JPS6210845B2 - - 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 Publication No. 109008/1983, a vehicle is known in which the damping force is changed according to 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, changes in load are also closely related to handling characteristics, and changes in load affect handling characteristics. In other words, the understeer characteristics become weaker when the load is high and become stronger when the load is low. Therefore, sufficient running stability cannot be ensured only by control according to vehicle speed. For example, when the number of passengers in a car increases or the load on the car increases, the understeer characteristics become weaker and the car becomes more prone to oversteer. Understeer characteristics are particularly effective in correcting when a car is subjected to external disturbances.
When this characteristic weakens, straight-line stability deteriorates, making the car dangerous, especially at high speeds. However, if the understeer characteristic becomes too strong, the responsiveness during steering becomes slow and the maneuverability deteriorates, so it is not desirable to simply strengthen the understeer characteristic. Therefore, it is desirable to always be able to obtain appropriate understeer characteristics when the load changes. On the other hand, when trying to obtain good handling characteristics by changing the damping force of the damper as described above, the following problems arise. The damping force of the damper is generated in response to the vertical movement of the vehicle body relative to the wheels, and the magnitude of this damping force is proportional to the speed of the vertical movement of the vehicle body. For this reason, for example, when the vehicle rolls when driving around a curve, the damper's damping force is obtained at the initial stage of entering the curved road where the vehicle height changes according to the roll, but in the steady roll state in the middle of the curve. Since the vehicle body is held in a constant roll, the vehicle height does not change, making it impossible to obtain the damping force of the damper. In other words, if you try to change the steering characteristics by adjusting the damper's damping force, you can obtain the desired steering characteristics at the initial stage of entering the curve, but in the middle of the curve when the steady roll state occurs, the damper's damping force will change. Therefore, there is a problem that the steering characteristic cannot be controlled to a desired value. The present invention has focused on this point, and an object of the present invention is to provide an automobile suspension that can always obtain desirable handling characteristics in response to changes in load. 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 load to always obtain desired steering characteristics. It is characterized by: 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 signal is input from a load sensor that detects the vehicle body load and outputs a signal when the load is high, this adjustment means is controlled by
That is, the controller is configured to input a control signal to the adjusting means so as to make the ratio of the spring constant of the front wheel suspension to the spring constant of the rear wheel suspension larger when the load is high than when the load is low. Here, making the ratio of the spring constant of the front wheel suspension to the spring constant of the rear wheel suspension larger at high loads than at low loads means that when the front wheel side spring constant is constant, the rear wheel suspension spring constants at high loads. There are three cases: reducing the constant, conversely, keeping the rear wheel constant and increasing the front wheel, and changing both in the opposite direction, that is, increasing the front wheel and decreasing the rear wheel ( In each case, the spring constant is changed in the opposite direction to the above at low loads. 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 mean that KF/KR at high loads is made smaller than KF/KR at low loads. This can be expressed as shown in Table 1.

[Table] Increasing KF/KR strengthens the understeer characteristics, so it is possible to prevent the understeer characteristics from being weakened by high loads. Since the present invention changes KF/KR depending on the magnitude of the vehicle body load as described above, it is possible to always obtain desirable understeer characteristics and to achieve good maneuverability and running stability. Furthermore, in the present invention, since the steering characteristics are controlled by changing the spring constant of the spring means, even when driving on a curve, the steering characteristics are always controlled favorably by receiving the spring force generated by the roll of the vehicle body. can be done. 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 output from the load sensor 4 that detects the magnitude of the vehicle body load is input to the controller 3 through a lead wire 3a, and the output is sent to the accumulators 1A and 2A of the front and rear wheel suspensions 1, 1; 2, 2 for changing the spring constant. Control signals are sent through lines 3b and 3c. Further, in this embodiment, a manual changeover switch 5 for switching the stiffness of the entire suspension between hard and soft is connected to the controller 3 through a lead wire 3d. As shown in Figure 2, each suspension 1,
1; 2, 2 is an accumulator 1 equipped with actuators 1a, 2a consisting of solenoid valves;
A, 2A are connected, and by communicating the air chambers in the accumulators 1A, 2A with the air chambers in the air springs of each suspension 1, 1; 2, 2 through this solenoid valve, the spring constant of the air spring is
KF and KR are starting to change. The output from the controller 3 that receives the signal from the load sensor 4 is inputted to the actuators 1a, 2a of the accumulators 1A, 2A of the left and right front and rear wheel suspensions 1, 1; 2, 2 through lead wires 3b, 3c. . The actuators 1a, 2a receiving this output, that is, a signal indicating high load, act on the air springs 1b, 1
b: Control the spring constants of 2b and 2b to be small or large. Specifically, when a high-level signal is input to the actuators 1a, 2a and the solenoids are driven, the air chambers of the accumulators 1A, 2A are communicated with the air chambers of the air springs of each suspension, and the spring constant is small. and the suspension becomes soft. Conversely, when the signal is low, the solenoid is demagnetized, the solenoid valve is closed, and the spring constant of the suspension becomes larger and harder. This is shown in a table as follows.

[Table] For example, if the load sensor 4 detects a load equal to or higher than a predetermined value and outputs a signal (voltage equal to or higher than the predetermined value) indicating a high load, the controller 3 receives this signal and activates the actuators 1a, 2a. is driven to increase the spring constant (KF) of the front wheel air springs 1b, 1b and decrease the spring constant (KR) of the rear wheel air springs 2b, 2b, thereby increasing KF/KR. Specifically, as shown in FIG. 3, for example, when the output of the load sensor 4 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 former transistor 3D is increased to turn on this transistor 3D, and the solenoid of the front wheel actuator 1a connected to the collector side of the former transistor 3C is demagnetized, thereby suspending the front wheel. By increasing the spring constant (KF) of the transistors 1 and 1, and driving the solenoid of the actuator 2a on the rear wheel side connected to the collector side of the latter transistor 3D,
It is possible to reduce the spring constant (KR) of the suspensions 2, 2 on the rear wheel side, thereby increasing KF/KR and strengthening the understeer characteristics. In a low load state, the output of the load sensor 4 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 change the spring constant of the front wheel ( Understeer characteristics are weakened by decreasing KF/KR by decreasing KF) and increasing the spring constant (KR) on the rear wheel side. In addition to the above-mentioned automatic automatic control, the automatic manual changeover switch 5 enables manual control when it is desired to manually change the spring constants (KF, KR) of the front and rear wheels as a whole. It is something to do. Next, a second embodiment will be explained with reference to FIG. In this embodiment, in addition to the load sensor 4, a manual changeover switch 5 is used. This changeover switch 5 allows the driver to change the spring constant of the entire front and rear wheel suspension between large and small, that is, change the elasticity of the suspension between hard and soft, according to his/her preference. The output of the load sensor 4 is input to the positive input of a comparator 31, and when the load is larger than a predetermined value (when the load is high), a signal indicating that the load is high is outputted from the comparator 31. That is, the output level of the comparator 31 becomes (H).
The output of this comparator 31 is the NOR circuit 32
and the non-inverting input of the OR circuit 33. On the other hand, the output of the manual changeover switch 5 is ORed with the other input of the NOR circuit 32.
Connected to the inverting input of circuit 33. NOR circuit 3
The output of 2 is sent to the transistor 34 that drives the actuator 1a of the accumulator 1A of the front wheel suspension 1, 1 in order to change the spring coefficient of the air spring of the front wheel suspension 1, 1.
The output of the circuit 33 is connected to a transistor 35 that drives the actuator 2a of the accumulator 2A of the rear wheel suspension 2,2. The signals and effects of the circuit shown in FIG. 4 will be explained with reference to Table 3.

[Table] First, the driver wants to make the entire suspension hard, so when he selects hard (large spring constant) with the manual changeover switch 5, the output of the switch 5 becomes (H), that is, “1”, and the NOR circuit 32 “1” is input to one input and the inverting input of the OR circuit 33. At this time, if the vehicle body load is high, the output of the load sensor 4 becomes an output (H), that is, "1", which is input to the other input of the NOR circuit 32 and the non-inverting input of the OR circuit 33.
Therefore, the output of the NOR circuit 32 becomes "0" and the output of the OR circuit 33 becomes "1". As a result, the transistor 34 on the front wheel side is turned off, the front wheel actuator 1a is demagnetized, and the spring constant (KF) becomes large (hard), while the transistor 35 on the rear wheel side is turned on, and the rear wheel actuator 2a is driven. Open the valve of accumulator 2A and reduce the spring constant (KR). (soft)
Therefore, the ratio of the spring constants of the front and rear wheels (KF/KR) increases, and the understeer characteristics are strengthened. Next, when the vehicle load decreases in the above state (hard selection), the output of the load sensor 4 becomes "0", so the output of the comparator 31 becomes "0",
The output of the OR circuit 33 becomes "0". Accordingly, the rear wheel actuator 2a is also demagnetized, the spring constant (KR) of the rear wheel suspension is also increased (hard), and the understeer characteristics are weakened to the standard state. Also, if the driver selects the soft suspension and sets the output of the changeover switch 5 to "0",
One input of the NOR circuit 32 becomes "0", and when the output from the comparator 31 is "1" with a high load, the output of the NOR circuit 32 is "0", and when it is "0" with a low load, it is set to "0". Set to “1”. On the other hand, at this time, since the inverting input of the OR circuit 33 is always set to "0", the output of the OR circuit 33 is always "1". Therefore, the actuator 2a of the rear wheel suspension is always driven and the spring constant (KR) is always small, and the spring constant (KF) of the front wheel suspension becomes large (hard) when the load is high, resulting in understeer characteristics. It becomes stronger and becomes smaller (softer) when the load is low, weakening the understeer characteristics. Next, a specific example of a variable spring constant air spring suspension in which the spring constant is reduced by driving the actuator as described above will be explained in detail with reference to FIG. (It is designated as suspension 2 for the rear wheels.) As shown in FIG.
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;
The piston rod 18 has 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 air 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. In addition, a control rod 21 passes through the center of the piston rod 18 vertically.
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. This control rod 21
An orifice 21b is provided at the lower end to communicate 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. Rotation of the control rod 21 causes the orifice to open. 21b and piston rod lower end 18
The communication between the hole 18a and 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 the solenoid valve 3 is connected to a solenoid valve (actuator) 2a of the accumulator 2A, and this solenoid valve 2a is electrically connected to a lead wire 3c from the controller 3. As described above, this solenoid valve 2a is opened and closed by the output from the controller 3 to communicate or separate the air chamber 12 and the air chamber of the accumulator 2A, thereby decreasing or increasing the spring constant (KR) of the air spring. The automobile suspension 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 vehicle body load, so that the spring means can be controlled in accordance with changes in the vehicle body load.
By increasing KF/KR, the understeer characteristic, which weakens under high loads, can be maintained at the desired strength, and stable driving performance can always be achieved regardless of changes in vehicle body load.

[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 and 4 are specific examples of the suspension of the present invention. The circuit diagram shown in FIG. 5 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, 4... Load sensor, 5... Manual changeover switch, 12... Air chamber, 13... Upper case, 1
4...Outer cylinder, 15...Inner cylinder, 16...Lower case, 18...
piston rod.

Claims (1)

[Claims] 1 Air spring means with a variable spring constant provided in parallel with a damper on at least one of the front and rear wheel suspensions, and controlling the communication/blocking between the air chamber of this air spring means and the air chamber of the accumulator, A solenoid valve that changes the spring constant of the means, a load sensor that detects the vehicle load and outputs a signal when the load is high, and when this signal is input, the spring constant of the front wheel suspension is changed to the spring constant of the rear wheel suspension. An automobile suspension comprising a controller that inputs a control signal for increasing the ratio to the adjusting means.