JPH0474208B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automobile suspension control device that variably controls suspension characteristics depending on driving conditions.

(Prior art) The spring characteristics of the springs and the damping rate of the dampers that make up the suspension of an automobile, in other words, the suspension characteristics, significantly affect the ride comfort and body posture of the automobile. If it is soft, the ride quality is good, but the so-called roll phenomenon in which the outer side of the vehicle body sinks when turning becomes significant, resulting in unstable vehicle body posture.

For such problems, for example, Japanese Patent Application Laid-open No. 1983-
Publication No. 30818 discloses an invention related to a "vehicle anti-roll device." This operates the orifice control solenoid of the shock absorber according to the vehicle speed and steering angle to increase the damping rate of the shock absorber during turning. According to this, during normal driving, the suspension characteristics are set to be soft to provide good riding comfort, and during cornering, the suspension characteristics are set to be hard to prevent the vehicle body from rolling.

However, this invention increases the damping rate of the shock absorber only while detecting vehicle body roll based on vehicle speed and steering wheel angle, so the suspension characteristics become soft as soon as the steering wheel is turned after turning. Therefore, it is not possible to prevent the vehicle body from swinging back after the steering wheel is turned back.

In addition, the body posture of an automobile is greatly influenced by the spring characteristics of the springs and dampers that make up the suspension, and for this reason, when attempting to stabilize the vehicle body posture by suppressing roll etc. when turning. The setting of the spring characteristics described above is extremely important.

(Object of the Invention) Therefore, the present invention provides a suspension control device that variably controls the spring characteristics of the suspension.
During normal driving, the suspension characteristics are soft to ensure a good ride, while when the vehicle is in a turning state, the spring characteristics are hardened to stabilize the vehicle body posture, and this hard state is used to terminate the above-mentioned turning state. By holding the steering wheel for a predetermined period of time, it is possible to effectively prevent the steering wheel from swinging back when the steering wheel is turned back after turning.

Particularly, in the present invention, by making the hard state holding time after the turning state is longer at high speeds and shorter at low speeds than at high speeds, it is possible to reliably prevent a significant swing back after turning, especially at high speeds, and to This prevents deterioration of riding comfort caused by unnecessarily hardening the suspension characteristics for a long time.

(Structure of the Invention) A suspension control device for an automobile according to the present invention is configured as follows in order to achieve the above object.

That is, in a suspension control device that variably controls the spring characteristics of the suspension, there is a turning state detecting means for detecting the turning state of the vehicle, a vehicle speed detecting means for detecting the traveling speed of the vehicle, and a system that receives the outputs of these detecting means. , when the vehicle is in a turning state, the spring characteristics of the suspension are made hard, and this hard state is held for a predetermined time after the end of the turning state, and the time for which this hard state is held is longer at high speeds and longer at low speeds. It is also equipped with a control means that sometimes sets the speed shorter than when the speed is high. The turning state detecting means is, for example, a roll detecting means for detecting roll of the vehicle body, and in this case, the spring characteristics of the suspension are made hard from the start of rolling due to turning until a predetermined time has elapsed after the rolling stops. At the same time, the hard state retention time after the roll stops is longer at high speeds and shorter at low speeds than at high speeds.

(Example) The present invention will be described below based on an example shown in the drawings.

As shown in FIG. 1, front, rear, left and right wheels 1...1 are provided with suspensions 2...2 for suspending the vehicle body. Each of these suspensions 2...2 has a damper 3, a coil spring 4, and an air spring chamber 5, and the damper 3 is equipped with a step motor 6 that switches its damping rate in two stages, large and small. Further, the air spring chamber 5 is connected to the accumulator 8 via a pipe 7, and
A solenoid valve 9 is interposed between the air spring chamber 5 and the accumulator 8 to communicate and cut off the two, and the amount of air acting as a spring is increased or decreased by opening and closing the solenoid valve 9. The spring constant of the air spring can be switched to two levels, large and small.

On the other hand, a controller 10 is provided that sends drive signals A and B to the step motor 6 and the solenoid valve 9 in each suspension 2...2, and this controller 10 includes a steering wheel angle sensor that detects the steering angle of the steering wheel. 11 and a signal D from the vehicle speed sensor 12 that detects the running speed of the vehicle.
is now entered.

