JP2735743B2 - 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 apparatus for reducing the steering force of a steering wheel of a vehicle, and more particularly to a power steering apparatus which uses an electric motor and an oil pump as power sources to achieve low fuel consumption. It is.

[0002]

2. Description of the Related Art As is well known, there are a hydraulic steering system and an electric steering system. In many hydraulic systems, the oil pump is driven by the engine, but in this system, the oil pump is always driven by the engine even when traveling straight without requiring assistance, so the loss of engine horsepower is reduced. There is a big problem.

On the other hand, the electric type has an advantage that the oil pump described above can be dispensed with and the electric motor is started and power assisted only when necessary, so that loss of engine horsepower is small.

[0004]

By the way, in a hydraulic power steering device, an assist direction is mechanically determined for steering operation, whereas in an electric power steering device, a steering operation is performed. It is necessary to rotate the electric motor forward and backward according to the direction.

Therefore, in the electric power steering system, various measures have been devised for improving the reliability of the assist power control system, such as adding a safety circuit for preventing runaway of the control device and detecting abnormal mechanical operation. However, there are still many problems in terms of reliability as compared with the current hydraulic power steering device.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the conventional problems described above, but for the purpose of achieving energy saving by a hydraulic power steering apparatus, in the invention according to the first
Is a relatively rotatable input shaft and output shaft, and a steering neutral
In the state, both the supply passage and the power cylinder
A direction switching valve for communicating the other cylinder chamber of the power cylinder in the discharge passage communicated with the supply passage by the relative rotation of communicating with the input shaft is closed with respect to the output shaft of the chamber in one of the cylinder chambers of the power cylinder, An oil pump for discharging pressurized oil according to the number of revolutions into the supply passage, and the oil pump
An electric motor for driving the front Symbol differential pressure detector for detecting the differential pressure of the supply passage and the high pressure side of the cylinder chamber of the power cylinder
Means based on the differential pressure detected by the differential pressure detecting means.
Control means for controlling the electric motor.
According to the second aspect of the present invention, an input capable of relative rotation is provided.
Shaft and output shaft, and supply passage in neutral state of steering
And the communication between both cylinder chambers of the power cylinder
Power supply path by relative rotation between input shaft and output shaft
Communicates with one cylinder chamber of the cylinder and power
How to connect the other cylinder chamber of the cylinder to the discharge passage
Direction switching valve and discharges pressure oil according to the number of rotations to the supply passage
Pump and electric motor for driving the oil pump
And accumulate the pressure of the pressure oil discharged by the oil pump
An accumulator and a high-pressure side cylinder of the power cylinder
Differential pressure detecting means for detecting a differential pressure between the pressure chamber and the supply passage.
Based on the differential pressure detected by the differential pressure detecting means.
And control means for controlling the electric motor .

[0007]

[Action] By the above configuration, the oil pump is driven oil is discharged by the electric motor, oil is supplied to the rectangular direction switching valve and the differential pressure detecting means. If the straight running state at this time the handle is not being operated, since there is no relative rotation between the input shaft and the output shaft, the direction switching valve is in the neutral state, the supply passage is closed by both cylinders of the power cylinder < The chamber is not in communication with the supply passage . Therefore, the differential pressure detection
Cylinder chamber on the high pressure side of the power cylinder detected at the stage
Pressure difference between the pressure and the supply passage increases, and this differential pressure exceeds a predetermined value.
The electric motor stops and the oil pump
Exit is stopped.

Next, when the handle is operated and relative rotation occurs between the input shaft and the output shaft, the direction switching valve is operated, and the supply passage communicates with the cylinder chamber in the direction to be assisted. When one of the cylinder chambers in the direction to be assisted communicates with the supply passage, the supply pressure detected by the differential pressure detection means is detected.
The differential pressure between the passage and the one cylinder chamber decreases, and the differential pressure
Is less than a predetermined value, the discharge amount of the oil pump will increase.
Thus, the electric motor is controlled to assist the steering force.
The assist is complete, the supply passage is in the closed state is no relative rotation between the input shaft and the output shaft again, differential pressure
The differential pressure detected by the output means rises, and this differential pressure
When rises above, the electric motor is Ru is stopped.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2, reference numeral 10 denotes a rack and pinion type gear housing.
The output shaft 12 and the output shaft 12 are rotatably housed on the same axis. The input shaft 11 and the output shaft 12 are connected to each other via a torsion bar 13 so as to be relatively rotatable. The input shaft 11 is connected to a steering handle 14 as shown in FIG.

The input shaft 11 and the output shaft 12 are provided with an inner valve 19 and an outer valve 20, respectively, which constitute a direction switching valve 17. The direction switching valve 17 is supplied to the supply port by the relative rotation of the input shaft 11 and the output shaft 12. 2
1 is connected to one of the two cylinder ports 22 and 23, and the other is connected to the discharge port 24. When the direction switching valve 17 is in the neutral state, the supply port 24 is closed by the first land 19 a formed on the inner valve 19, and when the direction switching valve 17 is operated, the supply port 24 is switched to one of the cylinder ports 22 and 23. And a second land 19b formed in the inner valve 19 when in the neutral state, opens to the discharge port 24, and controls the pressure of the oil flowing into the cylinder ports 22 and 23 when the direction switching valve 17 is operated. It is composed of a center open valve that performs the operation.

