JPH0321388B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device for a motor vehicle, and particularly to an improvement of a reaction force chamber type device.

In general, automobile power steering devices are
A power cylinder having a piston and pressure chambers on both sides of the piston interlocking with the steering shaft; a main pump driven by an engine and supplying pressure oil to each pressure chamber on both sides of the piston of the power cylinder; The vehicle is equipped with a switching valve that switches the pressure oil supply to each pressure chamber of the power cylinder in opposite directions according to a reaction force against the steering force (steering resistance from the road surface), and the switching valve is operated to switch according to the steering direction. By supplying pressure oil to one pressure chamber of the power cylinder, an assist force is applied to the steering force to reduce the steering force.

However, with this type of power steering device,
If the initial set load of the switching valve (minimum load for switching the switching valve) is set to a constant small value for when the car is running at low speeds, it will be effective against light steering force when the car is running at high speeds. However, the switching valve will respond and assist force will be applied, and as a result, there is a risk that the high-speed stability of the vehicle will be impaired.

Therefore, in order to solve this problem, conventionally, as disclosed in Japanese Patent Publication No. 54-9769, etc., there has been a countermeasure that uses hydraulic pressure to restrict the movement of the valve body within the housing of the above-mentioned switching valve. A force chamber is formed, and pressurized oil is supplied to the reaction force chamber from a control pump driven by the output shaft of a transmission whose rotation changes in proportion to the vehicle speed, thereby adjusting the initial set load of the switching valve to the vehicle speed. By increasing or decreasing accordingly,
A so-called reaction chamber type has been proposed in which the initial operating set load of the switching valve is increased to ensure running stability when the vehicle is running at high speed.

However, in this proposal, the main pump is directly connected to the engine for driving, so the pressure oil discharge amount of the main pump changes depending on the engine rotation speed, that is, the vehicle speed, and the engine's high rotation range (high speed In the driving range), the amount of pressurized oil discharged far exceeds the minimum required to provide assist force, and as a result, unnecessary pumping action occurs, resulting in a large energy loss in the engine.

In view of this, the present invention connects the above-mentioned control pump to an electric motor whose rotational torque changes depending on the vehicle speed, and uses hydraulic pressure from the control pump to control the rotation between the engine and the main pump. By changing the transmission ratio, the amount of pressure oil discharged from the main pump can be kept approximately constant regardless of changes in vehicle speed (engine speed), and unnecessary pumping action can be suppressed. The purpose of this is to reduce energy loss.

In order to achieve this object, the configuration of the present invention includes a power cylinder having a piston interlocked with a steering shaft and pressure chambers on both sides of the piston, and a power cylinder driven by an engine via a variable pulley mechanism, and a power cylinder having pressure chambers on both sides of the piston of the power cylinder. a main pump that supplies pressure oil to each pressure chamber,
A switching valve that switches the supply of pressure oil to each pressure chamber of the power cylinder by a reaction force against the steering force of the steering shaft; and supplying pressure oil to the switching valve to control the initial operating set load of the switching valve; A control pump that controls the pulley ratio of the variable pulley mechanism by supplying pressure oil to a pulley ratio control device of the variable pulley mechanism, an electric motor that drives the control pump, a vehicle speed sensor that detects vehicle speed, and a control pump that controls the pulley ratio of the variable pulley mechanism. and a controller that controls the rotational torque of the electric motor according to the output, thereby keeping the pressure oil discharge amount of the main pump substantially constant regardless of changes in vehicle speed and suppressing unnecessary pumping action. This is how it was done.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

1 and 2 show an example applied to a rack and pinion type steering device, in which 1 is a handle, 2 is the handle 1 at one end, and a pinion shaft 3 having a pinion 3a at the other end is integrally attached. The steering shaft 4 is a rack bar having a rack (not shown) that meshes with the pinion 3a, and left and right front wheels 6, 6 are connected to both ends of the rack bar 4 via knuckle arms 5, 5, respectively. By turning the handle 1, the rack bar 4 is moved in the left-right direction to give a steering angle to the front wheels 6, 6.

A power cylinder 7 is disposed at an intermediate position on the rack bar 4, and the power cylinder 7 is slidably inserted through the rack bar 4 as a piston rod. It has left and right pressure chambers 9 and 10 located on both sides of the piston 8. That is, the piston 8 is provided so as to interlock with the steering shaft 2.

The pressure chambers 9 and 10 on both sides of the piston 8 of the power cylinder 7 are connected to a switching valve 24, which will be described later, via pressure oil passages 11 and 12, respectively. It is connected to the discharge side of the pump 14 and to a reservoir 16 via a pressure oil return passage 15, and the reservoir 16 and the suction side of the main pump 14 are connected by a connection passage 17. The pressure oil discharged from 14 is transferred to the pressure oil supply passage 13, the switching valve 24 and the pressure oil passages 11 and 1.
One pressure chamber 9 of the power cylinder 7 via 2,
10 and the other pressure chamber 10, 9
The pressure oil inside is transferred to the pressure oil passages 12, 11 and the switching valve 24.
and the reservoir 1 via the pressure oil return passage 15.
6, thereby pushing the piston 8 in the power cylinder 7 and applying assist force to the steering force of the steering shaft 2 (handle 1).

The main pump 14 is drivingly connected to the vehicle engine 23 via a variable pulley mechanism 18. The variable pulley mechanism 18 is the engine 23
The drive pulley 19 attached to the output shaft 23a of
, a driven pulley 20 attached to the rotating shaft 14a of the main pump 14, a V-belt 21 stretched between both pulleys 19, 20, and both pulleys 19,
Pulley ratio control device 2 that controls the pulley ratio between 20
2. The drive pulley 19 includes a fixed sheave 19a fixed to the output shaft 23a of the engine 23, a movable sheave 19b slidably but non-rotatably supported on the output shaft 23a, and a pulley of the drive pulley 19 that connects the movable sheave 19b. It consists of a spring 19c that urges the fixed sheave 19a to increase its diameter. In addition, the driven pulley 20
is a fixed shaft 20a fixed to the rotating shaft 14a of the main pump 14, similar to the drive pulley 19.
a movable sheave 20b that is slidably but non-rotatably supported on the rotating shaft 14a, and a spring 20c that biases the movable sheave 20b in a direction away from the fixed sheave 20a so that the pulley diameter of the driven pulley 20 decreases. It consists of Further, the pulley ratio control device 22 has a pressure oil introduction chamber 22a on the back side of the movable sheave 20b of the driven pulley 20, which is hermetically formed by the sheave 20b and a flange portion 14b integral with the pump casing. When the pressure oil in the pressure oil introduction chamber 22a is low, the pulley diameter of the drive pulley 19 is made larger than the pulley diameter of the driven pulley 20 by the biasing force of the springs 19c and 20c of the respective pulleys 19 and 20, thereby increasing the pulley ratio. On the other hand, when the pressure oil pressure in the pressure oil introduction chamber 22a is high, the pulley diameter of the drive pulley 19 is made smaller than the pulley diameter of the driven pulley 20 against the urging force of the springs 19c and 20c to increase the pulley ratio. It operates like this.

On the other hand, 24 is a switching valve consisting of a 4-port 3-position spool valve disposed near the pinion shaft 3 so as to be orthogonal to the pinion shaft 3,
The switching valve 24 includes a housing 25 integrally formed with the casing 3b of the pinion shaft 3, and a valve body 26 that slides within the housing 25 in a direction perpendicular to the pinion shaft 3. On one side of the housing 26 is a pressure port 27 communicating with the pressure oil supply passage 13, and on both sides of the pressure port 27 are first and second ports 28 communicating with the pressure oil passages 11 and 12, respectively. 29, and a return port 30 which communicates with the pressure oil return passage 15 is provided on the side of the first port 28. On the other hand, the housing 2 is attached to the valve body 26.
5, there is a communication path 31 that communicates the second port 29 with the return port 30 when the first port 28 communicates with the pressure port 27, and a communication path 31 that communicates with the return port 30 when the first port 28 communicates with the pressure port 27; A through hole 32 extending in the direction toward the pinion shaft 3 is formed in a portion close to the pinion shaft 3, and one end arm portion 33a of a pinion holder 33 externally supported rotatably on the pinion shaft 3 is engaged with the through hole 32. , the other end arm portion 33b of the pinion holder 33 is locked to the casing 3b of the pinion shaft 3, and the pinion shaft 3
That is, when the steering shaft 2 rotates due to steering, the rack bar 4 responds to the steering force.
The pinion holder 33 swings around the locking position of the other end arm portion 33b to the casing 3b due to the reaction force from the pinion holder 33, and slides the valve body 26 by a predetermined stroke amount (for example, about 1 mm). By sliding, the supply of pressure oil from the main pump 14 to each pressure chamber 9, 10 of the power cylinder 7 is switched, and when the valve body 26 moves to the left in FIG. Through communication between the communication and return port 30 and the second port 29, pressure oil is supplied to the pressure chamber 9 on the left side, and pressure oil in the pressure chamber 10 on the right side is returned to the reservoir 16. When moving to the right side of the figure, pressure oil is supplied to the pressure chamber 10 on the right side through communication between the pressure port 27 and the second port 29 and communication between the return port 30 and the first port 28, and the pressure inside the pressure chamber 9 on the left side is It operates to return oil to the reservoir 16.

Further, on the other side of the valve body 26, there is a first spring receiving plate 34 whose movement in the right direction in FIG. A second spring receiving plate 36 whose movement to the left in FIG. 2 is regulated by a clip 35 that is engaged with the valve body 26 at a predetermined distance away from the plate 34 to the left (end side) A reaction force chamber 37 is formed in the housing 25 between the spring receiving plates 34 and 36 so as to be slidable, and a reaction force chamber 37 is formed in the reaction force chamber 37 to separate the spring receiving plates 34 and 36 from each other. A spring 38 is disposed to bias the valve body 26 in the direction, and the valve body 26 is moved only when a reaction force greater than the spring force of the spring 38 is applied from the rack bar 4 to the valve body 26.
That is, it is configured to set the initial operating set load of the switching valve 24.

Furthermore, the reaction chamber 37 of the switching valve 24 is communicated with the discharge side of the control pump 40 via a pressure oil supply passage 39, and a midway portion of the pressure oil supply passage 39 is connected to a pressure oil return passage 41 having an orifice 41a.
The reservoir 16 and the suction side of the control pump 40 are connected through a connecting passage 4.
2, and by supplying pressure oil from the control pump 40 to the reaction force chamber 37 to increase or decrease the pressure in the reaction force chamber 37, the switching valve 24
The initial operating set load is controlled to increase above the value corresponding to the spring force of the spring 38, and when the pressure in the reaction force chamber 37 is low, the initial operating set load is lowered, and when the pressure is high, the initial operating set load is increased. It is designed to increase the

Further, an intermediate portion of the pressure oil supply passage 39 connected to the control pump 40 is also connected to the pressure oil introduction chamber 22a of the pulley ratio control device 22 of the variable pulley mechanism 18 via an auxiliary pressure oil supply passage 43. Ori,
It is configured to control the pulley ratio of both pulleys 19 and 20 in the variable pulley mechanism 18 by supplying pressure oil of the same pressure as the pressure oil to the switching valve 24 from the control pump 40 to the pressure oil introduction chamber 22a. has been done.

The control pump 40 is drivingly connected to an electric motor 44 whose rotational torque (rotation speed) varies according to changes in input voltage. The electric motor 44 is connected to the vehicle battery 4 via a controller 45.
6, and the output of a vehicle speed sensor 47 for detecting vehicle speed is input to the controller 45. Accordingly, the controller 45 operates to increase or decrease the rotational torque of the electric motor 44, that is, the pressure oil discharge amount of the control pump 40 drivingly connected to the electric motor 44, in accordance with the output of the vehicle speed sensor 47.
As shown in FIG. 3, the pressure oil discharge amount of the control pump 40 is configured to correspond to the square root value of the vehicle speed as the vehicle speed increases. In addition, in Figure 2, 48
The orifices 41 of the pressure oil supply passage 39 and the pressure oil return passage 41 are configured to regulate the maximum pressure value of the pressure oil supplied from the control pump 40 to the switching valve 24 and the pulley ratio control device 22 of the variable pulley mechanism 18.
A is a relief valve interposed between the downstream side and the downstream side.

Next, the operation of the above embodiment will be explained.
When the engine 23 is stopped, the drive pulley 19 of the variable pulley mechanism 18 is maintained at its maximum pulley diameter by the biasing force of the spring 19c, and the driven pulley 20 is maintained at its minimum pulley diameter by the biasing force of the spring 20c. The pulley ratios of pulleys 19 and 20 are at a minimum value.

When the engine 23 is started in this state, from the start to the idling state, that is, when the vehicle is stopped, the vehicle speed sensor 47 and the controller 45 are inactivated to drive the electric motor 44 and the control that is drive-coupled to the motor 44. pump 40
does not operate, and as a result, the variable pulley mechanism 1
The pulley ratio control device 22 of No. 8 is kept in an inoperative state, so that the pulley ratio between the driving pulley 19 and the driven pulley 20 does not change, and as shown in the left part of FIG. The amount of pressure oil is discharged. Further, the oil pressure in the reaction force chamber 37 of the switching valve 24 becomes zero, and the switching valve 24
The initial set load of the spring 38 is the minimum value corresponding to the spring 38. As a result, even if a light steering force is applied to the steering shaft 2 (handle 1), the switching valve 24 is actuated in response, and pressure oil from the main pump 14 is supplied to one pressure chamber 9, 10 of the power cylinder 7. Therefore, the assist force acts on the steering force and the power steering function is exerted.

On the other hand, when the automobile shifts to a running state, the vehicle speed is detected by the vehicle speed sensor 47, and the controller 45 is actuated by the detection signal from the vehicle speed sensor 47, and the electric motor 44 and the control pump 40 are operated.
is operated so that the amount of pressure oil discharged from the control pump 40 increases in accordance with the square root of the vehicle speed, as shown in FIG. When pressure oil is discharged from the control pump 40 in accordance with the parallel root value of the vehicle speed, the pressure in the reaction chamber 37 of the switching valve 24 (control pump 4
The discharge pressure (0 discharge pressure) increases in proportion to the vehicle speed as shown in FIG. 4 due to passage resistance at the orifice 41a of the pressure oil return passage 41. The set load increases in proportion to the increase in vehicle speed. Further, the pressure oil from the control pump 40 is supplied to an auxiliary pressure oil supply passage 43.
The switching valve 24 is also connected to the pressure oil introduction chamber 22a of the pulley ratio control device 22 of the variable pulley mechanism 18 via the
This hydraulic pressure operates the pulley ratio control device 22 to increase the pulley diameter of the driven pulley 20 against the biasing force of the spring 20c, and the drive pulley 1
The diameter of pulley 9 is made smaller against the biasing force of spring 19c, and the pulley ratio of both pulleys 19 and 20 is increased. At that time, as the vehicle speed increases, the engine speed increases over a certain range depending on the gear position in the transmission, but the pulley ratio increases to offset the increase in engine speed, causing the main The rotational speed of the pump 14 decreases relative to the engine rotational speed, and the amount of pressure oil discharged from the main pump 14 is kept substantially constant regardless of changes in vehicle speed, as shown in the right side of FIG. From the above,
When the vehicle speed is low, the switching valve 24 operates in response to light steering force, and constant pressure oil from the main pump 14 is supplied to the pressure chambers 9 and 10 on one side of the power cylinder 7, thereby exerting the power steering function. On the other hand, when the vehicle speed increases, the switching valve 24 does not operate in response to a light steering force, suppressing the power steering function and improving the running stability of the vehicle.

Therefore, when the vehicle is running, the pulley ratio of both pulleys 19 and 20 of the variable pulley mechanism 18 is increased in response to an increase in the vehicle speed (engine rotation speed) to increase the rotation speed of the main pump 14, that is, the pressure oil discharge. Since the amount is kept approximately constant as shown by the solid line in FIG. 5, unnecessary pumping action in the main pump 14 is suppressed compared to the conventional example shown by the broken line in FIG. 5, thereby reducing energy loss in the engine 23. be able to.

In the above embodiment, the pulley ratio control device 22 of the variable pulley mechanism 18 is provided on the driven pulley 20 side (main pump 14 side), but it may be changed to the drive pulley 19 side (engine 23 side). Needless to say.

Further, in the above embodiment, an example was explained in which the present invention was applied to a rack and pinion type steering device, but it goes without saying that the present invention can be applied to various other types of steering devices such as a worm pin type and a ball screw type. That's true.

As explained above, according to the present invention, in a reaction chamber type power steering device for an automobile, the engine and the main pump are drivingly connected by a variable pulley mechanism, and the switching valve for controlling the power cylinder switching is connected. A control pump for controlling the initial operating load is drive-connected to an electric motor whose rotating torque changes depending on the vehicle speed, and pressurized oil from the control pump is supplied to the pulley ratio control device of the variable pulley mechanism to control the engine. By changing the rotational speed transmission ratio between the main pump and the main pump according to the vehicle speed, the main pump's pressure oil output can be kept almost constant regardless of changes in vehicle speed, eliminating the need for the main pump. It is possible to suppress the pumping action and reduce the energy loss of the engine.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall schematic explanatory diagram, FIG. 2 is an enlarged explanatory diagram of main parts, and FIG. 3 is an explanatory diagram showing the relationship between vehicle speed and pressure oil discharge amount of a control pump. FIG. 4 is an explanatory diagram showing the relationship between the vehicle speed and the reaction force chamber pressure of the switching valve, and FIG. 5 is an explanatory diagram showing the relationship between the engine speed, the vehicle speed, and the pressure oil discharge amount of the main pump. 2... Steering shaft, 3... Pinion shaft, 4... Rack bar, 7... Power cylinder,
8... Piston, 9, 10... Pressure chamber, 14...
Main pump, 18... Variable pulley mechanism, 19...
... Drive pulley, 20 ... Driven pulley, 22 ... Pulley ratio control device, 23 ... Engine, 24 ... Switching valve, 25 ... Housing, 26 ... Valve body,
33...Pinion holder, 37...Reaction force chamber, 38
... Spring, 40 ... Control pump, 41 ...
Pressure oil return passage, 41a...orifice, 44
...Electric motor, 45...Controller, 47...
...Vehicle speed sensor.

Claims (1)

[Claims] 1 A power cylinder that has a piston that interlocks with the steering shaft and pressure chambers on both sides of the piston, and a main that is driven by the engine via a variable pulley mechanism and supplies pressure oil to each pressure chamber on both sides of the piston of the power cylinder. A pump, a switching valve that switches the supply of pressure oil to each pressure chamber of the power cylinder by a reaction force against the dry steering force of the steering shaft, and controlling the initial set load for operation of the switching valve by supplying pressure oil to the switching valve. and a control pump that controls the pulley ratio of the variable pulley mechanism by supplying pressure oil to the pulley ratio control device of the variable pulley mechanism, an electric motor that drives the control pump, and a vehicle speed sensor that detects vehicle speed. A power steering device for an automobile, comprising: a controller that controls the rotational torque of the electric motor according to the output of the vehicle speed sensor.