JPH06193730A - Hydraulic motor drive circuit for traveling of work vehicle - Google Patents

Abstract

PURPOSE:To determine a running state of a vehicle, and set a relief pressure changeably for the whole speed range of the vehicle for reducing shock at the time of deceleration or acceleration effectively. CONSTITUTION:A pilot pressure in a pilot pipeline 8 is read from a pressure sensor 23 into a controller 7, and it is judged by the controller 27 if a vehicle is being decelerated, stopped, started, or accelerated based on the pilot pressure, etc., in accordance with an operation quantity of a traveling pedal 7A. When it is judged that the vehicle is under deceleration, a relief set pressure of a relief valve 19 is controlled to be a relief pressure in accordance with a traveling speed at this time, so a brake pressure in accordance with a motion quantity or motion energy at this time is applied to a hydraulic motor 3 to the vehicle traveling with the motion quantity or motion energy in accordance with the running speed. When the vehicle is being stopped, started, or accelerated, the relief set pressure of the relief valve 19 is controlled to be a relief pressure which is suitable for stopping starting, or acceleration in accordance with the pilot pressure at this time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic motor drive circuit for traveling of a work vehicle suitable for use in a hydraulic drive vehicle such as a wheel hydraulic excavator or a wheel loader.
In particular, the present invention relates to a traveling hydraulic motor drive circuit for a work vehicle, which is designed to prevent an impact from occurring during deceleration or acceleration of the vehicle.

[0002]

2. Description of the Related Art Generally, a hydraulic pump mounted on a hydraulic drive work vehicle such as a wheel hydraulic excavator and driven by a prime mover, and front and rear wheels by supplying and discharging pressure oil from the hydraulic pump. (Wheels) are driven to rotate to drive the vehicle, and a hydraulic motor for traveling is provided between the hydraulic motor, the hydraulic pump, and the tank, and is provided in the middle of the pair of main pipelines. A control valve for controlling the flow rate and direction of the pressure oil supplied to and discharged from the motor, operating means for traveling for switching the control valve according to the operation amount, and operation amount detection for detecting the operation amount of the operation means. Means, located between the hydraulic motor and the control valve, provided between the pair of main pipelines, when the control valve returns to the neutral position,
A counter balance valve that interlocks with the control valve to generate a braking pressure of the hydraulic motor, is provided between the counter balance valve and the hydraulic motor, and is provided between the pair of main pipelines. When the braking pressure exceeds a predetermined high pressure level, it is provided between the overload relief valve that relieves the pressure and the counter balance valve and the hydraulic motor, and is provided in the middle of a pair of main pipelines to brake the hydraulic motor. A tank pipeline for leading the pressure to the tank side, and a tank pipeline provided in the middle of the tank pipeline, which operates according to the detection value of the operation amount detecting means to reduce the braking pressure of the hydraulic motor to the relief of the overload relief valve. A hydraulic motor drive circuit for traveling of a work vehicle provided with a relief valve device for setting a pressure lower than a set pressure is known from, for example, Japanese Utility Model Laid-Open No. 2-144824. It has been.

In this type of conventional technique, the operating means for traveling is operated to switch the control valve from the neutral position, and the pressure oil from the hydraulic pump is supplied to and discharged from the hydraulic motor.
The rear wheels are rotated to drive the vehicle on the road. Then, when the operation amount of the operation means is reduced during the traveling on the road to suddenly decelerate the vehicle, the detection value of the operation amount detection means becomes small, whereby the relief valve device is actuated and the hydraulic motor of the hydraulic motor is operated. The braking pressure is set to a pressure lower than the relief setting pressure of the overload relief valve, and the braking pressure at this time is low-pressure relieved by the relief valve device so as to alleviate the impact during deceleration.

Further, the traveling hydraulic motor drive circuit according to this conventional technique is provided between the tank and the discharge side of the hydraulic pump, and when the drive pressure of the hydraulic motor exceeds a predetermined high pressure level. A main relief valve that relieves pressure, and operates according to the detection value of the operation amount detection means, and sets the drive pressure of the hydraulic motor to a pressure lower than the relief set pressure of the main relief valve. When the vehicle is suddenly started or suddenly accelerated, the operating means for traveling rises from a state where the operation amount is small, so that the detected value of the operation amount detecting means also rises from a small state. The other relief valve device sets the drive pressure of the hydraulic motor to a pressure lower than the relief set pressure of the main relief valve, and the drive pressure at this time is set to another relief pressure. At the start by the low pressure relief by-safe valve device, and so as to alleviate the impact at the time of acceleration.

[0005]

In the prior art described above, the relief valve device is operated according to the operation amount of the operating means when the vehicle is decelerated, and the braking pressure of the hydraulic motor is set to the relief set pressure of the overload relief valve. However, the braking pressure at this time cannot be set to a pressure corresponding to the traveling speed of the vehicle, and the impact during deceleration cannot be effectively mitigated. .

In addition, when the vehicle is suddenly started or suddenly accelerated, other relief valve devices are operated in the same manner as during deceleration, and the drive pressure of the hydraulic motor is set to a pressure lower than the relief set pressure of the main relief valve. However, there is a problem that the shock at the time of starting or accelerating cannot be effectively mitigated.

Further, it is necessary to separately provide a relief valve device for setting the relief pressure at the time of deceleration and another relief valve device for setting the relief pressure at the time of starting and accelerating, which complicates the entire structure. There's a problem.

