JPH09263251A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate pressure corresponding to a pressure difference between a supply passage and a cylinder chamber directly in a pressure generating chamber by using a pressure generating chamber which is pressurized by the displacement of a spool and generates pressure corresponding to pressure difference, and a pressure detecting means which controls the rotation of a motor. SOLUTION: The pressure in a pressure generating chamber 50 is equal to pressure difference (0) introduced into the first and second pressure chambers 45, 46, which is detected by a pressure detecting sensor 53, and an output signal proportional to the pressure is outputted. When the output signal is inputted in a controller 17, a motor 10 is started by a controller 17, so that a hydraulic pump 11 is driven at a prescribed rotational speed. As a result, hydraulic oil of prescribed flow rate necessary for power assist is supplied to a control valve 15 and press-fed to a power cylinder 13 through one cylinder port 29, thus reducing steering wheel operating effort.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy-saving type power steering apparatus for driving and controlling an oil pump by an electric motor when necessary.

[0002]

2. Description of the Related Art A power steering apparatus that starts an electric motor only when a steering wheel is operated to drive an oil pump and supplies hydraulic oil to a power cylinder to reduce steering force of a steering wheel is known. It is publicly known as described in Kaihei 5-338549. This type of power steering system
It is known that the loss of engine power can be reduced and the fuel consumption of the vehicle can be reduced as compared with the case where the oil pump is constantly driven by the engine.

[0003]

By the way, this type of power steering apparatus detects the differential pressure between the supply passage and the high pressure side cylinder chamber of the power cylinder in order to detect that the steering wheel has been operated. I am trying. However, the conventional differential pressure detecting device is disclosed in the above-mentioned JP-A-5-338549.
As described in Japanese Patent Publication No. JP-A-2003-242242, since the displacement amount of the detection shaft, which is displaced according to the pressure difference between the supply passage and the high-pressure side cylinder chamber of the power cylinder, is detected by the differential transformer, As mentioned above, there are problems in terms of cost and reliability. That is, the differential transformer is not only expensive, but also easily causes a temperature drift, and moreover, since the differential pressure is converted into a displacement amount for detection, the differential pressure cannot be stably detected.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a relative rotation of an input shaft and an output shaft and a relative rotation of the input shaft and the output shaft causes a power cylinder. A control valve for communicating one cylinder chamber to the supply passage and the other cylinder chamber of the power cylinder to the discharge passage, an oil pump for discharging hydraulic oil to the supply passage, and a high pressure for the supply passage and the power cylinder. Side differential pressure detection device for detecting the pressure difference with the cylinder chamber,
An electric motor that drives and controls the oil pump when the differential pressure detected by the differential pressure detection device is a predetermined value or less,
The differential pressure detecting device includes a spool that is displaced according to a differential pressure between the supply passage and a high-pressure side cylinder chamber of the power cylinder, and a pressure that is pressurized according to the displacement of the spool and that corresponds to the differential pressure. And a pressure detecting means for detecting the pressure in the pressure generating chamber and controlling the rotation of the electric motor.

With the above structure, at the neutral position of the steering wheel (straight running state), the differential pressure between the supply passage and the high pressure side cylinder chamber of the power cylinder becomes large, and the spool of the differential pressure detecting device slides. Pressurize the pressure generating chamber. As a result, a pressure corresponding to the pressure difference between the supply passage and the cylinder chamber on the high pressure side of the power cylinder is generated in the pressure generating chamber,
This pressure is detected by the pressure detecting means and the rotation of the electric motor is reduced.

When the handle is operated in a proper state,
The pressure difference between the supply passage and the cylinder chamber on the high pressure side of the power cylinder is reduced, and the pressure in the pressure generation chamber is reduced. When this is detected by the pressure detecting means, the rotation of the electric motor is increased and the steering force of the steering wheel is power assisted.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of the power steering apparatus. The power steering apparatus mainly includes an electric motor 10
And an oil pump 1 driven by this electric motor 10.
1, a reservoir 12, a power cylinder 13 for power assisting steering operation, and a rotary control valve 1 that operates in response to an operation of a steering wheel 14 and throttle-controls hydraulic oil supplied from the pump 11 to the power cylinder 13.
5 and the differential pressure detection device 16 for detecting the operation of the handle 14.
And a controller 17 that controls the rotation of the electric motor 10 according to the output of the differential pressure detection device 16. When the oil pump 11 is driven by the electric motor 10, hydraulic oil is discharged to the supply passage 18. It has become so.

