JPH062465B2 - Vehicle speed sensitive power steering device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle speed-sensitive power steering apparatus provided with a hydraulic reaction chamber that automatically controls a steering reaction force depending on a vehicle speed and a steering angle. .

[Conventional technology]

Conventionally, a power steering device has been provided with a reaction force device so as to give an appropriate steering feeling to a driver. Generally, the steering resistance is maximum at so-called stationary steering when the vehicle or the like is stopped, and becomes extremely small when the vehicle is traveling at high speed. Therefore, it is almost unnecessary to operate the function of the power steering device at the time of high speed traveling, and therefore, the reaction force device as described above is provided.

Japanese Patent Application No. 59-97447 discloses such a conventional power steering apparatus that controls the reaction force of the hydraulic reaction chamber along with the vehicle speed over the entire steering angle range.

[Problems to be solved by the invention]

However, in the above-described conventional power steering apparatus, the amount of electricity supplied from the controller to the reaction force pressure control valve is determined only by the vehicle speed, and the diagram of FIG. 9 (horizontal axis indicates vehicle speed, vertical axis indicates reaction force solenoid valve solenoid). Current value). As shown in the diagram of FIG. 10 (the horizontal axis is the vehicle speed, the vertical axis is the variable throttle area, that is, the opening area), the throttle area of the reaction force pressure control valve changes depending on the vehicle speed.

Also, because there is piping resistance downstream from the high pressure port of the valve housing to the oil tank,
As shown in the diagram of FIG. 1 (the flow rate through the fixed orifice on the horizontal axis and the power steering pressure on the vertical axis), the back pressure P ₁ is generated. Therefore, regardless of the vehicle speed, the fluid flows through the fixed orifice toward the variable orifice at the flow rate Q ₁ . Even if the steering wheel is not operated as the vehicle speed increases due to the fluid having the flow rate Q ₁ , reaction force pressure existing in the reaction force pressure control valve is generated, and this pressure increases as the speed increases. . Since this pressure is introduced into the hydraulic reaction chamber and becomes the initial pressure and acts on the valve spool of the power cylinder control valve mechanism, the diagram of FIG. 12 (horizontal axis represents steering torque, vertical axis represents power steering pressure). As shown in the diagram of FIG. 13 (the horizontal axis is the steering torque, the vertical axis is the power cylinder output, and MS is the state of manual steering), the vehicle speed (V
Indicate. V ₀ indicates a stop time, and the steering torque increases with an increase in V ₁ <V ₂ <... V _n ) and becomes an initial reaction force, so the steering wheel operation becomes heavy near the steering wheel neutral position,
Further, the steering torque when the steering wheel is steered to a position slightly apart from the vicinity of the neutral position of the steering wheel suddenly changes, which is not preferable for filling. That is, since a pressure similar to manual steering is generated as a characteristic near the neutral position of the steering wheel (indicated by N), a discomfort that is heavy when the steering wheel is turned is generated.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a vehicle speed-sensitive automatic steering device that has a good steering feeling near the neutral position of the steering wheel.

[Means for solving problems]

For this purpose, the present invention provides a vehicle speed sensor for detecting a vehicle speed, a steering angle sensor for detecting a steering angle, a valve for switching a supply direction of pressure oil discharged from a pump to a power cylinder, and a valve for suppressing movement of the valve. A power cylinder control valve mechanism having a force chamber, and a reaction force pressure control valve having a variable orifice arranged in the flow path from the reaction chamber to the oil tank and controlling the reaction pressure to the reaction chamber. Fixed in a flow path connecting the pump and the power cylinder, communicating with the reaction force chamber and diverting a part of the discharge flow rate from the pump supplied to the power cylinder to the reaction force pressure control valve side The reaction force pressure control valve is provided with an orifice, and based on the information of the vehicle speed sensor and the steering angle sensor, when the vehicle is traveling, the steering angle is set only in the vicinity of the steering wheel neutral position according to each vehicle speed. It exists to so as to reduce the variable throttle area of the orifice, which is constituted as a constant variable throttle area which is set by the vehicle speed in the steering angle of rest.

[Action]

According to the above configuration, the opening area of the variable orifice of the reaction force pressure control valve in the vicinity of the steering wheel neutral position can be changed from a state equivalent to the opening area at low speed, and even if the vehicle speed increases, the opening area near the steering wheel neutral position can be changed. Then, the reaction force pressure does not increase.

〔Example〕

Hereinafter, the present invention will be described based on embodiments shown in the drawings. FIG. 1 is a block diagram of a vehicle speed-sensitive power steering apparatus according to the present invention,
FIG. 2 is a circuit diagram showing a cross section of a part of the vehicle speed sensitive power steering apparatus.

A vehicle speed-sensitive power steering apparatus according to the present invention includes a valve spool 30 that moves by steering of a steering shaft 11 to switch a pressure oil supply direction to a power cylinder 12, and a valve spool 3.
0 power cylinder control valve mechanism 20 including hydraulic reaction force chambers 50 formed at both ends and supplied with pressure oil from pump 80 to suppress movement of valve spool 30, and reaction force chamber 5
The reaction force control valve 70 is installed in the flow path from 0 to the oil tank 82 and controls the pressure in the reaction force chamber 50 by a signal from the controller 84.

The steering wheel 13 of the vehicle is connected to the pinion shaft 22 via the steering shaft 11, and a pinion (not shown) is fixed to the pinion shaft 22. A rack (not shown) that meshes with the pinion extends perpendicularly to the pinion shaft 22, and this rack is connected to the piston 12A in the power cylinder 12. The piston 12A is connected to the tie rod 15 of the wheel 14, and the wheel 14 is steered by sliding the rack through the pinion shaft 22 by operating the handle.

A pinion shaft 22 is provided so as to penetrate through the valve housing 24. The pinion shaft 2 is provided in the valve housing 24.
A spool insertion hole 32 is formed in a direction orthogonal to 2, and the valve spool 30 is slidably disposed in the spool insertion hole 32. The valve spool 30 is formed with a pin hole 34 penetrating vertically, and the pin hole 34 and the pinion shaft 22 are connected by a swing lever 28. The swing lever 28 is swingable around the lower end fulcrum 29 in the left-right direction (FIG. 2).
The swing of the valve spool 30 allows the valve spool 30 to slide in the left-right direction. A pump port (not shown), cylinder ports 35 and 36, and a tank port 37, which sandwich the pump port, are provided on the inner peripheral surface of the spool insertion hole 32, and a high-pressure fluid is supplied from a pump 80 to the pump port. Oil tank 82 from the tank port 37.
The fluid is designed to be discharged.

On the other hand, an annular groove 38 is formed on the outer peripheral surface of the valve spool 30 at a position facing the pump port 39, and the high pressure oil allows the high pressure oil to pass through the annular groove 38.
Is selectively supplied to the power cylinder 12, so that the power cylinder 12 is operated.

A reaction force chamber 50 (50A, 50A,
50B) is formed, and extends in parallel with the spool insertion hole 32 in the valve housing 24 so that both reaction force chambers 50A and 50B are formed.
A communication passage 40 that communicates with each other is formed. An opening passage 42 that faces the annular groove 38 of the valve spool 30 is formed in the communication passage 40.
Both reaction force chambers 50A, 5 via the opening passage 42 and the communication passage 40.
Pressure oil is supplied to the inside of 0B. A fixed orifice 43 is provided in the opening passage 42 so that the pressure in the reaction force chamber 50 can be controlled to zero, and the pressure in the power cylinder 12 is influenced by the pressure in the reaction force chamber 50. I am not supposed to receive it.

The reaction chamber 50 (50A, 50B) has a piston 46 incorporated therein and is pushed by the spring 44 to the valve spool 30 side, but the reaction chamber 50 expands from the spool insertion hole 32. Therefore, the piston 46 cannot enter the spool insertion hole 32 and the pressure of the reaction force chamber 50 and the spring force of the spring 44 do not act on the valve spool 30 in the neutral state as shown in FIG. .

A passage 86, which serves as an oil return path and extends to the oil tank 82, is provided substantially at the center of the communication passage 40. A proportional solenoid type pressure control valve 70 capable of controlling the opening area of the passage 86 is installed in the passage 86. In the fluid passage of the pressure control valve 70, an automatic variable orifice 72 is formed that changes the opening according to the vehicle speed and the steering angle only near the neutral position of the handle 13. The variable orifice 72 is provided with a throttle portion 74 in a fluid passage in which fluid inlets and outlets are orthogonal to each other, and a portion 76A of the pilot spool 76 facing the throttle portion 74 is formed into a conical shape. By the exciting action of the solenoid 77, the pilot spool 76 can be slid together with the sliding shaft 78 to change the fluid passage opening area of the throttle portion 74.

The pressure control valve 70 is connected to the controller 84, and the pressure in the pressure chambers 50A and 50B can be adjusted by operating the proportional solenoid 77 in response to a signal from the controller 84 to change the fluid passage opening area of the throttle portion 74. It is like this.

The amount of electricity supplied to the proportional solenoid 77 of the pressure control valve 70 is controlled by a control signal from the controller 84. The controller 84 inputs signals from a vehicle speed sensor 88 provided on a wheel wheel shaft and the like and a steering angle sensor 89 provided on the steering shaft 11 of the steering wheel 13 and outputs a predetermined output signal in response to the signals. 77
The pressure control valve 70 operates in response to this signal, and the pressure introduced into the pressure chamber 50 is specified.

The control characteristic of the pressure control valve 70 is determined as follows.

That is, a signal corresponding to the vehicle speed at which the vehicle is stopped, such as when the vehicle is parked or when the vehicle is stationary, is output by the controller 84.
When the input is input to, the reaction force pressure control valve 70 is controlled so as to maintain the pressure in the reaction force chamber 50 at the tank pressure of the oil tank 82 irrespective of the steering angle of the handlebar 13, and FIGS. of the diagram (the horizontal axis steering torque, the vertical axis represents the power steering pressure and power cylinder output) is adapted to maintain the state of the full power as shown by V ₀ to.
As shown in the diagram of FIG. 5 (the horizontal axis is the steering angle, the vertical axis is the proportional solenoid energization value of the reaction force pressure control valve), within a certain steering angle range near the steering wheel neutral position as the vehicle speed increases. At, the energization value of the proportional solenoid changes. That is, when the vehicle speed V ₁ is the steering angle θ ₁ , when the vehicle speed V ₂ is the steering angle θ ₂ , ... At the vehicle speed V _n , the energization value of the proportional solenoid 77 is changed within the range of the steering angle θ _n. Has become. When the steering angle is equal to or more than the above-mentioned steering angle, a constant current value corresponding to each vehicle speed is obtained regardless of the steering angle.

Next, the operation of the embodiment of the present invention will be described.

When the handle 13 is now rotated to the right (the direction of arrow A in FIG. 2), the resistance of the rack is large, so that the pinion shaft 22 tries to displace in the direction opposite to the rack moving direction along the rack, and the fulcrum 29 of the swing lever 28 is urged. In the same direction (arrow B
)). This allows the valve spool 30
Moves in the same direction (the direction of arrow C) so that the pump port and the cylinder port 36 communicate with each other via the annular groove 38.
Pressure oil from 0 is supplied to the power cylinder 12.

At the same time, the high pressure fluid acts on both reaction force chambers 50A and 50B through the communication passage 40, and the valve spool 30 receives the drag force of the high pressure fluid in the reaction force chamber 50B. By the way, since this fluid circulates to the tank side through the variable orifice 72, the fluid pressure acting on the end face of the valve spool 30 as the drag force is determined by the fluid pressure ratio between the fixed orifice 43 and the variable orifice 72. Becomes Then, this reaction force is fed back via other components such as the swing lever 28, the pinion shaft 22, and the steering wheel 13 so as to give the driver a steering feeling as a valve reaction force.

By the way, when the vehicle is turned, that is, when the vehicle is stationary, while the vehicle is stopped, there is no input from the vehicle speed sensor 88 through the controller 84, so that the solenoid 77 is not excited and the pilot spool 76 is not changed. Therefore, the opening area of the variable orifice 72 becomes sufficiently large, so that the reaction force chamber 50
The fluid pressure in A and 50B is very small, so that the reaction force received by the valve spool 30 is also small, and the steering force for stationary steering becomes just light by power steering.

When the vehicle starts traveling, the energization value of the proportional solenoid 77 changes according to the vehicle speed within a certain range near the steering wheel neutral position as the vehicle speed increases, as shown in FIG. As shown in the diagram (the horizontal axis is the steering angle and the vertical axis is the variable throttle area), the opening area near the neutral position of the steering wheel can be changed from the opening area equivalent to the opening area at low speed, and the vehicle speed increases. However, the reaction pressure does not increase near the neutral position of the steering wheel. Therefore, as shown in the diagrams of FIGS. 3 and 4, the vicinity of the neutral position of the steering wheel and other positions are connected by a smooth curve, and good steering characteristics can be obtained, resulting in good feeling. In addition, the steering wheel 13 can be smoothly steered without feeling the weight at the beginning of turning, that is, the discomfort.

The vehicle speeds V ₁ to as shown in FIG. 5, V _2, ...... V respectively the steering angle steering angle with respect to _n is theta _1, theta _2, when it becomes more ...... theta _n is related to the steering angle Instead, a constant current value corresponding to each vehicle speed is applied to the proportional solenoid 77 depending on each vehicle speed.

The above relationship is shown in a flowchart of FIG.

Explaining the case where the reaction force pressure is controlled depending on the vehicle speed regardless of the steering angle, the vehicle speed is detected by the vehicle speed sensor 88 and an excitation signal is sent to the solenoid 77 via the controller 84. From this controller 84 to solenoid 77
The exciting current sent to is increased in proportion to the vehicle speed.

Due to the exciting action of the solenoid 77, the pilot spool 76 slides in the direction of the throttle 74 together with the sliding shaft 78, and the orifice opening area is reduced to reduce the reaction force chambers 50A, 5A.
The fluid pressure in 0B increases.

That is, when the vehicle speed increases and the ground contact resistance increases, if the steering wheel is turned at this time, the steering wheel becomes too light due to power steering and the steering feeling is lost, but the reaction force for obtaining the steering reaction force as described above. Since the pressure in the chambers 50A and 50B increases and the steering wheel feedback is performed via the swing lever 28 and other components, an optimum constant steering force according to the vehicle speed is always maintained.

Further, by automatically closing the automatic variable orifice 72 during high-speed operation and maximizing the supply pressure to the reaction force chambers 50A and 50B in the power cylinder control valve mechanism 20, the reaction force of the steering feeling having the largest V _n curve is maximized. Becomes a characteristic,
Further, it is of course possible to bring this closer to a manual state as shown by the symbol MS in FIG. 4 if necessary.

In this embodiment, since the pressure oil is supplied into both reaction force chambers 50A and 50B through one fixed orifice 43, the pressures in both reaction force chambers 50A and 50B are always the same. There is no difference in the steering reaction force even if steering is performed in either the left or right direction. As a result, stable turning travel is possible.

Further, in the pressure control valve 70 used in the above embodiment, the fluid inflow and outflow directions are orthogonal to each other. However, as shown in FIG. 8, the fluid inflow and outflow directions are the same. The configured pressure control valve may be used. The pressure control valve 90 has an annular groove 93 in the fluid passage, which is orthogonal to the fluid flow direction and faces the fluid outflow and outflow ports 91 and 92 on the outer circumference.
A pilot spool 94 having a groove formed therein, and the pilot spool 94 is slid together with the sliding shaft 96 by the exciting action of the solenoid 95. The area of the fluid passage opening can be changed.

〔The invention's effect〕

As described above, according to the present invention, the steering characteristic in the vicinity of the neutral position of the steering wheel is improved while the vehicle is traveling, the feeling is improved, and smooth steering can be performed without any discomfort at the beginning of turning the steering wheel.

[Brief description of drawings]

1 to 7 relate to an embodiment of the present invention, FIG. 1 is a block diagram of the present invention, FIG. 2 is a circuit diagram showing a part of a vehicle speed sensitive type power steering apparatus in section, and FIG. 6 to 6 are diagrams showing steering performance characteristics, FIG. 7 is a float chart showing the operation of the present invention, and FIG. 8 is a longitudinal section showing another embodiment of the reaction force pressure control valve used in the present invention. FIGS. 9 to 13 are diagrams showing steering characteristics according to the conventional example. 12 ... Power cylinder, 20 ... Power cylinder control valve mechanism, 43 ... Fixed orifice, 50 ... 50A, 50B
A reaction force chamber, 70 ... Reaction force pressure control valve, 72 ... Variable orifice, 80 ... Pump, 88 ... Vehicle speed sensor, 89 ... Steering angle sensor.

Claims (1)

[Claims] 1. A vehicle speed sensor for detecting a vehicle speed, a steering angle sensor for detecting a steering angle, a valve for switching pressure oil discharged from a pump to a power cylinder, and a reaction force chamber for suppressing movement of the valve. A power cylinder control valve mechanism, a reaction force pressure control valve having a variable orifice arranged in the flow path from the reaction force chamber to the oil tank, for controlling the reaction force pressure to the reaction force chamber, and the pump. A fixed orifice provided in a flow path connecting to the power cylinder, communicating with the reaction force chamber, and diverting a part of the discharge flow rate from the pump supplied to the power cylinder to the reaction force pressure control valve side; , The reaction pressure control valve is based on the information of the vehicle speed sensor and the steering angle sensor, when the vehicle is running,
The variable throttle area of the orifice is reduced depending on the steering angle only in the vicinity of the neutral position of the steering wheel according to each vehicle speed, and at other steering angles, the variable throttle area is set to a constant variable throttle area set by the vehicle speed. A vehicle speed-sensitive power steering device characterized in that