JP3038363B2 - 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 hydraulic power steering apparatus that generates a steering assist force by supplying a discharge hydraulic pressure of a hydraulic pump mounted on a vehicle.

[0002]

2. Description of the Related Art In recent automobiles, power steering devices (power steering devices) have become widespread in order to reduce the labor required for operating steering wheels (steering wheels) for steering and to obtain a comfortable steering feeling. ing.

[0003] The power steering apparatus is roughly classified into a hydraulic type using a hydraulic actuator as a source of steering assist force and an electric type using an electric motor. The former, that is, a hydraulic power steering device, sends a hydraulic pressure generated by a hydraulic pump mounted on a vehicle to a hydraulic actuator arranged in a steering mechanism in accordance with steering operation, and the hydraulic actuator The steering pressure is assisted by the hydraulic pressure generated. In order to drive the hydraulic pump, it is reasonable to use an engine mounted on the vehicle. The drive shaft of the hydraulic pump and the output shaft of the engine are directly connected via a transmission means such as a V-belt. Is generally used to drive a part of the driving force of the hydraulic pump.

[0004]

The steering of an automobile is performed against a road surface reaction force acting on a steered wheel, and the magnitude of the road surface reaction force is determined by the vehicle speed and the steering angle. Therefore, in the power steering device, it is necessary to generate a maximum steering assist force in a state where steering is largely performed at the time of low speed traveling or stop, that is, a so-called stationary state, and the source of operating hydraulic pressure is required. The specifications of the hydraulic pump are selected on the basis that the required hydraulic pressure and the required oil amount in the stationary state can be secured.

However, when the hydraulic pump selected in this way is driven by an engine, since the magnitude of the rotation speed of the engine substantially corresponds to the level of the vehicle speed, the hydraulic pump needs a large steering assist force. In this case, a large amount of discharge oil is generated during high-speed running. Most of the discharged oil is surplus oil that is returned to the oil tank without being supplied to the hydraulic actuator. Due to the unnecessary power burden for increasing the pressure of the surplus oil, the load on the engine increases and There was a drawback that caused a reduction in fuel efficiency.

Particularly in recent years, fuel efficiency regulations for automobiles, such as fuel efficiency regulations based on CAFE (Corporate Average Fuel Economy) values, which are being studied in the United States, have tended to be further tightened. In order to achieve this, it is important to eliminate the unnecessary power consumption described above.

[0007] To solve such difficulties, Japanese Patent Laid-Open No.
Japanese Patent No. 34364 discloses a structure in which the hydraulic pump and the engine are connected via an electromagnetic clutch, and the electromagnetic clutch is disengaged in accordance with a slow vehicle speed so that the hydraulic pump is driven only at a low speed. Power steering devices have been proposed.

The applicant of the present application also connects a drive shaft of a hydraulic pump, which is directly connected to a small electric motor, to an output end of an engine via an electromagnetic clutch, and engages the electromagnetic clutch in accordance with the vehicle speed. In fact, a power steering device that is selectively driven by a motor during high-speed running and by an engine during low-speed running and when stopped has already been proposed (Japanese Utility Model Application No. 3-111081). In this configuration, for example, when steering is performed during deceleration or acceleration, a further advantage is obtained in that there is little change in the steering sensation before and after the engagement of the electromagnetic clutch, and there is no possibility that the driver will feel strange.

However, an electromagnetic clutch having a sufficient disconnection capability with respect to a driving force required when the hydraulic pump serving as a hydraulic source of a power steering device is stationary is provided with a disconnection current that can be used on a vehicle. In practice, the electromagnetic clutch must be quite large, and in many cases, the electromagnetic clutch cannot be disposed around the hydraulic pump disposed in a limited space on the vehicle. However, there is a problem that it is difficult to realize the above-described configuration.

The present invention has been made in view of such circumstances, and enables a small electromagnetic clutch to connect a hydraulic pump, which is a hydraulic pressure source, to an engine, and secures a required hydraulic pressure and a required oil amount during stationary operation. It is an object of the present invention to provide a power steering device capable of reducing unnecessary power burden on an engine at the time of high-speed running.

