JPS6264671A - Power steering device - Google Patents

Abstract

PURPOSE:To improve steering sensibility over the entire speed region from a low vehicle speed region to a high vehicle speed region, by controlling auxiliary force entered into a steering wheel to modulate a sensibility characteristic with respect to a steering angle speed in accordance with a vehicle speed. CONSTITUTION:Sensibility, which is a ratio of auxiliary force to a manual torque entered into a steering wheel 19, is changed in accordance with a signal applied to an electronic control unit from a steering angle sensor 69 and a vehicle speed sensor 74 so that auxiliary force from auxiliary force producing means 10 is controlled in accordance with the sensibility. More specifically, the amount of oil to be supplied to a servo valve 14 is increased and the by-pass amount in a power cylinder 15 is reduced at a low vehicle speed so that steering operation is effected more lightly as the steering wheel 19 is actuated more quickly. The amount of oil to be supplied to the servo valve 14 is reduced and the by-pass amount in the power cylinder is increased at a high vehicle speed so that the steering operation is effected more heavily as the steering wheel is actuated more quickly. Thus, the most desirable sensibility characteristic with respect to a steering angle speed is obtained regardless of a vehicle speed so as to improve steering feeling.

Description

[Detailed description of the invention] [Industrial application field]

TECHNICAL FIELD The present invention relates to a power steering device for improving steering sensitivity of an automobile.

[Prior art]

A power steering device for an automobile is a device that generates an auxiliary steering force in proportion to the magnitude of manual torque input to a steering shaft of an automobile, thereby reducing the manual torque required for steering. The sensitivity, which is the ratio of auxiliary steering force to manual torque, can be varied depending on vehicle speed, steering angle, steering angular velocity, coefficient of friction between the road surface and the steered wheels, etc., so that the steering sensation is optimal regardless of driving conditions. Proposed.

[Problems to be solved by the invention]

Among these, various types of sensitivity characteristics to the steering angular velocity have been considered. The first characteristic is that the sensitivity increases as the steering angular velocity increases. This is a control method in which when the driver intends to turn the steering wheel quickly, the auxiliary steering force is increased to lighten the steering operation in order to achieve that intention. Control based on this characteristic provides a desirable steering feeling that matches the driver's intention, since the faster the steering wheel is turned, the lighter the steering becomes when driving at low speeds. However, when driving at high speeds, there is a problem in that the steering wheel becomes too light when the steering wheel is suddenly operated. The second characteristic is that the sensitivity decreases as the steering angular velocity increases. This is a control method that conversely makes the steering wheel harder to operate if the steering wheel is turned quickly. Control based on this characteristic improves safety by suppressing sudden steering operations because the steering wheel becomes heavy when driving at high speeds due to carelessness or excessively sudden steering operations. and straight-line running performance is improved. However, when driving at low speeds, the steering wheel becomes heavy, contrary to the driver's intention to suddenly operate the steering wheel, and the smoothness of the steering wheel operation is lost, resulting in a feeling of jerkiness in the steering wheel operation. The present inventors point out that the conventional sensitivity characteristics regarding steering angular velocity have the above-mentioned problems, and propose a new sensitivity characteristic that improves these drawbacks. That is, an object of the present invention is to improve the steering feel over the entire vehicle speed range from a low vehicle speed region to a high vehicle speed region by modulating the sensitivity characteristics regarding the steering angular velocity according to the vehicle speed.

[Means to solve the problem]

