JP2000142443A - Hydraulic power steering device and industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the temporary excessiveness of a steering force at the steering time in the same direction anew after stopping the steering of a handle. SOLUTION: An electro-magnetic open/close selector valve 21 is provided on a connection pipe road 41 for connecting a pair of supply/discharge pipe roads 27a, 27b in which the operation oil is supplied/discharge to/from the power cylinder 16 from an operation oil supply/discharge control valve 20. The electro-magnetic open/close selector valve 21 is made in an open state for a prescribed time from a close state by the micro-computer of a control unit 43 at the stopping time of the steering of a handle 17. The electro-magnetic open/close selector valve 21 is kept in the close state by the micro-computer when a tyre angle θT is a standard tyre angle or more when the handle 17 is steered in the maximum turn angle side and stopped. Further, the time when the electro-magnetic open/close selector valve 21 is opened is restricted by the micro-computer when the car speed (v) is the standard car speed or more.

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 apparatus and an industrial vehicle.

[0002]

2. Description of the Related Art Conventionally, all-hydraulic power steering devices have been employed in industrial vehicles such as forklifts. In addition, all-hydraulic power steering devices are employed not only in engine vehicles but also in battery vehicles. In a battery car, unlike an engine car, a hydraulic pump of a power steering device is driven by an electric motor provided separately from an electric motor for traveling or cargo handling. When the steering wheel is not being steered, the electric motor is stopped so that battery power is not wasted.

[0003] Conventionally, that the steering wheel is steered,
Detected by rotary encoder. The rotary encoder outputs a pulse signal of a pulse number corresponding to the steering amount of the steering wheel. The number of revolutions of the electric motor is controlled in accordance with the number of pulses of the pulse signal, and hydraulic oil at a predetermined supply pressure is supplied to a hydraulic oil supply / discharge control valve (power steering control valve) at a flow rate corresponding to a steering amount. .
The hydraulic oil supply / discharge control valve is operated by steering of a steering wheel, and supplies / discharges hydraulic oil supplied from a hydraulic pump to a power cylinder by a supply amount corresponding to a steering amount according to a steering direction. As a result, the power cylinder operates, and the steered wheels are steered in the steering direction of the steering wheel by the steering angle corresponding to the steering amount. Therefore, since the electric motor is operated only when the steering wheel is being steered, battery power is not wasted.

Since the operation of the hydraulic pump is stopped when the steering wheel is not being steered, it is necessary to operate the hydraulic pump promptly when the steering wheel is steered from the stopped state. This is because, if the operation of the hydraulic pump is delayed, the supply amount of hydraulic oil is insufficient at the start of steering, and the steering force temporarily increases.

[0005] The hydraulic oil supply / discharge control valve is operated by steering a steering wheel, and is a supply / discharge switching valve for switching the supply / discharge direction of hydraulic oil to / from a power cylinder. A supply pump for supplying a supply amount corresponding to the amount. Then, when the steering wheel is steered from the neutral state where no steering force is applied, first, the spool of the supply / discharge switching valve held at the neutral position is switched from the neutral position to the right steering position or the left steering position. That is, when the steering wheel is steered right or left, for example, 10 degrees from the neutral state, the spool is switched from the neutral position to the right or left steering position. When the steering wheel is further steered from a state in which the supply / discharge switching valve is switched from the neutral position to the right or left steering position, the supply pump is steered while the supply / discharge switching valve is switched to the right or left steering position. Operated by Then, the supply pump supplies a supply amount of hydraulic oil corresponding to the steering amount of the steering wheel to the power cylinder.

Accordingly, the supply pump is not driven until the steering wheel is steered from the neutral state and the supply / discharge switching valve is switched from the neutral position to the right or left steering position, and the steering wheel is operated with a light steering force corresponding to the play of the steering wheel. Steered.
Since the electric motor is operated while the steering wheel is idled, when the supply pump is operated by the steering of the steering wheel and hydraulic oil is supplied to the power cylinder, sufficient hydraulic oil is supplied from the hydraulic pump. Is supplied at a reasonable flow rate. Therefore, even when the steering wheel is steered from the neutral state, the steering force does not temporarily become excessive.

[0007]

When the steering wheel is steered to the right, for example, the hydraulic pressure in the oil passage from the left oil chamber of the power cylinder to the supply pump to which the hydraulic oil is supplied by the right steering is changed by the hydraulic pump. The hydraulic pressure is high due to the hydraulic pressure based on the steering force of the steering wheel added to the supply pressure from the steering wheel. Here, when the right steering of the steering wheel is stopped and the hand is released from the steering wheel so that the steering force is not applied, the supply / discharge switching valve returns from the right steering position to the neutral position by the action of the return spring, and the electric motor is turned off. The operation stops and the supply of hydraulic oil from the hydraulic pump stops. At this time, since the reaction force for returning the power cylinder to the neutral side remains in the tire of the steered wheel that is steered to the right, the reaction force causes the oil passage from the left oil chamber of the power cylinder to the supply / discharge switching valve. And the high oil pressure is sealed.

In this state, if the steering wheel is steered to the right again, the time required for the spool of the supply / discharge switching valve to move from the neutral position to the right steering position again is short, so that the hydraulic pump is operated when the supply pump is operated. Flow rate of hydraulic oil supplied from the engine is insufficient for the steering amount. As a result, the high oil pressure sealed in the power cylinder side acts as a resisting force on the supply pump operated by steering the steering wheel, and the steering force for right steering the steering wheel becomes temporarily excessive. After a while, the operating oil is supplied from the hydraulic pump at a flow rate corresponding to the steering amount, and the steering force becomes normal.

When the steering of the steering wheel to the right is stopped, if the steering wheel is held without releasing the hand from the steering wheel, the supply / discharge switching valve remains switched to the right steering position, and the electric motor stops and the hydraulic pressure is reduced. Supply of hydraulic oil from the pump stops. At this time, similarly to the case where the right-hand steered steering wheel is not held, the high oil pressure based on the reaction force of the tire of the steered right-hand steered wheel is applied between the left oil chamber of the power cylinder and the supply / discharge switching valve. Sealed in the oil passage.

When the steering wheel is to be further steered to the right from this state, the handle has no play in the right steering direction since the spool of the supply / discharge switching valve is already disposed at the right steering position. For this reason, the steering wheel is steered in a state where the electric motor is not operated and the hydraulic oil is not supplied from the hydraulic pump, and the steering force is temporarily further increased.

[0011] The above-mentioned phenomenon also occurs during left steering. Accordingly, there is a problem in that once the steering of the steering wheel is once stopped, when the steering wheel is again steered in the same steering direction, the steering force temporarily becomes excessively large and the steering of the steering wheel cannot be smoothly performed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a hydraulic power steering apparatus which stops an electric motor for driving a hydraulic pump when a steering wheel is not being steered. It is an object of the present invention to provide a hydraulic power steering device and an industrial vehicle that can prevent the steering force from being temporarily excessively increased when the steering wheel is once stopped and then steered in the same steering direction.

