JPH11334635A - Power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit a steering which might cause the vehicle motion to be unstable while turning. SOLUTION: A control valve 20, in response to a steering input from a steering 21, supplies and drains hydraulic fluid that is supplied from a hydraulic pump 17 to a pair of oil chambers R1 and R2 of a hydraulic pump cylinder 19. On pipe lines 29, 30 that connect each of supply and drain ports 24A, 24B to each of oil chambers R1, R2, solenoid open/close valves 38, 39 are provided that can shut off supplying and draining of the hydraulic fluid, respectively. A vehicle speed V and a steering angle θ are detected. When the vehicle speed V is at or greater than vehicle speed judgement values V1, V2 and the steering angle θ is at or greater than steering angle judgement values θ1, θ2, the solenoid open/close valves 38, 39 to the side of supplying the hydraulic fluid to the hydraulic power cylinder 19 are closed. In the meantime, oil pressures PL, PR of each of the oil chambers R1, R2 of the hydraulic power cylinder 19 are judged with an oil judgement value P0. When the steering is judged to be steered to straight-ahead, the solenoid open/close valves 38, 39 that have been closed are opened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-hydraulic power steering device used for a forklift or the like.

[0002]

2. Description of the Related Art Conventionally, for example, an engine type forklift, which is a cargo handling vehicle, includes an all-hydraulic power steering device. This power steering device includes a control valve that supplies and discharges hydraulic oil supplied from a hydraulic pump by an amount of oil corresponding to a steering input from a steering, and a control valve that steers steered wheels by using hydraulic oil supplied and discharged by the control valve. And a dynamic hydraulic power cylinder. The hydraulic pressure and flow rate of the hydraulic oil supplied from the hydraulic pump are adjusted within a predetermined range by a valve built in the hydraulic pump.

When the steering is steered, the control valve supplies an amount of hydraulic oil corresponding to the steering input to one oil chamber of the double-acting cylinder and discharges the same amount of hydraulic oil from the other oil chamber. You. Then, the steered wheels are steered by a steering assist force based on the hydraulic pressure of the hydraulic oil supplied from the hydraulic pump. Therefore, the steered wheels are steered by the steering assist force based on the hydraulic pressure generated by the hydraulic pump, regardless of the vehicle speed and the steering angle of the steered wheels.

[0004]

However, in a vehicle equipped with such a power steering device, when the vehicle is steered at a high steering speed at the same steering speed as when the vehicle speed is low, the steering angle of the steered wheels is increased. Became too large with respect to the vehicle speed, and the vehicle sometimes turned with a turning radius smaller than expected. As a result, the vehicle body may be tilted more than expected due to lateral acceleration and the vehicle may become unstable. Furthermore, the loading state of the load may become unstable due to the tilting or wobbling of the vehicle body.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to limit steering in which a vehicle body becomes unstable during turning in a fully hydraulic power steering device. A power steering device is provided.

[0006]

According to a first aspect of the present invention, a hydraulic oil supplied from a hydraulic pump is supplied to a hydraulic power cylinder in response to a steering input from a steering. In a fully hydraulic power steering device in which the steered wheels are steered left and right by the hydraulic power cylinder, the magnitude of the lateral acceleration applied to the vehicle at the time of turning based on the steering input does not become larger than a predetermined magnitude. There is provided a supply / discharge limiting means for limiting an amount of hydraulic oil supplied to the hydraulic power cylinder in accordance with a steering input of the steering.

According to a second aspect of the present invention, there is provided a hydraulic pump which is driven by a power source and supplies hydraulic oil in a predetermined range of oil pressure and oil amount, and is operated by a steering input from a steering wheel and supplied from the hydraulic pump. Hydraulic oil supply / discharge control means capable of supplying the hydraulic oil to the outside in accordance with the steering input while distinguishing the steering direction, and discharging the hydraulic oil of the same amount supplied from the outside to an external oil tank. A power steering system comprising: a pair of oil chambers to which hydraulic oil is supplied and discharged by the hydraulic oil supply and discharge control means; and a double-acting hydraulic power cylinder that steers steered wheels by supplying and discharging hydraulic oil to and from each oil chamber. A traveling state amount detecting means for detecting a traveling state amount of the vehicle detected according to a magnitude of a lateral acceleration applied to the vehicle at the time of turning; and a steering direction detection for detecting a steering direction of the steering. Means, flow rate limiting means capable of limiting the amount of hydraulic oil supplied from the hydraulic oil supply / discharge means to the hydraulic power cylinder, and a determination value preset for the traveling state quantity, The amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder by the right or left steering input is limited so that the lateral acceleration does not exceed a predetermined value corresponding to the determination value. While controlling the flow rate limiting means, based on the detection result of the steering direction detecting means, determine whether the steering input to the steering has been in the opposite direction as before, the steering input is in the direction opposite to the previous. When it becomes
Steering control means for controlling the flow rate limiting means so as not to limit the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder.

According to a third aspect of the present invention, in addition to the operation of the second aspect, the traveling state quantity is a combination of a vehicle speed and a steering angle, and the traveling state quantity detecting means includes: It comprises a vehicle speed detection means and a steering angle detection means, wherein the steering control means, when the vehicle speed is equal to or greater than a predetermined vehicle speed determination value, and when the steering angle is equal to or greater than a predetermined steering angle determination value,
The flow rate limiting means is controlled so as to limit the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder.

According to a fourth aspect of the present invention, in addition to the function of the second or third aspect, the hydraulic oil supply / discharge control means is a control valve, and the flow rate limiting means is The control valve is an electromagnetically operated on-off valve provided on at least one of a pair of flow paths for supplying and discharging hydraulic oil to and from each oil chamber of the hydraulic power cylinder, and the steering control means includes: The supply of hydraulic oil to the hydraulic power cylinder is allowed or cut off by controlling the electromagnetically operated on-off valve to a fully open state or a fully closed state.

According to a fifth aspect of the present invention, in addition to the function of the second aspect of the present invention, the electromagnetically operated on-off valve is configured such that the control valve is provided in each of the hydraulic cylinders. The steering direction detection means is provided in each of a pair of flow paths for supplying and discharging hydraulic oil to and from an oil chamber, and the steering direction detection means detects oil pressure in each oil chamber of the hydraulic power cylinder; Steering direction determining means for determining the direction of the steering input to the steering based on
When the steering direction determining unit determines that the steering direction of the steering has been changed to the opposite direction, the steering control unit releases the restriction on the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder. The flow restricting means is controlled so as to be controlled.

