JPS61200060A - Perfect hydraulic type power steering apparatus - Google Patents

Abstract

PURPOSE:To correct the steering-wheel position for the position of a steered wheel by installing a working-oil flowing-out means for the control operation by a control signal. CONSTITUTION:Working-oil flowing-out means 6 and 7 are installed into the hydraulic lines 4 and 5 for connecting a steering unit 2 and a steering cylinder 3. A steering-wheel turning angle theta1 and a wheel steering angle corresponding signal theta2 are input into a control means 8, which calculates the difference between the actual detection value and an aimed control value A. When the difference exceeds a prescribed value, the control signals (a) and (b) for correcting the position of a steering wheel 1 are outputted. In this case, the ratio of the wheel steering angle theta2 for the steering-wheel turning angle theta1 at the aimed control value A is made less than the ratio at an ideal control value B.

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. 6 is known. (Refer to "Nissan Technical Review, 19" published by Nissan Motor Co., Ltd. on December 9, 1981; pages 170 to 171) This conventional device 100 includes a steering wheel, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a valve mechanism, a steering wheel, a steering wheel, a steering wheel, a valve mechanism, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a valve mechanism, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a valve mechanism, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a valve mechanism, a steering wheel, a steering wheel, a steering wheel, a steering wheel, a valve mechanism, and a steering wheel, which are operated by a handle 101. , a steering cylinder 104 (actuator) for steering a steering wheel 103, and hydraulic lines 105, 106 for connecting the steering unit 102 and the steering cylinder 104.

In addition, what is indicated by 107 in the figure is a steering pump, 10
8 is a hydraulic oil tank, 109 is a vehicle body, 110 is a steering chain, 111 is a fixed wheel, and 112 is a handle spoke. This figure shows the state when steering to the left, and the steering wheel 10
By steering 3 to the right, the vehicle can turn to the left.

Therefore, by rotating the steering wheel in the steering direction, an amount of pressure oil sent from the steering pump 107 that is proportional to the steering wheel rotation angle is sent from the steering gear 102 to the steering cylinder 104 according to the arrow in the figure. .

The pressure oil sent to the steering cylinder 104 enters the steering cylinder 104 through the hollow part of the cylinder rod 141, and since the cylinder rod 141 is fixed to the vehicle body 109, the cylinder tube 104
2 moves in accordance with the amount of oil fed, and rotates the steering wheel 103 connected by the steering chain 110 by an angle corresponding to the rotation angle of the handle LOI.

(Problems to be Solved by the Invention) However, in such a conventional fully hydraulic power steering device, the steering unit 102 and the steering cylinder 104 are connected to the hydraulic line 105.1.
Since it was connected only by 06 and had no steering gear or mechanical link, the steering 22,
Due to oil leakage in the spokes 102, a discrepancy occurs between the amount of oil sent to the steering cylinder 104 and the rotation angle of the steering wheel 101, which may change the relative directional position of the steering wheel spokes 112 and the steered wheels 103. Ta.

In particular, if the steering wheel 101 is deviated from the neutral position even though the steering wheels 103 are in the straight-ahead neutral position, even if the operator tries to turn the steering wheel 101 by relying on the position of the steering wheel 103, the steering wheel 103 is actually in the straight-ahead neutral position. There were times when I would run away.

In order to solve these problems, the present applicant has filed an application (Japanese Patent Application No.
No. 17881, filed on June 8, 1982) was proposed as prior art.

This prior art provides drain oil lines 113, 114 and an electromagnetic switching valve 122 in hydraulic lines 105, 106,
the first and second solenoids 123 of the electromagnetic switching valve 122;
124 as control signals from the controller 125 (a), (
b) to correct the rotation angle of the handle 101 according to the cylinder stroke (corresponding to the steering angle of the steering wheel).

That is, in the controller 125, the steering wheel rotation angle detection means 12 provided on the steering shaft 121
Angle signal (θ) from 0 and steering cylinder 10
The stroke signal (S) from the cylinder stroke detection means 119 provided at 4 is input, and these signals (θ'') are input.
, (S) is compared with a target value stored in advance in the controller 125, and when this difference exceeds a predetermined value, the drive signal (
It outputs a) and (b).

