JPS59220455A - Self-centering mechanism of power steering device - Google Patents

Abstract

PURPOSE:To return a steering wheel automatically to a neutral position by providing a control device to control an opening degree of a throttle valve in a flow volume control means and a switching operation of a direction changing means. CONSTITUTION:A flow volume contorl means 10 to regulate a flow volume of an operation fluid is provided between a fluid pressure pump 1 and a control valve 4. A directon switching means 24 to change a flow direction of the operation fluid is provided on a branch route at an upper stream side of the flow volume control means 10. A lower stream side of a direction switching means 34 is connected with two fluid pressure chambers 6a of a power cylinder and a suction side of a fluid pressure pump 6b separately and respectively, while at the same time, non-return valves 11 and 12 to stop flow of the operation fluid from a power cylinder 6 to a control valve 4 are provided between both fluid pressure chambers 6a and 6b, and a control valve 4. Also a steering power detecting means 20 and a steering angle detecting means 21 during steering operation are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a self-centering mechanism for automatically restoring the steering wheel to a neutral position (straight running condition) in a power steering device used in a vehicle such as an automobile.

[Prior art]

As an example of a conventional power steering device, there is one shown in FIG. 1, for example. That is, numeral 1 in the figure is a hydraulic pump, and this hydraulic pump 1 sucks the working fluid in the reservoir tank 2, makes it high pressure, and supplies it to the supply circuit 3.
Discharge to. The hydraulic fluid discharged into the supply circuit 3 is supplied to a control pulp 4 that responds to steering operation, and is further circulated to the reservoir tank 2 via a return circuit 5.

The control pulp 4 has four variable apertures 41°, 42.
43.44, with four variable apertures 41,4
2, 43, and 44 are connected in series to form a first aperture group consisting of a first variable aperture 41 and a second variable aperture 42, a third variable aperture 43, and a fourth variable aperture. 44, and both aperture sets are connected in parallel to each other. Then, the first variable aperture 41 and the fourth variable aperture 44, the second variable aperture 42 and the third variable aperture
The variable apertures 43 each change with the same aperture area depending on the steering operation.

In addition, 6 in the figure is a power cylinder, and two hydraulic chambers 5a and 5 are formed in the cylinder tube 7 by a piston 9 integrated with a piston rod 8 passing through the cylinder tube 7.
b is defined. Further, left and right wheels (shown in the figure) are individually connected to both ends of the piston rod 8. The first hydraulic pressure chamber 6a of the power cylinder 6 is connected between the circuits connecting the first variable throttle 41 and the second variable throttle 42, and the second hydraulic pressure chamber 6b is connected to the circuit connecting the first variable throttle 41 and the second variable throttle 42. Aperture 43
and the fourth variable diaphragm 44.

Therefore, when the steering wheel is held in the neutral position and the vehicle is traveling straight, the aperture areas of the first variable aperture 41 and the third variable aperture 43 of the control pulp 4 and the second variable aperture are 942 and the fourth variable aperture 44
The aperture areas of each are equal. For example, by rotating the steering wheel to the right from this state, the control pulp 4 is actuated via a torsion bar (not shown -r) that is twisted in response to the steering operation, and the first variable throttle 41 If the opening degrees of the second variable diaphragm 42 and the third variable diaphragm 43 are narrowed while widening the opening degrees of the fourth variable diaphragm 44, the first variable diaphragm becomes larger than the third variable diaphragm 43. 41, a large amount of hydraulic fluid flows, and this is supplied to the first hydraulic chamber 6a of the power cylinder 6, causing the piston rod 8, which is integrated with the piston 9, to move to the left in the figure, and the hydraulic fluid corresponding to the amount of supplied fluid is supplied. is discharged from the 20th hydraulic pressure chamber 6b, and this is the fourth variable throttle 4.
4, is returned to the reservoir tank 2 via a return circuit 5. As a result, the left and right wheels connected to both ends of the piston rod 8 are steered in the same direction as the rotation direction of the steering wheel, and power assist for steering operation is performed through the operation of the power cylinder 6. It will be done.

Now, if you release the steering wheel's holding power,
The self-lining torque of the tire is the power cylinder 6.
At the same time, the spring force of a torsion bar (not shown) acts to restore the control pulp 4 to the neutral position, thereby canceling the power assist. From this, the steering is automatically restored to the neutral position based on the self-lining torque, and as a result, the vehicle changes to a straight running state.

However, in such a conventional power steering device, there are four variable throttles 41, 42 with relatively narrow throttle areas between the power cylinder 6 and the hydraulic pump.
A control pulp 4 consisting of 43.44 is interposed,
While additionally supplying hydraulic fluid to one hydraulic pressure chamber (ia (or 6b)) of the power cylinder 6 through these variable throttles 41, 42, 43, 44, hydraulic fluid corresponding to this supplied fluid amount is transferred to the other hydraulic chamber. By discharging the pressure chamber 6b (or fia), the power cylinder 6 is driven 5, thereby power assisting the steering operation.For this reason, when returning to the neutral position, the return circuit of the control pulp 4 is activated. The throttling resistance caused by the variable throttles 42 and 44 on the 5 side and the frictional resistance generated in the sliding parts of various seal members provided on the power cylinder 6 and the control pulp 4 are the resistance when the piston 9 of the power cylinder 6 moves. Due to these resistance forces, the restorability of the steering, especially when driving at low speeds, was not as good as that of general manual steering devices.