[0011]

A power steering apparatus according to the present invention selectively drives a hydraulic pump mounted on a vehicle by a motor directly connected to the hydraulic pump or an engine connected via an electromagnetic clutch. A power steering device that generates a steering assisting force by hydraulic pressure supplied from the hydraulic pump, a hydraulic cylinder attached to the electromagnetic clutch for assisting an engaging operation of the electromagnetic clutch, and an operation of the hydraulic cylinder. An oil guide path that guides the supply oil pressure as a hydraulic pressure, a vehicle speed sensor that detects a traveling speed of the vehicle, and an engagement current of the electromagnetic clutch and a drive current of the motor according to a vehicle speed detected by the vehicle speed sensor. And control means for passing through.

[0012]

According to the present invention, when the vehicle speed is low, power is supplied to the motor directly connected to the hydraulic pump, and power is supplied to the electromagnetic clutch interposed between the hydraulic pump and the engine. The pump is driven by the power generated by the motor and the driving power of the engine transmitted via the electromagnetic clutch, and the hydraulic pressure supplied from the hydraulic pump is used to generate steering assist power. At this time, the electromagnetic clutch is engaged by the engagement force generated by itself in response to the energization and the hydraulic pressure attached to the hydraulic cylinder by the action of the supply hydraulic pressure, and As the required hydraulic pressure increases, a stronger engagement state is obtained. Therefore, when the steering is performed at the time of stopping or traveling at low speed and the required hydraulic pressure at the destination is high, the required hydraulic pressure can be secured by transmitting sufficient driving force from the engine, and in other cases, the required hydraulic pressure can be secured. The transmission is small, and a decrease in fuel efficiency due to unnecessary power burden is suppressed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing a system configuration of a power steering device according to the present invention (hereinafter, referred to as the present device). In FIG. 1, reference numeral 1 denotes a pump main body that generates an operating oil pressure, and is configured to be driven by a motor 2 directly connected thereto and an engine 4 connected via an electromagnetic clutch 3. Is provided with an auxiliary cylinder 5 for assisting the engagement operation by hydraulic pressure generated as described later.

Reference numeral 6 denotes a control unit for controlling the cutoff of the drive current to the motor 2 and the cutoff of the engagement current of the electromagnetic clutch 3. The detection result of the vehicle speed sensor 60 for detecting the traveling speed of the vehicle is given to the input side of the control unit 6,
The motor 2 and the electromagnetic clutch 3 are energized by a vehicle speed sensor 60.
Is performed in response to an energization command issued by the control unit 6 when the detection result is equal to or less than a predetermined reference speed set in advance.

Only when the current vehicle speed detected by the vehicle speed sensor 60 is low, the pump body 1 receives the generated force of the motor 2 directly connected thereto and the electromagnetic clutch 3 in the engaged state. It is rotationally driven by the transmitted driving force of the engine 4. The oil discharged from the pump body 1 passes through a hydraulic control valve 7 provided in the middle of a steering wheel shaft 71 connecting the steering wheel 70 and the steering mechanism 80, and is provided with a hydraulic pressure arranged to apply a steering assist force to the steering mechanism 80. The hydraulic pressure supplied to the actuator 8 is also introduced to the auxiliary cylinder 5 via an oil guide 9 which branches off the oil supply path to the hydraulic control valve 7.

The hydraulic control valve 7 performs an operation of supplying and discharging hydraulic pressure according to the twist generated on the steering wheel shaft 71 by the steering torque applied to the steering wheel 70. The hydraulic control valve 7 is supplied from the pump body 1 with the supply and discharge operation. The hydraulic actuator 8 performs an operation of generating a hydraulic pressure (steering assist force) corresponding to the direction and magnitude of the steering torque and applying the hydraulic pressure to the steering mechanism 80 by the hydraulic pressure. Thereby, the operation of the steering mechanism 80 according to the operation of the steering wheel 70, that is,
The steering operation of the vehicle is assisted.

