JPH1120721A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in fuel consumption due to increase in an engine load in a power steering device for a vehicle. SOLUTION: In a power steering device 1 operated by means of a hydraulic pump, an electric motor 11 is used as a drive source for a hydraulic pump 8 discharging hydraulic fluid to a hydraulic circuit 6, while a control unit 15 controlling drive of the electric motor 11 is arranged. By means of a pressure inside an accumulator 9, which is arranged in the hydraulic circuit 6 so as to accumulate the pressure of the hydraulic fluid, and an output from a speed reduction detecting means 14 detecting speed reduction travel of a vehicle, the hydraulic pump 8 is actively driven in a speed reduction travel time, so that drive of the hydraulic pump 8 is lowered in a normal travel time.

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 a steering force of a steering wheel of a vehicle, and more particularly to drive control of a hydraulic pump.

[0002]

2. Description of the Related Art A conventional power steering apparatus includes a hydraulic pump for generating hydraulic pressure in a hydraulic circuit by discharging hydraulic oil, a control valve for switching a hydraulic circuit and controlling a supply amount of hydraulic oil, and an output unit. It consists of a power cylinder and a steering device that converts the movement of the steering wheel in the rotational direction into the movement in the reciprocating direction. The hydraulic oil discharged by the hydraulic pump presses the piston in the power cylinder to control the steering. Assist is provided. As the hydraulic pump, those using an engine as a drive source and those using an electric motor are used.

[0003] Recently, the hydraulic pump has been constantly driven,
There is known a configuration in which the hydraulic pump is operated only when the power steering device requires hydraulic oil, thereby reducing the load on the hydraulic pump and improving fuel efficiency. However, there is a problem that it takes time until the supply amount of the hydraulic oil by the hydraulic pump reaches a certain supply amount, and there is a problem that the assist for the steering operation is not sufficiently performed during the rapid steering within this time period.

To solve such problems, Japanese Patent Application Laid-Open No. 61-85272 discloses an accumulator for accumulating hydraulic oil in a hydraulic circuit, and a pressure sensor for detecting the pressure in the accumulator. There is disclosed one that drives the electric motor until the pressure reaches a predetermined pressure when the pressure falls below the pressure value.

[0005]

According to the above prior art,
Although it is possible to compensate for the lack of oil pressure at the start of the electric motor by accumulating hydraulic oil, the pressure in the hydraulic circuit tends to fall below a predetermined value when steering is heavily used. It is in a state of being driven. When the number of times the electric motor is driven increases, the electric motor uses the power generated by the alternator as a power source.
There is a problem in that a load is applied to the alternator, and as a result, the engine load increases and fuel efficiency deteriorates.

[0006]

In order to solve the above problems, a power steering apparatus according to the present invention comprises a pump for discharging hydraulic oil, a driving device for driving the pump, and a hydraulic pump for accumulating hydraulic oil discharged from the pump. A pressure accumulator and a pressure detecting means for detecting the pressure in the accumulator, and a control unit for controlling the driving of the driving device based on the accumulated pressure of the accumulator. In a power steering device configured to increase a steering force applied to a steered wheel by oil and transmit the steering force to the steered wheel, the control unit reduces a vehicle speed based on an output signal from a pressure detecting unit and a traveling state of the vehicle. Based on the output signal from the deceleration detecting means for detecting the decelerated running of the vehicle, until the accumulated pressure of the accumulator reaches a predetermined pressure during the decelerated running of the vehicle. Wherein the drive control of the braking system.

A pump for discharging hydraulic oil, a driving device for driving the pump, a pressure accumulator for accumulating hydraulic oil discharged by the pump, and pressure detecting means for detecting a pressure in the pressure accumulator; A control unit for controlling the driving of the driving device based on the accumulated pressure value of the accumulator, and increasing the steering force applied to the steered wheels by the operating oil accumulated in the accumulator when the steering wheel is rotated. In the power steering device configured to transmit to the steered wheels, the control unit is based on an output signal from the pressure detection unit and a control signal to a fuel injection unit from an engine control unit that controls driving of the engine. When the fuel injection to the fuel injection means is cut off, the driving of the driving device is controlled until the accumulated pressure of the accumulator reaches a predetermined pressure. It is characterized in.

Further, the control unit reduces the voltage supplied to the drive device when the running speed of the vehicle is equal to or higher than a predetermined speed, based on an output signal from speed detecting means for detecting the running speed of the vehicle.

Further, the drive unit is characterized by comprising an engine mounted on the vehicle, and a clutch mechanism for connecting and disconnecting the engine and the pump based on an output signal from the control unit.