According to a sixth aspect of the present invention, in addition to the operation of the second aspect of the invention, a lift detecting means for detecting a lift position of a fork in a forklift, Load detecting means for detecting the load of the load loaded on the fork, the steering control means,
Based on each preliminary determination value preset for a combination of the elevation position and the load corresponding to the magnitude of the centrifugal force that tries to tilt the vehicle body during turning according to the position of the center of gravity of the vehicle in the vertical direction, When the centrifugal force is equal to or greater than the magnitude corresponding to each of the preliminary determination values, the centrifugal force controls the flow rate limiting unit based on a first determination value set in advance for the value of the traveling state amount, and When the force is smaller than the magnitude corresponding to each of the preliminary determination values, the second determination that is set in advance for the value of the traveling state amount corresponding to the centrifugal force having a magnitude smaller than the first determination value. The flow rate limiting means is controlled based on the value. (Operation) According to the first aspect of the present invention, hydraulic oil is supplied to and discharged from the hydraulic power cylinder in response to a steering input from the steering wheel, and the hydraulic power cylinder causes the steered wheels to be steered according to the steering input. Steered by. When the lateral acceleration applied to the vehicle at the time of turning based on the steering input becomes larger than a predetermined magnitude, the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder is limited by the supply / discharge limiting means, and the steering amount is controlled. Limited for input.

According to the second aspect of the present invention, hydraulic oil in a predetermined range of hydraulic pressure and oil amount supplied from the hydraulic pump is supplied to and discharged from the hydraulic power cylinder in response to a steering input from the steering, and is driven. The wheels are steered by the hydraulic power cylinder by an operating amount in accordance with the steering input. The lateral acceleration at the time of turning of the vehicle is determined based on the traveling state amount, and the operation amount of the hydraulic power cylinder is limited so that the magnitude does not exceed a predetermined amount. Further, when the steering input in the state where the operation amount of the hydraulic power cylinder is limited is the steering input in the opposite direction, the operation of the hydraulic power cylinder is allowed.

According to the third aspect of the present invention, even if the vehicle shakes straight on an uneven road surface, the operation of the hydraulic power cylinder is limited based on the lateral acceleration applied to the vehicle due to the shake. Absent.

According to the invention described in claim 4, according to claim 2,
Alternatively, in addition to the effect of the third aspect of the invention, the supply and discharge of hydraulic oil to and from the hydraulic cylinder is allowed or restricted by the electromagnetically operated on-off valve.

According to the invention set forth in claim 5, according to claim 2,
In addition to the operation of the invention described in any one of the fourth to fourth aspects, the steering direction is determined based on the oil pressure of both oil chambers of the hydraulic power cylinder.

According to the invention of claim 6, according to claim 2,
In addition to the operation of the invention according to any one of claims 5 to 5, even if the magnitude of the lateral acceleration applied to the vehicle at the time of turning is the same, the center of gravity of the vehicle determined by the height of the load and the load is determined. When the vertical position is relatively low and the magnitude of the centrifugal force for tilting the vehicle body during turning is relatively small, the operation of the hydraulic power cylinder is permitted.
On the other hand, when the position of the center of gravity is relatively high and the magnitude of the centrifugal force for tilting the vehicle body during turning becomes relatively large, the operation of the hydraulic power cylinder is restricted.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 2 is a side view showing the forklift 10 as a vehicle. The forklift 10 is provided with a differential (not shown) driven by an engine 11, a front wheel axle 13 (shown in FIG. 1) supporting a drive wheel 12 as a front wheel, and a steering device (not shown), and a rear wheel. And a rear wheel axle 15 (shown in FIG. 1) that supports the steered wheels 14.

The forklift 10 is provided with a fully hydraulic power steering device 16. FIG. 1 is a schematic configuration diagram of the power steering device 16. The power steering device 16 includes a hydraulic pump 17, an oil tank 18, a hydraulic power cylinder 19, a control valve 20 as hydraulic oil supply / discharge control means, and the like.

The hydraulic pump 17 is driven by the engine 11, sucks hydraulic oil in an oil tank 18 from the inlet side, controls the sucked hydraulic oil to a predetermined range of hydraulic pressure and flow rate by a built-in valve, and controls the control valve 20. To supply.

A steering 21 is mechanically connected to the control valve 20. Control valve 2
Reference numeral 0 denotes an introduction port 22 for introducing hydraulic oil supplied from the hydraulic pump 17, a discharge port 23 for discharging hydraulic oil to the outside, and a pair of ports for supplying and discharging the same amount of hydraulic oil to the outside. Supply and discharge ports 24A and 24B. The supply side of the hydraulic pump 17 is connected to the introduction port 22 via a pipe 25, and the discharge port 23 is connected to the oil tank 18 via a pipe 26.

The control valve 20 is operated by a right steering input or a left steering input from the steering 21 to supply the hydraulic oil supplied to the introduction port 22 with the operating oil.
According to each steering input, the steering direction is distinguished and the hydraulic power cylinder 1 is connected to one of the pair of supply / discharge ports 24A and 24B.
9 and the same amount of hydraulic oil discharged from the hydraulic power cylinder 19 as the same supply / discharge ports 24B, 24A.
And the oil tank 18 from the discharge port 23
To be discharged.

The hydraulic power cylinder 19 is a rear wheel axle 1
5. The hydraulic power cylinder 19 is of a double-acting type and includes a pair of oil chambers defined by a piston 28 in a cylinder tube 27, that is, a right oil chamber R1 and a left oil chamber R2. The supply / discharge port 24A is connected to the right oil chamber R1 via a pipe 29, and the supply / discharge port 24B is connected to the left oil chamber R2 via a pipe 30. A pressure sensor 31 is provided in the right oil chamber R1 as pressure detecting means for detecting the oil pressure of the oil chamber R1, and a pressure sensor as a pressure detecting means for detecting the oil pressure of the oil chamber R2 is provided in the left oil chamber R2. A sensor 32 is provided.

A steering rod 33 is provided on both sides of the piston 28.
A and 33B are provided, and the steering rods 33A and 33B protrude from each end of the cylinder tube 27 to the outside. The ends of the steering rods 33A and 33B are pin-connected via a lever 37 to a knuckle 36 that is supported by a king pin 35 and supports the rear wheel 14.

On the pipe line 29, there is provided a right electromagnetically operated on / off valve (hereinafter referred to as right electromagnetic on / off valve) 38 which permits or shuts off the supply of hydraulic oil from the supply / discharge port 24A of the control valve 20 to the right oil chamber R1. Is provided. Similarly, a left-side electromagnetically operated on-off valve (hereinafter referred to as a left-sided electromagnetic on-off valve) 39 for allowing or shutting off the supply of hydraulic oil from the supply / discharge port 24B to the left-side oil chamber R2 is provided on the conduit 30. . In the present embodiment, the flow rate restricting means is constituted by the electromagnetic on-off valves 38 and 39.

The right electromagnetic on-off valve 38 is a normally open type with two ports and two positions, and has an electromagnetic solenoid 40 that closes in an excited state. The left electromagnetic on / off valve 39 is the same as the right electromagnetic on / off valve 38, and includes an electromagnetic solenoid 41 that closes in an excited state.