On the other hand, the auxiliary cylinder 5 is
Generates an oil pressure (engagement assisting force) corresponding to the oil pressure introduced through the oil guide passage 9, and applies this force to the electromagnetic clutch 3 as described later, so that the engaging operation of the electromagnetic clutch 3 is performed. It assists and strengthens the engagement. The hydraulic pressure introduced into the auxiliary cylinder 5 is the hydraulic pressure supplied to the hydraulic actuator 8 via the hydraulic control valve 7, and the level of the hydraulic pressure corresponds to the magnitude of the steering assist force generated by the hydraulic actuator 8. Accordingly, the magnitude of the engagement assist force generated by the auxiliary cylinder 5 corresponds to the strength of the engagement state of the electromagnetic clutch 3.

Here, the magnitude of the steering assist force generated by the hydraulic actuator 8 depends on the steering wheels 81, 81 that contact the road surface.
The magnitude of the road surface reaction force corresponds to the vehicle speed slowdown and the magnitude of the steering angle, respectively. That is, in the device of the present invention, the engagement assisting force generated by the auxiliary cylinder 5 juxtaposed to the electromagnetic clutch 3 increases the steering assisting force generated by the hydraulic actuator 8 to which the hydraulic pressure is supplied from the pump body 1. The engagement state of the electromagnetic clutch 3 is strengthened by the action of the engagement assisting force, and the electromagnetic clutch 3 itself does not need to have a high engagement ability, and the electromagnetic clutch 3 is downsized. Can be performed, and the energizing current for engagement can also be reduced.

In the device of the present invention configured as described above, when the current vehicle speed detected by the vehicle speed sensor 60 is higher than the reference speed, the controller 2 controls the motor 2 by the above-described operation. Since power is not supplied and the electromagnetic clutch 3 is in a disconnected state, the pump body 1 does not perform a pumping operation, and the hydraulic actuator 8 does not generate a steering assist force.

On the other hand, when the vehicle is running at a low speed where the vehicle speed detected by the vehicle speed sensor 60 is lower than the reference speed, power is supplied to the motor 2, the electromagnetic clutch 3 is engaged, and the pump body 1 Driven by the output of the motor 2 and the output of the engine 4 transmitted via the electromagnetic clutch 3, the discharge hydraulic pressure of the pump body 1 is controlled by a hydraulic control valve 7.
Is supplied to the hydraulic cylinder 8 via the oil passage and to the auxiliary cylinder 5 via the oil guide passage 9.
Is not performed and the generation of the steering assist force by the hydraulic actuator 8 is unnecessary, the supply hydraulic pressure is kept at a low level, and the generated force of the auxiliary cylinder 5 operated by the supply hydraulic pressure is also small. The state of engagement of the electromagnetic clutch 3 is weak, and the amount of power transmitted from the engine 4 is limited.
The pump body 1 is mainly driven by the output of the motor 2.

When the steering wheel 70 is operated in this state, the operation of the hydraulic control valve 7 in accordance with the operation causes the supply of oil to the upstream side of the hydraulic control valve 7, that is, to the auxiliary cylinder 5. The hydraulic pressure is increased, and the engagement state of the electromagnetic clutch 3 is strengthened as the hydraulic pressure increases. At this time, the pump body 1
It is mainly driven by the output of the engine 4 transmitted through the electromagnetic clutch 3 in a firmly engaged state, and the hydraulic actuator 8 operated by oil supply from the pump body 1 generates a large steering assist force. It can occur with margin. Further, the power burden on the engine 4 required for driving the pump body 1 is such that the steering assist force to be generated by the hydraulic actuator 8 due to the oil supply from the pump body 1 is large, that is, the vehicle speed is low and the steering angle is large. In this case, the power load only increases, and the power burden on the engine 4 as a whole is small, and the fuel consumption is slightly reduced.

