JP2010150043A - Fluid pressure circuit for wheel type crane - Google Patents

Abstract

[PROBLEMS] To simplify the structure, reduce costs and reduce fuel consumption.
A hydraulic circuit of a wheel crane includes a telescopic cylinder, a hoisting cylinder, a front shaft traveling motor, a hydraulic pump, and a switching valve. The switching valve 12 is disposed between the hydraulic pump 3 and the working hydraulic cylinder (the expansion / contraction cylinder 10 and the hoisting cylinder 11) and between the hydraulic pump 3 and the front shaft travel motor 8. . The switching valve 12 can supply the pressure oil from the hydraulic pump 3 to the expansion cylinder 10 and the hoisting cylinder 11 and the pressure oil from the hydraulic pump 3 to the front shaft traveling motor 8. The second switching position and the pressure oil from the hydraulic pump 3 are supplied to the front shaft traveling motor 8, and the hydraulic fluid returning from the front shaft traveling motor 8 to the switching valve 12 is supplied to the telescopic cylinder 10 and the undulating cylinder 11. It is possible to switch to a possible third switching position.
[Selection] Figure 1

Description

  The present invention relates to a fluid pressure circuit of a wheel crane.

  A hydraulic circuit of a conventional construction machine is shown in FIG. As shown in FIG. 6, the hydraulic circuit includes a telescopic cylinder 10 and a hoisting cylinder, which are working hydraulic actuators, via a hoisting / extension switching valve 24, in a gear box 2 installed in a prime mover 1 (engine). And a pump 70b for supplying hydraulic oil to the main winding motor 74 and the auxiliary winding motor 75 which are working hydraulic actuators via the main / auxiliary switching valve 25. Yes. The undulation / extension switching valve 24 controls the flow rate and direction of the hydraulic oil supplied from the pump 70a, and controls the movements of the expansion cylinder 10 and the undulation cylinder 11. The main winding / auxiliary switching valve 25 controls the flow rate and direction of the hydraulic oil supplied from the pump 70 b and controls the movement of the main winding motor 74 and the auxiliary winding motor 75. In addition, a pump 71 is provided for supplying hydraulic oil to a swing motor (not shown) via the swing switching valve 29. The turning switching valve 29 controls the flow rate and direction of the hydraulic oil supplied from the pump 71 and controls the movement of the turning motor. Further, the front shaft traveling motor 8 and the rear shaft traveling motor 9 which are traveling hydraulic actuators provided to move the entire vehicle independently of the pump, and a pump for supplying hydraulic oil to the motors 8 and 9. In this configuration, two sets of traveling hydraulic transmission devices (hereinafter referred to as traveling HST) configured to include 72a and 72b are additionally provided.

  The front shaft travel motor 8 and the rear shaft travel motor 9 are rotated by hydraulic oil supplied to the front shaft travel motor 8 and the rear shaft travel motor 9 from the pumps 72a and 72b of the two sets of travel HST, and the vehicle Run. The pump capacity and the motor capacity are controlled by controlling the tilt angles of the pumps 72a and 72b and the traveling motors 8 and 9. Thereby, the speed and acceleration of the vehicle are controlled. A hydraulic circuit of a hydraulic excavator is disclosed in Patent Document 1.

Japanese Patent No. 2777702

  However, in the hydraulic circuit shown in FIG. 6 described above, a pump for driving the working hydraulic actuator and the traveling hydraulic actuator is required separately, so that the structure of the gear box 2 for transmitting power becomes complicated. In addition to the need for thick pipes for each pump to suck in oil and increasing the number of parts, the pumps 70a and 70b for driving the working hydraulic actuators are equipped with a controller for controlling the pump capacity. Is expensive. Therefore, the cost becomes high. In addition, when the vehicle is traveling, the pumps 70a and 70b that drive the working hydraulic actuators idle so that there is a problem that power loss occurs and the travel fuel consumption increases. Further, during the crane work, the pumps 72a and 72b that drive the traveling hydraulic actuators idle so that there is a problem that power loss occurs and the crane work fuel consumption increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluid pressure circuit of a wheel type crane that can simplify the structure and reduce cost and fuel consumption.

  The present invention relates to a fluid pressure circuit of a wheel crane. The fluid pressure circuit according to the present invention has the following features in order to achieve the above object. That is, the fluid pressure circuit of the present invention includes the following features alone or in combination as appropriate.

  The first feature of the fluid pressure circuit according to the present invention for solving the above problems is that the working fluid pressure actuator, the traveling fluid pressure actuator, the working fluid pressure actuator, and the traveling fluid pressure actuator operate. A fluid pressure pump capable of supplying fluid; a working fluid pressure actuator; a traveling fluid pressure actuator; and a switching means provided between the fluid pressure pump, wherein the switching means includes the fluid pressure A first state in which working fluid from a pump can be supplied to the working fluid pressure actuator; a second state in which working fluid from the fluid pressure pump can be supplied to the traveling fluid pressure actuator; and from the fluid pressure pump Can be switched to the third state in which the working fluid pressure can be simultaneously supplied to the traveling fluid pressure actuator and the working fluid pressure actuator. A.

  According to this configuration, since the working fluid pressure actuator and the traveling fluid pressure actuator are driven by one fluid pressure pump, the number of pumps is reduced. Therefore, the structure of the fluid pressure circuit can be simplified. In addition, when carrying out crane work or traveling, fuel consumption can be reduced by reducing power consumption compared to conventional hydraulic circuits by reducing the number of pumps. Further, the cost can be reduced by reducing the number of pumps and simplifying the structure of the fluid pressure circuit.

A second feature of the fluid pressure circuit according to the present invention is that the switching means includes a first on-off valve provided between the working fluid pressure actuator and the fluid pressure pump, and the traveling fluid pressure. A second on-off valve provided between the actuator and the fluid pressure pump.
The on-off valve is a valve that can be switched between a state in which the valve is open, a state in which the valve is closed, and an intermediate state (a state in which the valve is throttled).

  In this configuration, the fluid pressure circuit includes a first on-off valve provided on the working fluid pressure actuator side and a second on-off valve provided on the traveling fluid pressure actuator side. Therefore, when the working fluid is supplied to the working fluid pressure actuator and the traveling fluid pressure actuator simultaneously (in the third state), when one of the two actuators is low in load, The valve opening degree of only the on-off valve provided on the low actuator side can be reduced (effective pressure loss is added). Therefore, when the load of one of the two actuators is low, a high load can be applied to the other actuator.