In FIG. 2, reference numeral 20 denotes a rack and pinion type gear housing, and an input shaft 21 and an output shaft 22 are rotatably housed in the gear housing 20 on the same axis, respectively. The shafts 22 are connected to each other via a torsion bar 23 so as to be rotatable relative to each other. An inner valve 25 and an outer valve 2 that constitute the control valve 15 are provided on the input shaft 21 and the output shaft 22, respectively.
6 are provided. As shown in FIG. 3, the control valve 15 has two cylinder ports that connect the supply port 27 connected to the supply passage 18 to the left and right chambers of the power cylinder 13 by the relative rotation of the input shaft 21 and the output shaft 22. One of 29 and 30 communicates with the other, and the other communicates with the discharge port 31. The control valve 15 includes a center closed valve portion that closes the supply port 27 in the neutral state and a center open valve portion that opens the two cylinder ports 29 and 30 to the discharge port 31 in the neutral state.

A pinion shaft 33 is provided at the tip of the output shaft 22.
Is formed, and the rack shaft 3 meshing with the pinion shaft 33 is formed.
4 is slidably housed in the gear housing 20. A piston 35 of the power cylinder 13 is connected to the rack shaft 34, and the interior of the power cylinder 13 is divided into left and right cylinder chambers 13A and 13B by the piston 35.

Next, the structure of the differential pressure detecting device 16 will be described with reference to FIG. The gear housing 20 has a large diameter hole 40 having an inner diameter D1 and inner diameters D2 on both sides of the large diameter hole 40.
Small-diameter holes 41 and 42 of (D2 <D1) are continuously formed. The large-diameter hole 40 and the small-diameter holes 41, 42 include a central large-diameter portion 43A of the spool 43 and small-diameter shaft portions 4 on both ends.
3B and 43C are slidably fitted to the large diameter portion 4
First and second pressure chambers 45 and 46 are formed on both sides of 3A. The first pressure chamber 45 is communicated with the supply port 27 via a first introduction passage 47, and the second pressure chamber 46 is connected to either one of the cylinder ports 29, 30 via a second introduction passage 48 and a shuttle valve 49. Be communicated to. In the shuttle valve 49, the ball 49A housed in the valve moves due to the pressure difference between the two cylinder ports 29 and 30, and the higher pressure of the cylinder ports 29 and 30 causes the second pressure chamber 46 to move.
It communicates with.

One small diameter shaft portion 43C of the spool 43
Faces a pressure generating chamber 50 formed at one end of the small-diameter hole 42 so that the pressure generating chamber 50 can move back and forth.
A spring 51 having a weak spring force is provided to urge the first pressure chamber 45 toward the first pressure chamber 45. At the sliding end of the spool 43, the pressure generating chamber 50 is provided with the reservoir 12 via the through hole 52.
Open to the first and second pressure chambers 45,
When the spool 43 slides against the spring 51 due to the differential pressure of the pressure introduced into the pressure chamber 46, the small diameter shaft portion 43C closes the through hole 52, whereby the pressure generating chamber 5
A pressure corresponding to the differential pressure is generated in 0, and this pressure is detected by the pressure detection sensor 53. The pressure detection sensor 53 sends an electric signal proportional to the detected pressure to the controller 17, and the controller 17 controls the rotation speed of the electric motor 10 based on the electric signal as shown in FIG.

By the way, the first and second pressure chambers 4 are
The pressure receiving area A1 of 5 and 46 and the pressure receiving area A2 of the pressure generating chamber 50 are expressed by the following formulas. A1 = π / 4 (D1 ² −D2 ² ) A2 = π / 4 · D2 ² Here, if the inner diameters D1 and D2 are set so that the relationship of A1 = A2 is established, the first and second pressure chambers are set. 45,
It becomes possible to generate the same pressure as the differential pressure introduced in 46 in the pressure generating chamber 50. If the relationship of A2 <A1 is satisfied,
The pressure obtained by expanding the differential pressure in the pressure generating chamber 50 is reversed to A2> A.
With the relationship of 1, it is possible to generate a pressure in the pressure generating chamber 50 with a reduced differential pressure.