The apparatus of the present invention as described above comprises a pump body 1,
This is realized by using a pump assembly shown in FIG. 2 which integrally includes a motor 2, an electromagnetic clutch 3, and an auxiliary cylinder 5.
The pump body 1 is a known vane pump, and has a cylindrical rotor provided with a plurality of vanes so as to be able to advance and retreat in a radial direction.
10 is coaxially loosely fitted inside a cam ring 11 forming an unbalanced annular shape, and these are integrally housed in a housing 14 together with a pressure plate 12 coaxially positioned on one side of the cam ring 11. End plate 13 on the other side
, And a plurality of pump chambers are formed between the inner circumference of the cam ring 11 and the outer circumference of the rotor 10.

The motor 2 has a stator 20 having a magnet fixed to the inner periphery of a thin cylindrical yoke housing 21 having one side coaxially fixed to the outer surface of the housing 14 of the pump body 1. A grommet 23 fixedly mounted on the other side of the yoke housing 21 and also serving as a support member for the rotor 22. , A rotational force is obtained by the rotor 22 in the magnetic field formed by the stator 20 inside the yoke housing 21 by supplying power to the coil through the coil.

The rotation shaft 24 of the rotor 22 is connected to a yoke housing
21, that is, inside the housing 14 of the pump body 1 and outside the grommet 23, the extending portion to the housing 14 side is a ball that is fitted and fixed to the housing 14 as shown in the figure. The bearing is supported by a bearing and a bearing bush fitted on the shaft center of the end plate 13, and the rotor 10 is fitted between these bearing positions.

That is, the pump body 1 and the motor 2 are in a state of being directly connected via the common rotary shaft 24,
The rotor 10 rotates according to the rotation of the rotor 22 accompanying the power supply to the motor 2, and from the suction pipe 15 fixed to the outside of the housing 14 through the suction oil passage 16 on the end plate 13 side, the pump chamber The pressurized oil is discharged through a pressure chamber 17 on the back side of the pressure plate 12 and a valve chamber 18 connected to the pressure chamber.

The electromagnetic clutch 3 is formed inside a clutch housing 30 coaxially fixed to the outer surface of the grommet 23. The input shaft 31 to the electromagnetic clutch 3 is a ball bearing
The clutch housing is supported by the
The input end of the input shaft 31 extending to the outside of the clutch housing 30 has a V-pulley 33 fitted thereto.
And an output shaft of the engine 4 via a V belt (not shown) wound around the V pulley 33.

The extension end of the input shaft 31 inside the clutch housing 30 is in contact with the extension end of the rotary shaft 24 of the motor 2 protruding from the shaft center of the grommet 23. A pair of friction plates 34 and 35 facing each other at a predetermined interval are fitted to the portion, and an annular surface is formed on the outer surface of the grommet 23 on the back of the friction plate 34 on the rotating shaft 24 side. In this case, the exciting coils 36 which are provided around are opposed to each other.

Thus, in this electromagnetic clutch 3,
When an exciting current supplied from an exciting circuit (not shown) is applied to the exciting coil 36 in response to an energizing command from the control unit 6, the action of the magnetic field generated by the exciting coil 36 causes the rotating shaft 24 to rotate.
The friction plate 35 on the input shaft 31 side is attracted to the friction plate 34 on the side, and the rotary shaft 24 and the input shaft 31, that is, the pump body 1 and the engine 4 are engaged by friction between the two plates 34 and 35. Is done.

The auxiliary cylinder 5 for assisting the engagement of the electromagnetic clutch 3 by hydraulic pressure is provided between the inner periphery of the clutch housing 30 and the outer periphery of the input shaft 31 so as to be slidable in the axial direction. The friction plate 35 fitted and fitted to the input shaft 31
And a pressure receiving plate 50 opposed to the rear surface of the clutch housing 30 as shown in FIG.
It has a pressure guiding chamber 51 formed by sealing the inner and outer circumferences of the ring and the oil seal in a liquid-tight manner.