However, in this prior art, if an error of more than a predetermined value occurs in the relationship between the cylinder stroke and the handle rotation angle, the handle 101 is rotated idly to correct the handle position. In setting the target value, if this target value C1 is made to match the ideal value obtained from theoretical calculations without considering oil leaks, etc., the oil amount may fluctuate due to large oil leaks, etc. Unless otherwise specified, the actual value and the target value CI would be within the error range, the position of the handle lO1 would be corrected less frequently, and the error would continue to occur.

Furthermore, if the target value C2 is set in the direction in which the steering wheel lot moves with respect to the steering cylinder 104, as shown in FIG. The situation continued as it had occurred, and furthermore, because it was in the advancing direction (the direction in which the cylinder stroke becomes larger relative to the steering wheel rotation angle), the turning angle of the steered wheels became larger, and the steering feeling was not favorable. There wasn't.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this purpose, the present invention employs the following solving means. did.

The solution of the present invention will be explained with reference to the conceptual diagram of the claim shown in FIG. In the fully hydraulic power steering system, the hydraulic lines 4, 5 are provided with hydraulic oil drain means 6, 7, and the hydraulic oil drain means 6, 7 are provided with a steering wheel rotation angle signal ( θ1) and wheel turning angle equivalent signal (θ2) are input to calculate the difference between the actual detected value and the control target value A, and if this difference exceeds a predetermined value, control is performed to correct the position of the steering wheel 1. Signal (a)
, (b), and the ratio of the wheel turning angle θ2 to the steering wheel rotation angle θ1 of the control target value A is set to be smaller than the ratio of the ideal control value B.

(Function) Therefore, in the fully hydraulic power steering device of the present invention, by using the solution as described above, when steering with the steering wheel, the steering wheel (wheel)
If there is an error in the wheel turning angle, the control unit calculates the difference between the actual wheel turning angle and the target wheel turning angle, and if this difference exceeds a predetermined value, the control unit calculates the difference between the actual wheel turning angle and the target wheel turning angle. By outputting a control signal to the hydraulic oil outflow means, the handle rotates idly due to the outflow of the hydraulic oil, and the handle position can be automatically corrected.

In most cases, this steering wheel position correction is achieved by setting the ratio of the wheel turning angle to the steering wheel rotation angle of the control target value to be smaller than the ratio of the ideal control value.
The difference between the actual wheel turning angle and the target wheel turning angle exceeds a predetermined value, and the steering wheel position is frequently corrected, and furthermore, the wheel turning angle tends to lag behind the steering wheel rotation angle. With this control, the steering feeling is not impaired.

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

In describing the embodiment, a fully hydraulic power steering device for a three-wheeled forklift truck will be taken as an example.

First, the configuration of the embodiment shown in FIGS. 2 to 4 will be explained.

10 is a handle, and this handle 10 is provided with handle spokes 11 to improve operability.

12 is a steering unit, and the handle 1
This steering unit 12 is a valve mechanism, and has the function of sending an amount of pressure oil sent from a steering pump 13, which will be described later, to the steering cylinder 14 in proportion to the rotation angle of the steering wheel. .

A steering cylinder 14 includes cylinder rods 16, 16 fixed to the vehicle body 15, a cylinder tube 17 that is a movable member, and a piston 18 that reciprocates within the cylinder tube 17.

A steering wheel 19 is connected to the cylinder tube 17 by a steering chain 20, 20, and is steered by movement of the cylinder tube 17.

Reference numerals 21 and 22 indicate hydraulic lines that connect the steering unit 12 and the steering cylinder 14, and one of these lines 21 and 22 supplies pressurized hydraulic oil from the steering pump 13 during steering. The other line is a return line that returns oil to the hydraulic oil tank 23.

Note that the cylinder rod 1 is connected to the steering cylinder 14.
The pressurized oil is sent through the hollow part of 6, and the oil is also returned through the hollow part.

A drain oil line 24.25 is connected to the hydraulic line 21.22, and an electromagnetic on-off valve 26.27 is provided in the middle of this drain oil line 24.25. 27, when both are closed, there is no outflow of hydraulic oil, and when one is open, hydraulic oil from one of the hydraulic lines 21 and 22 flows out to the hydraulic oil tank 23, and the handle position is corrected.

In addition, this drain oil line 24, 25 and the electromagnetic on-off valve 2
6.27 constitutes the hydraulic oil outflow means of the embodiment.