[0013]

SUMMARY OF THE INVENTION In order to solve the above problems, the invention according to claim 1 operates an electric motor that drives a hydraulic pump when a steering wheel is steered,
In a hydraulic power steering apparatus, a hydraulic oil supply / discharge control valve operated by steering the steering wheel supplies hydraulic oil supplied from the hydraulic pump to a power cylinder in accordance with a steering direction and a steering amount of the steering wheel. A hydraulic pressure release means is provided for releasing hydraulic pressure sealed in a supply / discharge oil passage connecting the supply control valve and the power cylinder when the steering of the handle is stopped.

According to a second aspect of the present invention, in the first aspect of the present invention, the hydraulic pressure release means includes an electromagnetic control valve provided so as to hold or release the hydraulic pressure of the supply / discharge oil passage. Steering stop detecting means for detecting that the steering of the steering wheel has stopped, and controlling the electromagnetic control valve so as to hold the oil pressure of the oil supply / drain passage when it is not detected that the steering of the steering wheel has stopped, And valve control means for controlling the electromagnetic control valve so as to release the oil pressure of the supply / drain oil passage when it is detected that the steering of the steering wheel has stopped.

According to a third aspect of the present invention, in the second aspect of the present invention, each time the steering wheel is steered, a steering direction detecting means for detecting a steering direction and newly storing the steering direction; Steering angle detection means for detecting the steering angle of
When it is detected that the steering of the steering wheel has stopped,
When the detected tire angle is equal to or greater than a predetermined reference steering angle, and when the stored steering direction is the straight-ahead state direction, the control to release the oil pressure of the oil supply / drain passage is allowed; When the stored steering direction is the maximum turning angle direction, a steering response control unit that controls the valve control unit so as to prohibit the control by the valve control unit to release the oil pressure of the supply / drain oil passage; and It has.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, when the detected vehicle speed is equal to or higher than a predetermined reference vehicle speed, the vehicle speed is detected. And a vehicle speed response control means for controlling the valve control means so as to limit the degree to which the oil pressure in the supply / discharge oil passage is released when the vehicle speed is lower than the reference vehicle speed.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the electromagnetic control valve is provided on a communication oil passage connecting the two oil supply and discharge oil passages. When the deviation angle between the target steering wheel angle of the steering wheel preset with respect to the tire angle and the detected steering wheel angle is equal to or greater than a predetermined allowable value, the deviation angle is less than the allowable value. And a shift angle correcting means for controlling the electromagnetic control valve when the steering wheel is steered.

The invention according to claim 6 is the invention according to any one of claims 2 to 5, wherein the electromagnetic control valve is an electromagnetic open / close switching valve, and the valve control means includes:
When it is detected that the steering of the steering wheel has been stopped, the electromagnetic open / close switching valve is controlled to be in an open state for a predetermined opening time.

According to a seventh aspect of the present invention, there is provided the hydraulic power steering apparatus according to any one of the first to sixth aspects. (Operation) According to the first aspect of the present invention, when the steering wheel is steered, the electric motor is operated, and hydraulic oil is supplied from the hydraulic pump to the hydraulic oil supply / discharge control valve. Then, hydraulic oil is supplied from the hydraulic oil supply / discharge control valve to the power cylinder in accordance with the steering direction and the steering amount of the steering wheel. As a result, the steered wheels are steered by the power cylinder according to the steering direction and the steering amount of the steering wheel. When the steering of the steering wheel stops, the steering oil from the tires of the steered wheels that have been steered up to the oil supply / drain passage from one oil chamber of the power cylinder to which the hydraulic oil was supplied at the time of the steering to the hydraulic oil supply / discharge control valve is supplied. A high oil pressure based on the reaction force is sealed and brought into a state. Then, after the steering of the steering wheel is stopped, the trapped high oil pressure is released by the depressurizing means. Therefore, when the steering wheel once stopped is steered again in the same steering direction, a high oil pressure acting as a resistance force in a direction opposite to the steering direction is not sealed, and the steering force of the steering wheel is temporarily excessively large. Never be.

According to the invention described in claim 2, according to claim 1,
In addition to the operation of the invention described in the above, when it is detected that the steering of the steering wheel has stopped, the electromagnetic control valve is controlled and the oil pressure in the oil supply / drain passage is released. As a result, when the steering wheel is again steered in the same steering direction from the state where the steering is stopped, the steering pressure of the steering wheel is temporarily excessively large because there is no high hydraulic pressure remaining as the steering resistance force in the oil supply / drain passage. Never be.

According to the invention described in claim 3, according to claim 2,
In addition to the effect of the invention described in the above, when the steering wheel is steered to the maximum turning angle side and stopped, and the steering angle of the steered wheels is equal to or larger than the reference steering angle, the hydraulic pressure of the oil supply / discharge oil passage is released. Absent. If the steering wheel is at the maximum turning angle and the steering of the steering wheel is regulated, if the steering force is continuously applied to the steering wheel, the operation of the power cylinder will be restricted because the oil pressure in the oil supply / drain passage will be released by the hydraulic pressure release means. The steering wheel is steered while it is left. As a result, the rotational positional relationship between the steering wheel and the steered wheels is shifted. However, when the steering wheel is steered in the direction of the maximum turning angle and the steering angle stops at the reference steering angle or more, the hydraulic pressure of the supply / discharge oil passage is not released, so that the rotational positional relationship between the steering wheel and the steered wheels does not shift.

According to the invention described in claim 4, claim 2 is provided.
Alternatively, in addition to the effect of the invention described in claim 3, when the vehicle speed is equal to or higher than the reference vehicle speed, the degree to which the high oil pressure sealed in the oil supply / discharge passage is released is limited. If the oil pressure in the oil supply / drain passage is released when the vehicle speed is equal to or higher than the reference vehicle speed, the steered wheels may be steered regardless of the steering of the steering wheel. However, when the vehicle speed is higher than or equal to the reference vehicle speed,
Since the degree to which the oil pressure in the oil supply / discharge passage is released is limited, the steered wheels are not steered regardless of the steering of the steering wheel.

According to the invention described in claim 5, according to claim 2,
In addition to the effect of the invention according to any one of claims 4 to 4, a temporary control of steering force at the time of steering wheel steering is performed by using an electromagnetic control valve for correcting a deviation between a steering wheel angle and a tire angle. The increase is suppressed.

According to the invention of claim 6, according to claim 2,
In addition to the effect of the invention described in any one of claims to 5, the high hydraulic pressure in the supply / discharge oil passage is released by setting the electromagnetic open / close switching valve to the open state for a predetermined time.

