JPH01233166A - Power steering device - Google Patents

Abstract

PURPOSE:To improve smoothness of steering, by a method wherein a resultant force of a steering force and the auxiliary steering force of an electric motor is detected, and when the resultant force exceeds a given steering force, drive of the electric motor is controlled in relation to only a value equivalent to an amount by which the resultant force exceeds a steering target value. CONSTITUTION:When a steering wheel 1 is steered, steering torque is transmitted to a gear 3 through a steering column shaft 2. The power of a DC motor 5 is imparted to the gear 3 through a pinion 4. A resultant force of a manual steering force and an auxiliary steering force is transmitted to a rack 7 through a pinion 6, and a rack shaft 8 is displaced in the direction of the width of a car to steer wheels 9. In this case, resultant torque TR is detected by means of a load torque sensor 10, and the resultant torque TR is compared with a target value TK. In the case of TR>TK, an error signal based on a deviation therebetween is outputted to the motor 5 to impart the auxiliary steering forced to a steering system.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a power steering device that provides power assistance for a vehicle such as an automobile, and more particularly to a power steering device in which steering torque is assisted by an electric motor. .

(Prior Art) In recent years, so-called power steering devices have been installed in vehicles from the viewpoint of maneuverability and running stability, and their use has become remarkable. The purpose of power steering is to reduce the driver's burden on steering, and the various functions required include reduction of steering force, a feedbank of precise reaction force in response to steering, and smooth steering. Furthermore, it is also required that the power required for devices that implement these various functions be small.

There are various types of power steering devices, such as hydraulic type and electric type, but the electric type is attracting attention because of its simple system. Conventional electric power steering devices of this type include those described in Japanese Patent Publication No. 50-33584 and Japanese Patent Application Laid-Open No. 62-175263, for example.

The former device is provided with a vehicle speed detector and a road condition/condition detector, and detects a vehicle speed signal and a road surface condition signal, respectively. Based on these signals, the auxiliary steering force of the electric motor is increased or decreased, and the relative strength (I-luke ratio) of the auxiliary steering force of the electric motor relative to the manual steering force is varied.

On the other hand, in the latter case, the steering force from the manual steering column is transmitted to the pinion shirt 1 to the tip of the steering column shirt I through the steering column shirt I, and is transmitted to the wheels from the steering column shaft that meshes with the pinion shirt I.

Further, the auxiliary power generated by the electric motor is transmitted from the electric motor to the steering column shaft via a set of gears.

(Problem to be Solved by the Invention) However, in such a conventional power steering device, the steering torque (torque generated by human power) is detected, and the manual steering force is determined based on this detection signal. Since the structure is such that the torque ratio between the electric motor and the auxiliary steering force is varied to reduce the steering torque, the following problems have occurred.

(1) Since the torque generated in the electric motor differs depending on the difference between the steering speed of the steering wheel and the shaft angular speed of the electric motor, the steering torque changes depending on the steering speed. Zunawachi,
As shown in the steering angle O3-steering I torque TS and load torque TR characteristic diagram shown in FIG.
varies depending on the steering speed. This greatly affects the steering sensation for the driver.

(n) Since the load torque T□ changes between the stopped state and the running state of the vehicle, it is especially necessary to prevent the steering I and the torque from being too light in the running state. In other words, as shown in Fig. 6, vehicle speed - negative load
As shown in the steering torque Ts characteristic diagram, in order to prevent the steering torque Ts from decreasing at high speeds, it is necessary to feedback control the magnitude of the steering torque Ts using the vehicle speed and steering angle as parameters, which requires complicated It becomes a control and leads to high costs.

(Objective of the Invention) Therefore, the present invention detects the combined force of the manual steering force and the auxiliary steering force generated by the electric motor, and performs control based on the detection result, thereby avoiding complicated control with a simple configuration. (
The purpose is to improve the smoothness of steering by feeding back the appropriate reaction force in response to steering.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the power steering system according to the present invention controls an electric motor so as to achieve a steering target value by means of a control means according to the steering force applied to the steering wheel, and uses this electric motor to provide assistance. A power steering device that applies a steering force is provided with a composite force detection means for detecting a composite force of the steering force of the steering wheel and the auxiliary steering force of the electric motor, and the control means is configured to detect a composite force of the steering force of the steering wheel and an auxiliary steering force of the electric motor, The electric motor is controlled so as to provide an auxiliary steering force corresponding to the amount of force.

(Function) In the present invention, the combined force of the steering force of the steering wheel and the auxiliary steering force of the electric motor is detected, and when this combined force exceeds a predetermined steering wheel steering force, the amount by which this exceeds the steering target value is The motor is controlled to generate auxiliary power accordingly.