28 is a control unit which receives a handle rotation angle signal (θ) from a handle rotation angle sensor 29 and a cylinder stroke signal (S) from a cylinder position sensor 30.
are input, arithmetic processing is performed based on these input signals (θ'') and (S), and control signals (a) and (b) are output to the solenoid 31.32 of the electromagnetic on-off valve 26.27. It is something to do.

The control unit 28 includes a count circuit 281, an A-D conversion circuit 282, and a RAM, as shown in FIG.
(Random, Access, Memory) 283, ROM (
read, only, memory) 284, clock circuit 28
5. CPU (Central).

Processing unit) 28B and position correction signal generation circuit 287.

The count circuit 281 counts the number of pulses of the steering wheel rotation angle signal (θ) input as a pulse signal,
This is a circuit that converts the signal into a digital signal that can be processed by the CPU 286.

The A-D conversion circuit 282 receives a cylinder stroke signal (S) from the cylinder position sensor 30 using a variable resistor.
This is a circuit that converts (an analog signal based on a current value) into a digital signal that can be processed by the CPU 286.

The RAM 283 is a readable and writable memory, and is a circuit that temporarily stores the handle rotation angle signal (θ) and the cylinder stroke signal (S) based on digital signals until the calculation processing time comes.

The ROM 284 is a read-only memory, and this R
OM284 has a table that shows the relationship between the handle rotation angle θ and the cylinder stroke X, which is the control target value.
is stored in the form of

Note that the control target value is set by setting the ratio of cylinder stroke X to handle rotation angle θ to be smaller than the ratio of both θ and X in the ideal control value (shown in graph B), as shown in graph A of Fig. 4. ing.

The clock circuit 285 is a circuit that sets the calculation processing time in the CPU 286.

The CPU 288 is called a central processing unit,
This circuit reads signals written in the RAM 283 and ROM 284, performs arithmetic processing according to a predetermined procedure, and outputs the result signal to the position correction signal generation circuit 287.

The position correction signal generation circuit 287 is a circuit that outputs control signals (a) and (b) to the solenoids 31 and 32 based on the result signal from the CPU 286, and these control signals (a) and (b) are This is an electric signal that operates a solenoid, and when this signal is output to one of the solenoids 31 and 32, one of the electromagnetic on-off valves 26 and 27 is switched to the open side, and the hydraulic oil is drained for the signal output time.

Next, the operation of the embodiment will be explained.

First, the CPO of the control unit 28 shown in FIG.
The control operation for steering wheel position correction will be described with reference to a flowchart showing the flow of the operation at step 286.

First, in step 200, a handle rotation angle signal (0) indicating the actual handle rotation angle ON when the handle 10 is rotated in one direction is read from the RAM 283.

In step 201, based on the handle rotation angle θn read out in step 200, the ROM 284
The target cylinder stroke xn is looked up in a table from the target value A stored in the table.

For example, in FIG. 4, the handle rotation angle θn is 01
If so, the target cylinder stroke xn becomes xl.

In step 202, a cylinder stroke signal (X) indicating the actual cylinder stroke xn at the actual handle rotation angle θn is read from the RAM 283.

For example, in FIG. 4, the actual cylinder stroke x
Let n be x2.

In step 203, the actual cylinder stroke xn is defined as a function f(t) of time t, and depending on whether the slope of this function, that is, the value differentiated with respect to time t, is positive or negative, the steering direction is determined to the right. Determine whether it is on the left.

Note that this steering direction determination may be made using the steering wheel rotation angle on or the target cylinder stroke xn.

Further, in step 203, if the value differentiated with respect to time t is zero, it means that no steering is being performed, and the process proceeds to step 204, where no result signal is output from the CPU 286.

Here, in the case of right steering, in the case of right steering, the process proceeds from step 203 to step 205, and in this step 205, the actual cylinder stroke xn
A stroke difference δ between the target cylinder stroke xn and the target cylinder stroke xn is calculated.

For example, as shown in FIG. 4, xn is x2 and xn
If is Xl, the stroke difference δ is δ1 = X2 - X1
It is obtained by the calculation of

In the next step 206, it is determined whether the stroke difference δ obtained in the step 205 is larger or smaller than a predetermined stroke error δn.