According to the seventh aspect of the present invention, a hydraulic power steering device provided in an industrial vehicle performs the operation according to any one of the first to sixth aspects.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, the forklift 10 is a battery vehicle, and is a four-wheeled vehicle driven by front wheels and steered by rear wheels. A traveling motor 13 for driving a front wheel 12 and a differential 1
4 and a hydraulic power cylinder (hereinafter simply referred to as a power cylinder) 16 for steering the rear wheels 15R and 15L. A cab 11a provided on the vehicle body 11 includes a steering wheel 1
7 is provided, and the rear wheel 1 is
5R and 15L are steered. The body 1 has a handle 1
An all-hydraulic power steering device that drives the power cylinder 16 based on the steering of the vehicle 7 is provided.

As shown in FIG. 1, the hydraulic power steering apparatus has an electric motor 18, a hydraulic pump 19, a hydraulic oil supply / discharge control valve (oil control valve) 20, a power cylinder 16, and an electromagnetic opening / closing switch as an electromagnetic control valve. Valve 2
1, a hydraulic circuit comprising an oil tank 22 and the like.

The electric motor 18 is a DC motor and can control the number of revolutions. The hydraulic pump 19 is an electric motor 18
The hydraulic oil in the oil tank 22 can be supplied to the hydraulic oil supply / discharge control valve 20 at a flow rate corresponding to the rotation speed of the electric motor 18. A feed line 24 to which hydraulic oil is supplied is connected to the hydraulic pump 19, and the feed line 24 is connected to a check valve 25.
Is connected to the hydraulic oil supply / discharge control valve 20 via the control valve.

The hydraulic oil supply / discharge control valve 20 has a supply port P to which a feed pipe 24 is connected, and a discharge port R to which a return pipe 26 for returning hydraulic oil to the oil tank 22 is connected. I have. The hydraulic oil supply / discharge control valve 20 includes supply / discharge ports A, B to which a pair of supply / discharge pipe lines 27 a, 27 b as supply / discharge oil paths for supplying / discharging the hydraulic oil to / from the power cylinder 16 are connected. It has. The hydraulic oil supply / discharge control valve 20 is mechanically operated by the steering of the handle 17, and supplies the hydraulic oil supplied from the hydraulic pump 19 to the power cylinder 16 by a supply amount corresponding to the steering amount of the handle 17. A supply / discharge switching valve 35 and a supply pump 36 are provided. The hydraulic oil supply / discharge control valve 20 includes a relief valve 28 that discharges the hydraulic pressure of the feed line 24 to the return line 26, and a return line 26.
Check valve 2 that allows hydraulic oil to move from feed line to feed line 24
9 is provided.

The power cylinder 16 is a double-acting double-rod type. A pair of oil chambers R1 and R2 are formed by a piston 31 in a cylinder body 30, and a supply / discharge pipe line 27a is provided in the left oil chamber R1. The supply / discharge conduit 27b is connected to the oil chamber R2. Cylinder rods 32 provided on both sides of the piston 31 extend to the outside, and each end thereof is connected via a tie rod 33 to a knuckle arm 34 rotatably supported by a rear axle beam (not shown). Each knuckle arm 34 supports a right rear wheel 15R and a left rear wheel 15L, respectively.

The hydraulic oil supply / discharge control valve 20 has a supply / discharge switching valve 35 for switching the direction of hydraulic oil supplied / discharged to / from the power cylinder 16. The supply / discharge switching valve 35 is
7, a spool 35a directly operated. When no steering force is applied to the handle 17, the spool 35 a is brought to the neutral position PN by the return spring 35 b. Further, the spool 35a is moved to the neutral position PN when a steering force of a predetermined value or more in the right steering direction is applied to the steering wheel 17.
When a steering force equal to or more than a predetermined value in the left steering direction is applied to the right steering position PR from, the neutral steering position PN is switched to the left steering position PL.

The hydraulic oil supply / discharge control valve 20 is a constant displacement type supply pump 3 operated by steering the handle 17.
6 is provided. In the neutral position PN, the supply / discharge switching valve 35 is connected to each of the oil chambers R1, R2 of the power cylinder 16,
The oil passage between the hydraulic pump 19 and the oil tank 22 is shut off, and the supply pump 36 is shut off from the oil passages communicating with the oil chambers R1, R2 and the hydraulic pump 19. In the right steering position PR, the supply / discharge switching valve 35 connects the hydraulic pump 19 to the left oil chamber R1 via the supply pump 36, and the right oil chamber R
2 to the return line 26. The supply / discharge switching valve 35
In the left steering position PL, the hydraulic pump 19 communicates with the right oil chamber R2 via the supply pump 36, and the left oil chamber R1 communicates with the return line 26. The supply pump 36 is
Is supplied to the power cylinder 16 by an amount corresponding to the steering amount.

When the steering wheel 17 is steered to the right or left from a neutral state in which no steering force in the left or right steering direction is applied, the hydraulic oil supply / discharge control valve 20 first supplies the oil while the supply pump 36 is not operated. The discharge switching valve 35 is switched from the neutral position PN to the right or left steering position PR, PL. When the steering wheel 17 is further steered right or left from this state, the supply pump 36
7 is operated according to the steering amount.

At the right end of the rear axle beam supporting the knuckle arm 34, a tire angle sensor 37 as a steering angle detecting means for detecting the rotational displacement of the kingpin is fixed.

Below the steering wheel 17, a steering wheel angle sensor 3 for detecting the rotational displacement of the steering shaft 17a is provided.
8 are provided. The differential device 14 (shown in FIG. 2) is provided with a vehicle speed sensor 40 for detecting the rotation speed of the ring gear 39.

A connecting line 41 is provided between the supply and discharge lines 27a and 27b as a connecting oil path for connecting the supply and discharge lines 27a and 27b.
1 is provided. The electromagnetic on / off switching valve 21 is a single-acting solenoid type, and has two supply / discharge conduits 27a, 27 when demagnetized.
b to shut off the oil passage between the two supply and discharge pipes 27a, 2 during excitation.
7b is communicated via the aperture 42.

Tire angle sensor 37, steering wheel angle sensor 3
8 and the vehicle speed sensor 40 are each electrically connected to the input side of the control unit 43. The output side of the control unit 43 is electrically connected to the electric motor 18 and the electromagnetic switching valve 21.