The differential provided on the front wheel axle 13 is provided with a magnetic sensor 43 as vehicle speed detecting means for detecting the rotation speed of the ring gear 42 corresponding to the vehicle speed V of the vehicle.

The upper bracket (not shown) supporting the king pin 35 has a steering angle θ of the steered wheels 14, that is, a steering angle θ = 0 in a straight traveling state, and a positive right steering angle θR during right steering.
And a potentiometer 4 as a steering angle detecting means for detecting a turning angle of the king pin 35 corresponding to a steering angle θ corresponding to a positive left steering angle θL at the time of left steering, that is, an absolute turning angle.
4 are provided. In the present embodiment, the magnetic sensor 4
3 and the potentiometer 44 constitute a traveling state quantity detecting means.

Also, inside the vehicle body, each pressure sensor 31,
A control unit 45 is provided in which the magnetic sensor 32, the magnetic sensor 43, the potentiometer 44, and the electromagnetic solenoids 40 and 41 are electrically connected.

Next, the electrical configuration of the power steering apparatus configured as described above will be described with reference to the electrical block diagram shown in FIG. The pressure sensor 31 outputs an analog oil pressure signal SPR corresponding to the oil pressure PR of the right oil chamber R1,
The pressure sensor 32 outputs an analog oil pressure signal SPL corresponding to the oil pressure PL of the left oil chamber R2 to the control unit 45.
Output to The magnetic sensor 43 outputs a vehicle speed signal PV having a pulse width proportional to the vehicle speed V to the control unit 45. The potentiometer 44 controls the steering angle θ of the steered wheels 14, that is,
An analog steering angle signal Sθ corresponding to the right steering angle θR and the left steering angle θL is output to the control unit 45.

The control unit 45 includes microcomputers 50 and A as steering control means and steering direction judging means.
/ D converters 51, 52, 53 and a solenoid drive circuit 54 are provided. The microcomputer 50 includes a central processing unit (hereinafter, CPU 55), a read-only memory (ROM) 56, a writable and readable memory (RAM) 57, an input interface 58, and an output interface 59. Microcomputer 5
0 is the right steering restriction flag FSR and the left steering restriction flag F
SL is provided. In the present embodiment, the hydraulic pressure sensor 3
The steering direction detecting means is constituted by the microphones 1 and 32 and the microphone computer 50. Further, the hydraulic sensors 32, 3
3, right electromagnetically operated on-off valve 38, left electromagnetically operated on-off valve 3
9, the magnetic sensor 43, the potentiometer 44, and the microcomputer 50 constitute a supply / discharge restricting means.

The CPU 55 has a detection value of a hydraulic pressure PR output from the pressure sensor 31 via the A / D converter 51, a detection value of a hydraulic pressure PL output from the pressure sensor 32 via the A / D converter 52, a magnetic sensor A detection value of a steering angle θ output by the potentiometer 44 via the A / D converter 53 and a detection value of the steering angle θ output by the potentiometer 44 are input via the input interface 58. Also, the CPU 55
The excitation current Ie for exciting the electromagnetic solenoid 40 of the right solenoid on-off valve 38 and the excitation current Ie for exciting the electromagnetic solenoid 41 of the left solenoid on-off valve 39 are supplied to the solenoid drive circuit 54 via the output interface 59, respectively. Output.

The ROM 56 stores various program data including the program data of the steering regulation process shown in the flowcharts of FIGS. CPU 55
Repeatedly executes the steering restriction process at predetermined time intervals (for example, several tens of milliseconds).

The CPU 55 performs a steering regulation process based on a predetermined judgment value for a traveling state quantity of the vehicle corresponding to the magnitude of the lateral acceleration applied to the vehicle at the time of turning.
The amount of hydraulic oil supplied / discharged to / from the hydraulic power cylinder 19 by the right and left steering inputs of the steering 21 is limited so that the acceleration does not exceed a predetermined magnitude corresponding to each determination value. The two solenoid valves 38, 39
Control. In the present embodiment, a combination of the vehicle speed V and the steering angle θ is set as the traveling state quantity.

The CPU 55 performs a steering restriction process as follows.
Based on the detection results of the two pressure sensors 31 and 32, it is determined whether or not the steering input to the steering 21 is in the opposite direction, and when the steering input is in the opposite direction, the hydraulic pressure is determined. The two electromagnetic on-off valves 38 and 39 are controlled so that the amount of hydraulic oil supplied to and discharged from the power cylinder 19 is not limited. The traveling state quantity is a detection quantity for estimating the magnitude of the lateral acceleration applied to the vehicle at the time of turning. In the present embodiment, a combination of the vehicle speed V and the steering angle θ is employed.

The ROM 56 stores a first vehicle speed determination value V1 as a vehicle speed determination value with respect to the vehicle speed V constituting the running state quantity.
And a second vehicle speed determination value V2, which is larger than the first vehicle speed determination value V1, is also set. A first steering angle determination value θ1 as a steering angle determination value with respect to the steering angle θ is also set. The second steering angle, which is smaller than the first steering angle determination value θ1,
The steering angle determination value θ2 is set. Then, as a determination value of the traveling state quantity, a combination of the first vehicle speed determination value V1 and the first steering angle determination value θ1, and a second vehicle speed determination value V2
And the second steering angle determination value θ2.

This is because, when the vehicle speed V is relatively high and the steering angle θ is relatively small, the lateral acceleration applied to the vehicle at the time of turning is proportional to the square of the vehicle speed V and inversely proportional to the turning radius. Also, or even when the vehicle speed V is relatively low and the steering angle θ is relatively large, the magnitude of the lateral acceleration applied to the vehicle at the time of turning based on the steering becomes equal to or less than a predetermined magnitude. It is. In the present embodiment, the first vehicle speed V
Vehicle speed determination value V1 = 5 km, second vehicle speed determination value V2 = 10 k
m is set respectively, and the maximum value of the right and left steering angles is 80 °
In contrast, the first steering angle determination value θ1 = 40 ° and the second steering angle determination value θ2 = 20 ° are set.

The CPU 55 determines the steering direction of the steering 21 based on whether the detected steering angle θ of the steered wheels 14 is the right steering angle θR or the left steering angle θL as the steering restriction processing. When the steering is right steering, the CPU 55 determines whether the detected vehicle speed V is less than the first vehicle speed determination value V1, or is equal to or greater than the first vehicle speed determination value V1 and the second vehicle speed determination value V2.
It is determined whether the value is less than or equal to or greater than the second vehicle speed determination value V2. When the vehicle speed V is less than the first vehicle speed determination value V1, the CPU 55 determines whether or not the right steering input that maximizes the right steering angle θ is applied to the control valve 20 from the steering 21 at the right steering angle θ. It is determined that the lateral acceleration applied to the vehicle body during a right turn does not become larger than a predetermined magnitude at which the vehicle becomes unstable.