The structure of the invention for improving the above problems is as follows. an auxiliary force generating means that generates an auxiliary force to assist the steering force of the automobile in response to a control signal from a control device; a steering angular velocity detector that detects a steering angular velocity of a steering wheel of the automobile; and a steering angular velocity detector that detects the running speed of the automobile. A vehicle speed detector, the steering angular velocity detector, and signals from the vehicle speed detector are input, and the ratio of the auxiliary force to the manual torque input to the steering wheel of the automobile is calculated according to the detected steering angular velocity and vehicle speed. A power steering device comprising a control device that changes a certain sensitivity and controls the auxiliary force output by the auxiliary force generating means according to the sensitivity, the control device controlling the auxiliary force when the vehicle speed is low. The auxiliary force is controlled with a low vehicle speed characteristic that increases the sensitivity as the steering angular velocity increases, and when the vehicle speed is high, the auxiliary force is controlled with a high vehicle speed characteristic that decreases the sensitivity as the steering angular velocity increases. However, when the vehicle speed is an intermediate speed, the auxiliary force is controlled using an intermediate vehicle speed characteristic between the low vehicle speed characteristic and the high vehicle speed characteristic corresponding to the vehicle speed. Specific aspects of realizing the control characteristics of the sensitivity regarding the steering angular velocity using the vehicle speed of the control device as a parameter are as follows.
For example, the following means can be used. First, the control device is provided with a storage device that stores the low vehicle speed characteristic, the high vehicle speed characteristic, and the intermediate vehicle speed characteristic corresponding to the vehicle speed as a data map. Second, a storage device storing the low vehicle speed characteristic and the high vehicle speed characteristic in the control device;
An intermediate vehicle speed characteristic calculating device is provided that calculates the intermediate vehicle speed characteristic by interpolation according to the detected vehicle speed from the low vehicle speed characteristic and the high vehicle speed characteristic stored in the storage device.

[Effect]

The control device inputs signals from the steering angular velocity detector and the vehicle speed detector, and changes the sensitivity, which is the ratio of the auxiliary force to the manual torque input to the steering wheel of the car, according to the detected steering angular velocity and vehicle speed. Then, the auxiliary force output by the auxiliary force generating means is controlled according to the sensitivity. When the vehicle is running at low speed, the control device controls the auxiliary force using a low vehicle speed characteristic that increases the sensitivity as the steering angular velocity increases; The auxiliary force is controlled using high vehicle speed characteristics that reduce sensitivity. When the vehicle is at an intermediate speed between the above speeds, the auxiliary force is controlled according to the vehicle speed using an intermediate vehicle speed characteristic between a low vehicle speed characteristic and a high vehicle speed characteristic. The auxiliary force generating means inputs a control signal from the control device to control the auxiliary force with the above characteristics, generates an auxiliary force according to the optimum sensitivity at that time, and assists manual torque to operate the steering wheel. Improve your sexuality.

