JP2017145960A - Control device of hydraulic travel apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promptly and accurately control to reduce a variable capacity of a hydraulic pump in response to an increase in a traveling load or the like, and to accurately prevent an engine stall. SOLUTION: A travel control device is rotationally driven by a variable displacement type hydraulic pumps 31 and 41 driven by an engine EG, hydraulic motors 32 and 42 driven by oil discharged from the hydraulic pump, and a hydraulic motor. To operate the traveling devices 5 and 5, the traveling operation lever 52 operated to instruct traveling, the first control valve 62 that regulates the discharge oil of the charge pump 61 to generate charge hydraulic pressure, and the traveling operation lever. A second control valve 65 is provided to generate the corresponding capacity control hydraulic pressure. The first control valve is configured to regulate and generate charge hydraulic pressure according to the rotation speed of the engine, and the hydraulic pump is subjected to variable capacity control by the capacity control hydraulic pressure generated by pressure regulation by the second control valve. [Selection diagram] Fig. 4

Description

  The present invention relates to a control device for a working vehicle having an engine-driven hydraulic travel device.

As an example of such a working vehicle, a skid is provided that has a traveling device provided with tires or crawlers on the left and right sides of the vehicle body, and changes the traveling direction by varying the operating speed of the tires or crawlers by the left and right traveling devices. A steer loader is known (see, for example, Patent Document 1). The skid steer loader is generally configured such that an engine for driving a traveling device or the like is mounted on the rear portion of the vehicle body, and the traveling device is driven using the engine driving force. In this case, as a traveling device, a configuration in which a hydraulic pump is driven by an engine and a tire or a crawler is driven by a hydraulic motor that is driven by the supply of oil discharged from the hydraulic pump, so-called HST (Hydro-Static Transmission).
Is used.

  In HST, a variable displacement type hydraulic pump is used, and traveling speed control is performed by variable displacement control of the hydraulic pump. At this time, variable displacement control of the hydraulic pump is performed using the discharge hydraulic pressure (charge hydraulic pressure) of the charge pump driven by the engine. When the work vehicle is traveling using such a traveling apparatus of HST, when the traveling load increases and the engine load increases, the engine rotation is decreased and the discharge amount of the charge pump is decreased. When the charge oil pressure decreases, the variable discharge capacity of the hydraulic pump controlled using the charge oil pressure decreases, thereby reducing the engine load and preventing engine stall.

Japanese Patent No. 5226569

  However, the control to reduce the variable discharge capacity of the hydraulic pump due to the decrease in charge oil pressure has different control characteristics due to the difference in oil viscosity due to the difference in oil temperature. There is a problem that it may not be done. In addition, when the traveling load increases rapidly, there is a problem that the engine stall prevention control may not be performed accurately due to a delay in response of the hydraulic pump capacity reduction control due to the decrease in the charge hydraulic pressure accompanying the decrease in engine rotation. There is also.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a control device that can accurately prevent engine stall against an increase in travel load.

In order to achieve the above object, a control device for a hydraulic traveling device according to the present invention includes an engine, a variable displacement hydraulic pump driven to rotate by the engine, and a hydraulic pressure driven by oil discharged from the hydraulic pump. A motor, a travel device that is rotationally driven by the hydraulic motor, a travel operation device that is operated to instruct travel by the travel device, a charge pump, and a charge hydraulic pressure that is adjusted by adjusting discharge oil of the charge pump. A first control valve to be generated;
And a second control valve that adjusts the charge hydraulic pressure in accordance with the operation of the travel operation device and generates a displacement control hydraulic pressure in accordance with the operation of the travel operation device. The first control valve is configured to generate the charge hydraulic pressure in accordance with the rotational speed of the engine, and the hydraulic pump is variable according to a displacement control hydraulic pressure generated by the second control valve. Capacity control is performed.

  In the control device having the above configuration, preferably, an accelerator operation device operated to instruct engine drive, an engine control device that performs drive control of the engine in accordance with an operation of the accelerator operation device, and the accelerator operation device A target engine speed setting device that sets a target engine speed according to the operation of the engine, and an engine speed detector that detects the engine speed, and an actual engine speed detected by the engine speed detector, The first control valve adjusts and generates the charge hydraulic pressure so as to reduce the difference from the target engine speed set by the target engine speed setting device.

  Further, in the control device having the above configuration, preferably, the first control valve adjusts and generates the charge hydraulic pressure by PID control so as to reduce a difference between the actual engine rotation speed and the target engine rotation speed.

  Further, in the control device having the above configuration, preferably, a hydraulic actuator that is operated by a hydraulic actuator, a main pump for supplying hydraulic oil to be supplied to the hydraulic actuator, and discharge oil of the main pump is used as the hydraulic actuator. A hydraulic pilot-type operation control valve that performs control to be supplied to the hydraulic control device, an operation operation device that is operated to instruct operation of the hydraulic operation device, and operation of the operation control valve according to operation of the operation operation device. And a third control valve that performs control to supply a pilot pressure for control to the operation control valve. In addition, the third control valve is configured to adjust the charge hydraulic pressure generated by the first control valve to generate the pilot pressure, and the operation control from the third control valve. A pilot detector for detecting that the pilot pressure is supplied to the valve; and when the pilot detector detects that the pilot pressure is supplied to the operation control valve, the target engine speed is adjusted. Reduce.

