JPS61205557A - Fully hydraulic type power steering device - Google Patents

Abstract

PURPOSE:To correct the handle position corresponding to the position of steering wheels through the outflow of actuating oil by providing an actuating oil outflow means that is controlled and operated by the control signal coming from a control means. CONSTITUTION:A steering unit 2 is operated by a handle 1 and a steering cylinder 3 steers steering wheels. Hydraulic lines 4 and 5 connect the steering unit 2 and the steering cylinder 3. Hydraulic line actuating oil outflow means 6 and 7 are provided and a handle rotary angle signal theta1 and a wheel steering angle corresponding signal theta2 are input to the actuating oil outflow means 6 and 7. The difference between the actual detection value and control target value A is computed. If this difference exceeds a preset value, a control means that outputs the control signals (a) and (b) for correcting the position of the handle 1 is provided. Besides, such residual pressure mechanisms 9 and 10 that save the pressure in a degree where the steering cylinder 3 can be positioned and held at the actuating oil outflow are provided in the actuating oil outflow means 6 and 7.

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. 14 is known. (Refer to "Nissan Giho, 19" published by Nissan Motor Co., Ltd. on December 9, 1981; pages 170-171) This conventional device 100 is a steering unit operated by a steering wheel lot.
and a steering cylinder 1 that steers the steering wheel 103.
04 (actuator), and hydraulic lines 105 and 106 that connect 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, 11O is a steering chain, Ill is a fixed wheel, and 112 is a steering wheel spoke.
By steering 03 to the right, the vehicle can turn left.

Therefore, by rotating the steering wheel 101 in the steering direction, an amount of pressure oil sent from the steering pump 107 that is proportional to the rotation angle of the steering wheel is sent from the steering unit 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 101.

(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 lines 105 and 1.
06, and there was no steering gear or mechanical link, there was a discrepancy between the amount of oil sent to the steering cylinder 104 and the rotation angle of the steering wheel 101 due to oil leaks in the steering gear 102. As a result, the relative directional positions of the handle spokes 112 and the steered wheels 103 may change.

In particular, if the steering wheel 101 is deviated from the neutral position even though the steering wheel 103 is 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 101, the steering wheel 103 is actually in the straight-ahead neutral position. There were times when I would run away.

With the aim of solving these problems, the present applicant has filed an application (Japanese Patent Application No. 1983-1983) with the content shown in Figure 15.
No. 117881, 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),
The actual value from (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 (a) is set so that the actual value matches the target value.
) 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 hydraulic line 105. l.

16, the pressurized oil was drained from one side of the handle lO1 and the handle lO1 was rotated idly to correct the handle position. Looking at the pressure change in the steering cylinder 104 on the side where the steering cylinder 104 is located, the pressure suddenly drops to the atmospheric pressure level due to the drain after the 1-position correction start point, and the pressure is no longer transmitted to one of the pistons in the steering cylinder 104. The pressure applied to the left and right sides of the piston becomes significantly unbalanced, resulting in a situation in which the position of the steering cylinder 104 cannot be maintained as it is against the external force applied from the steering wheel 103.

In other words, the steered wheels 103 have a self-returning function such as an elastic restoring force due to the ground pressure distribution with the road surface in the steered state, and this self-returning force becomes the force that moves the steering cylinder 104 during position correction, and is originally In this case, an attempt is made to correct the position of the steering wheel lot without changing the turning position of the steering wheel 103, but the steering wheel 103 sometimes rotates in the straight direction when the position is corrected due to the leakage of hydraulic oil.

Therefore, even though the operator is steering in a predetermined direction,
On the contrary, the steering wheel 103 sometimes returned to the straight direction, causing a feeling of discomfort in steering and unstable vehicle behavior.

(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 claims shown in FIG. In a fully hydraulic power steering device comprising hydraulic lines 4 and 5 connecting the.

A hydraulic oil outflow means 6.7 is provided in the hydraulic line, and a steering wheel rotation angle signal (θ1) and a wheel turning angle equivalent signal (θ2) are inputted to the hydraulic oil outflow means 6.7 to obtain the actual detected value. and the control target value A, and if this difference exceeds a predetermined value, a control signal (a) for correcting the position of the handle l is generated.
, (b), and a residual pressure mechanism 9 that leaves enough pressure in the hydraulic oil outflow means 6 and 7 to maintain the position of the steering cylinder 3 when one hydraulic oil spills;
lO was provided.

