JPS63130475A - Power steering device having reaction mechanism - Google Patents

Abstract

PURPOSE:To change the return spring characteristic between an input shaft and an output shaft independently between a handle steering condition and a returning condition by independently controlling oil pressure applied to first and second reaction chambers which are mutually independently provided. CONSTITUTION:A cylindrical large diameter part 32 is integrally formed with the end part of an input shaft 12, and the outer peripheral face 32a of the large diameter part 32 is rotatably fitted in the inner peripheral face 19 of a valve housing 10a. The pairs of grooves which are parallel to a housing groove 33 are formed on the outer peripheral face 32a of the cylindrical large diameter part 32, in positions nearly corresponding to two pairs of radial projecting parts 31. And, a first reaction chamber 34 and a second reaction chamber 38 are formed by these grooves and the inner peripheral face 19 of the valve housing 10a. The first reaction chamber 34 is connected to a first introduction port 37 and the second reaction chamber 38 is connected to a second introduction port 41, but both reaction chambers are not connected to each other. Pistons 36, 40 which are housed in the reaction chambers are mutually independently operated by pressures applied to the reaction chambers 34, 38.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power steering device equipped with a reaction force mechanism that can change the characteristics of manual steering torque depending on the driving condition of an automobile, and in particular to a power steering device for steering wheel return. Regarding improvement of characteristics.

[Prior art]

The reaction force mechanism of this type of power steering device, for example, as shown in FIG. It has reaction force pistons 3 for urging, and reaction force chambers 4 that apply working fluid pressure to each reaction force piston 3 are communicated with each other. Therefore, when both shafts rotate relative to each other in left and right directions about the neutral position, the torsion spring characteristics between the two shafts are the same on both the cutting side and the return side. Thus, a servo valve that operates according to the relative rotation angle between the two shafts 1 and 2 controls the supply and discharge of working fluid to the power cylinder that applies assist force to the output shaft 2 and reduces manual steering torque. I try to do that.

[Problem that the invention seeks to solve]

In such conventional technology, in an operating condition where the manual steering torque is large, that is, in an operating condition where the hydraulic pressure in the reaction force chamber is large and the torsion spring characteristics between the two shafts are stiff, the steering wheel is suddenly turned after turning the steering wheel sharply. If you try to return the handle, there is a problem in that the torsion spring characteristics are stiff, so the resistance when returning the handle becomes large. The present invention makes it possible to solve such problems.

[Means for solving the problem] For this purpose, the power steering device equipped with the reaction force mechanism according to the present invention has a housing 10 as illustrated in FIGS. 1 and 2.
an input shaft 12 and an output shaft 11 which are rotatably coaxially supported and elastically connected to each other so as to be rotatable relative to each other; 1
a servo valve 20 that controls the supply and discharge of working fluid to the power cylinder that provides the assist force to the power cylinder; In the power steering device, the reaction force mechanism 30 includes a radial protrusion 31 provided on either one of the shafts 11, 12.
and a large diameter portion 32 which is provided on the other of the shafts 11 and 12 and has a storage 133 for rotatably housing the radial protrusion 31 and is rotatably fitted into the housing 10; first and second reaction force chambers 34 and 38 formed independently from each other between the large diameter portion and the housing 10;
A first cylinder hole 35 formed in the large diameter portion 32 and opening into the first reaction force chamber 34 is fitted into the first cylinder hole 35 so as to be able to come into contact with the radial protrusion 31 and apply a force to the first reaction force chamber 34. a first reaction force piston 36 that urges both shafts 11 and 12 from one direction toward a relative rotational neutral position by a working fluid pressure;
A second cylinder hole 39 formed in the large diameter portion 32 and opening into the second reaction force chamber 38 is fitted into the second cylinder hole 39 so as to be able to come into contact with the radial protrusion 31, so that the second reaction force is applied to the second reaction force chamber 38. The second reaction force piston 40 urges the shafts 11 and 12 toward a relative rotational neutral position in a direction opposite to the one direction using the working fluid pressure.