  According to a third feature of the fluid pressure circuit of the present invention, the first on-off valve and the second on-off valve are poppet valves.

  According to this configuration, since the first on-off valve and the second on-off valve are poppet valves, there is less pressure loss than the spool valve. Therefore, the efficiency of the fluid pressure circuit is better than when the first on-off valve or the second on-off valve is a spool valve.

  According to a fourth aspect of the fluid pressure circuit of the present invention, the switching means is a three-position switching valve, and the first switching capable of supplying the working fluid from the fluid pressure pump to the working fluid pressure actuator. A position, a second switching position where the working fluid from the fluid pressure pump can be supplied to the traveling fluid pressure actuator, a working fluid from the fluid pressure pump supplied to the traveling fluid pressure actuator, and the traveling The working fluid returning to the switching valve from the working fluid pressure actuator can be switched to a third switching position where the working fluid pressure actuator can be supplied to the working fluid pressure actuator.

  As in this configuration, the first feature can be obtained by using the three-position switching valve as the switching means.

  The fifth feature of the fluid pressure circuit according to the present invention is that an impeller centrifugal pump is connected to the working fluid suction side of the fluid pressure pump.

  According to this configuration, a decrease in fluid pressure on the working fluid suction side of the fluid pressure pump can be suppressed by supplying the working fluid to the working fluid suction side of the fluid pressure pump by the impeller centrifugal pump. Therefore, cavitation can be prevented.

  The sixth feature of the fluid pressure circuit according to the present invention is that the drive shaft of the impeller centrifugal pump is connected to the drive shaft of the fluid pressure pump through a clutch.

  According to this configuration, when there is no need to suppress a decrease in the fluid pressure on the working fluid suction side of the fluid pressure pump, the impeller centrifugal pump can be stopped from rotating by setting the clutch in a separated state. Accordingly, idling power of the impeller centrifugal pump can be reduced, and deterioration of fuel consumption can be suppressed.

  A seventh feature of the fluid pressure circuit according to the present invention is that the fluid pressure circuit includes a first prime mover that drives the fluid pressure pump and a second prime mover that drives the impeller centrifugal pump.

  According to this configuration, since the second prime mover for driving the impeller centrifugal pump is provided separately from the first prime mover for driving the fluid pressure pump, it is not necessary to install the impeller centrifugal pump on the shaft of the fluid pressure pump. Therefore, the arrangement of the impeller centrifugal pump is facilitated, and the degree of freedom in designing the overall layout can be obtained.

  As described above, the fluid pressure circuit according to the present invention includes, in particular, a working fluid pressure actuator and switching means provided between the traveling fluid pressure actuator and the fluid pressure pump. The number of pumps is reduced by the configuration that can be switched from the first state to the third state. Therefore, the structure of the fluid pressure circuit can be simplified. In addition, fuel consumption can be reduced by reducing power consumption by reducing the number of pumps compared to conventional hydraulic circuits. Further, the cost can be reduced by reducing the number of pumps and simplifying the structure of the fluid pressure circuit.

It is the figure which showed the hydraulic circuit of the wheel type crane which concerns on 1st Embodiment. It is an enlarged view of C site | part shown in FIG. It is the figure which showed the hydraulic circuit of the wheel type crane which concerns on 2nd Embodiment. It is the figure which showed the hydraulic circuit of the wheel type crane which concerns on 3rd Embodiment. It is the figure which showed the hydraulic circuit of the wheel type crane which concerns on 4th Embodiment. It is the figure which showed the hydraulic circuit of the conventional construction machine.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a view showing a hydraulic circuit (fluid pressure circuit) of the wheel crane according to the present embodiment. FIG. 2 is an enlarged view of a portion C shown in FIG. As shown in FIG. 1, the hydraulic circuit of the wheel type crane includes a prime mover 1. The prime mover 1 drives the hydraulic pumps 3 and 4 (fluid pressure pump) and the turning hydraulic pump 5 via the gear box 2.

  The hydraulic pumps 3 and 4 are configured as bidirectional variable displacement pumps, and the tilt angles of the hydraulic pumps 3 and 4 are controlled by the regulators 7. The regulator 7 is connected to the pilot pressure source 28 via the electromagnetic switching valve 6, and a controller (not shown) is electrically connected to the electromagnetic switching valve 6. The controller outputs a control signal to the electromagnetic switching valve 6 to change the operation stroke of each regulator 7 to control the tilt angle of the hydraulic pumps 3 and 4. Thereby, the pump capacity of the hydraulic pumps 3 and 4 can be controlled.

  Then, the front shaft traveling motor 8 (traveling fluid pressure actuator), the telescopic cylinder 10 (working fluid pressure actuator), and the undulation cylinder 11 (working fluid) are supplied by the working oil (working fluid) supplied from the hydraulic pump 3. Pressure actuator) is driven. The hydraulic oil supplied from the hydraulic pump 4 causes the rear shaft traveling motor 9 (traveling fluid pressure actuator), the main winding motor 74 (working fluid pressure actuator), and the auxiliary winding motor 75 (working fluid pressure actuator). Driven. The front shaft traveling motor 8 and the rear shaft traveling motor 9 are connected to a traveling speed reducer (not shown) that reduces the rotational force of the front shaft traveling motor 8 and the rear shaft traveling motor 9 and transmits it to the traveling drive wheels. Has been.

  On the other hand, the turning hydraulic pump 5 is configured as a fixed displacement pump. The turning hydraulic pump 5 and a turning switching valve 29 for supplying hydraulic oil to a turning motor (not shown) for turning the upper body are connected by an oil passage 50, and the turning hydraulic pump 5 is connected to a suction oil passage. A swing motor (not shown) is driven by the hydraulic oil sucked from the tank T via 60. The hydraulic oil used for driving the swing motor is returned to the tank T via the return oil passage 61.

The hydraulic circuit of the wheel type crane according to the present embodiment includes a hydraulic circuit constituting an HST (Hydro Static Transmission) system (hereinafter referred to as an HST system) for driving the front shaft traveling motor 8 using the hydraulic pump 3 as a hydraulic source. A hydraulic circuit constituting an HST system for driving the rear shaft travel motor 9 using the hydraulic pump 4 as a hydraulic source is provided.