(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.

When the steering wheel position is corrected, even if a self-returning force is applied to the steering cylinder from the steering wheel, by providing a residual pressure mechanism in the hydraulic oil spill means, this residual pressure mechanism will transmit pressure into the steering cylinder. is not interrupted, and the position of the steering cylinder can be maintained as it is.

(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 structure of the first embodiment shown in FIGS. 2 to 8 will be explained.

IO 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
The steering pump 12 is a valve mechanism that 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. Motsu.

14 is a steering cylinder, which is attached to the vehicle body l.
A cylinder rod 16.16 fixed to 5, a cylinder tube 17 which is a movable member, and the cylinder tube 1
A piston 18 that reciprocates within 7 is provided.

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. 24.25 is a drain oil line connected to the hydraulic line 21.22. An electromagnetic switching valve 26, 27 is provided in the middle of this drain oil line 24, 25, and when one of the electromagnetic switching valves 26, 27 is opened, hydraulic oil from one side of the hydraulic line 21, 22 is transferred to the hydraulic oil tank 23. The handle position is corrected by flowing the water to the

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

As shown in FIG. 3, the electromagnetic switching valves 26, 27 are equipped with solenoids 31, 32 and springs 37, 36, 35, 36, and 35, which switch between the one-way valve sections 33, 34 and the drain sections 35, 36.
38, and an orifice 39.40 (residual pressure mechanism) provided in the middle of the drain oil line 24.25.

A specific example of the electromagnetic switching valve 26 will be explained with reference to FIG. spring 3
7, movable spool 41, check sleeve 42, orifice 39, one-way valve boat 43, valve frame 44, port frame 45. Input boat 46, output boat 47. guide 48
It is equipped with

The input port 46 is connected to the drain oil line 24 on the hydraulic line 21 side, and the output port 47 is connected to the drain oil line 24 on the hydraulic oil tank 23 side.

Therefore, when the solenoid 31 is de-energized, the spring 3
The one-way valve boat 43 is closed at the tip of the movable spool 41 which is biased by 7, allowing only flow from the output port 47 to the input port 46 via the orifice 39.
This is a state in which a so-called one-way valve is interposed (one-way valve part 33 side switching state), and when the solenoid 31 is energized, the movable spool 41 is pulled up against the spring 37, so that the input port 46 and The output boats 47 are brought into communication via the orifice 39 (switched state to the drain section 35 side).

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 (&) and (b) are output to the solenoid 31.32 of the electromagnetic on-off valve 26.27. It is something.

A specific example of the steering wheel rotation angle sensor 29 will be explained with reference to FIG. 5 and FIG. The steering wheel rotation angle sensor 29 is fixed to the shaft 54 of the structure, and the steering wheel rotation angle sensor 29 is attached to the steering column 55.

Therefore, when the steering shaft 50 is rotated during steering, the rotation decelerated by the worm 51 and the worm wheel 53 is input to the shaft 54, and the degree of rotation of the shaft 54 is converted into an electrical signal by the steering wheel rotation angle sensor 29. This allows the steering wheel rotation angle to be measured.

Further, the control unit 28 includes an A-D conversion circuit 281 and an A-D conversion circuit 282, as shown in FIG.
．． RAM (random access.

memory) 283, ROM (read, only, memory) 284, clock circuit 285. It is composed of a CPt7 (central processing unit) 286 and a position correction signal generation circuit 287.

The A-D conversion circuit 281 is a circuit that converts a steering wheel rotation angle signal (θ゛) input as an electrical 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

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. ing.

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

The CPU 286 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 switching valves 26 and 27 is switched to the drain section side, and the hydraulic oil is drained for the signal output time.

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

First, the CPU 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 on 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. 7, the handle rotation angle on is θl
If so, the target cylinder stroke xn becomes xt.

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

For example, in FIG. 7, the actual cylinder stroke x
Let n be x2. In step 203, the actual cylinder stroke xn is set as a function f (t) of time t, and depending on whether the slope of this function, that is, the value differentiated by the 2-hour meter, is positive or negative. , determine whether the steering direction is right or left.