[Purpose of the invention]

This invention was made by focusing on the insufficient restoring force to the neutral position in such conventional power steering devices, and when the steering and holding force of the steering wheel is released, the power cylinder Self-centering system that forcibly supplies working fluid to the fluid chamber on the side from which working fluid is discharged during steering, uses the fluid pressure to restore the power cylinder to the neutral position, and automatically restores the steering to the neutral position. The purpose is to provide a mechanism.

[Structure of the invention]

Accordingly, the present invention supplies the working fluid discharged from the fluid pressure pump to the power cylinder having two fluid chambers via the control pulp that responds to the steering operation, and returns it to the fluid pressure pump. supplying the working fluid to one fluid pressure chamber of the power cylinder through actuation of the control pulp;
In a power steering device that performs power assist by discharging a part of the working fluid from the other fluid pressure chamber to drive a power cylinder, a flow rate of the working fluid is provided between the fluid pressure pump and the control pulp. The upstream side of the flow rate control means is branched, and the branch path is provided with a direction switching means for switching the flow direction of the working fluid, and the downstream side of the direction switching means is set to The two fluid pressure chambers of the cylinder are individually connected to the suction side of the fluid pressure pump, and the flow of working fluid from the power cylinder to the control pulse is connected between both fluid chambers and the control pulp. In addition, a steering force detection means generates a detection output according to the magnitude of the steering force during steering operation, and a steering angle detection means generates a detection output according to the magnitude of the steering angle. and a control device for controlling the aperture opening of the flow rate control means and the switching operation of the direction switching means in accordance with an output signal from the rain detection means. Related to centering mechanism.

〔Example〕

The present invention will be explained below based on the drawings. .

FIGS. 2 to 9 are diagrams showing an embodiment of the present invention.

First, to explain the configuration, reference numeral 1 shown in FIG. 2 is a hydraulic pump that is a specific example of a fluid pressure pump. It is inserted into the hydraulic fluid as a specific example, and
A supply circuit 3 is connected to the discharge port. The hydraulic pump 1 is rotationally driven by an engine (not shown) to suck the hydraulic fluid in the reservoir tank 2, and discharges the hydraulic fluid into the supply circuit 3 at a high pressure. The supply circuit 3 includes a two-bottom, two-position switching valve 10, which is a specific example of flow rate control means.
is connected to a control pulp 4 that responds to steering operations. This 2 point 2 position switching valve 10
is a single-lenoid spring offset type electromagnetic switching valve having a solenoid 5OL3 and a spring S3, and its non-operating position 10a and operating position 10b.
Both are in communication, but a restriction is provided in the passage at the operating position 10b.

The control pulp 4 has four variable throttles 41°42.
43.44, and these four variable apertures 41,
42, 43, and 44, the first variable diaphragm 41 and the second variable diaphragm 42 are connected in series, and the third variable diaphragm 43 and the fourth variable diaphragm 44 are connected in series. The sets of apertures connected to each other are connected in parallel to each other. Furthermore, a first variable aperture 41 and a fourth variable aperture 44,
The second variable diaphragm 42 and the third variable diaphragm 43 change with the same diaphragm area depending on the steering operation, but the opening/closing direction is different from that of the first and fourth variable diaphragms 41 .
The second and third variable apertures 42, 43 are formed to operate in opposite directions relative to 44. Therefore, for example, when the aperture areas of the first and fourth variable apertures 41.44 increase, the aperture areas of the second and third variable apertures 42.43 decrease. In addition, four variable apertures 41, 42, 43
．． Reference numeral 44 is formed so that when the control valve 4 is located at the neutral position, which is a state in which the vehicle is traveling straight, the throttle opening degrees thereof are the same.

Further, 6 in the figure is a power cylinder, and this power cylinder 6 includes a cylinder tube 7, a piston rod 8 that passes through a hole in the cylinder tube T, and a piston rod 8 that is loosely fitted in the hole in the cylinder tube 7 and connected to the piston rod 8. The piston 9 is integrally provided, and the piston 9 divides the cylinder tube 7 into two hydraulic pressure chambers 6a and 6b. Both hydraulic chambers 6a and 5b constitute a specific example of two hydraulic chambers of the power cylinder 6. Bar r7-
Left and right wheels (shown in the figure) are individually connected to both ends of the piston rod 8 of the cylinder 6 via tie rods (not shown) or the like.

The first hydraulic chamber 6a of the power cylinder 6 has a check valve 11 between the circuits connecting the first variable throttle 41 and the second variable throttle 42.
The second hydraulic chamber 6b is connected to the circuit connecting the third variable throttle 43 and the fourth variable throttle 44 via a valve 12. These two reverse IL valves 11, 12i, ]: stop the flow of hydraulic fluid from each hydraulic pressure chamber 6a, 6b of the power cylinder 6 toward the control valve 4, and from the control valve 4 to each hydraulic pressure chamber 5a, 6b. Install it so that it only allows the flow of hydraulic fluid towards. The downstream side of the control valve 4 is connected to the reservoir tank 2 via a return circuit 5.