Next, the electrical configuration of the hydraulic power steering apparatus configured as described above will be described with reference to the electrical block diagram of FIG. The tire angle sensor 37 outputs a detected value of the amount of rotation of the kingpin to the control unit 43 as a tire angle signal Sθ corresponding to the tire angle θT of the right rear wheel 15R. The handle angle sensor 38 outputs two pulse signals PA and PB in which the number of pulses is proportional to the amount of steering of the handle 17 and the phase shift is reversed depending on the steering direction, and when the handle 17 is at the reference position. The reference position signal PC is output to the control unit 43 as a signal for detecting the handle angle θH of the handle 17. Note that the reference position is a normal rotation position of the steering wheel 17 when the tire angle θT is “0” (straight running state).
When the lock-to-lock is, for example, two and a half rotations, the handle 17 takes three reference positions with different tire angles θT. The vehicle speed sensor 40 outputs a pulse signal having a pulse number corresponding to the rotation speed of the ring gear 39 to the control unit 43 as a vehicle speed signal Pv corresponding to the vehicle speed v.

The control unit 43 includes an A / D converter 44,
A microcomputer (hereinafter, microcomputer) 45 as a steering response control means and a vehicle speed response control means, a motor drive circuit 46, an electromagnetic valve drive circuit 47, and the like are provided. In the present embodiment, the hydraulic oil supply / discharge control means is constituted by the handle angle sensor 38, the microcomputer 45, and the motor drive circuit 46. Also, the steering wheel angle sensor 38 and the microcomputer 45
Constitute a steering direction detecting means and a steering stop means. The vehicle speed sensor 40 and the microcomputer 45 constitute a vehicle speed detecting means. Further, the microcomputer 45 and the solenoid valve drive circuit 47 constitute a valve control unit and a deviation angle correction unit. Further, the electromagnetic opening / closing switching valve 21, the handle angle sensor 38, the microcomputer 45, and the electromagnetic valve driving circuit 4
Reference numeral 7 denotes a hydraulic pressure release unit.

The microcomputer 45 converts the tire angle signal Sθ output from the tire angle sensor 37 into an A / D signal by the A / D converter 44.
The converted tire angle data Dθ is input. Microcomputer 4
Reference numeral 5 inputs two pulse signals PA and PB output from the steering wheel angle sensor 38 and one reference position signal PC. The microcomputer 45 controls the vehicle speed signal Pv output from the vehicle speed sensor 40.
Enter

On the other hand, the microcomputer 45 includes the motor drive circuit 4
6 to rotate the electric motor 18 at the commanded rotation speed. The microcomputer 45 includes a solenoid valve driving circuit 47
To excite the electromagnetic switching valve 21 to switch from the closed state to the open state and hold it.

The microcomputer 45 repeatedly executes a predetermined control program. The control program includes each routine of hydraulic oil supply control processing, handle angle correction processing, and hydraulic pressure release processing. In addition, the control program includes a routine of a steering wheel angle detection process executed by interruption.

The microcomputer 45 controls the rotation speed of the electric motor 18 in accordance with the steering speed of the steering wheel 17 based on the input pulse signals PA and PB as the hydraulic oil supply control process.

The microcomputer 45 performs a steering wheel angle detection process,
Each time a new pulse signal PA or PB is input, the process is executed by interruption. The microcomputer 45 detects the steering direction of the steering wheel 17 and the steering wheel angle θH based on the input pulse signals PA and PB and the reference position signal PC as the steering wheel angle detection process. Then, the microcomputer 45 includes the handle 1
7 is in a stopped state, and the steering direction of the steering wheel 17 and the steering wheel angle θ at that time are detected.
H is newly stored each time.

The microcomputer 45 performs a steering angle correction process based on the input steering wheel angle θH and tire angle θT so that the positional relationship between the right rear wheel 15R and the steering wheel 17 does not significantly deviate from the normal positional relationship. Switching valve 42
Control.

More specifically, the microcomputer 45 includes the right rear wheel 1
Normal target steering wheel angle θH with respect to 5R tire angle θT
A map in which d is set is stored. Microcomputer 45
Is the input tire angle θT as the steering wheel angle correction process.
Is determined, and it is determined whether or not a deviation angle Δθ between the handle angle θH detected in the handle angle detection processing and the calculated target handle angle θHd is equal to or smaller than a preset allowable value θR. When the deviation angle Δθ exceeds the allowable value θR, the microcomputer 45 corrects the deviation of the deviation angle Δθ by 180 ° or less when the steering wheel 17 is being steered, as the steering wheel angle correction process. It is determined whether it is the direction. When the steering direction is in a direction in which the deviation angle Δθ cannot be eliminated, the microcomputer 45 keeps the electromagnetic open / close switching valve 42 in the closed state, and conversely, the steering direction can eliminate the deviation angle Δθ. If it is possible, the electromagnetic open / close switching valve 21 is excited to switch from the closed state to the open state and hold it.

The microcomputer 45 controls the electromagnetic open / close switching valve 42 when detecting that the steering of the steering wheel 17 has stopped based on the pulse signals PA and PB, the vehicle speed v and the tire angle θT as the hydraulic pressure release processing.

More specifically, the microcomputer 45 detects that the steering of the steering wheel 17 once stopped is stopped based on the input states of the pulse signals PA and PB as the hydraulic pressure release processing. When the steering operation of the steering wheel 17 is stopped, the microcomputer 45 starts the operation after a predetermined waiting time (for example, 0.3 seconds) has elapsed since the steering operation was stopped.
The electromagnetic open / close switching valve 21 is opened for a predetermined valve opening time.

This is based on the following reason. For example, if the steering wheel 17 is once steered to the right and then released from the steering wheel 17 so that no steering force is applied, the spool 35
a returns from the right steering position PR to the neutral position PN. At this time, the steering wheel 17 is steered to the right by the supply pressure supplied from the hydraulic pump 19 to the supply / discharge oil passage 27a between the left oil chamber R1 of the power cylinder 16 and the hydraulic oil supply / discharge control valve 20. A high oil pressure to which the oil pressure based on the steering force at the time of being applied is added is enclosed. This means that, even when the steering wheel 17 is no longer steered to the right, a reaction force for regulating the operation in the right steering direction is applied to the power cylinder 16 from the tires of the rear wheels 15R and 15L. Because there is.

When the steering wheel 17 is steered to the right more rapidly from this state, the spool 35a once returned to the neutral position PN
Moves to the right steering position PR, and the left oil chamber R <b> 1 is connected to the supply side of the hydraulic pump 19 via the supply pump 36.
Then, since the operation of the electric motor 18 has been started and a little has not elapsed, and the hydraulic oil is not supplied from the hydraulic pump 19 at a flow rate corresponding to the steering amount of the handle 17, the supply / discharge oil including the left oil chamber R1 The high oil pressure sealed in the path 27b acts on the handle 17 as a resistance in the direction opposite to the steering direction. Therefore, when the right-handed steering wheel 17 is temporarily stopped and then steered rightward, the steering force of the steering wheel 17 becomes temporarily excessive. Therefore, the microcomputer 45
The electromagnetic open / close switching valve 21 is temporarily opened in a state where the right steering of the handle 17 is temporarily stopped, and a high oil trapped in the oil supply / discharge passage 27a from the left oil chamber R1 to the hydraulic oil supply / discharge control valve 20 is provided. The hydraulic pressure is changed to a supply / discharge oil passage 27b from the right oil chamber R2 where the high hydraulic pressure is not confined to the hydraulic oil supply / discharge control valve 20.
To release the high oil pressure on the oil passage 27a side.
The same applies to the case where the steering wheel 17 is steered to the left.
Pulled out to the side.