  As shown in FIG. 1, the hydraulic circuit constituting the HST system for driving the front shaft traveling motor 8 using the hydraulic pump 3 as a hydraulic pressure source is composed of a pump circuit A1 and a motor circuit B1. The hydraulic circuit constituting the HST system for driving the rear shaft traveling motor 9 using the hydraulic pump 4 as a hydraulic pressure source includes a pump circuit A2 and a motor circuit B2. A switching valve 12 (switching means) capable of switching the oil path is disposed between the front shaft traveling motor 8 and the hydraulic pump 3, and is disposed between the rear shaft traveling motor 9 and the hydraulic pump 4. Is provided with a switching valve 13 (switching means) capable of switching the oil passage.

  The pump circuit A1 includes a hydraulic pump 3, a pair of overload relief valves 15a and 15b for regulating the maximum pressure of the circuit between the hydraulic pump 3 and the front shaft travel motor 8, and each overload relief valve 15a. , 15b and check valves 16a, 16b and a relief valve 14 provided in parallel. The hydraulic pump 3 is provided with ports 3a and 3b. When the port 3a of the hydraulic pump 3 shown in FIG. 2 is a discharge port and the port 3b is a suction port, the hydraulic pressure of the circuit between the hydraulic pump 3 and the front shaft travel motor 8 (see FIG. 1) is a predetermined pressure. Is exceeded, hydraulic oil is discharged to the oil passage 39 by opening the overload relief valve 15a. As a result, hydraulic oil is supplied to the port 3b, which is a suction port, via the check valve 16b. When the oil pressure in the oil passage 39 is high, a part of the hydraulic oil is returned to the tank T by opening the relief valve 14.

  Since the pump circuit A2 has the same configuration as the above-described pump circuit A1, the description thereof is omitted. The impeller centrifugal pump 19 is connected to the pump circuit A1 and the pump circuit A2. The hydraulic oil sucked up from the tank T by the impeller centrifugal pump 19 through the suction oil passage 60 is supplied to the pump circuit A1 and the pump circuit A2. It is supplied to the circuit A2. Further, a check valve 17 is provided on the impeller centrifugal pump 19 side in order to prevent the hydraulic oil from flowing backward. Since the impeller centrifugal pump 19 can be formed thinner than the gear pump 73 shown in FIG. 6, it is not necessary to provide a larger installation space than the gear pump 73.

  The motor circuit B1 is provided with a front shaft traveling motor 8 shown in FIG. 1, a flushing valve 20 for discharging excess oil in the circuit to the outside of the circuit, a relief valve 21, and an electromagnetic switching valve 22.

  Since the motor circuit B2 has the same configuration as the motor circuit B1 described above, the description thereof is omitted.

  The switching valve 12 is a three-position five-port switching valve, is of a spool type, and is disposed between the expansion / contraction cylinder 10 and the hoisting cylinder 11 and the hydraulic pump 3. Oil passages 30 and 31 communicating with the hydraulic pump 3 are connected to two ports of the switching valve 12 on the hydraulic pump 3 side. Further, the three ports on the front shaft travel motor 8 side of the switching valve 12 are provided with oil passages 32 and 33 communicating with the front shaft travel motor 8, an expansion / contraction cylinder 10 for expanding and contracting the boom, and a hoisting cylinder for lifting the boom. 11 are connected to oil passages 34 communicating with the undulation / extension switching valve 24 for supplying hydraulic oil to the oil supply 11. A pilot pipe 62 connected to the pilot pressure source 28 and a drain pipe 63a are connected to the proportional valves 23a and 23b provided on both sides of the switching valve 12.

  The switching valve 13 is a three-position five-port switching valve, is of a spool type, and is disposed between the main winding motor 74 and auxiliary winding motor 75 and the hydraulic pump 4. Oil passages 40 and 41 communicating with the hydraulic pump 4 are connected to the two ports on the hydraulic pump 4 side of the switching valve 13, respectively. The three ports on the rear shaft travel motor 9 side of the switching valve 13 are connected to main passage motors 42 and 43 communicating with the rear shaft travel motor 9, and main oil for supplying main oil to the main winding motor 74 and auxiliary winding motor 75. An oil passage 44 communicating with the winding / auxiliary switching valve 25 is connected to each other. A pilot pipe 62 connected to the pilot pressure source 28 and a drain pipe 63a are connected to the proportional valves 23c and 23d provided on both sides of the switching valve 13.

  The switching valve 12 is based on the operation of a shift lever (not shown) by an operator, and the first position 12a (first state, first switching position), the second position 12b (second state, second switching position). , And can be switched to any one of the third position 12c (third state, third switching position), and the switching valve 13 has a first position 13a (first state, first switching position), a second position 13b (first position). 2 state, 2nd switching position) and 3rd position 13c (3rd state, 3rd switching position) can be switched. Specifically, the pilot pressure (primary pressure) supplied from the pilot pressure source 28 is changed to the pilot pressure (secondary pressure) by the current flowing through the proportional valves 23a and 23b. Thereby, a pressure difference arises between the proportional valve 23a and the proportional valve 23b, and the switching valve 12 is switched based on the pressure difference. Similarly, the switching valve 13 is switched based on the pressure difference between the proportional valve 23c and the proportional valve 23d.

  In the first position 12a of the switching valve 12, the oil passage 30 and the oil passage 34 are communicated, the oil passage 32 and the oil passage 33 are communicated, and the port to which the oil passage 31 is connected is blocked. In the second position 12b, the oil passage 30 and the oil passage 32 are communicated, the oil passage 31 and the oil passage 33 are communicated, and the port to which the oil passage 34 is connected is blocked. In the third position 12c, the oil passage 31 and the oil passage 33 are communicated, the oil passage 32 and the oil passage 34 are communicated, and the port to which the oil passage 30 is connected is blocked.

  In the first position 13a of the switching valve 13, the oil passage 41 and the oil passage 44 are communicated, the oil passage 42 and the oil passage 43 are communicated, and the port to which the oil passage 40 is connected is blocked. In the second position 13b, the oil passage 41 and the oil passage 42 are communicated, the oil passage 40 and the oil passage 43 are communicated, and the port to which the oil passage 44 is connected is blocked. In the third position 13c, the oil passage 40 and the oil passage 43 are communicated, the oil passage 42 and the oil passage 44 are communicated, and the port to which the oil passage 41 is connected is blocked.