The supply circuit 3 is branched on the upstream side of the two-point/two-position switching valve 10, and within this branch path 3a is a directional switch 4, which is a specific example of a direction switching means for switching the flow direction of the hydraulic fluid. A port 3 vertical switching valve 13 is provided, and the hydraulic pump 1 side of the supply circuit 3 is connected to the P port. And 4
The A port of the three-position switching valve 13 is commonly connected to the power cylinder 6 side of the check valve 12 and connected to the 20th hydraulic chamber 6b of the power cylinder 6, and the B port is connected to the check valve 11 side. The T port is connected to the first hydraulic chamber 6a of the power cylinder 6 in common with the power cylinder 6 side, and the T port is further connected to the reservoir tank 2 via the return circuit 5. The 4-point/3-position switching valve 13 includes two solenoids 80L1.5OL2 and two springs s1. s
2, and its neutral position 13a is an open center.

The switching operation of the 4-point, 3-position switching valve 13 and the switching operation of the 2-point, 2-position switching valve 10 are controlled by a control signal output from the control device 15. The control device 15 is composed of a processing device such as a microcomputer, and includes a process input/output device 16, an arithmetic processing device 17, and a storage device 18. The process input/output device 16 includes a steering force detector 2, which is an example of a steering force detection means.
0 and a detection signal from a steering angle detector 21, which is an example of a steering angle detection means, are respectively input as analog voltage values, and two steering force setters 22a,
The reference value signal from the steering angle setter 22b and the reference value signal from the steering angle setter 23 are each input as predetermined voltage values set in advance.

The process input/output device 16 has an A/l) converter, converts each input signal into a digital value, and sequentially sends the digital value to the arithmetic processing device 17. The arithmetic processing unit 17 has a storage device 18
The voltage signal from the steering force detector 20 and the steering force setters 22a, 22 are operated according to a program stored in advance in the
In addition to comparing the voltage signal from the steering angle detector 2 with the voltage signal from the
The voltage signal from 1 and the voltage signal from the steering angle setter 23 are compared to determine whether the steering force is within a predetermined range and greater than a predetermined value, and whether the steering angle is zero. If the angle is zero, it is determined whether the angle is larger than a predetermined angle.

Then, the arithmetic processing unit 17 transmits an excitation current, which is a control signal SC for exciting the three solenoids 5OL1, 5OL2, and 5OL3, to the process input/output device 16 and each solenoid drive circuit 30 based on the result of the determination.
Each solenoid 5QL1.8 via a, 30b, 30C
Send separately to 0L2.5OL3.

As the steering force detector 20, for example, one having a configuration as shown in FIG. 4 can be adopted. This steering force detector 20 (ri) connects the steering shaft 25 to the input shaft 25.
a and output shaft 25b, and both shafts 25a,
25bj are connected via a torsion bar 26, and coaxially therewith are provided first and second planetary gear sets 27 and 28, and the three elements of the first planetary gear set 27 are a sun gear, a pinion carrier, and a ring gear. one of the elements is fixed to the vehicle body side, and one of the remaining two elements is connected to one of the input shaft 25a or the output shaft 25b,
and while leaving the other element free to rotate, any one of the three elements of the second planetary gear set is made free to rotate and connected to the free rotation element of the first planetary gear set; One of the remaining two elements is connected to the input shaft 25a.
Alternatively, the output shaft 25b is connected to the other element, and the other element is freely rotatable, and this element is provided with a rotation angle detection means 29 using a potentiometer or the like for detecting the rotation angle. . Then, the torsion angle between the input shaft 25a and the output shaft 25b is set to the first and second planetary gear set 2.
7. At the same time as amplifying it by 28, it is detected by the rotation angle detection means 29, and the detected value is converted into a predetermined analog signal according to the magnitude of the steering force and the steering direction, as shown in FIG. 5, for example. Then, it is sent to the process input/output device 16 of the control device 15.

That is, this steering force detector 20 outputs the reference voltage VO when the steering force T is zero, and also sets a neutral area To when the steering force T is within a predetermined value regardless of whether the steering direction is left or right. , steering wheel 24
When the vehicle is turned to the right side with a torque greater than a predetermined steering force T□, a voltage V (V≧VR
... VR is a voltage corresponding to the steering force TR), and the steering wheel 24 is moved to the left by a predetermined steering force T.
When turning with a torque greater than I, a voltage V corresponding to the left steering force TL (V≦VL...VI, is a voltage corresponding to the steering force TL) is output. Therefore, the neutral zone T.

Then, VR>V>VI.

The steering angle detector 21 has a relationship with the above-mentioned steering direction,
A sixth wheel responsive to the rotational position of the steering wheel 24.
When the steering wheel 24 is in a neutral position when the vehicle is running straight, that is, when the steering angle θ is zero (neutral point), θm is composed of a potentiometer as shown in the figure.
The reference voltage v6m is outputted as shown in FIG. As shown in the figure, for example, when the steering wheel 24 is turned to the right of the neutral point, the output voltage V increases, while when the steering wheel 24 is turned to the left of the neutral point, the output voltage V decreases. . As a result, when the detection signal V of the steering angle detector 21 is equal to the reference voltage v6m, the vehicle is running straight, and when the detection signal V is higher than the reference voltage V#□, the steering wheel is in the right steering position. When the detection signal is lower than the reference voltage v6m, it can be determined that the steering wheel is in the left steering position.

The two steering force setters 22a and 22b are configured with, for example, a variable voltage source, and the first steering force setter 22a sets an arbitrary steering force setting value TFL represented by the right side steering force T.
Further, the second steering force setter 22b outputs a voltage signal corresponding to an arbitrary steering force setting value TL represented by the left steering force TL. Then, each steering force setting value TFL, TL of the two steering force setting devices 22a, 22b is input to the process input/output device 16.
The arithmetic processing unit 17 reads the data through the T1. The difference between T, that is, the steering force T
The area value corresponding to the neutral area To is stored in the storage device 18.

