JPS6147724B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an automobile suspension, particularly a spring means with variable spring characteristics in parallel with a damper,
The present invention relates to an automobile suspension in which the spring characteristics are controlled according to the situation. BACKGROUND ART In automobile suspensions, systems have been proposed in which the damping force of a damper is controlled depending on the situation. For example, as shown in Japanese Utility Model Application No. 55-109008, a vehicle is known in which the damping force is changed depending on the vehicle speed so as 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 suddenly turn the steering wheel and drastically change the direction of travel of the car, the understeer characteristic is weakened, and if you approach oversteer, the response is better and the steering becomes 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 makes the spring characteristics of the spring means provided in parallel with the damper variable, and controls this according to changes in the steering angle to always obtain desired steering characteristics. It is characterized by this. That is, the suspension of the present invention is provided with a spring means for changing the spring characteristic by changing the spring constant on at least one of the front wheel and the rear wheel among the front and rear wheel suspension, and a means for adjusting the spring constant of the spring means. When a steering signal is input from a steering sensor that detects steering and outputs a steering signal during steering, this adjusting means is configured to adjust the spring constant of the front wheel suspension to the rear wheel suspension during steering. The controller includes a controller that inputs a control signal to the adjustment means to make the ratio of the spring constant to the spring constant smaller than when the steering wheel is not being steered. Here, making the ratio of the spring constant of the front wheel suspension to the spring constant of the rear wheel suspension smaller during steering than when not steering means that, while the spring constant of the front wheels is constant, the spring constant of the rear wheels during steering is There are three cases: increasing the size, conversely, keeping the rear wheel constant and decreasing the front wheel, and changing both in the opposite direction, i.e., decreasing the front wheel and increasing the rear wheel. In this case, the spring constant is changed in the opposite direction to the above when the vehicle is not being steered). Below, to simplify the explanation, the spring constants of the spring means of the front and rear wheel suspensions are KF, respectively.
Expressed in KR. Since the ratio of KF to KR is expressed as KF/KR, the above three cases are
This means making KF/KR smaller than KF/KR when the vehicle is not being steered. This can be expressed as shown in Table 1.

[Table] Decreasing KF/KR weakens the understeer characteristics, so it is possible to weaken the understeer characteristics during steering and improve steering control.
Since the present invention changes KF/KR depending on the magnitude of the steering angle as described above, desirable understeer characteristics can always be obtained, and good maneuverability and running stability can be achieved. 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,
2 are provided with accumulators 1A and 2A for changing the spring constant, and these are controlled by a controller 3. The controller 3 receives the output from the steering angle sensor 5 provided on the steering wheel 4 and detects the magnitude of the steering angle through a lead wire 3a, and inputs the output from the steering angle sensor 5 provided on the steering wheel 4 through a lead wire 3a. A control signal is sent to the accumulators 1A, 2A through lead wires 3b, 3c. In this embodiment, the output from the speedometer 6 is also output from the lead wire 3d.
input through. 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,
Accumulators 1A, 2A equipped with actuators 1a, 1a; 2a, 2a made of electromagnetic means are connected to 1; 2, 2, and the air chambers in the accumulators 1A, 2A are controlled by the electromagnetic means to each suspension 1, 1; By communicating with the air chambers in the air springs 2 and 2, the spring constants KF and KR of the air springs can be adjusted.
is beginning to change. The output from the controller 3 that receives the signal from the steering angle sensor 5 is sent to the accumulators 1A and 2 of the left and right front and rear wheel suspensions through lead wires 3b and 3c.
It is input to actuators 1a, 1a; 2a, 2a of 2A. The actuators 1a, 1a; 2a, 2a that receive this output, that is, the steering signal, control the spring constants of the air springs 1b, 1b; 2b, 2b to become smaller or larger. 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 reduce the spring constant KF of the front wheel air springs 1b, 1b, and reduce the spring constant KF of the front wheel air springs 1b, 1b.
Increase the spring constant KR of b, which results in KF/
Reduce KR. 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, producing a high output H, and the output of the comparator 3A increases. The base voltage of the transistor 3C connected to the output of the comparator 3A is lowered to turn off the transistor 3C, and the base voltage of the transistor 3D connected to the output of the comparator 3A is increased to turn on the transistor 3D. , the front wheel side actuators 1a, 1a (solenoids of electromagnetic means) connected to the collector side of the former transistor 3C are demagnetized to reduce the spring constant KF of the front wheel side suspensions 1, 1, and the latter transistor 3D is demagnetized. The rear wheel side actuators 2a, 2a (electromagnetic means solenoids) connected to the collector side are driven to increase the spring constant KR of the rear wheel side suspensions 2, 2, thereby reducing KF/KR and understeering. It is possible to weaken the characteristics. 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 adjust the spring constant of the front wheel.
Understeer characteristics are strengthened by increasing KF, decreasing the spring constant KR on the rear wheel side, and increasing KF/KR. 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 spring constant control by the steering angle sensor 5, This enables control according to vehicle speed. This vehicle speed-based control means, for example, as is conventionally known, vehicle speed V
control in the opposite direction, and control that weakens the 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 ( Two types of control can be considered to weaken the understeer characteristics depending on the magnitude of θ×V ² ). 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 control in the opposite direction for the steering angle and vehicle speed is shown in the embodiment shown in Fig. 5 by θ×V ²
The control for this will be explained with reference to the embodiment shown in FIG. ) In addition to the automatic automatic control described above, the automatic manual changeover switch 7 also enables manual control when it is desired to manually change the spring constants KF and KR of the front and rear wheels. . 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 , which is then input to the multiplier 33 to obtain θ×V ² , and this output θ×V ² to buffer 34a and amplifier 34
The spring constant is transmitted to the actuators 1a and 2b of the front and rear wheels via the spring 2b to control the spring constant. In other words, the ratio of the spring constant to the front and rear wheels depends on the magnitude of the product of the vehicle speed V squared and the steering angle θ.
The magnitude of KF/KR is controlled so that the larger this value (θ×V ² ) is, the smaller it becomes. This makes it possible to perform spring constant 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 spring constants of the front and rear wheels are controlled depending on the combination of vehicle speed and steering angle. This third embodiment performs basic control of reducing the magnitude of KF/KR during steering, while
Furthermore, the magnitude of KF/KR is changed depending on the vehicle speed. That is, KF/KR 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] In Table 2, "soft" means that the spring constants KF and KR are small, and "hard" means that they are large.
Therefore, Table 2 shows that when steering at both low and high speeds, the rear wheel spring constant KR is changed from soft to hard to weaken the understeer characteristics, and when the vehicle speed is from low to high both when driving straight and when steering. To become and,
The spring constant KF of the front wheels is changed 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. Actuator 1 of accumulator 1A of suspension 1 of the connected front wheel
a, 1a. (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 sent to the second comparator 38
and its output is input to the second transistor 39
is turned on and off to control the actuators 2a, 2a of the accumulator 2A of the rear wheel suspension 2 connected thereto. (During steering, the output of the second comparator 38 becomes H, turning on the actuator and making the software hard.) Next, a specific example of an air spring suspension with variable spring constant is shown in detail in Figure 6. explain. 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 the upper and lower cases 13 and 16.
a piston rod 18 coaxially penetrating the inside of the lower case 16 and slidable up and down with respect to the inner cylinder 15 of the lower case 16;
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 are provided. The oil chamber C between the outer cylinder 14 and the inner cylinder 15 is communicated with the upper end of the A chamber at the upper end, and with the lower end of the B chamber at the lower end. 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 rotation key 22 which is rotated by an external force so as to be able to transmit rotational force. The lower end of the control rod 21 is provided with an orifice 21b that communicates with a communication hole 18b formed in the lower end 18a of the piston rod 18 so as to communicate chamber A and chamber B. Due to the rotation, this orifice 21b and the piston rod lower end 18a
Communication with the communication hole 18b is turned on and off. The 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 omitted. 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. Absorbed elastically. Lower case 16
Brackets 16b and 16c fixed to the outer surface of the vehicle are used to secure a wheel support structure including a wheel hub that rotatably supports the wheels, and thereby the wheels are held on the part 10 of the vehicle body so as to be movable up and down. Ru. That is, the vehicle body is suspended by wheels and elastically supported so as to be movable up and down. A part of the peripheral wall of this air chamber 12 has an opening 12a.
is provided, and one end of a pneumatic pipe 23 for communicating the accumulator 2A and the air chamber 12 is connected to this opening 12a. This pneumatic piping 2
The other end of 3 is connected to a solenoid valve (the actuator) 2a of the accumulator 2A, and this solenoid valve 2a is electrically connected to a lead wire 3c from the controller 3. This solenoid valve 2a is closed by the output from the controller 3 as described above, and separates the air chamber 12 from the air chamber of the accumulator 2A.
Increase the spring constant KR of the air spring. That is, if this air spring is for the suspension 2 for the rear wheels, the solenoid valve 2a of the accumulator 2A is closed by the output from the controller 3 during steering, the volume of the air chamber 12 is reduced, and the air spring is The spring constant becomes larger. As the spring constant increases, the soft air spring becomes hard, and the spring constant KR of the rear wheel increases, as shown in Table 2.
As is clear from this, the car's understeer characteristics are weakened and responsiveness increases. In the case of the front wheels, contrary to the above control, when a steering signal during steering is input to the controller 3,
The controller 3 acts to open the solenoid valve (actuator) 1a of the accumulator 1A, and reduces the spring constant KF of the air springs of the front wheel suspensions 1, 1 to make them soft. The suspension of an automobile according to the present invention uses a spring means with a variable spring constant as described above, and controls this according to changes in the steering angle to control the KF/KF during steering.
By reducing KR, the understeer characteristic, which is weakened when the vehicle is not being steered, can be maintained at the desired level, and stable driving can always be achieved regardless of changes in the steering angle.

[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. The circuit diagram shown in FIG. 6 is a sectional view showing an example of the spring means used in the suspension of the present invention. 1, 2...suspension, 1a, 2a...actuator, 1A, 2A...accumulator,
3... Controller, 5... Steering angle sensor, 6...
...Vehicle speed sensor, 7...Auto manual changeover switch, 12...Air chamber, 13...Upper case, 14
...Outer cylinder, 15...Inner cylinder, 16...Lower case, 1
8...Piston rod, 18b...Communication hole, 19
...Main valve, 20 ...Bottom valve, 21
...Control rod, 21b...Orifice, 22...Rotary key.

Claims (1)

[Claims] 1. A spring means with a variable spring constant provided in parallel with a damper on at least one of the front and rear wheel suspensions, an adjusting means for changing the spring constant of the spring means, detecting the steering operation, and detecting when the steering wheel is turned. a steering sensor that outputs a steering signal to the controller; and a controller that inputs a control signal to the adjusting means to reduce the ratio of the spring constant of the front wheel suspension to the spring constant of the rear wheel suspension when the steering signal is input. suspension.