A pinion tooth 25 is provided at the tip of the output shaft 12.
Are formed, and the rack teeth 2 meshing with the pinion teeth 25 are formed.
The rack shaft 27 having the groove 6 is slidably housed in the gear housing 10. As shown in FIG. 1, a power cylinder 30 for assisting steering torque is provided on the rack shaft 27.
Are connected. Power cylinder 30
The inside has a cylinder chamber partitioned by a piston 31 into a left chamber and a right chamber. These left and right chambers are communicated with the two cylinder ports 22 and 23, respectively.

Reference numeral 40 denotes a plunger type oil pump. The discharge side of the oil pump 40 is connected via a check valve 41 to an accumulator 42 for accumulating the pressure of the discharged oil. The accumulator 42 is connected to the supply passage 4
3 is connected to the supply port 21 of the directional control valve 17 and the differential pressure detector 60 via the directional control valve 3. It is to prevent.

As shown in FIG. 3, the differential pressure detector 60 comprises a case housing 61, a spool housing 62 fitted into the case housing 61, a spool valve 63 and a differential transformer 64. A sliding hole 65 is formed in the case housing 61, and a spool valve 63 is slidably fitted in the sliding hole 65. The spool valve 63 is composed of a shaft 66 and a plunger 67, and the plunger 67 is
5 is divided into a first pressure chamber 70 and a second pressure chamber 71. The first pressure chamber 70 communicates with the supply passage 43, and the second pressure chamber 71 communicates with the cylinder ports 22 and 23 via the shuttle valve 72. ing. In this shuttle valve 72, a ball 72a disposed in the passage moves due to a pressure difference between the cylinder ports 22 and 23, and the higher pressure of the cylinder ports 22 and 23 communicates with the second pressure chamber 71. .

A spring 69 is provided in the second pressure chamber 71.
And presses the plunger 67 toward the first pressure chamber 70. One end of a shaft portion 66 of the spool valve 63 penetrates the spool housing 62, and a tip of one end of the shaft portion 66 has a core 6 constituting a part of the differential transformer 64.
8 is attached. The differential transformer 64 detects the movement of the spool 68 by detecting the movement of the core 68 by a change in electromotive force generated in a secondary winding (not shown). As shown in FIG. 4, the supply passage 43 and the cylinder ports 22 and 23
The output signal of the differential transformer 64 is input to the controller 73.

A drive circuit 74 is connected to the controller 73. The drive circuit 74 is connected to an electric motor 75 for driving the oil pump 40. The controller 73 is composed of a microprocessor and a memory, and outputs a differential pressure ΔP between the supply passage 43 and the high pressure side of the cylinder ports 22 and 23 shown in FIG.
A command signal for driving the electric motor 75 is output to the drive circuit 74 when the output signal value becomes equal to or less than the output signal value V1 corresponding to 1.
The drive circuit 74 supplies power to the electric motor 75 only when a command signal is output from the controller 73, and drives the oil pump 40 to rotate in one direction.

The operation of the above configuration will be described. When the oil pump 40 is driven by the electric motor 75, the oil is discharged and the pressure oil is supplied to the accumulator 42 and the supply passage 43. When the pressurized oil is supplied, the accumulator increases the pressure to a predetermined pressure, and the oil supplied to the supply passage 43 flows into the direction switching valve 17 and the differential pressure detector 60. At this time, if the steering wheel 14 is not operated and the vehicle is running straight, no relative rotation occurs between the input shaft 11 and the output shaft 12, so that the direction switching valve 17 does not operate and the supply port 21 is It is in a closed state that does not communicate with any of the cylinder ports 22 and 23. In this closed state, the cylinder port 2
2 and 23 are open to the discharge port 24 and are not actuated by hydraulic pressure.
No pressure is applied to. Therefore, the movement of the spool valve 63 of the differential pressure detector 60 is determined only by the oil pressure in the supply passage 43, and an output signal V1 corresponding to the differential pressure ΔP1 is output from the differential transformer 64 of the differential pressure detector 60 to the controller 73. At this point, the electric motor 75 is stopped.

On the other hand, when the handle 14 is operated and the torsion bar 13 is twisted to rotate the input shaft 11 and the output shaft 12 relatively, the relative rotation of the two shafts activates the direction switching valve 17 to supply the supply port. 21 is connected to one cylinder port 22 and the other cylinder port 23 is connected to a discharge port 24. When the cylinder port 22 and the supply port 21 are communicated, the pressure stored in the accumulator 42 is supplied from the cylinder port 22 to one cylinder chamber of the power cylinder 30. According to the flow rate supplied to the power cylinder 30, the piston 31
Is slid, and the steered wheels are steered via a required link mechanism. At this time, the oil in the other chamber of the power cylinder 30 is discharged from the discharge port 24 of the direction switching valve 17 to the tank.