  The undulation / extension switching valve 24 includes an expansion / contraction switching valve 24 a that supplies hydraulic oil to the expansion cylinder 10 and a undulation switching valve 24 b that supplies hydraulic oil to the undulation cylinder 11. The expansion / contraction switching valve 24a is connected with an oil passage 35 communicating with the bottom chamber 10a of the expansion / contraction cylinder 10 and an oil passage 36 communicating with the rod chamber 10b. An oil passage 37 communicating with the bottom chamber 11a of the cylinder 11 and an oil passage 38 communicating with the rod chamber 11b are connected. The hydraulic oil discharged from the telescopic cylinder 10 and the hoisting cylinder 11 is returned to the tank T through the return oil passage 61. The undulation / extension switching valve 24 controls the flow rate and direction of hydraulic oil supplied from the hydraulic pump 3 and controls the movement of the expansion cylinder 10 and the undulation cylinder 11.

  The main winding / auxiliary winding switching valve 25 includes a main winding switching valve 25 a that supplies hydraulic oil to the main winding motor 74 and an auxiliary winding switching valve 25 b that supplies hydraulic oil to the auxiliary winding motor 75. . An oil passage 74a communicating with the main winding motor 74 is connected to the main winding switching valve 25a, and an oil passage 75a communicating with the auxiliary winding motor 75 is connected to the auxiliary winding switching valve 25b. Yes. Further, the hydraulic oil used for driving the main winding motor 74 and the auxiliary winding motor 75 is returned to the tank T through the return oil passage 61. The main winding / auxiliary switching valve 25 controls the flow rate and direction of the hydraulic oil supplied from the hydraulic pump 4 and controls the movement of the main winding motor 74 and the auxiliary winding motor 75.

  With such a configuration of the switching valves 12 and 13, the front shaft traveling motor 8, the telescopic cylinder 10 and the hoisting cylinder 11 are connected to the hydraulic pump 3 through the switching valve 12. The hydraulic pump 4 is connected to the rear shaft travel motor 9, the main winding motor 74, and the auxiliary winding motor 75 through the switching valve 13.

  By switching the switching valve 12 to the first position 12a, the pressure oil from the hydraulic pump 3 is supplied to the undulation / extension switching valve 24 via the switching valve 12. Then, the pressure oil is supplied to the bottom chamber 10 a of the expansion / contraction cylinder 10, and the hydraulic oil in the rod chamber 10 b of the expansion / contraction cylinder 10 is discharged to the return oil passage 61. As a result, the telescopic cylinder 10 can be extended, and the boom can be extended. On the other hand, the pressure oil is supplied to the rod chamber 10 b of the expansion / contraction cylinder 10, and the hydraulic oil in the bottom chamber 10 a of the expansion / contraction cylinder 10 is discharged to the return oil passage 61. Thereby, the expansion / contraction cylinder 10 can be contracted and the boom can be contracted. Further, by switching the switching valve 13 to the first position 13a, after the pressure oil from the hydraulic pump 4 is supplied to the main winding / auxiliary switching valve 25 via the switching valve 13, the main winding motor 74 and the auxiliary motor 74 are supplemented. It is supplied to the winding motor 75. As a result, the main winding motor 74 and the auxiliary winding motor 75 are driven. Thereafter, the hydraulic oil used to drive the main winding motor 74 and the auxiliary winding motor 75 is discharged to the return oil passage 61.

  By switching the switching valve 12 to the second position 12b, the pressure oil from the hydraulic pump 3 is supplied to the front shaft traveling motor 8 via the switching valve 12. Thereby, the front shaft traveling motor 8 is driven. Further, by switching the switching valve 13 to the second position 13b, the pressure oil from the hydraulic pump 4 is supplied to the rear shaft traveling motor 9 via the switching valve 13. Thereby, the rear shaft drive motor 9 is driven.

  By switching the switching valve 12 to the third position 12c, the pressure oil from the hydraulic pump 3 is supplied to the front shaft traveling motor 8 via the switching valve 12. Thereafter, the hydraulic oil used in the front shaft traveling motor 8 returns to the switching valve 12 through the oil passage 32, and the return oil is supplied to the undulation / extension switching valve 24 via the switching valve 12. That is, the hydraulic oil from the hydraulic pump 3 is simultaneously supplied to the front shaft traveling motor 8 and the undulation / extension switching valve 24. Accordingly, the telescopic cylinder 10 and the hoisting cylinder 11 can be driven in conjunction with the driving of the front shaft traveling motor 8. Further, by switching the switching valve 13 to the third position 13 c, the pressure oil from the hydraulic pump 4 is supplied to the rear shaft traveling motor 9 via the switching valve 13. Thereafter, the hydraulic oil used in the rear shaft drive motor 9 returns to the switching valve 13 through the oil passage 42, and the return oil is supplied to the main winding / auxiliary switching valve 25 via the switching valve 13. That is, the hydraulic oil from the hydraulic pump 4 is simultaneously supplied to the rear shaft travel motor 9 and the main / auxiliary switching valve 25. Thus, the main winding motor 74 and the auxiliary winding motor 75 can be driven in conjunction with the driving of the front shaft traveling motor 8.

  A drain pipe 63 b is connected to the flushing valve 20, and the hydraulic oil discharged through the flushing valve 20 is returned to the tank T through the return oil passage 61. The drain pipe 63b is provided with the electromagnetic switching valve 22 and the relief valve 21, and the electromagnetic switching valve 22 blocks the drain pipe 63b based on a signal from the controller. That is, the controller shuts the drain pipe 63b by sending a signal to the electromagnetic switching valve 22 in conjunction with the operation of the shift lever by the operator operating the shift lever 12 to switch to the third position 12c. As a result, the hydraulic oil supplied from the hydraulic pump 3 to the front shaft traveling motor 8 is not discharged to the tank T via the drain pipe 63b, so that the telescopic cylinder 10 and the hoisting cylinder are connected via the switching valve 12. 11 can suppress a reduction in the flow rate of the hydraulic oil supplied to the fuel tank 11. As a result, the movements of the telescopic cylinder 10 and the undulating cylinder 11 are not hindered.