After the steering wheel 17 is once steered to the right,
When the handle 17 is held in that position, as shown in FIG. 4, the spool 35a of the supply / discharge switching valve 35 is fixed in the right steering position PR by the hydraulic pressure sealed by the reaction force from the tire. When the steering wheel 17 is further steered to the right from this state, the steering wheel 17 is not steered to the right by the movement of the spool 35a, that is, the steering wheel 17
Since the supply pump 36 is operated in a state where there is no play in the steering of the vehicle, the high oil pressure enclosed without operating the hydraulic pump 19 acts as a resistance force in the direction opposite to the right steering direction. For this reason, unlike the case where the steering wheel 17 once steered to the right is not held as it is, the resistance force is immediately applied to the steering wheel 17 to the right, so that the steering force in the right steering direction is further increased. Then, the microcomputer 45 temporarily opens the electromagnetic open / close switching valve 21 in a state where the right steering of the steering wheel 17 is temporarily stopped, so that the supply / discharge oil passage from the left oil chamber R1 to the hydraulic oil supply / discharge control valve 20 is provided. The high oil pressure sealed in 27a is supplied from the right oil chamber R2 to the hydraulic oil supply / discharge control valve 2
By discharging the oil to the oil supply / discharge passage 27b up to zero, the high oil pressure on the oil supply / discharge passage 27a side is released. The same applies to the case where the steering wheel 17 is steered to the left.

In the hydraulic pressure release process, the microcomputer 45 performs the steering operation when the detected tire angle θT is larger than a predetermined reference tire angle θTR when the steering of the steering wheel 17 is stopped. Only when the steering direction of the steering wheel 17 is in the direction toward the straight traveling state before the stop, the electromagnetic open / close switching valve 21 is opened for the valve opening time. On the other hand, the microcomputer 45 calculates the tire angle θ
When T is less than the reference tire angle θTR, the electromagnetic open / close switching valve 21 is opened for the valve opening time regardless of the steering direction of the steering wheel 17 before the steering stops.

This is because the hydraulic pressure release process is not performed when the tire angle θT is at the maximum turning angle, and the steering wheel 17 and the rear wheels 15R, 15R are
This is to prevent the relationship with L from shifting.

That is, when the steering wheel 17 is steered toward the maximum turning angle, when the rear wheels 15R and 15L reach the maximum turning angle, the steering of the steering wheel 17 is restricted and stopped. At this time, if the hydraulic pressure release processing is executed based on the stop of the steering of the steering wheel 17, both oil chambers R 1 and R 2 are communicated by the communication pipe 41, so that the power cylinder 1
The steering of the steering wheel 17 can be performed in a state where the operation of the steering wheel 6 is restricted. As a result, the handle 17 and both rear wheels 15R, 15R
The relationship with L is shifted.

Therefore, when the steering wheel 17 is steered to the maximum turning angle and stopped, the tire angle θT is equal to the reference tire angle θ.
If it is not less than TR, the hydraulic pressure release process is not executed. When the maximum turning angle at which the steering of both rear wheels 15R and 15L is restricted is detected, the hydraulic pressure release processing is not prohibited, and the tire angle θT when the steering wheel 17 is steered toward the maximum turning angle and stopped is determined. The reason for the case where the reference tire angle θTR or more is set is that the steering wheel 17 and the two rear wheels 15R and 15L are surely prevented from being displaced due to a control delay, and that the steering wheel 17 is steered to the maximum turning angle. This is because it does not matter if the power is increased.

Further, the microcomputer 45 determines that the detected vehicle speed v when the steering operation of the steering wheel 17 is stopped is reduced to a predetermined reference vehicle speed vR as a hydraulic pressure release process.
(E.g., less than 10 km / h), the valve opening time of the electromagnetic on-off switching valve 21 is set to a predetermined first predetermined time.
The valve opening time (for example, 2 seconds). Also, the microcomputer 45
When the vehicle speed v is equal to or higher than the reference vehicle speed vR, the valve opening time is set to a predetermined second valve opening time (for example, one second) shorter than the first valve opening time.

When the vehicle speed v is equal to or higher than the reference vehicle speed vR, the time during which the hydraulic pressure is released from the oil supply / discharge passages 27a and 27b is limited by the hydraulic pressure release process. This is to prevent the steering from being performed in spite of the state in which the steering of the steering wheel 17 is stopped, and to prevent the relationship between the steering wheel angle θH and the tire angle θT from shifting. That is, when the vehicle speed v is equal to or higher than the reference vehicle speed vR, if the oil pressure release process is performed while the steering of the steering wheel 17 is stopped, the two oil chambers R1 and R2 are communicated by the communication pipe 41. Rear wheel 15R, 15L
This is because the rear wheels 15R and 15L may be steered even though the steering of the steering wheel 17 is stopped by the force received from the road surface.

Next, the operation of the hydraulic power steering apparatus configured as described above will be described. When the steering wheel 17 is steered to the right during traveling, for example, pulse signals PA and PB are output from the steering wheel angle sensor 38 to the microcomputer 45. The microcomputer 45 controls the electric motor 1 based on the number of pulses of the pulse signals PA and PB in the hydraulic oil supply / discharge processing.
The number of rotations is controlled so that a flow rate of hydraulic oil according to the steering speed of the steering wheel 17 is supplied to the hydraulic oil supply / discharge control valve 20. Further, the hydraulic oil supply / discharge control valve 20 is operated by right steering of the handle 17, and the hydraulic oil supplied from the hydraulic pump 19 is supplied to the left oil chamber R <b> 1 of the power cylinder 16. As a result, the power cylinder 16 operates in the right steering direction, and the rear wheels 15R and 15L are steered to the right in accordance with the steering amount of the steering wheel 17. The same applies to the case where the steering wheel 17 is steered to the left. Therefore, the electric motor 15 is operated only when the steering wheel 17 is steered, and the rear wheels 15R and 15L are moved by the power cylinder 16 to the steering wheel 1.
7 is steered according to the steering direction and the steering amount.

In the steering wheel angle correction process, the microcomputer 45 sets the target steering wheel angle θ with respect to the input tire angle θT.
When the deviation angle Δθ between Hd and the steering wheel angle θH exceeds the allowable value θR, the steering wheel angle correction processing is executed. Therefore, when the relationship between the steering wheel 17 and the rear wheels 15R and 15L deviates greatly from the normal relationship, the steering wheel angle θ
H is corrected so as to approach the target steering wheel angle θHd.