Note that this steering direction determination may be made using the steering wheel rotation angle θn 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 xm
A stroke difference δ between the target cylinder stroke xn and the target cylinder stroke xn is calculated.

For example, as shown in FIG. 7, xm is x2 and xn
If is XI, the stroke difference δ is δI = X2-X
It is obtained by calculating I.

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 switched to the drain section 36 side, and through the drain oil pipe 25 and the electromagnetic on-off valve 27 provided in this hydraulic line 22,
The position of the handle 10 is corrected by letting the hydraulic oil escape into the hydraulic oil tank 23 and rotating the handle 10 idly in the steering direction without changing the cylinder stroke.

For example, in FIG. 7, if δl>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 move the handle 10.
position correction is performed.

The above control operation is repeated at predetermined time intervals to correct the position of the handle 10 in the delay direction.

The hydraulic oil drained when correcting the position of the steering wheel 10 due to this hydraulic oil leakage passes through one of the orifices 39 and 40, so the flow rate is restricted by the orifice 39 and 40, and the flow rate is limited by the orifice 39 and 40. pressure will not drop suddenly.

In other words, draining is performed in the same manner as part of the pressurized oil supplied from one of the hydraulic lines 21 and 22 is diverted to the drain side, and pressure transmission to the inside of the steering cylinder 14 is also cut off. Even if the self-returning force acts on the steering cylinder 14 from the steering wheel 19,
The position of the steering cylinder 14 can be maintained as it is.

By maintaining the position of the steering cylinder 14 in this manner, the steering wheels 19 are prevented from rotating in the straight forward direction opposite to the steering direction during position correction, thereby eliminating the sense of discomfort in steering. The stability of vehicle behavior during steering also increases.

Furthermore, when correcting the position of the handle 10, if the steering cylinder 14 moves somewhat due to excessive self-returning force being applied from the steering wheel 19, the hydraulic line and cylinder chamber on the side that is not drained will be moved by the amount of movement. The volume expands, and the negative pressure causes bubbles, etc., and it becomes impossible to transmit pressure.

However, the one-way valve portion 33.34 of the electromagnetic switching valve 26.27
Therefore, the hydraulic lines 21 and 22 are connected from the hydraulic oil tank 23 side.
By allowing the hydraulic oil to flow to the side through the drain oil line 24, the hydraulic oil is supplied to the hydraulic line on the side that is not drained due to the pressure difference, and the above-mentioned air bubbles etc. does not occur.

Furthermore, in the first embodiment, the ratio (x/θ) between the handle rotation angle θ and the cylinder stroke X at the control target value A
is set to be smaller than the ratio in the control ideal value B, in most cases the stroke difference δ is larger than the predetermined error δn, and the position of the handle 10 due to hydraulic oil spillage can be frequently corrected. At the same time, since the position control is performed in the delay direction, the steering feeling is comfortable and preferable.

Next, a second embodiment shown in FIGS. 9 and 10 will be described.

In this second embodiment, hydraulic lines 21 and 22 are connected by a connecting line 60, and an electromagnetic switching valve 61 or 62.
62 is provided, and when the electromagnetic switching valve 61 or 62.62 is excited (at the time of position correction), the hydraulic line 21.22 is brought into communication through the connection line 60.

Here, in the second embodiment shown in FIG. 9, a single electromagnetic switching valve 61 is shared, and in this example, the steering direction is determined in the arithmetic processing by the control means 28 (not shown). It is not necessary and can be easily configured.

Further, the second embodiment shown in FIG. 10 is configured to add a variable orifice 63 to the connection line 60 to further enhance the residual pressure function.

The other configurations are the same as those of the first embodiment, so some illustrations are omitted, and the same components as those of the first embodiment are given the same reference numerals.

Therefore, in this second embodiment, when correcting the position of the handle 10, the hydraulic lines 21, 22 are communicated with the connecting line 60, and the hydraulic oil tank 2 is connected via the connecting line 60.
3, and the pressure level is almost equal between the left and right hydraulic lines 21 and 22.
Pressure can remain in the hydraulic line on the hydraulic oil outflow side.

Next, a third embodiment shown in FIGS. 11 and 12 will be described.

