JPS60261778A - Fully hydraulic type power steering device - Google Patents

Abstract

PURPOSE:To get rid of any variation in relative positions of both a steering handle and a steering wheel due to oil leakage by supplying pressure oil from a compensating oil pressure supply line into an actuator to compensate the uncoinciding positions of both the steering handle and the steering wheel. CONSTITUTION:When a steering wheel 3 will not be set in the forward traveling neutral position even if a steering handle 1 has been set in the forward traveling neutral position because oil leaks inside a steering unit 2, a change-over operation of manual switching valve 16 causes pressure oil to be supplied from a compensating oil pressure pump 15 into a steering cylinder 4 via one of compensating oil pressure supply lines 13 and 14, turning the steering wheel 3 into the forward traveling neutral position. When the manual switching valve 6 is returned, into the original neutral position, after the identification of the turning action into the forward traveling neutral position of the steering wheel 3, the forward traveling neutral position of both the steering handle 1 and the steering wheel 3 will then coincide with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fully hydraulic power steering system used in vehicles such as forklift trucks and without a steering gear or mechanical link.

(Prior Art) As a conventional fully hydraulic power steering device, for example, a device as shown in FIG. 7 is known. (r8
(Refer to pages 170-171 of "Industrial Technology Report, 19," published by Nissan Motor Co., Ltd., December 1, 1985.) This conventional device operates a steering unit 2 (valve mechanism) operated by a steering wheel l, and a steering wheel 3. The vehicle was equipped with a steering cylinder 4 (actuator) for directing the vehicle to the vehicle, and hydraulic lines 5 and 6 for connecting the steering unit 2 and the steering cylinder 4.

In addition, what is shown by 7 in the figure is a steering pump, 8 is a hydraulic oil tank, 9 is a vehicle body, 10 is a steering chain, 11 is a fixed wheel, and 12 is a handle spoke. This figure shows the state during left steering, and by steering the steering wheels 3 to the right, the vehicle can turn to the left.

Therefore, by rotating the steering wheel l in the steering direction, an amount of pressure oil sent from the steering pump 7 that is proportional to the steering wheel rotation angle is sent from the steering unit 2 to the steering cylinder 4 according to the arrow in the figure.

Then, the pressure oil sent to the steering cylinder 4 enters the steering cylinder 4 through the hollow part of the cylinder rod 41, and since the cylinder rod 41 is fixed to the vehicle body 9, the cylinder tube splitter 42 has an oil supply amount. The steering wheels 3 connected by the steering wheel 3 are rotated by an angle corresponding to the rotation angle of the handle 1.

(Problems to be Solved by the Invention) However, in such a conventional fully hydraulic power steering device, the steering unit 2 and the steering cylinder 4 are connected only by the hydraulic line 5.6, and the steering gear and Since there was no mechanical link, oil in the steering unit 2 leaked, causing a discrepancy between the amount of oil sent to the steering cylinder 4 and the rotation angle of the steering wheel l. There was a possibility that the relative position of the direction could change.

In particular, if the steering wheels 3 are not in the neutral position even though the operator has set the steering wheel spokes 12 in the neutral steering position, the vehicle will not be able to travel straight and the vehicle will have to operate the steering wheel in a hurry. .

(Means for Solving the Problems) That is, the present invention has been made with the aim of solving the above-mentioned problems. A fully hydraulic power steering device that hydraulically steers the steered wheels in response to the operation of the / The actuator is provided with a switching valve for switching an oil path for supplying oil from a hydraulic source, and a correction hydraulic pressure supply line for correcting the position of the steered wheels is provided in the actuator.

(Function) Therefore, when the position of the handle and the position of the steered wheel do not match, the position of the steered wheel can be corrected by supplying pressurized oil to the actuator from the correction oil pressure supply line.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In describing the example, we will take a fully hydraulic power steering device for a three-wheeled forklift truck as an example.
The same parts as those in the conventional structure will be described with the same reference numerals.

First, the configuration of the first embodiment shown in FIGS. 1 and 2 will be explained.

1 is a handle, and this handle 1 is provided with handle spokes 12 for improved operability.

, 2 is a steering unit, which is directly operated by the steering wheel.This steering unit 2 is a valve mechanism, and the pressure oil sent from the steering pump 7, which will be described later, is adjusted to the steering wheel rotation angle. It has a function of sending a proportional amount of oil to the steering cylinder 4.

4 is a steering cylinder, which includes cylinder rods 41, 41 fixed to the vehicle body 9, a cylinder tube 42 that is a movable member, and a piston 43 that reciprocates within the cylinder tube 42.

It is equipped with

Reference numeral 3 denotes a steering wheel, which is connected to the cylinder tube 42 by a steering chain 10, 10, and is steered by movement of the cylinder tube 4.

5.6 is a hydraulic line that connects the steering unit 2 and the steering cylinder 4;
One of the hydraulic lines 5.6 serves as a supply line for supplying pressurized oil from the steering pump 7 during steering, and the other line serves as a return line for returning oil to the hydraulic oil tank.

