JPH08175414A - Steering device - Google Patents

Abstract

PURPOSE: To provide a steering device which can be controlled so as to make the actual behavior of a vehicle close to the expected properties of the vehicle obtained from the information inputted in a model within the vehicle. CONSTITUTION: When a steering angle detected by a steering angle sensor 16 and vehicle speed detected by a vehicle speed sensor 17 are inputted into the controller 14, the expected properties of the vehicle are computed according to the steering angle and vehicle speed. Using a lateral (g) detected by (g) sensor and/or a yaw rate detected by a yaw rate sensor 21 as the actual behavior of the vehicle, the controller 14 variably-controls the rigidity of a rack insulator 11 to get rid of a difference between the actual behavior and the expected properties of the vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device that steers the front wheels of a vehicle according to the rotation of the steering wheel.

[0002]

2. Description of the Related Art Conventionally, a steering device for improving steering response and stability of a vehicle is disclosed in, for example, Japanese Utility Model Laid-Open No. 60-25576. In this steering device, the compliance understeer amount of the front wheels of the vehicle is controlled according to the vehicle speed, and the steering characteristic and stability of the vehicle are improved by making the steer characteristic of the vehicle understeer tendency as the vehicle speed increases.

[0003]

However, in such a steering device, since the steering rigidity decreases as the traveling speed of the vehicle increases, the front wheels are steered when disturbance is input. Further, since such a steering device does not perform control based on the actual vehicle behavior, it is not possible to consider the friction coefficient of the road surface, which changes depending on the weather and the quality of the road surface, and therefore when the vehicle is traveling at high speed, There is the inconvenience that control is not performed even if there is a deviation between the vehicle behavior and the desired characteristics of the vehicle desired by the driver.

An object of the present invention is to provide a steering system which can control the desired characteristics of the vehicle obtained from the information input to the model inside the vehicle and the actual vehicle behavior so as to approach each other.

[0005]

A steering device according to a first aspect of the present invention is a variable control mechanism capable of variably controlling the rigidity of a steering system that steers the front wheels of a vehicle according to the rotation of a steering wheel, and a predetermined information. First to detect
Detecting means, calculating means for calculating the desired characteristics of the vehicle based on the detection signal of the first detecting means, second detecting means for detecting the actual vehicle behavior, and actual detected by the second detecting means. Variable control means for variably controlling the variable control mechanism is provided so as to eliminate the difference between the vehicle behavior and the desired characteristic of the vehicle.

According to a second aspect of the steering device of the present invention, the first detecting means detects a steering wheel angle and a vehicle speed as the predetermined information.

In the steering device according to a third aspect of the present invention, the second detecting means detects a physical quantity equivalent to yaw rate and / or a physical quantity equivalent to lateral acceleration acting on the vehicle body as the actual vehicle behavior. To do.

In the steering device according to a fourth aspect of the present invention, the second detection means detects a physical quantity equivalent to yaw rate and a physical quantity equivalent to lateral acceleration acting on the vehicle body as the actual vehicle behavior, and the variable control means When the vehicle is traveling at a medium or low speed, when the physical quantity equivalent to the yaw rate is variably controlled by the variable control mechanism using the value of the actual vehicle behavior, and when the vehicle is traveling at a high speed. Is characterized in that the physical quantity corresponding to the lateral acceleration is variably controlled by using the actual vehicle behavior value.

[0009]

In the steering apparatus according to the first aspect of the present invention, when the predetermined information is detected by the first detecting means, the calculating means calculates the intended characteristic of the vehicle based on the detection signal of the first detecting means. The variable control means controls the variable control mechanism so as to eliminate the difference between the desired characteristic of the vehicle and the actual vehicle behavior detected by the second detection means.

In the steering device according to the second aspect of the present invention, the calculating means calculates the desired characteristic of the vehicle based on the steering wheel angle and the vehicle speed detected by the first detecting means. The variable control means controls the variable control mechanism so as to eliminate the difference between the desired characteristic of the vehicle and the actual vehicle behavior detected by the second detection means.

In the steering device according to the third aspect of the present invention, the second detecting means detects the physical quantity equivalent to yaw rate and / or the physical quantity equivalent to lateral acceleration acting on the vehicle body as the actual vehicle behavior as the actual vehicle behavior. Thus, it is possible to realize better variable control of the rigidity of the steering system.

In the steering device according to a fourth aspect of the present invention, the second detecting means detects a physical quantity equivalent to yaw rate and a physical quantity equivalent to lateral acceleration acting on the vehicle body as an actual vehicle behavior, and the variable control means controls the vehicle When running at medium to low speeds, the physical quantity equivalent to yaw rate is variably controlled by the variable control mechanism using the actual vehicle behavior value, and when the vehicle is running at high speed, the physical quantity equivalent to lateral acceleration is adjusted. The variable control mechanism is variably controlled using the actual vehicle behavior value.

At low and medium speeds, stability does not become a problem at high and medium speeds, but rather good responsiveness is required. On the other hand, at high speeds, stability such that the rear part of the vehicle does not swing is required. Therefore, it is desirable that the yaw rate is selected as the vehicle behavior in order to improve the turning performance at medium and low speeds, whereas the lateral acceleration is selected at the high speed so that the lateral movement is improved, that is, the lateral acceleration is selected so that the vehicle trajectory becomes close to the desired characteristic. By changing the actual vehicle behavior value in accordance with the vehicle speed in this way, it is possible to realize better variable control of the rigidity of the steering system.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a steering device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a basic configuration diagram of a steering device according to the present invention. When the steering wheel 1 is rotated, the column shaft 2 fitted to the steering wheel 1 also rotates. This rotation is a rubber coupling (also called a column coupling)
3, transmitted to the pinion gear 5 via the intermediate shaft 4 and a joint (not shown). The pinion gear 5 meshes with the rack shaft 6, whereby the rotation of the pinion gear 5 is converted into a lateral movement of the rack shaft 6. The lateral movement amount of the rack shaft 6 is converted into the rotational movement again through the side rod 7 and the knuckle arm 8 and becomes the steering amount of the tire 9.

The rack shaft 6 is supported by a rack housing 10, and the rack housing 10 is placed on a vehicle body via a rack insulator 11. Therefore, the rigidity of the steering system is almost determined by the rigidity of the rubber coupling 3 and the rack insulator 11. Therefore, the rigidity of the rubber coupling 3 and the rack insulator 11 may be controlled in order to control the steering rigidity.

In this example, as a first example, a case where the rigidity of the rack insulator 11 is controlled will be described.
It is considered that the same effect as that of the present invention can be obtained by changing the rigidity of the link bush of the suspension. However, when changing the rigidity of the link bush of the suspension, the lateral force of the tire ground contact surface is changed by an external force (cornering force). Deformation occurs. As a result, the size of the cornering force does not change because the slip angle of the tire changes, but the generation of the cornering force is delayed. The steering device according to the present invention is different from the case where the rigidity of the link bush of the suspension is controlled in that only the change in the toe angle of the tire can be controlled.

FIG. 2 is a schematic diagram of an electro-hydraulic system for variably controlling the rigidity of the rack insulator. The flow rate generated by the pump 12 driven by the rotation of the engine or a separately provided motor is guided to the pressure control valve 13. The pressure control valve 13 generates a predetermined pressure according to a command current from the controller 14, and makes the pressure of the hydraulic chamber provided in the rack insulator 11 a predetermined pressure. The unnecessary flow rate is stored in the reservoir tank 15 and then sucked up by the pump 12. Although two rack insulators are shown in FIG. 1, only one of the rack insulators may be controlled. The controller 14 includes a steering wheel angle sensor 16 and a vehicle speed sensor 1
Calculation is performed based on the signal from 7 and the command current is supplied to the pressure control valve 13.

FIG. 3A is a side view of the rack housing, and FIG. 3B is a sectional view taken along line I-I thereof. A first embodiment in which the rigidity of the rack insulator is variably controlled using this will be described. The hydraulic chamber 11a provided in the rack insulator 11 is connected to the pressure control valve 13 (FIG. 2) via the hydraulic pipe 11b. Brackets 19a and 19b welded to the member 18 are fastened with bolts (not shown). As a result, the rack housing 10 is elastically supported by the rack insulator 11 with respect to the member 18.

Therefore, in FIG. 1, when a cornering force is generated in the tire 9, this cornering force is transmitted through the side rod 7 and the rack housing 10 moves in the left-right direction. This amount of movement is controlled by the rigidity value of the rack insulator 11.

In FIG. 3, the rack insulator 11
Is formed of an elastic body, and a hydraulic chamber 11a is provided in the rack insulator 11. The hydraulic chamber 11a is connected to the hydraulic pipe 11b.
The pressure control valve 13 in FIG. 2 controls the pressure. The rack insulator rigidity, that is, the rigidity of the steering system is changed according to the hydraulic pressure in the hydraulic chamber 11a.

In the controller 14 (FIG. 2), the command current and the pressure in the hydraulic chamber and the rack insulator 1 are used.
The relationship between 1 and the rigidity in the axial direction is measured in advance, and the current for obtaining the predetermined rigidity value is mapped. Variable control of the rigidity of the steering system is performed according to this map.

Variable control of the rigidity of the steering system according to the present invention will be described. The steering wheel angle and the vehicle speed detected by the steering wheel angle sensor 16 (FIG. 2) and the vehicle speed sensor 17 (FIG. 2) are supplied to the controller 14 (FIG. 2), respectively, and the initial characteristics of the model in the controller 14 (FIG. 2) Calculate the resulting vehicle behavior. On the other hand, as the actual vehicle behavior, the lateral g (lateral acceleration acting on the vehicle body) and the yaw rate are detected by the g sensor 20 and the yaw rate sensor 21.

When the lateral g and yaw rate calculated by the controller are g1 and φ1, respectively, and the lateral g and yaw rate detected by the g sensor 20 and the yaw rate sensor 21 are g2 and φ2, respectively, the variable stiffness of the steering system is controlled. It is performed based on g1-g2 or φ1-φ2.

FIG. 4 is a control characteristic diagram of the steering apparatus according to the present invention. FIG. 4 shows a case where the yaw rate φ2 detected by the yaw rate sensor 21 is adopted as the actual vehicle behavior.

First, in the period A, the actual behavior, that is, the yaw rate φ2 is smaller than the desired behavior, that is, the yaw rate φ1,
Since the movement of the vehicle is slow, increase the steering rigidity. In the period B, the yaw rate φ1 and φ1 are desired to be reduced by returning the steering wheel, and it is considered that the yaw rate φ2 returns to 0 earlier, so the steering rigidity is reduced.

Contrary to the period B, in the period C, the yaw rate φ2 does not return to 0 in response to the return of the steering wheel, so the steering rigidity is increased. In period D, as in period A,
Since the movement of the vehicle is slow, increase the steering rigidity.
In the period E, the steering rigidity is lowered for the same reason as in the period B. In the period F, the steering rigidity is increased for the same reason as in the period C. The control characteristic diagram of FIG.
This is a description of how to perform variable control of steering rigidity, and does not reflect the effect of control in the figure.

FIG. 5 is a diagram summarizing the control logic of the steering system according to the present invention. As you can see from the figure,
When the steering rigidity K is φ2> 0,

Set the arithmetic expression as Equation 1] _{K = K 0 + A (φ1} -φ2) (1), in the case of .phi.2> 0 whereas,

It may be set an equation as Equation 2] _{K = K 0 -A (φ1-} φ2) (2). However, K ₀ is the set rigidity when the steering wheel is neutral, and A is the proportional constant. It is desirable that the value of K ₀ is set to be high to some extent at a level at which a malfunction of the steering system such as shimmy or kickback when the vehicle is straight ahead can be tolerated to ensure the stability against disturbance. By adding the control described below in addition to the above control, more favorable control can be performed.

The values of K ₀ and A are changed according to the vehicle speed. As described in Japanese Utility Model Laid-Open No. 60-25576, it is desirable to make the steer characteristic understeer as the vehicle speed increases, but the basic understeer should be secured by the above-mentioned control that performs vehicle behavior feedback. As shown in FIG. 6A, the set rigidity K ₀ when the steering wheel is in neutral is increased as the vehicle speed increases in order to give a solid sense of the steering system and the disturbance of the course due to road surface disturbance. Further, as shown in FIG. 6B, the proportional constant A, which is the control gain, is likewise increased as the vehicle speed increases. This is because the delay of the vehicle behavior increases as the vehicle speed increases, and it is difficult to correct the actual behavior unless the control effect is increased.

As the vehicle behavior amount, the yaw rate detected by the yaw rate sensor at medium and low speeds and g at high speeds
The lateral g detected by the sensor is adopted. When the vehicle travels at medium to low speeds, stability does not become a problem as at high speeds, and rather good responsiveness is required, whereas when traveling at high speed, stability is ensured so that the rear part of the vehicle does not swing. Is required. Therefore, it is desirable that the yaw rate is selected as the vehicle behavior in order to improve the turning performance at low and medium speeds, while the lateral movement is improved at the high speed, that is, the lateral g is selected so that the vehicle trajectory is close to the desired characteristic. For this reason, the steering stiffness K is changed to the above formula (1) when φ2> 0.

Equation 3] _{K = K 0 + A (φ1} -φ2) + set an equation as B (g1-g2) (3 ), instead of the above formula in the case of contrast φ2> 0 (2) ,

It may be set an equation as Equation 4] _{K = K 0 -A (φ1-} φ2) -B (g1-g2) (4). However, K ₀ is the set rigidity when the steering wheel is neutral, and A and B are proportional constants.
In this case, the above-mentioned characteristics are satisfied by setting the proportional constants A and B as shown in FIGS. 7 (a) and 8b).

Let K ₀ in the equations (1) to (4) be the rigidity value of the hardware (in this case, the rack insulator), and let the rigidity when the vehicle is traveling straight ahead be K ₀ . In the above-described embodiment, as shown in (1) to (4), the rigidity is controlled to be high or low even when the steering wheel is neutral. However, if such control is performed, pressure is always generated when controlling with hydraulic pressure, and energy loss increases, so that fuel efficiency of the vehicle deteriorates. Further, when the rigidity of the rubber coupling is controlled by the electrorheological fluid as in the case of the third embodiment described later, the load on the battery increases. Therefore, the rigidity of the steering system is variably controlled only in the direction in which the rigidity is made rigid, and the other values are allowed by the rigidity value determined by the hardware. As a result, it is possible to reduce adverse effects on fuel efficiency and the like.

In this case, the steering stiffness K is calculated by the equation (1).
Control is performed according to (4), but if K <K ₀ , control is not performed. The control characteristic diagram at this time is shown in FIG. Further, FIG. 9 shows a control characteristic diagram in the case where the steering stiffness K is continuously changed as shown in FIGS. In this case, JP-A-60-161
Since an on / off type actuator as disclosed in Japanese Patent No. 251 can also be used, the steering device can be made inexpensive.

FIG. 10A is a side view of the rubber coupling, and FIG. 10B is a II-II sectional view thereof. A second embodiment in which the rigidity of the rubber coupling is variably controlled using this will be described. The basic configuration of the steering device of this example is the same as that of FIG. 1, and the electro-hydraulic system for variably controlling the rigidity of the rubber coupling is the same as that of FIG.

The outer cylinder 23 of the rubber coupling 3 welded to the input shaft 22 is fitted to the column shaft 2 (FIG. 1) so that they rotate integrally. An elastic body 25 is filled between the input shaft 22 and the output shaft 24. The output shaft 24 is connected to the intermediate shaft 4 (FIG. 1) so that they rotate together. Therefore, the elastic body 25 is twisted between the column shaft 2 (FIG. 1) and the intermediate shaft 4 (FIG. 1). The amount of twist displacement varies depending on the rigidity of the elastic body 25.

In this example, as shown in the figure, a hydraulic chamber 3a is provided inside the elastic body 25, and the pressure in the hydraulic chamber 3a is controlled by the hydraulic pressure in the hydraulic pipe 3b provided in the output shaft 24. In this example, the rubber coupling 3 is configured so that the rigidity value of the rubber coupling 3 in the twisting direction increases as the pressure in the hydraulic chamber 3a increases.

FIG. 11A is a side view of a rubber coupling controlled by an electrorheological fluid, and FIG. 11B is its side view III-.
It is a III sectional view. Using this, a third embodiment in which the rigidity of the rubber coupling is controlled by the electrorheological fluid will be described. The basic configuration of the steering device of this example is the same as that of FIG. 1, and the electro-hydraulic system for variably controlling the rigidity of the rubber coupling is the same as that of FIG.

In this example, the pipe-shaped spacer 26a is on the input shaft side, that is, the column shaft 2 (FIG. 1) side, and the spacer 26b having the same shape as the spacer 26a is on the output shaft side, that is, the intermediate shaft 4 (FIG. 1) side. , Through bolts, etc. These spacers 16
The elastic body 27 is bonded to a and 26b.

A liquid chamber 28 and an orifice 29 are provided inside the elastic body 27, and the liquid chamber 28 and the orifice 29 are filled with an electrorheological fluid. When the rubber coupling 3 is twisted, one of the two liquid chambers 28 connected by the orifice 29 expands and the other contracts. Therefore, the electrorheological fluid in the contracted liquid chamber 28 flows through the orifice 29.

Further, in this example, the electrodes 30 are provided around the orifices 29, and the voltage applied to these electrodes 30 is changed to change the viscosity of the electrorheological fluid filled in the orifices 29. As a result, the orifice 2
The viscosity of the electrorheological fluid passing through 9 changes, and the restraining force against the twist between the input shaft and the output shaft changes.

When the torsional speed is extremely low, the effect of controlling the rigidity of the rubber coupling is small, but in general, when the torsional displacement occurs, the rubber coupling has a certain torsional speed, and the rigidity of the rubber coupling is equivalently determined. Since it has been changed, a sufficient effect can be obtained even with such a configuration.

Here, the yaw rate feedback control type four-wheel steering system has an effect similar to this, but in the case of yaw rate feedback 4WS, when the yaw rate occurs, if the actual yaw rate does not reach the target yaw rate, the rear wheel To steer in the opposite phase direction to generate yaw rate. However, in this case, the cornering force of the front wheels is not increased, but the cornering force of the rear wheels is decreased to create a yaw moment to correct the yaw rate. As a result, the total lateral force of the front and rear wheels decreases, and the lateral g decreases. That is, the rear part of the vehicle is swung to form a side slip angle, but the vehicle trajectory is deviated.

On the other hand, when the rigidity of the steering system is controlled as in the present invention, if the yaw rate does not reach the target yaw rate, the compliance steering of the front wheels is controlled so as to be on the oversteer side. As a result, yaw moment is generated. Therefore, both the yaw rate and the lateral g can be increased, and as a result, the vehicle can be made to travel on the vehicle trajectory desired by the driver.

[0042]

As described above, according to the steering apparatus of the first aspect of the present invention, the rigidity of the steering system is controlled so as to eliminate the difference between the desired characteristics of the vehicle and the actual vehicle behavior. The actual vehicle behavior can be a desired characteristic regardless of the driving conditions.

According to the steering device of the second aspect of the present invention, by detecting the steering wheel angle and the vehicle speed as the predetermined information, it is possible to realize better variable control of the rigidity of the steering system.

According to the steering device of the third aspect of the present invention, by detecting the physical quantity equivalent to the yaw rate and / or the physical quantity equivalent to the lateral acceleration acting on the vehicle body as the actual vehicle behavior, a better steering system can be obtained. Variable rigidity control can be realized.

According to the steering device of the fourth aspect of the present invention, it is possible to realize a better variable control of the rigidity of the steering system by changing the value of the actual vehicle behavior according to the vehicle speed.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a steering device according to the present invention.

FIG. 2 is a schematic diagram of an electro-hydraulic system for variably controlling the rigidity of a rack insulator.

FIG. 3A is a side view of the rack housing,
(B) is the II sectional view.

FIG. 4 is a control characteristic diagram of the steering device according to the present invention.

FIG. 5 is a diagram summarizing the control logic of the steering device according to the present invention.

FIG. 6A shows a vehicle speed V and a set rigidity K when the steering wheel is in a neutral position.
It is a figure which shows the relationship between _0, and (b) is a figure which shows the relationship between the vehicle speed V and the proportionality constant A.

7A and 7B are diagrams showing characteristics of proportional constants A and B, respectively.

FIG. 8 is another control characteristic diagram of the steering device according to the present invention.

FIG. 9 is another control characteristic diagram of the steering device according to the present invention.

FIG. 10A is a side view of the rubber coupling, and FIG. 10B is a sectional view taken along the line II-II thereof.

11A is a side view of a rubber coupling controlled by an electrorheological fluid, and FIG. 11B is a sectional view taken along line III-III thereof.

[Explanation of symbols]

 1 Steering Wheel 2 Column Shaft 3 Rubber Coupling 4 Intermediate Shaft 5 Pinion Gear 6 Rack Axis 7 Side Rod 8 Knuckle Arm 9 Tire 10 Rack Housing 11 Rack Insulator 3a, 11a Hydraulic Chamber 3b, 11b Hydraulic Piping 12 Pump 13 Pressure Control Valve 14 Controller 15 Reservoir tank 16 Handle angle sensor 17 Vehicle speed sensor 18 Members 19a, 19b Bracket 20 g sensor 21 Yaw rate sensor 22 Input shaft 23 Outer cylinder 24 Output shaft 25, 27 Elastic body 26a, 26b Spacer 28 Liquid chamber 29 Orifice 30 Electrode A, B, C, D, E, F period

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B62D 137: 00

Claims (4)

[Claims] 1. A variable control mechanism capable of variably controlling the rigidity of a steering system that steers the front wheels of a vehicle according to the rotation of a steering wheel, a first detection means for detecting predetermined information, and a first detection means of the first detection means. Calculation means for calculating desired characteristics of the vehicle based on the detection signal, second detecting means for detecting actual vehicle behavior, actual vehicle behavior detected by the second detecting means, and desired characteristics of the vehicle A steering device comprising variable control means for variably controlling the variable control mechanism so as to eliminate the difference between the variable control mechanism and the variable control mechanism. 2. The steering apparatus according to claim 1, wherein the first detecting means detects a steering wheel angle and a vehicle speed as the predetermined information. 3. The steering according to claim 1, wherein the second detection means detects a physical quantity equivalent to yaw rate and / or a physical quantity equivalent to lateral acceleration acting on the vehicle body as the actual vehicle behavior. apparatus. 4. The second detecting means detects a physical quantity equivalent to yaw rate and a physical quantity equivalent to lateral acceleration acting on the vehicle body as the actual vehicle behavior, and the variable control means detects that the vehicle is running at a medium or low speed. In this case, the physical quantity equivalent to the yaw rate is variably controlled by the variable control mechanism using the value of the actual vehicle behavior, and when the vehicle is traveling at a high speed, the physical quantity equivalent to the lateral acceleration is determined. The steering apparatus according to claim 1 or 2, wherein the variable control mechanism is variably controlled using a value of the actual vehicle behavior.