【Example】

The device of this embodiment relates to a hydraulic power steering device. In this embodiment, the sensitivity characteristics related to the steering angular velocity are appropriately changed according to the vehicle speed, and the sensitivity characteristics related to the vehicle speed and the sensitivity characteristics related to the steering angle are also taken into consideration. In other words, the higher the vehicle speed, and the larger the steering angle, the lower the sensitivity, the smaller the auxiliary steering force generated in response to manual torque, and the heavier the steering feel. It is controlled so that Embodiments of the present invention will be described below based on the drawings. In FIG. 1, reference numeral 10 denotes an auxiliary force generating means, which includes a servo valve 14, a power cylinder 15, a solenoid valve 20, a solenoid drive circuit 65 for driving the solenoid valve 20, and a pump 22.
, a flow rate control valve device 40 , a solenoid drive circuit 75 for driving the same, and a hydraulic circuit 12 . The servo valve 14 is connected to a steering wheel 19 via a handle glaze 17, and the power cylinder 15 is connected to a steering wheel via a steering linkage of the enclosure. Therefore, by applying manual torque to this steering handle 19 and controlling the rotation of the servo valve 14, the power cylinder 1
The supply of pressure fluid to the power cylinder 15 is controlled.
An auxiliary steering force is generated, and the increased steering torque (manual torque + auxiliary steering force) is transmitted to the steered wheels. A pump 22 is connected to the servo valve 14 via a hydraulic circuit 12.
is connected. This pump 22 is connected to an automobile engine via a belt drive system, and the pumping action of this pump 22 supplies pressurized fluid to the servo valve 14 and power cylinder 15. Further, a solenoid valve 20 is attached to the power cylinder 15. This solenoid valve 20 bypasses a portion of the pressure fluid supplied to one high pressure chamber of the power cylinder 15 to the other low pressure chamber of the power cylinder 15, and its structure is! This is shown in the sectional view of Figure 2. The electromagnetic valve 20 includes a valve body 24, a spool 26 slidably inserted into an inner hole 25 of the valve body 24, and a solenoid 27. The spool 26 is normally held at the lower end by the bias of the spring 28, and the power cylinder 1
The communication between the passage 30 leading to the left ventricle of No. 5 and the passage 31 leading to the right ventricle is blocked. When an attractive force is applied to the spool 26 according to the current value applied to the solenoid 27, the spool 26 is displaced upward against the spring 28, and the passage 30
．． 31 are communicated with each other via a bypass slit 34. The pump 22 is further provided with a flow rate control valve device 40 that controls the discharge flow rate. This flow control valve device 40
As shown in FIG. 3, the throttle 45 controls the pressure fluid flowing from the discharge hole 42 of the pump 22 to the delivery boat 43, and the servo valve slides by the back and forth pressure of this proof 45 to open and close the bypass hole 44. It consists of a spool valve member 46 that controls the flow rate of pressure fluid supplied to the spool valve 14, and an electromagnetic valve 48 that is attached coaxially with the spool valve member 46 and adjusts the opening degree of the throttle 45. The solenoid valve 48 includes a solenoid 49, a movable spool 50 that is displaced by energization of the solenoid 49, and a valve shaft 51 integrally connected to the movable spool 50. Movable spool 50
Normally, the spring 53 together with the valve shaft 51 causes the orifice 4 to
5, and the throttle 45 is fully opened. However, as the movable spool 50 moves in the direction of the throttle 45 against the force 1a of the spring 53, the valve shaft 51 approaches the throttle 45 and reduces its opening degree. This operation causes the servo valve 14 to be removed from the delivery port 43.
The supply flow rate of pressure fluid to is reduced. In FIG. 1, 60 is an electronic control device. This electronic control device 60 has a microprocessor 61, a RAM 62, and a ROM 63 as its main components. This microprocessor 61
An interface 64 is connected to the interface 64, and a solenoid drive circuit 65.75 is connected to the interface 64. The solenoid drive circuits 65 and 75 control the current applied to the solenoid 27 of the electromagnetic valve 20 and the solenoid 49 of the flow control valve device 40, respectively. Further, a steering angle sensor 69 is connected to the microprocessor 61 via an interface 66, a counter 67, and a phase determination circuit 68. The steering angle sensor 69 consists of a rotary plate 70 connected to the steering shaft 17 and two photointerrupters 71 and 72, and detects the steering angle θ of the steering wheel from the signals from the photointerrupters 71 and 72. ing. Further, the steering angular velocity δ is detected from the period of the pulse input to the counter 67. Furthermore, a vehicle speed sensor 74 is connected to the microprocessor 61 via an interface 66 and a counter 75. The vehicle speed sensor 74 is composed of a tachometer connected to the output shaft of the transmission, and detects the vehicle speed (2) from the frequency of a pulse signal generated from the vehicle speed sensor 74. On the other hand, the ROM 63 contains a control pattern of a control current proportional to the applied current applied to the solenoid 27.49 of the electromagnetic valve 20, 48, and a control coefficient for calculating the applied current based on various parameters as a characteristic map. remembered. This control pattern is shown in Fig. 5(a).
Control pattern 1 regarding vehicle speed obtained from the combination of characteristic maps A1 and 81 as shown in FIG. 5(C),
As shown in (d), a control pattern 2 regarding the steering angle θ is prepared which is a combination of characteristic maps A2 and 82. Further, a control characteristic map regarding the steering angular velocity, which is a feature of the present invention, is shown in FIG. Figure 6 (a), (b)
) shows characteristic maps A3L and B3L during low-speed driving, and Fig. 6(C) and (d) show characteristic maps A3 during high-speed driving.
H and B3H are shown, respectively. Characteristic maps AI, Δ2. A3L and A3H are used to drive a solenoid 49 of a flow rate control valve device 40 that controls the flow rate supplied to the servo valve 14. Also, characteristic map B1. B
2. B3L and B3H are used to drive a solenoid 27 of an electromagnetic valve 20 that bypass-controls both end chambers of the power cylinder 15. In vehicle speed control, as can be seen from the characteristic map AI, the control coefficient αA related to the current IOA to be applied to the solenoid 49 increases as the vehicle speed (2) increases. Regarding the steering angle characteristics, as can be seen from the characteristic map B2, the control current Ill, which is proportional to the current IOB applied to the solenoid 27, increases as the steering angle θ increases. That is, in the former case, the amount of supply to the servo valve 14 is reduced, and in the latter case, the bypass flow rate of the power cylinder 15 is increased, thereby making the handle heavier. On the other hand, regarding the steering angular velocity δ, the solenoid 49.27