If the relationship is δ≦δn, the process proceeds to step 204 as position correction control is not required, and if δ>
If the relationship is δn, it is assumed that position correction control is required, and the process proceeds to step 207. In this step 207,
A result signal for activating the solenoid 32 is output from the CPU 286.

In other words, when steering to the right, hydraulic oil is sent from the steering unit 12 to the steering cylinder 14 via the hydraulic line 22, contrary to FIG. The valve 27 is opened, and the drain oil pipe 25 provided in this hydraulic line 22 is opened.
The hydraulic oil is transferred to the hydraulic oil tank 2 via the electromagnetic on-off valve 27.
3, and without changing the cylinder stroke,
The position of the handle 10 is corrected by rotating the handle 10 idly in the steering direction.

For example, in FIG. 4, if δ1>δn, only the handle rotation angle θ advances in the direction of arrow E.

Also, in the case of left steering, step 2 is applied similarly to right steering.
08 and step 209, proceed to either step 204 or step 210, and turn the handle lO
position correction is performed.

The above control operation is repeated at predetermined time intervals to correct the position of the handle lO in the delay direction.

In this way, the handle rotation angle θ at the control target value A
By setting the ratio (X/θ) between and cylinder stroke 10 position corrections can be performed frequently.

Further, since the position control is performed in the delay direction, the steering feeling is also favorable and does not feel strange.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, in the embodiment, a cylinder stroke signal is used as a wheel turning angle equivalent signal, but a turning angle signal obtained by directly detecting the turning angle of a steered wheel may also be used.

Furthermore, although the embodiments have shown the opening/closing control of the electromagnetic on-off valve, the outflow flow rate may be controlled by duty ratio control or variable flow rate control.

In addition, although the steering cylinder is shown as a cylinder that operates linearly, it may also be one that performs rotational movement or curved movement.

(Effects of the Invention) As described above, the fully hydraulic power steering device of the present invention is provided with a hydraulic oil draining means that is controlled and activated by a control signal from the control means, so that the steering wheel An effect is obtained in that the handle position relative to the position can be corrected by the hydraulic oil outflow.

Furthermore, since the control target value in the control means is set in such a direction that the wheel turning angle lags behind the steering wheel rotation angle compared to the ideal control value, the angle difference between the two becomes large, causing frequent steering wheel position correction. Furthermore, since the steering wheels are controlled in a delayed direction, the steering feeling is not impaired.

[Brief explanation of drawings]

Fig. 1 is a conceptual claim diagram showing a fully hydraulic power steering device of the present invention, Fig. 2 is a plan view showing a three-wheeled forklift truck equipped with the embodiment device, and Fig. 3 is a block diagram of the embodiment device. Figure 4 is a graph showing control target values stored in advance in the control unit of the embodiment device;
Fig. 5 is a flowchart showing the flow of operations in the CPU of the control unit of the embodiment device, Fig. 6 is a plan view showing a three-wheel forklift truck equipped with a conventional fully hydraulic power steering device, and Fig. 7 is a front view. FIG. 8 is a block diagram illustrating the prior art device, and is a graph illustrating target values in the controller of the prior art device. l...Handle 2...Steering unit 3...Steering cylinder 4...Hydraulic line 5...Hydraulic line 6...Hydraulic oil outflow means 7...Hydraulic oil outflow means 8...Control Means (θ1)...Handle rotation angle signal (02)...Wheel turning angle equivalent signal (a)...
Control signal (b)... Control signal A... Control target value B... Control ideal value Patent application Nissan Motor Co., Ltd. Figure 8

Claims (1)

[Claims] 1) A fully hydraulic power steering device including a steering unit operated by a handle, a steering cylinder that steers a steering wheel, and a hydraulic line that connects the steering unit and the steering cylinder, wherein the hydraulic line is connected to the steering unit. A hydraulic oil spilling means is provided, and a steering wheel rotation angle signal and a wheel steering angle equivalent signal are inputted to the hydraulic oil spilling means, and the difference between the actual detected value and the control target value is calculated, and this difference is determined as a predetermined value. A control means is provided for outputting a control signal for correcting the position of the steering wheel when the control target value exceeds the steering wheel rotation angle, and the ratio of the wheel turning angle to the steering wheel rotation angle of the control target value is set to be smaller than the ratio of the ideal control value. A fully hydraulic power steering device featuring: