JPH05330442A - Power steering device for vehicle - Google Patents

Abstract

PURPOSE:To improve the steering feeling by continuously switching the release of the steering assisting force of a power steering device. CONSTITUTION:A projection part 21b is formed on the input shaft 21 of a control valve 20, and plungers 26 and 27 for controlling each projection quantity of the push rods 26a and 27a are installed on an output shaft 22, and each relative turning angle difference of the input shaft 21 for the output shaft 22 is gradually regulated as the car speed V increases more by controlling the plungers 26 and 27 according to the car speed, and in the final stage, the input shaft 21 and the output shaft 22 are integrally revolved. Accordingly, as the car speed increases, the oil pressure generated by the control valve 20 is reduced to '0' in the final stage, and the operation of the control valve 20 is gradually brought to a stop. Simultaneously with the stop of the operation of the control valve 20, the operation of a hydraulic pump for supplying the high pressure oil into the control valve 20 is suspended, and the load of an engine for driving the hydraulic pump is lightened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention includes a control valve that operates by a steering torque applied to an input shaft to increase the hydraulic pressure generated in a power cylinder as the steering torque increases. The present invention relates to a vehicle power steering device that assists in accordance with generated hydraulic pressure.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in JP-A-8-177775, a centrifugal clutch is provided between a hydraulic pump for supplying hydraulic oil to a control valve and an engine that drives the hydraulic pump, and the clutch is used when the engine speed is low. When the engine speed becomes high, the centrifugal clutch is switched to the disengaged state to stop the operation of the hydraulic pump, cancel the steering assist of the vehicle at high speed and reduce the engine load. I have to.

[0003]

However, in the above-mentioned conventional apparatus, since the disengagement of the centrifugal clutch is switched depending on the engine speed, the engine speed is high even when the vehicle is running at low and medium speeds. In that case, the actuating pump may stop and the assist force may not be applied to the steering wheel operation. Further, when the centrifugal clutch is switched, the presence / absence of the assist force is rapidly switched, so that the driver feels uncomfortable with the change in the steering force, and the steering feeling of the vehicle deteriorates. The present invention has been made to address the above problems, and an object thereof is to prevent the assist force for steering wheel operation from being released during low-to-medium speed running, and also to continuously switch steering assist. An object of the present invention is to provide a vehicle power steering device that enables a driver to always operate a steering wheel with a good steering feeling.

[0004]

In order to achieve the above object, the structural feature of the present invention is that the driving force is transmitted from the engine to the hydraulic pump by being interposed between the engine and the hydraulic pump. An electromagnetic clutch that connects and disconnects the control valve, a hydraulic variable mechanism that is provided in the control valve and that controls the operation of the valve to vary the generated hydraulic pressure with respect to the steering torque applied to the input shaft, a vehicle speed sensor that detects the vehicle speed, and The hydraulic variable mechanism is controlled by the detected vehicle speed to decrease the generated hydraulic pressure with respect to the steering torque as the detected vehicle speed increases so that the generated hydraulic pressure becomes zero at a predetermined vehicle speed or higher, and the detected vehicle speed causes electromagnetic interference. When the detected vehicle speed is less than the prescribed vehicle speed by controlling the clutch, the electromagnetic clutch is maintained in the connected state, and when the detected vehicle speed is equal to or higher than the prescribed vehicle speed, the electromagnetic clutch is disengaged. In the provision of the electrical control means for switching the state.

[0005]

In the present invention constructed as described above, the electric control means controls the hydraulic variable mechanism on the basis of the vehicle speed detected by the vehicle speed sensor to decrease the generated hydraulic pressure with respect to the steering torque as the vehicle speed increases. Since the generated hydraulic pressure is made zero at a predetermined vehicle speed or higher, the hydraulic assist force for steering wheel operation decreases as the vehicle speed increases and becomes zero at a predetermined vehicle speed or higher. At the same time, the electric control means controls the electromagnetic clutch based on the detected vehicle speed,
When the detected vehicle speed is lower than the predetermined vehicle speed, the electromagnetic clutch is maintained in the connected state, and when the detected vehicle speed is higher than the predetermined vehicle speed, the electromagnetic clutch is switched to the disengaged state, so that the hydraulic pressure generated by the control valve becomes zero. When
The operation of the hydraulic pump is stopped.