Therefore, an appropriate reaction force corresponding to the steering is feedhacked, improving the smoothness of the steering, and providing a comfortable steering feeling to the driver.

(Example) Hereinafter, the present invention will be explained based on the drawings.

1 to 6 are diagrams showing an embodiment of a power steering device according to the present invention, and are examples in which the present invention is applied to a power steering device for a vehicle such as an automobile.

First, I will explain the configuration. In FIG. 1, 1 is a steering wheel, and the steering torque Ts of the steering wheel 1 is transmitted to a gear 3 provided at an intermediate portion of the steering column shirts 1 and 2. Motor 1 Luk TM (auxiliary steering force) from a DCC morph (electric motor) is also transmitted to the gear 3 via the pinion 4 . The combined torque of the steering torque Ts and the motor torque T is transmitted to a pinion 6 provided at the tip of the steering column shaft 2, and the pinion 6 meshes with a rack 7. Wheels 9 are connected to both ends of the rack 7 via a rank shaft 8. Therefore, when the steering wheel 1 is steered, the pinion 6 rotates, and the rack 7 is engaged with the rack 7 to move from side to side in the figure. That is, the rotational displacement of the steering wheel 1 is converted into a linear displacement of the rack 7, and the wheels 9 are steered.

Reference numeral 10 denotes a load torque sensor (combined force detection means), and the load I/lux sensor 1o detects the combined torque and outputs a sensor output corresponding to the combined torque to an error detection circuit 11 (not shown) which will be described later. Note that the load torque sensor 10 may be a load sensor.

FIG. 2 is a block diagram showing the overall configuration described above.

In this figure, reference numeral 11 is an error detection circuit that detects an error in the steering torque. The target value K of the torque is input. The error detection circuit 11 compares the sensor signal 1' with a steering torque target value (manual torque target value) TK, and outputs the result as an error signal C to the control circuit 12 (control means). The control circuit 12 generates a drive signal S for driving the DC motor 5 based on the error signal e.
, and the DC motor 5 applies motor torque T as auxiliary power to the gear 3 via the pinion 4 (as shown) in response to the drive signal S. Motor torque TM for gear 3
and the steering I and torque Ts from the steering wheel 1 (not shown), and their combined torque is output to the rack 7 via the pinion 6.

The rack 7 transmits the synthetic torque to a vehicle 9 (not shown) via a rack seat 8 (as shown). At this time, the pinion 6 has a load torque TR generated by the load side (rack 7 and vehicle 9) due to the composite torque and the composite torque.
is entered.

Next, the effect will be explained.

In FIG. 1, when a steering wheel 1 is steered, the steering torque Ts is transmitted to a gear 3 via a steering column shaft 2, and a DC motor 5 is connected to the gear 3.
A motor torque T is also transmitted from the motor via the pinion 4. These combined torques are transmitted to the input shaft sides of the load 1 to the lux sensor 10 and output to the error detection circuit 11 as the sensor output signal TsEN. The combined torque is then transmitted from the output shaft side of the load torque sensor 10 to the rank 7 via the pinion 6. At this time, the steering position is determined when the moments are balanced between the composite torque and the load torque TR applied to the output shaft side of the load torque sensor 0.

First, the operations up to this point will be explained with reference to FIG. 2, focusing on the control aspect. The resultant torque is the load torque sensor 0.
The sensor output signals Ts and N corresponding to the composite torque are output to the error detection circuit 11. here,
From the relationship between the above-mentioned composite torque and load torque T3, the following relational expression (2) is established.

TR=Ts, N=Ts+T, -■In other words, changes in the load torque TR are sequentially detected by the load torque sensor 0 and sent to the error detection circuit 1 as a sensor signal Ts□.
1 will be feed hacked. The sensed signals T s and H are compared and calculated with the target value TK of the steering torque in the error detection circuit 11, and the calculation is executed according to the following equation (0) to obtain the error output e.

e=T, -TK・・・・・・・・・・・・・・・・・・
■The steering torque target value TK is sequentially input to the error detection circuit 11 according to the steering torque Ts from a data map stored in advance in a RAM (not shown), etc.
K is set to an optimum value corresponding to when the vehicle is running at low speed, when the vehicle is running at high speed, when the vehicle is stopped, etc. That is, TK is set in advance in the data map as a function of vehicle speed (2). This is to provide an appropriate reaction force, or response, to the steering. It eliminates the feeling of instability caused by the rudder being too light, especially when driving at high speeds, while also reducing the steering force when the load is heavy, such as when the steering wheel is stationary at low speeds. This is to make it sufficiently light.