  According to the control device for a hydraulic traveling device according to the present invention configured as described above, the variable displacement control is performed by the displacement control oil pressure set by the second control valve in the hydraulic pump. At this time, the valve control device controls the operation of the first control valve in accordance with the rotational speed of the engine and sets the charge hydraulic pressure to a hydraulic pressure in accordance with the engine rotational speed. Sometimes, the charge hydraulic pressure can be quickly and accurately lowered to lower the capacity control hydraulic pressure. Thereby, the capacity | capacitance of a hydraulic pump can be reduced rapidly and exactly, and the engine stall at the time of increase in driving | running | working load etc. can be prevented exactly.

  In the control device according to the present invention, the first control valve is configured so as to reduce a difference between the actual engine rotation speed detected by the engine speed detector and the target engine rotation speed set by the target engine rotation setting device. Is preferably configured to regulate the charge hydraulic pressure. As a result, it is possible to accurately prevent engine stall when the travel load or the like increases only by simple control based on the engine rotation speed.

  Furthermore, in the control device according to the present invention, the first control valve is configured to adjust the capacity control hydraulic pressure by PID control so as to reduce the difference between the actual engine speed and the target engine speed. Is preferred. As a result, more accurate travel control and engine stall prevention control can be performed.

  Further, the control device according to the present invention includes a hydraulic actuator that is operated by a hydraulic actuator, a main pump that supplies hydraulic oil to be supplied to the hydraulic actuator, and discharge oil of the main pump that is used as the hydraulic actuator. A hydraulic pilot-type operation control valve that performs control to be supplied to the hydraulic control device, an operation operation device that is operated to instruct operation of the hydraulic operation device, and operation of the operation control valve according to operation of the operation operation device. It is preferable to include a third control valve that performs control to supply pilot pressure for control to the operation control valve. In this configuration, the third control valve is configured to adjust the charge hydraulic pressure generated by the first control valve to generate the pilot pressure, and the third control valve operates from the third control valve. A pilot detector for detecting that the pilot pressure is supplied to the control valve; and when the pilot detector detects that the pilot pressure is supplied to the operation control valve, the target engine speed Is preferably reduced. In this way, the target engine speed is reduced when the operating device is operated while the charge hydraulic pressure is being lowered to prevent stall when the traveling load or the like is increased. Accordingly, the charge hydraulic pressure is increased, and the lowered pilot pressure is increased to ensure the operation of the operation control valve, and the engine stall can be prevented.

It is a left view which shows the crawler type skid steer loader provided with the control apparatus which concerns on this invention in the state by which the arm was rock | fluctuated to the lowest position. It is a figure which shows the said skid steer loader, (a) is a top view, (b) is a front view. It is a left view which shows the said skid steer loader in the state which rock | fluctuated the arm to the most moved position. It is a hydraulic circuit diagram which shows the structure of the said control apparatus. It is a time chart which shows the control content by the said control apparatus. It is a hydraulic circuit diagram which shows the structure of the control apparatus which concerns on another embodiment of this invention. It is a time chart which shows the control content by the control apparatus which concerns on the said another embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, an example in which the present invention is applied to a crawler skid steer loader (hereinafter referred to as a crawler loader) in which a bucket is attached to the tip of an arm will be described. First, the overall configuration of the crawler loader 1 will be described with reference to FIGS.

  1 to 3, the crawler loader 1 includes a pair of left and right traveling devices 5 and 5 each having an endless crawler belt 3, and a main body on which the traveling devices 5 and 5 are attached to the left and right. The frame 9 includes a loader device 20 attached to the main body frame 9, and an operator cabin 11 provided at the upper center of the main body frame 9. The traveling devices 5 and 5 and the main body frame 9 are collectively referred to as “vehicle 10” hereinafter.

  The operator cabin 11 is formed in a box shape, and the front side of the vehicle is opened, and a front door 11a that can be opened and closed is provided at the opening. In the operator cabin 11, an operator seat (not shown) on which an operator sits facing the front side of the vehicle is provided, and traveling for operating the driving devices 5 and 5 on the left and right of the operator seat. An operation lever 52 (see FIG. 4) and a loader operation lever (not shown, but corresponding to the arm operation lever 78 shown in FIG. 6) for driving the loader device 20 are provided.

  As described above, the loader device 20 is attached to the main body frame 9. The main body frame 9 is provided with a plurality of pivot points for attaching the loader device 20. The loader device 20 includes an arm 21 disposed so as to surround the front, rear, left and right of the operator cabin 11, a pair of left and right control links 22 attached across the main body frame 9 and the arm 21, and a rear side of the control link 22. A pair of left and right arm cylinders 23 attached across the body frame 9 and the arm 21, a pair of left and right lift links 24 attached across the body frame 9 and the arm 21 on the rear side of the arm cylinder 23, It is comprised from the bucket 29 attached to the front-end part via the bracket 29a. The pair of left and right control links 22, arm cylinder 23 and lift link 24 are provided symmetrically, and the arm 21 is attached to the main body frame 9 via the control link 22, arm cylinder 23 and lift link 24.

  The bracket 29a is pivotally connected to the tip of the arm 21 so as to be swingable up and down, and the bucket 29 is detachably attached to the bracket 29a. The bucket 29 (bracket 29 a) is swung up and down with respect to the arm 21 by operating the bucket cylinders 28, 28 provided on the distal end side of the arm 21 to expand and contract.

  The crawler loader 1 is configured such that the operator sits on the operator seat and operates the travel operation lever and the loader operation lever to drive the travel device 5 and travel the vehicle 10 according to the operation of each operation lever. The arm cylinder 23 can be expanded and contracted to swing the arm 21 up and down, and the bucket cylinder 28 can be expanded and contracted to swing the bucket 29 up and down. In this case, the arm 21 can be swung up and down between the lowermost movement position 21D and the uppermost movement position 21U by extending and contracting the arm cylinder 23. As described above, the arm cylinder 23 and the bucket cylinder 28 operate the loader device 20 in accordance with the operation of the loader operation lever. Hereinafter, the arm cylinder 23 and the bucket cylinder 28 are collectively referred to as a loader actuator.