The steering angle setter 23 is constituted by, for example, a variable voltage source, and is configured to output a voltage signal corresponding to a steering angle setting value θm at a neutral position in which no steering is performed, represented by θ□.

The control device 15 receives voltage output signals from the above-mentioned steering force detector 20, steering angle detector 21, steering force setters 22a, 22b, and steering angle setter 23, and operates based on these input signals. Said 4-point and 3-position switching valve 13
The excitation current, which is the control signal SC, is output to the two solenoids 5OL1 and 5OL2 and the solenoid 80L3 of the two-point/two-position switching valve 10, and each solenoid 5OLI, 5OL2゜5OL3 is individually operated as shown in Fig. 8. Or by selectively combining and driving with excitation,
Drive control of both switching valves 10.13.

FIG. 9 is a flowchart for executing the program of the control device 15. When the calculation process starts,
First, in step 1, the detected value T of the steering force detector 20 is read and stored in a predetermined area of the storage device 18. Next, in step 2, the steering force detection value T falls within the neutral area T of the steering force.
Determine whether it is in o. Then, when the detected steering force T is not in the neutral zone To, that is, when the steering force T is zero or within a predetermined value (TR>T>TL), the process moves to step 3 and the steering angle detector 21 The detected value θ is read and stored in a predetermined area of the storage device 1B.

Next, in step 4, the detected steering angle value θ is set to the reference angle θ□
(the steering angle θ is zero), and if the detected steering angle θ is not equal to the reference angle θ□, the process moves to step 5. In step 5, the detected steering angle θ is set to the reference angle θ□
Determine whether the value is greater than or not. This is because, as described above, the steering angle setter 23 sets the reference angle (steering angle setting value) Om.
On the other hand, when the steering angle detector 21 is in the right steering position, the steering angle detector 21 outputs a voltage larger than the voltage signal V corresponding to the reference angle θ□ according to the steering angle θ. A signal V□ is output, and conversely, when the steering position is on the left side, a voltage signal V that is smaller than the voltage signal Vθ corresponding to the reference angle θ is generated depending on the steering angle θ.
In order to output L (Fig. 5), it is determined whether the voltage signal V corresponding to the detected steering angle θ is larger than the voltage signal V corresponding to the reference angle θ□. You can determine whether it is facing towards you or towards the left.

Therefore, when the detected steering angle θ is not larger than the reference angle width, that is, when the steered wheels are facing to the left, the process moves to step 6 and the solenoid 5OL2 is turned OFF.
``At the same time, move on to step 7.''

Turn on solenoid sor, 1, then move to step 8 and turn on solenoid 5OL3.
" do.

As a result, the 4-point and 3-position switching valve 13 is moved to the left position 13b.
The working fluid from the hydraulic pump 1 is switched to the first position of the power cylinder 6 via this 4-point/3-position switching valve 13.
At the same time, the two-bottom, two-position switching valve 10 is switched to the steering position 10b to narrow the circuit.

As a result, the power cylinder 6 is returned to the left side in FIG.
Centering is performed in this way.

On the other hand, in step 5, the detected steering angle θ is changed to the reference angle θ
□ If it is larger, that is, the steering wheel is facing to the right, proceed to step 9 and turn on solenoid 80L.
At the same time, the program proceeds to step 10 and turns on the solenoid 80L2, and then proceeds to step 8 to turn on the solenoid 5OL3.

As a result, the 4-point and 3-position switching valve 13 is moved to the right position 13C.
The working fluid from the hydraulic pump 1 is switched to the second position of the power cylinder 6 via this four-bottom, three-position switching valve 13.
At the same time, the two-bottom, two-position switching valve 10 is switched to the operating position 10b to narrow the circuit. As a result, the power cylinder 6 is returned to the right side in FIG. 2, and centering is performed in this manner.

Further, in step 4, if the detected steering angle θ is equal to the reference angle θ□, that is, when the vehicle is in a straight-ahead running state, the vehicle is already centered, so the process moves to step 11 and the solenoid 5OL3 is turned off. "At the same time, the process moves to step 12 and the solenoid 5OL2
Then, in step 13, the solenoid 80L1 is turned off. As a result, the 4-point, 3-position switching valve 13 is held at the neutral position 13a, and the 2-point, 2-position switching valve 10 is held at the non-operating position 10a, and the centered state is maintained.

Further, in step 2, the detected steering force T is a neutral area T of the steering force. If not, that is, the predetermined value TFL or TL
When steering to the right or to the left with the above steering force T, proceed to step 21 and turn on solenoid 5OL3.
Then, in step 22, it is determined whether the detected steering force T is larger than the set steering force TR during right-hand steering using the method previously shown in FIGS. 4 and 5.

Therefore, if the detected steering force T is not larger than the right side steering force set value T1, that is, if the steering is to the left, the process moves to step 23 and the solenoid 5OL1 is turned off.
'OFF' L, and then proceed to step 24 to turn on the solenoid 5OL2. This results in 2 points and 2 points.
While the position switching valve 10 is held at the non-operating position 1°a,
The 4-point/3-position switching valve 13 is switched to the right position 13C, and the power cylinder 6 is pushed to the right in FIG. 2 in the same manner as described above, thereby performing power assist to the right.

