DE112007001952T5 - Fan drive system - Google Patents

Abstract

Blower drive system characterized by:
a load pressure-sensitive variable displacement pump;
a work machine circuit and a flow control valve to which a discharge flow rate of the variable displacement pump is supplied;
a load pressure cutoff valve controlled by a maximum load pressure in the work machine circuit;
a cooling fan driving hydraulic motor;
a first discharge oil line connecting the variable displacement pump and the working machine circuit;
a second discharge oil passage branched from the first discharge oil passage and communicating with the flow control valve;
a feed oil passage connecting the flow control valve and the hydraulic motor;
a first precursor oil line taking the maximum load pressure in the work machine circuit;
a second precursor oil line that extracts a load pressure driving the hydraulic motor; and
a shuttle valve that selects high pressure side load pressure between the maximum load pressure in the first stage oil line and the load pressure in the second stage oil line;
a pump displacement of the variable displacement pump is controlled according to a differential pressure between the high pressure side load pressure selected by the shuttle valve and a pump pressure of the variable displacement pump, ...

Description

Technical area

The The present invention relates to a fan drive system, the one in a forklift, a skid loader (skid steer loader, SSL) and a crawler dump loader, the work machines are, installed engine cooling fan drives.

Background Art

In a conventional work machine whose engine is under Use of a water cooling device cooled. That is, the engine is cooled by a coolant by a water jacket provided on a machine body circulated. The coolant heated in the water jacket becomes led to a radiator and cooled, and that cooled coolant becomes the water jacket again fed.

One Cooling fan is placed in front of a radiator, and a coolant flowing through the radiator is caused by the wind generated by the cooling fan cooled. In general, the cooling fan (the cooling fan) from a motor via a Belt driven. Thus, the number of revolutions of the cooling fan corresponds the number of revolutions of the engine.

If the cooling fan is driven directly by the engine, becomes an arrangement area for the cooling fan limited, and a level of design of the radiator and other devices is limited. Therefore, will a structure used in which instead of the direct drive through the Engine, a hydraulic pump is used as the drive source, and a hydraulic motor of the cooling fan is replaced by a Delivery flow rate driven by a hydraulic pump.

If the hydraulic pump is used for the cooling fan becomes, the degree of freedom of design increases for the hydraulic motor, the cooling fan, the radiator and other devices. However, because the hydraulic pump arranged for the cooling fan as a new part must be, is the number of hydraulic pumps as a whole elevated.

Around To arrange the hydraulic pump as a new part, the design structure complex, and a larger installation space is required. Next, there is a problem in the cost increase and increased Number of parts.

Around To solve this problem is a fan drive system has been proposed in which a variable displacement pump, the oil an actuator, also as a hydraulic pump for the cooling fan driving Hydraulic motor is used.

Regarding the blower drive system, in which the variable displacement also As the hydraulic pump is used, one is in patent 1 described drive device has been proposed. Patent 1 discloses a cooling fan device in which the variable displacement pump is also used as the hydraulic pump, and the hydraulic pump hydraulically drives the cooling fan. The drive device described in Patent Document 1 is for a work machine such as a backhoe, in which the working machine frequently during his ride is used, and a large variable displacement pump is used so that oil is simultaneous to both the driving device as well as the working machine can be supplied.

It are various types of implements, such as one Implement that uses the work machine frequently and a working device, mainly for locomotion is used and in which the working machine only for a short while while driving. Examples such devices, mainly for driving used are a forklift, a skid steer loader and a Raupenkipplader.

The The present invention relates to a fan drive system for a work tool such as the forklift, but a cooling fan device as in patent 1 is not for the work tool like designed for the forklift. In the described in Patent Document 1 Cooling fan device, a structure is disclosed in which a discharge flow rate from a hydraulic pump Actuator and a cooling fan driving hydraulic motor is supplied. From here on becomes a drive device of Patent Document 1 as a conventional example 1 of present invention explained.

9 is a hydraulic circuit diagram of the drive device of patent document 1. As in 9 is shown is a main hydraulic pump 92 designed as a variable displacement pump by a motor 91 is driven. A discharge flow rate from the main hydraulic pump 92 becomes a working machine hydraulic cylinder 94 via an actuation valve 93 fed. Part of the from the main hydraulic pump 92 incoming discharge flow rate is the hydraulic motor 95 via a flow control valve 108 fed. The hydraulic motor 95 drives a cooling fan 96 at.

The main hydraulic pump 92 is designed as a hydraulic pump of the load pressure-sensitive type. The main hydraulic pump 92 has a frenzy disc 102 on, and an angle of the swash plate 102 becomes under a load pressure in the hydraulic cylinder according to a high-pressure side load pressure 94 and a load pressure in the hydraulic motor 95 controlled. The load pressure in the hydraulic cylinder 94 is via a load-sensitive line 99 (hereinafter, LS oil passage), and the high-pressure side load pressure under the load pressure in the hydraulic motor 95 and the load pressure in the hydraulic cylinder 94 becomes the load-sensitive valve 101 via a check valve 100 fed.

To a flow rate of the hydraulic motor 95 To supplement the supplied oil, is a hydraulic constant pump 104 from a drain valve 106 and a relief valve 107 via a check valve 105 controlled.

When a pump pressure of the hydraulic constant pump 104 becomes excessively high, the drain valve becomes 106 operated on an opening position side, and a discharge flow rate from the hydraulic constant pump 104 is via the drain valve 106 in a tank 97 issued. When the pump pressure of the main hydraulic pump 92 becomes big, becomes the relief valve 107 switched to an open position. Thus, the discharge flow rate from the hydraulic constant pump 104 via the relief valve 107 in the tank 97 issued.

A detected by a temperature sensor temperature of the working oil in the tank 97 and that of a fan speed sensor 103 detected number of revolutions of the fan become a control 98 entered. An opening area of the flow control valve 108 is controlled using these input detection signals. When the flow control valve 108 is controlled and the supply flow rate to the hydraulic motor 95 is controlled, a recording torque (absorption torque) of the hydraulic motor 35 be controlled to a specified pickup torque.

• Patentschrift 1: Japanische Patentoffenlegungsveröffentlichung Nr. 2000-161060

Thus, in the drive device for the cooling fan described in Patent Document 1, a change in the number of revolutions of the cooling fan 96 be suppressed, even if a pickup torque of the hydraulic motor 95 is varied, and the rotation of the cooling fan 96 can be stabilized. When the load of the hydraulic motor 95 is varied, may be a change in the number of revolutions of the cooling fan 96 be suppressed, and the rotation of the cooling fan 96 can be stabilized.

• Patent document 1: Japanese Patent Laid-Open Publication No. 2000-161060

Disclosure of the invention

To be solved by the invention problem

The cooling fan driving apparatus described in Patent Literature 1 is suitable for a working apparatus which frequently uses the working machine while driving, such as a backhoe. Therefore, a large variable displacement pump becomes the main hydraulic pump 92 used so that oil simultaneously to all facilities such as the driving device, the working machine and the hydraulic motor 95 for the cooling fan 96 can be supplied. The hydraulic constant pump 104 is provided so that the flow rate can be supplemented when a flow rate of the hydraulic motor 95 who has the cooling fan 96 turns, supplied oil is reduced.

The Inventors of the present invention have come to the idea, that in the case of a working device such as a Forklift, a skid steer loader (SSL) and a caterpillar dump truck, the mainly used for driving and their working machine used only for a short time, the use a large variable displacement pump in terms of maximum delivery flow rate, which can be dispensed by a hydraulic pump, unnecessary is different from that described in Patent Document 1 Device.

• (1) Zunächst wird hinsichtlich eines Lastdrucks, der die Pumpenverdrängung der Hydraulikpumpe steuert, ein Lastdruck der Arbeitsmaschine und ein Lastdruck des den Kühlventilator antreibenden Hydraulikmotors voneinander getrennt, und die Pumpenverdrängung der Hydraulikpumpe wird unter Verwendung von einem dieser Lastdrücke gemäß bestimmen Bedingungen gesteuert.
• (2) Wenn die Arbeitsmaschine betätigt wird, wird die Priorität auf den Lastdruck der Arbeitsmaschine gelegt, und die Pumpenverdrängung der Hydraulikpumpe wird gemäß dem Lastdruck der Arbeitsmaschine gesteuert, auf welchen die Priorität gelegt wurde. (3) Wenn die Arbeitsmaschine während der Fahrt des Arbeitsgeräts verwendet wird, kann dem Hydraulikmotor, der den Kühlventilator antreibt, keine ausreichende Flußrate zugeführt werden, aber die Zeit, während der die Arbeitsmaschine bei laufender Fahrt betätigt wird, ist kurz. Daher kann der Temperaturanstieg in dem Abstrahler auf ein niedriges Niveau unterdrückt werden, selbst wenn die dem Abstrahler zugeführte Windmenge zeitweilig vermindert ist.
• (4) Wenn die Arbeitsmaschine nicht betätigt wird, wird die Pumpenverdrängung der Hydraulikpumpe gemäß dem Lastdruck des Hydraulikmotors gesteuert, der den Kühlventilator antreibt. Damit kann die erhöhte Temperatur bei Normaldrehung des Kühlventilators verringert werden, selbst wenn die Temperatur in dem Abstrahler zeitweilig erhöht wurde. (5) Als die maximale Pumpenverdrängung der Hydraulikpumpe wird die für die maximal erforderliche Flußrate zur Betätigung der Arbeitsmaschine geeignete Pumpen verdrängung verwendet, selbst wenn die Zeit, während der die Arbeitsmaschine verwendet wird, kurz ist. Damit kann die Betätigung der Arbeitsmaschine stabilisiert werden. (6) Daher kann die (maximale) Pumpenverdrängung der Hydraulikpumpe verringert werden.