  The crawler loader 1 is provided with a diesel engine EG (hereinafter referred to as an engine EG) at a rear position of the operator cabin 11 at the upper rear side of the main body frame 9. The traveling device 5, the arm cylinder 23, and the bucket cylinder 28 are configured to be driven by receiving hydraulic oil from a hydraulic pump driven by the engine EG. The left and right sides of the engine EG are covered by the side frames of the main body frame 9, and the upper and rear sides are covered by the engine cover 15 and the rear door 16, respectively. The engine cover 15 is provided so as to be openable and closable with respect to the main body frame 9 using a pair of left and right hinge mechanisms (not shown) provided at the front end.

The driving force of the engine EG is used to operate the arm cylinder 23 and the bucket cylinder 28 and is also transmitted to the left and right traveling devices 5 and 5 to be used for causing the vehicle 10 to travel. A configuration for causing the vehicle 10 to travel will be described with reference to the hydraulic circuit diagram of FIG. As shown in FIGS. 1 and 3, the left and right traveling devices 5, 5 each have a drive sprocket 5.
The crawler belts 3 and 3 are driven by rotating the drive sprockets 5a and 5b to cause the vehicle 10 to travel. These left and right drive sprockets 5a and 5b are driven to rotate by left and right hydraulic motors 32 and 42, respectively. That is, the traveling devices 5 and 5 are driven by the hydraulic motors 32 and 42.

As shown in FIG. 4, the hydraulic motors 32 and 42 constitute part of the left and right HST circuits 30 and 40. The HST circuit has the same configuration on the left and right, and the configuration will be described by taking the left HST circuit 30 as an example. In the left HST circuit 30, a left hydraulic motor 32 is connected to a left hydraulic pump 31 that is rotationally driven by an engine EG via oil passages 33a and 33b to form a hydraulic closed circuit. When the left hydraulic pump 31 is rotationally driven by the engine EG, the discharged oil is supplied to the left hydraulic motor 32 via, for example, an oil passage 33a and is rotationally driven. As a result, the left drive sprocket 5 a is rotationally driven by the left hydraulic motor 32 to drive the left crawler belt 3, and the vehicle 10 is driven by the left traveling device 5. The oil used to drive the left hydraulic motor 32 is returned to the left hydraulic pump 31 through the oil passage 33b.

  In the left HST circuit 30, the left hydraulic pump 31 in the oil passages 33a and 33b is a variable displacement pump, and its discharge capacity is variably controlled by the variable displacement control actuators 31a and 31b. This variable capacity control will be described later. The left hydraulic motor 32 is capable of switching the capacity in two stages of high and low, and is configured to perform two-stage capacity switching by controlling the hydraulic pressure supply to the capacity switching cylinder 35a by the speed switching valve 35. It has high pressure relief valves 34a and 34b for preventing the hydraulic pressure in the left HST circuit 30 from exceeding a predetermined pressure, and a flushing relief valve 39 for cooling the oil.

  Since the right HST circuit 40 has the same configuration as the left HST circuit 30, a simple description will be given while avoiding repeated explanation. In the right HST circuit 40, a variable displacement type right hydraulic pump 41 that is rotationally driven by the engine EG is connected to the right hydraulic motor 42 via oil passages 43a and 43b. When the right hydraulic pump 41 is rotationally driven by the engine EG, the right hydraulic motor 42 is rotationally driven by the supply of the discharged oil, and the right driving sprocket 5b is rotationally driven to drive the right crawler belt 3 to drive the right traveling device 5. Thus, the driving of the vehicle 10 is performed. The right hydraulic motor 42 can also switch the capacity in two steps. The right HST circuit 40 is also provided with high-pressure relief valves 44a and 44b and a flushing relief valve 49.

  As can be seen from the above description of the configuration, the left and right hydraulic pumps 31 and 41 are rotationally driven by the engine EG, and the discharged oil is sent to the left and right hydraulic motors 32 and 42 via the oil passages 33a, 33b, 43a, and 43b, respectively. These are driven to rotate. As a result, the left and right drive sprockets 5 a and 5 b are driven by the left and right hydraulic motors 32 and 42, and the traveling drive by the left and right traveling devices 5 and 5 is performed. High and low two-stage switching of the left and right hydraulic motors 32 and 42 is performed simultaneously, and either a high speed stage or a low speed stage is set. On the other hand, variable displacement control of the left and right hydraulic pumps 31 and 41 is performed independently, and the drive speeds of the left and right traveling devices 5 and 5 are controlled independently. If the left and right traveling devices 5 and 5 are driven in the same direction at the same speed, it is possible to perform straight traveling, and it is possible to perform steering that changes the traveling direction by making the left and right traveling speeds different.

  The travel control can be performed by performing the variable displacement control of the left and right hydraulic pumps 31 and 41 as described above. The travel control device 60 that performs the travel control will be described.

  The left and right hydraulic pumps 31, 41 are respectively provided with variable displacement control actuators 31a, 31b, 41a, 41b, and control the displacement control hydraulic pressure Pc supplied to these variable displacement control actuators 31a, 31b, 41a, 41b. Thus, the variable displacement control of the left and right hydraulic pumps 31 and 41 can be performed. Specifically, when the displacement control oil pressure Pc is low, the displacement of the hydraulic pumps 31, 41 is small, and as the displacement control oil pressure Pc increases, the displacement of the hydraulic pumps 31, 41 increases.