On the other hand, as another conventional technique, the drive pressure of the hydraulic motor is set by the main relief valve when the vehicle is accelerated, and the braking pressure of the hydraulic motor is set by the overload relief valve of a relatively low pressure when the vehicle is decelerated. For example, JP-A-2-243833 proposes a traveling hydraulic motor drive circuit for a working vehicle in which the operation of the overload relief valve is prohibited until the control valve is returned to the neutral position. However, in this case, the shock at the time of starting or accelerating cannot be alleviated, and at the time of deceleration, the overload relief valve always sets a constant relief pressure, so the shock at deceleration is spread over the entire speed range. There is a problem that it cannot be alleviated.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention can determine the running state of the vehicle, can set the relief pressure variably over the entire speed range of the vehicle, and can reduce the pressure during deceleration. It is an object of the present invention to provide a traveling hydraulic motor drive circuit for a work vehicle, which is capable of effectively alleviating impact during acceleration.

[0010]

In order to solve the above-mentioned problems, the present invention provides a hydraulic pump mounted on a vehicle and driven by a prime mover, and a hydraulic pump and a tank connected via a pair of main pipelines. Is located between the hydraulic motor, the hydraulic pump, and the tank, and is located between the hydraulic motor, the hydraulic pump, and the tank for running the vehicle by supplying and discharging pressure oil from the hydraulic pump. A control valve that is provided to control the flow rate and direction of the pressure oil supplied to and discharged from the hydraulic motor, an operating unit for traveling that switches the control valve according to the operation amount, and an operation amount of the operation unit are provided. When the operation amount detecting means for detecting and the hydraulic motor and the control valve are provided in the middle of each of the main pipelines and the pressure acting on the hydraulic motor exceeds a required set pressure, Variable to relieve excess pressure when Relief pressure setting means, speed detecting means for detecting the traveling speed of the vehicle, traveling state determining means for determining the traveling state of the vehicle based on at least a signal from the operation amount detecting means, and the traveling state determining means. When it is determined that the vehicle is in deceleration by, so as to control the set pressure of the relief pressure setting means to a pressure suitable for deceleration based on a signal from the speed detection means,
A configuration including a control signal output means for outputting a control signal for deceleration to the relief pressure setting means is adopted.

The control signal output means determines the set pressure of the relief pressure setting means based on the signal from the manipulated variable detecting means when the running state determining means determines that the vehicle is accelerating. A configuration may be adopted in which a control signal for acceleration is output to the relief pressure setting means so as to control to a pressure suitable for acceleration.

Further, the control signal output means controls the set pressure of the relief pressure setting means to a pressure suitable for stopping when the running state judging means judges that the vehicle is stopped. Good.

On the other hand, the traveling state determining means may determine the traveling state of the vehicle based on a signal from the operation amount detecting means and a signal from the speed detecting means.

Further, a pair of pressure detecting means is provided between the hydraulic motor and the control valve in the middle of the pair of main pipelines, and the traveling state judging means is provided with a signal from each pressure detecting means. The traveling state of the vehicle may be determined based on the signal from the operation amount detecting means and the signal from the speed detecting means.

A counter balance valve is provided in the middle of the pair of main pipes between the hydraulic motor and the control valve, and the relief pressure setting means is provided between the counter balance valve and the hydraulic motor. It is preferably located and provided in the middle of each of the main pipelines.

In this case, the relief pressure setting means is disposed between the counter balance valve and the hydraulic motor and is arranged between the pair of main pipelines, and the pressure oil on the high pressure side of each of the main pipelines is discharged. A high pressure selection valve to be selected, and a relief valve of a set pressure variable type which is provided in the middle of a tank pipe line connecting the high pressure selection valve to a tank and variably sets a relief pressure by a control signal from the control signal output means. It should be composed of.

Further, the relief pressure setting means is provided between the counter balance valve and the hydraulic motor, and the pair of overload relief valves are respectively disposed between the pair of main pipelines, and the respective overload relief valves. A relief type pressure control valve for variably controlling the relief pressure of the relief valve by a control signal from the control signal output means may be used.

[0018]

With the above structure, the traveling state of the vehicle can be determined at an early stage based on the operation amount of the operating means for traveling, and when it is determined that the vehicle in the middle of traveling is decelerating, the vehicle is decelerated according to the traveling speed of the vehicle. Since the relief pressure at the time can be set, the braking pressure corresponding to the energy at this time can be applied to the hydraulic motor for the vehicle traveling with the energy corresponding to the traveling speed, and the braking pressure becomes excessive. It is possible to reliably prevent it from becoming too small or too small.

Further, at the time of starting or accelerating the vehicle, the relief pressure suitable for acceleration can be set according to the operation amount of the operating means, and the driving pressure acting on the hydraulic motor becomes excessive.
It can be prevented from being too small. Then, when the vehicle is stopped, the relief pressure suitable for this can be set, and the vehicle can be held in a stopped state.

[0020]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 9 by taking a hydraulic motor drive circuit for a wheel hydraulic excavator as an example of a hydraulic motor drive circuit for traveling of a work vehicle.

1 to 7 show a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a variable displacement hydraulic pump which is mounted on a vehicle and is rotationally driven by a prime mover (not shown) such as an engine. The hydraulic pump 1 is a tank 2
It sucks the hydraulic oil inside and discharges high-pressure oil (hereinafter referred to as pressure oil). Reference numeral 3 denotes a traveling hydraulic motor connected to the hydraulic pump 1 and the tank 2 via a pair of main pipelines 4A and 4B. The hydraulic motor 3 is a variable displacement hydraulic motor having a variable capacity portion 3A. The output shaft 3B is connected to front and rear wheels (neither is shown) via a speed reducer or the like. Then, the hydraulic motor 3 is rotated in the forward direction or the reverse direction by supplying / discharging the pressure oil from the hydraulic pump 1 via the main pipelines 4A, 4B, and drives these wheels to drive the vehicle.

Reference numeral 5 denotes a control valve located between the hydraulic motor 3 and the hydraulic pump 1 and the tank 2 and provided in the middle of the main pipelines 4A and 4B. The control valve 5 is a pair of hydraulic pilot portions 5A. , 5B, for example, a 4-port 3-position hydraulic pilot type directional control valve, which is switched from a neutral position (a) to a switching position (b) or (c) by a pilot pressure Ps described later. The control valve 5 controls the flow rate of the pressure oil supplied to and discharged from the hydraulic motor 3 in accordance with the stroke amount when the neutral position (a) is switched to the switching positions (b) and (c), and the switching position ( B) side and switching position (c)
With respect to the side, the rotation direction of the hydraulic motor 3 is controlled to be switched between the forward direction and the reverse direction.

Reference numeral 6 denotes a hydraulic pump for supplying pilot pressure, which is driven by a prime mover together with the hydraulic pump 1. Reference numeral 7 denotes a traveling pedal 7A for moving the control valve 5 from the neutral position (a) to the switching positions (b) and (c). A pressure-reducing valve type pilot valve is shown as a traveling operation means for switching the traveling speed V to control the traveling speed V. The pilot valve 7 is connected to the hydraulic pump 6 on the high pressure side and to the tank 2 on the low pressure side. , Its output side is connected to the pilot line 8. The pilot valve 7 is interlocked with a traveling pedal 7A provided in a driver's cab (not shown), and a pilot pressure Ps corresponding to an operation amount (depression amount) of the traveling pedal 7A is supplied from the hydraulic pump 6 to a pilot conduit. Supply within 8.

Reference numeral 9 denotes a forward / reverse switching valve for switching and connecting the pilot conduit 8 to the pilot conduits 8A and 8B. The forward / rearward switching valve 9 is composed of a 4-port 3-position directional switching valve and is provided in the operator's cab. A switching lever 9A is provided to move the neutral position (N) to the forward position (F) or the reverse position (R).
Is switched to. Here, the pilot conduits 8A, 8
B is connected to the hydraulic pilot portions 5A and 5B of the control valve 5, and when the forward / reverse switching valve 9 is switched to the forward position (F), the pilot pressure Ps from the pilot valve 7 acts on the hydraulic pilot portion 5A. When it is switched to the reverse position (R), the pilot pressure Ps is applied to the hydraulic pilot portion 5B.

Reference numeral 10 denotes a slow return valve as a speed regulating valve provided between the pilot valve 7 and the forward / reverse switching valve 9 and provided in the middle of the pilot pipe line 8. The slow return valve 10 is a throttle 10A. The throttle 10A prevents the control valve 5 from returning to the neutral position (a) early when the operation of depressing the travel pedal 7A is released.

Reference numeral 11 denotes a counterbalance valve provided between the hydraulic motor 3 and the control valve 5 and provided in the middle of the main pipelines 4A and 4B. The counterbalance valve 11 is interlocked with the forward or reverse drive pressure. Then, when the control valve 5 returns to the neutral position (a) and the drive pressure decreases, the control valve 5 returns to the position shown in the figure in conjunction with this, and the braking pressure of the hydraulic motor 3 is generated in the main pipeline 4A or 4B. Let

Reference numeral 12 is a control valve 5 and a counter balance valve 11.
And a shuttle valve as a high-pressure selection valve provided between the main pipelines 4A and 4B, which is located between the main pipelines 4A and 4B. By selecting and guiding the driving pressure of the hydraulic motor 3 into the control line 13, for example, the servo cylinder 1 described later
At 4, the capacity of the hydraulic motor 3 is switched according to the driving pressure at this time.

Reference numeral 14 denotes a servo cylinder attached to the hydraulic motor 3, and the servo cylinder 14 is a drive rod 14
The tip of A is connected to the variable capacity section 3A of the hydraulic motor 3,
The displacement varying unit 3A of the hydraulic motor 3 is tilted according to the pressure from the control line 13. Then, the servo cylinder 1
Reference numeral 4 indicates that the capacity varying section 3A is always tilted to the small capacity side to rotate the hydraulic motor 3 at a high speed with a small torque so that the pressure from the control line 13, that is, the driving pressure that is the motor self pressure exceeds a predetermined pressure. At this time, the capacity varying portion 3A is tilted to the large capacity side, and the hydraulic motor 3 is rotated at a low speed with a large torque.

Reference numeral 15 denotes a make-up check valve provided between the hydraulic motor 3 and the counter balance valve 11 and provided between the main pipelines 4A and 4B. The check valve 15 is provided via a tank pipeline 16. When the main pipe 4A or 4B is connected to the tank 2 and there is a negative pressure in the main pipe 4A or 4B during braking of the hydraulic motor 3 or the like, the hydraulic oil in the tank 2 is supplied to the main pipe 4A or 4B to prevent the occurrence of cavitation. To do.

Reference numeral 17 denotes another shuttle valve as a high-pressure selection valve provided between the hydraulic motor 3 and the counterbalance valve 11 and provided between the main pipelines 4A and 4B. The shuttle valve 17 is the main pipeline 4A. , 4B, the main line 4A or 4B on the high pressure side between the hydraulic motor 3 and the counterbalance valve 11 is selected, and the high pressure side pressure oil is transferred to the other tank line 18
Guide inside. The tank line 18 is connected to the tank 2 through the tank line 16 at the position of the makeup check valve 15.

Reference numeral 19 is a shuttle valve 17 and a tank line 1.
8 is a relief pressure variable type relief valve that constitutes a relief pressure setting means together with the relief pressure setting means 8.
The solenoid proportional solenoid section 19A variably sets the relief pressure Pr with the characteristic 20 shown by the solid line in FIG. The relief valve 19 is opened when the pressure of the pressure oil introduced into the tank line 18 via the shuttle valve 17 exceeds the relief set pressure by the electromagnetic proportional solenoid section 19A, and this pressure is set to the tank line 16 Relief to the tank 2 via the structure prevents excessive pressure from acting on the hydraulic motor 3.