[0006]

As can be understood from the above description of the operation,
According to the present invention, if the vehicle is traveling at a speed lower than the predetermined vehicle speed, the hydraulic assist force is always applied to the steering wheel operation. it can. Further, since the presence / absence of the hydraulic assist force is continuously switched, the driver does not feel a sense of discomfort associated with the switching of the hydraulic assist force, and the steering feeling of the vehicle is improved.

[0007]

【Example】

a. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows an entire vehicle power steering apparatus according to the embodiment. The power steering system includes a hydraulic pump 16 driven by an engine 11 via a pulley 12, a belt 13, a pulley 14 and an electromagnetic clutch 15. The pump 16 is a reservoir 17
The hydraulic oil therein is pumped up and the high-pressure hydraulic oil is supplied to the control valve 20. The electromagnetic clutch 15 is normally connected,
It is switched to the disconnected state by energization and the transmission of the driving force from the engine 11 to the hydraulic pump 16 is released.

As shown in FIGS. 1 to 3, the control valve 20 includes an input shaft 21 connected to a steering handle 32 via a steering shaft 31, and a pinion 34 meshed with a rack bar 33.
And an output shaft 22 formed integrally therewith. Input shaft 2
1 and the output shaft 22 are coaxially rotatably arranged, the input shaft 21 is connected to one end of the torsion bar 24 by a pin 23, and the output shaft 22 is connected to the other end of the torsion bar 24 by a pin 25. ing. The control valve 20 having such a configuration allows the hydraulic pump 1 to be operated by the relative displacement between the input shaft 21 and the output shaft 22 which causes the torsion bar 24 to be twisted.
The hydraulic oil from 6 is supplied to one oil chamber of the power cylinder 35, and the hydraulic oil in the other oil chamber is discharged to the reservoir 17 to assist the turning operation of the steering handle 32. In this case, from the control valve 20 to the power cylinder 35
The hydraulic pressure supplied to one of the oil chambers is, as shown in FIG.
It has a characteristic of increasing as the torsion angle of the torsion bar 24 increases.

The lower end of the input shaft 21 is formed with protrusions 21a and 21b protruding in the radial direction (the protrusion 21b is longer than the protrusion 21a), and the upper end of the output shaft 22 is provided with a stopper groove 22a, 22b is formed so that the relative rotation of the input shaft 21 and the output shaft 22 is limited within a range of ± 5 degrees. Further, a pair of arm portions 22c and 22d are integrally formed so as to project from the outer periphery of the output shaft 22, and electromagnetic plungers 26 and 27 are fixed to the tips of the arm portions 22c and 22d. The electromagnetic plungers 26 and 27 are push rods 26a and 27 that can move forward and backward.
a, and the push rods 26a and 27a are protruded as the input control voltage E increases so that both rods 2
The distance a between the tips of 6a and 27a is reduced. In this case, as shown in FIG. 5, when the control voltage E changes from “0” to E ₀ , the distance a between the tips is ± of the protrusion 21b.
The distance changes from a predetermined distance a ₀ that allows rotation of 5 degrees to a distance a ₁ that is equal to the thickness of the protrusion 21b.

An electric control circuit 40 is connected to the electromagnetic clutches 15 and the electromagnetic plungers 26 and 27 of the control valve 20. A vehicle speed sensor 41 that detects a vehicle speed V is connected to the electric control circuit 40. As shown by the solid line in FIG. 6, the vehicle speed V detected by the sensor 41 increases from “0” to “0”. When the vehicle speed V increases from the above and the vehicle speed V becomes equal to or higher than the predetermined vehicle speed V ₀ , the control voltage E maintained at the predetermined voltage E ₀ is output to the electromagnetic plungers 26 and 27. Further, the electric control circuit 40 keeps the electromagnetic clutch 15 in the non-energized state until the vehicle speed V detected by the vehicle speed sensor 41 reaches the predetermined vehicle speed V _0, and when the vehicle speed V becomes equal to or higher than the predetermined vehicle speed V ₀ , the electromagnetic clutch 15 operates. Energize 15.