As a result of intensive research, the inventors have found that it is only necessary for the hydraulic pump to have a pump displacement designed to ensure a discharge flow rate supplied to the work machine which most needs the flow rate. In order to provide a blower drive system which adjusts a pump displacement of a hydraulic pump according to a maximum flow rate required for the operation of the work machine and which can use a small variable displacement pump with a low pump displacement, the inventors have provided the following solution.

• (1) First, regarding a load pressure that controls the pump displacement of the hydraulic pump, a load pressure of the work machine and a load pressure of the hydraulic motor driving the cooling fan are separated, and the pump displacement of the hydraulic pump is controlled using one of these load pressures according to determined conditions.
• (2) When the work machine is operated, priority is given to the load pressure of the work machine, and the pump displacement of the hydraulic pump is controlled according to the load pressure of the work machine on which the priority is given. (3) When the work machine is used while the implement is running, the hydraulic motor that drives the cooling fan can not be supplied with an adequate flow rate but the time during which the work machine is operated while the vehicle is running is short. Therefore, the temperature rise in the radiator can be suppressed to a low level even if the amount of wind supplied to the radiator is temporarily decreased.
• (4) When the work machine is not operated, the pump displacement of the hydraulic pump is controlled in accordance with the load pressure of the hydraulic motor that drives the cooling fan. Thus, the elevated temperature at normal rotation of the cooling fan can be reduced even if the temperature in the radiator has been temporarily increased. (5) As the maximum pump displacement of the hydraulic pump suitable for the maximum flow rate required for operating the working machine pump displacement is used, even if the time during which the working machine is used, is short. Thus, the operation of the working machine can be stabilized. (6) Therefore, the (maximum) pump displacement of the hydraulic pump can be reduced.

Means of solving the problem

The The aim of the present invention can be achieved by that in the claims 1 to 5 described aspects of the invention are solved.

That is, a first aspect of the present invention provides a blower drive system characterized by: a load pressure-sensitive variable displacement pump; a work machine circuit and a flow control valve to which a discharge flow rate of the variable displacement pump is supplied; a load pressure cutoff valve controlled by a maximum load pressure in the work machine circuit; a cooling fan driving hydraulic motor; a first discharge oil line connecting the variable displacement pump and the working machine circuit; a second discharge oil passage branched from the first discharge oil passage and communicating with the flow control valve; a feed oil passage connecting the flow control valve and the hydraulic motor; a first precursor oil line taking the maximum load pressure in the work machine circuit; a second precursor oil line that extracts a load pressure driving the hydraulic motor; and a shuttle valve that selects a high-pressure-side load pressure from the maximum load pressure in the first stage oil line and the load pressure in the second stage oil line
a pump displacement of the variable displacement pump is controlled according to a differential pressure between the high pressure side load pressure selected by the shuttle valve and a pump pressure of the variable displacement pump, the load pressure isolation valve is disposed in the second precursor oil line, the load pressure isolation valve according to a differential pressure between a pressurizing force of the first stage oil passage removed maximum load pressure and a force acting on the load pressure release valve biasing force of a spring is controlled,
when the pressing force of the maximum load pressure is greater than the biasing force of the spring, the load pressure separating valve is switched from a position in which the second precursor oil passage is communicated with the shuttle valve to a position where the second precursor oil passage is in Connected to a tank and the shuttle valve is pressurized to a tank, and
when the pressing force of the maximum load pressure is less than the biasing force of the spring, the load pressure separating valve is switched from the position in which the second precursor oil line is brought into communication with the tank in a position in which the second precursor oil line in Communication is brought with the shuttle valve, and the shuttle valve is acted upon by the hydraulic motor driving load pressure.

According to a blower drive system of a second aspect of the invention of the present application, in the structure of the above-described first aspect of the invention, throttling is arranged in the second precursor oil passage, instead of disposing the load pressure isolation valve in the second precursor oil passage, the second precursor oil passage is downstream branches the throttling in two oil lines, wherein one of the branched oil lines is connected to the shuttle valve, the load pressure separating valve is disposed at an intermediate portion of the other oil passage, and the other oil passage is connected to a tank,
the load pressure release valve is controlled according to a differential pressure between a pressure force from the maximum load pressure taken by the first precursor oil passage and a biasing force of a spring acting on the load pressure isolation valve when the pressure force from the maximum load pressure is greater than the biasing force of the spring, the load pressure isolation valve in one Position is switched, in which the second precursor oil line is brought into communication with a tank and the shuttle valve is pressurized to a tank pressure, and
when the pressing force of the maximum load pressure is less than the biasing force of the spring, the load pressure separating valve is switched from the position in which the second precursor oil passage is brought into communication with the tank to a position in which the communication is cut off, and the shuttle valve is acted upon by the hydraulic motor driving load pressure.

A third aspect of the present invention provides a blower drive system characterized by: a load pressure sensitive variable displacement pump; a steering circuit, a work machine circuit, and a flow control valve to which a discharge flow rate is supplied from the variable displacement pump; a priority valve which preferably supplies the discharge flow rate from the variable displacement pump to the steering circuit in which the steering circuit is used as a circle preferable to the work machine circuit; a load pressure relief valve controlled by a maximum load pressure in the work machine circuit; a hydraulic motor that drives a cooling fan;
a third discharge oil passage connecting the variable displacement pump and the priority valve; a fourth delivery oil passage connecting the priority valve and the steering circuit; a fifth discharge oil passage connecting the priority valve and the work machine circuit; a sixth discharge oil passage branched from the third discharge oil passage and connected to the flow control valve; a supply oil passage connecting the flow control valve and the hydraulic motor;
a first precursor oil line taking the maximum load pressure in the work machine circuit; a second precursor oil line that takes a load pressure to drive the hydraulic motor; a third precursor oil line taking a load pressure in the steering circuit;
a first shuttle valve that selects a high-pressure side load pressure from the maximum load pressure in the first stage oil line and the load pressure in the third stage oil line; and a second shuttle valve that selects a high-pressure-side load pressure from the high-pressure-side load pressure selected by the first shuttle valve and the load pressure in the second pilot-stage oil passage
a pump displacement of the variable displacement pump is controlled according to a differential pressure between the high pressure side load pressure selected by the shuttle valve and a pump pressure of the variable displacement pump, the load pressure isolation valve is disposed in the second precursor oil line, the load pressure isolation valve according to a differential pressure between a pressurizing force of the first stage oil passage removed maximum load pressure and a force acting on the load pressure release valve biasing force of a spring is controlled,
when the pressing force of the maximum load pressure is greater than the biasing force of the spring, the load pressure separating valve is switched from a position in which the second precursor oil passage is communicated with the shuttle valve to a position where the second precursor oil passage is in Connected to a tank and the shuttle valve is pressurized, and when the pressure force of the maximum load pressure is less than the biasing force of the spring, the load pressure relief valve from the position in which the second precursor oil line brought into communication with the tank is switched to a position in which the second precursor oil line is brought into communication with the shuttle valve, and the shuttle valve is acted upon by the hydraulic motor driving the load pressure.

According to a blower driving system of a fourth aspect of the present application, in the above-described structure of the third aspect, throttling is disposed in the second precursor oil passage, instead of disposing the load pressure cutoff valve in the second precursor oil passage and the second precursor oil passage branched downstream of the throttling in two oil lines, wherein one of the branched oil lines is connected to the shuttle valve, the load pressure release valve is disposed at an intermediate portion of the other oil passage, and the other oil passage is connected to a tank,
the load pressure relief valve is controlled according to a differential pressure between a pressing force of the maximum load pressure extracted by the first precursor oil passage and a biasing force of a spring acting on the load pressure separating valve;
when the pressing force of the maximum load pressure is greater than the biasing force of the spring, the load pressure release valve is switched to a position in which the second precursor oil passage is communicated with a tank and the shuttle valve is pressurized with a tank pressure, and
when the pressing force of the maximum load pressure is less than the biasing force of the spring, the load pressure separating valve is switched from the position in which the second precursor oil passage is brought into communication with the tank to a position in which the communication is cut off, and the shuttle valve is acted upon by the hydraulic motor driving load pressure.

According to one Blower drive system of a fifth aspect The present invention will provide a control structure of the flow control valve specified in the first four aspects of the invention.

Effect of the invention

If a load pressure of the working machine in a working machine circuit is generated, the displacement of the variable under Use of the maximum load pressure under the load pressures of the Arbeitsmaschinenkreises be controlled. It is possible to continue to prevent the load pressure, which is the pump displacement controls the variable displacement, during operation of the working machine varies, and the work machine can be in a stable state operate.

Further, when not used for the operation of the working machine discharge flow rate Ver a laxative consumption of the discharge flow rate can be prevented. Since the (maximum) displacement of the hydraulic pump amount required for the operation of the working machine, the (maximum) displacement of the hydraulic pump can be reduced.

Brief description of the figures

1 is a simplified circuit diagram for a hydraulic circuit (first embodiment);

2 Fig. 10 is a circuit diagram of a hydraulic circuit (first embodiment);

3 is a simplified circuit diagram of a hydraulic circuit (second embodiment);

4 is a circuit diagram of a hydraulic circuit (second embodiment);

5 Fig. 12 is a circuit diagram of a hydraulic circuit in which a priority valve is not used (third embodiment);

6 Fig. 15 is a circuit diagram for a hydraulic circuit using the priority valve (third embodiment);

7 Fig. 12 is a circuit diagram for a hydraulic circuit (fourth embodiment);

8th is a circuit diagram for a hydraulic circuit (fifth embodiment); and

9 shows a hydraulic circuit (Conventional Example 1).