Next, the operation of the above configuration will be described. When the oil pump 11 is driven by the electric motor 10, hydraulic oil is discharged from the oil pump 11, and this hydraulic oil is supplied to the supply port 27 of the control valve 15 and the first differential pressure detection device 16.
It is supplied to each of the introduction paths 47. In the neutral position (straight running state) of the handle 14, the supply port 27 of the control valve 15 is closed and the pressure of the oil pump 11 is maintained at a high pressure, while the two cylinder ports 29 and 30 are connected to the discharge port 31. It is opened and kept at a low pressure.
Therefore, the difference (pressure difference) between the pressure introduced into the first pressure chamber 45 from the first introduction passage 47 and the pressure introduced into the second pressure chamber 46 from the second introduction passage 48 becomes large, and the spool 43 becomes It slides against the spring 51 to pressurize the hydraulic oil in the pressure generating chamber 50. If the small reaction force of the spring 51 is neglected, the spool 43 stops when the pressure in the pressure generating chamber 50 becomes equal to the differential pressure introduced into the first and second pressure chambers 45 and 46.

As a result, a pressure having the same pressure as the differential pressure introduced into the first and second pressure chambers 45 and 46 is generated in the pressure generating chamber 50, and this pressure is detected by the pressure detection sensor 53, and the pressure is detected. An output signal proportional to is output. When this output signal is input to the controller 17, the controller 17 controls the rotation speed of the electric motor 10 according to the output signal as shown by the solid line in FIG. That is, when the output of the pressure detection sensor 53 (the differential pressure in the pressure generating chamber 50) becomes equal to or higher than the set level, the electric motor 10
The rotation speed of is gradually decreased, and finally stopped.

In a proper state, the handle 14 is operated,
When the control valve 15 is actuated, the supply port 27 communicates with one cylinder port 29 (30) and the other cylinder port 30 (29) communicates with the discharge port 31. When the supply port 27 communicates with one cylinder port 29, the first and second pressure chambers 45, 4 of the differential pressure detection device 16 are connected.
The differential pressure introduced to 6 becomes substantially 0, and the spool 43
Slides by the force of the spring 51 and releases the pressurization of the hydraulic oil in the pressure generating chamber 50. Therefore, the pressure in the pressure generating chamber 50 becomes equal to the differential pressure (0) introduced into the first and second pressure chambers 45 and 46, which is detected by the pressure detection sensor 53, and an output signal proportional to the pressure is output. To be done. When this output signal is input to the controller 17,
The electric motor 10 is started by the controller 17, and the oil pump 11 is driven at a predetermined rotation speed. As a result, a predetermined flow rate of hydraulic oil required for power assist is supplied to the control valve 15
Is supplied to the power cylinder 13 via the one cylinder port 29, and the steering force of the steering wheel is reduced.

Thus, only when the pressure difference between the supply port 27 and the high pressure side of the cylinder ports 29, 30 becomes less than a predetermined value, that is, when the steering wheel 14 is steered, the electric motor 10 is started to activate the oil pump. By driving 11, the power loss required to drive the oil pump 11 can be significantly reduced, and energy saving can be achieved. In the above-described embodiment, the handle 14 is used for simplicity of explanation.
In the neutral state (straight running state), the electric motor 10 is described as being stopped based on the increase in the differential pressure. However, in reality, the electric motor 10 is based on the increase in the differential pressure.
When the stop is stopped, the hydraulic oil leaks from the control valve 15 and the differential pressure (output of the pressure detection sensor 53) decreases, so that the electric motor 10 is restarted. Therefore, practically, as shown by the solid line in FIG. 5, the electric motor 10 is driven at an extremely low speed even in the neutral state of the handlebar 14 and the hydraulic oil for the leakage is continuously supplied.

FIG. 6 shows another embodiment of the present invention. The same parts as those in the embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. In the figure,
Reference numeral 60 is an accumulator connected to the supply passage 18 of the oil pump 11, and reference numeral 61 is a check valve that blocks the flow from the accumulator 60 side to the oil pump 11 side. When the oil pump 11 is driven by the electric motor 10 and the working oil is discharged to the supply passage 18, the working oil is supplied to the accumulator 60, and the accumulator 60 accumulates pressure until a predetermined pressure is reached.