Further, the CPU 55 performs a steering restriction process as follows.
When the detected vehicle speed V is equal to or greater than the second vehicle speed determination value V2, it is determined whether the detected right steering angle θ is equal to or greater than the second steering angle determination value θ2. The CPU 55 determines that the vehicle speed V is the second
If the right steering angle θ is equal to or greater than the second steering angle determination value θ2 when the vehicle speed determination value is equal to or greater than V2, a steering input that sets the right steering angle θ to be equal to or greater than the second steering angle determination value θ2 is performed by the control valve 20. Is determined, it is determined that the lateral acceleration applied to the vehicle body during the right turn is equal to or larger than a predetermined magnitude at which the vehicle becomes unstable.

On the other hand, even when the vehicle speed V is equal to or greater than the second vehicle speed determination value V2, the CPU 55 determines that the right steering angle θ is less than the second steering angle determination value θ2. Second
Even if a steering input that is less than the steering angle determination value θ2 is applied to the control valve 20, it is determined that the lateral acceleration applied to the vehicle body at the time of turning right does not exceed a predetermined magnitude at which the vehicle becomes unstable.

The CPU 55 performs a steering restriction process as follows.
If the detected vehicle speed V is equal to or greater than the first vehicle speed determination value V1 and the second vehicle speed V
If it is less than the vehicle speed determination value V2, it is determined whether or not the detected right steering angle θ is equal to or greater than a first steering angle determination value θ1 set to a value larger than the second steering angle determination value θ2.
When the vehicle speed V is equal to or greater than the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2, if the right steering angle θ is equal to or greater than the first steering angle determination value θ1, It is determined that the lateral acceleration applied to the vehicle body is equal to or larger than a predetermined magnitude at which the vehicle becomes unstable.

On the other hand, the CPU 55 determines that the right steering angle θ is less than the first steering angle determination value θ1 even when the vehicle speed V is equal to or greater than the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2. In such a case, it is determined that the lateral acceleration applied to the vehicle body during the right turn does not exceed a predetermined magnitude at which the vehicle becomes unstable.

Further, the CPU 55 performs a steering restriction process as follows.
When the acceleration applied to the vehicle body during a right turn is less than a predetermined magnitude at which the vehicle becomes unstable, that is, when the vehicle speed V is less than the first vehicle speed determination value V1, the vehicle speed V is equal to or greater than the second vehicle speed determination value V2. When the right steering angle θ is less than the second steering angle determination value θ2, and when the vehicle speed V is equal to or more than the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2, and the right steering angle θ is the first steering angle determination value θ1. If it is less than the right, the right steering restriction flag FSR is set to “0”.

On the other hand, the CPU 55 determines that the acceleration applied to the vehicle body at the time of turning right is equal to or larger than a predetermined value at which the vehicle becomes unstable, that is, the vehicle speed V is increased to the second speed as the steering restriction processing.
The right steering angle θ is equal to or greater than the second steering angle determination value θ at the vehicle speed determination value V2 or more.
When the vehicle speed V is greater than or equal to 2, and when the vehicle speed V is greater than or equal to the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2 and the right steering angle θ is greater than or equal to the first steering angle determination value θ1, It is determined whether or not the hydraulic pressure determination value P0 is exceeded. CP
When the hydraulic pressure PR is equal to or less than the hydraulic pressure determination value P0, U55 determines that there is a possibility that a right steering input that makes the vehicle unstable may be applied from the steering 21, and the steering is performed in order to restrict right steering by the steering input. The restriction flag FSR is set to “1”. On the other hand, when the oil pressure PR exceeds the oil pressure determination value P0, the CPU 55 determines that a left steering input for reducing the unstable state of the vehicle is being applied from the steering 21 and allows the left steering by the steering input. To this end, the right steering restriction flag FSR is set to “0”.

When the steering direction is left steering, the CPU 55 performs the same control as when the steering direction is right steering. That is, the CPU 55 determines that the vehicle speed V is the first vehicle speed determination value V1.
Is less than the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2, or the second vehicle speed determination value V
It is determined whether it is two or more. Further, the CPU 55
Determines whether the left steering angle θ is equal to or greater than the second steering angle determination value θ2 when the vehicle speed V is equal to or greater than the second vehicle speed determination value V2, and determines whether the vehicle speed V is equal to or greater than the first vehicle speed determination value V1 and When the vehicle speed is less than the vehicle speed determination value V2, the left steering angle θ is equal to the first steering angle θ1.
It is determined whether or not this is the case.

Then, as a steering restriction process, the CPU 55 determines that the acceleration applied to the vehicle body at the time of turning to the left is smaller than a predetermined magnitude at which the vehicle becomes unstable, that is, the vehicle speed V becomes the first speed.
When the vehicle speed V is less than the vehicle speed determination value V1, the vehicle speed V becomes the second vehicle speed determination value V
When the left steering angle θ is less than the second steering angle determination value θ2 when the left steering angle θ is less than the second steering speed determination value V2 and when the left steering angle θ is less than the second vehicle speed determination value V2, the left steering angle θ is less than the first steering angle determination value θ2. Value θ1
If it is less than the predetermined value, the left steering restriction flag FSL is set to “0”.

Further, the CPU 55 performs a steering restriction process as follows.
When the acceleration applied to the vehicle body during a left turn is equal to or greater than a predetermined value at which the vehicle becomes unstable, that is, when the vehicle speed V is equal to or greater than the second vehicle speed determination value V2 and the left steering angle θ is equal to or greater than the second steering angle determination value θ2 And when the vehicle speed V is greater than or equal to the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2 and the left steering angle θ is greater than or equal to the first steering angle determination value θ1, the hydraulic pressure PL of the left oil chamber R2 becomes a predetermined value. It is determined whether or not the oil pressure determination value P0 has been exceeded. CP
When the hydraulic pressure PL is equal to or less than the hydraulic pressure determination value P0, the U55 determines that there is a possibility that a left steering input that makes the vehicle unstable will be applied from the steering 21, and the left steering wheel 55 controls the left steering by the steering input. The steering restriction flag FSL is set to “1”. On the other hand, when the oil pressure exceeds the oil pressure determination value P0, the CPU 55 determines that the right steering input for reducing the unstable state of the vehicle is being applied from the steering 21 and allows the right steering by the steering input. Therefore, the left steering restriction flag FSL is set to “0”.

The solenoid drive circuit 54 supplies the exciting current Ie to the electromagnetic solenoid 41 of the left electromagnetic on-off valve 39 when the right steering restriction flag FSR is "1", and supplies the same when the right steering restriction flag FSR is "0". The supply of the excitation current Ie is stopped. The solenoid drive circuit 54 supplies the exciting current Ie to the electromagnetic solenoid 40 of the right solenoid on-off valve 38 when the left steering restriction flag FSL is “1”, and supplies the excitation current Ie when the left steering restriction flag FSL is “0”. The supply of Ie is stopped.

