JPH0659837B2 - Power steering device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power steering apparatus.

2. Description of the Related Art Generally, hydraulic oil is selectively supplied to and discharged from two working chambers in a cylinder separated by a piston by a hydraulic control mechanism to assist the steering operation of a steering member connected to the piston. A power steering device that requires a steering assist force is required when the vehicle is running at low speed or when the vehicle is stationary, but on the other hand, steering is required when running at high speed with less ground resistance than when the vehicle is running at low speed. From the standpoint of improving stability, it does not require much steering assistance. That is, it is preferable that the handlebar load be lightened when the vehicle is traveling at low speed or stationary, and the handlebar load is heavy when the vehicle is traveling at high speed.

Therefore, in order to meet such a request, the applicant of the present invention
For example, Japanese Patent Application No. 59-231973 (Japanese Patent Application Laid-Open No. 61-11).
No. 0671)). This power steering device is provided with a bypass passage for branching the hydraulic oil discharged from the pump from a supply passage for feeding the hydraulic oil to two working chambers separated by a piston and returning the hydraulic oil to a tank. On the way, a fixed throttle mechanism that allows a limited flow of hydraulic oil from the supply passage toward the bypass passage, and a variable throttle mechanism that changes the opening area of the bypass passage according to the vehicle speed on the downstream side of the fixed throttle mechanism. And the movement of the spool valve that constitutes the hydraulic control mechanism,
A hydraulic reaction force mechanism for braking according to the pressure difference between the hydraulic pressure generated in the fixed throttle mechanism and the hydraulic pressure generated in the variable throttle mechanism is provided.

A conventional power steering apparatus having such a configuration is composed of a fixed throttle mechanism provided in the middle of a bypass passage branched from a hydraulic oil supply passage and a variable throttle mechanism that changes the opening area of the bypass passage according to the vehicle speed. The hydraulic pressure generated between the two is guided to the hydraulic reaction mechanism, and the movement of the spool valve that constitutes the hydraulic control mechanism can be gradually braked by this hydraulic reaction mechanism, which smooths the steering wheel steering wheel load according to the vehicle speed. It can be increased or decreased.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a conventional power steering apparatus, when the vehicle is in a low speed state, the variable throttle mechanism is loosened so that the hydraulic reaction mechanism does not act.

Then, the flow rate in the bypass channel increases and the flow rate in the supply channel decreases. For this reason, the pressure of the working chamber in the cylinder does not rise sufficiently, and the steering assisting force is not sufficiently exerted.
If the variable throttle mechanism is throttled, the pressure of the hydraulic reaction force mechanism rises, which also hinders the steering. On the other hand, when the vehicle is in a high-speed state, it is desirable that the steering reaction force is large from the viewpoint of steering stability, so the variable throttle mechanism is throttled. Since the pressure is decreasing inside, the variable throttle downstream is more strongly throttled to increase the pressure introduced into the hydraulic reaction mechanism.
For this reason, the flow rate in the bypass path is greatly reduced, and the flow rate in the supply path is correspondingly increased. As a result, the flow resistance of the hydraulic control mechanism increases, the pressure in the supply path increases, the discharge pressure of the pump increases, and the pump does extra work, resulting in energy loss. It was

Means for Solving Problems In order to solve such conventional problems, the present invention provides
When an input member driven by the operation force of the steered wheels, an output member for driving the steering member that gives a steering force to the wheels, and a relative rotational displacement between the input member and the output member,
A hydraulic control mechanism for selectively supplying and discharging hydraulic oil to and from two working chambers in a cylinder separated by a piston to assist the steering operation of a steering member connected to the piston, and to control the vehicle speed. Accordingly, in the power steering device including the hydraulic reaction mechanism that applies a reaction force when the hydraulic control mechanism moves, the power steering device is branched from the supply passage for supplying the hydraulic oil discharged from the pump to the two working chambers. A bypass passage for returning hydraulic oil to the tank, and two throttle mechanisms are provided in the middle of the bypass passage, and at least the upstream throttle mechanism is a variable throttle mechanism for changing the opening area of the bypass passage. In addition, an oil passage branched from the bypass passage between these two throttle mechanisms is provided to communicate with the hydraulic reaction mechanism, while controlling the throttle amount of the variable throttle mechanism. The vehicle speed signal and the hydraulic pressure sensor obtained from the vehicle speed sensor are provided by providing a controller and a vehicle speed sensor for inputting the detected vehicle speed signal to the controller and mounting a hydraulic pressure sensor for detecting the hydraulic pressure in the bypass passage between the two throttle mechanisms. A hydraulic signal obtained from the above is input to the controller to control the throttle amount of the variable throttle mechanism.