Reference numeral 21 denotes a main relief valve provided between the hydraulic pump 1 and the tank 2 and the control valve 5 on the discharge side of the hydraulic pump 1. The relief valve 21 is the hydraulic pump 1. When the pressure of the pressure oil discharged from the pump, for example, the driving pressure of the hydraulic motor 3 exceeds a predetermined high pressure level (relief setting pressure), this pressure is relieved and the hydraulic pump 1
It is possible to prevent excessive pressure from acting on the hydraulic motor 3 and the like.

Reference numeral 22 is a control valve 5 and a counter balance valve 11.
And a center joint provided in the middle of the main pipelines 4A, 4B, etc., between the lower traveling body and the upper revolving body (both not shown) of the wheel type hydraulic excavator. The pressure oil from the hydraulic pump 1 can be supplied to and discharged from the hydraulic motor 3 even when the upper swing body is swung. That is, the hydraulic motor 3, the counter balance valve 11, etc. are provided in the lower traveling body, and the hydraulic pumps 1, 6, the control valve 5, the pilot valve 7, etc. are provided in the upper revolving body.

Reference numeral 23 denotes a pressure sensor as an operation amount detecting means provided between the forward / reverse switching valve 9 and the slow return valve 10 and provided in the middle of the pilot pipe line 8. The pressure sensor 23 is a pilot pipe. The pilot pressure Ps in the road 8 is detected as the operation amount (depression amount) of the traveling pedal 7A, and a detection signal is output to the controller 27 described later.

Reference numerals 24A and 24B denote pressure sensors as a pair of pressure detecting means provided between the hydraulic motor 3 and the counterbalance valve 11 and provided in the middle of the main pipelines 4A and 4B. 24B is the main pipeline 4A, 4
The pressures Pa and Pb in B are detected, and the detection signals are output to the controller 27.

Reference numeral 25 denotes a rotation speed sensor as a speed detecting means provided near the output shaft 3B of the hydraulic motor 3, and the rotation speed sensor 25 detects the rotation speed N of the hydraulic motor 3.
The detection signal is output to the controller 27.

Reference numeral 26 denotes a drain line of the hydraulic motor 3,
The drain pipe line 26 is connected to the tank 2 via the center joint 22 together with the tank pipe line 16 and discharges leaked oil (a part of the pressure oil) generated in the hydraulic motor 3 into the tank 2.

Further, 27 indicates a controller as a control device comprising a microcomputer or the like, and the input side of the controller 27 is the pressure sensors 23, 24A, 2
4B and the rotation speed sensor 25 and the like, and the output side is connected to the electromagnetic proportional solenoid portion 19A and the like of the relief valve 19. The controller 27 stores the program shown in FIG.
The relief pressure control process 9 and the like are performed. Further, in the storage circuit of the controller 27, in the storage area 27A, a traveling speed calculation map illustrated by a solid line in FIG. 4, a relief pressure calculation map including a characteristic 28 illustrated by a solid line in FIG. 5, and in FIG. In FIG. 7, a relief pressure calculation map including a characteristic 29 illustrated by a solid line, a relief pressure setting value (not shown) suitable for a stop, and a current value conversion map including a characteristic 30 illustrated by a solid line in FIG. 7 are stored. There is.

Here, the traveling speed calculation map shown in FIG. 4 is configured to calculate the traveling speed V of the vehicle from the rotation speed N of the hydraulic motor 3 detected by the rotation speed sensor 25, and the relief pressure shown in FIG. The calculation map is configured to calculate the relief pressure Pr suitable for deceleration based on the traveling speed V of the vehicle. Further, the relief pressure calculation map shown in FIG. 6 indicates that the pressure sensor 23 is used as the operation amount of the traveling pedal 7A.
The relief pressure Pr suitable for accelerating the vehicle is calculated from the pilot pressure Ps in the pilot line 8 detected in step 1. The current value conversion map shown in FIG. 7 is obtained by converting the relief pressure Pr shown in FIG. 5 and FIG. The relief pressure Pr of the relief valve 19 has a characteristic shown in FIG. 2 when converted into a current value and a control signal having this current value is output to the electromagnetic proportional solenoid portion 19A of the relief valve 19. ing.

The hydraulic motor drive circuit for the wheel hydraulic excavator according to the present embodiment has the above-mentioned structure, and its operation will be described below.

First, when the hydraulic motor 3 is rotated in the forward direction in order to rotate the front and rear wheels (wheels) provided on the lower traveling body of the wheel-type hydraulic excavator in the forward direction to move the vehicle forward, When the switching valve 9 is switched from the neutral position (N) to the forward position (F) and the traveling pedal 7A is stepped on, the pilot pressure Ps corresponding to the operation amount is generated from the pilot valve 7 to the pilot conduit portion of the pilot conduit 8. 8
It is supplied to the hydraulic pilot portion 5A of the control valve 5 via A, and the control valve 5 controls the pilot pressure Ps, that is, the traveling pedal 7
The neutral position (a) by the stroke amount corresponding to the operation amount of A
Is switched to the switching position (b) side, and the driving pressure of the hydraulic motor 3 is generated in the main pipeline 4A. The control valve 5 controls the flow rate of the pressure oil supplied to and discharged from the hydraulic pump 1 to the hydraulic motor 3 according to the operation amount at this time, and the traveling pedal 7
The hydraulic motor 3 is rotated in the forward direction at a speed corresponding to the operation amount of A.