If the steering wheel 17 is steered to the right, for example, so that no steering force is applied to the steering wheel 17, the reaction oil from the rear wheels 15R, 15L steered to the right causes the hydraulic oil supply / discharge control valve to move from the left oil chamber R1. High oil pressure is sealed in the oil supply / discharge passage 27b up to 20. When the steering of the steering wheel 17 is stopped,
The microcomputer 45 executes a hydraulic pressure release process.

In the hydraulic pressure release process, the microcomputer 45
0.3 seconds after the steering of the steering wheel 17 is stopped, the electromagnetic open / close switching valve 21 is opened for 2 seconds.
Then, the supply / discharge oil passage 27a is communicated with the supply / discharge oil passage 27b,
The high oil pressure trapped in the oil supply / discharge passage 27a is released.

When the steering wheel 17 is further steered to the right from this state, the spool 35a that has returned to the neutral position PN moves toward the right steering position PR and the electric motor 1
8 is operated, and the hydraulic pump 19 is driven. Spool 3
When the steering wheel 17 is steered to the right until the steering wheel 5a is located at the right steering position PR, the supply / discharge conduit 27b is connected to the supply side of the hydraulic pump 19 via the supply pump 36. At this time,
Only a short time has elapsed since the electric motor 18 was operated, and the flow rate of the hydraulic oil supplied from the hydraulic pump 19 is in communication with the supply pump 36 even if the amount of steering oil of the steering wheel 17 is insufficient. Since the hydraulic pressure of the supplied oil supply / discharge passage 27a is released, the steering wheel 17 does not have a large resistance to the right steering. Therefore, the steering force of the steering wheel 17 does not temporarily become excessively large when the steering wheel 17 that is steered to the right is not subjected to the steering force once and then steered to the right again.

When the handle 17 is steered to the right and stopped when the handle 17 is held at the handal angle θH, a high oil pressure is sealed in the supply / discharge oil passage 27a including the left oil chamber R1. Also in this case, the high oil pressure trapped in the supply / discharge oil passage 27a is released by the oil pressure release processing executed by the microcomputer 45.

In this case, the spool 35a is moved to the right steering position P.
The supply pump 36 is operated while the handle 17 has no play, and the electric motor 18 is driven to drive the hydraulic pump 19. Accordingly, although the flow rate of the hydraulic oil supplied from the hydraulic pump 19 is further insufficient for the steering of the steering wheel 17, the right steering of the steering wheel 17 is steered because the high oil pressure sealed in the oil supply / discharge passage 27 b is released. There is no great resistance to Therefore, even when the steering wheel 17 is steered to the right again while holding the steering wheel 17 steered to the right, the steering force of the steering wheel 17 does not temporarily become excessive.

When the steering is stopped after the steering wheel 17 is steered to the maximum turning angle side and the tire angle θT is equal to or larger than the reference tire angle θTR, the microcomputer 45 does not execute the hydraulic pressure release processing. Accordingly, when the steering wheel 17 is steered to the right and the tire angle θT reaches the maximum turning angle, the hydraulic pressure release process is not performed and the communication conduit 41 is not communicated. There is no deviation.

Further, when the vehicle speed v is equal to or higher than the reference vehicle speed vR, when the steering of the steering wheel 17 is stopped, the microcomputer 45 opens the electromagnetic on / off switching valve 21 in the hydraulic pressure release process for a first valve opening time (for example, 2 seconds). The valve is opened for a second valve opening time (for example, one second) set shorter than the above.

Accordingly, when the vehicle speed v is equal to or higher than the reference vehicle speed vR, the time during which the communication pipe 41 is communicated is restricted by the hydraulic pressure release processing as compared with the case where the vehicle speed v is lower than the reference vehicle speed vR. The rear wheels 15R and 15L are not steered even though they are not.

As described in detail above, according to the hydraulic power steering apparatus of the present embodiment, the following effects can be obtained. (1) When steering of the steering wheel 17 is stopped, the high oil pressure sealed in the oil supply / discharge passage 27a (27b) communicating with the power cylinder 16 is released by the reaction force from the tires of the rear wheels 15R and 15L. I made it. As a result, handle 1
When the steering wheel 7 is re-steered in the same steering direction, the oil pressure on the supply / discharge oil passages 27a and 27b does not become a large resistance to the steering of the steering wheel 17. Therefore, when the steering wheel 17 is not being steered, the electric motor 18 for driving the hydraulic pump can be stopped. In addition, when the steering wheel 17 is once stopped and then steered in the same steering direction again, the steering force is reduced. It can be temporarily prevented from becoming excessive.

(2) When the steering wheel 17 is steered to the maximum turning angle and stopped, and when the tire angle θT is equal to or larger than the reference tire angle θT, the high oil pressure sealed in the oil supply / discharge passage 27a (27b) is released. I did not. Therefore, when the steering of the steering wheel 17 causes the tire angle θT to reach the maximum turning angle and the steering is restricted, the steering wheel 17 is not steered while the steering of the rear wheels 15R and 15L is restricted. As a result, the steering wheel 17 and the two rear wheels 15R, 1R are removed by the hydraulic pressure release processing for preventing a temporary increase in the steering force.
5L can be prevented from deviating from the normal relationship.

(3) When the vehicle speed v is equal to or higher than the reference vehicle speed vR, the oil supply / drain passage 27a
The time for releasing the high oil pressure enclosed in (27b) is limited to a short time. Therefore, by the hydraulic pressure release processing executed when the vehicle speed v is high, it is possible to prevent the two rear wheels 15R and 15L from being steered by the force received from the road surface even when the steering wheel 17 is not steered.

(4) In order to eliminate the deviation of the steering wheel angle θH from the regular target steering wheel angle θHd with respect to the tire angle θT, an electromagnetic wave provided on the communication line 41 connecting the two oil supply / discharge passages 27a and 27b. The open / close switching valve 21 is used to release high oil pressure sealed in the oil supply / discharge passage 27a (27b). Therefore, a hydraulic power steering device that performs control to eliminate such a deviation of the steering wheel angle θH includes:
This can be implemented without changing the hydraulic circuit or adding a new electromagnetic control valve.

(5) When the steering of the steering wheel 17 is stopped, the electromagnetic open / close switching valve 21 is controlled for a predetermined opening time to release the high oil pressure trapped in the supply / discharge oil passages 27a and 27b. . Therefore, there is no need to detect the oil pressure of the supply / discharge oil 27a, 27b and perform control based on the detected value, and the electrical configuration can be simplified.