Next, the operation of the power steering apparatus configured as described above will be described with reference to the flowchart of the steering restriction processing shown in FIGS. In the steering restriction processing, the CPU 55 firstly performs a step (hereinafter, referred to as S).
At 100, the detected values of the steering angle θ and the oil pressures PR and PL are read, and the vehicle speed V is obtained. Next, the CPU 55
In S110, it is determined from the steering angle θ whether the steering direction is a right steering state, a left steering state, or a straight traveling state.

When the CPU 55 determines in S110 that the vehicle is in the right steering state, in S120 the vehicle speed V is less than the first vehicle speed determination value V1, or is equal to or more than the first vehicle speed determination value V1 and the second vehicle speed V is equal to or greater than the second vehicle speed determination value V1.
It is determined whether the vehicle speed is lower than the vehicle speed determination value V2, or is equal to or higher than the second vehicle speed determination value V2.

When the CPU 55 determines in S120 that the vehicle speed V is equal to or greater than the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2, the CPU 55 determines in S130 that the right steering angle θR is greater than or equal to the first steering angle determination value θ1. It is determined whether or not there is. CPU 55
When the right steering angle θR is smaller than the first steering angle determination value θ1 in S130, the right steering restriction flag FSR is set to “0” in S140, and the process ends.

On the other hand, if the right steering angle θR is equal to or larger than the first steering angle determination value θ1 in S130, the CPU 55 proceeds to S1.
At 50, it is determined whether or not the oil pressure PR of the right oil chamber R1 exceeds the oil pressure determination value P0. When the oil pressure PR is equal to or less than the oil pressure determination value P0 in S150, the CPU 55 proceeds to S16.
If 0, the right steering restriction flag FSR is set to “1”, and the process ends.

On the other hand, the CPU 55 determines in S150 that the hydraulic pressure PR
Is greater than the oil pressure determination value P0, S140 is executed, and the process ends. On the other hand, when the vehicle speed V is equal to or higher than the second vehicle speed determination value V2 in S120, the CPU 55 proceeds to S1.
At 70, it is determined whether the right steering angle θR is equal to or larger than the second steering angle determination value θ2. When the right steering angle θR is smaller than the second steering angle determination value θ2 in S170, the CPU 55 proceeds to S170.
140 is executed and the process is terminated.

On the other hand, if the right steering angle θR is equal to or larger than the second steering angle determination value θ2 in S170, the CPU 55 proceeds to S1.
Execute 50. Further, the CPU 55 determines in S120 that the vehicle speed V
Is less than the first vehicle speed determination value V1 in S140
To end the process.

When the right steering restriction flag FSR is "1", the solenoid drive circuit 54 controls the left solenoid on-off valve 39.
The electromagnetic current 41 is supplied to the electromagnetic solenoid 41, and when the right steering restriction flag FSR is "0", the exciting current Ie is supplied.
Stop supplying. Therefore, at the time of right steering, the right electromagnetic on-off valve 38 and the left electromagnetic on-off valve 39 are connected to each other as shown in FIG.
Control is performed as shown in FIG.

When the CPU 55 determines in S110 that the steering is in the left steering state, the CPU 55 determines in S180 that the vehicle speed V is equal to the first steering speed.
It is determined whether the vehicle speed is less than the vehicle speed determination value V1, is equal to or more than the first vehicle speed determination value V1, and is less than the second vehicle speed determination value V2, or is equal to or more than the second vehicle speed determination value V2. CPU 55
When the vehicle speed V is less than the first vehicle speed determination value V1 in S180, the process ends.

On the other hand, if the CPU 55 determines in S180 that the vehicle speed V is equal to or greater than the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2, the CPU 55 determines in S190 that the left steering angle θL is equal to the first steering speed θL.
It is determined whether the steering angle is equal to or larger than the steering angle determination value θ1. CPU
55 is that the left steering angle θL is equal to the first steering angle determination value θ in S190.
If it is less than 1, the left steering restriction flag FS is determined in S200.
L is set to “0” and the process ends.

On the other hand, if the left steering angle θL is equal to or larger than the first steering angle determination value θ1 in S190, the CPU 55 proceeds to S2.
At 10, it is determined whether or not the oil pressure PL of the left oil chamber R2 exceeds the oil pressure determination value P0. When the hydraulic pressure PL is equal to or less than the hydraulic pressure determination value P0 in S210, the CPU 55 proceeds to S22.
If 0, the left steering restriction flag FSL is set to “1”, and the process ends.

On the other hand, the CPU 55 determines in S210 that the hydraulic pressure PL
Is greater than the oil pressure determination value P0, S200 is executed and the process is terminated. On the other hand, when the vehicle speed V is equal to or more than the second vehicle speed determination value V2 in S180, the CPU 55 proceeds to S2.
At 30, it is determined whether the left steering angle θL is equal to or greater than the second steering angle determination value θ2. If the left steering angle θL is smaller than the second steering angle determination value θ2 in S230, the CPU 55 proceeds to S230.
200 is executed, and the process ends.

On the other hand, if the left steering angle θL is equal to or larger than the second steering angle determination value θ2 in S230, the CPU 55 proceeds to S2.
Execute Step 10. The CPU 55 controls the left steering restriction flag FS.
When L is "1", the excitation current Ie is supplied to the electromagnetic solenoid 40 of the right electromagnetic on-off valve 38, and when the left steering restriction flag FSL is "0", the supply of the excitation current Ie is stopped. Therefore, during left steering, the right solenoid on-off valve 38
The left solenoid valve 39 is controlled as shown in FIGS. 5 (a) and 5 (b).

As a result of the steering restriction processing, when the steering wheel 21 is steered to the right while the vehicle speed V is lower than the first vehicle speed determination value V1, a hydraulic power cylinder 19 for steering the steered wheels 14 is provided.
The hydraulic oil supplied from the hydraulic pump 17 at a predetermined range of hydraulic pressure and oil amount to the left oil chamber R2
The hydraulic oil is supplied from the control valve 20 in response to the right steering input from the engine and the same amount of hydraulic oil is discharged from the right oil chamber R1 to the oil tank 18 via the control valve 20. As a result, by operating the hydraulic power cylinder 19 based on the supplied and discharged hydraulic oil, the steered wheels 14 are steered to the right in accordance with the steering input.