The pressure guiding chamber 51 communicates with a connecting hole 90 formed with an opening in the outer surface of the clutch housing 30. The connecting hole 90 has a base end close to the discharge side of the pump body 1. And a pressure guiding pipe 91 piped as shown by a two-dot chain line in the figure.
Are connected. That is, the discharge hydraulic pressure of the pump body 1 is introduced into the pressure guide chamber 51 through the oil guide passage 9 formed by the pressure guide pipe 91 and the connection hole 90, and the pressure receiving plate 50 receiving the hydraulic pressure is supplied to the pressure guide plate 51. As shown in the figure, the friction plates 34 and 35 slide in the axial direction against the spring force of a coil spring interposed between the friction plates 35 and are in sliding contact with each other by energizing the exciting coil 36. , The frictional force between the two plates 34 and 35 is increased, and the engagement of the electromagnetic clutch 3 is strengthened.

In the device of the present invention, as a result of the above-described engagement assisting operation performed by the auxiliary cylinder 5, the exciting coil
The original engagement capacity of the electromagnetic clutch 3 upon energization of the motor 36 may be small, and as shown in the figure, it is possible to employ friction plates 34 and 35 sufficiently smaller than the diameters of the pump body 1 and the motor 2. In addition, the size of the exciting coil 36 can be reduced, and the electromagnetic clutch 3 that engages the engine 4 with the pump body 1 can be significantly reduced in size. Significant compactness is achieved.

[0032]

As described above in detail, in the device according to the present invention, the interposition is provided between the drive shaft of the hydraulic pump for generating the hydraulic pressure supplied to the hydraulic actuator for steering assistance and the output shaft of the engine mounted on the vehicle. Since the engagement operation of the electromagnetic clutch that is disengaged according to the vehicle speed is assisted by the generation force of the hydraulic cylinder that uses the supply hydraulic pressure as the operating oil pressure, the electromagnetic clutch can be significantly reduced in size, A structure in which the engagement means including the electromagnetic clutch and the hydraulic cylinder can be easily arranged in a limited space around the hydraulic pump, and a sufficient steering assist force can be obtained when necessary without lowering the fuel consumption of the engine. Can be realized, and the present invention has an excellent effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of a device of the present invention.

FIG. 2 is a side sectional view showing one embodiment of a pump assembly used for realizing the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump main body 2 Motor 3 Electromagnetic clutch 4 Engine 5 Auxiliary cylinder 6 Control part 7 Hydraulic control valve 8 Hydraulic actuator 9 Oil guideway 10 Rotor 24 Rotary shaft 34 Friction plate 35 Friction plate 50 Pressure receiving plate 51 Pressure guide chamber 60 Vehicle speed sensor

Continuation of the front page (56) References JP-A-3-96480 (JP, A) JP-A-4-317864 (JP, A) JP-A-57-140276 (JP, A) Jpn. , U) Microfilm photographing the contents of the specification and drawings attached to the application for Japanese Patent Application No. 1-1112269 (Japanese Patent Application Publication No. 3-51680) (JP, U) Japanese Utility Model Application No. 63-167875 (Japanese Patent Application Publication No. -87985) Microfilm (JP, U) which photographed the contents of the specification and drawings attached to the application form (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/02

Claims (1)

(57) [Claims] A hydraulic pump mounted on a vehicle is selectively driven by a motor directly connected thereto or an engine connected via an electromagnetic clutch, and a steering assist force is supplied by hydraulic pressure supplied from the hydraulic pump. In the power steering device adapted to be generated, a hydraulic cylinder attached to the electromagnetic clutch to assist the engagement operation thereof, an oil guide path for guiding the supply hydraulic pressure as an operating oil pressure of the hydraulic cylinder, A vehicle speed sensor for detecting a traveling speed of the vehicle, and control means for passing an engagement current of the electromagnetic clutch and a drive current of the motor in accordance with a vehicle speed detected by the vehicle speed sensor. Power steering device.