On the other hand, in step 22, if the detected steering force T is larger than the set steering force TR when steering to the right, that is, if the steering is to the right, the process proceeds to step 25, where the solenoid 5OL2 is turned off, and further, step 26 Then, the solenoid 80L1 is turned on. As a result, the 2-point, 2-position switching valve 10 is held in the non-operating position, while the 4-point, 3-position switching valve 13 is switched to the left position 13b, and the power cylinder 6 is pushed to the left in FIG. power assist to the left side.

Next, the effect will be explained.

First, each setting value TRI of the steering force setting device 22a, 22b
TL (TR>TL) is set to a desired value, thereby determining the neutral region To of the steering force, and the set value θ□ of the steering angle setter 23 is set to zero. Then, when the arithmetic processing unit 17 is started and the processing is started as described above based on the flowchart of FIG. 9, the steering force T of the steering wheel 24 reaches the neutral area T. If the steering angle θ is equal to the set value θ□ and is zero, that is, when the vehicle is traveling straight and no steering force T greater than the predetermined value is acting, steps 1 to 4 are performed. After that, the process proceeds to steps 11 to 13, and all three solenoids 80L1.5OL2.5QL3 are turned OFF.
to the non-operating position 10a.
and the 4-point to 3-position switching valve 13 to the neutral position 13.
hold at a. In this state, the steering wheel is already centered, so self-centering is not performed.

Further, if the steering force T is within the neutral zone To, but the steering angle θ is larger than the steering angle setting value θm, that is,
When the steering force T is less than the predetermined value TR, but the steering wheel is in a position where the steering wheel is turned to the right, steps 1 to 5 are performed.
Step 9. The process proceeds to step 10 and step 8, and the solenoid 5OL1 is turned off, while the two solenoids 80L2 and 5OL3 are both turned off.
ON” and set the 2-point to 2-position switching valve 10 to operation position 1.
Control is performed to switch the 3-position switching valve 13 to the right position 13c. This results in
Of the working fluid from the hydraulic pump 1, the hydraulic pressure supplied to the two hydraulic chambers 5a and 5b of the power cylinder taro via the 2-bot 2-position switching valve 10 and the control pulp 4 is 2-bot. The control pulp 4 is throttled by the two-position switching valve 10 to reduce the influence of the difference in the opening degree of each variable throttle 41, 42, 43° 44, and the second Since hydraulic pressure is supplied to the hydraulic pressure chamber 6b, the power cylinder 6 moves to the left in FIG. 2 and returns to the neutral position, thus performing self-centering to the right.

Furthermore, although the steering force T is within the neutral zone To,
If the steering angle θ is not larger than the set steering angle θ□, that is, if the steering force T is less than or equal to the set steering force TL but the vehicle is in a position where it is steered to the left, the process proceeds to steps 1 to 8, Turn off solenoid 5OL2, while turning on both solenoids 5QL1.5OL3.
” 2-point 2-position switching valve.

10 to the operating position 10b and the 4-point/3-position switching valve 13 to the left position 13b.

As a result, the first hydraulic pressure chamber 6 of the power cylinder 6 is opened via the 4-point/3-position switching valve 13, contrary to the case of right-hand steering.
Since the working fluid of the hydraulic pump 1 is supplied to the point a, the power cylinder 6 moves to the left in FIG. 2 and returns to the neutral position, thus performing self-centering to the left.

On the other hand, the steering wheel 24 is set to a steering force TI5.
When steering to the left with the above force (d1), of the four variable apertures 41, 42, 43, and 44, 41°44 is narrowed and 42.43 is widened.

After cutting, step 1 and step 2, step 21-2
The process proceeding to step 6 appears, and the two solenoids 5OL1.
While turning both 5OL3 "OFF", solenoid 8
Turn 0L2 ON and return the 2-point 2-position switching valve 10 to the non-operating position 10a.
3 to the right position 13C. As a result, the passage of the 2-point/2-position switching valve 100 is maintained in a normal state, and the four variable throttles 41, 4 of the control pulp 4 are
2, 43, and 44, the working fluid of the hydraulic pump 1 is further supplied to the second hydraulic chamber 6b of the power cylinder 6 via the 4-point/3-position switching valve 13. is supplied, the power cylinder 6 moves to the right in FIG. 2, and normal power assist for leftward steering is performed.

Further, when the steering wheel 24 is being steered to the right with a force greater than or equal to the set steering force TR, 42 degrees 43 of the four variable apertures 41, 42, 43, and 44 are narrowed down, and 41.44 of the variable apertures are widened.

Further, the process of proceeding to step 25 and 26 via step 1, step 2, step 21, and step 22 is performed,
Turn off both solenoids 5OL2 and 5OL3.
Meanwhile, turn on solenoid soI, 1,
The 2-point 2-position switching valve 10 is in the non-operating position F(t, 10
Return to position a and move the 4-boat 3-switch valve 13 to the left position 131.
) is controlled. As a result, the passage of the two-point/two-position switching valve 10 is maintained in a normal state, and the four variable throttles of the control valve 4 are
While increasing the influence of the difference in the opening degree of the power cylinder 6, the
Since the hydraulic fluid for the hydraulic pump 1 is supplied to the hydraulic chamber 6aK, the power cylinder 6 moves to the left in FIG. 2, and normal power assist for rightward steering is performed.