Note that a cylinder rod 41 is connected to the steering cylinder 4.
The pressurized oil is sent through the hollow part of the cylinder, and the oil is also returned through the hollow part.

Reference numeral 13.14 denotes a correction hydraulic pressure supply line, in which the correction hydraulic pump 15, which is a hydraulic pressure source, and the hydraulic line 13.14 are connected via a manual switching valve 16. 14 has a check valve 17.1
8 is provided so that pressurized oil can be supplied to the steering cylinder 4 only from the correction hydraulic pump 15 side.

ni M, IN, 9. 6.1 2,7 42.
20 is a return line, and when the steering wheel 1 is in a neutral state, all the oil sent from the steering pump 7 to the steering unit 2 passes through the return line 20 and is returned to the hydraulic oil tank 8.

Further, numeral 21 in the figure is a correction hydraulic oil tank.

Next, the operation of the first embodiment will be explained.

During steering, by rotating the steering wheel I in the steering direction, an amount of pressure oil sent from the steering pump 15 that is proportional to the steering angle is sent from the steering unit 2 through one of the hydraulic lines 5 and 6 to the steering wheel. This is done by rotating the steering wheel 3, which is sent to the cylinder 4, by an angle corresponding to the rotation angle of the handle 1.

Even though the steering wheel 1 is set in the straight-ahead neutral position, if oil leaks inside the steering unit 2 and the steering wheels 3 are not in the straight-ahead neutral position, the manual switching valve 1
6 to one side, pressurized oil is sent from the correction hydraulic pump 15 to the steering cylinder 4,'I through one of the correction hydraulic pressure supply lines 13 and 14, and the steering wheel 3 is rotated in the direction of the straight-ahead neutral position 1. make it move.

Then, after confirming that the steering wheel 3 has rotated to the straight-ahead neutral position, the manual switching valve 16 is returned to the original neutral position.
The straight-ahead neutral position of the handle l and the straight-ahead neutral position of the steered wheels 3 can be matched.

Next, a second embodiment shown in FIGS. 3 and 4 will be described.

This embodiment is an example in which the first embodiment is developed so that the straight-ahead neutral position correction operation can be performed only by operating the correction switch 22.

To explain a different configuration from the first embodiment, reference numeral 23 and 24 are limit switches whose contacts face switch plates 25 and 26 provided on the cylinder tube 42, and when the steering cylinder 4 is in the neutral position, both The limit switches 23 and 24 are arranged so that they are open, and one of the limit switches 23 and 24 is closed when the limit switches 23 and 24 are not in the neutral position. - 27 is an electromagnetic switching valve, which connects the first solenoid 28 and the second solenoid.
and a solenoid 29, the limit switch 23.
When the switch 24 is operated, either the first solenoid 28 or the second solenoid 29 is energized and a switching operation is performed.

In the electric circuit of the second embodiment, as shown in FIG. installed in parallel to the circuit.

Note that the other configurations are the same as those in the first embodiment, so the same reference numerals are given and the explanation will be omitted.

Next, the operation of the second embodiment will be explained.

When correcting the straight-ahead neutral position of the steering wheel 3, set the handle 1 to the straight-ahead neutral position and turn on the correction switch 22, then one of the limit switches 23 and 24 will adjust according to the positional deviation of the steering wheel 3. Since the solenoid is closed, the solenoid on the closed switch side is energized from the power supply 30, and the solenoid switches the electromagnetic switching valve 27 to rotate the steered wheel 3 toward the straight-ahead neutral position as in the first embodiment. I can do it.

Note that when the steered wheels 3 are corrected to the straight-ahead neutral position, the limit switches 23 and 24 are both opened, so the electromagnetic switching valve 27 automatically returns to the original neutral position.

Next, a third embodiment shown in FIG. 5 will be described.

While the first and second embodiments only had a straight-ahead neutral position correction function, this embodiment is not limited to the straight-ahead neutral position, and can be applied to any position of the handle l. , this is an example in which the steering angle of the steered wheels 3 can be corrected according to the rotation angle of the steering wheel 1.

To explain the configuration different from the second embodiment, 32 is a steering wheel rotation angle detection means, which is arranged on the steering shaft 31 of the steering wheel 1, detects the steering wheel rotation angle, and outputs an angle signal (θ). be.

33 is a cylinder stroke detection means;
It is arranged with respect to the cylinder tube 42 of the steering cylinder 4, detects the cylinder stroke, and outputs a stroke signal (S).

34 is a controller, which includes an arithmetic circuit that inputs the angle signal (θ) and calculates a target cylinder stroke Sk according to the handle rotation angle θ, and a calculation circuit that calculates the handle rotation angle θ or the target cylinder stroke Sk at a time t. A discrimination circuit that differentiates and discriminates the steering direction compares the actual cylinder stroke Sj from the stroke signal (S) with the cylinder stroke Sk, and determines whether the first solenoid 28
Alternatively, the second solenoid 29 is provided with a comparator that outputs the torque drive signals (a) and (b) to the second solenoid 29. In this example, the handle rotation angle θ, the target cylinder stroke Sk, and the actual cylinder stroke Sj are as follows:
The value with the steering wheel l turned to the far left is set to zero,
It is defined so that the value becomes more positive as the vehicle is steered further to the right.

