JPH022750B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power steering device, and particularly to a power steering device that controls auxiliary force in accordance with centrifugal force applied to a vehicle body.

[Prior Art] Conventionally available power steering devices generally use a hydraulic device, a transmission device, etc. to provide steering assist force and change the assist force depending on the vehicle speed. Some vehicles increase the auxiliary force at low speeds to make the steering wheel lighter (making steering easier), and conversely reduce the auxiliary force at high speeds to make the steering wheel heavier (making steering more difficult).

The reason for making the steering wheel lighter when driving at low speeds is to reduce the burden on the driver when turning the steering wheel vigorously such as when parking in a garage or driving on a mountain road. In addition to improving running stability when driving, it also makes it difficult to make sudden turns such as so-called sudden steering.

[Problems to be Solved by the Invention] However, the method of simply reducing the steering assist force across the board during high-speed travel cannot reliably avoid the sharp turns described above during high-speed travel. That is, even if it is an expressway, the road has curves, so it is necessary to turn the steering wheel, and even if the steering wheel is somewhat heavy, it is necessary to be able to freely steer the vehicle. In that case, if something unexpected happens, such as when the driver discovers a foreign object on the road,
There have been times when I suddenly turned the steering wheel unexpectedly, and even though I was able to steer, the car turned sharply. the result,
Vehicles may also roll over.

The present invention was developed as a result of extensive research in view of these problems, and the purpose of the present invention is to provide a power steering force that captures the centrifugal force generated in the vehicle body and effectively prevents sharp turns during high-speed driving. There is.

[Means for Solving the Problems] This object includes a steering device that transmits steering force generated by steering wheel operation to the wheels, and a steering assist force generating means attached to the steering device that assists steering based on the steering wheel operation. In the power steering device, a steering angle sensor detects a steering angle due to a steering wheel operation, a vehicle speed sensor detects a vehicle speed, a calculation means calculates a centrifugal force applied to the vehicle body based on detection signals of both the sensors, and the vehicle speed and the vehicle speed. This is achieved by a power steering device characterized in that it is provided with a control means for controlling the auxiliary force outputted from the steering auxiliary force generating means to be reduced as the centrifugal force increases.

[Example] The present invention will be described below by giving examples and referring to the drawings.

Fig. 1 is a schematic configuration diagram showing a power steering device according to an embodiment, and Fig. 2 is an explanatory diagram of its concept, where 1 is a steering wheel, and 2 is a steering angle sensor that detects the rotation angle of the steering wheel provided on the handle post. ,
Reference numeral 3 denotes a rotary valve 3a provided in the rack and pinion portion, and a flow control valve 3 that controls the bypass amount of pressure oil sent from the rotary valve 3a to the cylinder 4, which will be described later.
a control valve consisting of a control valve 4, a cylinder provided in the rack part and generating an auxiliary force by hydraulic pressure;
6 is a vehicle speed sensor provided on the output shaft of the transmission, and 6 receives input signals from the steering angle sensor 2 and vehicle speed sensor 5 to control the output (hydraulic pressure) of the hydraulic pump to be constant regardless of the engine speed. , a control circuit for controlling the flow rate control valve 3b, 7 a hydraulic pump driven by the engine, and 8 an oil tank. A generating means is configured.

The cylinder 4 is partitioned into left and right working chambers by a piston 4a, and the piston 4a is connected to the left and right wheels 9.
Trunk rods 4b, 4c connected to a, 9b
is connected to.

Further, as shown in FIG. 3, the control circuit 6 includes an A-D converter 6 that converts an analog voltage signal from the potentiometer of the steering angle sensor 2 into a digital signal.
a, a microcomputer 6b that receives the output of the A-D converter 6a and a pulse signal proportional to the vehicle speed from the vehicle speed sensor 5, and performs calculation and control; an output signal via an output latch (not shown) in the microcomputer 6b; Therefore, the power transistor 6c controls the current flowing through the electromagnetic coil of the flow rate control valve 3b.
It is equipped with

Furthermore, the microcomputer 6b performs control according to a control program as shown in the flowchart of FIG. The process will be explained below along with the flowchart.

When a key switch (not shown) of the engine is turned on and the engine is started, initialization processing (not shown) is performed, and the processing shown in this flowchart is started, and step 20 is executed first.

In step 20, a pulse signal proportional to the vehicle speed from the vehicle speed sensor 5 is input, and the vehicle speed V is determined by the pulse interval or the number of pulses per unit time.
is calculated, and the process moves to the next step 21.

In step 21, the steering angle is determined from the detection signal of the steering angle sensor 2 inputted via the AD converter 6a, and the turning radius R of the vehicle body at that steering angle is calculated.

In the following step 22, the predetermined vehicle weight M and the steps 20 and 2 are determined in advance.
Based on the vehicle speed V and turning radius R calculated in 1,
The centrifugal force FR is calculated by the above formula: FR=M·V ₂ /R, and the process moves to the next step 23.

In step 23, the steering assist force F1 is calculated based on the centrifugal force FR calculated in the previous step 22, and the process proceeds to the next step 24.

In step 24, a linear function f of the vehicle speed V
(V) to calculate the auxiliary force F2, and then proceed to the next step 2.
The process moves to step 5.

In step 25, the auxiliary force F1 and the auxiliary force calculated in steps 23 and 24 are calculated.
F2 is added to find the control auxiliary force F.

In the following step 26, the magnitude of the flow control valve 3b drive signal necessary to generate the auxiliary force F is determined according to the magnitude of the vehicle speed F calculated in step 25 (for example, if duty control is used, the magnitude of the pulse signal is determined). A drive signal having the determined magnitude is outputted to the power transistor 6c via the output latch to control the flow rate control valve 3b. As a result, the bypass amount of pressure oil sent to the cylinder 4 is controlled, and the auxiliary force is controlled.

The process then returns to step 20, and the same process is repeated thereafter.

In this way, in this embodiment, in step 22,
Centrifugal force FR acting on the vehicle body from the vehicle body turning radius R determined by the steering angle θ, vehicle weight M, and vehicle speed V
is calculated, and in step 23, the auxiliary force F1 is calculated based on the size of this switching valve FR. As a result, if the vehicle weight M is constant, the auxiliary force F1 changes depending on the vehicle speed V and the turning radius R, as shown in Fig. 5A, that is, as the vehicle speed V increases and the turning radius R decreases. Furthermore, if the vehicle speed V and vehicle weight M are constant, as the steering angle θ increases (the radius of rotation R decreases), as shown in FIG.

By the way, since the centrifugal force FR is proportional to the square of the vehicle speed V, the auxiliary force F1 set accordingly is also set as a quadratic function of the vehicle speed V. Therefore, if the steering assist force is controlled only by this assist force F1, there will be a region where the assist force changes greatly with a slight change in the vehicle speed V, and a region where the assist force does not change much with a change in the vehicle speed V. area will occur.

Therefore, in this embodiment, the auxiliary force F2, which is a linear function of the vehicle speed V, is further calculated in step 30.
In step 31, the auxiliary force F used for control is set by adding this auxiliary force F2 to the auxiliary force F1 set according to the centrifugal force FR. That is, by controlling the steering assist force in consideration of the vehicle speed V in addition to the centrifugal force FR of the vehicle, it is possible to arbitrarily adjust the change in the assist force in response to changes in vehicle speed.

As a result, according to this embodiment, the centrifugal force FR of the vehicle is
The larger the steering force is, the smaller the steering assist force is (that is, the heavier the steering wheel is), which effectively prevents sudden turns caused by the driver's sudden steering. Optimal settings can be made taking into account moments, etc.
It becomes possible to improve the running stability of the vehicle over a wide vehicle speed range.

Here, the vehicle weight M used to calculate the centrifugal force FR in step 22 is determined by assuming that the vehicle is loaded with approximately half the specified loading weight (number of passengers). Although a predetermined fixed value may be used as in the embodiment, a weight sensor such as a load cell may be provided between the axle and the vehicle body to detect the actual vehicle weight, and the detection result may be used in step 22. It's okay. In addition, the calculation of the auxiliary force F1 in step 23 takes into account vehicle type-specific characteristics (drive system, vehicle body length, center of gravity position, etc.).
It is sufficient to use a mathematical formula determined experimentally depending on the situation.

Further, in the above embodiment, a hydraulic power steering device is described, but the present invention can also be applied to an electric type using a pulse motor etc. or a mechanical type using a variable ratio gear. It is possible to demonstrate the effect of

[Effects of the Invention] As detailed above, the power steering device of the present invention uses the switching valve and the vehicle speed as parameters for controlling the auxiliary force, and controls the auxiliary force according to the magnitude of the centrifugal force and the vehicle speed. are doing.

Therefore, according to the present invention, the steering assist force of the power steering device is reduced in accordance with the magnitude of the centrifugal force generated in the vehicle body, and by making the steering wheel heavier, it is possible to prevent sudden steering by the driver. It is possible to effectively prevent sudden turns and, as a result, to prevent rollover accidents and the like. In addition, since vehicle speed is used in addition to centrifugal force as a parameter for auxiliary force control, the generation characteristics of auxiliary force over a wide range of vehicle speeds can be set in consideration of the vehicle's moment of inertia, etc., and driving stability can be improved over a wide range of vehicle speeds. It becomes possible to increase over a range.

[Brief explanation of drawings]

FIG. 1 is a schematic system diagram showing the power steering device of the embodiment, FIG. 2 is an explanatory diagram of the same concept, FIG. 3 is a block diagram showing the control circuit, FIG. 4 is a flowchart showing the control program, and FIG. Figures A and B are explanatory diagrams for explaining the effects of the embodiment. 1... Steering wheel, 2... Steering angle sensor, 3...
Control valve, 3b...Flow rate control valve, 4...Cylinder, 5...Vehicle speed sensor, 6...Control circuit, 6
b...Microcomputer, 6c...Power transistor.

Claims (1)

[Scope of Claims] 1. A power steering device comprising: a steering device that transmits steering force from a steering wheel operation to the wheels; and a steering assist force generating means attached to the steering device that assists steering based on the steering wheel operation, comprising: a steering angle sensor that detects a steering angle caused by an operation; a vehicle speed sensor that detects vehicle speed; a calculation means that calculates centrifugal force applied to the vehicle body based on detection signals of both sensors; and control means for controlling the assist force outputted from the steering assist force generating means to be smaller.