In order to obtain the capacity control hydraulic pressure Pc, a charge pump 61 that is rotationally driven by the engine EG is provided. The oil discharged from the charge pump 61 is sent to the first control valve 62 through the oil passage 61a, where the charge hydraulic pressure Pch is regulated. The oil having the charge hydraulic pressure Pch is sent to the second control valve 65 through the oil passage 62a. The second control valve 65 adjusts the charge hydraulic pressure Pch according to the operation of the travel operation lever 52 mechanically connected to the second control valve 65, and supplies it to the variable displacement control actuators 31a and 31b of the left hydraulic pump 31. The displacement control hydraulic pressure PcL and the variable displacement control actuators 41a, 4 of the right hydraulic pump 41
The right displacement control hydraulic pressure PcR supplied to 1b is generated. These displacement control hydraulic pressures PcL and PcR are supplied to variable displacement control actuators 31a, 31b, 41a and 41b through oil passages 66a, 66b, 67a and 67b, respectively, and variable displacement control of the left and right hydraulic pumps 31 and 41 is performed. It is like that. A high-pressure relief valve 69 is provided to prevent the hydraulic pressure in the oil passage 61a from exceeding a predetermined pressure, and a maximum hydraulic pressure that can be generated by the first control valve 62 is set by the high-pressure relief valve 69. Is done.

  The travel control device 60 configured as described above includes a controller 50 that controls the operation of the first control valve 62. The controller 50 is input with the actual rotational speed (Nea) information of the engine EG detected by the engine rotation sensor 51 through the signal line 51a, and the operation information (depression amount information) of the accelerator pedal 53 through the signal line 53a. The operation information of the accelerator operation dial 54 is input via the signal line 54a. Based on the input information, the controller 50 controls the operation of the first control valve 62 via the signal line 56 and controls the engine drive by an engine control device (not shown) via the signal line 58. The accelerator pedal 53 and the accelerator operation dial 54 are collectively referred to as an accelerator operation device.

  Control by the controller 50 will be described. When the operation information (depressing amount information) of the accelerator pedal 53 or the operation information of the accelerator operation dial 54 is input, a command signal is sent to the engine rotation control device so that the engine rotation corresponds to the accelerator operation amount, and engine drive control is performed. (Accelerator control or throttle control) is performed. A target engine speed (Neo) corresponding to the operation amount of the accelerator pedal 53 or the operation position of the accelerator operation dial 54 is set. The target engine speed (Neo) is a target value of engine rotation when a predetermined engine load is applied, and the driving operation lever 52 is not operated and the engine EG is not loaded by the control by the engine drive control. In this case, the idling speed is higher than the target engine speed (Neo). As can be seen from this, the controller 50 controls the engine EG according to the operation of the accelerator operating device, and sets the target engine speed (Neo) according to the operation of the accelerator operating device. An engine rotation setting device.

  When the travel operation lever 52 is operated, the second control valve 65 regulates and generates the capacity control hydraulic pressures PcL and PcR to be supplied to the variable displacement control actuators 31a, 31b, 41a and 41b according to the operation of the travel operation lever 52. The variable displacement control of the left and right hydraulic pumps 31 and 41 is performed. As a result, hydraulic pressure is supplied from the left and right hydraulic pumps 31 and 41 to the left and right hydraulic motors 32 and 42 according to the variable displacement control, and the hydraulic motors 32 and 42 are driven to rotate. Driven and the vehicle 10 travels according to the operation of the travel operation lever 52.

  When the left and right hydraulic pumps 31 and 41 are operated in this manner, the driving load acts on the engine EG, so that the engine rotation decreases according to the load. The change in the engine speed is transmitted to the controller 50, and the controller 50 controls the operation of the first control valve 62 so as to generate the charge hydraulic pressure Pch corresponding to the actual engine speed (Nea). At this time, for example, when the engine is in a predetermined throttle state, when the actual engine speed (Nea) matches the target engine speed (Neo), the capacity of the hydraulic pumps 31 and 41 is used to operate the travel operation lever 52. The controller 50 generates the charge hydraulic pressure Pch by the first control valve 62 so as to have a corresponding capacity. Specifically, the charge hydraulic pressure Pch is generated so that the capacity control hydraulic pressures PcL and PcR according to the operation of the travel operation lever 52 can be generated.

On the other hand, when the actual engine speed (Nea) falls below the target engine speed (Neo), the controller 50 reduces the charge hydraulic pressure Pch generated by the first control valve 62. As a result, the capacity control hydraulic pressures PcL and PcR generated by the second control valve 65 in response to the operation of the travel operation lever 52 are decreased to correspond to the decreased charge hydraulic pressure Pch, and the capacity of the hydraulic pumps 31 and 41 is decreased. To do. As a result, the driving load of the hydraulic pumps 31 and 41 by the engine decreases, and the engine rotation increases. Accordingly, control is performed to keep or bring the actual engine speed (Nea) to or close to the target engine speed (Neo) regardless of changes in engine load, that is, travel load, and engine stall can be reliably prevented.

  A specific example of the above-described control by the controller 50 will be described with reference to FIG. FIG. 5 shows the actual engine speed Nea (rpm), the engine drive torque TQe (%), and the energization current Asol (mA) of the solenoid used to control the charge hydraulic pressure Pch regulated by the first control valve 62. It is a graph which shows the change of this with time. The energization current Asol (mA) indicates the charge hydraulic pressure Pch.