  In addition, the controller shuts off the drain pipe 63b by sending a signal to the electromagnetic switching valve 22 in conjunction with an operation of the shift lever by the operator operating the shift lever 13 to switch to the third position 13c. As a result, the hydraulic oil supplied from the hydraulic pump 4 to the rear shaft travel motor 9 is not discharged to the tank T via the drain pipe 63b, so that the main winding motor 74 and the auxiliary winding motor are connected via the switching valve 13. A reduction in the flow rate of the hydraulic oil supplied to 75 can be suppressed. As a result, the movements of the main winding motor 74 and the auxiliary winding motor 75 are not hindered. Since the traveling system forms a closed circuit during traveling alone, the oil temperature becomes high. In order to cool this, the relief valve 21 releases the hydraulic oil to the drain pipe 63b when the hydraulic pressure in the low-pressure side oil passage opposite to the driving high-pressure side exceeds a predetermined pressure.

  An oil cooler 26 is provided in the return oil passage 61 of the hydraulic circuit. The hydraulic oil discharged from the telescopic cylinder 10 and the undulating cylinder 11 and the hydraulic oil discharged from the main winding motor 74 and the auxiliary winding motor 75 are cooled by the oil cooler 26 and returned to the tank T. A filter 27 for removing impurities mixed in the hydraulic oil and a check valve 18 are provided in parallel on the tank T side of the return oil passage 61 from the oil cooler 26.

  In the above configuration, when an accelerator (not shown) is operated, the electromagnetic switching valve 6 is switched and operated by a signal from the controller based on the operation signal, and the tilt angles of the hydraulic pumps 3 and 4 are increased. As a result, the hydraulic oil discharged from the hydraulic pumps 3 and 4 is sent to the front shaft traveling motor 8 and the rear shaft traveling motor 9, and the front shaft traveling motor 8 and the rear shaft traveling motor 9 are rotated to travel the vehicle. .

(Features of fluid pressure circuit of wheel type crane of this embodiment)
As described above, the hydraulic circuit of the wheel crane according to the present embodiment includes the telescopic cylinder 10 and the hoisting cylinder 11, the front shaft traveling motor 8, the hydraulic pump 3, and the switching valve 12. The main winding motor 74 and the auxiliary winding motor 75, the rear shaft traveling motor 9, the hydraulic pump 4, and the switching valve 13 are provided.

  The switching valve 12 is disposed between the hydraulic pump 3 and the working hydraulic cylinder (the expansion / contraction cylinder 10 and the hoisting cylinder 11) and between the hydraulic pump 3 and the front shaft travel motor 8. The switching valve 12 can supply pressure oil from the hydraulic pump 3 to the first and second cylinders 10 and 11 and the first position 12a where the pressure oil from the hydraulic pump 3 can be supplied to the front shaft traveling motor 8. The second position 12b and the pressure oil from the hydraulic pump 3 are supplied to the front shaft traveling motor 8, and the hydraulic oil returning from the front shaft traveling motor 8 to the switching valve 12 is supplied to the telescopic cylinder 10 and the undulating cylinder 11. It is possible to switch to a third position 12c that is possible (the pressure oil from the hydraulic pump 3 can be supplied to the front shaft traveling motor 8 and the telescopic cylinder 10 and the hoisting cylinder 11 simultaneously).

  The switching valve 13 is disposed between the hydraulic pump 4 and the working hydraulic motor (main winding motor 74, auxiliary winding motor 75) and between the hydraulic pump 4 and the rear shaft traveling motor 9. Yes. The switching valve 13 can supply pressure oil from the hydraulic pump 4 to the main winding motor 74 and the auxiliary winding motor 75, and can supply pressure oil from the hydraulic pump 4 to the rear shaft traveling motor 9. The second position 13b and the pressure oil from the hydraulic pump 4 are supplied to the rear shaft travel motor 9 and the hydraulic oil returning from the rear shaft travel motor 9 to the switching valve 13 is supplied to the main winding motor 74 and the auxiliary winding motor 75. It is possible to switch to the third position 13c that is possible (the pressure oil from the hydraulic pump 4 can be supplied to the rear shaft traveling motor 9, the main winding motor 74, and the auxiliary winding motor 75 simultaneously).

  According to this configuration, by switching the switching valve 12, hydraulic oil supplied by one hydraulic pump 3 can be supplied to the expansion / contraction cylinder 10, the undulation cylinder 11, and the front shaft traveling motor 8. The expansion / contraction cylinder 10 and the undulation cylinder 11 and the front shaft traveling motor 8 can be driven by the hydraulic pump 3. Further, by switching the switching valve 13, hydraulic oil supplied by one hydraulic pump 4 can be supplied to the main winding motor 74, the auxiliary winding motor 75 and the rear shaft traveling motor 9. Thus, the main winding motor 74 and the auxiliary winding motor 75 and the rear shaft driving motor 9 can be driven. Therefore, the number of pumps can be reduced and the structure of the hydraulic circuit can be simplified. Moreover, the structure of the gear box 2 which transmits motive power to a pump can be simplified by reduction of the number of pumps. In addition, since the pressure oil is supplied to the work system and the traveling system by one pump, there is no pump that idles like a conventional hydraulic circuit. Thereby, fuel consumption reduction can be aimed at. Furthermore, the cost can be reduced by reducing the number of pumps and simplifying the structure of the hydraulic circuit.

  The switching valves 12 and 13 are three-position switching valves.

  By using a three-position switching valve as the switching valves 12 and 13 as in this configuration, the above-described characteristics can be obtained.

  An impeller centrifugal pump 19 is connected to the hydraulic oil suction side of the hydraulic pumps 3 and 4.

  According to this configuration, by supplying hydraulic oil to the hydraulic oil suction side of the hydraulic pumps 3 and 4 by the impeller centrifugal pump 19, it is possible to suppress a decrease in hydraulic pressure on the hydraulic fluid suction side of the hydraulic pumps 3 and 4. Therefore, cavitation can be prevented.

(Second Embodiment)
FIG. 3 shows a hydraulic circuit according to the second embodiment. The main differences between the first embodiment and the second embodiment are the following two points.
In the first embodiment shown in FIG. 1, the three-position switching valves 12 and 13 are used to switch from the first state to the third state. On the other hand, in 2nd Embodiment shown in FIG. 3, it switches from a 1st state to a 3rd state using the switching means 112 and the switching means 113. FIG.
In the first embodiment, as shown in FIG. 1, the drive shaft of the impeller centrifugal pump 19 is directly connected to the drive shafts of the hydraulic pumps 3 and 4. On the other hand, in the second embodiment shown in FIG. 3, the drive shaft of the impeller centrifugal pump 19 is connected to the drive shafts of the hydraulic pump 3 and 4 via a clutch 119a.
Hereinafter, the difference will be described with reference to FIG. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

  The switching means 112 can switch from the first state to the third state (the switching operation will be described later). This switching means 112 is provided between an on-off valve 112 a (first on-off valve) provided between the telescopic cylinder 10 and the hoisting cylinder 11 and the hydraulic pump 3, and between the front shaft traveling motor 8 and the hydraulic pump 3. And an on-off valve 112b (second on-off valve) provided. Here, the on-off valve is a valve that can be switched between a state in which the valve is open, a state in which the valve is closed, and an intermediate state (state in which the valve is throttled). Specifically, it is a poppet type logic valve described below, for example.