When the vehicle speed V is equal to or greater than the first vehicle speed determination value V1 and less than the second vehicle speed determination value V2, the right steering angle θR is changed from less than the first steering angle determination value θ1 to the first steering angle determination value θ1 or more. When the steering wheel 21 is steered to the right so that the left solenoid on-off valve 39 is switched from the communicating state to the closed state,
Even if a right steering input is applied to the steering wheel 21 continuously, the hydraulic power cylinder 19 does not operate. As a result, the steered wheels 14 are not steered to the right any more, and the lateral acceleration applied to the vehicle at the time of turning does not increase enough to make the vehicle unstable.

When the steering wheel 21 is steered to the left in a state where the right steering of the steered wheels 14 is restricted while the vehicle speed V is equal to or higher than the first vehicle speed judgment value V1 and lower than the second vehicle speed judgment value V2, the control valve 20 is turned to the right. The left electromagnetic on-off valve 39 is switched from the shut-off state to the communicating state based on the hydraulic pressure PR supplied to the right oil chamber R1 via the electromagnetic on-off valve 38. Then, the hydraulic oil is supplied to the right oil chamber R1 of the hydraulic power cylinder 19, and the hydraulic oil is discharged from the left oil chamber R2 to the control valve 20 side via the left electromagnetic opening / closing valve 39, so that the hydraulic power cylinder 19 is steered. 14 is steered to the left. As a result, the steered wheels 14 are steered from the state in which right steering is restricted to the straight traveling state.

When the vehicle speed V is less than the first vehicle speed determination value V1, the left solenoid valve 39 remains open.
Even if the steering angle θ of the steered wheels 14 is equal to or larger than the first steering angle determination value θ1, right steering of the steering 21 is permitted. While the right steering angle θR is equal to or larger than the first steering angle determination value θ1, the vehicle speed V
From the first vehicle speed determination value V1 to the first vehicle speed determination value V1 or more, the supply of hydraulic oil to the left oil chamber R2 is regulated by the left solenoid on-off valve 39, and the right steering angle θR is determined by the first steering angle determination. The operation of the hydraulic power cylinder 20 is regulated while the value exceeds the value θ1. As a result, while the steering angle of the steered wheels 14 is equal to or greater than the first steering angle determination value θ1, further right steering is restricted.

From this state, the vehicle speed V is changed to the first vehicle speed determination value V
If the steering wheel 21 is steered to the left with the value of 1 or more,
The left electromagnetic on-off valve 39 is switched from the shut-off state to the communicating state based on the hydraulic pressure PR supplied from the control valve 20 to the right oil chamber R1 via the right-side electromagnetic on-off valve 38. Then, the hydraulic oil is supplied to the right oil chamber R1 of the hydraulic power cylinder 19, and the hydraulic oil is discharged from the left oil chamber R2 to the control valve 20 side via the left electromagnetic opening / closing valve 39, so that the hydraulic power cylinder 19 is steered. 14 is steered to the left. As a result, the steered wheels 14 are steered from the state in which right steering is restricted to the straight traveling state.

Similarly, when the vehicle speed V is equal to or greater than the second vehicle speed determination value V2, the steering wheel 21 is moved rightward so that the right steering angle θR becomes smaller than the second steering angle determination value θ2 and equal to or greater than the second steering angle determination value θ2. When the steering is performed, the operation of the hydraulic power cylinder 19 is restricted, and the steered wheels 14 are not further steered to the right. When the steering 21 is steered to the left from this state, the operation of the hydraulic power cylinder 19 is permitted, and the steered wheels 14 are steered from the state in which right steering is restricted to the straight traveling state.
Further, when the vehicle speed V is changed from a value less than the second vehicle speed determination value V2 to a value equal to or more than the second vehicle speed determination value V2 from the state where the right steering angle θR is equal to or more than the second steering angle determination value θ2, the operation of the hydraulic power cylinder 19 is restricted and the steering is performed. Wheel 14 is no longer steered to the right. When the steering 21 is steered to the left from this state, the operation of the hydraulic power cylinder 19 is permitted, and the steered wheels 14 are steered from the state in which right steering is restricted to the straight traveling state.

When the steering wheel 21 is steered to the left, the same operation as when steered to the right is performed. As described in detail above, according to the power steering device of the present embodiment, the following effects can be obtained.

(1) The hydraulic oil supplied to and discharged from the hydraulic power cylinder 19 in response to the steering input from the steering 21 so that the magnitude of the lateral acceleration applied to the vehicle at the time of turning does not become larger than a predetermined magnitude. The amount of oil was restricted. Therefore, it is possible to prevent steering in which the vehicle becomes unstable during turning.

(2) The lateral acceleration applied to the vehicle at the time of turning based on the steering input is determined based on the running state quantity (combination of the vehicle speed V and the steering angle θ), and the hydraulic power cylinder 1
The amount of hydraulic oil to be supplied / discharged to / from the pump 9 is limited. Therefore, based on the detected traveling state quantity, it is possible to prevent steering in which the vehicle becomes unstable during turning.

(3) The vehicle speed V and the steering angle θ, which determine the magnitude of the lateral acceleration applied to the vehicle at the time of turning, are taken as the traveling state quantities.
Is detected, and it is determined whether or not the vehicle becomes unstable during turning based on a combination of both. Therefore,
Lateral acceleration is directly detected by an acceleration sensor, and the vehicle body swings from side to side when traveling straight on an uneven road surface, compared to when the vehicle is judged to be unstable based on this lateral acceleration. The steering control means (microcomputer 50) does not operate due to the acceleration. As a result, the steering of the steered wheels 14 is not restricted at the time of steering from straight running, even though the vehicle does not become unstable.

(4) The solenoid on-off valve 3 provided on the pipes 29 and 30 between the control valve 20 and the cylinder 19
According to 8, 39, the hydraulic oil supplied to and discharged from the hydraulic power cylinder 19 from the valve 20 is allowed or cut off. Therefore, the supply and discharge of the hydraulic oil to and from the hydraulic power cylinder 19 can be stopped, and the steering that makes the vehicle unstable can be stopped.

(5) The steering direction is determined based on the oil pressure in each of the oil chambers R1, R2 of the hydraulic power cylinder 19. Therefore, it is possible to detect that a steering input has been made in a direction opposite to the steering direction that makes the vehicle unstable.

The embodiment is not limited to the above embodiment, but may be modified as follows. The lateral acceleration may be directly detected using a lateral acceleration sensor, and the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder 19 may be limited based on the result of the determination of the detected lateral acceleration. In this case as well, it is possible to prevent steering in which the vehicle becomes unstable due to lateral acceleration applied to the vehicle at the time of turning.

In the above embodiment, the lateral acceleration as a running state quantity is calculated from the detected vehicle speed V and steering angle θ,
The operation amount of the hydraulic power cylinder 19 may be limited based on a result of determining the lateral acceleration based on a predetermined determination value. In this case as well, it is possible to prevent steering in which the vehicle becomes unstable due to lateral acceleration applied to the vehicle at the time of turning. In addition, even if the vehicle sways while traveling straight on an uneven road surface, the steering of the steered wheels 14 is not restricted based on the lateral acceleration applied to the vehicle due to the sway.