The power steering apparatus of the present invention having such a configuration variably operates the variable throttle mechanism provided on the upstream side of the bypass passage so that the throttle is strengthened at a low speed of the vehicle and the flow rate supplied to the hydraulic control mechanism is increased. Is increased to increase the pressure of the working chamber in the cylinder to increase the assisting force, and the pressure downstream of the variable throttle mechanism is decreased to reduce the pressure of the hydraulic reaction mechanism to reduce the reaction force. Further, when the vehicle is running at high speed, the throttle of the variable throttle mechanism is weakened to increase the bypass flow rate to reduce the flow rate in the supply path, thereby suppressing the pressure increase in the supply path and reducing the discharge pressure. Measure and reduce the load on the pump to eliminate energy loss. Further, as the bypass flow rate increases, a higher pressure is introduced into the hydraulic reaction force mechanism by the action of the downstream throttle mechanism, the steering reaction force increases, and the steering becomes stable. Further, in addition to such a vehicle speed sensor, a hydraulic pressure sensor for detecting the hydraulic pressure in the bypass passage between the two throttle mechanisms is attached to detect the hydraulic pressure that changes due to a change in the oil temperature or steering even at the same vehicle speed. By inputting this signal to the controller, the diaphragm amount of the variable diaphragm mechanism is corrected. That is, there is a predetermined correlation between the hydraulic pressure and the viscosity of the hydraulic oil, and the viscosity and the oil temperature, and the pump discharge pressure fluctuates when the steered wheels are rotated. Therefore, these are corrected.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A is a sectional view showing a first embodiment of a power steering apparatus according to the present invention, and FIG. 2 is a sectional view taken along line II-II in FIG. 1A.

As shown in FIGS. 1A and 2, the inside of the cylinder 2 is separated by a piston 1 into two working chambers 3 and 4, and the piston 1 is a sector shift 40 which is a steering member for driving a steering link. Are linked to. A housing 5 for sealing one end of the cylinder 2 is provided with a supply hole 6 and a discharge hole 7 for supplying and discharging the hydraulic oil discharged from the pump P to and from the two working chambers 3, 4. A worm shaft 8 which is an output member for driving a sector shaft 40 that applies a steering force to the wheels is rotatably accommodated in a bearing 5 through a bearing 9. One end of the worm shaft 8 is screwed onto the piston 1 via a ball screw 41. Also, on the other end side of this worm shaft 8,
A stub shaft 29, which is an input member connected to the steered wheels 43, is connected via a torsion bar 42 having a twistability. Further, on the other end side of the worm shaft 8, there is provided a hydraulic control mechanism 10 for selectively supplying / discharging hydraulic oil to / from the two working chambers 3 and 4 to assist the steering operation of the sector shaft 40. I'm running. This hydraulic control mechanism 10 has a first
As shown in FIG. A, it comprises a cylindrical valve accommodating portion 11 having a predetermined annular groove on its inner peripheral surface, and a spool valve 12 slidably fitted in the valve accommodating portion 11. , The valve housing
Three valve chambers 1 are provided inside 11 by means of four lands formed on the outer circumference of the spool valve 12 at predetermined intervals in the axial direction.
3, 14, 15 are formed. Among these, the valve chambers 13 and 14 located on both sides communicate with the annular groove 5a formed between the housing 5 and the worm shaft 8 via the supplies 16 and 17. Of these, the valve chamber 13 communicates with one of the working chambers 3 through an oil passage 18, and the valve chamber 14 has
It communicates with the other working chamber 4 via an oil passage 19. Also,
Of the valves 13, 14 and 15, the valve chamber 15 located at the center is
The spool valve 12 is communicated with the discharge hole 7 via an oil passage 44, and the spool valve 12 is driven by one stub shaft pin 30a provided on the stub shaft 29 to slide in the valve housing portion 11 in the axial direction. At this time, the area of the fluid passage from the valve chamber 13 or the valve chamber 14 to the valve chamber 15 increases or decreases, and at the same time, the area of the fluid passage from the supply ports 16 and 17 to the valve chambers 13 and 14 corresponding thereto decreases. Or it is increasing.