[Effect]

When the steering wheel is turned in one direction from the straight-ahead state and further in that direction, the output shaft 11 rotates in that direction from the straight-ahead state.The rotation angle of the human power shaft 12 is the output This is larger than the rotation angle of the shaft 110. In this state, one reaction force piston, for example, the first reaction force piston 3
6 is in contact with the radial protrusion 31, and both shafts 11, 12
The torsion spring characteristics during this period are controlled by the hydraulic pressure applied to the first reaction force chamber 34. In the state where the handle is turned in one direction, if the handle is returned faster than the return speed when the handle is released, the output shaft 11 is rotated in one direction from the position in the straight-ahead state as described above, but the human power shaft 12020
The rotation angle is smaller than the rotation angle of the force axis 110. In this state, only the second reaction piston 40 is connected to the radial protrusion 31.
The torsion spring characteristics between the two shafts 11 and 12 are the second
It is controlled by the oil pressure applied to the reaction force chamber 38. When the handle is turned in the other direction, the torsion spring characteristics between the shafts 11 and 12 are controlled by the hydraulic pressure applied to the second reaction chamber 3 when the handle is turned, and when the handle is released and returned. When returning faster than the speed, it is controlled by the oil pressure applied to the first reaction force chamber 34.

〔Effect of the invention〕

According to the present invention as described above, by independently controlling the hydraulic pressure applied to the first reaction force chamber and the second reaction force chamber, which are provided independently from each other, the input shaft and output shaft of the power steering device are controlled. The return spring characteristics between the two shafts can be changed independently for the state in which the steering wheel is turned in and the state in which it is returned quickly. Even in a driving state where the torsion spring characteristics are stiff, the torsion spring characteristics can be automatically made soft when the steering wheel is returned quickly, and the steering wheel can be returned smoothly.

〔Example〕

First, the present invention will be explained with reference to the embodiments shown in FIGS. 1 and 2.

Valve housings 10 fixed to each other as shown in FIG.
An output shaft 11 is rotatably supported within a housing 10 consisting of a gear housing 10b and a gear housing 10b by two bearings 15 and 18, and a pinion lla of the output shaft 11 is slidable in a direction substantially perpendicular thereto. The racks 14a of the rack shafts 14 supported by the racks 14a are engaged with each other. This rack shaft 14 has a piston rod 54a of the power cylinder 54 (see FIG. 3).
are connected to the steering wheels via a closed steering linkage. Inside the housing 10, a human power shaft 12, which is a steering shaft, is connected to an output shaft 11 by bearings 17 and 18.
coaxially supported; both shafts 11 and 12 are elastically connected by a torsion bar 13 passing through the center hole of the human power shaft 12, and based on the relative rotation of the shafts 11 and 12; A servo valve 20 is provided. The servo valve 20 has a rotor valve member 21 formed on the human power shaft 12.
A sleeve valve member 22 is fitted between the rotor valve member 21 and the housing 10 and connected to the output shaft 11 by a pin 23, and includes a supply boat 25 and a discharge boat 26.
and a pair of distribution bows) 27a.

27b. The working fluid from the supply boat 25 exerts equal pressure on both distribution boats 27a, 27b in the neutral position where the relative rotation angle between the shafts 11, 12 is O, and when both shafts 11.12 are in the neutral position If the relative rotation deviates, a pressure difference corresponding to the direction and relative rotation angle will be distributed between the two bows) 27a.

27b to generate assist force in the power cylinder 54.