In addition to the electromagnetic on-off valves 38 and 39 that can be switched between fully open and fully closed, electromagnetically operated flow control valves that can change the opening in two stages are provided in the pipe lines 29 and 30, respectively. Further, for each of the determination value sets V1, θ1, V2, and θ2, preliminary determination value sets V1a, θ1a, V2a, and θ2a corresponding to lower lateral acceleration values are set. Then, the microcomputer 50 controls the steering,
First, the opening degree of the electromagnetically operated flow control valve is controlled from full open to half open based on the preliminary determination value sets V1a, θ1a, V2a, θ2a, and then the electromagnetic opening / closing valve 38 based on the determination value sets V1, θ1, V2, θ2. , 39 from the communication state to the cutoff state.

In this configuration, when the operation of the hydraulic power cylinder 19 is restricted, the steering operation of the steering 21 is restricted once it becomes heavy, so that the driver is less likely to feel uncomfortable with the operation of the steering 21. it can.

A solenoid proportional control valve capable of continuously changing the opening degree is used in place of the solenoid on-off valves 38 and 39,
The microcomputer 50 operates the hydraulic power cylinder 19
May be controlled so that the opening degree when restricting the operation of is decreased as the vehicle speed V increases. In this case, the higher the vehicle speed V, the greater the steering force when the steering is restricted. Therefore, the steering when the steering is restricted when the vehicle speed V is relatively low and the vehicle is less likely to be unstable during turning. The operation of No. 21 is made less likely to cause discomfort,
When the steering is restricted when the vehicle speed V is relatively high and the vehicle is likely to be unstable during turning, steering can be reliably restricted.

The lifting position H of the load is detected by the limit switch, and the load W is detected by the pressure sensor from the hydraulic pressure of the lift cylinder. Then, based on the detected lift position H and the load W, a combination of the lift position H and the load W corresponding to the magnitude of the centrifugal force that causes the vehicle to tilt during turning according to the position of the vehicle center of gravity in the vertical direction. The magnitude of the centrifugal force is determined on the basis of a preliminary determination value (H = H0, W = W0) set in advance. When the magnitude of the centrifugal force is equal to or greater than the magnitude corresponding to the preliminary determination value,
The electromagnetic on-off valves 38 and 39 are controlled based on a first determination value (for example, a first vehicle speed determination value V1 and a first steering angle determination value θ1) set in advance with respect to the traveling state quantity, and the magnitude of the centrifugal force is increased. Is smaller than the size corresponding to the preliminary judgment value,
A second determination value (the first vehicle speed determination value V1 and the third steering angle determination value θ3, which is set in advance for the value of the traveling state amount corresponding to the centrifugal force having a magnitude smaller than the first determination value, where θ3
> Θ1), the electromagnetic on-off valves 38 and 39 may be controlled.

Therefore, even if the value of the traveling state quantity is the same, when the loading state of the load is low and the position of the center of gravity is low and the vehicle is unlikely to be unstable when turning, the operation of the hydraulic power cylinder 19 is not performed. The vehicle speed V and the steering angle θ are not restricted over a wider range so that they are not easily regulated. Also, when the loading state of the load is high, high, and high, the center of gravity is high, and the vehicle tends to be unstable during turning, the operation of the hydraulic power cylinder 19 is restricted at an early point in time, so that the vehicle can be reliably turned during turning. It can prevent instability.

An electromagnetic opening / closing valve is provided in only one of the pipes 29, 30 connecting each of the supply / discharge ports 24A, 24B of the control valve 20 and each of the oil chambers R1, R2.
The steering direction of the steering 21 may be detected by a torque sensor provided on the steering 21. According to this configuration as well, it is possible to prevent steering in which the vehicle becomes unstable during turning.

The control valve 20 is only required to be capable of supplying and discharging hydraulic oil supplied from the hydraulic pump 17 in accordance with a steering input. For example, any of a rotary valve, a spool valve, a flapper valve and the like can be used. There may be.

The vehicle on which the power steering device is mounted is not limited to a forklift, and may be an industrial vehicle such as a tractor shovel (shovel loader), a skid steer loader, a towing tractor, an aerial work vehicle, or the like.

Hereinafter, technical ideas other than the claims which can be grasped from the embodiment will be described together with their effects. (1) In the power steering device according to claim 2, the traveling state quantity is a lateral acceleration, the traveling state detecting unit is an acceleration sensor, and the steering control unit determines that the lateral acceleration is a predetermined value. When the value is equal to or more than the value, the flow rate limiting means is controlled so as to limit the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder. According to such a configuration, steering can be assisted in a wider range of vehicle speed and steering angle within a range in which the vehicle does not become unstable due to lateral acceleration applied to the vehicle at the time of turning based on the steering input.

(2) In the power steering apparatus according to claim 2 or 3, the hydraulic oil supply / discharge control means is a control valve, and the flow rate restriction means is such that the control valve is a hydraulic power cylinder. An electromagnetically-operated on-off valve provided on at least one of a pair of flow paths for supplying and discharging hydraulic oil to and from each oil chamber, the opening degree of which can be switched between fully open and fully closed; An electromagnetically operated flow control valve that is provided on at least one of the flow passages and whose opening degree can be switched between a full open state and a half open state, wherein the steering control means controls the electromagnetically operated open / close valve to a fully open state, Control the operation flow control valve to full open to allow the supply of hydraulic oil to the hydraulic power cylinder,
In addition, when the electromagnetic operation on-off valve is controlled to a fully closed state to shut off the supply of hydraulic oil, and when the state in which the supply and discharge of the hydraulic oil is allowed to be shut off, the electromagnetic operation on-off valve is fully opened. After controlling the electromagnetic operation flow control valve from full open to half open as it is, the electromagnetic open / close valve is controlled from full open to full close.

According to such a configuration, when the operation of the hydraulic power cylinder is restricted, the steering operation is not suddenly restricted, so that the driver is less likely to feel uncomfortable with the steering operation. .

(3) In the power steering apparatus according to any one of claims 1 to 6, the steering control means is constituted by a microcomputer. According to such a configuration, even when the same power steering device is mounted on vehicles of different models, it is possible to easily change the determination value of the running state amount that differs for each model.

(4) A forklift equipped with the power steering device according to any one of claims 1 to 6. According to such a configuration, it is possible to prevent the vehicle from turning when the vehicle becomes unstable.

[0087]

According to the first to sixth aspects of the present invention, it is possible to limit steering in which the vehicle becomes unstable during turning.

According to the third aspect of the present invention, it is possible to prevent erroneous control due to lateral vibration when the vehicle is traveling straight on an uneven road surface. According to the fourth aspect of the invention, it is possible to restrict the steering that makes the vehicle unstable.

