JP2979460B2 - Power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device (power steering device) used for an automobile or the like.

[0002]

2. Description of the Related Art Generally, a power steering device reduces the steering force of a driver by applying a hydraulic assisting force to the steering device. This oil pressure is generated by the flow of oil "discharged" by a hydraulic pump driven by the engine or an electric motor.

For example, in Japanese Patent Application Laid-Open No. 2-290780, the "discharge oil" of a hydraulic pump constantly driven by an electric motor is controlled via a control valve (power steering (PS) valve) that is switched according to a steering state. In a power steering device that supplies power to one of two pressure chambers on both sides of a piston of a power cylinder mechanism, the output of an electric motor is controlled according to a vehicle speed and a steering speed.

A control valve such as a rotary valve operated by the driver's steering switches the flow of the "discharge oil" in accordance with the right or left steering direction to generate an assisting force. The aim is to reduce the force.

[0005]

However, conventionally, a complicated control valve such as a rotary valve or a spool valve is used to control the "discharge oil" of the hydraulic pump, so that the cost increases. There was a problem.

[0006] Further, since a considerably strong force is originally required for the steering assist, if the hydraulic pump is driven after the necessity of the assist is generated, the strong force is instantaneously raised. Since the hydraulic pump is constantly driven because it cannot be performed, there is a problem in terms of energy saving (fuel consumption efficiency), and in severe circumstances, there is a possibility that the electric motor may be heated or damaged.

The present invention has been made to solve the above-mentioned conventional problems, and does not require the use of an expensive rotary valve or the like, and it is sufficient to drive the hydraulic pump only at the time of steering. An object of the present invention is to provide an effective power steering device.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a hydraulic pressure is applied to a piston provided on a steering rack shaft and one of two pressure chambers provided on both sides of the piston. In a power steering device provided with a power cylinder mechanism that assists axial movement, a steering state detection unit that detects a steering state of the steering device, and a communication path that enables communication between two pressure chambers of the power cylinder mechanism. When,
A hydraulic pump that is driven when a steering state is detected by the steering state detection means and that allows oil to move between the two pressure chambers through the communication path; and a hydraulic pump on the communication path. And a pair of direction switching valves provided between the pressure chambers and the two pressure chambers and having a check valve function of controlling a moving direction of oil by a hydraulic pump in accordance with a steering direction. It has been achieved.

The directional control valve is constituted by an electromagnetic directional control valve, and a vibration state determining means for determining a vibration state of the steering rack shaft from a current fluctuation generated at the directional control valve during running of the vehicle. When the direction switching valve is controlled to reduce the vibration based on the determination result, flutter vibration or the like can be easily detected, and furthermore, the vibration can be easily suppressed. Also.

[0010]

According to the present invention, the steering state detecting means detects whether the driver has operated the steering device, for example, the steering state such as right or left and how fast the driver has operated. Then, only when the input signal is input, the hydraulic pump is driven in accordance with the input signal.

This hydraulic pump is not used for "generating discharge oil" for pumping oil from an oil tank and guiding it to a pressure chamber as in the prior art, but for "pressure" on both sides of a piston of a power cylinder mechanism. The oil between the chambers is moved through the communication passage. "

The direction of movement of the oil is switched by a pair of direction switching valves having a check valve function provided between the hydraulic pump and the two pressure chambers on the communication passage. Therefore, this pair of directional control valves cooperate and basically allow only the right pressure chamber → the left pressure chamber, and the left pressure chamber →
It suffices to create three modes, that is, only the right pressure chamber is permitted and totally free. Therefore, it is sufficient to have a function as a check valve, and there is no need for a complicated action like a conventional rotary valve.

Further, it is not necessary to drive the hydraulic pump during non-steering, such as when the vehicle is going straight, and since the rising characteristics are good, a sufficiently high assist force can be obtained even when the hydraulic pump is driven only when needed. Therefore, the driving time of the hydraulic pump can be greatly reduced, and the fuel consumption efficiency can be greatly improved.

Further, the direction switching valve is constituted by an electromagnetic switching valve,
When the vibration state of the steering rack shaft is determined from the current fluctuation generated in the drive circuit of the directional control valve constituted by the electromagnetic switching valve during vehicle running, vibration phenomena such as flutter vibration and kickback Can be easily detected, and when the directional control valve is controlled to reduce this vibration, the vibration can be effectively suppressed.

[0015]

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

FIG. 1 is a schematic configuration diagram showing an auxiliary steering force generating mechanism of a power steering apparatus (power steering apparatus) to which the present invention is applied.

In FIG. 1, reference numeral 10 denotes a pinion shaft which is rotated by a steering operation (steering operation) not shown.
Reference numeral 2 denotes a rack shaft that meshes with a pinion 14 provided at the tip of the pinion shaft 10. When the pinion shaft 10 rotates by the driver's steering, the pinion shaft 10 and the pinion 14 rotate, the rack shaft 12 moves to the right or left, and the wheels (not shown) are steered via a known mechanism.

