JP2007276532A - Steering control device for work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering control device for a work vehicle, in which the strength of a component device such as a steering actuator and a valve can be set lower. <P>SOLUTION: The device is provided with a hydraulic pump 1, steering cylinders 2 and 3 driven by hydraulic oil discharged from the hydraulic pump 1, a valve 4 to control the flow of hydraulic oil supplied from the hydraulic pump 1 to the steering cylinders 2 and 3, a steering wheel 5 to change the valve 4, and a variable relief valve 6 to regulate the discharging pressure of the hydraulic pump 1. The device is also provided with pressure sensors 9 and 10 to detect the negative pressure of the steering cylinders 2 and 3, and a regulation means to regulate the magnitude of the set pressure of the variable relief valve 6 according to the negative pressure detected by the pressure sensors 9 and 10. The regulation means includes a solenoid valve 7 to control the set pressure of the variable relief valve 6, and a controller 11 to control the solenoid valve. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a work vehicle steering control device that is provided in a work vehicle such as a wheel loader or a wheel excavator and controls a steering actuator.

  There exists a thing shown by patent document 1 as this type of prior art. This prior art is supplied to a hydraulic pump, a relief valve for defining the discharge pressure of the hydraulic pump, a steering actuator driven by pressure oil discharged from the hydraulic pump, that is, a steering cylinder, and the hydraulic pump to the steering cylinder. The valve includes a valve that controls the flow of pressure oil, and a steering wheel that switches the valve, that is, a steering handle.

The valve is switched by turning the steering handle, and the pressure oil discharged from the hydraulic pump is supplied to the steering cylinder through the valve, whereby the vehicle body or the wheel is bent in either the left or right direction. .
JP-A-4-228371

  In this type of work vehicle, a large steering force is required when the steering handle is turned largely from a stopped state and the work vehicle is bent, for example, to the maximum in either the left or right direction. That is, the force against the load pressure of the steering cylinder is increased. In particular, a large steering force is required when turning the steering wheel as much as possible from a stopped state in which the brake device is operating to bend the work vehicle greatly.

  Therefore, conventionally, the set pressure of the relief valve is determined in consideration of a large steering force when the steering handle is rotated to the maximum. For this reason, the strength design of apparatus components such as valves and steering cylinders becomes strict, and the manufacturing cost of these apparatus components tends to increase. It should be noted that when the steering wheel is turned less or when traveling, the steering force, that is, the force that resists the load pressure of the steering cylinder, can be small even if the brake device is in operation. There is a tendency.

  The present invention has been made from the above-described prior art, and an object of the present invention is to provide a steering control device for a work vehicle capable of setting the strength of device components such as a steering actuator and a valve low. is there.

  In order to achieve this object, the present invention controls a hydraulic pump, a steering actuator driven by pressure oil discharged from the hydraulic pump, and a flow of pressure oil supplied from the hydraulic pump to the steering actuator. In a steering control device for a work vehicle comprising a valve, a steering handle for switching the valve, and a relief valve for regulating a discharge pressure of the hydraulic pump, the relief valve is a variable relief valve and a load on the steering actuator It is characterized by comprising detection means for detecting pressure and adjustment means for adjusting the magnitude of the set pressure of the variable relief valve in accordance with the load pressure detected by the detection means.

  In the present invention configured as described above, for example, when the steering handle is rotated to the maximum from the stop state, and the load pressure corresponding to the pressure oil pressure supplied to the steering actuator becomes high, the load pressure is detected by the detecting means. It is detected and adjusted by the adjusting means so that the set pressure of the variable relief valve is increased in accordance with the high load pressure detected by the detecting means. Further, for example, when the steering handle is slightly turned from the stopped state or when traveling, the load pressure of the steering actuator is relatively low. The load pressure is detected by the detection means, and is adjusted by the adjustment means so that the set pressure of the variable relief valve is lowered according to the low load pressure detected by the detection means. Therefore, it is not necessary to design the strength of the apparatus constituent devices such as the steering actuator and the valve so as to always withstand the maximum load pressure of the steering actuator, and this strength can be set low.

  The present invention also provides a hydraulic pump, a steering actuator driven by pressure oil discharged from the hydraulic pump, a valve for controlling the flow of pressure oil supplied from the hydraulic pump to the steering actuator, and the valve. A steering control device for a work vehicle having a steering handle for switching and a relief valve for defining a discharge pressure of the hydraulic pump, comprising a device related to a load pressure of the steering actuator, wherein the relief valve is a variable relief valve And detecting means for detecting the state of the device, and adjusting means for adjusting the magnitude of the set pressure of the variable relief valve in accordance with the state of the device detected by the detecting means. It is said.