(6) The steering angles of both rear wheels 15R, 15L are
The tire angle sensor 37 detects the tire angle θT. Therefore, the handle 17 and both rear wheels 15R,
Since the actual tire angle θT can be detected irrespective of the deviation from the reference wheel angle 15L, the reference tire angle θTR can be set to a value close to the maximum turning angle.
By not releasing the oil pressure only when the steering wheel 5L is steered to the maximum turning angle, it is possible to prevent a temporary increase in the steering force when the steering wheel 17 is re-steered over a wide range.

(7) The present invention was applied to a hydraulic control device in which the number of revolutions of the electric motor 18 for driving the hydraulic pump 19 is controlled according to the steering speed of the steering wheel 17. Therefore, handle 1
7, the flow rate of the hydraulic oil supplied from the hydraulic pump 19 at the time of re-steering of the steering wheel 17 becomes further insufficient as compared with the hydraulic control device in which the electric motor is driven at the same rotation speed regardless of the steering speed. The effect obtained by releasing the high oil pressure sealed in the oil supply / discharge passages 27a and 27b becomes remarkable. As a result, by controlling the rotation speed in accordance with the steering speed of the steering wheel 17, it is possible to suppress the consumption of battery power, and to effectively suppress a temporary increase in the steering force when the steering wheel 17 is re-steered. can do.

Note that the embodiment is not limited to the above-described embodiment, and may be implemented as in the following different examples. ○ Implement for hydraulic power steering systems that do not perform steering wheel angle correction processing.

For example, the electromagnetic open / close switching valve 21 provided in the connecting pipe line 41 connecting the two oil supply / discharge oil paths 27a and 27b is used only for the hydraulic pressure release processing. Alternatively, the communication pipe 41 and the electromagnetic opening / closing switching valve 21 are not provided, and as the electromagnetic control valve, a relief valve newly connected to both the supply and discharge oil passages 27a and 27b, and the supply and discharge oil passages 27a and 27
An electromagnetic on-off valve provided between b and the relief valve is provided. Then, the microcomputer 45 closes the electromagnetic on-off valve when the steering wheel 17 is being steered, and opens the electromagnetic on-off valve when the steering of the steering wheel 17 is stopped. Then, the high oil pressure enclosed by the reaction force from the steered wheels 15R, 15L is released. In this case, even if the steered handle 17 is not held and the spool 35a of the supply / discharge switching valve 35 returns to the neutral position PN, the high hydraulic pressure sealed in the two supply / discharge oil passages 27a, 27b. Can be drained to the oil tank 22. Therefore, high hydraulic pressure can be reliably released in a short time, and the handle 17
Even when the steering is stopped for a short period of time, the enclosed hydraulic pressure can be sufficiently released. As a result, even when the steering of the steering wheel 17 is stopped for a short time,
It is possible to ensure that the steering force does not become excessive when the steering is performed again.

The oil supply / drainage passage 27 separate from the communication line 41
A conduit connecting the valves a and 27b is provided, and an electromagnetic switching valve having a larger cross-sectional area than the electromagnetic switching valve 21 is provided on the conduit. When the steering angle θH is corrected, the supply / drain oil passages 27a and 27b are communicated with each other by the electromagnetic opening / closing switching valve 21 and when the high oil pressure is released, by the newly provided electromagnetic opening / closing switching valve having a large flow path cross-sectional area. Let it do. In this case, the valve opening time required for sufficiently releasing the enclosed high oil pressure can be shortened, so that the high oil pressure can be reliably released while the steering of the steering wheel 17 is stopped. Handle 17
When the steering wheel is steered, the steering force can be reliably prevented from becoming excessive.

The steering wheel angle θ is used instead of the tire angle θT.
When H is equal to or larger than the predetermined reference steering wheel angle, and when the steering direction is on the maximum turning angle side, the oil pressure of the oil supply / discharge oil passages 27a and 27b may not be released. In this case, the same effect can be obtained.

The hydraulic pressure release processing may be performed only when the vehicle speed v is lower than the reference vehicle speed vR. in this case,
When the vehicle speed v is equal to or higher than the reference vehicle speed vR, both rear wheels 15
R, 15L can be prevented from being steered by the resistance force from the road surface.

When the hydraulic pressure release process is being performed based on the stop of the steering of the steering wheel 17, the steering wheel 1
When it is detected that the steering wheel 7 has been steered again, the hydraulic pressure release processing is interrupted. In this configuration, when the steering wheel 17 is steered again and the tire angle θT reaches the maximum turning angle during the execution of the hydraulic pressure release process in a state where the tire angle θT is equal to or larger than the reference tire angle θTR due to the steering of the steering wheel 17. In addition, since the hydraulic pressure release process is stopped, the relationship between the handle 17 and the rear wheels 15R and 15L can be prevented from shifting.

A hydraulic power steering device may be used in which the number of revolutions of the electric motor 18 for driving the hydraulic pump 19 is not controlled in accordance with the steering speed of the steering wheel 17. Also in this case, the effects described in (1) to (6) can be obtained.

The present invention is applied to a hydraulic power steering device provided in a cargo handling vehicle other than the forklift 10. ○ Implemented in all-hydraulic hydraulic power steering devices installed in industrial vehicles such as construction vehicles and agricultural vehicles, as well as cargo vehicles.

Hereinafter, in addition to the inventions described in the claims, the technical ideas grasped from the above-described embodiments will be described together with their effects. (1) The invention according to claim 6, further comprising steering detection means for detecting that the steering wheel has been turned from a stopped state, wherein the valve control means controls the electromagnetic on / off switching valve to an open state. When it is detected that the steering wheel has been steered, the electromagnetic open / close switching valve is switched from the open state to the closed state at the time when the valve opening time does not end.

According to such a structure, the steering of the steering wheel is stopped, and while the high oil pressure sealed in the oil supply / drain passage is being released, the steering wheel is again steered, and the steered wheels are turned to the maximum turning angle. Is restricted, the relationship between the steering wheel and the steered wheels can be prevented from shifting.

(2) In the invention described in claim 6, the steering angle detecting means is a tire angle sensor. With such a configuration, it is possible to prevent a temporary increase in the steering force during re-steering over a wide range by not releasing the oil pressure only when the steered wheels are surely steered to the maximum turning angle.

(3) In the invention according to any one of claims 1 to 6, a steering speed detecting means (the steering wheel angle sensor 38, the microcomputer 45) for detecting the steering speed of the steering wheel is provided. Motor drive means (microcomputer 45, motor drive means) for driving the electric motor at a rotational speed corresponding to the steering speed;
Motor drive circuit 46). According to such a configuration, it is possible to suppress the consumption of battery power by controlling the rotation speed in accordance with the steering speed of the steering wheel, and furthermore, it is possible to effectively increase the steering force when the steering wheel is re-steered. Can be suppressed.