  Here, the target engine speed (Neo) is set to 2400 rpm by the accelerator operation dial 54, and the traveling operation lever 52 is not operated until the time t1, and the traveling operation lever 52 is operated from the time t1. The case where the vehicle 10 is made to travel is shown. Since the traveling operation lever 52 is in the neutral position until time t1, the second control valve 65 is operated so that the capacity of the left and right hydraulic pumps 31, 41 is zero. As a result, the engine EG enters a no-load state, and the actual engine speed Nea is higher than the target engine speed Neo, for example, about 2750 rpm as shown in the figure. At this time, the energization current Asol of the solenoid used for the control of the charge hydraulic pressure Pch by the first control valve 62 is a high value of 1500 mA corresponding to the high engine speed, and the charge hydraulic pressure Pch is a high pressure. The capacity control hydraulic pressures PcL and PcR that are regulated by the control valve 65 are pressures that make the capacity of the left and right hydraulic pumps 31 and 41 zero.

  When the travel operation lever 52 is operated from time t1, the second control valve 65 adjusts and generates the capacity control hydraulic pressures PcL and PcR according to the operation of the travel operation lever 52. As a result, the capacity of the left and right hydraulic pumps 31 and 41 is set to a capacity corresponding to the operation of the operation lever 52, and the discharged oil is sent to the left and right hydraulic motors 32 and 42 to rotate them, and the left and right sprockets 5a. , 5b are rotationally driven to start traveling of the vehicle 10. At this time, a load for rotationally driving the left and right hydraulic pumps 31 and 41 acts on the engine EG, and the actual engine speed Nea decreases as shown in the figure as the load increases. At the same time, the engine driving torque TQe becomes an output corresponding to the pump driving load from the no-load state, and the energization current Asol of the solenoid used for controlling the charge hydraulic pressure Pch by the first control valve 62 decreases from 1500 mA to the actual engine speed Nea. Decreases depending on

  At time t2, the actual engine speed Nea matches the target engine speed Neo, and the energization current Asol of the solenoid at this time is 1250 mA. This energization current value is a target by which the charge hydraulic pressure Pch that is regulated by the first control valve 62 can be directly obtained by the capacity control hydraulic pressures PcL and PcR that are regulated by the second control valve 65 according to the operation of the operation lever 52 The charge oil pressure Pcho is set. From time t1 to time t2, since the actual engine speed Nea> the target engine speed Neo, the charge oil pressure Pch is higher than the target charge oil pressure Pcho.

Even after the time t2, the actual engine speed Nea continues to decrease due to the engine driving load, and accordingly, the energization current Asol of the solenoid also decreases. As a result, the charge hydraulic pressure Pch that is regulated by the first control valve 62 falls below the target charge hydraulic pressure Pcho, and the capacity control hydraulic pressure PcL that is regulated by the second control valve 65 according to the operation of the operation lever 52. PcR decreases. As a result, the capacity of the hydraulic pumps 31 and 41 is reduced, and the engine driving load is reduced. In this graph, the actual engine speed Nea decreases most at time t3, but thereafter gradually increases with a decrease in engine drive load, and gradually approaches the target engine speed Neo. When the engine speed reaches the target engine speed Neo, the hydraulic pump drive is balanced with the engine driving force. The pressure control of the charge hydraulic pressure Pch by the first control valve 62 at this time is performed by PID control based on the difference between the actual engine speed Nea and the target engine speed Neo. Thereby, it becomes the smooth pressure regulation according to a rotation difference.

  When the charge hydraulic pressure Pch is controlled by the first control valve 62 corresponding to the actual engine speed Nea as described above, the hydraulic pumps 31, 41 are controlled so that the actual engine speed Nea becomes the target engine speed Neo. The variable displacement control is performed, and the traveling control with respect to the fluctuation of the engine load can be performed quickly and accurately. As a result, even when the oil temperature is low or when the traveling load suddenly increases, it is possible to perform accurate traveling control and to reliably prevent engine stall.

  In the above description, the case where the hydraulic pumps 31 and 41 for driving are driven by the engine EG has been described. However, the engine EG is also used to drive a loader hydraulic pump (not shown) that supplies hydraulic oil to the arm cylinder 23 and bucket cylinder 28 for driving the loader device 20. When the arm cylinder 23 and the bucket cylinder 28 are also operated, in the above-described control, the engine load is the sum of the driving load of the loader hydraulic pump in addition to the travel driving load, and the actual engine speed with respect to the total load. Control is performed so that Nea is the target engine speed Neo.

Second embodiment:
In the above description, the travel control based on the operation of the travel operation lever 52 has been described. However, the crawler loader 1 also requires the operation control of the loader device 20 in accordance with the operation of the loader operation lever. Although it is possible to make this loader control independent of the above-described travel control, the travel control device and the loader control device are related in order to simplify the device configuration as much as possible and reduce costs. Hereinafter, as a second embodiment, an example of a control device configuration in which a travel control device and a loader control device are associated will be described with reference to FIG.

  The control device shown in FIG. 6 has a configuration in which a loader control device 70 is added to the traveling control device 60 substantially the same as that shown in FIG. For this reason, the same number and code | symbol are attached | subjected about the overlapping part in the structure of the traveling control apparatus 60. FIG. Hereinafter, the configuration of the control device of FIG. 6 will be described mainly with respect to the differences from the configuration shown in FIG. The configuration of the left and right HST circuits 30 and 40 that rotationally drive the drive sprockets 5a and 5b of the left and right traveling devices 5 and 5 is the same as that shown in FIG.