  The on-off valve 112a (first on-off valve) and the on-off valve 112b (second on-off valve) are poppet valves (valves in which the valve element moves perpendicularly to the valve seat) (poppet type logic valves). This poppet valve has less pressure loss than the spool valve and can improve the efficiency of the hydraulic circuit. The on-off valve 112a and the on-off valve 112b can adjust the load by reducing the valve opening. Specifically, the valve opening degree of the valve can be reduced by adjusting the pressure for pressing the valve body against the valve seat using a proportional valve or the like.

  The switching means 113 can switch from the first state to the third state (the switching operation will be described later). This switching means 113 is provided between an on-off valve 113 a (first on-off valve) provided between the main winding motor 74 and auxiliary winding motor 75 and the hydraulic pump 4, and between the rear shaft traveling motor 9 and the hydraulic pump 4. And an on-off valve 113b (second on-off valve) provided.

  Since the on-off valve 113a (first on-off valve) and the on-off valve 113b (second on-off valve) have the same functions as the on-off valve 112a and on-off valve 112b, detailed description thereof is omitted.

  The clutch 119a is provided to rotate and stop the impeller centrifugal pump 19. That is, the drive shaft of the impeller centrifugal pump 19 is connected to the drive shafts of the hydraulic pumps 3 and 4 via the clutch 119a. When the clutch 119a is in the separated state, the impeller centrifugal pump 19 stops rotating. As a result, it is possible to suppress power loss when the impeller centrifugal pump 19 is rotated (idling) (in what case the clutch 119a is coupled and separated will be described later). The clutch 119a may be any of a hydraulic wet type, an electromagnetic type, or a dry type.

  The hydraulic circuit according to the second embodiment includes a gear pump 73 unlike the first embodiment shown in FIG. As with the conventional hydraulic circuit shown in FIG. 6, the gear pump 73 is a pump that supplies hydraulic oil to the hydraulic circuit.

(Operation of on-off valve and clutch)
Next, operations of the switching means 112 and 113 and the clutch 119a shown in FIG. 3 will be described. Specifically, the case where the switching means 112 and 113 are switched to the second state will be described first, the case where the switching means 112 is switched to the first state and the third state will be described, and then the switching means 113 is set to the first state. The case of switching to the state and the third state will be described.

  First, the case where the switching means 112 and 113 are set to the second state will be described. That is, a case where hydraulic oil from the hydraulic pump 3 is supplied only to the front shaft traveling motor 8 and a case where hydraulic fluid from the hydraulic pump 4 is supplied only to the rear shaft traveling motor 9 will be described. As for the switching means 112, the on-off valve 112b is opened and the on-off valve 112a is closed. As for the switching means 113, the on-off valve 113b is opened and the on-off valve 113a is closed. Furthermore, the rotation of the impeller centrifugal pump 19 is stopped with the clutch 119a in the separated state.

  The clutch 119a is brought into the separated state for the following reason. The circuit of the traveling system constitutes a closed circuit. That is, the hydraulic oil supplied from the oil passage 32 to the front shaft traveling motor 8 returns to the suction side port 3b of the hydraulic pump 3 through the oil passages 33 and 31 without substantially leaking. Further, the hydraulic oil supplied from the oil passage 42 to the rear shaft traveling motor 9 returns to the suction side port of the hydraulic pump 4 through the oil passages 43 and 41 without substantially leaking. Therefore, the hydraulic pressure on the hydraulic oil suction side of the hydraulic pump 3 or 4 is sufficiently high. Therefore, there is no need to prevent cavitation by supplying hydraulic oil to the hydraulic oil suction side of the hydraulic pump 3 or 4 by the impeller centrifugal pump 19. Therefore, the rotation of the impeller centrifugal pump 19 is stopped with the clutch 119a in the separated state.

  Next, the case where the switching means 112 is switched to the first state will be described. That is, a case where hydraulic oil from the hydraulic pump 3 is supplied only to the undulation / extension switching valve 24 will be described. In this case, the on-off valve 112a is opened and the on-off valve 112b is closed. Further, the clutch 119 a is in a coupled state, and the impeller centrifugal pump 19 supplies pressure oil to the hydraulic oil suction side port 3 b of the pump 3. Note that, unlike the travel system circuit described above, the work system circuit is an open circuit (the hydraulic oil returns to the tank T through the return oil passage 61). Therefore, the impeller centrifugal pump 19 supplies pressure oil to the hydraulic oil suction side port 3b of the hydraulic pump 3 to prevent cavitation.

  Next, the case where the switching means 112 is switched to the third state will be described. That is, a case where hydraulic oil from the hydraulic pump 3 is simultaneously supplied to the front shaft traveling motor 8 and the undulation / extension switching valve 24 will be described. In this case, both the on-off valves 112a and 112b are opened. Further, the clutch 119a is in a coupled state.

  At this time, control is performed to throttle the low-pressure side valve opening degree of the on-off valves 112a and 112b. More specifically, the following control is performed. The load pressure on the telescopic cylinder 10 and hoisting cylinder 11 side (working side) and the load pressure on the front shaft traveling motor 8 side (traveling side) are detected by a pressure sensor or the like. Then, control is performed to reduce the valve opening degree of the on-off valve connected to the low pressure side actuator on the work side and the traveling side (adding effective pressure loss). More preferably, the control is performed so that the sum of the load pressure of the low-pressure side actuator and the effective pressure loss of the on-off valve with the valve opening reduced is equal to the load pressure of the high-pressure side actuator. Thereby, a high load can be applied to the actuator on the high pressure side. On the other hand, if this control is not performed, since the on-off valves 112a and 112b are connected via the oil passage 30, the load pressure of the high-pressure side actuator will drop to the load pressure of the low-pressure side actuator.

