JP2501564B2 - Vehicle power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention aims to reduce the operating force required for steering a vehicle.
The present invention relates to a power steering device for a vehicle, which is configured to apply an assisting force to a steering mechanism.

(Prior Art) As one of vehicle power steering devices, for example, as shown in Japanese Patent Application Laid-Open No. 60-139572, in addition to the need for a larger steering force as the vehicle speed increases, It is known that a larger steering force is required as the steering angle of the vehicle becomes larger.

In the power steering device that adjusts the operation force required for steering in such a mode, normally, the working pressure oil discharged from the oil pump is an auxiliary device including a power cylinder and the like via the valve portion of the steering control means. In addition to being supplied to the force generation unit, it is supplied to the reaction force generation unit provided in the above-mentioned steering control unit via the pressure oil amount adjustment unit (proportional solenoid valve or the like). The steering control means controls the supply / discharge amount of the operating pressure oil to / from the auxiliary force generating portion according to the steering input given from the steering wheel, while the pressure oil amount adjusting means responds to the control signal from the predetermined control portion. Change the effective cross-sectional area of the hydraulic oil passage,
Adjust the amount of working pressure oil supplied to the reaction force generator. As a result, the assisting force generating section generates a steering assisting force according to the steering input, the steering mechanism operates to steer the wheels, and the reaction force generating section is supplied from the pressure oil amount adjusting means. A steering reaction force that controls the operation of the valve portion of the steering control means is generated according to the amount of hydraulic oil. The larger the steering reaction force obtained by the reaction force generation unit, the larger the steering force on the steering wheel needs to be.

Then, in such a case, the control unit, in order to increase the amount of working pressure oil supplied to the reaction force generation unit, the higher the vehicle speed and the larger the steering angle of the vehicle, The pressure oil amount adjusting means is controlled. In this way, the pressure oil amount adjusting means is controlled to change the amount of operating pressure oil supplied to the reaction force generating portion, whereby the torque required to rotate the steering wheel, that is, the torque required for steering is, for example, As shown by the alternate long and short dash line in FIG. 8, when the vehicle is traveling at the medium vehicle speed v ₂ , it is greater than when the vehicle is traveling at the low vehicle speed v _1. In addition, the vehicle speed is higher than when traveling at medium speed v _2.
v becomes large towards when running at _3, and, in any case, is assumed to increase with increasing steering angle.

(Problems to be Solved by the Invention) However, in the power steering device configured as described above, it is necessary that the steering force with respect to the steering handle is increased as the steering angle is increased. When a large steering angle is taken, the steering wheel operation may be too heavy. When the vehicle travels at high speed, the steering angle is not usually large, and when the vehicle travels at low speed, the torque required for steering is generally small. It is not so inconvenient to make the steering wheel operation heavy when the steering wheel is taken, but when the vehicle is traveling at medium speed, if the steering wheel operation is made heavy when the large steering angle is taken, the burden on the driver will be increased. Since it becomes large, it is desired that the steering wheel operation when the large steering angle is taken should not be too heavy.

However, in order to make the steering handle operation light when a large steering angle is taken, if the torque required for steering when the vehicle is running at medium speed is made small as a whole, a small steering angle is taken. In this case, the inconvenience of excessive reduction due to the response through the steering wheel during steering occurs.

In view of such a point, the present invention changes the torque required for steering in the vehicle according to the vehicle speed and the steering angle, and when the steering angle is set to be relatively small at least when the vehicle is running at medium speed, the steering is performed. An object of the present invention is to provide a power steering device for a vehicle, which can obtain an appropriate response through the steering wheel and can prevent the steering wheel operation from becoming too heavy during steering when the steering angle is relatively large. And

(Means for Solving Problems) In order to achieve the above-mentioned object, a vehicle power steering apparatus according to the present invention is operated by operating a vehicle speed sensor, a steering angle sensor, and a steering handlebar provided in the vehicle. In order to give a steering reaction force that changes in response to signals from a vehicle speed sensor and a steering angle sensor to the steering mechanism including the steering handle and a steering reaction force that applies a driving assist force corresponding to the steering to the steering handle. And a steering control unit that controls the auxiliary force generation unit, wherein the steering control unit increases the steering reaction force as the vehicle speed detected by the vehicle speed sensor increases,
At least when the vehicle is traveling at medium speed, the steering angle sensor detects the steering angle as compared with the rate of increase of the steering reaction force with respect to the increase of the steering angle when the steering angle detected by the steering angle sensor is relatively small. The increase rate of the steering reaction force with respect to the increase of the steering angle when the steering angle is relatively large is small.

(Operation) In the power steering apparatus for a vehicle according to the present invention configured as described above, the steering control means for generating the steering reaction force applied to the steering wheel generates the assisting force for applying the driving assisting force to the steering mechanism. In controlling the parts, the steering reaction force is increased as the vehicle speed detected by the vehicle speed sensor increases, and the steering angle detected by the steering angle sensor is relatively small at least when the vehicle is running at medium speed. The increase rate of the steering reaction force with respect to the increase of the steering angle when the steering angle detected by the steering angle sensor is relatively large compared to the increase rate of the steering reaction force with the increase of the steering angle at An increase in steering reaction force by performing a small control operation leads to an increase in torque required for steering performed by manually operating the steering wheel. As a result, when the vehicle is traveling at at least medium speed, when steering is performed with a relatively small steering angle, an appropriate response can be obtained through the steering handle during steering, and When steering is performed under a relatively large steering angle, the steering wheel operation is prevented from becoming too heavy during the steering.

(Example) Hereinafter, the Example of this invention is described with reference to drawings.

FIG. 1 shows an example of a power steering device for a vehicle according to the present invention. This power steering device includes an oil pump 10 driven by an engine, and the working pressure oil discharged from the oil pump 10 is electromagnetic. Throttle valve
It is supplied to the oil chamber of the power cylinder 20 via 12 and the rotary valve 15, and is supplied to the reaction force chamber 18 via the flow rate control valve 16. The degree of throttling of the electromagnetic throttle valve 12 is changed according to the value of the control current I supplied from the control unit 100. The manner of change is, for example, as shown in FIG. The larger the value of the control current I, the larger the degree of aperture.
Further, the flow rate control valve 16 is supplied to the reaction force chamber 18 according to the hydraulic pressure difference between the working pressure oil discharged from the oil pump 10 and the working pressure oil obtained at the outlet side of the electromagnetic throttle valve 12. Change the working oil pressure. Then, excess operating pressure oil in the rotary valve 15 and the flow rate control valve 16 is discharged to the reserve tank 22.

In this example, the rotary valve 15 constitutes the steering control means, and the electromagnetic throttle valve 12 and the flow rate control valve 16 constitute the pressure oil amount adjusting section, but the configuration of each of these valves is known. However, detailed description thereof will be omitted.

Based on such a configuration, by the power cylinder 20 whose working pressure oil is supplied to the oil chamber, the steering mechanism 25,
A drive assist force is applied according to manual steering performed by manually operating the steering handle 26. When a driving assist force is applied to the steering mechanism 25 by the power cylinder 20, the steering handle 26 is manually operated to apply a steering input to the rotary valve 15 from the steering handle 26, and in response to the steering input, the rotary handle 15 is rotated. The valve 15 controls the supply / discharge of the operating pressure oil to / from the oil chamber of the power cylinder 20 and the amount of the operating pressure oil supplied to the power cylinder 29. At that time, reaction chamber
At 18, hydraulic pressure that restricts the operation of the rotary valve 15 is generated by the working pressure oil supplied from the flow control valve 16,
This hydraulic pressure is applied to the steering wheel 26 as a steering reaction force.

The control unit 100 that supplies the control current I to the electromagnetic throttle valve 12 as described above includes the vehicle speed signal Sv, which is a detection signal corresponding to the vehicle speed, which is obtained from the vehicle speed sensor 30 arranged in association with the transmission. It is obtained from a steering angle sensor 36 provided in association with the steering wheel 26. A steering angle signal Sd, which is a signal representing the steering angle, which is the detected output of the steering angle of the steering handle 26, is supplied.

The control unit 100 is specifically, for example,
It is constructed as shown in FIG. In the specific example shown in FIG. 3, the control voltage forming circuit 52 to which the vehicle speed signal Sv obtained from the vehicle speed sensor 30 is supplied, and the steering angle sensor.
Control voltage forming circuits 51 and 53 to which the steering angle signal Sd obtained from 36 is supplied are provided. Control voltage forming circuit 51
The steering angle is large when the steering angle is within a predetermined value θ ₁ or less (at a small steering angle), as shown in FIG. 4, according to the steering angle represented by the steering angle signal Sd. The higher the level becomes, the more the steering angle exceeds a predetermined value θ ₁ , the more constant level L ₁
To form a control voltage S ₁ which is applied to _one input end of the adder circuit 56. Further, the control voltage forming circuit 52 forms a control voltage S ₂ that takes a higher level as the vehicle speed becomes higher, as shown in FIG. 5, according to the vehicle speed represented by the vehicle speed signal Sv, and adds it to the adding circuit 56. To the other input terminal and the comparison input terminal of the comparator 54. The adder circuit 56 forms a control voltage S ₄ having a level obtained by adding the level of the control voltage S _{1 and} the level of the control voltage S ₂ and outputs it to one input terminal of the AND circuit 61 and one of the subtraction circuits 58. Supply to the input end of. Further, the reference input terminal of the comparator 54 has a level corresponding to a predetermined vehicle speed.
When the reference voltage Sr of Lh is applied and the level of the control voltage S ₂ is higher than the level Lh of the reference voltage Sr, therefore, when the vehicle speed represented by the vehicle speed signal Sv becomes higher than a predetermined vehicle speed (vehicle During high-speed traveling), the control signal Sh having a high level is obtained from the comparator 54. This control signal Sh is the AND circuit 61
Is directly supplied to the other input terminal of the
The control signal Sh 'is level-inverted by 57 and supplied to one input terminal of the AND circuit 62.

Control voltage generating circuit 53 in accordance with the steering angle indicated by the steering angle signal Sd, the sixth to as shown in the figure, when the steering angle is smaller than the predetermined value theta ₂ takes a zero level, the steering angle is a predetermined value theta ₂ When the steering angle is less than the predetermined value θ ₃ , the higher the steering angle, the higher the level is, and when the steering angle is the predetermined value θ ₃ or more, the control voltage S ₃ that takes a constant level L ₁ is formed. Is supplied to the other input terminal of the subtraction circuit 58. The subtraction circuit 58 forms a control voltage S ₅ having a level obtained by subtracting the level of the control voltage S ₃ from the level of the control voltage S ₄ , and supplies it to the other input terminal of the AND circuit 62.

The AND circuit 61 obtains the control voltage S ₄ when the control signal Sh has a high level, while the AND circuit 62 obtains the control voltage S ₅ when the control signal Sh has a low level, and controls these voltages. The voltages S ₄ and S ₅ are supplied to the control current forming circuit 65 via the OR circuit 63. The control current forming circuit 65 has a control voltage
A control current I having a level according to the level of S ₄ or S ₅ is formed and supplied to the electromagnetic throttle valve 12.

Under such a configuration, when the vehicle speed represented by the vehicle speed signal Sv is higher than a predetermined vehicle speed corresponding to the level Lh of the reference voltage Sr, the OR circuit 63 controls the control voltage S ₁
Control voltage S ₄ taking level level and the level of the control voltage S ₂ is added to obtain, the control voltage S ₄ is supplied to the control current forming circuit 65, the control current generating circuit 65, the seventh
In the figure, when the vehicle is traveling at a high vehicle speed v ₃ , as illustrated, when the steering angle represented by the steering angle signal Sd is within a predetermined value θ ₁ or less, the steering angle is large. The control current I takes a certain level and takes a constant level (I ₃ ) when the steering angle exceeds a predetermined value θ ₁ .

Further, when the vehicle speed represented by the vehicle speed signal Sv is less than a predetermined vehicle speed corresponding to the level Lh of the reference voltage Sr at the medium speed or low speed running, the OR circuit 63 controls the level of the control voltage S _{4 to} the level of the control voltage S ₃ . A control voltage S ₅ having a level obtained by subtracting is obtained, and this control voltage S ₅ is the control current forming circuit 65.
In FIG. 7, the control current forming circuit 65 exemplifies a case where the vehicle is traveling at a medium speed v ₂ and a case where the vehicle is traveling at a low vehicle speed v _1. As described above, when the steering angle is in the range of the predetermined value θ ₁ or less, the larger the steering angle is, the higher the level is, and when the steering angle is in the range of the predetermined value θ ₁ or more and less than the predetermined value θ ₂ A range where the steering angle is a predetermined value θ ₂ or more and less than a predetermined value θ _{3 with a} certain level (I ₂ or I ₁ ; I ₃ > I ₂ > I ₁ ) smaller than the certain level when the vehicle is running at high speed. The control current takes a smaller level as the steering angle is larger, and when the steering angle is a predetermined value θ ₃ or more, the control current takes the same level as when the steering angle is the predetermined value θ _3. I is obtained.

The control current I obtained in this way is
As can be seen from the figure, under the same steering angle,
The higher the vehicle speed represented by the vehicle speed signal S _{v, the} higher the level.

The degree of throttle in the electromagnetic throttle valve 12 to which the control current I is supplied depends on the level of the control current I. Here, the greater the degree of throttle of the electromagnetic throttle valve 12, the greater the difference between the hydraulic pressure in the upstream side portion and the hydraulic pressure in the downstream side portion thereof, so the displacement amount of the spool built in the flow control valve 16 is increased. As a result, the amount of working pressure oil supplied from the oil pump 10 to the reaction force chamber 18 via the flow rate control valve 16 increases.

Then, the increase in the amount of working pressure oil supplied to the reaction force chamber 18 in the rotary valve 15 increases the hydraulic pressure generated in the reaction force chamber 18, and thus the steering reaction force applied to the steering handle 26 increases, The torque required for steering performed by manually operating the steering handle 26 is increased. As a result, the amount of working pressure oil supplied to the reaction force chamber 18 is changed as described above, and as a result, the torque required for steering has a steering angle of a predetermined value θa (as described above), as indicated by the solid line in FIG. When it is in the range less than the predetermined value θ ₂ ), the larger the steering angle at that time is, the larger the value is, as in the case of the conventional power steering device described above. The vehicle is fast V ₃
When the steering angle is in the range of the predetermined value θa or more, the steering angle increases in the range of less than the predetermined value θa in accordance with the steering angle at that time, as illustrated in the case of traveling at When the vehicle travels at low speed and medium speed, the vehicle is traveling at low speed v ₁ and medium speed v ₂ , respectively. When the steering angle is in a range equal to or greater than the predetermined value θa, an increase rate that is smaller than an increase rate when the steering angle increases within a range that is less than the predetermined value θa (for example, substantially zero) according to the steering angle at that time.
Will increase with.

Since the torque required for steering is changed in this way, when the vehicle is traveling at medium speed or low speed, when steering is performed while the steering angle is relatively small, When the steering wheel 26 is steered under a relatively large steering angle, the steering wheel 26 should not be too heavy to operate. In particular, there is an advantage that steering with a large steering angle can be performed easily without inconvenience.

Although the rotary valve 15 is used as the steering control means in the above example, a spool valve or a flapper valve may be used instead of the rotary valve 15, and the configuration of the pressure oil amount adjusting unit may be used. However, the combination is not limited to the combination of the electromagnetic throttle valve 12 and the flow control valve 16 described above. Furthermore, under a constant vehicle speed, when the steering angle is between the predetermined value θ ₁ and the predetermined value θ ₂ , it is not necessary to make the torque required for steering constant as in the above example,
Instead of being kept constant, the steering angle may be increased in accordance with the increase of the steering angle with an increase rate that is smaller than the increase rate when the steering angle is in the range of less than the predetermined value θ ₁ .

Further, in the above example, the electromagnetic throttle valve 12 is
Although it is assumed that the larger the control current I supplied to it, the larger the degree of throttling, the electromagnetic throttle valve 12 may have the opposite characteristic. That is, the electromagnetic throttle valve 12 controls the control current I supplied to it.
May have a characteristic such that the larger the degree is, the smaller the degree of aperture is, and the degree of aperture may be maximized when the control current I is not supplied. When the electromagnetic throttle valve 12 has such characteristics, for example, a failure such as disconnection occurs in the control system including the control unit 100 and the control current I is not supplied to the electromagnetic throttle valve 12. At this time, the degree of throttle of the electromagnetic throttle valve 12 is set to the maximum value so that the steering becomes heavy, so that the steering of the vehicle is prevented from becoming unstable.

(Effects of the Invention) As is apparent from the above description, according to the power steering device for a vehicle according to the present invention, the torque required for steering changes depending on the vehicle speed and the steering angle.
At least when the vehicle is running at medium speed, when the steering angle is relatively small, an appropriate response is obtained through the steering wheel for steering, and when the steering angle is relatively large, When steering, the steering wheel operation is prevented from becoming too heavy. Therefore, there is an advantage that stable steering can be easily performed especially when the vehicle is traveling at a medium speed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a vehicle power steering apparatus according to the present invention, FIG. 2, FIG. 4, FIG. 5, FIG.
FIG. 7 and FIG. 7 are characteristic diagrams for explaining the operation of the example shown in FIG. 1, FIG. 3 is a block diagram showing a concrete example of the control unit in the example shown in FIG. 1, and FIG. FIG. 3 is a characteristic diagram provided for explaining the operation of the power steering device of FIG. 1 and the example shown in FIG. 1. In the figure, 10 is an oil pump, 12 is an electromagnetic throttle valve, 15 is a rotary valve, 16 is a flow control valve, 18 is a reaction force chamber, 20 is a power cylinder, 30 is a vehicle speed sensor, 36 is a steering angle sensor, and 10 is a steering angle sensor.
0 is a control unit.

Claims (1)

(57) [Claims] 1. A vehicle speed sensor, a steering angle sensor, and an assisting force generator for applying a driving assisting force to a steering mechanism including the steering wheel, the drive assisting force corresponding to steering performed by operating a steering wheel provided on the vehicle. Steering control means for generating a steering reaction force that changes in response to signals from the vehicle speed sensor and the steering angle sensor to the steering wheel and controlling the auxiliary force generating portion, The steering control means increases the steering reaction force as the vehicle speed detected by the vehicle speed sensor increases, and the steering angle detected by the steering angle sensor is relatively high at least during the medium speed running of the vehicle. The steering angle detected by the steering angle sensor is relatively large compared to the rate of increase of the steering reaction force with respect to the increase of the steering angle when the steering angle is small. Power steering device for a vehicle, characterized in that formed between the small rate of increase of the steering reaction force against the increase of the steering angle of a certain original.