  In the present invention configured as described above, for example, when the steering handle is rotated to the maximum from the stop state, and the load pressure corresponding to the pressure oil pressure supplied to the steering actuator becomes high, the load pressure is accordingly increased. It is detected by the detection means that the state of the device such as the brake device related to the high pressure is detected, and the variable relief valve is set according to the state of the device such as the brake device detected by the detection device. The pressure is adjusted by the adjusting means so as to increase the pressure. Further, for example, when the steering handle is slightly turned from the stopped state or when traveling, the load pressure of the steering actuator is relatively low. Accordingly, it is detected by the detection means that the state of the device related to the load pressure corresponds to a low load pressure, and the variable relief valve is set according to the state of the device detected by the detection means. The pressure is adjusted by the adjusting means so that the pressure is lowered. Therefore, it is not necessary to design the strength of the apparatus constituent devices such as the steering actuator and the valve so as to always withstand the maximum load pressure of the steering actuator, and this strength can be set low.

  Further, the present invention is the above-described invention provided with a device related to the load pressure of the steering actuator, wherein the device related to the load pressure of the steering actuator comprises a brake device that brakes a wheel, and the detection means includes the brake The adjusting means detects whether or not the brake device is in an operating state by the detecting means, and sets the set pressure of the variable relief valve to a predetermined value. The pressure is adjusted to a high pressure value, and when the detecting means detects that the brake device is not in an operating state, the set pressure of the variable relief valve is adjusted to a predetermined pressure value lower than the predetermined high pressure value. It is characterized by comprising means.

  Further, the present invention is the above invention comprising a device related to the load pressure of the steering actuator, wherein the detection means comprises a pressure sensor for detecting the brake pressure of the brake device, and the adjustment means is the variable relief valve. And a controller for controlling the solenoid valve in accordance with a detection value of the pressure sensor.

  In addition, the present invention includes the travel detection means in the above invention, and invalidates the adjustment by the adjustment means when the travel detection means detects that the vehicle is in the travel state, and sets the set pressure of the variable relief valve. Is provided with means for maintaining the pressure at a predetermined low pressure value.

  Since the present invention is provided with the adjusting means for adjusting the set pressure of the variable relief valve according to the load pressure of the steering actuator, the discharge pressure of the hydraulic pump according to the maximum load pressure of the steering actuator is always supplied to the steering actuator. This makes it possible to set the strength of the apparatus constituent devices such as the steering actuator and the valve to be lower than the conventional one. Along with this, the manufacturing cost can be made lower than before.

  Further, the present invention is provided with the adjusting means for adjusting the set pressure of the variable relief valve according to the state of the equipment related to the load pressure of the steering actuator, so that the discharge pressure of the hydraulic pump according to the maximum load pressure of the steering actuator. Is not always supplied to the steering actuator, which makes it possible to set the strength of the apparatus constituent devices such as the steering actuator and the valve to be lower than the conventional one. Along with this, the manufacturing cost can be made lower than before.

  The best mode for carrying out a steering control device for a work vehicle according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a hydraulic circuit diagram showing a first embodiment of a steering control device for a work vehicle according to the present invention.

  As shown in FIG. 1, a first embodiment of the present invention is provided in a work vehicle such as a wheel loader, and includes a hydraulic pump 1 and a steering actuator that is driven by pressure oil discharged from the hydraulic pump 1, For example, a steering cylinder 2 and 3 that bends the above-mentioned front side part in the left-right direction of a vehicle body that is divided into two parts, a front side part and a rear side part, that are connected to each other via a pin, and from the hydraulic pump 1 to the steering cylinder 2 3 is provided with a valve 4 for controlling the flow of pressure oil supplied to 3 and a steering handle 5 for switching the valve 4.

  In particular, in the first embodiment, the relief valve that defines the discharge pressure of the hydraulic pump 1 is composed of the variable relief valve 6. Further, detection means for detecting the load pressure of the steering cylinders 2 and 3, for example, pressure sensors 9 and 10 are provided. Furthermore, an adjusting means for adjusting the set pressure of the variable relief valve 6 according to the load pressure detected by the pressure sensors 9 and 10 is provided. This adjusting means includes, for example, an electromagnetic valve 7 that is connected to the pilot pump 8 and controls the set pressure of the variable relief valve 6, and a controller 11 that controls the electromagnetic valve 7 according to the detection values of the pressure sensors 9 and 10. Yes. In the controller 11, for example, a predetermined threshold value for setting the set pressure of the variable relief valve 6 to a predetermined high pressure value is stored in advance.