When the operation of depressing the traveling pedal 7A is released, the pilot line 8 is connected to the tank 2 via the pilot valve 7 and the forward / reverse switching valve 9 is switched to the forward position (F). Hydraulic pilot section 5 of control valve 5
The pilot pressure Ps supplied to A is the slow return valve 1
It is gradually discharged to the tank 2 side through the 0 throttle 10A,
The control valve 5 gradually returns from the switching position (b) to the neutral position (a), and the counter balance valve 11 also returns to the position shown in the figure in conjunction with this. As a result, the pressure oil can be confined between the hydraulic motor 3 and the control valve 5, or substantially the counter balance valve 11 in the main pipelines 4A and 4B, and the hydraulic motor 3 can be rotated by inertia. When continuing, the braking pressure of the hydraulic motor 3 is generated on the side of the main pipeline 4B, and the hydraulic motor 3 is gradually stopped by the throttling action of the counter balance valve 11 or the like.

However, when the braking pressure becomes excessive, a high braking pressure acts on the hydraulic motor 3 which continues inertial rotation in a direction opposite to the rotating direction, so that the entire drive circuit of the hydraulic motor 3 is driven. An impact such as sudden braking is generated, the driver feels uncomfortable or hinders driving, and the driving stability is deteriorated.

Therefore, in this embodiment, the controller 27
By performing relief pressure control processing of the relief valve 19 as will be described later, the relief set pressure of the relief valve 19 is variably set to the relief pressure Pr suitable for the traveling state of the vehicle, and the braking pressure acting on the hydraulic motor 3 is set. Alternatively, when the driving pressure becomes excessive, the relief valve 19 is opened, and the excess pressure at this time is transferred from the shuttle valve 17 to the tank pipes 18, 1.
When the vehicle is decelerated, it is relieved to the tank 2 via 6
It is designed to effectively mitigate the occurrence of shocks when starting or accelerating.

When the forward / reverse switching valve 9 is switched to the reverse position (R), the control valve 5 is switched from the neutral position (a) to the switching position (c) according to the operation amount of the traveling pedal 7A. Driving pressure of the hydraulic motor 3 is generated on the side of the main pipeline 4B, the hydraulic motor 3 rotates in the opposite direction, and the lower traveling body (vehicle) moves backward. Then, when the operation of the traveling pedal 7A is released, the control valve 5 returns to the neutral position (a) similarly to the forward movement, and in this case, the braking pressure is generated on the main pipe line 4A side,
The hydraulic motor 3 is gradually stopped. In addition, the forward / reverse switching valve 9
Is returned to the neutral position (N), the travel pedal 7
Regardless of the operation of A, the control valve 5 is held at the neutral position (A).

Next, the relief pressure control process of the relief valve 19 by the controller 27 will be described with reference to FIGS.

First, when the processing operation is started, in step 1, the rotational speed N of the hydraulic motor 3 is read from the rotational speed sensor 25, and the pilot pressures Ps and pressures Pa and Pb are read from the pressure sensors 23, 24A and 24B. Step two
In order to determine the running state of the vehicle, the acceleration / deceleration determination of the vehicle is performed.

In this case, when the pilot pressure Ps detected by the pressure sensor 23 is decreasing, the traveling pedal 7A is released, and the control valve 5 reduces the amount of pressure oil supplied to and discharged from the hydraulic pump 1 to the hydraulic motor 3. Therefore, at this time, it is possible to determine that the vehicle is in the decelerating state, and the processing of step 3 and subsequent steps described later is performed. When the operation of the traveling pedal 7A is released and the pressures Pa and Pb in the main pipelines 4A and 4B are substantially equal to each other, or when the rotation speed N of the hydraulic motor 3 is zero, the vehicle is Since it can be determined that the vehicle is stopped, step 8 described later is performed. On the other hand, when the pilot pressure Ps detected by the pressure sensor 23 is increasing, the travel pedal 7A is stepped on, and when the vehicle starts, or the operation amount of the travel pedal 7A becomes large, the hydraulic pressure is supplied to the hydraulic motor 3. Since it is possible to determine that the vehicle is in an accelerating state due to an increase in the flow rate of pressure oil, the process of step 9 described later is performed.

When it is determined in step 2 that the vehicle is decelerating, the traveling speed V of the vehicle is calculated from the traveling speed map shown by the solid line in FIG. Then, the relief pressure Pr during deceleration is calculated based on the traveling speed V of the vehicle from the relief pressure calculation map of the characteristic 28 shown by the solid line in FIG.

Next, in step 5, the relief pressure Pr at this time is converted into a current value by the current value conversion map of the characteristic 30 shown by the solid line in FIG. 7, and the process proceeds to step 6 for deceleration corresponding to this current value. By outputting the control signal to the solenoid proportional solenoid portion 19A of the relief valve 19, the relief set pressure of the relief valve 19 is controlled to be the relief pressure Pr corresponding to the traveling speed V at this time, and the process returns at step 7. .

When it is determined in step 2 that the vehicle is stopped, the process proceeds to step 8 to calculate the relief pressure Pr suitable for the stop from the set value preset in the storage area 27A, and the step 5 Then, the relief pressure Pr at this time is converted into a current value by the current value conversion map shown in FIG. 7, and the process proceeds to step 6 and the control signal for stop corresponding to this current value is sent to the electromagnetic proportional solenoid section 19A of the relief valve 19. Is output to control the relief setting pressure of the relief valve 19 to be the relief pressure Pr suitable for the stop.

Further, when it is determined in step 2 that the vehicle is accelerating, the process proceeds to step 9 and the relief pressure Pr suitable for acceleration is calculated from the relief pressure calculation map shown in FIG. 6 based on the pilot pressure Ps at this time. Then, in step 5, the relief pressure Pr at this time is converted into a current value by the current value conversion map shown in FIG. 7, and in step 6, the control signal for acceleration corresponding to this current value is sent to the relief valve 19.
By outputting to the electromagnetic proportional solenoid section 19A of
The relief set pressure of the relief valve 19 is controlled to be the relief pressure Pr suitable for the acceleration state at this time.