Next, the reaction force mechanism 30 provided between the shafts 11 and 12 will be explained. As shown in Figures 1 and 2, the human power axis 1
Two pairs of radial protrusions 31 are integrally formed at the end of the second example of the output shaft 11, protruding in opposite directions along the axial direction. Further, a cylindrical large diameter portion 32 is integrally formed at the end of the output shaft 11 on the side of the human power shaft 12, and therein is a housing for housing each radial protrusion 31 so as to be relatively rotatable at a predetermined angle. A groove 33 is formed. Outer peripheral surface 3 of large diameter portion 32
2a is rotatably fitted to the inner peripheral surface 19 of the valve housing 10a, and two pairs of radial protrusions 31 are provided on the outer peripheral surface 32a.
Two pairs of grooves parallel to the storage groove 33 are formed at positions substantially corresponding to the storage grooves 33, and these grooves and the inner circumferential surface 19 of the valve housing 10a form a pair of first reaction force chambers 34 and a pair of second reaction force chambers 38, respectively. and two annular grooves 3 corresponding to each reaction chamber 34,38.
4a.

38a is formed. The first reaction force chambers 34 communicate with each other through a first annular groove 34a, and the housing 10
It communicates with the first introduction boat 37 formed in
The reaction force chambers 38 are communicated with each other by the second annular groove 38a and also communicated with the second introduction boat 41, but both reaction force chambers 34
．． , 38 are not communicated with each other.

As mainly shown in FIG. 2, the first reaction force chamber 34 and the storage groove 3
3, a pair of first cylinder holes 35 are provided at diagonal positions with respect to the center of both shafts 11.12, and are substantially perpendicular to one pair of radial protrusions 31. First
A reaction piston 36 is fitted into the partition wall between the second reaction chamber 38 and the storage groove 33, and the other pair of radial protrusions 31 are provided at diagonal positions opposite to the first cylinder hole 35. A pair of second cylinder holes 39 are formed substantially perpendicular to the second cylinder holes 39, into which a second reaction piston 40 is fitted. The first and second reaction pistons 36.40 move the radial protrusion 31 between the shafts 11 and 11 by the working fluid pressure applied to the first and second reaction chambers 34.38.
The reaction force pistons 36 and 40 are biased toward the relative rotational neutral position of 12 from opposite directions.
The presence of the flange formed on the 8 side prevents the radial protrusion 31 from being biased beyond the neutral position.

The power steering device (indicated by reference numeral P) equipped with the reaction force mechanism described above is used by being connected as shown in FIG. 3, for example. That is, the working fluid from the supply pump 50 having a constant discharge amount by a built-in flow rate adjustment valve or the like is divided at a predetermined ratio by a flow dividing valve 51, and one flow rate is passed through a conduit 55 to a servo valve of the power steering device P. 20 supply boats 25, and the other flow rate is bypassed by an electromagnetic throttle valve 52 to control the pressure through a pipe 56 and an electromagnetic switching valve 53 to the first and 2nd introduction baud) is supplied at 37.41. The electromagnetic throttle valve 52 is normally fully open, and its opening decreases as the control current (2) applied to the solenoid 52a increases. Introduction board) 3
7.41 is communicated with the reservoir 59, but if the control current ia is applied to one solenoid 53a, the left position is selected and the working fluid pressure of the conduit 56 is applied to the first introduction boat 37, and at the same time the second introduction boat 37 is connected to the reservoir 59. By communicating the boat 41 with the reservoir 59 and applying the control current 1b to the other solenoid 53b, the right position is selected and the working fluid pressure of the conduit 56 is applied to the second introduction boat 41, and at the same time the first introduction boat 37 is communicated with the reservoir 59. The discharge boat 26 of the servo valve 20 is in communication with the reservoir 59, and both distribution boats 27
a.

Both chambers of the power cylinder 54 are communicated with 27b.

A control circuit for controlling the electromagnetic throttle valve 52 and the electromagnetic switching valve 53 shown in FIG. 3 is shown in FIG. The electronic control unit 60 consists of a microprocessor (hereinafter simply referred to as CPU) 61, a read-only memory (hereinafter simply referred to as ROM) 62, a writable memory (hereinafter simply referred to as RAM), and an input/output interface 64. A- on face 64
A steering angle sensor 70 that detects the rotation angle θ of the steering wheel shaft and a vehicle speed sensor 71 that detects the vehicle speed V of the automobile are connected via D converters 72 and 73, and an electromagnetic throttle valve 52 is connected via amplifiers 74 and 75. The solenoid 52a and the solenoids 53a and 63b of the electromagnetic switching valve 53 are connected.

The ROM 62 stores a control pattern of the control current (2) applied to the solenoid 52a of the electromagnetic throttle valve 52 as a characteristic map. Figures 5 (a) and (b) graphically show this control pattern for vehicle speed ■ and steering angle θ. Characteristic B shows a control pattern, ie, a cutting map in a cutting state, and characteristic B shows a control pattern, ie, a return map, in a returning state, ie, a state in which the steering wheel that has been turned in one direction is returned to a straight forward state. Figure 5(a) shows the control pattern for vehicle speed at a constant steering angle, and (b)
) shows a control pattern for the steering angle θ at a constant vehicle speed. Each solenoid 53 of the electromagnetic switching valve 53
The control pattern of the control currents ia and ib applied to a and 53b is as shown in Fig. 6, and when the steering angle θ is within a small range (−α × θ × α) centered on the straight-ahead state, both The current applied to the solenoids 53a and 53b is O, but θ≧
When α, a control current with a constant value of 1a is applied to one solenoid 53a, and when θ≦−α, a control current with a constant value of 1b is applied to the other solenoid 53b. .

Next, the control operation of the control circuit shown in FIG. 4 will be explained with reference to the flowchart shown in FIG. Note that the ROM 62 stores a control program for executing the control operations according to this flowchart.

When you turn on the main switch of the car, the electronic control device 60
sets each variable to 0 or a predetermined initial value. Steering angle θ and vehicle speed V that change moment by moment in the driving state of the car
is detected by the steering angle sensor 70 and the vehicle speed sensor 71, and the current value is stored in the concave road register in the electronic control device 60. The CPU 61 operates at predetermined time intervals (for example, 0.5
Each time an interrupt signal is inputted every second (seconds), a processing operation is executed based on the control program.

The CPU 61 first reads the current steering angle θ and vehicle speed ■ stored in the register in step 100 of the flowchart in FIG.
It is determined whether or not θ is less than α, and if -α is less than θ and α, in the next step 102, the current output to the electromagnetic switching valve 530 and both solenoids 53a and 53b is stopped, and the reaction force mechanism 3
After communicating the two-way blade chambers 34 and 3B of 0 to the reservoir 59,
Stop execution of the control program. In this state, that is, in a state in which the steering angle θ is within the range of ±α with respect to the straight-ahead state, no pressure is applied to the double-sided blade chambers 34 and 38, so the reaction force mechanism 30 does not operate.

If α<θ is not less than α, the CPU 61 advances the control operation from step 101 to step 103.

After step 103, depending on the steering angle θ and the range of the steering angle change rate θ calculated in advance in the concave road step,
It is divided into the following four operating states.

(1) First, if θ>0 and θ>0, that is, the handle is in the cutting state in one direction, the CPU 61 executes the control operation from step 103 to steps 104, 105, 1
06, 110, in step 104 the control current ia is output to one solenoid F 53 a of the electromagnetic switching valve 53 to set it to the left position, and in step 106 the vehicle speed ■ and steering angle θ are determined from the cutting map A in FIG. A control current value I is searched based on the value I, and in step 110, a control current having this value I is applied to the solenoid 52a of the electromagnetic throttle valve δ2, and then execution of the control program is stopped.

In this state, the working fluid pressure in the V path 56 changes almost in the same way as in the cutting map A in FIG. The force is applied from the introduction boat 37 to the first reaction force chamber 34 , and the second reaction force chamber 38 is communicated with the reservoir 59 via the second introduction boat 41 , the conduit 38 and the electromagnetic switching valve 53 . As a result, the assist force decreases as the vehicle speed 1 and the steering angle θ increase, and the ratio of the manual steering torque to the steering reaction torque from the steered wheels increases.