  In the first embodiment, for example, when the wheel loader is stopped, the steering handle 5 is rotated as much as possible, so that the load pressure corresponding to the pressure of the pressure oil supplied to the steering cylinder 2 or 3 is increased. Then, the load pressure is detected by the pressure sensor 9 or 10, and the corresponding detection value is output to the controller 11.

  The controller 11 compares the input detection value with the predetermined threshold value described above. For example, when the detection value is equal to or higher than the predetermined threshold value, the set pressure of the variable relief valve 6 is set to a predetermined high pressure value in the electromagnetic valve 7. When the detected value is smaller than a predetermined threshold value, a control signal for setting the set pressure of the variable relief valve 6 to a predetermined pressure value lower than the predetermined high pressure value is output to the electromagnetic valve 7. To do. In this case, the steering handle 5 is turned to the maximum to the maximum, and the load pressure of the steering cylinder 2 or 3 becomes a high load pressure, and the detection value detected by the pressure sensor 9 or 10 is not less than a predetermined threshold value. Therefore, a control signal for setting the set pressure of the variable relief valve 6 to a predetermined high pressure value is output to the electromagnetic valve 7. As a result, the electromagnetic valve 7 is driven, the pilot pressure of the pilot pump 8 is supplied to the control unit of the variable relief valve 6 via the electromagnetic valve 7, and the set pressure of the variable relief valve 6 is controlled to a predetermined high pressure value. The Accordingly, the discharge pressure of the hydraulic pump 1 is increased, and sufficient pressure oil is supplied to the steering cylinders 2 and 3 to bend the front portion of the vehicle body to the left or right.

  Further, for example, when the steering wheel 5 is slightly turned from a state where the wheel loader is stopped, or when traveling, the load pressure of the steering cylinder 2 or 3 is relatively low. The load pressure is detected by the pressure sensor 9 or 10. This detected value is smaller than a predetermined threshold value stored in the controller 11. Therefore, a control signal for setting the set pressure of the variable relief valve 6 from the controller 11 to a predetermined pressure value lower than the predetermined high pressure value described above is output to the electromagnetic valve 7. As a result, the solenoid valve 7 is driven, the pilot pressure of the pilot pump 8 is supplied to the control unit of the variable relief valve 6 via the solenoid valve 7, and the set pressure of the variable relief valve 6 is higher than the predetermined high pressure value described above. Controlled to a low predetermined pressure value.

  Therefore, although the pressure of the pressure oil supplied to the steering cylinder 2 or 3 is low, the steering cylinder 2 or 3 has sufficient pressure oil or travel to bend the front portion of the vehicle body slightly leftward or rightward. Sometimes enough pressure oil is supplied to bend the front part of the car body in the left-right direction.

  According to the first embodiment configured as described above, the strength of the device components such as the steering cylinders 2 and 3 and the valve 4 should not be designed to be large enough to always withstand the maximum load pressure of the steering cylinders 2 and 3. This strength can be set low. This can reduce the manufacturing cost.

  FIG. 2 is a hydraulic circuit diagram showing a second embodiment of the present invention, and FIG. 3 is a diagram showing a relationship between a brake pressure set by a controller provided in the second embodiment shown in FIG. 2 and an output signal to an electromagnetic valve. It is.

  The second embodiment of the present invention shown in FIGS. 2 and 3 is also provided in, for example, a wheel loader, and is equivalent to the hydraulic pump 1, steering cylinders 2 and 3, valve 4, and steering that are equivalent to the first embodiment described above. A handle 5, a variable relief valve 6, a solenoid valve 7, a pilot pump 8, and a controller 11 are provided.

  In particular, the second embodiment includes a device related to the load pressure of the steering actuator, that is, the steering cylinders 2 and 3, for example, a brake device including a front wheel brake device 12 and a rear wheel brake device 13 for braking the wheel, A detecting means for detecting the state of the brake device, for example, a pressure sensor 16 for detecting a brake pressure supplied to the front wheel brake device 12 is provided. When the front wheel brake device 12 is in an actuated state, that is, in a brake state, the load pressure on the steering cylinders 2 and 3 increases when the front side portion of the vehicle body is bent to the left or right. That is, the brake device including the front wheel brake device 12 is a device greatly related to the load pressure of the steering cylinders 2 and 3.