Both are controlled by the same characteristics. When driving at low speed, the drive current for solenoid 49.27 is IOA. The control coefficients βAL and β[IL related to IO[1 are controlled so that the larger the steering angular velocity becomes, the smaller the control coefficients become, thereby increasing the sensitivity. That is, by increasing the supply amount to the servo valve 14 and decreasing the bypass flow rate of the power cylinder 15, the setting is made so that the faster the steering wheel is turned, the lighter the steering becomes. Also, when driving at high speed, solenoid 49.
Control coefficient βA1 related to drive current IOA, l0II of 27
1, β and 1 are controlled so as to increase as the steering angular velocity δ increases, so that the sensitivity decreases. That is,
By reducing the supply m to the servo valve 14 and increasing the bypass flow rate of the power cylinder 5, it is set so that the faster the steering wheel is turned, the heavier the steering becomes. ! Figure 4 shows the CPU used in the control device of this example device.
61 is a flowchart showing the processing procedure of No. 61. CPU
61 starts execution from step 100. In step 100, the vehicle speed 2, steering angle θ, and steering angular velocity are read. Next, in step 102, a control coefficient αA corresponding to the vehicle speed is determined from the characteristic map A1 shown in FIG. 5(a). Next, in step 104, a control current IA proportional to the drive current IOA corresponding to the steering angle θ is searched from the characteristic map A2 also shown in FIG. 5(C). In step 106, the current vehicle speed ■ is compared with the upper limit vehicle speed vh, and if it is smaller than that, the process moves to step 108, and the control coefficient βA according to the steering angular velocity δ is determined according to the characteristic map A3L of FIG. 6(a).
Then, in step 110, a control coefficient βA11 corresponding to the steering angular velocity δ is searched from the characteristic map A 3 H shown in FIG. 6(C). Then, in step 112, the optimum control coefficient βA corresponding to the vehicle speed ■ is calculated by supplementing the characteristics shown by the characteristic maps Δ3L and Δ3H according to the vehicle speed ■. Next, in step 114, the drive current IOA for driving the solenoid 49 is calculated by the product of the control coefficient βA determining the sensitivity regarding the steering angular velocity δ, the control coefficient αA regarding the vehicle speed, and the control current IA regarding the steering angle. Next, the process moves to step 116 and a control signal is output to the solenoid drive circuit 75 to drive the solenoid 49. As a result, the sensitivity is controlled to be most suitable for the driving condition of the vehicle and the steering condition of the steering wheel at that time, and an auxiliary steering force is generated from the power cylinder 15 in accordance with the sensitivity. On the other hand, if the current vehicle speed is higher than the upper limit vehicle speed vh in step 106, steps 140 and 142 are performed to perform control according to the steering angular velocity δ from the characteristic map A3H for the steering angular velocity at high vehicle speeds shown in FIG. 6(c). Coefficient β8:1
seek. Steps 118 to 132 are performed using the solenoid 27.
This is a step for determining a drive current for driving the , and the processing method is the same as steps 100 to 116 described above. That is, in step 118, FIG.
Control coefficient α according to vehicle speed from characteristic map B1 shown in b)
Search B. Next, in step 120, a control current IB corresponding to the steering angle is searched from the characteristic map B2 shown in FIG. 5(d), and in step 122, the current vehicle speed
If it is determined that it is lower than ) is searched for the control coefficient β[111 according to the steering angular velocity δ. In step 128, the control coefficient βB is determined according to the current vehicle speed.
is obtained by complementing βBL and βBl+. Step 13
0, the determined control coefficient αB1 control current IB and
A drive current JOB for driving the solenoid 27 is calculated according to the control coefficient βB, and the current value IO is determined in step 132.
A control signal is output in response to B, and the solenoid 27 is driven. As a result, an optimum sensitivity characteristic regarding the steering angular velocity can be obtained depending on the vehicle speed. As described above, in this embodiment, a hydraulic power steering device has been described, but the present invention is applicable not only to a hydraulic power steering device but also to an electric power steering device. In addition, two solenoid valves are provided to control the sensitivity: a solenoid valve 20 that bypasses the high-pressure chamber and low-pressure chamber of the power cylinder, and a solenoid valve 48 that changes the discharge capacity of the pump. Either one is fine. Further, each solenoid valve is controlled according to the three parameters of vehicle speed, steering angle, and steering angular velocity, but these parameters are not limited to these, and can also be controlled by these parameters. Solenoid valve is optional. [Effects of the Invention] The power steering device of the present invention increases the sensitivity as the steering angular velocity increases at low vehicle speeds, decreases the sensitivity as the steering angular velocity increases at high vehicle speeds, and decreases the sensitivity at intermediate vehicle speeds. It has a control device that adjusts the sensitivity with an intermediate characteristic between the characteristics of . Therefore, regardless of the magnitude of the vehicle speed, a sensitivity characteristic regarding the steering angular velocity that is most desirable for the vehicle speed at that time is obtained, and the steering loss feeling is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a device according to a specific embodiment of the present invention, and FIG. 2 is a pipe line that bypasses a high pressure chamber and a low pressure chamber of a power cylinder used in the device according to the embodiment. 3 is a cross-sectional view of a flow control valve device that controls the flow rate of pressure oil supplied to the servo valve of the device of the same embodiment, and FIG. 4 is a cross-sectional view of the solenoid valve provided in the device of the embodiment. A flowchart showing the processing procedure of the CPU used in the control device. Fig. 5 is a characteristic diagram for determining the control current of the solenoid valve related to vehicle speed and steering angle. Fig. 6 is a characteristic diagram for determining the control current of the solenoid valve related to the steering angular velocity. FIG. 4 is a characteristic diagram for determining drive current. 14... Servo valve 15... Power cylinder 22... Pump 27.49...
Solenoid 40...Flow control valve device 48...
Solenoid valve 60...''Electronic control device 69...Steering angle sensor 74°...Vehicle speed sensor Fig. 2 Fig. 3 Fig. 4 Fig. 6 (B3L)