Note that the neutral rW position 13a of the 4-point/3-position switching valve 13 is of the center-open type, so when the vehicle is traveling straight, most of the flow discharged from the hydraulic pump 1 flows through the switching valve 1.
3 and is directly returned to the reservoir tank 2, the discharge pressure of the hydraulic pump 1 can be reduced, and fuel efficiency can be improved accordingly.

A second embodiment of the invention is shown in FIGS. 10 to 16.

In this embodiment, the self-centering speed is continuously controlled steplessly in accordance with the vehicle speed V and the steering angle θ of the steering wheel. Therefore, a vehicle speed detector 31 that detects the vehicle speed and outputs a signal thereof, and a vehicle speed setter 32 that outputs a signal corresponding to a predetermined vehicle speed setting value are provided, and the respective signals are input to the control device 15.

The vehicle speed detector 31 is, for example, a propeller shaft (path in the figure).
This rotation detector outputs a pulse signal with a frequency corresponding to the rotation speed of the propeller shaft, which is converted by a frequency-voltage converter into a voltage output corresponding to the rotation speed. I'll do what I do.

Further, the vehicle speed setter 32 is constituted by, for example, a variable voltage source, and is configured to output a voltage signal corresponding to an arbitrary vehicle speed setting value v5 represented by v5.

Further, in this embodiment, as shown in FIG. 10, in order to perform the self-centering speed steplessly, a variable throttle valve 33 with two points and two positions is used as a specific example of the flow rate control means.
is used. This 2-port 2-position variable throttle valve 33 is
This is a single solenoid spring offset type electromagnetic throttle valve having a solenoid 5OL4 and a spring 84, and its throttle area changes steplessly and continuously according to the magnitude of the drive current applied to the solenoid 5OL4. , when the solenoid 5OL4 is "OFF", the aperture area is maximized, and when the excitation current is maximum, the circuit is closed. Fig. 11 shows the current (1) applied to the solenoid 5OL4 and the current It is a graph diagram showing the relationship between the opening degree of the variable diaphragm that is opened and closed by the operation of the solenoid 5OL4, and the variable diaphragm can be controlled to an arbitrary opening degree by adjusting the magnitude of the applied current.

The drive current value of the solenoid 5OL4 in the 2-port 2-position variable throttle valve 33 is determined, for example, based on a determination procedure shown in a block diagram as shown in FIG. That is, first, the magnitude of the assist hydraulic pressure P required to return the steering wheel to the neutral position is determined from the vehicle speed V and the steering angle θ. This is because, as shown in FIG. 13, there is a certain relationship between the steering angle θ and the assist hydraulic pressure P depending on the vehicle speed V, so the necessary assist hydraulic pressure P can be easily calculated. be able to. In the same figure, the solid line a shows a characteristic graph of assist hydraulic pressure P vs. steering angle θ when stationary (vehicle speed v-0), and the broken line shows a similar characteristic graph at a certain vehicle speed (vehicle speed v>0). shows.

Furthermore, the target value of the steering return speed (π) is determined based on the vehicle speed V and the steering angle θ. This is the first
As shown in Figure 4, the absolute value 1θ1 of vehicle speed V and steering angle θ
The vehicle speed v(vl, v2.v,...
- The target value of the steering return speed (π) increases according to the reference vehicle speed, '/1<V2<V3). Therefore, by looking at the vehicle speed V and the steering angle 1θI, the target steering return speed (π) under the driving conditions can be determined. In addition, this figure shows the relationship between the steering return speed (-27) and the steering angle Iθ1, where the solid line C is v (when V work, the solid line d is v
When l<v<v2, the solid line e(dv2 x v<■) is a characteristic graph, respectively.

Next, based on the above-mentioned assist hydraulic pressure P and steering return speed (π), the 2-port 2-position variable throttle valve 33
Determine the aperture opening. FIG. 15 is a graph showing the relationship between the assist hydraulic pressure P and the steering return speed 0 (revised) when the throttle opening of the variable throttle valve 33 is used as a parameter. In order to obtain this, the assist hydraulic pressure P is small when the throttle opening of the variable throttle valve 33 is large, as shown by the solid line f, and the assist hydraulic pressure P is small when the throttle opening is small, as shown by the solid line g. A large amount of P is required.

Therefore, it is possible to determine the throttle opening degree of the variable throttle valve 33 that achieves the amount of force required to return the steering wheel to the neutral position. In addition, in the figure, a solid line parallel to the steering return speed (π) indicates the relief pressure of the variable throttle valve 33.

In this embodiment, the arithmetic processing unit 17 of the control device 15 in FIG. 3 is operated according to the flowchart shown in FIG. 16. That is, in FIG. 16, between step 4 and step 5 in FIG. 9, there is a step 41 in which the detected mv of the vehicle speed detector 31 is read and stored in a predetermined area of the storage device 1B, and the detected vehicle speed is A step 42 for determining whether V is faster than the set vehicle speed V5 from the vehicle speed setter 32 is interposed, and when it is determined in Step 42 that the detected vehicle speed V is faster than the set vehicle speed V, It is configured to proceed to step 11A.

Along with changing the 2-point 2-position switching valve 10 to the 2-port 2-position variable throttle valve 33, the solenoid 5O
Since L3 is the solenoid 5OL4, steps 8, 11 and 21 in FIG. 9 are respectively replaced by steps 8A.

Step IIA and Step 21. The structure is exactly the same as that shown in the same figure except that it is changed to A.