Note that the other configurations are the same as those of the first and second embodiments, 'A, A6°-c, *-R? y, L-cm#J□, ゛ru.

Next, the operation of the third embodiment will be explained.

Explaining according to the flowchart shown in FIG. 6, first, the handle rotation angle θ is detected by the handle rotation angle detection means 32.

Then, based on the handle rotation angle θ, the controller 34 calculates a target cylinder stroke Sk that is proportional to the handle rotation angle θ.

Next, the actual cylinder stroke Sj is detected by the cylinder stroke detection means 33.

Next, the steering wheel rotation angle θ or the target cylinder stroke Sk is differentiated with respect to the time t, and depending on whether the value is positive or negative, the steering direction 'of the steering wheel l is determined to be right or left steering. Note that if the value is 0 (zero), the handle l is in a fixed state, and the electromagnetic switching valve 27 remains in the neutral position. In other words, in order to avoid giving the driver a sense of discomfort, the position of the steered wheels is not corrected when the vehicle is traveling straight or when the vehicle is holding the steering wheel.

Next, the target cylinder stroke Sk and the actual cylinder stroke Sj are compared, and the actual cylinder stroke Sj
The solenoid drive signal (L), (b) is outputted to the first solenoid 28 or the second solenoid 29, and the electromagnetic switching valve 27 is switched so that the difference between The solenoid 4 is moved to correct the steering angle of the steering wheel 3 in accordance with the rotation angle of the handle l.

Although embodiments of the present invention have been described in detail with reference to the drawings,
The specific configuration is not limited to this embodiment, and any design changes or the like that do not depart from the gist of the present invention are included in the present invention.

For example, the correction hydraulic pump in the embodiment may be used in tandem with a steering pump.

Further, in order to facilitate the operation for correcting the position of the steering wheel, a mechanism may be provided that allows the stroke of the steering cylinder or the position of the steering wheel to be viewed from the driver's seat.

Further, instead of switching the correction hydraulic pressure supply lines using a switching valve, an independent hydraulic pump may be provided for each hydraulic line, and driving or non-driving of this hydraulic pump may be controlled.

Furthermore, for safety, a mechanism may be added that prevents the switching valve from operating unless the vehicle is stopped, and it may also be linked to the handbrake.

In addition, in the second embodiment, if the correction switch is a switch that is automatically turned on when the steering wheel is in the straight-ahead state position (a predetermined range is set), each time the steering wheel passes through the straight-ahead state range, Neutral position correction of the steered wheels is performed.

(Effects of the Invention) As described above, according to the present invention, since the steering wheel position relative to the steering wheel position can be corrected by the correction hydraulic pressure supply line, changes in the relative position between the steering wheel and the steering wheel due to oil leakage can be prevented. This has the effect of eliminating the

14. Ah, □ - Fig. 1 is a plan view showing a three-wheel forklift truck equipped with a fully hydraulic power steering device according to the first embodiment of the present invention, Fig. 2 is a hydraulic circuit diagram showing the device according to the first embodiment, and Fig. 3
The figure is a hydraulic circuit diagram showing the second embodiment device, FIG. 4 is an electric circuit diagram in the second embodiment device, FIG. 5 is a hydraulic circuit diagram showing the third embodiment device, and FIG. 6 is the third embodiment device. FIG. 7 is a plan view showing a three-wheeled forklift truck equipped with a conventional fully hydraulic power steering device.

l... Handle 2... Steering unit 3... Steering wheel 4... Steering cylinder (actuator) 5.
6...Hydraulic line 13.14...Correction hydraulic pressure supply line Patent application Hitori Nissan Motor Co., Ltd. 1 Fig. 1 0 3 Fig. 4\ 0 Fig. 5 558- Fig. 6

Claims (1)

[Scope of Claims] l) A steering unit that is operated by a steering wheel, an actuator that steers a steering wheel, and a hydraulic line that connects the steering unit and the actuator, in response to the operation of the steering wheel, A fully hydraulic power steering device that hydraulically steers a steered wheel includes a hydraulic power source and a switching valve that switches an oil path for oil supplied from the hydraulic source, and supplies correction hydraulic pressure to the actuator to correct the position of the steered wheel. A fully hydraulic power steering device featuring a line. 2] The switching valve is in the neutral position of the handle. The fully hydraulic power steering device according to claim 1, wherein the fully hydraulic power steering device operates upon detecting that the difference between the neutral positions of the actuators exceeds a predetermined value. 3) The switching valve operates upon detecting that the difference between the target stroke of the actuator corresponding to the handle angle and the actual stroke of the actuator exceeds a predetermined value. Fully hydraulic power steering system as described.