(2) In step 103, θ>0 and θ>
0, that is, if the handle is in the returning state from one direction, the CPU 61 advances the control operation from step 103 to steps 104, 105, 109, and 110, performs the same process as described above in step 104, and performs the same process as described above in step 109. Search the control current value ■ based on the vehicle speed V and steering angle θ from the return map B in Figure 5, and proceed to step 1.
At step 10, the control current having the value ■ is applied to the solenoid 52a of the electromagnetic throttle valve δ2, and then the execution of the control program is stopped. In this case, the point where the working fluid pressure in the pipe line 56 increases overall, that is, the torsion spring characteristics between the input and output shafts 11 and 12 provided by the first reaction piston 36 is greater than in the case (1) above. The operating state is the same as in (1) above, except that it is rigid.

In this state, if the handle is returned at a slower rate than the handle return speed when the handle is released, the torsion spring characteristics between the shafts 11 and 12 provided by the first reaction piston 36 become more rigid, so that the output shaft 11 is cut into the handle. The differential pressure of the working fluid applied to the power cylinder 54 that provides the directional assist force is less than in the case of a cut, and therefore the return of the handle is lighter. In addition, when the handle is returned faster than the release speed, the first reaction piston 36 is moved by the radial protrusion 31
Further apart, the second reaction piston 40 comes into contact with the radial protrusion 31, so that working fluid flows into and out of the power cylinder 54 to operate the output shaft 11 in the return direction.

Since the working fluid pressure in the second reaction chamber 38 that urges the second reaction piston 40 is 0, the torsion spring characteristics between the shafts 11 and 12 are extremely soft, and therefore the servo valve 20
Since the amount of working fluid flowing into and out of the power cylinder 54 through the power cylinder 54 increases, the return of the handle becomes extremely light.

In addition, in the above states (1) and (2), if the steering wheel is turned to the steering angle θ2 and then turned back, and then turned again after returning to the steering angle θl, the control current I will be as shown in FIG.
A hysteresis loop is drawn as shown by the arrow in b), and the assist force etc. change accordingly.

(3) In step 103, if θ>0 and θ<0, that is, the handle is in the cutting state in the other direction, the CPU 61 advances the control operation from step 103 to steps 107, 108, 106° 110. After that, execution of the control program is stopped. In this case, the electromagnetic switching valve 53 is in the right position, and therefore the working fluid pressure in the conduit 56 is transferred from the second introduction boat 41 of the reaction force mechanism 30 to the second reaction chamber 3.
8, the state is the same as in (1) above except that the first reaction force chamber 34 is communicated with the reservoir 59, and its operation is the same as in (1) above except that the handle is cut in the other direction.
) is the same as

(4) In step 103, θ is not 0 but θ is O
If not, that is, if the handle is in the returning state from the other direction, the CPU 6 advances the control operation from step 103 to steps 107, 108, 109, and 110, and then stops execution of the control program. In this case, as in (3) above, the working fluid pressure in the pipe line 56 is reduced to the second reaction force chamber 3.
The state is the same as (2) above except that the first reaction force chamber 34 is communicated with the reservoir 69, and its operation is the same as (2) above except that the handle is cut in the other direction. )
is the same as

The CPU 61 repeatedly executes the above-mentioned processing operation according to the flowchart of FIG. 7 every time an interrupt signal is inputted at a predetermined short time interval, and the vehicle speed is determined as follows.

The opening degree of the electromagnetic throttle valve 52 is set depending on the sign of the steering angle θ and the steering angle change rate θ, and the electromagnetic switching valve 53 is switched. As a result, a manual steering torque corresponding to the vehicle speed and steering angle can be obtained, and the manual steering torque can be made smaller in the return state than in the turning state, making it easier to operate the steering wheel. .