Best way to execute the invention

preferred Embodiments of the present invention will be described below described in more detail based on the accompanying drawings. A construction of a blower drive system for a Forklift according to the invention is not limited to one Hydraulic circuit structure with a blower drive system explained below restricted, and other hydraulic circuit structures can be used if only meets the technical idea of the invention becomes.

First embodiment

A hydraulic circuit with a blower drive system according to the first embodiment of the present invention is described using 1 and 2 explained. 1 is a simplified circuit diagram of a hydraulic circuit and 2 is a detailed circuit diagram of a hydraulic circuit. First, the hydraulic circuit with the blower drive system according to the first embodiment of the invention will be briefly using 1 explains, and then the hydraulic circuit with the fan drive system according to the first embodiment of the invention using 2 explained. Reference numerals for common parts in the 1 and 2 are explained using the same reference numerals of the parts.

As in 1 is shown, a discharge flow rate of a load pressure-sensitive variable displacement pump 1 driven by a motor (not shown) into a discharge oil line 51 delivered as a first delivery oil line. The delivery oil line 51 branches into an oil line 57 as a second discharge oil line. The delivery oil line 51 is with a work machine circle 33 connected. The oil line 57 is with a flow control valve 37 connected. One of the flow control valve 37 controlled by the variable displacement pump 1 delivered flow rate is supplied as an operating flow rate, which via an oil line 58 as feed oil line a hydraulic motor 35 drives.

The of the variable displacement pump 1 discharged flow rate is from the displacement control device 2 controlled. The pump displacement of the variable displacement pump 1 is by operation of the displacement control device 2 controlled. The displacement control device 2 may vary according to a differential pressure between a pump pressure in the discharge oil line 51 and a high-pressure-side load pressure to be actuated by the maximum load pressure of Arbeitserkaschinkreis 33 and a load pressure in the hydraulic motor 35 given is.

The maximum load pressure in the work machine circuit 33 is via a precursor oil line 77 taken as the first precursor oil line. The precursor oil line 77 branches into a precursor oil line 78 connected to one side of a shuttle valve 29 connected, and a precursor oil line 79 that with the valve 45 connected to the load pressure separation.

The load pressure of the hydraulic motor 35 is via a precursor oil line 83 taken as a second precursor oil line. A valve 45 for load pressure separation is in the precursor oil line 83 arranged. The precursor oil line 83 is between a connection with the precursor oil line 80 connected to the other side of the shuttle valve 29 connected, and a connection to a tank 50 switched, from the valve 45 for load pressure separation.

The over the precursor oil line 77 removed maximum load pressure in the work machine circuit 33 is via the precursor oil line 79 to the valve 45 for load pressure separation, and a spring force of a spring is applied to an end face of the Ar driven machine 33 (of the valve 45 ) opposed to an end face to which the maximum load pressure is applied. When the load pressure in the work machine circuit 33 is generated, the valve 45 connected to the load pressure separation against the spring force of the spring, the precursor oil line 83 will with the tank 50 connected, and the load pressure in the precursor oil line 80 is set to a tank pressure. When the load pressure in the work machine circuit 33 is not generated, the valve 45 Switched to the load pressure separation by the spring force of the spring, the precursor oil line 83 is with the precursor oil line 80 connected, and the load pressure of the hydraulic motor 35 becomes for the load pressure of the precursor oil line 80 established.

When a plurality of work machines in the work machine circuit 33 are arranged, and there are a plurality of load pressures in the Arbeitsmachaschinkreis 33 gives, is about the precursor oil line 77 taken from the existing plurality of load pressures, the highest load pressure. Even if a plurality of work machines in the work machine circuit 33 are provided, when a load pressure in a work machine in the work machine circuit 33 occurs, this load pressure through the precursor oil line 77 taken.

The of the shuttle valve 29 extracted high pressure side load pressure is through the precursor oil line 85 to the displacement control device 2 guided. A pump pressure in the delivery oil line 51 becomes the displacement control device 2 led, the displacement control device 2 will be in line with a differential pressure between the pump pressure and that of the shuttle valve 29 removed high pressure side load pressure actuated, and the pump displacement of the variable 1 is controlled.

An opening area of the flow control valve 37 is from a thermo module 38 and is shifted according to a temperature of a coolant cooled by a radiator (not shown). A structure of the thermomodule 38 will be referring to later 2 explained.

In this construction, when the load pressure in the work machine circuit 33 is not generated, the pump displacement of the variable 1 in accordance with the load pressure of the hydraulic motor 35 to be controlled. When the load pressure in the work machine circuit 33 is generated, the pump displacement of the variable displacement pump 1 consistent with the maximum load pressure of the work machine circuit 33 to be controlled.

Next, the hydraulic circuit with the blower drive system according to the first embodiment will be described in detail using FIG 2 explained. Reference numerals of common parts in the 1 and 2 are explained using the same reference numerals of the parts. As in 2 is shown, a discharge flow rate from the load pressure-sensitive variable displacement pump 1 , which is driven by a motor M, the discharge oil line 51 fed.

The delivery oil line 51 is via a check valve 48 with a pump opening 24E a first-direction switching valve 8th connected, and is also via a check valve 49 with a pump opening 25D a second direction switching valve 17 connected.

A directional control valve 8th is with bottom sides of a pair of lifting cylinders 13A and 13B over an oil line 54 connected. A precursor check valve 12 is in the oil line 54 arranged, and the precursor check valve 12 is controlled by a directional control valve electromagnetic circuit. From the head sides of the pair of lift cylinders 13A and 13B returning oil is via a drain oil line 69 in a tank 50 discharged, and from the bottom sides of the pair of lifting cylinders 13A and 13B returning oil is through the oil line 54 delivered and controlled.

A directional changeover valve 17 is with a pair of pitch cylinders 20A and 20B through oil pipes 55 and 56 connected.

The load pressures at the bottom sides of the pair of lift cylinders 13A and 13B be through a precursor oil line 74 taken, and become one end side of a shuttle valve 27 guided. Load pressures in the pair of pitch cylinders 20A and 20B be through a precursor oil line 76 taken from the other side of the shuttle valve 27 fed.

One of the shuttle valve 27 selected high-pressure side load pressure is through the precursor oil line 77 taken, and is via the precursor oil line 78 one end side of the shuttle valve 29 fed, and is via the precursor oil line 79 the valve 45 supplied for load pressure separation.

The first direction switching valve 8th can by operating an operating lever 9 is switched and is considered a switching valve with seven openings 24A to 24G educated. The first direction switching valve 8th has a subdivided into two sub-units (coils), ie in a first sub-structure 8A and a second substructure 8B subdivided substructure (spool structure). By pressing the operating lever 9 can be the first substructure 8A be switched from a position VII to a position IX. The second substructure 8B follows the movement of the first substructure 8A by a clamping force of the spring 10a and can be moved from position IV to position VI. The feather 10b is formed as a neutral spring, which is the first-direction switching valve 8th returns to neutral positions V and VIII.

The openings 24C and 24D escort the oil pipeline 54 through a check valve 12 and are with bottom sides of the lifting cylinder 13A and 13B connected. The opening 24A is formed as an opening, which is a load pressure at the bottom sides of the lifting cylinder 13A and 13B which move a fork (not shown) up and down. The opening 24A leads the load pressure to the bottom sides of the lifting cylinders 13A and 13B via the precursor oil line 54 the shuttle valve 27 to. The opening 24B is with an oil pressure chamber of the precursor check valve 12 through the electromagnetic switching valve 15 connected.

The pump opening 24E is formed as an opening having a discharge flow rate of the variable displacement pump 1 that an oil line 52 passed through the check valve 48 is supplied. The tank openings 24F and 24G are formed as openings through which of the bottom sides of the lifting cylinder 13A and 13B delivered flow rates via a drain oil line into the tank 50 be delivered. A throttling 86 is in the drain oil line 63 arranged, and a pressure above the throttling 86 becomes the second substructure 8B applied as a precursor print. The second substructure 8B becomes independent of the first substructure 8A according to a differential pressure between the pressure upstream of the restriction 86 and the tank pressure controlled.

The position VIII of the first-direction switching valve 8th is a neutral position of the first-direction switching valve 8th , and when the first-direction switching valve 8th is in the neutral position, is the second substructure 8B switched to the position V, which represents a neutral position. When the first-direction switching valve 8th by actuating the operating lever 9 can be switched to position IX, oil from the oil line 52 from the opening 24C over the check valve 12 arrive and can the bottom sides of the lifting cylinder 13A and 13B over the oil line 54 be supplied. At this time is the second substructure 8B by a pressing force from the first-direction switching valve 8th switched to position VI.

In this way, a fork (not shown) can be moved upwards. Because the second substructure 8B at that time in from the actuation of the first substructure 8A is in the position VI, is the opening 24D foreclosed. Oil at the top of the lift cylinders 13A and 13B is via the drain oil line 69 in the tank 50 issued.

When the first-direction switching valve 8th by the operation of the operating lever 9 is switched to the position VII, the oil from the oil line 52 blocked off, and the oil supply to the bottom sides of the lifting cylinder 13A and 13B will be cut off. At this time, when the electromagnetic switching valve 15 is controlled and the precursor oil line 75 is brought into communication, from bottom sides of the cylinder 13A and 13B discharged oil from the opening 24C through the tank opening 24F and can pass through the drain oil line 63 in the tank 50 be delivered.

At this time follows the second subunit 8B the circuit of the first-direction switching valve 8th in the position VII, due to the biasing force of the spring 10a , and is switched to position IV. At the same time, the lifting cylinders reach the bottom side 13A and 13B discharged oil from the opening 24D through the tank opening 24G and can via the drain oil line 63 in the tank 50 be delivered. Thus, the fork (not shown) can be moved down.