When the direction switching valve 17 is operated to connect the supply port 21 to one of the cylinder ports 22 and the other cylinder port 23 to the discharge port 24, it is held by the accumulator 42. Since the oil pressure in the supply passage 43 decreases and the pressure from the cylinder port 22 acts on the second pressure chamber 71 of the differential pressure detector 60, the first pressure chamber 70 and the second
The differential pressure in the pressure chamber 71 decreases. Therefore, the spool valve 6
3 is returned to the first pressure chamber 70 side, and when the output signal from the differential transformer 64 decreases to V1 or less, the oil pump 40 outputs the output signal of a predetermined value from the differential transformer 64 of the differential pressure detector 60. Is driven by the electric motor 75 until is output to the controller 73. After that, handle 14 continuously
Is carried out, there is no pressure difference between the supply passage 43 and the cylinder port 22, so that the oil pump 40 is continuously driven. When the steering of the steered wheels is completed and the relative rotation between the input shaft 11 and the output shaft 12 stops, and the inner valve 19 and the outer valve 20 are in the neutral state, the supply port 21 is closed again and the supply passage is closed. The oil pump 40 stops when the pressure rises to the detection signal V1 from the differential pressure detector 60.

As described above, the pressure oil is discharged from the oil pump 40 only when the pressure difference between the supply passage 43 and the high pressure side of the cylinder ports 22 and 23 is smaller than ΔP 1, that is, only when the steering wheel is steered. Useless discharge operation of the oil pump is eliminated, and energy saving is achieved. Further, by holding the pressure by the accumulator 42, it is possible to prevent a delay in assisting when the operation of the handle 14 is started.

In the above embodiment, the supply passage 43 is provided.
The pressure difference between the pressure and the high pressure side of the cylinder ports 22 and 23 is set to a predetermined value .DELTA.P1. By so doing, it is possible to provide a vehicle speed response that increases the steering force of the steering wheel according to the vehicle speed.

In the above embodiment, the input shaft 1
Although the example in which the output shaft 12 and the output shaft 12 are connected via the torsion bar 13 has been described, other spring means may be used instead of the torsion bar 13.

[0022]

As described above, the present invention provides a neutral steering system.
In the state, both the supply passage and the power cylinder
Direction switching valve that closes communication with the chamber and the power cylinder
Differential pressure detection to detect the differential pressure between the high pressure side cylinder chamber and the supply passage
The electric motor that drives the oil pump
Control based on the differential pressure detected by the detecting means
Since it is configured, it is Ru effect that can greatly reduce the loss of engine horsepower during straight running as compared with the conventional hydraulic power steering apparatus.

[0023]

[Brief description of the drawings]

FIG. 1 is a diagram showing a control block of a power steering device.

FIG. 2 is a sectional view of a power steering device.

FIG. 3 is a diagram showing a configuration of a differential pressure detector.

FIG. 4 is a diagram showing output characteristics of a detection signal of a differential pressure detector.

[Explanation of symbols]

 Reference Signs List 11 input shaft 12 output shaft 13 torsion bar 17 directional switching valve 30 power cylinder 40 oil pump 42 accumulator 75 electric motor 60 differential pressure detector 72 shuttle valve 73 controller 74 drive circuit

Claims (2)

(57) [Claims] An input shaft and an output shaft rotatable relative to each other and an operation shaft.
In the neutral state of the rudder, both the supply passage and the power cylinder
A direction switching valve for communicating the other cylinder chamber of the power cylinder in the discharge passage communicated with the supply passage to one of the cylinder chambers of the power cylinder by the relative rotation of the communicating closed and the input shaft and the output shaft of the cylinder chamber an oil pump which discharges pressurized oil in accordance with the rotation speed to the supply passage, the
An electric motor for driving the oil pump, the differential pressure detecting means for detecting the differential pressure of the cylinder chamber and the supply passage of the high pressure side of the front Symbol power cylinder, the detected differential pressure by the differential pressure detecting means
And a control means for controlling the electric motor based on the power steering. 2. An input shaft and an output shaft which are rotatable relative to each other.
In the neutral state of the rudder, both the supply passage and the power cylinder
The communication with the cylinder chamber is closed and the phase between the input shaft and output shaft is
The supply passage is rotated by one rotation of the power cylinder.
And the other cylinder of the power cylinder.
A directional switching valve for communicating the nozzle chamber with the discharge passage;
An oil pump that discharges pressure oil according to the number of revolutions into the passage,
An electric motor for driving an oil pump;
An accumulator that accumulates the pressure of the released pressure oil;
Between the cylinder chamber on the high pressure side of the power cylinder and the supply passage
Differential pressure detecting means for detecting the differential pressure, and the differential pressure detecting means
A control for controlling the electric motor based on the detected differential pressure.
A power steering device comprising a control means.