On the other hand, on the other end side of the worm shaft 8, as shown in FIG. 1A, the hydraulic reaction mechanism 20 is opposed to the hydraulic control mechanism 10.
Is provided. The hydraulic reaction force mechanism 20 includes a control cylinder 21 fixed to the worm shaft 8 and a cylinder 21
Of the sealing plates 22 and 22 for closing the openings of both ends of the two pistons, and two pistons 23 and 24 slidably fitted in the control cylinder 21.
And reaction chambers 31 and 32 formed between the pistons 23 and 24 and the sealing plates 22 and 22, and the stub shaft 29.
Stub shaft pin 30a, which is similarly planted at a diametrically opposite position of the stub shaft pin 30a that drives the hydraulic control mechanism 10, and faces between the pistons 23 and 24.
30b and the stub shaft pin 30b with the piston 23,
Set springs 25 and 26 for constantly urging 24, and stop rings 27 and 28 mounted on the inner circumference of the cylinder 21 for restricting movement of the pistons 23 and 24 toward each other. ing.

The reaction force chambers 31 and 32 communicate with an oil passage 38 through through holes 33 and 34 that open and an annular oil passage 37 that is formed between the worm shaft 8 and the housing 5. The stub shaft insertion chamber 45 formed between the two pistons 23, 24 communicates with the hydraulic oil discharge hole 7 via an oil passage 46.

Further, the pump P and the two working chambers 3 and 4 are connected by a supply path 47, and the hydraulic control mechanism 10 is provided in the middle of the supply path 47 so that the hydraulic oil discharged from the pump P is It is adapted to be switched and fed to the working chambers 3 and 4. A bypass line 49 for returning hydraulic oil from the supply line 47 to the tank T.
In the middle of this bypass path 49, on the upstream side, a variable throttle mechanism 50 that changes the opening area of the bypass path 49 according to the vehicle speed, and on the downstream side, a fixed throttle with a constant opening area. Mechanisms 51 and are respectively provided. From a bypass passage 49 between the variable throttle mechanism 50 and the fixed throttle mechanism 51, a branch passage 52 communicating with an oil passage 38 provided in the housing 5 is provided.
Is provided. Thus, the fixed throttle mechanism 51 and the variable throttle mechanism 50 are provided in the reaction force chambers 31 and 32 of the hydraulic reaction force mechanism 20.
A hydraulic pressure generated between the hydraulic pressure and the pressure is introduced, and the stub shaft pin 30b receives a reaction force according to the hydraulic pressure. Reference numeral 48 is a discharge passage for returning the hydraulic oil to the tank T, and the hydraulic control mechanism 10 and the hydraulic reaction mechanism are provided from the pump P through the supply passage 47.
The hydraulic oil sent to the tank 20 is recirculated to the tank T from these, and the hydraulic oil discharged from any of the working chambers 3 and 4 of the cylinder 2 is also sent to the tank T via the hydraulic control mechanism.
Reflux to. Further, a hydraulic pressure sensor 56 for detecting the hydraulic pressure of hydraulic oil is provided in the branch passage 52, and a hydraulic pressure signal obtained from this hydraulic pressure sensor 56 is inputted to the electronic controller 55. On the other hand, each signal obtained from the vehicle speed sensor 53 and the steering wheel load select switch 54 is input to the electronic controller 55.
The signal from 6 is input and the control signal is output to the solenoid 50a that constitutes the variable aperture mechanism 50.

Next, the operation of the power steering system according to this embodiment having such a configuration will be described.

First, the case where the vehicle is traveling at a low speed will be described.

In this case, the vehicle speed sensor 53 detects a low-speed traveling state, and the controller 55 operates the solenoid 50a in response to the vehicle speed signal to increase the throttle amount of the variable throttle valve 50b constituting the variable throttle mechanism 50 (passage area). The amount of hydraulic oil discharged toward the tank T through the bypass passage 49 is reduced. Then, in the supply path 47, the loss of the flow rate is small, and a high pressure acts on either one of the working chambers 3 or 4 in the cylinder 2 through the hydraulic control mechanism 10 to obtain a large steering assisting force. On the other hand, since the hydraulic pressure generated between the variable throttle mechanism 50 and the fixed throttle mechanism 51 is small, each of the insides of the control cylinder 21 from the branch passage 52 through the oil passage 38, the annular oil passage 37 and the through holes 33, 34. The pressure of the hydraulic oil introduced into the reaction force chambers 31, 32 is small, and the steering reaction force is small. Thus, the steering wheel 43 can be operated with a small force at low speed.