  The control device shown in FIG. 6 has the same travel control device 60 as that shown in FIG. 4, and this travel control device uses hydraulic pressure from the charge pump 61 driven by the engine EG. The control device further includes a main pump 71 that supplies hydraulic pressure for controlling the operation of the loader control device 70. The main pump 71 is also rotationally driven by the engine EG and supplies the discharged oil to the oil passage 71a. . Control to supply the hydraulic pressure supplied to the oil passage 71a to a loader actuator (in FIG. 6, exemplarily shows the arm cylinder 23) is performed by the loader control device 70, which will be described later. The travel control device 60 will be briefly described.

As described above, the discharge oil of the charge pump 61 that is rotationally driven by the engine EG is sent to the first control valve 62 through the oil passage 61a, where the charge hydraulic pressure Pch is regulated. The oil having the charge hydraulic pressure Pch is fed to the travel operation lever 52 by the second control valve 65.
The left displacement control hydraulic pressure PcL supplied to the variable displacement control actuators 31 a and 31 b of the left hydraulic pump 31 and the right displacement control hydraulic pressure supplied to the variable displacement control actuators 41 a and 41 b of the right hydraulic pump 41. PcR is generated. These displacement control oil pressures PcL and PcR are supplied to the variable displacement control actuators 31a, 31b, 41a and 41b, and variable displacement control of the left and right hydraulic pumps 31 and 41 is performed.

  The controller 50 receives the actual engine speed (Nea) information of the engine EG detected by the engine rotation sensor 51, the operation information (depression amount information) of the accelerator pedal 53, and the operation information of the accelerator operation dial 54. The controller 50 controls the operation of the first control valve 62 based on the input information, and further performs engine drive control by an engine control device (not shown) via the signal line 58. When operation information (depression amount information) of the accelerator pedal 53 or operation information of the accelerator operation dial 54 is input to the controller 50, a command signal is sent to the engine rotation control device so that the engine rotation according to the accelerator operation amount is performed. Perform engine drive control (accelerator control or throttle control). At the same time, the target engine speed (Neo) corresponding to the operation amount of the accelerator pedal 53 or the operation position of the accelerator operation dial 54 is set.

  When the travel operation lever 52 is operated, the second control valve 65 regulates and generates the capacity control hydraulic pressures PcL and PcR to be supplied to the variable displacement control actuators 31a, 31b, 41a and 41b according to the operation of the travel operation lever 52. The variable displacement control of the left and right hydraulic pumps 31 and 41 is performed. In accordance with this variable displacement control, hydraulic pressure is supplied from the left and right hydraulic pumps 31, 41 to the left and right hydraulic motors 32, 42, the hydraulic motors 32, 42 are driven to rotate, and the left and right traveling devices 5, 5 are driven. The vehicle 10 travels according to the operation of the travel operation lever 52.

  When the left and right hydraulic pumps 31 and 41 are operated in this manner, the driving load acts on the engine EG, so that the engine rotation decreases according to the load. The change in the engine speed is transmitted to the controller 50, and the controller 50 controls the operation of the first control valve 62 so as to generate the charge hydraulic pressure Pch corresponding to the actual engine speed (Nea). At this time, for example, when the engine is in a predetermined throttle state, when the actual engine speed (Nea) matches the target engine speed (Neo), the capacity of the hydraulic pumps 31 and 41 is used to operate the travel operation lever 52. The controller 50 generates the charge hydraulic pressure Pch by the first control valve 62 so as to have a corresponding capacity.

  When the actual engine speed (Nea) falls below the target engine speed (Neo), the controller 50 reduces the charge hydraulic pressure Pch generated by the first control valve 62. As a result, the capacity control hydraulic pressures PcL and PcR generated by the second control valve 65 in response to the operation of the travel operation lever 52 are decreased to correspond to the decreased charge hydraulic pressure Pch, and the capacity of the hydraulic pumps 31 and 41 is decreased. To do. As a result, the driving load of the hydraulic pumps 31 and 41 by the engine decreases, and the engine rotation increases. Thus, control is performed to maintain the engine speed at the target engine speed (Neo) regardless of changes in engine load, that is, travel load, and engine stall can be reliably prevented.

  Next, the operation control of the arm cylinder 23 (loader actuator) by the loader control device 70 will be described. As described above, the discharge oil of the main pump 71 driven by the engine EG is supplied to the oil passage 71a. A main pressure regulating valve 71c is provided in the oil passage 71a, and the oil pressure in the oil passage 71a is regulated to the line pressure PL. The oil passage 71a is connected to the arm control valve 73, and is selectively connected to the rod side port 23a or the bottom side port 23b of the arm cylinder 23 by the arm control valve 73. The arm control valve 73 is actuated by receiving a pilot pressure Pp supplied to pilot ports 73a and 73b located at its ends.

  For example, when the pilot pressure Pp is supplied to the pilot port 73a, the arm control valve 73 moves to the upward movement position, and connects the oil passage 71a to the rod side port 23a via the oil passage 72a. At the same time, the oil passage 72b connected to the bottom side port 23b is connected to the tank via the oil passage 71b. As a result, the oil having the line pressure PL in the oil passage 71a is supplied to the rod-side oil chamber of the arm cylinder 23 and presses in the direction in which the arm cylinder 23 is reduced. Accordingly, the oil in the bottom side oil chamber is discharged from the bottom side port 23b to the tank through the oil passage 72b, the arm control valve 73 and the oil passage 71b, and the arm cylinder 23 is reduced. When the pilot pressure Pp is supplied to the pilot port 73b, the arm control valve 73 moves to the downward movement position, connecting the oil passage 71a to the bottom side port 23b via the oil passage 72b, and the oil connected to the rod side port 23a. The path 72a is connected to an oil path 71b that connects to the tank. As a result, the line pressure PL is supplied to the bottom side oil chamber of the arm cylinder 23, the oil in the rod side oil chamber is discharged to the tank, and the arm cylinder 23 is extended.