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

The steering force T of the steering wheel 24 is in the neutral area To
, and if the steering angle θ is equal to the set value θm and is zero and the detected vehicle speed is not greater than the set vehicle speed v5, that is, the vehicle is traveling straight and the set steering force TR is
When the steering force T greater than (or TL) is not acting and the vehicle speed V is less than the set vehicle speed v8, the process moves to step 5. Perform centering control. Then, the throttle opening of the 2-port 2-position variable throttle valve 33 is set to a predetermined value using the drive current value obtained as described above from the vehicle speed V and the steering angle θ, and the vehicle speed V and the steering angle θ are The self-centering speed is controlled accordingly.

On the other hand, in step 42, the detected vehicle speed V is changed to the set vehicle speed V.
If the speed is faster than that, there is no need to perform self-centering using the assist hydraulic pressure of the power cylinder 6, and only the steering restoring force that a normal vehicle originally provides is sufficient, so the process proceeds to step 11A1 step 12 and step 13. In addition, the 4-point and 3-position switching valve 1
Control is carried out to hold 3 at the neutral position tiaa, and self-centering is not carried out.

Thus, in this embodiment, when the vehicle speed is below the arbitrary set value Vs, it is possible to set the steering return speed (π) to a desired value as a target value according to the driving conditions at that time, and also to set it to a desired value. This allows the steering to self-center at an ideal return speed. Moreover, since vehicle speed is a powerful means of understanding driving conditions, by using vehicle speed as a condition signal for self-centering, it is possible to further improve steering stability, and the self-centering function is activated above a certain vehicle speed. By making the configuration impossible, the solenoid 5QL1.
At the same time, a fail-safe function against malfunction of the 80L2.5OL4 can be achieved.

FIG. 17 shows a third embodiment of the invention.

In this embodiment, a center-closed type double solenoid spring center electromagnetic switching valve is used as a 4-point, 3-position switching valve 34, which is a specific example of a direction switching means. This is similar to the first embodiment shown in FIG. In this embodiment, when the vehicle is traveling straight, the 4-point/3-position switching valve 34 is in the neutral position with all four boats closed, so both hydraulic chambers 5a and 5b of the power cylinder 6 are sealed. This makes it easier to maintain a straight line. Therefore, it is possible to perform optimal self-centering control according to the driving situation, and at the same time, it is possible to significantly improve straight-line stability during high-speed driving.

Figure 18 shows solenoids 5OL1, 5OL2, 5OL3
(or 5OL4) is a chart showing the phenomenon when it malfunctions. Numbers 1 to 6 in the vertical column of this diagram indicate the "ON" and OFF" combinations of the three solenoids 5OL1 to 3, and the horizontal column indicates the steering status.As is clear from this diagram, There are two types of malfunctions:

(1) A situation in which hydraulic pressure assist does not occur or an equivalent condition; (11) A situation in which the solenoid on the opposite side to the intended one operates or the steering turns off automatically; (1)
In this case, the steering force of the steering wheel is only slightly heavier than the steering force of the manual/l/steering wheel due to the difference in the overall gear ratio, and there is no problem since the steering becomes impossible. However, in the case of Qi), it greatly influences the steering performance, and in particular, the higher the vehicle speed, the greater the influence becomes.

Therefore, an embodiment that takes measures against the above case (II) will be described below. Conditions that cause a serious effect like the case in (11) are: (a) When solenoid 5OL3 (or 5OL4) is
ON'-.

Time (b) Solenoid 5OLl and solenoid 5QL2
A problem occurs only when the two conditions for operating in reverse are met at the same time (numbers 4 and 6 in the diagram).

Therefore, when it is determined that there is an abnormality, solenoid 8
By turning only 0L3 (or 5OL4) OFF, or by turning OFF all solenoids 5QL1 to 5QL3 (or 5OL4), a failsafe against malfunction of the solenoids 5QL1 to 5OL4 can be achieved.Especially , as shown in Figure 16,
When the vehicle speed V is equal to or higher than the set vehicle speed v5, all the solenoids 5OL1 to 5OL4 are turned OFF without fail, thereby reducing the risk of malfunction.

Further, FIG. 19 shows a flowchart of a fourth embodiment of the present invention.

In this embodiment, the control device 15 in FIG.
The arithmetic processing unit 17 is operated according to the flowchart shown in FIG. That is, in FIG. 19, after step 8A in FIG. 16, it is determined whether the absolute value 1θ-0m1□ of the steering angle θ read this time is also larger than the absolute value 1θ-θmio of the steering angle θ read last time. Step 81 of determining 10-0m1□〉1θ-
When θmIO, it is assumed that there is an abnormality and all the solenoids 5OL1.5OL2.5OL4 are turned off (step 82), and step 83 is provided to turn on an abnormality lamp to warn of the abnormality. This is the solenoid 5OL of the 2-port 2-position variable throttle valve 33.
When solenoid 4 is "ON", it is only when self-centering is performed, so this solenoid 5OL4
is ON” and the operation is normal, the steering angle θ must be
is obtained from the premise that must be close to the central position θ□. Therefore, in this case, the solenoid 5OL4 and the other solenoids 5OL1 and 5OL2 are all turned OFF'' and the power cylinder 6
By disabling the power assist, these serious malfunctions can be quickly prevented. In this way, the read value of steering angle θ is adjusted to the center position θ
By monitoring 1θ-θml to see how far it is from □ and comparing it with the previous data,
Each solenoid 80L1.5 when self-centering is activated.
Since it is possible to determine whether the operation of OL2.5OL4 is normal or abnormal, these serious malfunctions can be instantly prevented. Moreover, the abnormality can be notified to the driver by lighting an abnormality lamp or the like.