Due to the pressure accumulating action of the accumulator 60, even if the hydraulic oil slightly leaks from the control valve 15 after the electric motor 10 is stopped during non-steering, the differential pressure does not drop rapidly. Therefore, it is not necessary to continue driving the electric motor 10 in the neutral state of the steering wheel. In the above-described embodiment, the pressure detection sensor 53 that outputs an electric signal proportional to the pressure is used, and the electric motor 10 is output based on the output of the pressure detection sensor 53.
Although the example of controlling the rotation speed of No. 1 has been described, a pressure detection switch that turns on and off at a predetermined pressure may be used as the pressure detection unit. In this mode, as shown by the broken line in FIG. 5, when the pressure in the pressure generating chamber 50 becomes equal to or lower than a predetermined value, the pressure detection switch is turned on, and the electric motor 10
Is driven at a high rotation speed, and when the pressure in the pressure generating chamber 50 becomes equal to or higher than a predetermined value, the pressure detection switch is turned off, and the rotation speed of the electric motor 10 is controlled to be reduced or stopped.

As described above, according to the above-described embodiment, the first and second differential pressure detecting devices 16 are used.
A differential pressure introduced into the pressure chambers 45 and 46, that is, a pressure corresponding to the differential pressure between the supply passage 27 and the high pressure side of the cylinder ports 29 and 30 is generated in the pressure generating chamber 50, and this pressure is detected. 53 or the pressure detection switch is used for direct detection, the differential pressure can be detected without using an expensive and unstable differential transformer as in the conventional case, and the electric motor 10 drives the oil pump 11 when necessary. This has the effect of improving the reliability of the energy-saving type power steering apparatus and contributing to cost reduction.

[0020]

According to the present invention, the differential pressure detecting device is provided with a spool which is displaced according to the differential pressure between the supply passage and the high pressure side cylinder chamber of the power cylinder, and a differential pressure which is applied by the displacement of the spool. Since the pressure generating chamber for generating a pressure corresponding to the pressure and the pressure detecting means for detecting the pressure in the pressure generating chamber to control the rotation speed of the electric motor are provided, the supply passage and the cylinder on the high pressure side of the power cylinder are configured. It is possible to directly generate a pressure in the pressure generating chamber according to the pressure difference between the chamber and the pressure generating chamber, which eliminates the need for using an expensive and unstable differential transformer as in the conventional case. There is an effect that improvement and cost reduction can be realized.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a power steering device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a specific configuration of a power steering apparatus.

FIG. 3 is a sectional view showing a configuration of a control valve.

FIG. 4 is a cross-sectional view showing a configuration of a differential pressure detection device.

FIG. 5 is a diagram showing a relationship between a differential pressure (electric signal) and a rotation speed of an electric motor.

FIG. 6 is an overall configuration diagram of a power steering apparatus showing another embodiment of the present invention.

[Explanation of symbols]

 10 Electric Motor 11 Oil Pump 12 Reservoir 13 Power Cylinder 14 Handle 15 Control Valve 16 Differential Pressure Detection Device 17 Controller 27 Supply Port 29, 30 Cylinder Port 31 Discharge Port 43 Spool 45, 46 Pressure Chamber 50 Pressure Generation Chamber 53 Pressure Detection Sensor

Claims (4)

[Claims] An input shaft and an output shaft that are relatively rotatable;
A control valve that communicates one cylinder chamber of the power cylinder with the supply passage and the other cylinder chamber of the power cylinder with the discharge passage by the relative rotation of the input shaft and the output shaft, and discharges the hydraulic oil into the supply passage. An oil pump, a differential pressure detection device for detecting a differential pressure between the supply passage and the high pressure side cylinder chamber of the power cylinder, and the differential pressure detection device detects the differential pressure below a predetermined value. An electric motor for driving and controlling an oil pump is provided, and the differential pressure detection device includes a spool that is displaced according to a differential pressure between the supply passage and a high pressure side cylinder chamber of the power cylinder, and a displacement of the spool. A pressure generating chamber that is pressurized and generates a pressure according to the differential pressure, and a pressure detecting unit that detects the pressure in the pressure generating chamber and controls the rotation of the electric motor. Power steering apparatus according to claim. 2. The power steering apparatus according to claim 1, wherein the pressure detecting means comprises a pressure detecting sensor that outputs an electric signal according to the pressure in the pressure generating chamber. 3. The power steering apparatus according to claim 1, wherein the pressure detecting means includes a pressure detecting switch that is turned on and off when the pressure in the pressure generating chamber reaches a predetermined value. 4. The control valve comprises a center closed valve part that closes a supply port communicating with the supply passage in a neutral state, and a center open valve part that opens two cylinder ports to a discharge port in the neutral state. Item 1. The power steering apparatus according to item 1.