Here, the specific structure of the suspension 2 will be explained with reference to FIG. The lower end of the upper case 22 and the upper end of the lower case 24 are connected through a rolling diaphragm 25, and both cases 22, Seal member 26 is inside 24
The inside of the upper case 22 is a hermetically sealed air spring chamber 5. The air spring chamber 5 is connected to the accumulator 8 via the pipe 7 and the solenoid valve 9 as described above, and spring receiving members 27 and 28 are fixedly installed in the upper case 22 and the lower case 24, respectively. A coil spring 4 is attached.

Further, the lower case 24 is composed of an outer cylinder 29 and an inner cylinder 30, and a piston rod 31 hanging down from the upper case 22 is inserted into the inner cylinder 30 so as to be vertically slidable, and is provided at the lower end of the rod 31. The inside of the inner cylinder 30 is connected to the upper oil chamber 3 by the main valve 32.
3 and a lower oil chamber 34. Further, a bottom valve 35 is provided at the lower end of the inner cylinder 30, and a space between the inner cylinder 30 and the outer cylinder 29 is a reservoir chamber 36.

Further, the main valve 32 has an extension side orifice 38 configured to allow the working fluid to pass only from the upper oil chamber 33 to the lower oil chamber 34 side by means of a check valve 37, as shown in an enlarged view in FIG. , check valve 39
It has a contraction side orifice 40 which allows working fluid to pass only from the lower oil chamber 34 to the upper oil chamber 33 side, and also has an orifice valve 43 consisting of a sleeve 41 and a valve body 42.
This orifice valve 43 is connected to the step motor 6 shown in FIGS.
When the through hole 41a in the sleeve 41 and the through hole 42a in the valve body 42 coincide with each other as shown in the figure, the upper oil chamber 33 and the lower oil chamber 34
It is designed to communicate with This results in
Upper oil chamber 33, lower oil chamber 34 and main valve 3
2, the damper 3 configured by the step motor 6 achieves a high damping rate state in which both the chambers 33 and 34 are communicated only through the orifice 38 or 40, and in addition to these, the damper 3 is operated by the step motor 6.
3, it is also switched to a state with a small attenuation rate.

On the other hand, the controller 10 shown in FIG. 1 is configured as shown in FIG. 4. That is, the controller 10 receives the signal C from the steering wheel angle sensor 11.
a roll determination circuit 51 which outputs a roll signal E of "H" level when determining the roll of the vehicle during turning when inputted with the roll signal E, and a first timer circuit 52 and a second timer circuit 5 to which the roll signal E is inputted, respectively.
3, and a vehicle speed determination circuit 54 which receives the signal D from the vehicle speed sensor 12 and outputs a signal F at the "H" level when the vehicle is running at high speed. The first and second timer circuits 52 and 53 are circuits having an off-delay function, and as shown in FIG. G ₁ and G ₂ are output respectively, but when the input of signal E is stopped, the delay time T ₁ and T ₂ (T ₁
> T ₂ ), the output of the signals G ₁ and G ₂ is stopped.
The output signal G ₁ of the first timer circuit 52 and the output signal F of the vehicle speed determination circuit 54 are input to the first AND circuit 55, and the output signal G ₂ of the second timer circuit 53 and the output signal F of the vehicle speed determination circuit 54 are input to the first AND circuit 55. The signal F' obtained by inverting the output signal F by the inverter 56 is
It is input to the 2AND circuit 57, and the first and second
The output signals H and I of the 2AND circuits 55 and 57 are input to the amplifier circuit 59 via the OR circuit 58, and when either one of the signals H and I is at the "H" level, the output signals H and I from the amplifier circuit 59 are input to each of the steps. Drive signals A and B are output to the motor 6 and the solenoid valve 9.
Here, the drive signal A drives the step motor 6 to close the orifice valve 43 in the damper 3, and the drive signal B causes the solenoid valve 9 to close. Therefore, when these signals A and B are output, both the attenuation rate of the damper and the spring constant of the spring are increased, and the suspension characteristics of the suspension 2 become hard.

The roll determination circuit 51 is configured by, for example, a microcomputer as shown in FIG. That is, the signal C from the steering wheel angle sensor 11
It is composed of an arithmetic circuit 63 into which the signal is input via an amplifier 61 and an A-D converter 62, and a memory circuit 64 connected to the arithmetic circuit 63. Then, according to the flowchart in FIG. 7, the arithmetic circuit 63 first reads the current steering wheel angle θ using the signal C (step S ₁ ), and then reads the current steering wheel angle θ using the signal C.
The current weighted average value θ ₀ is determined based on the weighted average value θ ₀ ' of the steering wheel angles up to the previous time determined by the previous calculation stored in the storage device 64 (step S ₂ ). After that, this average value θ ₀ is compared with the steering wheel angle θ read this time, and when the difference - θ - θ ₀ - exceeds a certain value R, a roll signal E is sent to the first and second timer circuits 52 and 53. Output (step
_S3 , _S4 ). Here, in the example of Fig. 7, the average value θ ₀ ' up to the previous time and the current reading handle angle θ
When calculating the current average value θ ₀ from , both θ ₀ ′,
A constant K greater than 1 to make the weight of θ different
is used.

Next, the operation of the above embodiment will be explained.

First, during normal straight-ahead running, the controller 10 does not output drive signals A and B that harden the suspension characteristics to the step motors 6 and electromagnetic valves 9 of each suspension 2...2. Therefore, in each suspension 2, damper 3
As shown in FIG. 3, the orifice valve 43 communicates the upper oil chamber 33 and the lower oil chamber 34, and also communicates the air spring chamber 5 and the accumulator 8, so that both the damper and the spring are connected to each other. It is considered to be in a soft state. On the other hand, when the steering wheel is turned in order to turn the automobile, in the roll determination circuit 51 of the controller 10 to which the signal C is input from the steering wheel angle sensor 11, the arithmetic circuit 63 operates according to the flowchart shown in FIG. In operation, first, the weighted average value θ ₀ of the steering wheel angle is calculated.
This average value θ ₀ changes smoothly and with a delay with respect to changes in the steering wheel angle θ, as shown in FIG. 5a.
When the difference between the steering wheel angle θ at that time and the average value θ ₀ up to that point exceeds a certain value R, that is, the steering wheel angle θ exceeds the average value θ ₀ plus the constant value R. When operated, in other words, when the roll of the vehicle body is determined, a roll signal E is output from the arithmetic circuit 63 (roll determination circuit 51) to the first and second timer circuits 52, 53. The first and second timer circuits 52 and 53 are the first and second AND
Signals G _{1 and 1} are applied to one gate of the circuits 55 and 57, respectively.
Output G ₂ . At this time, the first and second AND circuits 5
The other gates 5 and 57 are input with the signal F that is at the "H" level at high speeds and the signal F' that is at the "H" level at low speeds from the vehicle speed determination circuit 54, respectively. The 1AND circuit 55 outputs a signal H that is the same as the output signal G ₁ of the first timer circuit 52, and at low speed, the second AND circuit 57 outputs a signal I that is the same as the output signal G ₂ of the second timer circuit 53.
will be output. In that case, the output signals G ₁ and G ₂ of the first and second timer circuits 52 and 53 rise simultaneously with the ON of the input signal E, as shown in FIGS. 5b to 5d. output signal of
G ₁ is the output signal of the second timer circuit 53 after the relatively long time T ₁ has passed after the input signal E is turned off.
G ₂ is turned off after a relatively short time T ₂ has elapsed. As a result, at high speeds, the amplification circuit 59 sends information to the step motor 6 and the solenoid valve 9 based on the output signal H of the first AND circuit 55 from when the roll is determined until a relatively long time T ₁ has passed after the end of the determination. Drive signals A and B are output, and the first drive signal is output at low speeds.
Based on the output signal I of the 2AND circuit 57, the drive signals A and B are outputted from when the roll is determined until a relatively short time _T2 has elapsed after the end of the determination.

In this way, the orifice valve 43 of the damper 3 in each suspension 2...2 is closed at the same time as the roll determination during turning, both at high speed and at low speed, and the air spring chamber 5 and accumulator 8 are closed. The suspension characteristic is made hard by being cut off, and even after the roll determination is completed, the hard state is maintained for a set time T ₁ or T ₂ corresponding to the vehicle speed, thereby preventing swinging back after the roll is stopped. . In that case, at high speed, the above hard state retention time
Since T ₁ is long, hunting is reliably prevented, especially at high speeds without significant shaking back, and at low speeds, the hard state holding time T ₂ is short, so the time required to sacrifice ride comfort to prevent shaking back is minimized. It is said to be a limited time. In particular, since the spring characteristics of the air springs that greatly influence the vehicle body posture are set to be hard, vehicle body roll during turning is more effectively suppressed and the vehicle body posture is stabilized.

In this embodiment, the roll determination circuit 51 of the controller 10 determines roll when the difference between the steering wheel angle θ and the average value θ ₀ of the steering wheel angle up to the point in time exceeds a certain value R. Therefore, the roll signal E is not outputted in a complicated manner due to rotation of the steering wheel with a degree of play, and the above-mentioned signal is not outputted when the steering wheel angle θ is maintained at a constant angle and enters a steady turning state. The output of E is stopped. In other words, the roll signal E is output only when the steering wheel angle changes sharply above a certain level and the vehicle body is actually rolling, and the roll signal E is output for a predetermined period of time T ₁ or T during the output of the signal E and after the output is stopped. ₂ , the suspension is set to hard, and when the above-mentioned time _T1 or _T2 elapses after transitioning to a steady turning state, the suspension is returned to soft again. Then, as shown in Fig. 5, when returning from a steady turning state to a straight-ahead running state, when the steering wheel angle changes sharply more than a certain level again, a roll signal E is output again, and during the output and after the output is stopped. The suspension becomes hard again for a predetermined time _T1 or _T2 .

In addition to the calculation formula shown in the flowchart of Fig. 7, the calculation formula for calculating the average value θ ₀ of the steering wheel angle θ is the simple average value of N values of the steering wheel angle θ _o from the start of control to the relevant point in time. , that is, θ ₀ =( _N 〓 ⁿ⁼¹ θ _o )/N,
Alternatively, among the N values of the steering wheel angle θ _o from the start of control to the relevant time point, the average value of M values immediately before the relevant time point, that is, θ ₀ =( _N 〓 ^n=N-M+1 θ _o )/M, etc. may also be used.

Further, the roll determination circuit for determining the roll during turning in the controller 10 may be configured by an analog circuit 51' as shown in FIG.
That is, the current steering angle θ indicated by the signal C from the steering wheel angle sensor 11 is transmitted to the differential amplifier 7 via the amplifier 71.
2, one is input directly and the other is input as an average value θ ₀ as _shown in FIG. Then, this difference is input to a comparator 74 and compared with a constant voltage R, and when the difference (θ-θ ₀ ) is larger than R, the roll signal E is output. Even with such a configuration, the same effect as in the above embodiment can be obtained.

In the above embodiments, the suspension characteristics are controlled for both the air spring and the damper, but it may also be possible to control only the air spring, which has a large effect on stabilizing the vehicle body posture. It is also possible to control only the suspension of the outer wheels. Furthermore, the hard state holding time may be changed in three or more steps or steplessly depending on the vehicle speed.

(Effects of the Invention) As described above, according to the present invention, among the dampers and springs that make up the suspension in a turning state, the springs that have a large effect on stabilizing the vehicle body posture by suppressing the displacement of the vehicle body are particularly effective. In addition to making the spring characteristics hard, this hard state is maintained for a predetermined period of time even after the end of the turning state, and this hard state is held for a longer time at high speeds and shorter at low speeds than at high speeds. Rolling and shaking of the vehicle body caused by turning are reliably prevented at high speeds, where they become especially noticeable, and at low speeds, without unnecessarily sacrificing ride comfort, and the posture of the vehicle body is stabilized.

The above-mentioned embodiment is an example in which the suspension characteristics are once returned to soft when transitioning to a steady turning state, but this steady turning state is also determined to be a roll state, and when returning to a straight running state, A hard state retention time may be provided to return to the software state.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a control system diagram, FIG. 2 is a vertical sectional view showing the specific structure of the suspension, FIG. 3 is an enlarged view of the main parts, and FIG. A block diagram showing the configuration of the controller, Fig. 5 is a time chart showing the operation, and Fig. 6 is a block diagram showing the configuration of the controller.
The figure is a block diagram showing one specific example of the roll judgment circuit in the controller, FIG. 7 is a flowchart showing the operation of the judgment circuit, and FIG. 8 is a circuit diagram showing another specific example of the roll judgment circuit. . 2... Suspension, 3... Damper, 5...
Air spring chamber, 7... Pipe, 8... Accumulator, 9... Solenoid valve, 10... Control means (controller), 11, 51, 51'... Turning state detection means (11... Handle angle sensor, 51, 51'...roll determination circuit), 12...vehicle speed detection means (vehicle speed sensor).

Claims (1)

[Scope of Claims] 1. A suspension control device that variably controls the spring characteristics of a suspension, which comprises: turning state detection means for detecting the turning state of a vehicle; vehicle speed detection means for detecting the running speed of the vehicle; receiving the output of the detection means, hardens the spring characteristics of the suspension when the vehicle is in a turning state, maintains this hard state for a predetermined time after the end of the turning state, and maintains this hard state; A suspension control device for an automobile, comprising control means for setting a longer time at high speeds and shorter time at low speeds than at high speeds. 2. The automobile suspension control device according to claim 1, wherein the turning state detection means is a roll detection means for detecting roll of the vehicle body.