More specifically, for example, when traveling at a slow speed by picking and carrying a suspended load (pick & carry), the front shaft traveling motor 8 side is more than the load pressure on the telescopic cylinder 10 and undulating cylinder 11 side. The load pressure is low. Therefore, by reducing the opening degree of the on-off valve 112b, a high load pressure can be applied to the expansion cylinder 10 and the undulation cylinder 11 side, and the speed of these cylinders does not slow down.
In order to travel without slowing down the speed of the work side actuator (the telescopic cylinder 10 and the hoisting cylinder 11), the on-off valve 112b is closed (the switching means 112 is in the first state) and the front shaft travel motor You may make it drive | work only with the rear-axis drive motor 9 by making the inclination angle of 8 side into zero.

  Next, the case where the switching means 113 is switched to the first state will be described. That is, a case where hydraulic oil from the hydraulic pump 4 is supplied only to the main / auxiliary switching valve 25 will be described. In this case, the on-off valve 113a is opened and the on-off valve 113b is closed. Further, the clutch 119a is engaged, and the impeller centrifugal pump 19 supplies pressure oil to the hydraulic oil suction side of the hydraulic pump 4.

  Next, the case where the switching means 113 is switched to the third state will be described. That is, the case where the hydraulic oil from the hydraulic pump 4 is supplied to the rear shaft traveling motor 9 and the main / auxiliary switching valve 25 at the same time will be described. In this case, both the on-off valves 113a and 113b are opened. Further, the clutch 119a is in a coupled state. Further, similarly to the case where the switching means 112 is switched to the third state, control is performed to reduce the valve opening degree of the on-off valve connected to the low load pressure side actuator. In order to travel without slowing down the speed of the work side actuator (main winding motor 74 or auxiliary winding motor 75), the on-off valve 113b is closed (the switching means 113 is set to the first state) and the rear shaft traveling motor. You may make it drive | work only with the front shaft drive motor 8 by making the inclination angle of 9 side into zero.

(Features of fluid pressure circuit of wheel type crane of this embodiment)
As described above, the hydraulic circuit of the wheel crane according to the present embodiment has the following characteristics.

The hydraulic circuit according to the present embodiment includes an on-off valve 112a provided on the expansion / contraction cylinder 10 and undulation cylinder 11 side, and an on-off valve 112b provided on the front shaft travel motor 8 side. Therefore, when hydraulic fluid is supplied simultaneously to at least one of the expansion cylinder 10 and the hoisting cylinder 11 (working hydraulic actuator) and the front shaft traveling motor 8 (traveling hydraulic actuator) (in the third state) In the case where one of the above two types of actuators (working and traveling) has a low load, only the on-off valve provided on the low-load actuator side (either on-off valve 112a or 112b) (Only one) can be throttled (effective pressure loss is added).
The hydraulic circuit according to the present embodiment includes an on-off valve 113a provided on the main winding motor 74 and auxiliary winding motor 75 side, and an on-off valve 113b provided on the rear shaft travel motor 9 side. Therefore, when hydraulic oil is supplied simultaneously to at least one of the main winding motor 74 and the auxiliary winding motor 75 (working hydraulic actuator) and the rear shaft traveling motor 9 (traveling hydraulic actuator) (in the third state) In the case where one of the above two types of actuators (working and traveling) has a low load, only the on-off valve provided on the low-load actuator side (either on-off valve 113a or 113b) (Only one) can be throttled (effective pressure loss is added).
Therefore, when the load on one of the two types of actuators (working and traveling) is low, a high load can be applied to the other actuator.

  Moreover, since the on-off valve 112a and the on-off valve 112b are poppet valves, there is less pressure loss than the spool valve. Therefore, the hydraulic circuit is more efficient than the case where the on-off valve 112a and the on-off valve 112b are spool valves. The on-off valve 113a and the on-off valve 113b have similar characteristics.

  The drive shaft of the impeller centrifugal pump 19 is connected to the drive shafts of the hydraulic pumps 3 and 4 via the clutch 119a. Therefore, when there is no need to suppress a decrease in hydraulic pressure on the hydraulic oil suction side of the hydraulic pump 3 or 4, the rotation of the impeller centrifugal pump 19 can be stopped by bringing the clutch 119a into a separated state. Therefore, the idling power of the impeller centrifugal pump 19 can be reduced, and deterioration of fuel consumption can be suppressed.

(Third embodiment)
FIG. 4 shows a hydraulic circuit according to the third embodiment. The differences between the second embodiment and the third embodiment are the following two points.
In the second embodiment shown in FIG. 3, the hydraulic oil discharged from the main winding / auxiliary switching valve 25 returns to the tank T through the return oil passage 61. On the other hand, in the third embodiment shown in FIG. 4, a back pressure check valve 264 is installed in the return oil passage 61, and an oil passage that connects the main winding / auxiliary winding switching valve 25 and the hydraulic oil suction side of the hydraulic pump 4. 261 is added.
In the second embodiment shown in FIG. 3, pressure oil is supplied from the impeller centrifugal pump 19 to the hydraulic pump 4. On the other hand, in the third embodiment shown in FIG. 4, no pressure oil is supplied from the impeller centrifugal pump 19 to the hydraulic pump 4.
Hereinafter, the difference will be described with reference to FIG. Since other configurations are the same as those of the second embodiment, the same reference numerals are given (or the reference numerals are appropriately omitted to avoid complication), and the description thereof is omitted.

  As described above, the back pressure check valve 264 is installed in the return oil passage 61 that connects the main winding / auxiliary switching valve 25 and the tank T, and the main winding / auxiliary switching valve 25 and the hydraulic pump 4. An oil passage 261 connecting the hydraulic oil suction side is formed. As a result, most of the hydraulic oil discharged from the main / auxiliary winding switching valve 25 does not pass through the return oil passage 61 but returns to the hydraulic oil suction side of the hydraulic pump 4 through the oil passage 261 and the oil passage 261a. It is. The hydraulic oil is also supplied to the hydraulic pump 4 from a small capacity gear pump 73a. Therefore, cavitation of the hydraulic pump 4 is prevented.

Further, since cavitation of the hydraulic pump 4 is prevented in this way, it is not necessary to supply hydraulic oil to the hydraulic oil suction side of the hydraulic pump 4 by the impeller centrifugal pump 19. Therefore, an oil passage for communicating the impeller centrifugal pump 19 and the hydraulic pump 4 is not provided.
Thereby, the capacity | capacitance of the impeller type centrifugal pump 19 can be made small compared with the case where hydraulic fluid is supplied to the hydraulic pumps 3 and 4 by the impeller type centrifugal pump 19.