  The generation and supply control of the pilot pressure Pp will be described. As described above, the charge hydraulic pressure Pch regulated and generated by the first control valve 62 is supplied to the oil passage 62 a, but the oil passage 62 b branched from the oil passage 62 a is connected to the third control valve 77. The third control valve 77 adjusts the charge hydraulic pressure Pch in accordance with the operation of the arm operation lever 78 (loader operation lever) to create the pilot pressure Pp. The pilot pressure Pp is supplied from the oil passages 74 a and 74 b to the pilot ports 73 a and 73 b of the arm control valve 73 in response to the operation of the arm operation lever 78, and controls the operation of the arm control valve 73. Thereby, the expansion / contraction operation of the arm cylinder 23 is controlled as described above, and the vertical swing operation of the arm 21 is performed. That is, the arm 21 swings up and down according to the operation of the arm operation lever 78.

  Since the pilot pressure Pp is created by regulating the charge hydraulic pressure Pch generated by the first control valve 62, as described above, the charge pressure Pch is used to prevent engine stall when the engine rotation is reduced due to an increase in traveling load. When the pressure decreases, the pilot pressure Pp also decreases. When the pilot pressure Pp is lowered in this way, when this is supplied to the pilot ports 73a and 73b of the arm control valve 73, a sufficient pressing force cannot be obtained, and the operation delay of the arm control valve 73 occurs or operates. There is a problem that it may disappear. As described above, when the operation delay of the arm control valve 73 occurs or does not operate, there arises a problem that even if the arm operation lever 78 is operated, the vertical swing operation of the arm 21 is delayed or does not operate.

  In view of such a problem, this control device is provided with hydraulic pressure sensors 75 and 76 for detecting the hydraulic pressure of the oil passages 74a and 74b for supplying the pilot pressure Pp. Detection signals from the hydraulic sensors 75 and 76 are input to the controller 50, and the controller 50 detects that the pilot pressure Pp has been supplied to one of the oil passages 74a and 74b. That is, the controller 50 detects this when the arm operation lever 78 is operated and the pilot pressure Pp is supplied to one of the pilot ports 73a and 73b.

  When it is detected that the pilot pressure Pp is supplied to any one of the pilot ports 73a and 73b, the controller 50 performs control to reduce the target engine speed (Neo). Here, as already described, when the actual engine speed (Nea) matches the target engine speed (Neo), the capacity of the hydraulic pumps 31 and 41 becomes the capacity corresponding to the operation of the travel operation lever 52. As described above, the first control valve 62 generates the charge hydraulic pressure Pch. That is, the charge hydraulic pressure Pch is generated so that the capacity control hydraulic pressures PcL and PcR according to the operation of the travel operation lever 52 can be generated.

The controller 50 can generate the capacity control hydraulic pressures PcL and PcR according to the operation of the travel operation lever 52 when the actual engine speed (Nea) coincides with the target engine speed (Neo) thus lowered. To generate a regulated charge oil pressure Pch. At this time, if the variable displacements of the hydraulic pumps 31 and 41 do not change, the discharge amount decreases as the engine speed decreases, so that the capacity control hydraulic pressures PcL and PcR corresponding to the operation of the travel operation lever 52 cannot be generated. For this reason, it is necessary to increase the variable capacity of the hydraulic pumps 31 and 41 in accordance with a decrease in the engine speed, and the controller 50 increases the charge hydraulic pressure Pch by the first control valve 62 to increase the variable capacity of the hydraulic pumps 31 and 41. Increase control.

  As can be seen from the above description, when the controller 50 performs a control to decrease the target engine speed (Neo), the control increases the charge hydraulic pressure Pch. When the charge hydraulic pressure Pch is thus increased, the pilot pressure Pp generated by the third control valve 77 is also increased. Therefore, the pilot pressure Pp supplied from the third control valve 77 to the pilot ports 73a and 73b of the arm control valve 73 in accordance with the operation of the arm operation lever 78 is increased, and the arm control valve 73 can be normally operated. It is possible to prevent the arm 21 from swinging up and down and malfunctioning.

  The control by the controller 50 described above will be described with reference to FIG. In FIG. 7, the target engine speed (Neo) is set to 2400 rpm by the accelerator operation dial 54, the travel operation lever 52 is not operated until time t1, and the travel operation lever 52 is operated from time t1. In this example, the vehicle 10 is caused to travel and the arm operation lever 78 is operated at time t4. As can be seen from this, the control and operation up to immediately before operating the arm operation lever 78 at time t4 are the same as those shown in FIG.

  Therefore, a brief description will be given up to time t3. First, until the time t1, since the traveling operation lever 52 is in a neutral position, the capacity of the left and right hydraulic pumps 31, 41 is zero, the engine EG is in a no-load state, and the actual engine speed Nea is the target engine speed Neo. The higher is about 2750 rpm. When the travel operation lever 52 is operated from time t1, the second control valve 65 adjusts and generates the capacity control hydraulic pressures PcL and PcR according to the operation of the travel operation lever 52, and the capacity of the left and right hydraulic pumps 31 and 41 is increased. The capacity is set according to the operation of the operation lever 52. The oil discharged from the hydraulic pumps 31 and 41 is sent to the left and right hydraulic motors 32 and 42 to rotate them, and the left and right sprockets 5a and 5b are rotationally driven to start traveling of the vehicle 10. As a result, as shown in the figure, the actual engine speed Nea decreases, and the engine driving torque TQe becomes an output corresponding to the pump driving load from the no-load state, and the solenoid of the first control valve 62 used for controlling the charge hydraulic pressure Pch. The energizing current Asol decreases from 1500 mA in accordance with the decrease in the actual engine speed Nea.