  The second embodiment also includes a brake valve 14 for controlling the brake pressure supplied to the front wheel brake device 12 and the rear wheel brake device 13, a predetermined brake pressure, and the surplus pressure to other circuits. And a charge valve 15 that enables supply to the battery.

  In addition, the second embodiment includes an adjusting unit that adjusts the magnitude of the set pressure of the variable relief valve 6 in accordance with the state of the front wheel brake device 12 detected by the pressure sensor 16. This adjusting means adjusts the set pressure of the variable relief valve 6 to a predetermined high pressure value when the pressure sensor 16 detects that the front wheel brake device 12 is in an operating state, that is, in a brake state. When it is detected that the front wheel brake device 12 is not in the operating state, that is, in the brake released state, the set pressure of the variable relief valve 6 is adjusted to a predetermined pressure value lower than the predetermined high pressure value. It consists of adjustment means. This adjusting means includes the electromagnetic valve 7 and the controller 11 described above.

  The controller 11 stores in advance the relationship between the brake pressure shown in FIG. 3 and the output signal of the solenoid valve 7, that is, the control signal. As shown in FIG. 3, when the brake pressure exceeds a predetermined high value A, the control signal to the electromagnetic valve 7 becomes an ON signal. When the brake pressure is smaller than a predetermined high value A, the control signal to the solenoid valve 7 is an off signal. In addition, once the brake pressure becomes equal to or higher than the predetermined high value A, the control signal of the electromagnetic valve 7 is held at the ON signal unless the brake pressure becomes a value B sufficiently lower than the predetermined high value A. The control signal of the solenoid valve 7 is set to be an off signal when the value becomes equal to or less than the predetermined value B. Thus, the value B is set in order to ensure the stability of the control, that is, to form a dead zone.

  In the second embodiment, for example, when the wheel loader is in a stopped state and the front wheel brake device 12 is in an activated state, that is, in a brake state, the steering cylinder 5 is rotated to the maximum. When the load pressure corresponding to the pressure oil pressure supplied to the steering cylinder 2 or 3 is increased thereby, the state of the front wheel brake device 12 which is a device related to the load pressure is increased. It is detected by the pressure sensor 16 that a high brake pressure corresponding to is supplied, and the detected value of the pressure sensor 16 is output to the controller 11.

  The controller 11 compares the input detected value with the predetermined high value A shown in FIG. 3. When the detected value is equal to or higher than the predetermined high value A, for example, the set pressure of the variable relief valve 6 is applied to the electromagnetic valve 7. When a control signal composed of an ON signal for setting a predetermined high pressure value is output and the detected value is lower than a predetermined high value A, the set pressure of the variable relief valve 6 for the electromagnetic valve 7 is lower than the predetermined high pressure value. A control signal composed of an off signal with a predetermined pressure value is output. In this case, the steering wheel 5 is turned as far as possible to the maximum, and the front wheel brake device 12 is in an operating state where the load pressure of the steering cylinder 2 or 3 is high. The detected value detected by the pressure sensor 16 is Since the value is equal to or higher than the predetermined high value A in FIG. 3, a control signal including an ON signal for setting the set pressure of the variable relief valve 6 to a predetermined high pressure value is output to the electromagnetic valve 7.

  Thus, the solenoid valve 7 is driven, the pilot pressure of the pilot pump 8 is supplied to the control unit of the variable relief valve 6 via the solenoid valve 7, and the set pressure of the variable relief valve 6 is controlled to a predetermined high pressure value. The Accordingly, in the second embodiment, the discharge pressure of the hydraulic pump 1 is increased in the same manner as in the first embodiment described above, and is sufficient to bend the front portion of the vehicle body greatly leftward or rightward via the valve 4. Pressure oil is supplied to the steering cylinders 2 and 3.

  In such a state, in a state where the detection value of the pressure sensor 16 does not reach the predetermined value B even when the detection value becomes lower than the predetermined high value A, a control signal composed of an ON signal is continuously output to the electromagnetic valve 7, The set pressure of the variable relief valve 6 is held so as to be a predetermined high pressure value.