At this time, with respect to the input of the steering torque,
The pinion shaft 10 is swingably mounted as indicated by an arrow in the figure, and the displacement of the pinion shaft 10 in the rack shaft 12 direction is determined by a displacement sensor 15 (such as a unit switch or a potentiometer) mounted on the tip of the pinion shaft 10. Steering state detecting means). The output of the displacement sensor 15 is converted into information on a steering state such as a steering direction or a steering torque by a controller 34 described later.

Reference numeral 16 denotes a power cylinder mechanism for generating an auxiliary steering force.
And is divided into a left cylinder chamber (left pressure chamber) 20 and a right cylinder chamber (right pressure chamber) 22.

Reference numeral 24 denotes a solenoid pump (hydraulic pump) for mutually moving the oil in both cylinder chambers 20 and 22 through a communication passage 25. The solenoid pump 24 includes a coil 26, a piston 28, and a gas chamber 30 in the upper part. Have.

Reference numerals 32 and 33 denote check valves (directional switching valves) for switching the direction in which the oil sent by the solenoid pump 24 flows. Reference numeral 34 denotes the output of the displacement sensor 15 attached to the tip of the pinion shaft 10 as described above. The controller (control device) controls the solenoid pump 24 and the check valves 32 and 33 by receiving the output from the vehicle speed sensor 36 and converting the information into steering information.

The structure of the check valves 32 and 33 is shown in FIG. In FIG. 2, reference numeral 38 denotes a housing made of a non-magnetic material such as aluminum, reference numerals 40 and 41 denote iron cores, reference numeral 42 denotes a coil wound around the iron core 40, and reference numeral 44 denotes plastic or rubber or the like which moves left and right in the housing 38. A poppet valve 46 is a magnet attached to the poppet valve 44.

Next, the operation will be described.

When the vehicle is traveling straight, no steering signal is generated from the displacement sensor 15 of the pinion shaft 10, so that the controller 34
Does not output a drive signal for the solenoid pump 24. At this time, as shown in FIG. 2, the two check valves 32 and 33 are not energized by the coil 42 and the iron core 40 is not magnetized, so the magnet 46 is attracted to the iron core 41 and the poppet valve 44 is located at the center in the housing 38 and is in a left-right communication state.

Therefore, for example, for a small steering input,
The oil in the left and right cylinder chambers 20 and 22 of the power cylinder 17 can move freely through the check valves 32 and 33 and the solenoid pump 24, and thus operates as a so-called manual steering mechanism.

Next, when the steering wheel is turned right, the tip of the pinion shaft 10 moves as shown by the arrow in FIG. Further, as described above, the signal of the vehicle speed sensor 36 is also input to the controller 34. The signal from the displacement sensor 15 is converted by the controller 34 into a steering direction (right turn in this case) and a steering torque.

From the controller 34, the drive output of the solenoid pump 24 corresponding to the vehicle speed signal and the check valve 3
2, 33 control signals are output.

As shown in FIG. 4, when current is applied to the coil 42, the upper part of the iron core 40 is magnetized to the S pole and the lower part thereof is magnetized to the N pole. The pole and the N pole of the iron core 40 attract each other, and the magnet 4
6 and the N pole of the iron core 40 are repelled, so that the poppet valve 44 moves to the left in the drawing, so that the oil flows only in one direction from left to right as indicated by the arrow.

Further, since the current flowing through the coil 26 of the solenoid pump 24 is controlled as shown in the waveform in the figure, the piston 28 repeats the vertical movement. At this time, piston 2
When the pressure 8 rises, the pressure between the check valves 32 and 33 decreases, the oil is sucked from the check valve 33, and when the piston 28 moves down, the oil flows into the check valve 3
Extruded from 2.

Accordingly, oil flows from the left cylinder chamber 22 of the power cylinder 17 to the right cylinder chamber 20, the oil is filled in the right cylinder chamber 20, the piston 18 is pressed to the left, and the rack shaft 12 is displaced to the left. The steering force is assisted.

Next, when turning the steering wheel to the left, the operation is basically the same as that for turning to the right. However, as shown in FIGS.

That is, as shown in FIG. 5, when the steering wheel is turned to the left, the tip of the pinion shaft 10 moves as indicated by an arrow in the figure, and when this is transmitted to the controller 34 by the displacement sensor 15, the control signal is transmitted from the controller 34. Is output.

As shown in FIG. 6, when the current flowing through the coil 42 is turned to the right, the check valves 32 and 33 are turned to the right and the upper part of the iron core 40 becomes the north pole and the lower part becomes the south pole. Moves to the right, causing oil to flow in only one direction, from right to left.

Here, when the piston 28 of the solenoid pump 24 repeatedly moves up and down, the oil is
Pump 24 through check valve 32
To the left cylinder chamber 20 from the check valve 33.
And the left cylinder chamber 20 is filled with oil. As a result, the piston 18 is pressed to the right, and the rack shaft 12 is displaced to the right.