The operation of the embodiment configured as described above will be described. When the vehicle is stopped, the electric control circuit 40 keeps the electromagnetic clutch 15 in the non-energized state and causes the electromagnetic plungers 26 and 27 to have "0". Supply a control voltage representing
Therefore, since the electromagnetic clutch 15 is set to the connected state and the driving force of the engine 11 is supplied to the hydraulic pump 16, the pump 16 supplies high-pressure hydraulic oil to the control valve 20.
Supply to. Further, since the electromagnetic plungers 26 and 27 set the distance a between the push rods 26a and 27a to the predetermined distance a ₀ , the protrusion 21b of the input shaft 21 is not
It can rotate within ± 5 degrees with respect to 2. When the steering handle 32 is rotated in such a state, the steering handle 3 is rotated.
The rotation of 2 is transmitted to the input shaft 21 via the steering shaft 31,
The input shaft 21 rotates in the turning direction of the steering wheel 32. On the other hand, since a road surface reaction force is input to the output shaft 22 from a wheel (not shown) via the rack bar 33 and the pinion 34, the torsion bar 24 is twisted between the input shaft 21 and the output shaft 22. Along with this, a relative rotation angle difference occurs. Due to this relative rotational displacement, the control valve 20 operates to supply high-pressure hydraulic oil to one oil chamber of the power cylinder 35 and discharge the hydraulic oil in the other oil chamber.
The turning operation of the steering handle 32 is performed by the power cylinder 35.
Assisted by the hydraulic pressure of. At this time, the input shaft 21
Since the relative rotational angle difference between the output shaft 22 and the output shaft 22, that is, the torsion angle of the torsion bar 24 is allowed up to the maximum angle (± 5 degrees), the hydraulic pressure generated from the control valve 20 is also allowed up to the maximum (see FIG. 4). As a result, when the steering torque applied to the steering handle 32 becomes large, the control valve 20 supplies a large generated hydraulic pressure to the power cylinder 35, so that the turning operation of the steering handle 32 is performed by the power cylinder 35.
It is assisted by a large hydraulic pressure.

On the other hand, when the vehicle speed V increases, the electric control circuit 40 supplies the electromagnetic plungers 26 and 27 with the control voltage E which increases in proportion to the vehicle speed V (see the solid line in FIG. 6). 26 and 27 reduce the distance a between the push rods 26a and 27a as the vehicle speed V increases. As a result, the maximum torsion angle of the torsion bar 24 decreases as the vehicle speed V increases (see the alternate long and short dash line in FIG. 6). Therefore, the maximum generated hydraulic pressure supplied from the control valve 20 to the power cylinder 35 also increases as the vehicle speed V increases. Decrease. As a result, the hydraulic pressure generated by the control valve 20 with respect to the steering torque applied to the steering wheel 32 also decreases as the vehicle speed V increases (see FIG. 7). Therefore, when the vehicle speed V increases, the power for the turning operation of the steering wheel 32 is increased. The hydraulic assist force by the cylinder 35 also gradually decreases.

When the vehicle speed V reaches the predetermined vehicle speed V ₀ , the control voltage E supplied from the electric control circuit 40 to the electromagnetic plungers 26, 27 becomes the predetermined voltage E ₀ , and the distance a between the push rods 26a, 27a. Is set to a predetermined distance a ₁ , the input shaft 21 and the output shaft 22 always rotate integrally, and the torsion angle of the torsion bar 24 is always “0” (see FIG. 6). As a result, the generated hydraulic pressure of the control valve 20 is always substantially “0” (see FIG. 4), and even if the steering torque is applied to the steering handle 32, the control valve 20 substantially applies the hydraulic pressure to the power cylinder 35. Since it does not occur, the turning operation of the steering wheel 32 is not assisted by hydraulic pressure in this state. At this time, the electric control circuit 40 controls the energization of the electromagnetic clutch 15, so that the clutch 15 is switched to the disengaged state and the hydraulic pump 16
The driving force from the engine 11 is not transmitted to the engine. As a result, when the control valve 20 is not operating, the engine 1
The unnecessary load of 1 is removed. Even if the vehicle speed V is further increased, the electromagnetic clutch 15 is maintained in the disengaged state and the control valve 20 is maintained in the inoperative state by the action of the electric control circuit 40 similar to the above.