Thus, according to this embodiment, it is determined whether the vehicle is decelerating, stopping, or starting and accelerating based on the pilot pressure Ps corresponding to the operation amount of the traveling pedal 7A. If it is possible to make a positive determination, and if it is determined that the vehicle is decelerating, the relief set pressure of the relief valve 19 is controlled to the relief pressure Pr corresponding to the traveling speed V at this time, so that the momentum or kinetic energy corresponding to the traveling speed V is controlled. With respect to the vehicle traveling with the braking force, the braking pressure according to the momentum or the kinetic energy at this time can be applied to the hydraulic motor 3, and the braking pressure can be surely prevented from becoming excessive or excessive. It can be prevented.

Further, when it is determined that the vehicle is stopped, the relief set pressure of the relief valve 19 can be controlled to a preset relief pressure Pr suitable for stopping, and the vehicle can be held in a stopped state. At the time of starting or accelerating the vehicle, the relief set pressure of the relief valve 19 can be set to a relief pressure Pr suitable for starting and accelerating corresponding to the pilot pressure Ps at this time, and the driving pressure acting on the hydraulic motor 3 is excessive. Then, the relief valve 19 is opened,
The excess pressure at this time can be relieved to the tank 2 through the tank pipe lines 18 and 16.

Therefore, in this embodiment, when the vehicle is suddenly started or suddenly accelerated, the driving pressure of the hydraulic motor 3 can be controlled to be surely reduced to the relief pressure Pr corresponding to the operation amount of the traveling pedal 7A. It is possible to effectively prevent an impact from occurring when the vehicle is suddenly started and suddenly accelerated, and it is possible to smoothly start and accelerate the vehicle by operating the traveling pedal 7A.

Further, when the vehicle is decelerated, a braking pressure corresponding to the kinetic energy of the vehicle can be applied to the hydraulic motor 3, which effectively causes an impact such as a sudden braking during sudden deceleration. The relief pressure Pr can be variably set in the whole speed range of the vehicle from low speed to high speed, and various effects such as improvement of steering stability and safety can be achieved.

Next, FIG. 8 shows a second embodiment of the present invention. In this embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. To do
The feature of this embodiment is that when the pressure acting on the hydraulic motor 3 exceeds a required set pressure, a variable relief pressure setting means for relieving excess pressure at this time is provided with the counter balance valve 11 and the hydraulic motor 3. And a pair of overload relief valves 31A, 31B respectively disposed between the pair of main pipelines 4A, 4B and pilot lines 32A, 32B of the overload relief valves 31A, 31B. A shuttle valve 33 as a high-pressure selection valve that selects the high-pressure side of the pilot conduits 32A and 32B;
The shuttle valve 33 is provided in the middle of another drain line 34 connecting to the drain line 26 of the hydraulic motor 3, and the relief pressure Pr of the overload relief valves 31A and 31B is variably controlled by a control signal from the controller 35. And a variable pressure control valve 36 that operates.

Here, the controller 35 has substantially the same structure as the controller 27 described in the first embodiment.
Although a map similar to the maps shown in FIG. 4 to FIG. 7 is stored in the storage area 35A, the current value of the control signal output to the electromagnetic proportional solenoid portion 36A of the pressure control valve 36 is stored in the controller 35. , Pressure control valve 3
It is set small corresponding to the pressure acting on 6. Further, the outflow sides of the overload relief valves 31A and 31B are connected to the base end side of the pipeline 37, and the tip end side of the pipeline 37 is provided with a makeup check valve 15 between the counter balance valve 11 and the hydraulic motor 3. It is connected to the main pipelines 4A and 4B through the tank pipeline 16 as well.

Then, the overload relief valve 31A,
31B is a pressure control valve 3 located in the middle of the drain conduit 34.
When the driving pressure or the braking pressure acting on the hydraulic motor 3 exceeds the respective relief pressures Pr suitable for starting, accelerating, decelerating or stopping the vehicle, the drain line is normally held by the valve 6. When the pressure control valve 36 is opened by the pilot pressure generated in the valve 34, either one of the overload relief valves 31A and 31B is opened in conjunction with this, and the excess pressure at this time is released to the pipe 37 and Main line 4 via make-up check valve 15
Of A and 4B, it is relieved in the low pressure side main conduit 4A or 4B.

Thus, in this embodiment having the above-described structure, it is possible to obtain substantially the same effects as the first embodiment. However, in this embodiment, in particular, the counter balance valve 11 and the hydraulic motor 3 are connected to each other. A pair of main pipes 4 located between
The pressure control valve 36 variably controls the relief pressure Pr of the pair of overload relief valves 31A and 31B disposed between A and 4B by a control signal from the controller 35, and the pressure control valve 36 is overloaded. Relief valve 3
Of the pilot conduits 32A, 32B of 1A, 31B,
Since the high pressure side is provided in the middle of another drain line 34 connected to the drain line 26 of the hydraulic motor 3 via the shuttle valve 33, the overload relief valves 31A, 31
The pressure acting on the pressure control valve 36 can be significantly reduced as compared with the pressure acting on B.
Can be downsized together with the electromagnetic proportional solenoid section 36A to reduce the cost.

Next, FIG. 9 shows a third embodiment of the present invention. In this embodiment as well, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. To do
The feature of this embodiment is that when the pressure acting on the hydraulic motor 3 exceeds a required set pressure, a variable relief pressure setting means for relieving excess pressure at this time is provided with the counter balance valve 11 and the hydraulic motor 3. And a pair of bypass pipelines 41A, 41B connected between the pair of main pipelines 4A, 4B, respectively, and a control signal from the controller 42 provided in the middle of the bypass pipelines 41A, 41B. It consists of a pair of set pressure variable relief valves 43A and 43B that variably control the relief pressure Pr.

Here, the controller 42 has substantially the same structure as the controller 27 described in the first embodiment.
Although a map similar to the maps shown in FIGS. 4 to 7 is stored in the storage area 42A, the controller 42 uses the electromagnetic proportional solenoids 44A and 44B of the relief valves 43A and 43B for deceleration and acceleration, respectively. It is configured to output a control signal for stop or stop.