Therefore, according to the present embodiment, the "discharge oil" pumped from the oil tank by the hydraulic pump is not distributed to the left and right cylinder chambers by using the rotary control valve as in the prior art. The power cylinder mechanism 16 is constituted by the solenoid pump 24 for directly moving the oils 20 and 22 and the check valves 32 and 33 for controlling the moving direction, so that the entire structure is simple and an expensive rotary control valve is unnecessary. Therefore, since the solenoid pump 24 can be driven only at the time of steering due to its low cost and responsiveness, power consumption other than the controller input signal processing can be reduced to zero outside the power assist region. And save energy.

The gas chamber 3 above the solenoid pump 24
When nitrogen gas is sealed in 0, a sealed power steering system can be formed and abnormal noise of oil can be reduced.

Further, at high speed, the left and right cylinder chambers 2
The controller 34 can also function so as to apply pressure to 0 and 22. This increases the apparent rigidity of the rack shaft 12 in the left and right directions, so that the controller 34 can function as a so-called flutter damper. Prevention can be achieved.

Since the left and right vibration of the rack shaft 12 causes a change in the volume of the left and right cylinder chambers 20 and 22, this is transmitted to the check valve 32, the magnet 46 vibrates in the left and right direction, and the coils 42 of the check valves 32 and 33 are turned. An AC current corresponding to the current is generated.

Therefore, as shown in FIG.
When 0 (this corresponds to the vibration state determination means) is provided,
By detecting the current, the phenomenon of flutter vibration and kickback vibration on a rough road can be detected. As a result, the left and right cylinder chambers 20 and 22 are pressurized to suppress these vibrations, or the left and right cylinder chambers 20 and 22 are pressurized so as to more positively resist the left-right vibration of the rack shaft 12. By causing the controller 34 to function, the vibration of the steering wheel can be more effectively prevented.

The power steering mechanism can be manufactured at a low cost by mass-producing the same device for each vehicle type. In addition, the control function changes the control content for each vehicle type and the information analysis method of the displacement sensor. And so on. As a result, for example, a steering return rotation function, a flutter damper function,
It is easy to stratify the added value of the steering system such as the shimmy damper function or the vehicle speed sensitive function, and it is possible to respond to the demands of the user in detail.

[0041]

As described above, according to the present invention,
Without using a rotary control valve or the like, a power steering mechanism can be configured with a hydraulic pump driven only at the time of steering and a pair of direction switching valves, so that it can be manufactured easily and inexpensively.
Power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view including a partial cross-sectional view illustrating an operation of a power steering system according to a first embodiment when the vehicle is traveling straight ahead.

FIG. 2 is a cross-sectional view showing the operation of the check valve according to the embodiment when the vehicle is traveling straight.

FIG. 3 is an explanatory view including a partial cross-sectional view illustrating a function of the power steering system of the present embodiment when turning right.

FIG. 4 is a cross-sectional view showing the function of the check valve of the present embodiment when turning right.

FIG. 5 is an explanatory view including a partial cross-sectional view showing the function of the power steering system of the present embodiment when the vehicle is turned left.

FIG. 6 is a cross-sectional view showing the function of the check valve of the present embodiment when the valve is turned left.

FIG. 7 is an explanatory view including a partial cross-sectional view illustrating a vibration suppression function of the power steering system according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Pinion shaft 12 ... Rack shaft 15 ... Displacement sensor 16 ... Power cylinder mechanism 17 ... Power cylinder 18 ... Piston 24 ... Solenoid pump 25 ... Communication path 32, 33 ... Check valve 34 ... Controller 36 ... Vehicle speed sensor 44 ... Poppet valve 50 … Current detector

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 5/08 B62D 6/00 F16K 31/06

Claims (2)

(57) [Claims] A power assisting the axial movement of the rack shaft by applying hydraulic pressure to a piston provided on a steering rack shaft and one of two pressure chambers provided on both sides of the piston. In a power steering apparatus provided with a cylinder mechanism, a steering state detecting means for detecting a steering state of the steering apparatus; a communication path enabling communication between two pressure chambers of the power cylinder mechanism; and a steering state detecting means. A hydraulic pump that is driven when a steering state is detected and that allows oil to move between the two pressure chambers through the communication path; and a hydraulic pump and the two pressure chambers on the communication path. And a pair of direction switching valves each having a check valve function of controlling a moving direction of oil by the hydraulic pump in accordance with a steering direction. Power steering apparatus according to symptoms. 2. The steering system according to claim 1, wherein the directional control valve comprises an electromagnetic directional control valve, and a vibration state of the steering rack shaft is determined from a current fluctuation generated at the directional control valve during vehicle running. A power steering device comprising: a vibration state determination unit that performs control of the direction switching valve based on the determination result so as to reduce the vibration.