Next, the error signal e is output to the control circuit 12, and when TR>T, the control circuit 12 converts the error signal e into a drive signal S for the DC motor 5 and outputs it to the DC motor 5. This drive signal S. When the DC motor 5 is driven, the DC motor 5 generates auxiliary power, and this auxiliary power is transmitted to the gear 3 as a motor torque TM via a pinion 4 (not shown). Therefore, the load torque sensor 10, the error detection circuit 11, and the control circuit 12 sequentially execute feed hack control with the TR as the control target.

Returning to FIG. 2 again, when T,>TK, the composite torque subjected to feedback control (error correction) as described above is transmitted to the rack 7 via the pinion 6 on the output side of the load torque sensor 10. The rack 7 converts the rotational displacement of the pinion 6 due to the combined torque into a linear displacement, and steers the vehicle 9 to a predetermined steering angle θ position (a position in balance with TR) via a rank shaft 8 connected to both ends of the rack 7. . On the other hand, T
Drive signal S when R≦TK. is not output and the DC motor 5 is not driven, so only the steering torque Ts is applied to the rack 7.
and similarly steers the wheels 9.

Due to the above effects, the characteristics of this example are as shown in Figures 3(a) to (
C) and as shown in Figure 4.

FIGS. 3(a) to 3(c) are characteristic diagrams of steering angle θ3 vs. steering torque Ts when the vehicle speed V is V-0, low-speed running, and high-speed running, and it is clear from these figures. Even if there are differences in vehicle speed or steering speed, the steering torque T
s is stable without fluctuation. Figure 4 is a vehicle speed V-steering torque Ts characteristic diagram, where the steering torque Ts is the load torque TR.
It has the same characteristics as .

Therefore, unlike the conventional method, there are the following effects.

(1) By installing the load torque sensor 10 at a position to detect the composite torque of the steering torque Ts and the motor torque TM and setting the steering torque target value TK, the steering torque Ts exceeds the steering torque target value T. When the steering torque Ts reaches the steering torque target value T7, the motor torque T can be power assisted.

(IT> Since the steering torque Ts is not affected by the difference between the steering speed of the steering wheel and the angular velocity of the shaft of the DC motor 5 or by the change in load torque 1.8, an appropriate reaction force corresponding to the steering is feed-hacked. This improves the smoothness of the steering, making it possible to provide a more comfortable steering sensation to the driver.

(III) The control system is simplified and the cost of the power steering system is reduced.

(IV) Since the steering torque target value TK is set in advance as a function of vehicle speed, it is possible to eliminate the feeling of instability caused by light steering especially when driving at high speeds, while sufficiently lightening the steering force when driving at low speeds and under heavy loads. This allows you to get an appropriate steering response.

(Effect) According to the present invention, the combined force of the steering force of the steering wheel and the auxiliary steering force of the electric motor is detected, and when this combined force exceeds a predetermined steering wheel steering force, the Since the electric motor is controlled so that auxiliary power is generated only for the excess power, the appropriate reaction force corresponding to the steering is fed back regardless of differences in the motor shaft angular speed or fluctuations in the load per torque, ensuring smooth steering. In addition to improving steering performance, it is possible to provide a comfortable steering sensation for the driver.

[Brief explanation of the drawing]

1 to 4 are diagrams showing one embodiment of the power steering system according to the present invention, in which FIG. 1 is an overall configuration diagram thereof, FIG. 2 is a control block diagram of FIG. 1, and FIG. ) to (c) are diagrams showing the characteristics of the steering angle and steering torque, Figure 4 is a diagram showing the characteristics of the vehicle speed and steering torque, and Figure 5.6 is a diagram showing the characteristics of the conventional power steering system. FIG. 5 is a diagram showing the characteristics of the steering angle, steering torque, and load torque, and FIG. 6 is a diagram showing the characteristics of the vehicle speed, steering torque, and load torque. ■・・・Steering wheel, 5・・・・・・
DC motor (electric motor), 10... Load torque sensor (combined force detection means), 12... Control circuit (
control means).

Claims (2)

[Claims] (1) In a power steering system in which an electric motor is controlled by a control means so that a steering target value is achieved according to a steering force applied to a steering wheel, and the electric motor applies an auxiliary steering force, the steering force of the steering wheel and the electric motor are controlled. A composite force detection means for detecting a composite force with the auxiliary steering force is provided, and when the composite force exceeds a predetermined steering wheel steering force, the control means controls the electric motor only for the amount exceeding the steering target value. A power steering system characterized in that the electric motor is controlled so as to provide an auxiliary steering force according to the present invention. (2) The power steering system according to claim 1, wherein the steering target value is set as a function of vehicle speed.