[0010]

FIG. 1 shows a first embodiment of the present invention. A power steering device 1 comprises a rack and pinion type steering device 2 and a power cylinder 3 provided on a rack shaft 2d thereof. And a control valve 5 for controlling supply and discharge of hydraulic oil to and from the power cylinder 3 via a supply and discharge circuit 4
A hydraulic circuit 6 for supplying and discharging hydraulic oil to and from the control valve 5, and a tank 7 provided in the hydraulic circuit 6 for storing hydraulic oil
And a hydraulic pump 8 for discharging hydraulic oil in a tank 7 and an accumulator 9 for accumulating hydraulic oil.

In the power steering apparatus 1, by steering the steering wheel 2a, rack teeth meshing with the pinion teeth 2b via a steering shaft 2c having one end connected to the steering wheel 2a and the other end formed with pinion teeth 2b. The steering force is transmitted to the rack shaft 2d where the 2e is formed, and hydraulic oil is supplied to one of the cylinder chambers 3a, 3b in the power cylinder 3 by the control valve 5 according to the rotation direction and the twist of the steering shaft 2c. At the same time, the other hydraulic fluid in the cylinder chambers 3a and 3b is discharged, and the hydraulic fluid urges a piston 3c provided on the rack shaft 2d to assist the steering force.

Next, the hydraulic circuit 6 will be described. The hydraulic circuit 6 includes a supply circuit 6a for supplying hydraulic oil to the control valve 5, and a discharge circuit 6b for discharging hydraulic oil from the control valve 5 to the tank 7. The hydraulic oil in the tank 7 is discharged by the hydraulic pump 8 to the supply circuit 6a, and is accumulated in the accumulator 9 via the check valve 10 that regulates the outflow direction of the hydraulic oil. The hydraulic pump 8 has a configuration in which an electric motor 11 driven by electric power generated by an alternator (not shown) is used as a drive source.

In the power steering device 1 according to the present invention, the accumulator 9 is provided with a pressure sensor 12 for measuring the pressure of the hydraulic oil accumulated in the accumulator 9, and the output signal of the pressure sensor 12 and the vehicle A normal traveling signal and a deceleration traveling from the deceleration detecting means 14 for determining whether the vehicle is traveling normally during acceleration or at a constant speed or traveling during deceleration while the vehicle speed is decreasing. The signals are input to a control unit 15 including a microprocessor and a memory, and the driving of the electric motor 11 is controlled. The deceleration detecting means 14 is a vehicle speed sensor 1 for detecting the speed of the vehicle.
This is a well-known means for detecting the deceleration of the vehicle based on the vehicle speed signal from the engine 3, the brake signal output when the brake is operated, the engine speed signal, and the like.

The operation of the power steering device 1 having the above configuration will be described. When the hydraulic pump 8 is driven by the electric motor 11 based on the output signal from the control unit 15, the working oil is discharged to the supply circuit 6a and accumulated in the accumulator 9.

The control unit 15 controls the driving of the electric motor 11 based on the pressure in the accumulator 9 from the pressure sensor 12 and the output signal from the deceleration detecting means 14. As shown in FIG. 2, in step 101, the control unit 15
When a normal driving signal indicating normal driving is detected, the routine proceeds to step 103, where normal control is performed. When a deceleration traveling signal indicating deceleration traveling is detected, the routine proceeds to step 102, where deceleration control is performed.

Next, the normal control will be described with reference to the flowchart of FIG. In step 201, the pressure P in the accumulator 9 is detected by the pressure sensor 12,
In step 202, it is determined whether the pressure P is equal to or lower than the lower limit value P1. When it is determined that the pressure P is equal to or lower than the lower limit value P1, the routine proceeds to step 203, where the flag 1 is set, and the electric motor 11 is driven in step 204. When it is determined in step 202 that the pressure P is equal to or higher than the lower limit value P1, the process proceeds to step 205, and it is determined whether the flag 1 is set. If it is determined that the flag 1 is set, the routine proceeds to step 206, where it is determined whether or not the pressure P has reached the upper limit value P2. Step 206
If it is determined that the pressure P has not reached the upper limit value P2, the routine proceeds to step 203, where the electric motor is continuously driven. If it is determined in step 206 that the pressure P has reached the upper limit value P2, the process proceeds to step 207, where the electric motor is stopped, and the flag 1 is returned in step 208. Step 2
If it is determined that the flag 1 is not set at 05, the routine is skipped. FIG. 4 shows the electric motor 1 in the normal control.
1 shows the relationship between the drive of No. 1 and the pressure in the accumulator 9.

The lower limit value P1 and the upper limit value P2 are values obtained by experiments. Assuming that the maximum hydraulic pressure in the hydraulic circuit is 100%, the lower limit value P1 is a pressure required for an urban area and is higher than the maximum hydraulic pressure. The upper limit value P2 is a pressure required for sudden steering or danger avoidance and is approximately 8% of the maximum hydraulic pressure.
0%.

Next, the deceleration control will be described. During deceleration driving, the engine is driven by coasting of the vehicle, so that even if an electric load is applied to the alternator, there is no effect on fuel efficiency. During this deceleration running,
The control unit 15 drives the electric motor 11 until the relief set pressure P3, which is a pressure value higher than the upper limit value P2, is reached, or until a normal traveling signal is input from the deceleration detecting means 14, and the accumulated pressure in the accumulator 9 is increased. I do.

As shown in FIG. 5, in step 301, a signal from the deceleration detecting means 14 is detected, and in step 302, the pressure P in the accumulator 9 is detected. Step 3
03, it is determined whether or not the vehicle is running at a reduced speed.
It is determined whether or not the pressure P has reached the relief set pressure P3. If it is determined in step 305 that the pressure has not reached the relief set pressure P3, the process proceeds to step 305, where the flag 2 is set, and the electric motor is driven in step 306. In step 303, it is determined that the vehicle is not running at a reduced speed, or in step 304
When it is determined that the pressure P has reached the relief pressure P3, the routine proceeds to step 307, where it is determined whether the flag 2 is set. If the flag 2 is set, the process proceeds to step 308 to stop the electric motor, and returns the flag 2 in step 309. If it is determined in step 307 that the flag 2 is not set, Get out of the routine. FIG. 6 shows a relationship between the driving of the electric motor 11 and the pressure in the accumulator 9 in the deceleration control. The electric motor 11 is driven at the time when the pressure in the accumulator 9 is equal to or less than P3 and the vehicle is traveling at a reduced speed.

Further, as shown in FIG. 7, the control unit 15 sets the motor rotation speed of the electric motor 11 to the normal rotation speed N1 when the vehicle speed is low and the hydraulic pump 8 based on the output signal from the vehicle speed sensor 13. The hydraulic oil is discharged to the hydraulic circuit 6 by the vehicle speed, and the vehicle speed becomes a predetermined value (V
1: vehicle speed that requires little assistance)
The supply voltage to the electric motor 11 is reduced to N2, which is lower than the normal rotation N1, so that the hydraulic pump 8 controls the discharge amount of hydraulic oil to the hydraulic circuit 6 to be reduced. When the vehicle speed is equal to or higher than a predetermined value, the discharge amount of the hydraulic oil is reduced, but when the vehicle speed is equal to or higher than the predetermined value, almost no assistance is required for steering. At the same time, since the minimum pressure required for assist is always stored in the accumulator 9, assist shortage does not occur.

In the power steering apparatus 1 according to the present invention, during normal driving, normal control is performed, and when the pressure in the accumulator 9 is reduced by steering of the steering wheel 2a and becomes lower than the lower limit value P1, the upper limit value P2 is reached. Since the electric motor 11 is driven to drive the hydraulic pump 8 until then, the hydraulic oil having the lower limit value P1 or more can always be stored in the accumulator 9 without any influence on the steering of the steering wheel 2a.

In addition, during deceleration traveling, since the operation is performed so as to secure sufficient hydraulic oil in the accumulator 9, even if the steering of the steering wheel 2a is frequently used, the pressure may be lower than the lower limit value P1.
Can be avoided as much as possible.
Can be reduced. During deceleration driving, the engine is driven by the coasting of the vehicle. Therefore, even if the electric motor 11 is driven, only part of the engine output during the coasting is consumed for driving the alternator. Fuel economy deterioration due to driving of the motor 11 can be suppressed.

Further, in a vehicle speed region where little assistance is required, the supply voltage to the electric motor 11 is reduced.
Fuel economy deterioration due to driving of the electric motor drive 11 can be suppressed.

Further, on a sloping road or the like, a part of the output of the engine is lost due to the drive of the alternator, so that the effectiveness of the engine brake is improved.

FIG. 8 shows a second embodiment of the present invention, which is applied to a vehicle having an engine control unit for controlling fuel injection by an injector. A control signal for controlling the injection (injection time and injection amount) is always input, and the drive of the electric motor 11 is controlled based on the control signal and the output signal from the pressure sensor 12.

The control signal is, as shown in FIG. 9, an engine speed sensor 17 for detecting the engine speed.
And a water temperature sensor 18 for detecting the temperature of the engine cooling water for cooling the surroundings of the engine cylinder, a vehicle speed sensor 13, and a signal from an idle switch 19 which is turned on when the throttle is fully closed, to determine the engine operating state and traveling. The state is detected, and when the vehicle speed is equal to or higher than a predetermined vehicle speed, the idle switch 19 is turned on, and the engine speed is equal to or higher than the predetermined speed, the fuel injection by the injector a is stopped (fuel cut). Is a signal used to restart fuel injection by the injector a when even one of them is not satisfied (recovery). Note that the engine speed, which is a condition for fuel cut, is appropriately changed depending on the water temperature for the predetermined engine speed.

The control unit 15 receives a control signal from the engine control unit 16 and determines that the vehicle is traveling normally if fuel injection is being performed by the injector a, as in the first embodiment. Normal control is performed. If the fuel injection by the injector a is cut, it is determined that the vehicle is running at a reduced speed,
The deceleration control is performed in the same manner as in the first embodiment.

In the second embodiment, the control signal for controlling the fuel injection of the injector a output from the engine control unit 16 is used for discriminating between the normal control and the deceleration control.
The present invention can be easily applied to an engine using an engine that performs fuel injection by using a fuel injection device.

FIG. 10 shows a third embodiment of the present invention.
0 uses an engine 21 connected to the hydraulic pump 8. The clutch mechanism 20 connects and disconnects the engine 21 and the hydraulic pump 8 based on an output signal from the control unit 15 and controls driving of the hydraulic pump 8. The control unit 15 is configured to perform the same control as in the first or second embodiment based on the output signal from the pressure sensor 12 and the output signal from the vehicle speed sensor 13.

In the third embodiment, since the hydraulic pump 8 is driven by the output of the engine, the size of the alternator and the battery can be reduced.
As in the first and second embodiments, it is possible to improve the fuel efficiency and the effectiveness of the engine brake.

[0031]

As described above, according to the present invention, the number of times of driving the pump during normal running can be reduced by positively driving the pump during deceleration running in which the engine is driven by inertia. The fuel consumption can be prevented from deteriorating. Also, by actively applying a load to the engine during deceleration traveling, the effectiveness of the engine brake on a slope or the like can be enhanced, and the friction of a brake shoe or the like can be suppressed.

[Brief description of the drawings]

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

FIG. 2 is a flowchart of overall control according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating normal control in the overall control of FIG. 2;

FIG. 4 is an explanatory diagram showing a relationship between an electric motor and pressure in normal control.

FIG. 5 is a flowchart illustrating deceleration control in the overall control of FIG. 2;

FIG. 6 is an explanatory diagram showing a relationship between an electric motor and pressure in deceleration control.

FIG. 7 is an explanatory diagram showing a relationship between an electric motor and a vehicle speed.

FIG. 8 is an overall configuration diagram of a power steering apparatus according to a second embodiment of the present invention.

FIG. 9 is a block diagram showing a relationship between the engine control unit and the control unit in FIG. 7;

FIG. 10 is an overall explanatory diagram of a power steering device according to a third embodiment of the present invention.

[Brief description of reference numerals]

 Reference Signs List 1 power steering device 2 steering device 3 power cylinder 4 supply / discharge circuit 5 control valve 6 hydraulic circuit 7 tank 8 hydraulic pump 9 accumulator 11 electric motor 13 vehicle speed sensor 14 deceleration detecting means 15 control unit

Claims (4)

[Claims] A pump that discharges hydraulic oil, a driving device that drives the pump, a pressure accumulator that accumulates hydraulic oil discharged by the pump, and pressure detection means that detects a pressure in the pressure accumulator. A control unit for controlling the driving of the driving device based on the accumulated pressure value of the accumulator, and increasing the steering force applied to the steered wheels by the operating oil accumulated in the accumulator when the steering wheel is rotated. In the power steering device configured to transmit to the steered wheels, the control unit includes an output signal from the pressure detection unit and a deceleration detection unit that detects deceleration traveling of the vehicle whose vehicle speed decreases based on the traveling state of the vehicle. And controlling the drive of the driving device until the accumulated pressure of the accumulator reaches a predetermined pressure when the vehicle is running at a reduced speed. Power steering device. 2. A pump for discharging hydraulic oil, a driving device for driving the pump, a pressure accumulator for accumulating hydraulic oil discharged by the pump, and pressure detecting means for detecting a pressure in the pressure accumulator; A control unit for controlling the driving of the driving device based on the accumulated pressure value of the accumulator, and increasing the steering force applied to the steered wheels by the operating oil accumulated in the accumulator when the steering wheel is rotated. In the power steering device configured to transmit to the steered wheels, the control unit is based on an output signal from the pressure detection unit and a control signal to a fuel injection unit from an engine control unit that controls driving of the engine. Controlling the driving of the driving device until the accumulated pressure of the accumulator reaches a predetermined pressure when fuel is cut into the fuel injection means. A power steering device characterized by the following. 3. The control unit according to claim 2, wherein the control unit reduces a supply voltage to the driving device when the running speed of the vehicle is equal to or higher than a predetermined speed, based on an output signal from speed detecting means for detecting the running speed of the vehicle. The power steering device according to claim 1 or 2, wherein 4. The drive device according to claim 1, further comprising an engine mounted on a vehicle, and a clutch mechanism for connecting and disconnecting the engine and the pump based on an output signal from the control unit. The power steering apparatus according to any one of claims 1 to 3.