Next, a case where the vehicle shifts from the low speed traveling state to the high speed traveling state will be described.

In this case, the vehicle speed sensor 53 detects that the vehicle has traveled from the low-speed traveling state to the high-speed traveling state, and the controller 55 activates the solenoid 50a in response to the vehicle speed signal corresponding thereto, and the throttle amount of the variable throttle valve 50b is reduced. The amount of hydraulic oil discharged toward the tank T through the bypass path 49 is increased, and the flow rate is regulated mainly by the fixed throttle mechanism 51 on the downstream side.

Then, the flow rate in the supply path 47 decreases, and the hydraulic control mechanism 10
The flow resistance in the inside is reduced, the rise in the pressure in the supply passage 47 is suppressed, and a large rise in the pump discharge pressure is prevented. Thus, the pump P does not do extra work and energy loss is small. On the other hand, since the hydraulic pressure generated on the upstream side of the fixed throttle mechanism 51 is close to the hydraulic pressure of the supply passage 47, the pressure of the hydraulic oil introduced from the branch passage 52 into the reaction force chambers 31, 32 becomes relatively large, and the steering The reaction force becomes great. Thus, at high speed, the operation of the steered wheels 43 becomes moderately heavy, and the steering becomes stable.

On the other hand, the hydraulic pressure sensor 56 constantly detects the fluctuation of the hydraulic pressure in the branch path 52, inputs the hydraulic pressure signal to the electronic controller 55, and outputs the control signal to the solenoid 50a of the variable throttle mechanism 50 based on the vehicle speed signal from the vehicle speed sensor 53. Correcting.

That is, the temperature of the hydraulic oil is low when the vehicle is started, and rises as time passes. It is low in winter and high in summer. Thus, the oil temperature is not always constant but changes. Further, the viscosity of the hydraulic oil changes as the oil temperature changes, and the lower the oil temperature, the higher the viscosity. As the viscosity of the hydraulic oil increases, the flow resistance increases, and the pressure difference before and after the orifice increases. Therefore, the pressure in the branch passage 52 also increases as the flow resistance in the fixed throttle mechanism 51 increases. On the other hand, the steering wheel 43
When you rotate, the back pressure is applied to the supply line 47,
The pressure in 47 rises. Therefore, the pressure in the branch path 52 also increases.

As described above, the pressure in the branch path 52 changes depending on the passage of time from the start and the season even at the same vehicle speed, and also changes due to the rotation operation of the steered wheels 43. Since the hydraulic pressure introduced to the vehicle also changes, by inputting the signal of the hydraulic sensor 56 in addition to the signal from the vehicle speed sensor 53 to the electronic controller 55, the reaction force chambers 31 and 32 are adjusted to the hydraulic pressure suitable for the vehicle speed. A signal is output to the solenoid 50a of the variable throttle mechanism 50 so as to control the opening of the variable throttle valve 50b.

FIG. 1B is a sectional view showing a second embodiment of the power steering apparatus according to the present invention.

The embodiment shown in FIG. 1B is different from the first embodiment in that the downstream throttling mechanism of the two throttling mechanisms provided in the bypass path 49 is also the variable throttling mechanism 57, and the control of this is performed. Similarly to the variable throttle mechanism 50 on the upstream side, the vehicle speed sensor 53
This is performed by the output of the electronic controller 55 in response to inputs from the steering wheel load select switch 54 and the hydraulic pressure sensor 56.