〔Effect of the invention〕

As described above, in this invention, a flow rate control means for adjusting the flow rate of the working fluid is provided between the fluid pressure pump and the control pulp, and the upstream side of the flow rate control means is branched to the branch path. , a direction switching means for switching the flow direction of the working fluid is provided, and the downstream side of this direction switching means is individually connected to the two fluid pressure chambers of the power cylinder and the suction side of the fluid pressure pump, and Check valves are installed between the pressure chamber and the control pulp to stop the flow of working fluid from the power cylinder to the control pulp, and also generate a detection output according to the magnitude of the steering force during steering operation. a steering force detection means;
a steering angle detection means for generating a detection output according to the magnitude of the steering angle, and a flow rate control means according to an output signal from the rain detection means.

The configuration is such that a control device is provided to control the opening of the throttle and the switching operation of the direction switching means. For this reason, when the steering force and steering force of the steering wheel are released, working fluid is forcibly supplied to the fluid pressure chamber of the power cylinder on the side from which working fluid is discharged during steering, and the fluid pressure The power cylinder can be automatically restored to the neutral position. Therefore, the stability of the steering wheel at low speeds can be significantly improved, and even when the vehicle is stationary, the steering wheel is automatically restored to the neutral position simply by releasing the steering wheel, improving driving operability. The effect is that it can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing a conventional power steering device, FIG. 2 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 3 is a block diagram showing an example of a control device. 4 is an explanatory diagram showing an example of the steering force detection means, FIG. 5 is a characteristic diagram of the signal output from the steering force detection means of FIG. 4,
6 is an explanatory diagram showing an example of the steering angle detecting means, FIG. 7 is a characteristic diagram of the signal output from the steering angle detecting means of FIG. 4, and FIG. 8 is an explanatory diagram showing an example of the operation of the steering angle detecting means of FIG. 9 is a flowchart for explaining the operation of the control device in FIG. 3, and FIG. 10 is a hydraulic circuit diagram showing a second embodiment of the present invention. Figure 11 is a graph showing the relationship between the throttle opening and applied current of the variable throttle valve in Figure 10, Figure 12 is an explanatory diagram of the process for determining the driving current value of the solenoid, and Figure 13 is a graph showing the relationship between the throttle opening and applied current of the variable throttle valve in Figure 10. ,
Fig. 10 is a graph showing assist hydraulic pressure and steering angle in relation to vehicle speed to explain the operation, and Fig. 14 is a graph showing steering return speed and steering angle during self-centering in relation to vehicle speed. A graph diagram, FIG. 15 is a graph diagram showing the relationship between assist hydraulic pressure and steering return speed in relation to throttle opening, and FIG. 16 is a flowchart for explaining the operation of the control device in FIG. Figure 18 is a hydraulic circuit diagram showing a third embodiment of the invention, Figure 18 is a chart showing solenoid malfunctions and their phenomena, and Figure 19 is a control diagram according to a fourth embodiment of the invention. 3 is a flowchart illustrating the operation of the device. 1... Hydraulic pressure pump (fluid pressure pump), 4... Control pulp, 41, 42, 43.44... Variable throttle, 6... Power cylinder, 6a, 6b... Hydraulic pressure chamber (
10... 2-point 2-position switching valve (flow control means), 11.12... Check valve, 13.34...
4-bottom 3-position switching valve (direction switching means), 15...control device, 20...steering force detector (steering force detection means),
21... Steering angle detector, (steering angle detection means), 22a
, 22b... Steering force setting device, 23... Steering angle setting device, 31... Vehicle speed detector, 32... Vehicle speed setting device, 33
...2-port 2-position variable throttle valve (flow control means),
80L1゜5OL2.5OL3.5OL4... Solenoid patent applicant Nissan Motor Co., Ltd. agent Patent attorney Tetsuya Mori Patent attorney
Yoshiaki Naito, patent attorney, Shimizu, patent attorney, Haku Yamaki, 43- Figure 4, 26, 77@press

Claims (1)

[Claims] The working fluid discharged from the fluid pressure pump is supplied to the power cylinder having two fluid pressure chambers through a control valve that responds to steering operation, and is returned to the fluid pressure pump. In a power steering device that performs power assist by supplying the working fluid to one fluid chamber of the power cylinder through operation and discharging a part of the fluid pressure from the other fluid chamber to drive the power cylinder, A flow rate control means for regulating the flow rate of the working fluid is provided between the fluid pressure pump and the control valve, and an upstream side of the flow rate control means is branched to direct the flow direction of the working fluid to this branch path. A direction switching means for switching is provided, and the downstream side of the direction switching means is connected to the two =1-
A check valve is connected individually to the fluid pressure chamber and the suction side of the fluid pressure pump, and is located between both fluid chambers and the control valve to stop the flow of working fluid from the power cylinder to the control valve. and a steering force detection means for generating a detection output according to the magnitude of the steering force during steering operation, and a steering angle detection means for generating a detection output according to the magnitude of the steering angle. A self-centering mechanism for a power steering device, characterized in that a control device is provided for controlling the aperture opening of the flow rate control means and the switching operation of the direction switching means in accordance with an output signal from the rain detection means.