At this time, the second subunit becomes 8B in accordance with a differential pressure between the tank pressure and a pressure in the drain oil line 63 above the throttling 86 switched to position V. That is, the flow rate of the opening 24D discharged oil is in accordance with the on the second subunit 8B applied pressure difference between the tank pressure and the pressure in the drain oil line 63 upstream of the throttling 86 controlled.

The total discharge flow rate of the returning, from the bottom sides of the lifting cylinder 13A and 13B delivered oil is a summed flow rate of the discharge flow rate from the second subunit 8B and the discharge flow rate from the first subunit 8A ,

This allows the first subunit 8A with flow rate control characteristics with respect to the opening 24D be provided, and the downward movement speed of the lifting cylinder 13A and 136 can via the first-direction switching valve 8th to be controlled.

2 shows an example in which the first-direction switching valve 8th a flow rate control valve function for controlling the downward movement speeds of the lift cylinders 13A and 13B has, but the flow control valve can in the oil line 54 be arranged. By the flow control valve in the oil line 54 is arranged, it becomes possible to prevent an excessive increase in the downward movement speed of the fork when the fork is moved down in a state in which the load pressures of the lifting cylinder 13A and 13B are big.

The over the oil line 54 with the bottom sides of the lifting cylinder 13A and 13B connected check valve 12 is through the electromagnetic switching valve 15 controlled. The electromagnetic switching valve 15 acts as a safety device, and when a driver sits on a driver's seat, acts in the electromagnetic switching valve 15 provided solenoid and the electromagnetic switching valve 15 can be switched to the connection position. When the driver sits in the driver's seat, the solenoid does not work and the electromagnetic switching valve 15 is connected by a clamping force of a spring in the Abschottstellung.

When the directional control valve 8th in the switching position (IV), (VII) and the electromagnetic switching valve 15 is in the Abschottstellung, opens the precursor check valve 12 not even if a trial is started, the lift cylinder 13A and 13B lower as the pressure on the precursor check valve 12 to the side of the lifting cylinder 13A and 13B ie the pressure in the pre-stage oil line 75 is not reduced.

Thus, that of the lifting cylinders 13A and 13B returning oil to the precursor check valve 12 stopped.

When the directional control valve 8th in the switching position (IV), (VII) and the electromagnetic switching valve 15 is in the connecting position, the pressure in the precursor oil line is sufficient 75 from the opening 24B through the tank opening 24F and becomes equal to one with the tank 50 communicating pressure. This allows the precursor check valve 12 be in the connection state. That is, that of the bottom sides of the lifting cylinder 13A and 136 returning oil is delivered via the precursor envelope valve 12 to the actuator openings 24C and 24D brought.

A lowering safety valve 14 is between the lift cylinder 13A and the lift cylinder 13B arranged. The function of the lowering safety valve 14 lies therein, an abrupt pressure loss at the bottom side of the lift cylinder 13A even then prevent if the oil line 54 or similar is damaged. This makes it possible to make an abrupt downward movement of the fork due to damage to the oil line 54 to prevent.

The second direction switching valve 17 can by operating an operating lever 18 be switched between three positions and is as a switching valve with five openings 25A to 25E educated. One on the second directional changeover valve 17 force-acting spring 17a is formed as a neutral spring, which is the second-direction switching valve 17 returns to the neutral position XI.

The opening 25A is over an oil line 56 with the head sides of the tilt cylinder 20A and 20B connected, and the opening 25C is over an oil line 55 with the bottom sides of the tilt cylinder 20A and 20B connected.

The opening 256 is as an opening for detecting the on the tilt cylinder 20A and 20B designed load acting, and is via a precursor oil line 76 with the shuttle valve 27 connected. The pump opening 25D is formed as an opening, to which through the oil line 52 reached discharge flow rate of the variable displacement pump 1 over the check valve 59 is supplied. The tank opening 25E is formed as an opening through which of the tilt cylinders 20A and 20B discharged oil via a drain oil line 64 to the tank 50 is delivered.

The second direction switching valve 17 is equipped with a mechanism that prevents oil on the head sides of the tilt cylinder 20A and 20B flows into the tank even when the subunit is operated and is switched to the position XII when the engine is stopped, that is, when no oil passes through the oil pipe 52 flows.

The supply of tilt cylinders 20A and 20B with oil can by feeding from the oil line 52 to the tilt cylinders 20A and 20b supplied oil through the opening 25A or 25C from the pump opening 25D in the second direction switching valve 17 to be controlled. From the pitch cylinders 20A and 20B discharged oil can from the drain oil line 64 through the oil line 55 or the oil line 56 be returned.

That of the variable displacement pump 1 to the delivery oil line 51 discharged oil passes through the from the delivery oil line 51 branched oil line 57 and becomes the hydraulic motor 35 fed, which is a cooling fan 36 drives. This is the flow rate of the hydraulic motor 35 supplied oil controlling flow control valve 37 is in the oil line 57 arranged. To prevent the pressure in the oil line 57 exceeds a predetermined value is a drain valve 44 in one of the oil line 57 branching discharge oil line 68 arranged.

An opening area of the flow control valve 37 is due to a pressure difference between the relative to the flow control valve 37 upstream and downstream pressure and spring force of a spring 37a controlled. The spring force of the spring 37a is through the thermo module 38 set in accordance with the temperature of the cooled by a radiator (not shown) coolant.

If the coolant temperature is high, the thermo module will work 38 such that the spring cap of the spring 37a is increased, and when the coolant temperature is low, the thermal module acts 38 such that the spring force of the spring 37a is reduced. Therefore, when the coolant temperature is high, the opening area of the flow control valve becomes 37 increases and the flow rate of the hydraulic motor 35 supplied oil can be increased. This allows the cooling fan (the cooling fan) 36 can be rotated at a high speed, the amount of air supplied to the radiator can be increased and the coolant temperature can be reduced.

If the coolant temperature is low, the thermal module will work 38 such that the spring force of the spring 37a is weakened, the opening area of the flow control valve 37 is reduced and the flow rate of the hydraulic motor 35 supplied oil is reduced. This turns the cooling fan (cooling fan) 36 braked, the amount of air supplied to the radiator is reduced and the coolant temperature can be increased.

A changeover valve 40 for normal / reverse rotation, which is the direction of rotation of the hydraulic motor 35 is between the flow control valve 37 and the hydraulic motor 35 arranged. By switching the changeover valve 40 for normal / reverse rotation it is possible to use the oil line 58 or the oil line 59 for connection to the hydraulic motor 35 and the selected oil line 58 or oil line 59 Oil from the oil line 57 supply. At this time, this is done by the hydraulic motor 35 discharged oil through the oil line 59 or the oil line 58 in the drain oil line 67 issued.

The circuit of the switching valve 40 for normal / reverse rotation is by the operation of a solenoid valve 41 controlled for normal / reverse rotation. The solenoid valve 41 for normal / reverse control selects between a tank pressure in one with the hydraulic motor 35 connected drain oil line 81 and one in the from the oil line 57 branched off oil line 60 prevailing pressure, and brings one of these pressures on the switching valve 40 for normal / reverse rotation on. The on the change-over valve 40 applied for normal / reverse rotation Pressure is applied to the tank pressure or the pressure in the oil line 60 set. This will be the switching valve 40 for normal / reverse rotation switched between a position in which the hydraulic motor 35 normally is rotated and a position in which the hydraulic motor 35 turns in reverse direction.

A downstream of the flow control valve 37 acting hydraulic pressure is via the precursor oil line 83 as one on the hydraulic motor 35 taken effective load pressure. The precursor oil line 83 is with the valve 45 connected to the load separation. The valve 45 for load separation is designed as a two-position and three-orifice valve. Regarding the on the valve 45 It is possible to use a spring with a force of 0.5 MPa for acting on the load pressure separation spring.

If a work machine than on the valve 45 It is possible to use a spring of such a strength that the valve is used for load pressure separation 45 is switched directly to the load pressure separation by the maximum load pressure of the working machine circuit. Using the spring of such strength, when the work machine is being used, the valve may be used 45 for load pressure separation immediately against a biasing force on the valve 45 to switch the load pressure separation acting spring.

This is the pump displacement of the variable 1 controlled during operation of the work machine by a load pressure of the operated work machine.

Therefore, it can be prevented that the pump displacement of the variable 1 controlling load pressure during operation of the work machine from a load pressure of the work machine to the load pressure of the hydraulic motor 35 changes and the operability of the working machine can be stabilized.

By switching the valve 45 for load pressure separation of the shuttle valve 29 via the precursor oil line 80 supplied load pressure on the load pressure of the hydraulic motor 35 or tank pressure. One of the valve 45 pressures selected for load pressure separation may be via the pre-stage oil line 80 the serving as load pressure selector shuttle valve 29 be supplied.

For controlling the switching of the valve 45 for load pressure separation is that of the shuttle valve 27 selected high-pressure side load pressure via the pre-stage oil line 77 taken and over from the precursor oil line 77 branched pre-stage oil line 79 the valve 45 supplied for load pressure separation. When the lifting cylinder 13A and 13B or the tilt cylinder 20A and 20B are actuated, acting on the Arbeitsmaschinenkreis maximum load pressure of the working machine via the precursor oil line 79 on the valve 45 applied for load pressure separation.

At this time is the valve 45 switched to the load pressure separation against the biasing force of the spring, the precursor oil line 83 is with the tank 50 connected, and the valve 45 For load pressure separation is switched to a position in which the load pressure in the precursor oil line is set to the tank pressure. When the load pressure of the work machine is not generated in the work machine circuit, the valve is 45 switched to load pressure separation in a position at which the shuttle valve 29 with the in the precursor oil line 83 prevailing load pressure is applied.