Claims (3)

[Claims] (1) An auxiliary force generating means that generates an auxiliary force that assists the steering force of the automobile in response to a control signal from a control device; a steering angular velocity detector that detects a steering angular velocity of a steering wheel of the automobile; and a steering angular velocity detector that detects the steering angular velocity of a steering wheel of the automobile; A vehicle speed detector that detects speed, the steering angular velocity detector, and signals from the vehicle speed detector are input to generate an auxiliary force for manual torque that is input to the steering wheel of the automobile according to the detected steering angular velocity and vehicle speed. and a control device for controlling the auxiliary force output by the auxiliary force generating means according to the sensitivity by changing the sensitivity, which is a ratio of the vehicle speed. When the vehicle speed is low, the auxiliary force is controlled using a low vehicle speed characteristic that increases the sensitivity as the steering angular velocity increases, and when the vehicle speed is high, the auxiliary force is controlled using a high vehicle speed characteristic that decreases the sensitivity as the steering angular velocity increases. A power steering system characterized in that when the vehicle speed is an intermediate speed, the auxiliary force is controlled using an intermediate vehicle speed characteristic between the low vehicle speed characteristic and the high vehicle speed characteristic corresponding to the vehicle speed. (2) The power steering according to claim 1, wherein the control device has a storage device that stores the low vehicle speed characteristic, the high vehicle speed characteristic, and the intermediate vehicle speed characteristic corresponding to the vehicle speed. Device. (3) The control device includes a storage device that stores the low vehicle speed characteristics and the high vehicle speed characteristics, and a control device that uses the low vehicle speed characteristics and the high vehicle speed characteristics stored in the storage device to determine the speed according to the detected vehicle speed. 2. The power steering system according to claim 1, further comprising an intermediate vehicle speed characteristic calculation device that calculates the intermediate vehicle speed characteristic by interpolation.