As can be understood from the above description of the operation, according to the above embodiment, the vehicle is stopped or the predetermined vehicle speed V ₀ is reached.
If the vehicle is traveling below the speed, the control valve 20 is operated, the electromagnetic clutch 15 is kept in the connected state, and the hydraulic assist force is always applied to the turning operation of the steering handle 32, so that the turning of the handle 32 is performed. The operation is easy. On the other hand, when the vehicle speed V becomes equal to or higher than the predetermined vehicle speed V ₀ , the control valve 2
Since 0 is deactivated and the hydraulic assist force for the turning operation of the steering wheel 32 is released, the operation of the steering wheel 32 during high speed traveling is stable. At the same time, the electromagnetic clutch 15 is switched to the disengaged state and the driving force is not transmitted from the engine 11 to the hydraulic pump 16, so that the load on the engine 11 can be reduced. Further, in the process of releasing the hydraulic assist, the steering wheel 3
Since the hydraulic pressure generated by the control valve 20 gradually decreases with respect to the steering torque applied to No. 2, the hydraulic assist force for steering wheel operation gradually changes from a large value to “0”.
The driver does not feel uncomfortable with the change in the hydraulic assist force, and the steering feeling of the vehicle is improved.

B. Second Embodiment Next, a second embodiment of the present invention will be described. In the second embodiment, the control valve 20 of the first embodiment is changed to a control valve 50 shown in FIG. This control valve 5
0 is an output shaft 5 integrally formed with an input shaft 52 rotatably supported by a cylindrical housing 51 and connected to a steering handle 32, and a pinion 34 meshing with a rack bar 33.
3 and 3. The input shaft 52 and the output shaft 53 are coaxially and rotatably arranged, and the input shaft 52 has a pin 54.
Is connected to one end of the torsion bar 55 by the output shaft 5
3 is connected to the other end of the torsion bar 55 by a pin 56. A valve rotor 57 is integrally formed in the lower portion of the input shaft 52, and the rotor 57 faces a valve sleeve 58 rotatably mounted on the inner circumference of the housing 51. The valve sleeve 58 is connected to the output shaft 53 via a pin 53a, and rotates integrally with the coaxial shaft 53. The control valve 50 causes the hydraulic oil supplied from the hydraulic pump 16 to the supply port 51a to flow through one of the input / output ports 51b and 51c by the relative rotational displacement of the valve rotor 57 and the valve sleeve 58. The oil is supplied to one oil chamber of the power cylinder 35, and the operating oil in the other oil chamber of the cylinder 35 is input / output port 51.
It is discharged to the reservoir 17 through the other of b and 51c and the discharge port 51d.

A piezoelectric actuator 62 is housed in the upper portion of the housing 51 which is partitioned by an oil seal 61. As shown in FIG. 9, the piezoelectric actuator 62 is formed by stacking piezoelectric elements, extends in the axial direction according to an input voltage, and both ends thereof are supported by thrust bearing rings 63a and 63b. The axial displacement of the thrust bearing rings 63a, 63b is determined by the input shaft 52.
It is regulated by stoppers 64a and 64b fixed to the input shaft 52.
Is in contact with the outer peripheral surface of the
The outer peripheral surface of 63b is in contact with the inner peripheral surface of the valve sleeve 58. With this configuration, when the control voltage E is applied to the piezoelectric actuator 62, the entire length of the piezoelectric actuator 62 becomes longer, the thrust bearing rings 63a and 63b expand in the radial direction, and the frictional force against the relative rotation between the input shaft 52 and the valve sleeve 58 is generated. To increase. Then, when the control voltage E reaches the predetermined voltage E ₀ , the frictional force becomes maximum and the input shaft 52 and the valve sleeve 58 rotate integrally. In addition, in the second embodiment, the electric control circuit 40 has a configuration shown in FIG.
As shown in, the control voltage E is output to the piezoelectric actuator 62, which increases as the vehicle speed V increases and becomes the predetermined voltage E ₀ at a predetermined vehicle speed V ₀ or higher. The other structure is the same as that of the first embodiment.