According to the fifth aspect of the invention, it is possible to reliably detect that a steering input in a direction opposite to the steering direction that makes the vehicle unstable is applied. According to the invention described in claim 6, steering can be assisted in a wider range of vehicle speed and steering angle while restricting steering in which the vehicle becomes unstable during turning.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a power steering device.

FIG. 2 is a schematic side view of a forklift.

FIG. 3 is an electric block diagram of the power steering device.

FIG. 4A is a graph showing an open / closed state of a left electromagnetically operated on-off valve with respect to a vehicle speed and a steering angle during right steering;
(B) is a graph showing the open / closed state of the right electromagnetically operated on / off valve with respect to the vehicle speed and the steering angle.

FIG. 5A is a graph showing an open / closed state of a left electromagnetically operated on-off valve with respect to a vehicle speed and a steering angle during left steering;
(B) is a graph showing the open / closed state of the right electromagnetically operated on / off valve with respect to the vehicle speed and the steering angle.

FIG. 6 is a flowchart of a flow rate control process.

FIG. 7 is a flowchart of a flow rate control process.

[Explanation of symbols]

11 power source, 14 steering wheel, 17 hydraulic pump, 18
... oil tank, 19 ... hydraulic power cylinder, 20 ... control valve as hydraulic oil supply / discharge control means, 21 ... steering, 32, 33 ... oil pressure sensor as hydraulic pressure detection means constituting supply / discharge restriction means and steering direction detection means , 38
··· Right electromagnetically operated on / off valve constituting supply / discharge limiting means and flow rate limiting means; 39 ··· Left electromagnetically operated open / close valve; 43 ··· Magnetic sensor as vehicle speed detecting means constituting supply / discharge limiting means and traveling state amount detecting means; 44: a potentiometer as a steering angle detecting means constituting the supply / discharge limiting means and the traveling state quantity detecting means; 50; a microcomputer as a steering control means and a steering direction determining means constituting the supply / discharge limiting means and the steering direction detecting means; R1: right oil chamber, R2: left oil chamber, V: vehicle speed that constitutes a traveling state quantity, V1: first vehicle speed decision value as a vehicle speed decision value, V2: second vehicle velocity decision value, θ: traveling state quantity A steering angle to be configured, θ1... A first steering angle determination value as a steering angle determination value, θ2... Similarly a second steering angle determination value.

Claims (6)

[Claims] 1. An all-hydraulic power steering device in which hydraulic oil supplied from a hydraulic pump is supplied to a hydraulic power cylinder in response to a steering input from a steering, and the steered wheels are steered left and right by the hydraulic power cylinder. The amount of hydraulic oil supplied to the hydraulic power cylinder in accordance with the steering input of the steering so that the magnitude of the lateral acceleration applied to the vehicle at the time of turning based on the steering input does not become larger than a predetermined magnitude. Power steering device provided with a supply / discharge restricting means for restricting the pressure. 2. A hydraulic pump, which is driven by a power source and supplies hydraulic oil with a predetermined range of hydraulic pressure and oil amount, and is operated by a steering input from a steering wheel, and the hydraulic oil supplied from the hydraulic pump is steered. Depending on the input,
Hydraulic oil supply / discharge control means capable of supplying the same amount of hydraulic oil supplied from outside to an external oil tank while supplying the hydraulic oil to the outside while distinguishing the steering direction; A double-acting hydraulic power cylinder, which has a pair of oil chambers for supplying and discharging hydraulic fluid and steers the steered wheels by supplying and discharging hydraulic oil to and from each oil chamber. Traveling state quantity detection means for detecting a traveling state quantity of the vehicle detected in accordance with the size; steering direction detection means for detecting a steering direction of the steering; Flow rate limiting means capable of limiting an amount of supplied hydraulic oil, and the oil is supplied by a right or left steering input of the steering based on a predetermined determination value for the traveling state quantity. Controlling the flow rate limiting means so that the amount of hydraulic oil supplied to and discharged from the power cylinder is limited so that the lateral acceleration does not exceed a predetermined magnitude corresponding to the determination value; Based on the detection result of the steering direction detecting means, it is determined whether or not the steering input to the steering is in the opposite direction, and when the steering input is in the opposite direction, the hydraulic power cylinder is And a steering control means for controlling the flow rate limiting means so as not to limit the amount of hydraulic oil supplied and discharged. 3. The travel state quantity is a combination of a vehicle speed and a steering angle, wherein the travel state quantity detection means includes a vehicle speed detection means and a steering angle detection means, and the steering control means includes a vehicle speed and a steering angle detection means. When the steering angle is equal to or greater than a predetermined vehicle speed determination value and the steering angle is equal to or greater than the predetermined steering angle determination value, the flow rate limiting means is configured to limit the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder. The power steering apparatus according to claim 2, which controls the power steering. 4. The hydraulic oil supply / discharge control means is a control valve, and the flow rate restricting means is a pair of a control valve for supplying and discharging hydraulic oil to and from each oil chamber of the hydraulic power cylinder. An electromagnetically operated on / off valve provided on at least one of the flow paths, wherein the steering control means controls the electromagnetically operated on / off valve to a fully open state or a fully closed state to supply hydraulic oil to a hydraulic power cylinder. The power steering apparatus according to claim 2 or 3, wherein the power steering apparatus allows or shuts off. 5. The electromagnetically operated on-off valve is provided in each of a pair of flow paths through which the control valve supplies and discharges hydraulic oil to and from each of the oil chambers of the hydraulic cylinder. The hydraulic power cylinder includes: a hydraulic pressure detecting unit configured to detect a hydraulic pressure in each oil chamber; and a steering direction determining unit configured to determine a direction of a steering input to a steering wheel based on the hydraulic pressure. When the determining means determines that the steering direction of the steering is in the opposite direction, the flow rate limiting means is controlled so that the restriction on the amount of hydraulic oil supplied to and discharged from the hydraulic power cylinder is released. The power steering device according to any one of claims 2 to 4, which controls the power steering device. 6. A forklift, comprising: a lift detecting means for detecting a lift position of a fork in a forklift; and a load detecting means for detecting a load of a load loaded on the fork. The centrifugal force is determined based on each preliminary determination value set in advance for a combination of the elevation position and the load corresponding to the magnitude of the centrifugal force that attempts to tilt the vehicle body during a turn according to the position in the direction. When the magnitude is equal to or greater than the magnitude corresponding to each of the preliminary determination values, the flow rate limiting means is controlled based on a first determination value set in advance for the value of the traveling state quantity, and When the value is less than the magnitude corresponding to the preliminary determination value, the value of the traveling state quantity corresponding to the centrifugal force having a magnitude smaller than the first determination value is determined based on a second determination value set in advance. Power according to any one of claims 2 to 5 for controlling the flow restriction Te steering system.