Further, the bypass pipes 41A, 41B have the relief valves 43A, 43B located in the middle thereof always kept closed, so that the main pipes 4A, 4B are connected via the bypass pipes 41A, 41B. To prevent communication with each other and ensure that driving pressure or braking pressure of the hydraulic motor 3 is generated in the main pipelines 4A and 4B. When the driving pressure or the braking pressure acting on the hydraulic motor 3 exceeds the respective relief pressures Pr suitable for starting, accelerating, decelerating or stopping the vehicle, the bypass pipeline 41A,
One of the relief valves 43A and 43B is opened in the middle of 41B, so that the excess pressure at this time is reduced to the main line 4
Of A and 4B, it is relieved in the low pressure side main conduit 4A or 4B.

Thus, in this embodiment having the above-described structure, it is possible to obtain substantially the same effect as that of the first embodiment. However, particularly in this embodiment, the counter balance valve 11 and the hydraulic motor 3 are connected to each other. A pair of main pipes 4 located between
Since the relief valves 43A and 43B are arranged between the A and 4B via the bypass pipes 41A and 41B, the shuttle valve 17 and the like used in the first embodiment can be eliminated and the hydraulic circuit can be simplified. can do.

Further, the controller 42 uses the pressure sensor 24
The pressures Pa and Pb in the main pipelines 4A and 4B are read from A and 24B, and the relief valve 43 is read based on the pressures Pa and Pb.
A control signal may be selectively output to the electromagnetic proportional solenoids 44A and 44B of A and 43B. In this case, when the pressure Pa in the main pipe line 4A of the pressures Pa and Pb is high, the relief valve 43A is controlled. By outputting a signal and outputting a control signal to the relief valve 43B when the pressure Pb in the main pipeline 4B is high, the drive pressure or braking pressure acting on the hydraulic motor 3 is started, accelerated, decelerated or stopped. The relief pressures Pr can be suppressed to below the respective suitable relief pressures Pr, and steering stability and safety can be effectively improved.

In each of the above-mentioned embodiments, step 2 of the program shown in FIG. 3 shows a concrete example of the traveling state judging means which is a constituent of the present invention, and step 3 shows a concrete example of the speed detecting means. , Step 4 to Step 9 show specific examples of the control signal output means.

In each of the above embodiments, the pressure sensor 23
Although it has been described that the running state of the vehicle is determined based on the pilot pressure Ps or the like detected in step 1, if the signal from the forward / reverse switching valve 9 is read in step 1 shown in FIG. When the advance switching valve 9 is switched to the forward position (F) and the pressure Pa in the main pipeline 4A of the main pipelines 4A and 4B is higher than the pressure Pb in the main pipeline 4B, the vehicle is in an accelerated state. It can be determined that the vehicle is in the deceleration state when the pressure Pb in the main pipeline 4B is higher than the pressure Pa in the main pipeline 4A. Further, even when the forward / reverse switching valve 9 is switched to the reverse position (R), it is possible to determine whether the vehicle is decelerating or accelerating, and the forward / reverse switching valve 9 is set to the neutral position (N). In the switched state, when the pressure Pa in the main pipeline 4A and the pressure Pb in the main pipeline 4B are equal, it can be determined that the vehicle is stopped.

Further, in each of the above embodiments, the storage area 27A (35A, 42) of the controller 27 (35, 42) is used.
In FIG. 5A, the relief pressure calculation map composed of the characteristic 28 illustrated by the solid line in FIG. 5 and the relief pressure calculation map composed of the characteristic 29 illustrated by the solid line in FIG. 6 are stored. Instead, the relief pressure calculation maps having the characteristics 28A and 29A shown by the dotted lines in FIGS. 5 and 6 may be stored in the storage areas 27A (35A, 42A), respectively.

On the other hand, in each of the above embodiments, the relief valve 19
(31A, 31B, 43A, 43B) relief pressure Pr
The electromagnetic proportional solenoid section 19A (36A, 44A, 44
2), the characteristic 20 shown by the solid line in FIG. 2 is variably set. However, instead of this, the relief valve 19 (31A) has the characteristic 20A shown in FIG. , 31B, 43A, 43B), the relief pressure Pr may be set variably. In this case, the relief valve 19 may be activated when a disconnection accident occurs.
(31A, 31B, 43A, 43B) relief pressure Pr
Can be kept at the maximum pressure and a fail-safe function can be given. Further, in this case, the current value conversion map having the characteristic 30A shown by the dotted line in FIG.
The configuration may be such that it is stored in (35A, 42A).

[0071]

As described above in detail, according to the present invention, variable relief pressure setting means for relieving excess pressure is provided between the hydraulic motor and the control valve, at least in the middle of each main pipeline. When it is determined that the traveling state of the vehicle is decelerating based on the signal from the operation amount detecting means for traveling, the control signal for deceleration is output to the relief pressure setting means,
Since the set pressure of the relief pressure setting means is controlled to a pressure suitable for deceleration based on the signal from the speed detecting means, the running state of the vehicle can be discriminated early based on the operation amount of the operating means for running. When it is determined that the vehicle in the middle of traveling is decelerating, the relief pressure at the time of deceleration can be set according to the traveling speed of the vehicle. Then, for the vehicle traveling with energy corresponding to the traveling speed, the braking pressure corresponding to the energy at this time can be applied to the hydraulic motor, and the braking pressure becomes excessive or excessive. Can be reliably prevented.

Further, at the time of starting or accelerating the vehicle, the relief pressure suitable for acceleration can be set according to the operation amount of the operating means, and the driving pressure acting on the hydraulic motor becomes excessive or excessive. Can be prevented. Then, when the vehicle is stopped, the relief pressure suitable for this can be set, and the vehicle can be held in a stopped state.