In this third embodiment, a flow divider valve (a fixed position flow divider valve 64, 64 or a return line side priority valve 65, 65) is provided as a residual pressure mechanism at the rear of one hydraulic oil outflow means, and one flow side of the flow divider valve is provided. is connected to the hydraulic oil tank 23 through drain oil lines 24 and 25, and the other branch side is connected to return lines 66 and 67.
The hydraulic lines 21 and 22 are connected to each other.

In the figure, reference numeral 68.68 is an electromagnetic switching valve for switching between opening and closing, and an orifice 69 is provided in the flow path of both the above-mentioned branched flow 64.65.
is the provision.

The other configurations are the same as those of the first embodiment, so some illustrations are omitted, and the same components as those of the first embodiment are given the same reference numerals.

Therefore, in this third embodiment, when correcting the position of the lX handle 10, a part of the oil amount flowing out of the hydraulic line on the hydraulic oil outflow side is caused to flow into the hydraulic oil tank 23, and the remaining oil amount is By returning the pressure from one return line to the hydraulic line, a sudden drop in pressure can be suppressed.

Next, a fourth embodiment shown in FIG. 13 will be described. This fourth embodiment is an example in which a relief valve 70, 70 is provided as a residual pressure mechanism at the rear of the hydraulic oil outflow means.

In the figure, 71 and 71 are electromagnetic switching valves for switching between opening and closing.

The other configurations are the same as those of the first embodiment, so some illustrations are omitted, and the same components as those of the first embodiment are given the same reference numerals.

Therefore, in this fourth embodiment, even if one of the electromagnetic switching valves 71.71 switches to the drain side and hydraulic oil flows out when correcting the position of the handle 10, the relief valve 70.7
The hydraulic oil will flow out only when the pressure is higher than the predetermined pressure set at 0, and it will be shut off when the pressure is lower than the predetermined pressure.
The pressure can be maintained at the set value.

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 even if there are design changes within the scope of 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.

Further, the residual pressure mechanism is not limited to the embodiments as long as it is a mechanism that can maintain line pressure on the hydraulic oil outflow side.

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.

In addition, since the residual pressure mechanism is provided in the first hydraulic oil outflow means, the transmission of pressure into the steering cylinder is not interrupted when correcting the position of the steering wheel, and the position of the steering cylinder can be maintained. .

[Brief explanation of the drawing]

Figure 1 shows a fully hydraulic power steering system according to the present invention.
Fig. 2 is a plan view showing a three-wheeled forklift truck equipped with the device of the first embodiment;
The figure is a block diagram of the device of the first embodiment, FIG. 4 is a sectional view showing a specific example of the electromagnetic switching valve of the device of the first embodiment, and FIGS. 5 and 6 are the handle rotation angles of the device of the first embodiment. A sectional view and a partially cutaway side view showing a specific example of the sensor, FIG. 7 is a graph showing control target values stored in advance in the control unit of the embodiment device, and FIG. 8 is a graph of the control unit of the embodiment device. A flowchart diagram showing the flow of operation in the CPU, FIG. 9 and FIG. 1θ are schematic diagrams of main parts showing the device of the second embodiment, FIG. FIG. 13 is a schematic diagram of the main parts showing the device of the fourth embodiment, and FIG. 14 is a plan view showing a three-wheeled forklift truck equipped with a conventional fully hydraulic power steering device.
FIG. 15 is a block diagram showing a prior art device;
The figure is a graph showing changes in the hydraulic oil outflow side steering cylinder pressure in the prior art device. 1... Handle 2... Steering unit 3... Steering cylinder 4.5... Hydraulic line 6.7... Hydraulic oil spill means 8... Control means 9.10... Residual pressure mechanism (θ1)...Handle rotation angle signal (θ2)...Wheel turning angle equivalent signal (a)...
Control signal (b)...control signal

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 spill means is provided, and a steering wheel rotation angle signal and a wheel turning angle equivalent signal are input to the hydraulic oil spill 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 hydraulic oil exceeds the position of the steering wheel, and the hydraulic oil spilling means is provided with a residual pressure mechanism that leaves enough pressure to maintain the position of the steering cylinder when the hydraulic oil spills. A fully hydraulic power steering device characterized by: