JPS629449B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an automobile suspension, and more particularly to an automobile suspension that includes a damper with variable damping force and that controls the damping force depending on the situation. In an automobile suspension, an example of a system that controls the damping force of a damper according to the situation is as shown in Utility Model Application Publication No. 109008/1983, which changes the damping force according to the vehicle speed. It is known to always obtain favorable handling characteristics. This enhances understeer characteristics at high speeds, and provides neutral steering or weak oversteer characteristics at low speeds, ensuring stable handling characteristics at all times as the vehicle speed changes. However, there are various factors other than vehicle speed as changes in the situation that require changes in handling characteristics. For example, the size of the steering angle is closely related to the required handling characteristics, and it is desirable that the understeer characteristics be weaker when the steering wheel is turned significantly.
That is, it is desirable that the understeer characteristic be weakened when the steering angle is large, and strengthened when the steering angle is small. Therefore, sufficient running stability cannot be ensured only by control according to vehicle speed. For example, when you turn the steering wheel suddenly and change the direction of travel of the car, the understeer characteristic is weakened, and if you approach oversteer, the response will be better and the steering will be easier. However, when the vehicle is traveling straight without turning the steering wheel, it is desirable to have strong understeer characteristics because it improves straight-line performance. The understeer characteristic is particularly effective in correcting disturbances when the car is subjected to disturbances, and when this characteristic weakens, the straight-line stability decreases, making the car dangerous, especially at high speeds. Therefore, when the steering angle changes, it is desirable to always be able to obtain an appropriately strong understeer characteristic. The present invention has focused on this point, and an object of the present invention is to provide a suspension for an automobile that can always obtain desirable steering characteristics in accordance with changes in the steering angle. In order to achieve this objective, the suspension of the present invention is characterized in that the damping force of the damper is made variable, and this is controlled in accordance with changes in the steering angle, so that desired steering characteristics are always obtained. be. That is, the suspension of the present invention is provided with a damper unit that changes the damping force by changing the fluid passage area in the damper on at least one of the front wheel and the rear wheel among the front and rear wheel suspensions, and the damper unit's damping force is changed. The force is controlled by electromagnetic means, and this electromagnetic means receives the output of a steering angle sensor that detects the steering angle and adjusts the damping force of the damper unit on the front wheel side to the damping force of the damper unit on the rear wheel side during steering. The present invention is characterized in that the control is performed by a control means that outputs a control signal that makes the ratio smaller than when the vehicle is not steered. Here, the damping force of the damper unit on the front wheel side is
Making the ratio of the damping force of the rear wheel side damper unit smaller during steering than when not steering means to increase the damping force on the rear wheel side when steering while keeping the front wheel side damping force constant, and vice versa. There are three cases: when the front wheel side is made smaller while keeping the wheel side constant, and when both are changed in the opposite direction, that is, when the front wheel side is made smaller and the rear wheel side is made larger (in each case, when not steering, the (the damping force is changed in the direction of). Hereinafter, to simplify the explanation, the damping forces of the front and rear wheel damper units will be expressed as CF and CR, respectively.
Since the ratio of CF to CR is expressed as CF/CR, the above three cases mean that CF/CR during steering is smaller than CF/CR during non-steering. This can be expressed as shown in Table 1.

[Table] Decreasing CF/CR weakens the understeer characteristics, so it is possible to weaken the understeer characteristics during steering and improve steering control.
In the present invention, as described above, CF/CR is changed depending on the magnitude of the steering angle, so that desirable understeer characteristics can always be obtained, and good maneuverability and running stability can be realized. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an automobile equipped with a suspension according to an embodiment of the present invention, and FIG. 2 shows a system diagram of its main parts. In this embodiment, front wheel suspension 1, 1, rear wheel suspension 2,
A damper unit with variable damping force is provided in each of the damper units 2, and these are controlled by a controller 3. The controller 3 receives an output from a steering angle sensor 5 provided on the steering wheel 4 and detects the magnitude of the steering angle through a lead wire 3a, and is connected to the front and rear wheel suspensions 1, 1, and 3 having built-in damper units with variable damping force. A control signal is sent to 2 and 2 through lead wires 3b and 3c. Also,
In this embodiment, the output from the speedometer 6 is also input through the lead wire 3d. Furthermore, an auto/manual selector switch 7 is connected to the controller 3 through a lead wire 3e. As shown in Figure 2, each suspension 1,
1, 2, 2 are actuators 1a, 1a, 2a, 2a made of electromagnetic means, and damper units 1b, 1b, which can change the damping force by the actuators 1a, 1a, 2a, 2a.
2b, 2b, and this damper unit 1b, 1b,
A controller 3 is provided with coil springs 1c, 1c, 2c, 2c for further supporting springs 2b, 2b, and receives a signal from a steering angle sensor 5.
The output from the motor is inputted to the actuators 1a, 1a, 2a, 2a of the left and right front and rear wheel suspensions 1, 1, 2, 2 through lead wires 3b, 3c. The actuators 1a, 1a, 2a, 2a receiving this output, that is, the control signal, control the damping force of the variable damping force damper units 1b, 1b, 2b, 2b to a magnitude corresponding to the steering angle. For example, if the steering angle sensor 5 detects a steering angle equal to or greater than a predetermined value and outputs a signal (voltage equal to or greater than a predetermined value) indicating that the steering angle is large, the controller 3 receives this signal and activates the actuators 1a, 1a. ,2
a, 2a to drive the front wheel damper unit 1.
The damping force (CF) of the rear wheel damper units 2b and 2b is increased, thereby reducing CF/CR. Specifically, as shown in FIG. 3, for example, when the output of the steering angle sensor 5 exceeds a predetermined value, the positive input of the comparator 3A of the controller 3 increases, outputting a high output (H), and increasing the output of the comparator 3A.
The base voltage of a transistor 3C connected to the output of the comparator 3A via an inverter 3B is lowered to turn off the transistor 3C, and the comparator 3A
The base voltage of the transistor 3D connected to the output of the transistor 3D is increased to turn on this transistor 3D, and the actuators 1a, 1a (solenoids of electromagnetic means) on the front wheel side connected to the collector side of the former transistor 3C are demagnetized. This reduces the damping force (CF) of the suspensions 1, 1 on the front wheels, and drives the actuators 2a, 2a (solenoids of electromagnetic means) on the rear wheels connected to the collector side of the latter transistor 3D. It is possible to increase the damping force (CR) of the side suspensions 2, 2, thereby decreasing CF/CR and weakening the understeer characteristics (standard understeer). In the straight-ahead state, the output of the steering angle sensor 5 is below a predetermined value, so the output of the comparator 3A becomes a low output (L), and the transistor 3C connected via the inverter 3B is turned on to increase the damping force (CF) on the front wheel side. ), reduce the damping force (CR) on the rear wheel side, and increase CF/CR to strengthen the understeer characteristics. Note that the output of the speedometer 6 (FIGS. 1 and 2), which is a vehicle speed sensor, is input to the controller 3 together with the output of the steering angle sensor 5, and in addition to the above-mentioned damping force control by the steering angle sensor 5, This enables control according to vehicle speed. This control according to vehicle speed is, for example, as conventionally known, control that strengthens understeer characteristics at high speeds, that is, control that performs control on vehicle speed (V) in the opposite direction to control on steering angle (θ). and,
Control that weakens understeer characteristics as the vehicle speed increases during steering, i.e., a control that multiplies the steering angle (θ) by the square of the vehicle speed (V ² ) to suppress roll caused by centrifugal force during steering (θ×V ² ) There are two possible control methods for weakening the understeer characteristics depending on the magnitude of . Although the output of the vehicle speed sensor 6 is not used in FIG. 3, examples of the above two types of control using the output of the vehicle speed sensor 6 will be explained in the embodiments shown in FIGS. 4 and 5. (The former example in which the steering angle and vehicle speed are controlled in the opposite direction is shown in the embodiment shown in Fig. 5.
The control for ^V2 will be explained using the embodiment shown in FIG. ) In addition to the above-mentioned automatic automatic control, the automatic manual changeover switch 7 can also be used to manually change the damping force ratio (CF/CR) of the front and rear wheels.
It allows manual control. Next, FIG. 4 shows a second embodiment. In this embodiment, the output θ of the steering angle sensor 5 and the output S of the vehicle speed sensor 6, which are input to the controller 30, are the same as the steering angle θ, and the vehicle speed V is the output S of the vehicle speed sensor.
The output V converted by the converter 31 that converts into voltage is multiplied by the multiplier 32 to obtain V ² , and then input to the multiplier 33 to obtain θ×V ² , and this output θ×V ₂ The buffer 34a and the amplifier 34b
The damping force is transmitted to the actuators 1a and 2b of the front and rear wheels through the damping force to control the damping force. In other words, the damping force ratio between the front and rear wheels depends on the magnitude of the product of the square of the vehicle speed (V) and the steering angle (θ).
The magnitude of CF/CR is controlled so that the larger this value (θ×V ² ) is, the smaller it becomes. This makes it possible to perform damping force control on the steering angle multiplied by the influence of centrifugal force that is proportional to the square of the vehicle speed. Next, an embodiment will be described in which the damping force of the front and rear wheels is controlled according to a combination of vehicle speed and steering angle. This third embodiment performs basic control of reducing the magnitude of CF/CR during steering, while
Furthermore, the size of CF/CR is changed depending on the vehicle speed. In other words, the CF/CR is made larger at high speeds than at low speeds to strengthen understeer characteristics at high speeds.
This relationship can be expressed as shown in Table 2.

【table】

[Table] In Table 2, "soft" means that the damping force (CF, CR) is small, and "hard" means that the damping force is large. Therefore, Table 2 shows that the understeer characteristics are weakened by changing the damping force (CR) of the rear wheels from soft to hard when steering both at low speeds and high speeds. When the car goes from high to high, the damping force (CF) of the front wheels goes from soft to hard to enhance understeer characteristics. A circuit diagram of such an embodiment is shown in FIG. As is clear from FIG. 5, the output from the vehicle speed sensor 6 is input to the first comparator 36 of the controller 35, which turns on and off the first transistor 37 connected to the output of the first comparator 36. The actuators 1a, 1a of the connected front wheel suspension 1 are controlled.
(At high speed, the output of the first comparator 36 becomes H and turns on the actuator, making the software hard.) On the other hand, the output of the steering angle sensor 5 is input to the second comparator 38, and its output is 2 transistor 39 is turned on and off, and the actuators 2a, 2a of the rear wheel suspension 2 connected thereto are controlled. (During steering, the output of the second comparator 38 becomes H, and by turning on the actuator, the software is made hard.) Next, a specific example of a damper unit with variable damping force is shown in Figs. 6 and 7. Explain in detail. As shown in FIG. 6, a suspension 2 has an upper end fixed to a part 10 of the vehicle body via an elastic body 11.
A lower case 16 consists of an upper case 13 that forms an air chamber 12, and an outer cylinder 14 and an inner cylinder 15 that are assembled so that their upper ends enter and exit the lower end of the upper case.
, a connecting body 17 that airtightly connects the insides of the upper and lower cases 13 and 16, and a piston rod that coaxially penetrates the insides of the upper and lower cases 13 and 16 and is slidable up and down with respect to the inner cylinder 15 of the lower case 16. 18, a main valve 19 fixed to the lower end of the piston rod 18, and a bottom valve 20 fixed to the lower end of the inner cylinder 15.
The oil chamber in the inner cylinder 15 is divided into a chamber A above the main valve 19 and a chamber B below the main valve 19, and further divided into an outer cylinder 14 and an inner cylinder 1.
The upper end of the oil chamber C between 5 and 5 communicates with the upper end of chamber A, and the lower end communicates with the lower end of chamber B, respectively. Further, a control rod 21 passes vertically through the center of the piston rod 18, and the upper end 21a of the control rod 21 is engaged with a rotary key 22 which is rotated by an external force so as to be able to transmit rotational force. A communication hole 1 is provided at the lower end of the control rod 21, which is bored in the lower end 18a of the piston rod 18 so as to communicate chamber A and chamber B.
An orifice 21b communicating with the piston rod 8b is provided, and by rotation of the control rod 21, communication between the orifice 21b and the communication hole 18b of the lower end portion 18a of the piston rod is turned on and off. Details of the structure of the lower end of the piston rod 18, including the lower end of the control rod 21, the main valve 19, and the bottom valve 20 will be described later with reference to FIG. The relative vertical movement of the upper case 13 and the lower case 16 is achieved not only by the air spring provided by the air chamber 12 but also by a spring 30 (held between the upper and lower spring cases 13a and 16a fixed to the upper and lower cases 13 and 16). It is elastically absorbed by 2c) in FIG. Brackets 16b and 16c fixed to the outer surface of the lower case 16 are for fixing a wheel support structure including a wheel hub that rotatably supports the wheels, so that the wheels can move up and down on the part 10 of the vehicle body. is maintained. That is, the vehicle body is suspended by wheels and elastically supported so as to be movable up and down. In the suspension constructed as described above, the A, B, and C chambers in the lower case 16, the communication passages that communicate these, and the valves 19 and 20 constitute a damper unit to generate a damping force.
The details of the structure of the damper unit that generates the damping force will be explained below with reference to FIG. As shown in FIG. 7, the main valve 19 has a contraction side orifice 19a and an expansion side orifice 19b.
are formed, and the respective orifices 19a, 19
Valves 19c and 19d are provided at b. Similarly, the contraction side orifice 20 is installed on the bottom valve 20.
A and an extension side orifice 20b are formed, and valves 20c and 20d are provided respectively. In the part of the main valve 19 where chamber A and chamber B are adjacent, orifices 19a and 1 are used to increase the damping force.
9b, but when reducing the damping force, the control rod 21 is rotated so that the orifice 21b at the lower end of the control rod 21 and the communication hole 18b at the lower end 18a of the piston rod 18 communicate with each other. and control rod 21
A and B are connected to each other through a communication hole 18A that is open from the inside of the orifice 21b at the lower end to the B chamber.
The rooms are communicated. Therefore, the fluid passage area between chambers A and B increases, and the damping force of this damper unit decreases. The control rod 21 is rotated by rotating a rotary key 22 engaged with the upper end 21a (for example, 90 degrees), thereby rotating the orifice 2.
1b and the communication hole 18b are turned on and off.
The rotary key 22 is driven and rotated by electromagnetic means such as a solenoid, and performs variable control of the damping force of the damper unit. When using the damper unit configured as above on the rear wheel side, control rod 2 should be
The orifice 21b of No. 1 is turned on to increase the fluid passage area between chambers A and B to obtain a relatively small damping force, and when the steering angle sensor detects a large steering angle. The orifice 21b may be turned on to reduce the area and increase the damping force. When using this for the front wheels, the orifice 21b is turned on during steering and turned off when the vehicle is running straight. Furthermore, when this is used for both the front and rear wheels, the above two types may be used in combination as they are. The automobile suspension according to the present invention uses a damper with variable damping force as described above, and controls this according to changes in the steering angle to reduce CF/CR during steering. The understeer characteristic, which is sometimes weakened, can be maintained at a desired level, and stable driving can always be achieved regardless of changes in the steering angle. Note that in the above embodiment, the magnitude of the damping force is switched between two types, large and small, but this is due to the orifice 2.
By continuously changing the communication cross-sectional area between the communication hole 1b and the communication hole 18b, it can be changed continuously, and if the output of the steering angle sensor is also a continuous analog value, subtle changes in the steering angle can be made. It is also possible to perform continuous control according to changes. Of course, it goes without saying that multistage control in which this is divided into three or more stages is also possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an automobile equipped with the suspension of the present invention, Fig. 2 is a system diagram of an embodiment of the suspension of the present invention, and Figs. 3 to 5 show specific examples of Fig. 2. FIG. 6 is a sectional view showing an example of a damper unit used in the suspension of the present invention, and FIG. 7 is a sectional view showing the main part of FIG. 6 in detail. 1, 2... Suspension, 1a, 2a... Actuator, 3... Controller, 5... Steering angle sensor, 6... Vehicle speed sensor, 7... Automatic manual changeover switch, 12... Air chamber, 13...
Upper case, 14... Outer cylinder, 15... Inner cylinder, 16...
...Lower case, 18...Piston rod, 19...
Main valve, 20...Bottom valve, 18b...
...Communication hole, 21...Control rod, 21b
...Orifice, 22...Rotary key.

Claims (1)

[Claims] 1 Suspension means for suspending a vehicle body on the front wheels and rear wheels, a damper unit that changes the damping force by changing the fluid passage area, which is provided on at least one of the front wheels and the rear wheels among the suspension means, An electromagnetic means for changing the above-mentioned fluid passage area of the damper unit, a steering angle sensor that detects the steering angle, and an output of the steering angle sensor that adjusts the damping force of the front wheel side damper unit to the damping force of the rear wheel side damper unit. An automobile suspension comprising a control means for inputting a control signal to the electromagnetic means to make the ratio smaller during steering than when not steering.