FIG. 8 shows an example of use of the power steering device P according to the present invention, which is different from that shown in FIG. In this example, the working fluid from the supply boat δ0 having a constant discharge amount is divided at a predetermined ratio by the diverter valve 51, and one flow rate is supplied to the servo valve 20 of the power steering device P via the pipe 55. The other flow rate is equally divided by a flow divider valve 80 and passed through a pipe 87 and 8 days to the first and second supply ports 37 and 41 of the reaction force mechanism 30 of the power steering device P. Supplied. Lines 87 and 88 are bypassed and pressure controlled by electromagnetic throttle valves 81 and 82. The electromagnetic throttle valves 81 and 82 have the same characteristics and are normally fully open, but the degree of opening decreases as the value of the control current I applied to the solenoids 81a and 82a increases. .

A control circuit for controlling the electromagnetic throttle valves 81 and 82 shown in FIG. 8 is shown in FIG. The configuration of this control circuit is substantially the same as that shown in FIG.
Instead of the electromagnetic throttle valves 81 and 82, the amplifiers 74a and 7
The only difference is that it is connected to the human output interface 64 via 5a. The control pattern of the control current 1 applied to the electromagnetic throttle valves 81, 820 and solenoids 81a and 82a is stored in the R0M62a, and this control pattern is substantially the same as that shown in FIG.
The value of the control current I is O when the steering angle θ is within the range of ±α around the straight-ahead state.

Next, the outline of the control operation of the control circuit shown in FIG. 9 will be explained with reference to the flowchart shown in FIG. 10. The CPU 61 executes processing operations based on the control program according to this flowchart each time an interrupt signal is input at a predetermined time interval. Note that this control program is stored in the R0M62a.

The CPU 61 first reads the current steering angle θ and vehicle speed V in step 120, and if -α<θ<α, advances the control operation from step 121 to step 122.
Stop execution of the control program. In this state, the solenoid 81a.

The current output to 82a is stopped and both electromagnetic throttle valves 81.8
2 is fully opened, the pressure applied to the double blade chambers 34 and 38 becomes 0, and the reaction force mechanism 3o does not operate. −α×θ
<If not α, the CPU 51 executes the control operation in step 121.
Then proceed to step 123. After step 123,
As with the above-mentioned usage conditions, there are four operating conditions depending on the range of the steering angle θ and its rate of change δ.

First, if θ>0 and θ>0, the CPU 61 executes the control operation from step 123 to steps 124, 125, 1
After advancing 26,128 steps, execution of the control program is stopped. In this state, the current output to the solenoid 82a is stopped, so the second electromagnetic throttle valve 82 is fully opened, the pressure applied to the second introduction boat 41 becomes 0, and the first
Since the control current of the value I searched from the depth of cut map A in FIG. 5 is output to the solenoid 81a of the electromagnetic throttle valve 81, the working fluid pressure in the conduit 87 is determined according to the depth of cut map A in FIG.
The working fluid pressure changes in the same manner as the first introduction boat 37.
is applied to the first reaction force chamber 34 from.

In this case, the operating state is the same as in case (1) in the above usage example.

If θ〉0 and θ〉0, the CPU 61 performs control operations from step 123 to step 124, step 125,
After proceeding to steps 127 and 128, execution of the control program is stopped. In this state, as above, the second introduction boat 4
1 becomes 0, but the control current of the value ■ searched from the return map B in FIG. The fluid pressure changes similarly to the return map B in FIG. 5, and this working fluid pressure is applied from the first introduction boat 37 to the first reaction force chamber 34. In this case, the operating state is the same as in case (2) in the above usage example.

If θ〉0 and θ〈0, the CPU 61 executes the control operation from step 123 to step 129゜130.13
After proceeding to 1,133, execution of the control program is stopped. In this state, the pressure applied to the first introduction boat 37 is O, and the second introduction boat 41 is in the second reaction force chamber 38.
A working fluid pressure that changes in the same way as in the cut map A in FIG. 5 is applied through . In this case, (
The operating state is the same as in case 3).