In the second embodiment constructed as described above, the electric control circuit 40 has a vehicle speed V as shown in FIG.
A control voltage that increases proportionally with the increase of the control voltage and becomes the predetermined voltage E ₀ at the predetermined vehicle speed V ₀ is output to the piezoelectric actuator 62. Due to this increase in the control voltage E, the piezoelectric actuator 62 is actuated to operate the valve sleeve 58 of the input shaft 52.
Therefore, even if a steering torque is applied to the input shaft 52 from the steering wheel 32, the relative rotation between the input shaft 52 (the valve rotor 54) and the valve sleeve 58 (the output shaft 53) with respect to the same steering torque. The angle difference is reduced. When the control voltage E reaches the predetermined voltage E ₀ ,
The relative rotation angle difference becomes "0", and the control valve 50 stops operating. As a result, when the vehicle speed V increases, the hydraulic pressure generated by the control valve 50 with respect to the steering torque applied to the steering wheel 32 gradually decreases, and when the vehicle speed V is equal to or higher than the predetermined vehicle speed V ₀ , the generated hydraulic pressure is substantially “0”. (See FIG. 11), the hydraulic assist force of the power cylinder 35 with respect to the turning operation of the steering wheel 32 changes according to the vehicle speed V as in the first embodiment. Further, since the electric control circuit 40 controls the electromagnetic clutch 15 in the same manner as in the first embodiment, the same effect as in the first embodiment can be expected in the second embodiment.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of a vehicle power steering device according to first and second embodiments of the present invention.

FIG. 2 is a vertical sectional front view of a control valve according to the first embodiment.

FIG. 3 is a cross-sectional view of the control valve taken along line 3-3 of FIG.

FIG. 4 is a change characteristic graph of the hydraulic pressure generated by the control valve with respect to the torsion angle of the torsion bar.

FIG. 5 is a change characteristic graph of a distance between push rods with respect to a control voltage.

FIG. 6 is a change characteristic graph of a control voltage and a torsion angle of a torsion bar with respect to a vehicle speed.

FIG. 7 is a change characteristic graph of generated hydraulic pressure of the control valve with respect to steering torque.

FIG. 8 is a vertical sectional front view of a control valve according to a second embodiment.

FIG. 9 is a change characteristic graph showing the expansion of the piezoelectric actuator with respect to the input voltage.

FIG. 10 is a change characteristic graph of control voltage with respect to vehicle speed.

FIG. 11 is a change characteristic graph of generated hydraulic pressure of the control valve with respect to steering torque.

[Explanation of symbols]

11 ... Engine, 15 ... Electromagnetic clutch, 16 ... Hydraulic pump, 20 ... Control valve, 21 ... Input shaft, 21a, 21b
... Projection part, 22 ... Output shaft, 22a, 22b ... Stopper groove, 24 ... Torsion bar, 26, 27 ... Electromagnetic plunger, 26a, 27a ... Push rod, 32 ... Steering handle, 35 ... Power cylinder, 40 ... Electric control circuit Four
1 ... Vehicle speed sensor, 50 ... Control valve, 52 ... Input shaft, 5
3 ... Output shaft, 55 ... Torsion bar, 57 ... Valve rotor, 58 ... Valve sleeve, 62 ... Piezoelectric actuator, 63a, 63b ... Thrust bearing, 64a, 6
4b ... Stopper.

Claims (1)

[Claims] Claim: What is claimed is: 1. A hydraulic pump driven by an engine, and hydraulic oil supplied from the hydraulic pump actuates by a steering torque applied to an input shaft to increase hydraulic pressure generated in a power cylinder as the steering torque increases. In a vehicle power steering device including a control valve, an electromagnetic clutch that is interposed between the engine and the hydraulic pump and that interrupts transmission of driving force from the engine to the hydraulic pump, the control valve A hydraulic pressure variable mechanism that is provided inside to regulate the operation of the valve to vary the generated hydraulic pressure with respect to the steering torque; a vehicle speed sensor that detects a vehicle speed; and a hydraulic pressure variable mechanism that controls the hydraulic pressure variable mechanism based on the detected vehicle speed. As the detected vehicle speed increases, the hydraulic pressure generated with respect to the steering torque is decreased to generate the hydraulic pressure above the predetermined vehicle speed. When the pressure is zero and the detected vehicle speed controls the electromagnetic clutch to maintain the electromagnetic clutch in the connected state when the detected vehicle speed is less than the predetermined vehicle speed, the detected vehicle speed is the predetermined vehicle speed. An electric control means for switching the electromagnetic clutch to a disengaged state in the above case is provided.