  At time t2, the actual engine speed Nea matches the target engine speed Neo, and the energization current Asol of the solenoid at this time is 1250 mA. This energization current value is a value that becomes the target charge oil pressure Pcho from which the capacity control oil pressures PcL and PcR in which the charge oil pressure Pch is regulated and set according to the operation of the operation lever 52 are obtained as they are. Even after time t2, the actual engine speed Nea continues to decrease due to the engine driving load, and the energization current Asol of the solenoid also decreases. As a result, the charge oil pressure Pch is lower than the target charge oil pressure Pcho, the capacity control oil pressures PcL and PcR are reduced, the capacity of the hydraulic pumps 31 and 41 is reduced, and the engine drive load is reduced. As a result, the actual engine speed Nea decreases most at time t3, but thereafter gradually increases with a decrease in the engine drive load, and gradually approaches the target engine speed Neo.

When the arm operation lever 78 is operated at time t4, the pilot pressure Pp is supplied to one of the pilot ports 73a and 73b of the arm control valve 73 according to the operation.
The supply of the pilot pressure Pp is detected by the hydraulic pressure sensors 75 and 76, and the detection signal is sent to the controller 50. Upon receiving this detection signal, the controller 50 reduces the target engine speed Neo. For example, as shown in FIG. 7, the target engine speed Neo (1) (= 2750 rpm) before the arm operation lever 78 is operated is reduced to the target engine speed Neo (2) (= 2000 rpm). As a result, the capacity control hydraulic pressures PcL and PcR need to be increased to increase the capacity of the hydraulic pumps 31 and 41 as described above, and the charge pressure Pch is increased.

  That is, when the arm operation lever 78 is not operated, control is performed so that the solenoid energization current Asol (1) becomes higher as indicated by the solenoid current Asol (2) when the arm operation lever 78 is operated. As a result, the charge pressure Pch is increased and the pilot pressure Pp is increased accordingly, and the pilot pressure Pp thus increased is supplied to one of the pilot ports 73 a and 73 b of the arm control valve 73. For this reason, the arm control valve 73 can be operated corresponding to the operation of the arm operation lever 78 accurately, and the vertical swing operation delay and the operation failure of the arm arm 21 can be prevented. The actual engine speed Noa is the actual engine speed Neo (1) when the arm operation lever 78 is not operated, but is indicated by the actual engine speed Neo (2) when the arm operation lever 78 is operated. Thus, the control approaches the target engine speed Neo (2) that has been reduced.

  In the above description, the case where the traveling operation lever 52 is mechanically connected to the second control valve 65 has been described. However, the travel operation lever 52 may be configured to be electrically connected to the second control valve 65 via the controller 50. In this case, the controller 50 can control the operation of the second control valve 65 based on operation information (input information) input from the travel operation lever 52.

EG engine 1 crawler loader 5 travel device 20 loader device 23 arm cylinder 28 bucket cylinder 30, 40 HST circuit 31, 41 hydraulic pump 32, 42 hydraulic motor 62 first control valve 65 second control valve 73 arm control valve 77 third control Valve 78 Arm control lever

Claims (4)

Engine,
A variable displacement hydraulic pump that is rotationally driven by the engine;
A hydraulic motor driven by oil discharged from the hydraulic pump;
A traveling device that is rotationally driven by the hydraulic motor;
A travel operation device operated to instruct the travel by the travel device;
A charge pump,
A first control valve that regulates the discharge oil of the charge pump to generate a charge hydraulic pressure;
A second control valve that regulates the charge hydraulic pressure in response to an operation of the travel operation device and generates a displacement control hydraulic pressure in accordance with the operation of the travel operation device;
The first control valve is configured to regulate and generate the charge hydraulic pressure according to the rotational speed of the engine,
The hydraulic traveling device control device according to claim 1, wherein the hydraulic pump is configured to perform variable displacement control with a displacement control oil pressure regulated by the second control valve. An accelerator operating device operated to instruct the engine drive;
An engine control device that performs drive control of the engine in response to an operation of the accelerator operation device;
A target engine rotation setting device that sets a target engine rotation speed according to the operation of the accelerator operation device;
An engine speed detector for detecting the rotational speed of the engine,
The first control valve regulates the charge hydraulic pressure so as to reduce the difference between the actual engine speed detected by the engine speed detector and the target engine speed set by the target engine speed setting device. The control device according to claim 1, wherein the control device is generated.   3. The control device according to claim 2, wherein the first control valve adjusts and generates the charge hydraulic pressure by PID control so as to reduce a difference between the actual engine rotation speed and the target engine rotation speed. . A hydraulic actuator actuated by a hydraulic actuator;
A main pump for supplying hydraulic oil to be supplied to the hydraulic actuator;
An operation control valve of a hydraulic pilot type that performs control to supply the discharge oil of the main pump to the hydraulic actuator;
An operation operating device operated to instruct the operation of the hydraulic operation device;
A third control valve that performs control to supply a pilot pressure to the operation control valve for controlling the operation of the operation control valve according to an operation of the operation operation device;
The third control valve is configured to adjust the charge hydraulic pressure generated by the first control valve to generate the pilot pressure,
A pilot detector for detecting that pilot pressure is supplied from the third control valve to the operation control valve;
4. The control device according to claim 2, wherein when the pilot detector detects that the pilot pressure is supplied to the operation control valve, the target engine rotation speed is reduced.

Images