Therefore, the relief pressure can be variably set over the entire speed range of the vehicle, the impact at the time of deceleration or acceleration can be effectively alleviated, and the steering stability and safety can be surely improved. Various effects such as being possible can be achieved.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing a hydraulic motor drive circuit for a wheel hydraulic excavator according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a relief pressure by the relief valve in FIG. 1 and a current of a control signal applied to an electromagnetic proportional solenoid section.

FIG. 3 is a flowchart showing a relief pressure control process of a relief valve by a controller.

FIG. 4 is an explanatory diagram of a traveling speed calculation map stored in a storage area of a controller.

FIG. 5 is an explanatory diagram of a relief pressure calculation map stored in a storage area of the controller.

FIG. 6 is an explanatory diagram of another relief pressure calculation map stored in the storage area of the controller.

FIG. 7 is an explanatory diagram of a current value conversion map stored in a storage area of a controller.

FIG. 8 is a hydraulic circuit diagram showing a hydraulic motor drive circuit for a wheel hydraulic excavator according to a second embodiment.

FIG. 9 is a hydraulic circuit diagram showing a hydraulic motor drive circuit for a wheel hydraulic excavator according to a third embodiment.

[Explanation of symbols]

1 Hydraulic Pump 2 Tank 3 Hydraulic Motor 4A, 4B ... Main Pipeline 5 Control Valve 7 Pilot Valve (Operating Means) 7A Travel Pedal 8 Pilot Pipeline 9 Forward / Reverse Switching Valve 11 Counterbalance Valve 16, 18 Tank Pipeline 17 Shuttle Valve ( High pressure selection valve) 19,43A, 43B Relief valve (relief pressure setting means) 19A, 36A, 44A, 44B Electromagnetic proportional solenoid 23 Pressure sensor (manipulation amount detection means) 24A, 24B Pressure sensor (pressure detection means) 25 Number of revolutions Sensor (speed detection means) 26,34 Drain pipe 27,35,42 Controller (control device) 31A, 31B Overload relief valve (relief pressure setting means) 36 Pressure control valve 41A, 41B Bypass pipe

Claims (8)

[Claims] 1. A hydraulic pump mounted on a vehicle, which is driven by a prime mover, and a hydraulic pump and a tank, which are connected to each other through a pair of main pipes, and by supplying and discharging pressure oil from the hydraulic pump. A hydraulic motor for traveling that drives the vehicle, and a flow rate of pressure oil that is provided between the hydraulic motor, the hydraulic pump, and the tank and that is provided in the middle of each of the main pipelines, and that is supplied to and discharged from the hydraulic motor. A control valve for controlling the direction,
An operating means for traveling for switching the control valve according to the operation amount, an operation amount detecting means for detecting the operation amount of the operating means, and each of the main pipes located between the hydraulic motor and the control valve. When the pressure acting on the hydraulic motor exceeds a required set pressure provided in the middle of the road, a variable relief pressure setting means for relieving excess pressure at this time and a traveling speed of the vehicle are detected. A speed detecting means; a traveling state determining means for determining a traveling state of the vehicle based on at least a signal from the operation amount detecting means; and, when the traveling state determining means determines that the vehicle is decelerating, Control signal output means for outputting a control signal for deceleration to the relief pressure setting means so as to control the set pressure of the relief pressure setting means to a pressure suitable for deceleration based on a signal from the speed detection means. Traveling hydraulic motor drive circuit configured comprising a work vehicle. 2. The control signal output means sets the set pressure of the relief pressure setting means based on a signal from the manipulated variable detecting means when the running state determining means determines that the vehicle is accelerating. The hydraulic motor drive circuit for traveling of the work vehicle according to claim 1, wherein a control signal for acceleration is output to the relief pressure setting means so as to control to a pressure suitable for acceleration. 3. The control signal output means is configured to control the set pressure of the relief pressure setting means to a pressure suitable for stopping when the traveling state judging means judges that the vehicle is stopped. The hydraulic motor drive circuit for traveling of the work vehicle according to claim 1. 4. The traveling state determining means determines the traveling state of the vehicle based on a signal from the operation amount detecting means and a signal from the speed detecting means. Hydraulic motor drive circuit for traveling of the work vehicle of. 5. A pair of pressure detection means is provided between the hydraulic motor and the control valve in the middle of the pair of main pipelines, and the traveling state determination means is provided with a signal from each pressure detection means. The hydraulic motor drive circuit for the traveling of the work vehicle according to claim 1, wherein the traveling state of the vehicle is determined based on a signal from the operation amount detecting means and a signal from the speed detecting means. 6. A counterbalance valve is provided between the hydraulic motor and the control valve in the middle of the pair of main pipelines, and the relief pressure setting means is provided between the counterbalance valve and the hydraulic motor. The hydraulic circuit drive circuit for traveling of the work vehicle according to claim 1, 2, 3, 4, or 5, which is located and provided in the middle of each of the main pipelines. 7. The relief pressure setting means is disposed between the counter balance valve and the hydraulic motor and is arranged between the pair of main pipelines, and selects the pressure oil on the high pressure side of the respective main pipelines. A high pressure selection valve, and a relief valve of a set pressure variable type, which is provided in the middle of a tank pipe line connecting the high pressure selection valve with a tank and variably sets a relief pressure by a control signal from the control signal output means. The traveling hydraulic motor drive circuit for a work vehicle according to claim 6, which is configured. 8. The pair of overload relief valves disposed between the counterbalance valve and the hydraulic motor and disposed between the pair of main pipelines, and the respective overload relief pressure setting means. 7. The hydraulic motor drive circuit for traveling of the work vehicle according to claim 6, comprising a variable pressure control valve that variably controls the relief pressure of the relief valve by a control signal from the control signal output means.