JPH0647385B2 - Vehicle power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle power steering system, and more particularly to a vehicle power steering system having a rotary electric motor as a drive source.

[Prior art]

Conventionally, in this type of vehicle power steering apparatus, as disclosed in, for example, Japanese Patent Application Laid-Open No. 57-201762, the rotary electric motor is driven only when it is necessary to assist the operation of the steering wheel of the vehicle. There are things I tried to do.

[Problems to be solved by the invention]

However, in such a configuration, if the rotary electric motor is stopped while the steering wheel is being operated, the steering feeling suddenly becomes heavy, which causes a feeling of strangeness.

Therefore, in order to cope with such a situation, the present invention intends to stop the rotary electric motor in the vehicle power steering device under the substantial neutral position of the steering wheel.

[Means for solving problems]

In solving such problems, the structural features of the present invention are as follows.
As illustrated in FIG. 1, a steering mechanism 1 that travels the steered wheels 2 in one direction (or another direction) in response to a turning operation of the steering wheel 1a of the vehicle in one direction (or another direction),
A fluid pump 4 that is driven by the rotary electric motor 3 to generate a pressure fluid, and a piston 5d that is slidably fitted in the cylinder 5a to form both chambers 5b and 5c.
When fluid pressure is generated in one (or the other) of 5c, the piston 5d is slid toward the other (or one) of the two chambers 5b, 5c, and the other direction (or one direction) of the steering wheel 1a.
Of the power cylinder 5 for assisting the turning operation of the steering wheel 1a, and the twist amount of the steering shaft 1b that is provided coaxially with the steering shaft 1b of the steering handle 1a and is accompanied by the turning operation of the steering handle 1a in one direction (or the other direction). The servo valve means 6 for applying the amount of pressure fluid from the fluid pump 4 to the other (or one) of the two chambers 5b and 5c of the power cylinder 5, and both chambers of the power cylinder 5 when in the first switching state. Both chambers 5 of the power cylinder 5 when the second switching state is achieved by shutting off 5b and 5c
Electrical switching means 7 for allowing communication between b and 5c, vehicle speed detection means 8a for detecting the traveling speed of the vehicle and generating it as a vehicle speed signal, and generating a vehicle speed determination signal when the value of the vehicle speed signal is smaller than the set vehicle speed value. If the value of the vehicle speed signal is larger than the set vehicle speed value, the vehicle speed determination means 8b for extinguishing the vehicle speed determination signal, and the first output signal required for driving the rotary electric motor 3 in response to the generation of the vehicle speed determination signal Is generated and applied to the rotary electric motor 3, and the second output signal necessary for the first switching state of the electrical switching means 7 is made to disappear, and the first output signal is made to disappear in response to the disappearance of the vehicle speed determination signal. In addition to generating the second output signal, the electrical switching means 7 is generated.
Output signal generating means 9 applied to the steering wheel 1a, a turning state detecting means 9a for detecting the turning state of the steering wheel 1a and generating a turning state detection signal, and the value of the turning state detection signal is substantially neutral to the steering wheel 1a. And a neutral state determining means 9b for generating a neutral state determination signal when the state corresponds to the state and extinguishing the neutral state determination signal when the value of the turning state detection signal does not correspond to the substantially neutral state of the steering wheel 1a. The signal generating means 9 eliminates the first output signal and produces the second output signal in response to the disappearance of the vehicle speed discrimination signal and the generation of the neutral state discrimination signal, and causes the electrical switching means 7 to operate at the second side. This is because the switching state is set.

[Action effect]

With the above configuration of the present invention, therefore, when the vehicle is traveling straight ahead at a speed lower than the set vehicle speed value, the steering handle 1a is rotated in one direction (or the other direction) to operate the steering mechanism 1. When the steered wheels 2 are steered in one direction (or in the ground direction), the output signal generation means 9 outputs the vehicle speed determination signal from the vehicle speed determination means 8b, and the second output signal disappears. To generate the first output signal, and the fluid pump 4
Is driven by the rotary electric motor 3 to generate pressure fluid, and the electric switching means 7 is in the first switching state in the power cylinder 5
Since the communication between the two chambers 5b and 5c is cut off, the power cylinder 5 cooperates with the servo valve means 6 to assist the turning operation of the steering handle 1a.

In this state, when the traveling speed of the vehicle is higher than the set vehicle speed value, the vehicle speed discriminating means 8b erases the vehicle speed discriminating signal, but the neutral state discriminating means 9b keeps the neutral state discriminating signal extinguished. The output signal generating means 9 maintains the generation of the first output signal under the disappearance of the second output signal. After that, when the steering wheel 1a enters the neutral state, the neutral state determination means 9b cooperates with the rotation state detection means 9a to generate a neutral state determination signal, and the output signal generation means 9 disappears the first output signal. At the same time, the second output signal is generated, and the rotary motor 3 stops the fluid pump 4 due to the stop, and the electrical switching means 7 enters the second switching state to allow the communication between the chambers 5b and 5c.

Thus, even if the traveling speed of the vehicle is higher than the set vehicle speed value during the turning operation of the steering wheel 1a, the rotary electric motor 3 is stopped and both chambers of the power cylinder 5 are returned after the steering wheel 1a is returned to the neutral state. Since 5b and 5c are communicated with each other, the fluid in the left chamber 5b (or the right chamber 5c) of the power cylinder 5 can flow into the right chamber 5c (or the left chamber 5b) even if the fluctuation occurs due to the stop of the fluid pump 3. Therefore, no negative pressure is generated in the right chamber 5c (or the left chamber 5b), and the steering operation of the steering handle 1a is not affected at all.
Therefore, the steering feeling does not feel uncomfortable.

Further, in such a case, even if the piston 5d of the power cylinder 5 moves, the two chambers 5b and 5c are in communication with each other, so that the piping resistance can be kept small even when the viscosity of the fluid is large at low temperatures. As a result, unnecessary force is not applied to the steering wheel 1a, and the steering load resistance at the time of steering for emergency avoidance is suppressed to be small. Furthermore, both rooms 5
Since a negative pressure is not generated in b and 5c, a special effect is produced that bubbles are not generated in both chambers 5b and 5c.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
The figure shows a power steering apparatus for a vehicle according to the present invention. The power steering apparatus includes a steering mechanism 10. The steering mechanism 10 moves the steering shaft 12 leftward (or rightward) when the steering wheel 11 is turned leftward (or rightward). 12a and rack bar 13 according to the rotation to
The piston 21 of the power cylinder 20 is slid leftward (or rightward) in the power cylinder 20 while meshing with the steering wheel 14 to steer the steering wheel 14 leftward (or rightward). There is.

The power steering apparatus includes a DC electric motor 30, a constant capacity oil pump 40 connected to the DC electric motor 30, a servo valve 50 coaxially mounted on the steering shaft 12, and an electromagnetic opening / closing valve 60. The oil pump 40 is the DC motor 3
The oil passage P is driven from the reservoir 40a by being driven at a rotational speed of 0.
The hydraulic oil is pumped through 1 and discharged into the oil passage P2 as pressure oil. The servo valve 50 connects the oil passages P2 and P5 to the oil passages P3 and P4 by turning the steering shaft 12 to the left, and steers the pressure oil applied from the oil pump 40 through the oil passage P2. The throttling oil passage P3 is applied to the right chamber 23 of the power cylinder 20 in an amount according to the turning force of the shaft 12 to the left, and the remaining pressure oil is discharged into the reservoir 40a through the oil passage P5 and the power cylinder 20 is discharged. The pressure oil in the left chamber 22 is received through the oil passage P4 and discharged from the oil passage P5 into the reservoir 40a. Further, the servo valve 50 connects the oil passages P2 and P5 to the oil passages P4 and P3 by rotating the steering shaft 12 to the right.
To the oil passage P2 from the oil pump 40.
Through the throttle oil passage P4 to the left chamber 22 of the power cylinder 20, and the residual pressure oil is passed through the oil passage P5. The pressure oil in the right chamber 23 of the power cylinder 20 is received through the oil passage P3 and discharged from the oil passage P5 into the reservoir 40a while being discharged into the reservoir 40a.

This means that the power cylinder 20 cooperates with the servo valve 50 to slide the piston 21 to the right (or to the left) under the pressure oil generated in the left chamber 22 (or the right chamber 23) to steer the steering wheel. This means assisting the turning operation of 11 to the right (or the left). However, when the steering handle 11, that is, the steering shaft 12, is in the neutral state, the servo valve 50 connects the oil passages P2, P3, and P4 to the oil passage P5. The electromagnetic on-off valve 60 is of a normally closed type and is interposed between the intermediate portions of the oil passages P3 and P4. Then, the solenoid on-off valve 60 is closed under the demagnetization of its solenoid 61 to close both oil passages P3 and P4.
The communication between the respective intermediate portions of the above is cut off by the excitation of the solenoid 61 to allow the communication between the respective intermediate portions of the oil passages P3 and P4.

The power steering apparatus has a vehicle speed sensor 70a, an angle sensor 70b, and an electric control circuit 70 connected to both sensors 70a and 70b. The vehicle speed sensor 70a detects the vehicle speed of the vehicle and detects the vehicle speed. Generates a series of pulse signals at a frequency proportional to
To the left (or right) of the neutral state (steering handle 1
The rotation angle with reference to the neutral state (1) is detected and generated as an analog angle voltage.

As shown in FIG. 3, the electric control circuit 70 includes a frequency-voltage converter 71 (hereinafter, referred to as F-) connected to the vehicle speed sensor 70a.
V converter 71) and each A-D converter 7 connected to the F-V converter 71 and the angle sensor 70b.
2, 73 and a microcomputer 75 connected to both of the A / D converters 72, 73, and the FV converter 71 is an analog circuit in which the frequency of each pulse signal from the vehicle speed sensor 70 is proportional to this. Convert to vehicle speed voltage. The A-D converter 72 converts the analog vehicle speed voltage from the F-V converter 71 into a digital vehicle speed voltage (hereinafter, digital vehicle speed voltage Vs
Called). The A / D converter 73 is the angle sensor 7
The analog angle voltage from 0b is converted into a digital angle voltage (hereinafter, referred to as digital angle voltage Vθ).

The microcomputer 75 repeatedly executes a computer program stored therein in advance in cooperation with both AD converters 72 and 73 in accordance with the flowchart shown in FIG. 4, and during this execution, both DAs are executed. Converter 7
Various kinds of arithmetic processing required for the control of Nos. 6 and 77 are performed. In this case, when the microcomputer 75 generates a digital excitation voltage required for exciting the solenoid 61, as will be described later, the DA converter 76 converts the digital excitation voltage into an analog excitation voltage. When the microcomputer 75 generates a digital rotation voltage required to drive the DC motor 30, as will be described later, the DA converter 77 converts the digital rotation voltage into an analog rotation voltage.

The power amplifier 78 amplifies the analog excitation voltage from the DA converter 76 and generates it as an amplified excitation voltage. The power amplifier 79 amplifies the analog rotation voltage from the DA converter 77 and generates it as an amplified rotation voltage. In other words, the solenoid 61 is excited in response to the amplified excitation voltage from the power amplifier 78, and the DC motor 30 rotates in response to the amplified rotation voltage from the power amplifier 79.

In the present embodiment configured as described above, the vehicle is placed in the straight running state and the device of the present invention is placed in the operating state. At this time, if the vehicle speed of the vehicle is equal to or lower than the first set voltage Vs1 (corresponding to, for example, the first set vehicle speed = 80 km / h), the microcomputer 75 starts in step 81 of the computer program, and then in step 81. , The vehicle speed sensor 70a and the FV converter 71 in cooperation with the digital vehicle speed voltage V generated from the AD converter 72.
The digital angle voltage Vθ generated from the A / D converter 73 is read in cooperation with s and the angle sensor 70b, and in step 82, it is determined to be “NO” based on Vs ≦ Vs1. The first set fourth vehicle speed Vs1 is stored in the microcomputer 75 in advance.

While repeating the determination of “NO” in step 82,
When the vehicle speed of the vehicle is higher than the first set vehicle speed (80 km / h), the microcomputer 75 determines “YES” in step 82, and in step 83, step 81
It is determined to be "YES" based on the first digital angle voltage V? In this case, the set angle voltage Vθ1 is equal to the play angle (eg, 10) to the left (or right) with respect to the neutral direction of the steering wheel 11.
)) And is stored in the microcomputer 75 in advance.

Thereafter, when the microcomputer 75 generates the digital excitation voltage in step 83a and maintains the disappearance of the digital rotation voltage in step 83b, the DA converter 7
6 generates an analog excitation voltage in response to the digital excitation voltage, the power amplifier 78 generates an amplified excitation voltage, the electromagnetic opening / closing valve 60 is opened by the excitation of the solenoid 61, and both the left and right chambers 22, 23 of the power cylinder 20 are opened. Communication is established via the oil passages P4 and P3. At this time, the DC motor 30 remains stopped. When the calculation in step 83b is completed in this manner, the microcomputer 75 causes the step 8
In step 4, as in step 81, the digital vehicle speed voltage Vs and the digital angle voltage Vθ are read, and Vs> second set vehicle speed voltage Vs2 (for example, second set vehicle speed = 70 km
(Corresponding to / h), it is determined to be “NO” in step 85. However, the second set vehicle speed voltage Vs2 is already stored in the microcomputer 75.

Then, during the repetition of the determination of “NO” in step 85, the vehicle is set to the second set vehicle speed (70 km /
If it is less than h), the microcomputer 75 determines “YES” in step 85, and in step 86,
Similar to the case of step 83, "YES" is determined, the digital excitation voltage is extinguished in step 86a, and the digital rotation voltage is generated in step 86b. Then, the DA converter 76 extinguishes the analog excitation voltage in response to the extinction of the digital excitation voltage from the microcomputer 75, and the power amplifier 78 extinguishes the amplified excitation voltage. As a result, the solenoid opening / closing valve 60 is closed by demagnetizing the solenoid 61, and the left and right chambers 22, 2 of the power cylinder 20 are closed.
The communication between 3 is cut off.

On the other hand, the DA converter 77 generates an analog rotation voltage in response to the digital rotation voltage from the microcomputer 75, the power amplifier 79 generates an amplification circuit voltage, the DC motor 30 rotates, and the oil pump 40 operates. When driven, the hydraulic oil in the reservoir 40a is pumped up and used as pressure oil in the oil passage P.
Dispense into 2. At this time, since the steering wheel 11 is in the neutral state, the pressure oil in the oil passage P2 is discharged from the oil passage P5 into the reservoir 40a through the servo valve 50.

When the circulation calculation of both steps 81 and 82 is maintained during the repetition of the calculation of the microcomputer 75 associated with the straight running state of the vehicle as described above, the vehicle speed of the vehicle is the first set vehicle speed (80 km / h). In the following, and based on the calculation results of both steps 86a and 86b, the oil pump 40 is driven by the DC electric motor 30 to generate pressure oil in a state where communication between the left and right chambers 22 and 23 of the power cylinder 20 is cut off. ing. In this case, when the steering handle 11 is rotated leftward, the steering shaft 12 is rotated leftward in response to the rotation with respect to the steering handle 11 and the piston 21 of the power cylinder 20 is slid to the left chamber 22 side. The traveling wheels 14 are steered to the left. Further, the servo valve 50 transfers the pressure oil applied from the oil pump 40 through the oil passage P2 to the steering shaft 1
2 is applied to the inside of the right chamber 23 of the power cylinder 20 through the throttle oil passage P3 in an amount corresponding to the rotational force of 2 to the left, and the residual pressure oil and the pressure oil applied from the existing chamber 22 through the oil passage P4 are applied. Oil passage P
5 to be discharged into the reservoir 40a, and the power cylinder 20
Moves the piston 21 to the left according to the pressure difference between the left and right chambers 22 and 23 to assist the turning operation of the steering handle 11 in the left direction.

Further, when the vehicle speed of the vehicle increases above the first set vehicle speed (80 km / h) during the turning operation of the steering handle 11 to the left under the circulation calculation of both steps 81 and 82, the microcomputer 75 determines "YES" based on Vs> Vs1 at step 82, and step 8
In step 3, it is determined to be "NO" based on Vθ> Vθ1, and thereafter, by repeating the circulation calculation in each of steps 81, 82, and 83, the assisting action for the turning operation of the steering handle 11 to the left is repeated as described above. Bring

After that, when the vehicle goes straight ahead due to the return of the steering wheel 11 to the neutral state, the microcomputer 75 at step 83 determines “YES” based on Vθ ≦ Vθ1.
, The digital excitation voltage is generated in step 83a, and the digital rotation voltage is extinguished in step 83b. As a result, the solenoid opening / closing valve 60 is excited by the solenoid 61 in the same manner as described above, so that both the left and right chambers 2 of the power cylinder 20 are excited.
The direct current electric motor 30 stops the oil pump 40 by the stop in the same manner as described above while permitting communication between the second and the second electric motors.

In other words, even if the vehicle speed of the vehicle is higher than the first set vehicle speed (80 km / h) as described above, the steering handle 11 is changed from the turning operation state to the neutral state and the two oil passages P2 and P5.
Since the electromagnetic open / close valve 60 allows communication between the left and right chambers 22 and 23 after the servo valve 50 is fully opened, the oil pump 40 is stopped by stopping the DC motor 30. Oil pump 40
Even if the discharge pressure of No. 2 suddenly changes due to the stop of the oil pump 40, the steering handle 11 in the neutral state is not affected at all and the steering feeling is not uncomfortable. In such a case, since the left and right chambers 22 and 23 of the power cylinder 20 communicate with each other as described above, even if the piston 21 moves, the hydraulic pressure in the left and right chambers 22 and 23 circulates in the power cylinder 20. Air bubbles can be prevented.

Further, when the steering wheel 11 is rotated leftward while the microcomputer 75 is performing the circulation calculation of both steps 84 and 85 under the straight traveling state of the vehicle as described above, Is the second set vehicle speed (70
km / h) and both steps 83a,
Since the DC electric motor 30 is stopped based on the communication between the left and right chambers 22 and 23 of the power cylinder 20 based on the calculation result in 83b, the steering wheel 11 is not assisted. This means that the steering interval with respect to the steering wheel 11 is heavy.

Further, when the vehicle speed of the vehicle decreases below the second set vehicle speed (70 km / h) during the turning operation of the steering handle 11 to the left under the circulation calculation of both steps 84 and 85, the microcomputer 75 determines "YES" based on Vs <Vs2 in step 85, and then step 86
At V.sub..theta.> V.theta.1, it is determined to be "NO", and thereafter, the assisting action on the steering wheel 11 is maintained in the stopped state in the same manner as described above by repeating the circulation calculation of the steps 84, 85, 86.

After that, when the vehicle is in the straight traveling state due to the return of the steering wheel 11 to the neutral state, the microcomputer 75 at step 86 determines “YES” based on Vθ ≦ Vθ1.
Then, based on the calculation of both steps 86a and 86b, the device of the present invention is put in the assisting ready state as described above. In other words, even if the vehicle speed of the vehicle is lower than the second set vehicle speed (70 km / h) as described above, the left and right chambers of the power cylinder 20 after the steering handle 11 has changed from the turning operation state to the neutral state. Since the communication between 22 and 23 is cut off and the oil pump 40 is driven by the drive of the DC motor 30, even if the discharge pressure of the oil pump 40 suddenly changes by the drive of the oil pump 40, it becomes a neutral state. There is no influence on the steering wheel 11 without any influence on the steering feeling. As described above, the DC motor 30 has a vehicle speed of substantially 70 km / h.
Since it is driven only when, it also helps save power.

In the above-described operation, the case where the steering handle 11 is rotated leftward has been described. However, the present invention is not limited to this, and the case where the steering handle 11 is rotated rightward,
The same effect as the above can be achieved.

Further, in the above embodiment, the angle sensor 70b is adopted as the means for detecting the neutral state of the steering wheel 11, but the invention is not limited to this, and for example, an angular velocity sensor or a torque sensor is adopted instead of the angle sensor 70b. The steering wheel 11 is operated by an angular velocity sensor or a torque sensor.
The neutral state may be detected.

Further, in the embodiment of the present invention, a variable displacement oil pump may be adopted instead of the constant displacement oil pump 40, and the rotation speed of the DC motor 30 may be reduced instead of stopping the DC motor 30. You may allow it.

[Brief description of drawings]

1 is a block diagram showing the configuration of the invention described in the claims, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a detailed circuit diagram and an electric control circuit of FIG. FIG. 4 is a flow chart showing the operation of the microcomputer shown in FIG. Explanation of reference numerals 10 ... Steering mechanism, 11 ... Steering handle, 12 ... Steering shaft, 14 ... Steering wheel, 20 ... Power cylinder, 21
...... Piston, 22 ...... left chamber, 23 ...... right chamber, 30 ......
DC motor, 40 ... Oil pump, 50 ... Servo valve, 60 ... Electromagnetic on-off valve, 61 ... Solenoid, 70 ...
... electric control circuit, 71 ... FV converter, 72,73 ...
... A-D converter, 70a ... vehicle speed sensor, 70b ... angle sensor, 75 ... microcomputer 7, 76, 7
7 ... DA converter, 78, 79 ... Power amplifier.

Front page continuation (72) Inventor Masahiko Suzuki, 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd. (56) Reference JP-A-57-60972 (JP, A) JP-A-58-139868 ( JP, A) JP 57-158162 (JP, A)

Claims (1)

[Claims] 1. A steering mechanism for traveling a steering wheel in one direction (or another direction) in response to a turning operation of a steering wheel of a vehicle in one direction (or another direction), and a pressure driven by a rotary electric motor. A fluid pump for generating a fluid, and a piston that is slidably fitted in a cylinder to form both chambers. When a fluid pressure is generated in one (or the other) of the chambers, the pistons are A power cylinder that slides toward the other side (or one side) of the chamber to assist the turning operation in the other direction (or one direction) of the steering handle; and a power cylinder that is provided coaxially with the steering shaft of the steering handle. The amount of the pressure fluid from the fluid pump is throttled according to the amount of twist of the steering shaft due to the turning operation of the steering wheel in one direction (or the other direction), and is applied to the other (or one) of both chambers of the power cylinder. Servo valve means , Electrical switching means for shutting off both chambers of the power cylinder when the first switching state is set, and permitting communication between both chambers of the power cylinder when the second switching state is set; Vehicle speed detection means for generating a signal, and a vehicle speed determination signal that generates a vehicle speed determination signal when the value of the vehicle speed signal is smaller than a set vehicle speed value, and a vehicle speed determination signal that disappears when the value of the vehicle speed signal is greater than the set vehicle speed value Means for generating a first output signal required for driving the rotary motor in response to the generation of the vehicle speed determination signal and applying the first output signal to the rotary motor, and a second output signal required for the first switching state of the electrical switching means. The output signal is extinguished, the first output signal is extinguished in response to the extinction of the vehicle speed determination signal, and the second output signal is extinguished.
An output signal generating means for generating an output signal and giving it to the electrical switching means; a rotating state detecting means for detecting a rotating state of the steering wheel and generating a rotating state detecting signal; A neutral state determination signal is generated when the value corresponds to the substantially neutral state of the steering wheel, and the neutral state determination signal is extinguished when the value of the turning state detection signal does not correspond to the substantially neutral state of the steering wheel. State determining means is provided, and the output signal generating means causes the second output signal to occur while eliminating the first output signal in response to the disappearance of the vehicle speed determination signal and the generation of the neutral state determination signal, A power steering apparatus for a vehicle, wherein the electric switching means is set to the second switching state.