The gear pump 73a is intended to replenish hydraulic fluid to the HST travel circuit (a circuit that drives the rear shaft travel motor 9 using the hydraulic pump 4 as a hydraulic source), and prevents cavitation of the hydraulic pump 4 during single travel operation. To help.
Further, no back pressure check valve is installed in the return oil passage 61a between the undulation / extension switching valve 24 and the tank T. This is due to the following reason. That is, during the cylinder extension operation of the telescopic cylinder 10 and the hoisting cylinder 11, the hydraulic oil discharged from the rod side (rod chambers 10b, 11b side) is the head side (bottom chambers 10a, 11a side), and the hydraulic pump 3 The amount of oil is greatly reduced compared to the hydraulic oil supplied to the discharge side. Therefore, a sufficient amount of pressure oil cannot be supplied to the hydraulic pump 3 by oil supply using the back pressure check valve described above. Therefore, pressure oil is supplied to the hydraulic pump 3 by the impeller centrifugal pump 19.

(Fourth embodiment)
FIG. 5 shows a hydraulic circuit according to the fourth embodiment. In the third embodiment shown in FIG. 4, the impeller centrifugal pump 19 is driven by the prime mover 1 (first prime mover). On the other hand, in the fourth embodiment shown in FIG. 5, the impeller centrifugal pump 19 is driven by an electric motor 301 (second prime mover).
Hereinafter, the difference will be described with reference to FIG. Since other configurations are the same as those in the third embodiment, the same reference numerals are given (or the reference numerals are omitted as appropriate to avoid complications), and the description thereof is omitted.

  The electric motor 301 (second prime mover) is a prime mover that drives the impeller centrifugal pump 19. By turning on / off the electric motor 301, it is possible to provide the same function as that of coupling / separating the clutch 119a according to the third embodiment shown in FIG. Further, as shown in FIG. 5, the electric motor 301 is arranged at a position shifted from the axes of the hydraulic pumps 3 and 4. Therefore, the axial length can be reduced as compared with the case where the hydraulic pumps 3 and 4 and the impeller centrifugal pump 19 are arranged on one shaft.

(Features of fluid pressure circuit of wheel type crane of this embodiment)
In the hydraulic circuit according to the present embodiment, an electric motor 301 that drives the impeller centrifugal pump 19 is provided separately from the prime mover 1 that drives the hydraulic pumps 3 and 4, so that the impeller centrifugal is provided on the shafts of the hydraulic pumps 3 and 4. There is no need to install the pump 19. Therefore, the arrangement of the impeller centrifugal pump 19 is facilitated, and the degree of freedom in designing the overall layout can be obtained.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

  For example, in 2nd Embodiment-4th Embodiment shown in FIGS. 3-5, the poppet valve was used for on-off valve 112a, 112b, 113a, and 113b. However, if the valve has two ports, one input and one output, and can be switched to a position where the valve opens, a position where the valve closes, and an intermediate position (position where the valve is throttled), a poppet The present invention can be applied even if it is not a valve.

1 prime mover (first prime mover)
2 Gearbox 3, 4 Hydraulic pump (fluid pressure pump)
8 Front shaft travel motor (travel fluid pressure actuator)
9 Rear shaft motor (travel hydraulic actuator)
10 Cylinder for expansion and contraction (working fluid pressure actuator)
11 Rolling cylinder (working fluid pressure actuator)
12, 13 Switching valve (switching means)
19 Impeller Centrifugal Pump 22 Electromagnetic Switching Valves 23a, 23b, 23c, 23d Proportional Valves 24 Relief / Extension Switching Valves 25 Main Winding / Auxiliary Winding Switching Valves 28 Pilot Pressure Source 74 Main Winding Motor (Working Fluid Pressure Actuator)
75 Supplementary winding motor (working fluid pressure actuator)
112, 113 switching means 112a, 113a On-off valve (first on-off valve)
112b, 113b On-off valve (second on-off valve)
119a Clutch 301 Electric motor (second prime mover)
A1, A2 Pump circuit B1, B2 Motor circuit T Tank

Claims (7)

A working fluid pressure actuator;
A fluid pressure actuator for traveling;
A fluid pressure pump capable of supplying a working fluid to the working fluid pressure actuator and the traveling fluid pressure actuator;
Switching means provided between the working fluid pressure actuator and the traveling fluid pressure actuator and the fluid pressure pump;
The switching means has a first state in which the working fluid from the fluid pressure pump can be supplied to the working fluid pressure actuator, and a second state in which the working fluid from the fluid pressure pump can be supplied to the traveling fluid pressure actuator. And a third state in which the working fluid from the fluid pressure pump can be simultaneously supplied to the traveling fluid pressure actuator and the working fluid pressure actuator. Pressure circuit.   The switching means includes a first opening / closing valve provided between the working fluid pressure actuator and the fluid pressure pump, and a second opening / closing valve provided between the traveling fluid pressure actuator and the fluid pressure pump. The fluid pressure circuit of the wheel type crane according to claim 1, further comprising a valve.   The fluid pressure circuit of the wheel type crane according to claim 2, wherein the first on-off valve and the second on-off valve are poppet valves.   The switching means is a three-position switching valve, a first switching position capable of supplying the working fluid from the fluid pressure pump to the working fluid pressure actuator, and the working fluid from the fluid pressure pump as the traveling fluid. A second switching position that can be supplied to the pressure actuator, and a working fluid that supplies the working fluid from the fluid pressure pump to the traveling fluid pressure actuator and returns from the traveling fluid pressure actuator to the switching valve. The fluid pressure circuit of the wheel type crane according to claim 1, wherein the fluid pressure circuit can be switched to a third switching position that can be supplied to the fluid pressure actuator.   The fluid pressure circuit of the wheel type crane according to any one of claims 1 to 4, wherein an impeller centrifugal pump is connected to a working fluid suction side of the fluid pressure pump.   6. The fluid pressure circuit of the wheel type crane according to claim 5, wherein a drive shaft of the impeller centrifugal pump is connected to a drive shaft of the fluid pressure pump through a clutch.   The fluid pressure of the wheel type crane according to any one of claims 1 to 5, comprising a first prime mover for driving the fluid pressure pump and a second prime mover for driving the impeller centrifugal pump. circuit.

Images