From the load pressure on the bottom sides of the lifting cylinder 13A and 13B and the load pressure in the tilt cylinders 20A and 20B the high pressure side of the load pressures through the shuttle valve 57 selected and to the precursor oil line 77 output. That means that of the shuttle valve 27 selected high-pressure side load pressure is applied as a load pressure of the work machine on the work machine circuit.

The of the shuttle valve 27 selected and via the precursor oil line 77 extracted high-pressure side load pressure is in the shuttle valve 29 through from the precursor oil line 77 branched off precursor oil line 78 fed. A drain valve 32 is in the precursor oil line 78 on the outlet side of the shuttle valve 27 arranged such that the of the shuttle valve 27 selected high-pressure side load pressure does not exceed a predetermined value. The drain valve 32 is with the tank 50 through a drain oil line 66 connected.

That is, that of the shuttle valve 27 selected high-pressure side load pressure will be the maximum load pressure of the work machine circuit, and the shuttle valve 29 is charged with it. In the shuttle valve 29 is determined by the maximum load pressure of the work machine circuit and that of the valve 45 load pressure selected for load pressure separation, a high pressure side of the load pressures of the precursor oil line 85 output. The one from the valve 45 load pressure selected for load pressure separation is the load pressure of the hydraulic motor 35 or the tank pressure. The of the shuttle valve 29 selected high-pressure side load pressure becomes the displacement control device 2 supplied, which is the displacement of the variable displacement pump 1 via the precursor oil line 85 controls.

The displacement control device 2 includes a switching valve 5 , which is formed as a three-position and three-opening switching valve, and a drive cylinder, the swash plate angle of a swash plate 1a the variable displacement pump 1 controls. The changeover valve 5 is in accordance with a differential pressure between that of the shuttle valve 29 selected high-pressure side load pressure and the pump pressure of the variable displacement pump 1 connected. The drive cylinder 6 , the swash plate angle of the swash plate 1a the variable displacement pump 1 controls, by a switching operation of the switching valve 5 be operated.

That is, when the of the shuttle valve 29 selected high-pressure side load pressure acting on the switching valve 5 applied spring pressure of the spring, and the pump pressure of the variable displacement pump 1 balanced, is the switching valve 5 in the in 2 shown neutral position, and the drive cylinder 6 retains the swash plate angle of the swash plate 1a in the current state.

Is a differential pressure between that of the shuttle valve 29 selected high pressure side load pressure and the pump pressure of the variable displacement pump 1 increases, the switching valve 5 to the in 2 switched to the left position, the pump displacement of the variable 1 is increased and the discharge flow rate from the variable displacement pump 1 will be raised. When the differential pressure between that of the shuttle valve 29 selected high-pressure side load pressure and the pump pressure from the variable displacement pump 1 becomes small, the switching valve 5 in the in 2 switched right position, the displacement of the variable 1 is reduced, and the discharge flow rate of the variable displacement pump 1 is reduced.

With this, the displacement control device becomes 2 according to a differential pressure between that of the shuttle valve 29 selected high-pressure side load pressure and the pump pressure in the oil line 51 operated, and the discharge flow rate of the variable displacement pump 1 is controlled in accordance with the differential pressure.

That is, the lift cylinders 13A and 13B or the tilt cylinder 20A and 20B are actuated, and when the load pressure in the lift cylinder 13A and 13B or tilt cylinders 20A and 20B is generated, the valve 45 switched to the load pressure separation by the load pressure in the sealed position. This will be the precursor oil line 80 in communication with the tank 50 brought, and the over the precursor oil line to the shuttle valve 29 applied pressure is the tank pressure.

When the load pressure of the work machine is generated in the work machine circuit, the load pressure of the cooling blower can 36 driving hydraulic motor 35 be treated as a forced tank pressure condition. Therefore, the maximum load in the work machine circuit and the tank pressure treated load pressure of the hydraulic motor 35 together in the shuttle valve 29 be compared.

This is the one of the variable displacement pump 1 delivered discharge amount based on the maximum load pressure of the work machine circuit ge controls. In other words, when the load crawler in the lift cylinders 13a and 13B or tilt cylinders 20A and 20B is generated, the discharge flow rate from the variable displacement pump 1 not from the load pressure of the hydraulic motor 35 controlled.

Even if the load pressure in the hydraulic motor 35 greater than the load pressure of the lifting cylinder 13A and 13B or the load pressure of the tilt cylinder 20A and 20B becomes the pump displacement of the variable displacement pump 1 not from the load pressure of the hydraulic motor 35 but is controlled based on the maximum load pressure of the work machine circuit when the load pressure is generated in the work machine circuit. Therefore, the work machine can be stably operated when the load pressure is generated in the work machine circuit.

When the load pressure of the work machine is generated in the work machine circuit, the pump displacement of the variable displacement pump 1 even when the fork is moved vertically in a non-load state during driving, it is controlled to become equal to the pump displacement in accordance with the maximum load pressure in the work machine circuit.

In this case, even if the load pressure of the cooling fan 36 driving hydraulic motor is larger than the maximum load pressure in the work machine circuit, the swash plate angle of the variable displacement pump is not according to the cooling fan 36 driving hydraulic motor 35 but is controlled according to the maximum load pressure in the work machine circuit. Thus, a suitable for the maximum load pressure in the Arbeitsmaschinenkreis flow rate of the variable displacement pump 1 delivered, and the working machine can be operated in a stable manner.

If the fork is moved vertically without load while driving, one will turn the cooling fan 36 and to obtain a sufficient amount of wind flow rate required by the cooling fan 36 driving hydraulic motor 35 not supplied. However, since the operation time during which the fork is vertically moved without load is short, it is possible to suppress a temperature rise in the radiator to a low level even if the amount of wind supplied to the radiator is temporarily decreased.

In addition, the pump displacement of the variable displacement pump 1 after the operating time during which the fork is moved vertically without load while driving is completed, according to the load pressure of the cooling fan 36 driving hydraulic motor 35 controlled.

Second embodiment

A hydraulic circuit with a blower drive system according to the second embodiment of the present invention is performed using the 3 and 4 explained. In addition to the hydraulic circuit of the first embodiment, a steering drive circuit is provided in the second embodiment. A maximum load pressure of the load pressures of a steering drive device 30 , the lifting cylinder 13A and 13B and the tilt cylinder 20A and 20B is considered a load pressure in the precursor oil line 78 used as a first precursor oil line leading to the shuttle valve 29 leads. With regard to this structure, the second embodiment is different from the first embodiment, but the other structure is the same as that of the first embodiment.

Therefore, the parts of the second embodiment that correspond to those of the first embodiment will be denoted by the same reference numerals and their explanation will be omitted, while mainly explaining a structure different from that of the first embodiment. The with the shuttle valve 29 connected precursor oil line 78 is the one with the precursor oil line 77 in the first embodiment, connected precursor oil passage, but the precursor oil passage 78 The second embodiment is designed as a pre-stage oil line, one of a shuttle valve 28 selected high-pressure side load pressure takes.

3 shows a simplified hydraulic circuit diagram of the second embodiment similar 1 , and 4 Fig. 12 is a detailed hydraulic circuit diagram of the second embodiment, similar 2 ,

As in 3 is shown, passes from a load pressure-sensitive variable displacement pump 1 driven by a motor (not shown) dispenses discharged oil through a discharge oil line 51 as a third delivery oil line, and becomes a load pressure sensitive priority valve 3 fed. From the priority valve 3 discharged oil is used as working oil that operates a work machine and the steering.

That is, that of the priority valve 3 discharged oil is through an oil line 53 as a fourth output oil line to a steering circuit 34 fed, and is through the oil line 52 as a fifth delivery oil line to the work machine circuit 33 fed.

Next passes oil that passes through the oil line 57 flows as a sixth discharge oil line, which from the discharge oil line 51 upstream of the priority valve 3 branched off, via the flow control erventil 37 through the oil line 58 as the supply oil line, and is used as working oil, which is the hydraulic motor 35 drives.

A discharge flow rate from the variable displacement pump 1 is from the displacement control device 2 controlled, and the operation of the displacement control device 2 may be in accordance with a differential pressure between the pump pressure and the highest load pressure below the maximum load pressure in the work machine circuit 33 , the maximum load pressure in the steering circuit 34 and the load pressure of the hydraulic motor 35 to be controlled.

The maximum load pressure in the work machine circuit 33 is via the precursor oil line 77 taken as a first precursor oil line, and the load pressure in the steering circuit 34 is via the precursor oil line 71 taken as a third precursor oil line. The precursor oil line 77 and the precursor oil line 71 are with the shuttle valve 28 connected, which selects the high pressure side load pressure. The high pressure side load pressure between the maximum load pressure in the work machine circuit 33 and the load pressure in the steering circuit 34 is through the shuttle valve 28 selected as the first shuttle valve, and is via the precursor oil line 78 taken.

The of the shuttle valve 28 Selected high-pressure side load pressure in the pre-stage oil line 78 becomes the shuttle valve 29 supplied as a second shuttle valve. The via the precursor oil line 77 extracted maximum load pressure of the working machine circuit 33 we the valve 45 for load pressure separation via the precursor oil line 79 fed.

The valve 45 for load pressure separation, according to a differential pressure between a load pressure in the precursor oil passage 79 and one on the valve 45 Controlled for load pressure separation spring force of a spring. That is, if one in the work machine circle 33 generated load pressure is generated, sets the valve 45 For load pressure separation, the load pressure in the precursor oil line 80 on the tank pressure, and when the load pressure in the work machine circuit 33 is not generated, sets the valve 45 For load pressure separation, the load pressure in the precursor oil line 80 on the load pressure of the hydraulic motor 35 ,

With this construction, the discharge displacement of the variable displacement pump 1 according to a differential pressure between that of the shuttle valve 29 selected load pressure in the precursor oil line 85 and the pump pressure in the discharge oil line 51 causes. Next, when the load pressure in the work machine circuit 33 is generated, the displacement of the variable displacement pump 1 according to a differential pressure between the pump pressure and the high-pressure side load pressure under the maximum load pressure of the work machine circuit 33 and the load pressure of the steering circuit 34 controlled.

Next, the hydraulic circuit with the cooling fan system will be described in detail using 4 explained. In 4 and the 1 to 3 the same components are provided with the same reference numerals. As in 4 is shown, a discharge flow rate of the driven by the motor M load pressure-sensitive variable displacement pump 1 over the oil line 51 the load pressure sensitive priority valve 3 fed. The priority valve 3 is formed as a three-position and three-opening switching valve.

A pump opening 23C of the priority valve 3 is with the variable pump 1 via the delivery oil line 51 connected. An opening 23A runs through the oil line 52 and is with an opening 24E of the first-direction switching valve 8th over the check valve 48 connected, and is with an opening 25D of the second direction switching valve 17 over the check valve 49 connected. The opening 23B is over the oil line 53 with the steering drive device 30 connected.

The steering drive device 30 can as a steering actuator actuator 31 Act. A discharge flow rate from the steering drive device 30 can via the drain oil line 65 in the tank 50 be delivered.

A position of the priority valve 3 is according to a differential pressure between a hydraulic pressure of the oil passage 53 , the oil to the steering drive device 30 supplies, and a load pressure in the actuator 31 connected via the pre-stage oil line 71 through the directional valve 4 is removed with electromagnetic switching.

The priority valve 3 can be switched between three positions, from a position I to a position III. In position III, a supply of the discharge flow rate from the variable displacement pump 1 to the oil line 52 which is a supply oil line to the lift cylinder 13A and 13B and the pitch cylinders 20A and 20B is, stopped, and a discharge flow rate from the variable displacement pump 1 can the oil line 53 supplied with a supply oil line to the aforementioned steering drive device 30 is.

In position II, the discharge flow rate of the variable displacement pump 1 the oil line 52 and the oil line 53 be supplied. In the position I, the discharge flow rate of the variable displacement pump 1 the oil line 52 are supplied, and the discharge flow rate of the variable displacement pump 1 can the oil line 53 be fed through a throttling.

An output pressure at the output from the priority valve 3 to the oil line 53 can be applied via the precursor oil line 72 be removed. The oil line 53 is above an oil line 62 and one in the oil line 62 arranged throttling in communication with the precursor oil line 72 ,

Part of the precursor oil line 72 merges with that of the precursor oil line 71 branched pre-stage oil line 73 and is at one end of the priority valve 3 connected via a throttle. Oil from the precursor oil line 72 and the precursor oil line 73 gives a first detection pressure and is combined with a biasing force of a spring 3a on the priority valve 3 applied. The first sensing pressure and the biasing force of the spring 3a be a first operating pressure and can be the priority valve 3 switch to position III. The other part of the precursor oil line 72 goes to the other end of the priority valve 3 led, where the spring 3a is not arranged, and serves as a second detection pressure, which is the priority valve 3 in the position 1 on.

The electromagnetic switching control valve 4 is in the precursor oil line 73 arranged, and if a solenoid 4a the electromagnetic switching control valve 4 operated or non-operated, the electromagnetic switching control valve 4 be switched between an open valve state and a closed valve state. In 4 is the solenoid 4a placed in the non-powered state and the electromagnetic switching control valve 4 closes the precursor oil line 73 ,

When the electromagnetic switching control valve 4 is opened, a pressure in the precursor oil line 73 equal to the load pressure in the precursor oil line 71 ,

A pressure in the precursor oil line 71 and the biasing force of the spring 3a act as a first operating pressure, which is the priority valve 3 switches to position III. When a differential pressure between the second operating pressure and the first operating pressure is a predetermined differential pressure for driving the Lenkbetätigungsaktuators 31 exceeds, the priority valve 3 switched from the position III in accordance with the differential pressure of the second operating pressure in the position II or the position I.

This can be one for driving the actuator 31 the steering drive device 30 required flow rate always to the oil line 53 be issued. From the delivery flow rate from the variable displacement pump 1 may be an excess with respect to driving the actuator 31 required flow rate the lifting cylinders 13A and 13B and / or tilt cylinders 20A and 20B from the oil line 52 be supplied.

When the electromagnetic control switching valve 4 is switched from this state to the closed valve state, ie, the foreclosed state between the precursor oil line 73 and the precursor oil line 71 , the first detection pressure and the second detection pressure become equal to the pilot pressure in the oil passage 53 , and these are equal to each other.

This will be the priority valve 3 by the biasing force of the spring 3a switched to position III, and the switched state in position III is maintained. Therefore, the priority valve stops 3 the oil supply to the lifting cylinders 13A and 13B and / or tilt cylinders 20A and 20B , That is, the priority valve 3 only supplies oil to the steering drive device 30 , which enjoys a higher priority, and a condition in which the priority valve 3 only with the oil line 53 is in communication is maintained.

The circuit of the electromagnetic switching control valve 4 can be controlled by a seat state confirmation switch arranged on a driver's seat. That is, when the seated state confirmation switch detects that a driver is sitting on the driver's seat, the solenoid becomes 4a the electromagnetic switching control valve 4 controlled, and the electromagnetic switching control valve 4 maintains the connection state.

So, because the priority valve 3 via the precursor oil line 73 is pressurized, it is possible, a load pressure of the steering drive device 30 in the precursor oil line 71 to use, and the priority valve 3 becomes in accordance with a differential pressure between the load pressure of the steering drive device 30 and the steering drive device 30 supplied pump pressure controlled.

When the seat condition confirmation switch detects that a driver has left the driver's seat, the solenoid becomes 4a the electromagnetic switching control valve 4 no longer energized, as in 4 shown, and the precursor oil lines 71 and 73 be separated. So that's the priority valve 3 via the precursor oil line 72 supplied pressures substantially equal to each other.

Therefore, the priority valve becomes 3 due to the biasing force of the spring 3a switched to position III, and this switching state in position III is maintained. At this time, the oil supply to the lift cylinders 13A and 13B and / or tilt cylinders 20A and 20B stopped, that is, in a state where the driver is moving away from the driver's seat, it is possible to detect a condition in which the working machine can not be operated.

A shift control valve 22 containing the precursor oil line 71 and the precursor oil line 73 is brought to the connection state, is not limited to the electromagnetic switching control valve, and other switching control valves can be used. The switching control valve may be brought into the communication state by an "ON" signal, or the switching control valve may be brought into the communication state by an "OFF" signal.

A control signal for controlling the electromagnetic switching control valve 4 is not limited to a signal from the seated state operation switch disposed on the driver's seat, and it is possible to use a detection signal from another detection switch as a control signal for the magnetic switching control valve, and the electromagnetic switching control valve 4 control using the other control signal.

The one from the precursor oil line 71 detected load pressure of the lifting cylinder 13A and 13B and that of the precursor oil line 76 detected load pressure of the tilt cylinder 20A and 20B be the shuttle valve 27 fed. The of the shuttle valve 27 Selected high-pressure side load pressure is via the pre-stage oil line 77 the shuttle valve 28 fed. The load pressure in the pre-stage oil line 77 becomes the load pressure isolation valve 45 as the maximum load pressure in the work machine circuit 33 supplied (see 1 ).

The one from the precursor oil line 71 detected load pressure of the steering drive device 30 becomes the shuttle valve 28 fed. A high pressure side load pressure between the maximum load pressure in the work machine circuit and the load pressure in the steering drive device 30 is from the shuttle valve 28 selected and the precursor oil line 78 pitched. The precursor oil line 78 is with the shuttle valve 29 connected. The shuttle valve 29 pressurizes the precursor oil line 85 with the larger pressure from the high pressure side, from the shuttle valve 28 selected load pressure and the load pressure in the precursor oil line 80 ,

Like the load pressure in the pre-stage oil line 80 becomes the load pressure isolation valve 45 controlled. This will be the load pressure in the hydraulic motor 35 or tank pressure selected. The pump displacement of the variable displacement pump 1 is in accordance with a differential pressure between the pump pressure and that of the shuttle valve 29 controlled selected high pressure side load pressure.

Thus, when the load pressure is generated in the work machine circuit, the pump displacement of the variable displacement pump 1 according to a differential pressure between the pump pressure and the high-pressure side load pressure under the maximum load pressure in the work machine circuit and the load pressure in the steering drive device 30 controlled. When no load pressure is generated in the work machine circuit, the pump displacement of the variable displacement pump 1 according to a differential pressure between the pump pressure and that of the shuttle valve 29 under the load pressure of the steering drive device 30 and the load pressure of the hydraulic motor 35 controlled selected high pressure side load pressure.

Third embodiment

The 5 and 6 show a hydraulic circuit with a fan drive system according to a third embodiment of the present invention. A circuit structure for charging the precursor oil line 80 with a load pressure in the third embodiment is different from those of the first and second embodiments. The further construction in 5 is similar to the one in 2 12, which is a circuit structure of the first embodiment, and the other structure in FIG 6 is similar to the one in 4 shown circuit structure, which is a circuit structure of the second embodiment.

Regarding 5 in which the priority valve 3 is not provided, the same structure as that of the first embodiment and the same parts of the third embodiment, which are the same as those of the first embodiment, provided with the same reference numerals, and their explanation will be omitted. Regarding 6 where the prority valve 3 is used, the same structure as that of the second embodiment and the same parts of the third embodiment, which are the same as those of the first embodiment, are given the same reference numerals, and explanation thereof will be omitted.

As in the 5 and 6 is shown, the structure of a load pressure isolation valve differs 46 the third embodiment of the load pressure-separating valve 45 in the embodiments 1 and 2. That is, as in the 5 and 6 is shown is the load pressure isolation valve 46 of the third embodiment is designed as a two-position and two-opening switching valve. A throttling 87 is in the precursor oil line 83 disposed downstream of the flow control valve 37 is connected.

The precursor oil line 83 Branches downstream of the throttling 87 , and one of the abge branched lines, ie a precursor oil line 80 is with the shuttle valve 29 connected. The other branched pre-stage oil line is with the tank 50 via the arranged at an intermediate region load pressure-separating valve 46 connected.

When a load pressure in the lifting cylinders 13A and 13B or tilt cylinders 20A and 20B is generated, the load pressure in the Arbeitsmaschinenkreis on the precursor oil line 79 on the load pressure isolation valve 46 applied. This will be the load pressure isolation valve 46 switched to a switching position in which the precursor oil line 83 in communication with the tank 50 brought is. At this time, a change-over valve 29 supplied pressure in the precursor oil line 80 a tank pressure, and the tank pressure is called the load pressure the shuttle valve 29 fed.

That is, the tank pressure is considered by the precursor oil valve 80 to the shuttle valve 29 fed supplied load pressure. Because the throttling 87 upstream of the precursor oil line 80 is provided, the load pressure of the hydraulic motor 35 from the throttling 87 held.

Therefore, in the in 5 shown hydraulic circuit at this time one of the shuttle valve 27 selected high-pressure side load pressure from the shuttle valve 29 the precursor oil line 85 given up. In the in 6 shown hydraulic circuit is one of the shuttle valve 28 selected high-pressure side load pressure from the shuttle valve 29 on the precursor oil line 85 given up.

That is, one of the precursor oil line 85 from the shuttle valve 29 output high-pressure side load pressure is the maximum load pressure of the work machine circuit in the case of in 5 and is a high pressure side load pressure below the maximum load pressure of the work machine circuit and the load pressure in the steering drive device 30 in the case of in 6 shown hydraulic circuit. The pump displacement of the variable displacement pump 1 becomes in accordance with a differential pressure between the high-pressure-side load pressure, the precursor oil line 85 is abandoned, and controlled the pump pressure of the variable.

If no load pressure in the working machine in the lifting cylinders 13A and 13B or tilt cylinders 20A and 20B is generated, the load pressure-separating valve 46 switched to the switching position in which the connection between the precursor oil line 83 and the tank 50 is cut off. At this time, in the in 5 shown hydraulic circuit, the precursor oil line 85 from the shuttle valve 29 with the load pressure of the hydraulic motor 35 applied. In the in 6 shown hydraulic circuit is the precursor oil line 85 with a high pressure side load pressure below that of the shuttle valve 28 selected high-pressure side load pressure and a load pressure in the hydraulic motor 85 applied. The displacement control device 2 is in accordance with a differential pressure between the high-pressure side load pressure, with the precursor oil line 85 is applied, and the pump pressure of the variable 1 controlled.

Fourth embodiment

7 shows a hydraulic circuit with a fan drive system according to the fourth embodiment of the present invention. In the fourth embodiment, similar structures to those of the second embodiment will be given the same reference numerals and the description thereof will be omitted. In the fourth embodiment, a control structure for controlling the flow rate of the hydraulic motor differs 35 supplied oil from the control structure for controlling a flow rate of the hydraulic motor 35 supplied oil in the second embodiment.

The rest Structure is the same as that of the second embodiment. Consequently are the same in the fourth embodiment Structure like that of the second embodiment, the same Provide parts with the same reference numerals and their explanations will be omitted.

With regard to the construction of the load pressure separating valve 45 The fourth embodiment will be the structure of the load pressure cutoff valve 45 used, which is explained in the second embodiment, but the construction using the throttling 87 and the load pressure isolation valve 46 which is explained in the third embodiment, may also be for the construction of the load pressure-separating valve 45 of the fourth embodiment. As a control structure for controlling the flow rate of the hydraulic motor 35 supplied oil for the fourth embodiment, a control structure for controlling the flow rate of the hydraulic motor 35 supplied oil can be used as in 2 and 5 is shown.

One from the oil pipe 57 upstream of the flow control valve 37 branched oil line 61 is with a decompression valve 43 connected. The decompression valve 43 is from a thermo module 38 controlled. When a coolant temperature is high, the thermal module increases 38 a spring force of a spring 43a , and when the coolant temperature is low, the thermal module decreases 38 the spring force of the spring 43a ,

Therefore, at high coolant temperature, high pressure oil from the decompression valve 43 on the flow control valve 37 applied. This will be the flow control valve 37 controlled so that its opening area is increased, and the flow rate of the hydraulic motor 35 supplied oil can be increased. Therefore, the cooling fan 36 can be rotated at a higher speed, the amount of wind supplied to the radiator can be increased and the coolant temperature can be reduced.

If the coolant temperature is low, the thermal module will decrease 38 the spring force of the spring 43a , and decompressed oil is released from the decompression valve 43 on the flow control valve 37 applied. The flow control valve 37 is controlled so that its opening area is reduced, and the flow rate of the hydraulic motor 35 supplied oil is reduced. This turns the cooling fan 36 braked, the amount of wind supplied to the radiator is reduced and the coolant temperature can be increased.

Fifth embodiment

8th shows a hydraulic circuit with a fan drive system according to a fifth embodiment of the present invention. In the fifth embodiment, the same parts as those of the second embodiment are denoted by the same reference numerals, and explanation thereof will be omitted. In the fifth embodiment, as a control structure for controlling a flow rate of the hydraulic motor 35 supplied an adjustable throttle valve 39 used. A pressure compensation valve 42 is downstream of the variable throttle valve 39 arranged, and provided as a second precursor oil line precursor oil line 84 , which is a hydraulic pump (hydraulic pump pressure) downstream of the pressure compensating valve 42 detected is with the load pressure isolation valve 45 connected. These structures of the fifth embodiment are different from those of the second embodiment.

The rest Structure is the same as that of the first embodiment (second embodiment). Therefore, in the fourth (fifth) Embodiment the same parts as those of the second Embodiment provided with the same reference numerals and their explanation is omitted.

As a construction of a load pressure cutoff valve of the fifth embodiment, an example in which the structure of the load pressure cut valve explained in the second embodiment is applied 45 is shown, but the structure of the explained in the third embodiment throttling 87 and the load pressure release valve 46 For example, in the fifth embodiment, instead of the load pressure cut valve 45 be used. A control structure for controlling a flow rate of the hydraulic motor 35 supplied oil in the fifth embodiment, instead of the control structure for controlling the flow rate of the hydraulic motor 35 supplied oil to be used in the 2 and 5 is shown.

The adjustable throttle valve 39 is through the thermo module 38 controlled. When the coolant temperature is high, the thermal module will control 38 the adjustable throttle valve 39 to the complete communication state against a spring force of a spring 39a , When the coolant temperature is low, the variable throttle amount of the variable throttle valve becomes 39 according to the thermomodule 38 detected coolant temperature controlled.

Therefore, at high coolant temperature, a large amount of oil of the oil passage 57 from the adjustable throttle valve 39 the pressure compensation valve 42 be supplied. If the coolant temperature is low, the oil in the oil line 57 the pressure compensation valve 42 from the adjustable throttle valve 39 be supplied in the throttled state.

The pressure compensation valve 42 becomes in accordance with a differential pressure between a downstream of the variable throttle valve 39 from a precursor oil line 82 removed hydraulic pump pressure and the highest of a pressure in the precursor oil line 78 , ie the load pressures in the lifting cylinders 13A and 13B , the load pressures in the tilt cylinder 20A and 20B and a load pressure in the steering drive device 30 switched and controlled.

When a pressure in the precursor oil line 78 greater than a pressure in the oil line 57 is, the pressure compensation valve stops 42 the oil supply in the oil line 57 to the hydraulic motor 37 , That is, when a pressure in the precursor oil line 78 higher than a pump pressure of the variable displacement pump 1 can the total flow rate of the variable displacement pump 1 the lifting cylinders 13A and 13B and the pitch cylinders 20A and 20B , which are work machines represent, and the operation of the hydraulic motor 35 is temporarily stopped. Thus, the work machine is a large amount of oil available.

When the pressure in the precursor oil line 78 essentially equal to the pressure in the oil line 57 will or if the pressure in the oil line 57 greater than the pressure in the pre-stage oil line 78 , can the pressure compensation valve 42 the oil of the oil pipe 57 the hydraulic motor 35 respectively. Industrial Applicability

The basis of the present invention This technical idea can be used for hydraulic pressure systems requiring control of a load-sensitive type variable displacement pump incorporating a load pressure in a hydraulic motor driving a cooling fan.

Summary

The The present invention provides a blower drive system ready at the when load generation in a work machine a Pump displacement of a variable displacement pump according to the Load of the working machine can be controlled, and if not in the load is generated in the working machine, the pump displacement the variable displacement pump according to a load pressure of a controlled a cooling fan driving hydraulic motor can be.

A flow control valve controlled based on a coolant temperature 37 is arranged in an oil line, through which oil from a variable displacement pump 1 a hydraulic motor 35 is supplied, wherein the variable displacement pump 1 a swash plate and the swash plate angle of a displacement control device 2 is controlled. A precursor oil line 83 for detecting a load pressure of the hydraulic motor 35 is with a shuttle valve 29 via a load pressure isolation valve 45 connected. A maximum load pressure in a work machine circle 33 and a load pressure of a precursor oil line 80 be the shuttle valve 29 fed. One of the shuttle valve 29 selected high-pressure side load pressure becomes the displacement control device 2 via a precursor oil line 85 fed. The load pressure isolation valve 45 is due to a load pressure from a precursor oil line 79 controlled. When a load pressure is generated in the work machine, the load pressure cut valve intersects 45 a communication between the precursor oil line 83 and the shuttle valve 29 off to the shuttle valve 29 to apply a tank pressure.