  Further, for example, when the wheel loader is stopped and the front wheel brake device 12 is not operated, that is, when the steering handle 5 is slightly turned from the state where the brake is released. When traveling, the load pressure of the steering cylinder 2 or 3 is relatively low. The pressure sensor 16 detects that the state of the front wheel brake device 12 related to the load pressure is a state where the brake pressure is maintained at a low brake pressure. This detected value is smaller than a predetermined high value A stored in the controller 11. Therefore, the controller 11 outputs a control signal including an off signal that sets the set pressure of the variable relief valve 6 to a predetermined pressure value lower than the above-described high pressure value. As a result, the solenoid valve 7 is driven, the pilot pressure of the pilot pump 8 is supplied to the control unit of the variable relief valve 6 via the solenoid valve 7, and the set pressure of the variable relief valve 6 is lower than a predetermined high pressure value. Pressure value. Accordingly, in the second embodiment as well, the pressure oil supplied to the steering cylinder 2 or 3 is reduced in the same manner as in the first embodiment described above, but the front portion of the vehicle body is attached to the steering cylinder 2 or 3. Pressure oil sufficient to bend slightly to the left or right is supplied, or sufficient pressure oil to bend the front portion of the vehicle body in the left-right direction during travel.

  Even in the second embodiment configured as described above, the strength of the device components such as the steering cylinders 2 and 3 and the valve 4 is always set to the maximum of the steering cylinders 2 and 3 as in the first embodiment described above. It is not necessary to design a large strength that can withstand the load pressure, and this strength can be set low. This can reduce the manufacturing cost.

  In the first and second embodiments, the travel detection means is provided, and when the travel detection means detects that the vehicle is in the travel state, the adjustment by the adjustment means described above is invalidated, and the variable relief valve The controller 11 may include a means for holding the set pressure 6 at a predetermined low pressure value, for example, a means for outputting a control signal including the off signal shown in FIG.

1 is a hydraulic circuit diagram illustrating a first embodiment of a steering control device for a work vehicle according to the present invention. It is a hydraulic circuit diagram which shows 2nd Embodiment of this invention. It is a figure which shows the relationship between the brake pressure set by the controller with which 2nd Embodiment shown in FIG. 2 is provided, and the output signal to a solenoid valve.

Explanation of symbols

1 Hydraulic pump 2 Steering cylinder (steering actuator)
3 Steering cylinder (steering actuator)
4 Valve 5 Steering handle 6 Variable relief valve 7 Solenoid valve (adjustment means)
8 Pilot pump 9 Pressure sensor (detection means)
10 Pressure sensor (detection means)
11 Controller (Adjustment means)
12 Brake device for front wheel 13 Brake device for rear wheel 16 Pressure sensor (detection means)

Claims (5)

A hydraulic pump; a steering actuator driven by pressure oil discharged from the hydraulic pump; a valve for controlling a flow of pressure oil supplied from the hydraulic pump to the steering actuator; a steering handle for switching the valve; In a steering control device for a work vehicle including a relief valve that regulates a discharge pressure of a hydraulic pump,
The relief valve consists of a variable relief valve,
Detecting means for detecting a load pressure of the steering actuator;
A steering control device for a work vehicle, comprising: adjusting means for adjusting the set pressure of the variable relief valve according to the load pressure detected by the detecting means. A hydraulic pump; a steering actuator driven by pressure oil discharged from the hydraulic pump; a valve for controlling a flow of pressure oil supplied from the hydraulic pump to the steering actuator; a steering handle for switching the valve; In a steering control device for a work vehicle including a relief valve that regulates a discharge pressure of a hydraulic pump,
It has equipment related to the load pressure of the steering actuator,
The relief valve consists of a variable relief valve,
Detecting means for detecting the state of the device;
A steering control device for a work vehicle, comprising: an adjusting unit that adjusts a set pressure of the variable relief valve in accordance with the state of the device detected by the detecting unit. In the invention of claim 2,
The equipment related to the load pressure of the steering actuator comprises a brake device for braking the wheel,
The detection means consists of detecting whether or not the brake device is in an operating state,
When the detecting means detects that the brake device is in the operating state, the adjusting means adjusts the set pressure of the variable relief valve to a predetermined high pressure value, and the detecting means operates the brake device. A steering control device for a work vehicle, comprising means for adjusting a set pressure of the variable relief valve to a predetermined pressure value lower than the predetermined high pressure value when it is detected that the state is not in a state. In the invention of claim 3,
The detection means comprises a pressure sensor for detecting the brake pressure of the brake device,
The adjusting means is
A steering control device for a work vehicle, comprising: a solenoid valve that controls a set pressure of the variable relief valve; and a controller that controls the solenoid valve according to a detection value of the pressure sensor. In the invention according to any one of claims 1 to 4,
While having a traveling detection means,
And a means for invalidating the adjustment by the adjusting means and holding the set pressure of the variable relief valve at a predetermined low pressure value when the running detecting means detects that the vehicle is in a running state. A steering control device for a working vehicle.

Images