In these embodiments, the case where the present invention is applied to the power steering device of the recirculation rating type using the worm shaft 8 as the output member has been described. For example, the pinion shaft is used as the output member. It was lucky. and. The present invention may be applied to a pinion type power steering device.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, the supply passage for the hydraulic oil from the pump to the working chamber and the bypass passage for returning to the tank from the middle of the supply passage are provided. Is provided with two throttle mechanisms, at least the upstream throttle mechanism is a variable throttle mechanism that changes the opening area of the bypass passage, and an oil passage branched from the bypass passage between these two throttle mechanisms is provided. While communicating with the hydraulic reaction mechanism, a controller for controlling the throttle amount of the variable throttle mechanism and a vehicle speed sensor for inputting a vehicle speed signal detected by the controller are provided.
An oil pressure sensor for detecting the oil pressure in the bypass passage between the two throttle mechanisms is attached, and the vehicle speed signal obtained from the vehicle speed sensor and the oil pressure signal obtained from the oil pressure sensor are input to the controller to adjust the throttle amount of the variable throttle mechanism. Since the control is performed, when the vehicle is running at low speed, the variable throttle mechanism on the upstream side is greatly throttled to increase the pressure to the working chamber and reduce the pressure to the reaction force chamber to provide effective steering assistance. If possible, when the vehicle is running at high speed, the throttle of the variable throttle mechanism on the upstream side is loosened to increase the flow rate of the bypass passage, and the flow rate of the bypass passage is mainly throttled by the throttle mechanism on the downstream side to reduce the reaction force chamber. A relatively high pressure is introduced to increase the steering reaction force, which stabilizes the steering, loosens the variable throttle mechanism, and increases the flow rate in the bypass path.
The flow rate in the supply path decreases, which suppresses the rise in pressure in the supply path to reduce the load on the pump and eliminates the loss of energy. Since a hydraulic pressure sensor that detects the hydraulic pressure in the road is provided and a correction signal for controlling the throttle amount of the variable throttle mechanism is input to the electronic controller, changes in the oil temperature of the hydraulic oil and rotational operation of the steered wheels are performed. There is an advantage that the variation of the pressure caused by is corrected, the throttle amount of the variable throttle mechanism is corrected, and the steering reaction force that always matches the vehicle speed is realized to provide the driver with a preferable steering feeling.

[Brief description of drawings]

FIG. 1A is a vertical sectional view including a block diagram showing a first embodiment of a power steering apparatus according to the present invention, FIG. 1B is a similar vertical sectional view showing a second embodiment, and FIG. It is a cross-sectional view showing a power steering device. 1 ... Piston, 2 ... Cylinder, 3, 4 ... Working chamber,
8 …… Worm shaft (output member), 10 …… Hydraulic control mechanism, 12 …… Spool valve, 20 …… Hydraulic reaction mechanism, 29 ……
Stub shaft (input member), 40 …… Sector shaft (steering member), 43 …… Steering wheel, 47 …… Supply path, 48 …… Discharge path, 49 …… Bypass path, 50 …… (Upstream side) variable Throttle mechanism, 51 ... (downstream side) fixed throttle mechanism, 56 ... hydraulic sensor, 57 ... (downstream side) variable throttle mechanism, P ... pump.

Claims (1)

[Claims] 1. An input member driven by an operation force of a steered wheel, an output member driving a steering member for applying a steering force to a wheel, and a relative rotational displacement between the input member and the output member. At this time, with a hydraulic control mechanism for selectively supplying and discharging hydraulic oil to and from two working chambers in a cylinder separated by a piston to assist the steering operation of a steering member connected to the piston, In a power steering apparatus including a hydraulic reaction force mechanism that applies a reaction force when the hydraulic control mechanism moves in accordance with a vehicle speed, a hydraulic fluid discharged from a pump is supplied from a supply passage for feeding the hydraulic oil to the two working chambers. A bypass path for branching and returning the hydraulic oil to the tank is provided, two throttle mechanisms are provided in the middle of the bypass path, and at least the upstream throttle mechanism is a variable throttle that changes the opening area of the bypass path. With a mechanism, it provided an oil passage branched from the bypass passage between these two diaphragm mechanism,
A controller for controlling the throttle amount of the variable throttle mechanism and a vehicle speed sensor for inputting a vehicle speed signal detected by the controller are provided while communicating with the hydraulic reaction mechanism, and a bypass path between the two throttle mechanisms is provided. A hydraulic pressure sensor for detecting the internal hydraulic pressure is attached, and a vehicle speed signal obtained from the vehicle speed sensor and a hydraulic pressure signal obtained from the hydraulic pressure sensor are input to the controller to control the throttle amount of the variable throttle mechanism. Power steering device to do.