1

variable

2

Displacement control device

3

priority valve

4

way valve with electromagnetic switching

8th

First direction switching valve

13A, 13B

lifting cylinder

17

Second direction switching valve

20A, 20B

tilt cylinder

27 to 29

shuttle valve (Two-way valve)

30

Steering drive device

31

actuator (Actuator)

33

Working machine circuit

34

steering circuit

35

hydraulic motor

36

cooling fan

37

flow control

38

thermo-module

39

adjustable throttle valve

40

switching valve for normal / reverse rotation

41

solenoid valve for normal / reverse rotation

42

Pressure compensation valve

43

Pressure relief valve

45

Valve for load pressure separation

46

Valve for load pressure separation

92

Main hydraulic pump

95

hydraulic motor

96

cooling fan

98

control device

101

LS Valve

104

hydraulic fixed displacement pump

106

drain valve

107

relief valve

108

flow control

best

kind for carrying out the invention

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 2000-161060 [0016]

Claims (5)

Blower drive system characterized by: a load pressure-sensitive variable displacement pump; a work machine circle and a flow control valve to which a discharge flow rate the variable displacement pump is supplied; a load pressure isolation valve, which is controlled by a maximum load pressure in the work machine circuit; one a cooling fan driving hydraulic motor; a first delivery oil line containing the variable displacement pump and the working machine circuit connects with each other; a second discharge oil line, which is branched from the first discharge oil line and connecting them to the flow control valve; a Feed oil line containing the flow control valve and connects the hydraulic motor with each other; a first precursor oil line, which extracts the maximum load pressure in the work machine circuit; a second precursor oil line, one the hydraulic motor removes driving load pressure; and a shuttle valve that between the maximum load pressure in the first precursor oil line and the load pressure in the second precursor oil passage, a high-pressure side Load pressure selects, where a pump displacement the variable displacement pump according to a differential pressure between the high pressure side selected by the shuttle valve Load pressure and a pump pressure of the variable displacement pump is controlled, the Load pressure isolation valve in the second pre-stage oil line is arranged, the load pressure release valve according to a Differential pressure between a compressive force of the by the first Precursor oil line taken from maximum load pressure and a biasing force acting on the load pressure separating valve Spring is controlled, when the compressive force of the maximum Load pressure is greater than the preload force of Spring, the load pressure relief valve from a position in which the second precursor oil line brought in conjunction with the shuttle valve, in one position is switched, in which the second precursor oil line brought in conjunction with a tank and the shuttle valve is subjected to a tank pressure, and when the pressure force from the maximum load pressure less than the biasing force of the spring is the load pressure relief valve from the position in which the second Pre-stage oil line brought into communication with the tank is switched to a position in which the second precursor oil line brought into communication with the shuttle valve, and the shuttle valve is acted upon by the hydraulic motor driving load pressure. Blower drive system characterized by: a load pressure-sensitive variable displacement pump; a work machine circle and a flow control valve to which a discharge flow rate the variable displacement pump is supplied; a load pressure isolation valve, which is controlled by a maximum load pressure in the work machine circuit; one a cooling fan driving hydraulic motor; a first delivery oil line containing the variable displacement pump and the working machine circuit connects with each other; a second discharge oil line, which is branched from the first discharge oil line and connecting them to the flow control valve; a Feed oil line containing the flow control valve and connects the hydraulic motor with each other; a first precursor oil line, which extracts the maximum load pressure in the work machine circuit; a second precursor oil line, one the hydraulic motor removes driving load pressure; and one in the second precursor oil line arranged throttling; and a shuttle valve between the maximum load pressure in the first pre-stage oil line and the load pressure in the second precursor oil passage, a high-pressure side Load pressure selects, where a pump displacement the variable displacement pump according to a differential pressure between the high pressure side selected by the shuttle valve Load pressure and a pump pressure of the variable displacement pump is controlled, the second precursor oil line downstream of the restriction is branched into two oil lines, with one of the branched oil lines connected to the shuttle valve, the load pressure relief valve on an intermediate region of the other oil line arranged is, and the other oil line connected to a tank is the load pressure release valve according to a Differential pressure between a compressive force of the by the first Precursor oil line taken from maximum load pressure and a biasing force acting on the load pressure separating valve Spring is controlled, when the compressive force of the maximum Load pressure is greater than the preload force of Spring, the load pressure relief valve is switched to a position in the second precursor oil line in conjunction with a Tank is brought and applied to the shuttle valve with a tank pressure will, and when the pressing force is lower from the maximum load pressure as the biasing force of the spring, the load pressure release valve of the position in which the second precursor oil line in Communication with the tank is brought into a position in which the communication is cut off and the shuttle valve is acted upon by the hydraulic motor driving load pressure. Blower drive system characterized by: a load pressure-sensitive variable displacement pump; a steering circuit, a work machine circuit, and a flow control valve to which a discharge flow rate is supplied from the variable displacement pump; a priority valve which preferably supplies the discharge flow rate from the variable displacement pump to the steering circuit by using the steering circuit as a circle preferable to the work machine circuit; a load pressure relief valve controlled by a maximum load pressure in the work machine circuit; a hydraulic motor that drives a cooling fan; a third discharge oil passage connecting the variable displacement pump and the priority valve; a fourth delivery oil passage connecting the priority valve and the steering circuit; a fifth discharge oil passage connecting the priority valve and the work machine circuit; a sixth discharge oil passage branched from the third discharge oil passage and connected to the flow control valve; a supply oil passage connecting the flow control valve and the hydraulic motor; a first precursor oil line taking the maximum load pressure in the work machine circuit; a second precursor oil line that takes a load pressure to drive the hydraulic motor; a third precursor oil line taking a load pressure in the steering circuit; a first shuttle valve that selects a high-pressure side load pressure from the maximum load pressure in the first stage oil line and the load pressure in the third stage oil line; and a second shuttle valve that selects a high-pressure side load pressure from the high-pressure-side load pressure selected by the first shuttle valve and the load pressure in the second pilot-stage oil passage, wherein a pump displacement of the variable displacement pump is selected according to a differential pressure between the high-pressure-side load pressure selected by the second shuttle valve and a pump pressure Variable displacement pump is controlled, the load pressure release valve is disposed in the second precursor oil line, the load pressure release valve according to a differential pressure between a pressure force from the extracted by the first precursor oil line maximum load pressure and a force acting on the load pressure release valve biasing force of a spring is controlled when the pressure force of the maximum load pressure is greater than the biasing force of the spring, the load pressure release valve from a position in which the second precursor oil line is brought into communication with the shuttle valve in a Position is switched, in which the second precursor oil line is brought into communication with a tank and the shuttle valve is pressurized with a tank pressure, and when the pressure force of the maximum load pressure is less than the biasing force of the spring, the load pressure relief valve from the position in the second precursor oil line is brought into communication with the tank, is switched to a position in which the second precursor oil line is brought into communication with the shuttle valve, and the shuttle valve is acted upon by the load pressure driving the hydraulic motor. Blower drive system, characterized by: a load pressure-sensitive variable displacement pump; a steering circuit, a work machine circuit, and a flow control valve to which a discharge flow rate is supplied from the variable displacement pump; a priority valve which preferably supplies the discharge flow rate from the variable displacement pump to the steering circuit by using the steering circuit as a circle preferable to the work machine circuit; a load pressure relief valve controlled by a maximum load pressure in the work machine circuit; a hydraulic motor that drives a cooling fan; a third discharge oil passage connecting the variable displacement pump and the priority valve; a fourth discharge oil passage connecting the priority valve and the steering circuit; a fifth discharge oil passage connecting the priority valve and the work machine circuit; a sixth discharge oil passage branched from the third discharge oil passage and connected to the flow control valve; a supply oil passage connecting the flow control valve and the hydraulic motor; a first precursor oil line taking the maximum load pressure in the work machine circuit; a second precursor oil line that takes a load pressure to drive the hydraulic motor; a third precursor oil line taking a load pressure in the steering circuit; a restriction disposed in the second precursor oil passage; a first shuttle valve that selects a high-pressure side load pressure from the maximum load pressure in the first stage oil line and the load pressure in the third stage oil line; and a second shuttle valve that selects a high-pressure side load pressure from the high-pressure-side load pressure selected by the first shuttle valve and the load pressure in the second pilot-stage oil passage, wherein a pump displacement of the variable displacement pump is selected according to a differential pressure between the high-pressure-side load pressure selected by the second shuttle valve and a pump pressure Variable displacement pump is controlled, the second precursor oil line is branched downstream of the throttling in two oil lines, wherein one of the branched oil lines with the change Valve is connected, the load pressure release valve is disposed at an intermediate portion of the other oil passage, and the other oil passage is connected to a tank, the load pressure release valve according to a differential pressure between a pressure force from the extracted by the first precursor oil line maximum load pressure and acting on the load pressure relief valve A biasing force of a spring is controlled when the pressing force of the maximum load pressure is greater than the biasing force of the spring, the load pressure release valve is switched to a position in which the second precursor oil line is brought into communication with a tank and pressurizes the shuttle valve with a tank pressure is, and when the pressing force of the maximum load pressure is less than the biasing force of the spring, the load pressure release valve from the position in which the second precursor oil line is brought into communication with the tank, is switched to a position in which the communication is cut off and the shuttle valve is acted upon by the hydraulic motor driving load pressure. Blower drive system according to one of the claims 1 to 5, characterized in that the flow control valve according to a temperature of a coolant is controlled.