If θ>0 and d<0, the CPU 61 performs control operations from step 123 to step 129, 130,
After proceeding to steps 132 and 133, execution of the control program is stopped. In this state, the pressure applied to the first introduction boat 37 becomes 0, and the working fluid pressure that changes like the return map B in FIG. 5 is applied to the second reaction force chamber 38 via the second introduction boat 41. be done. In this case, the operating state is the same as in the case ()1) in the above usage example.

Particularly in this example, as the vehicle speed increases, the defined blade chamber 3
It is also possible to simultaneously increase the working fluid pressure introduced into 4.38.

The CPU 61 repeatedly executes the above-described processing operation according to the flowchart of FIG. 10 at predetermined short time intervals. As a result, as in the above usage example, a manual steering torque corresponding to the vehicle speed and steering angle can be obtained, and the manual steering torque is made smaller in the returning state than in the turning state, so that the steering wheel Operation can be facilitated.

In the above usage example, the control current value I to be applied to the electromagnetic throttle valve is searched and determined from maps A and B, which differ depending on whether the handle is in the cutting state or in the return state. The control current value I may be determined by searching only from one map A. In that case, if you let go of the handle and return it slower than the return speed, the handle will not necessarily become lighter, but if you release it and return it faster than the return speed, the handle will become lighter. The return of the handle becomes easier.

[Brief explanation of the drawing]

1 and 2 show an embodiment of a power steering device equipped with a reaction force mechanism according to the present invention, in which FIG. 1 is a longitudinal sectional view, FIG. 2 is a sectional view taken along the line ■-■ in FIG. Figures 3 to 7 show the first usage example, Figure 3 is a connection diagram with related equipment, Figure 4 is a control circuit diagram of each solenoid valve, and Figure 5 is the control applied to the solenoid throttle valve. A characteristic diagram of the current, Figure 6 is a characteristic diagram of the control current applied to the electromagnetic switching valve, Figure 7 is a flowchart of the control program,
Figures 8 to 10 show the second usage example, Figure 8 is a connection diagram with related equipment, Figure 9 is a control circuit diagram of the electromagnetic throttle valve, Figure 10 is a flowchart of the control program, and Figure 11 is a flowchart of the control program. The figure is a diagram corresponding to FIG. 2 of the prior art. Explanation of symbols 10...Housing, 11...Output shaft, 12◆...
Human power shaft, 20... Servo valve, 30... Reaction force mechanism, 3
1... Radial protrusion, 32... Large diameter part, 33...
Storage groove, 34... First reaction force chamber, 36... First cylinder hole, 36... First reaction force piston, 38... Second reaction force chamber, 39... Second cylinder hole , 40... second reaction piston.

Claims (1)

[Claims] An input shaft and an output shaft are rotatably coaxially supported within the housing and are elastically connected to be relatively rotatable; a servo valve that controls the supply and discharge of working fluid to and from the power cylinder, and a reaction force mechanism that changes the assist force by changing the torsion spring characteristics between the two shafts in accordance with the applied working fluid pressure. In the power steering device, the reaction force mechanism includes a radial protrusion provided on either one of the shafts, and a housing provided on the other of the shafts for rotatably housing the radial protrusion. a large diameter portion having a groove and rotatably fitted within the housing; first and second reaction force chambers formed independently from each other between the large diameter portion and the housing; The first cylinder hole formed in the diameter portion and opening into the first reaction force chamber is fitted into the first cylinder hole so as to be able to come into contact with the radial protrusion, and the two cylinders are driven by the working fluid pressure applied to the first reaction force chamber. a first reaction force piston that urges the shaft from one direction toward a relative rotational neutral position; and the radial protrusion in a second cylinder hole formed in the large diameter portion and opening into the second reaction force chamber. a second reaction force that urges both shafts toward a relative rotational neutral position from a direction opposite to the one direction by means of working fluid pressure applied to the second reaction force chamber; A power steering device equipped with a reaction force mechanism characterized by comprising a piston.