(4) In the invention according to any one of claims 4 to 6, when the detected vehicle speed is equal to or higher than the reference vehicle speed, the vehicle speed response control means controls the hydraulic pressure of the supply / discharge oil passage. The valve control means is controlled so as not to pull out.
According to such a configuration, when the vehicle speed is high, the relationship between the steered wheels and the steering wheel can be reliably prevented from shifting.

(5) In the invention as set forth in claim 6, the vehicle speed response control means includes: when the vehicle speed is equal to or higher than the reference vehicle speed, when the vehicle speed is lower than the reference vehicle speed.
The valve control means is controlled so as to shorten the valve opening time of the electromagnetic switching valve. According to such a configuration, only by controlling the valve opening time, the degree to which the oil pressure in the supply / discharge oil passage is released can be limited, and the control content is simplified.

[0089]

According to the present invention, the electric motor for driving the hydraulic pump is stopped when the steering wheel is not being steered. When steering in the same steering direction, it is possible to prevent the steering force from becoming temporarily excessive.

According to the third to seventh aspects of the present invention, when the steering wheel is steered to the maximum, the relationship between the steering wheel and the steered wheels is prevented from being shifted due to the operation of the electromagnetic control valve. be able to.

According to the present invention, when the vehicle speed is high, the steered wheels are hardly steered regardless of the steering of the steering wheel, and the relationship between the steering wheel and the steered wheels is shifted. It can be difficult.

According to the fifth to seventh aspects of the present invention, the hydraulic circuit is changed or a new electromagnetic circuit is provided for a hydraulic power steering apparatus that corrects the deviation of the steering wheel from the normal steering wheel. It can be implemented without adding a control valve.

According to the sixth and seventh aspects of the present invention, there is no need to perform control based on the hydraulic pressure controlled by the electromagnetic control valve, and the electrical configuration can be simplified.

[Brief description of the drawings]

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

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

FIG. 3 is a block diagram showing an electrical configuration.

FIG. 4 is a configuration diagram of a hydraulic power steering device.

[Explanation of symbols]

10 forklift as an industrial vehicle, 16 hydraulic power cylinder, 17 handle, 18 electric motor, 1
9: Hydraulic pump, 20: Hydraulic oil supply / discharge control valve, 21: Electromagnetic open / close switching valve as an electromagnetic control valve constituting hydraulic pressure release means, 22: Oil tank, 27a, 27b: Supply / discharge pipe as supply / drain oil passage Road, 37: a tire angle sensor as a steering angle detecting means, 38: a steering wheel angle sensor constituting a hydraulic pressure releasing means, a hydraulic oil supply / discharge controlling means, a steering direction detecting means, and a steering stop detecting means, 40: a vehicle speed detecting means Vehicle speed sensor,
41: a connecting pipe as a connecting oil path; 45: hydraulic pressure releasing means, hydraulic oil supply / discharge control means, steering stop detecting means, valve control means, steering direction detecting means, vehicle speed detecting means, and steering constituting a deviation angle correcting means A microcomputer as response control means and a vehicle speed response control means; 46, a motor drive circuit constituting hydraulic oil supply / discharge control means; 47, an electromagnetic valve drive circuit constituting hydraulic pressure release means, valve control means and deviation angle correction means; R1, R2: oil chamber, vR: reference vehicle speed, Δθ: deviation angle, θHd: target handle angle, θR: allowable value, θTR:
Reference tire angle as reference steering angle.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B62D 113: 00 F term (Reference) 3D032 CC01 CC48 CC49 CC50 DA02 DA03 DA04 DA09 DA23 DC08 DC09 DC33 DC34 DD01 DE02 DE09 EB11 EC03 EC18 GG04 GG06 GG11 3D033 EB02 GA05 HA03 3F333 AA02 AB13 FA20 FD09 FE09 FH08

Claims (7)

[Claims] When a steering wheel is steered, an electric motor for driving a hydraulic pump is operated, and a hydraulic oil supply / discharge control valve operated by steering the steering wheel is operated by a hydraulic oil supplied from the hydraulic pump. In a hydraulic power steering apparatus that supplies a hydraulic pressure to a power cylinder in accordance with a steering direction and a steering amount of the steering wheel, wherein the hydraulic pressure sealed in a supply / discharge oil passage connecting the supply control valve and the power cylinder is used to stop the steering of the steering wheel. A hydraulic power steering device provided with a hydraulic pressure releasing means for sometimes releasing the hydraulic power steering device. 2. The hydraulic pressure release means includes: an electromagnetic control valve provided to hold or release the hydraulic pressure of the supply / drain oil passage; and a steering stop detection means for detecting that the steering of the steering wheel has stopped. When it is not detected that the steering of the steering wheel has stopped, the electromagnetic control valve is controlled so as to maintain the hydraulic pressure of the oil supply / drain passage, and when it is detected that the steering of the steering wheel has stopped, 2. The hydraulic power steering apparatus according to claim 1, further comprising valve control means for controlling the electromagnetic control valve so as to release the oil pressure of the oil discharge passage. Each time the steering wheel is steered, a steering direction detecting means for detecting a steering direction and newly storing the steering direction; a steering angle detecting means for detecting a steering angle of the steered wheel; Is detected to have stopped,
When the detected tire angle is equal to or greater than a predetermined reference steering angle, and when the stored steering direction is the straight-ahead state direction, the control to release the oil pressure of the oil supply / drain passage is allowed; When the stored steering direction is the maximum turning angle direction, a steering response control unit that controls the valve control unit so as to prohibit the control by the valve control unit to release the oil pressure of the supply / drain oil passage; and The hydraulic power steering device according to claim 2, comprising: 4. A vehicle speed detecting means for detecting a vehicle speed, wherein when the detected vehicle speed is equal to or higher than a predetermined reference vehicle speed, an oil pressure in the supply / discharge oil passage is reduced with respect to when the vehicle speed is lower than the reference vehicle speed. 4. The hydraulic power steering apparatus according to claim 2, further comprising: a vehicle speed response control unit that controls the valve control unit so as to limit the vehicle speed. 5. The electromagnetic control valve is provided on a communication oil passage connecting the two oil supply / drain passages, and a target handle angle of the handle preset with respect to the tire angle, and the detected handle detected. A deviation angle correction means for controlling the electromagnetic control valve when the steering wheel is steered so that when the deviation angle from the angle is equal to or greater than a predetermined allowable value, the deviation angle is less than the allowable value. The hydraulic power steering device according to any one of claims 2 to 4, further comprising: 6. The electromagnetic control valve is an electromagnetic on / off switching valve, and the valve control means sets the electromagnetic on / off switching valve in advance when it is detected that the steering of the steering wheel is stopped. The valve is controlled to be open for a predetermined valve opening time.
The hydraulic power steering device according to any one of claims 1 to 5. 7. An industrial vehicle equipped with the hydraulic power steering device according to claim 1.