JPS63195012A - Control device for vehicle suspension - Google Patents

Abstract

PURPOSE:To decrease a pitching phenomenan during a high speed traveling by setting a spring constant of each spring constant variable spring mechanism so that a differential value between the front wheel side spring constant and the rear wheel spring constant takes a positive value when a vehicle speed exceeds a given value. CONSTITUTION:A vehicle suspension is enveloped elastically in the up and down directions by an elastic body in which the inner part is made to be an air chamber between a body side member and a shock absorber. And a spring constant variable spring mechanism A, which can change a spring constant to at least two stages of high and low by adjusting pressure in the air chamber of the elastic body, is provided to at least either side of the front or rear wheel side. In this case, a vehicle speed judging means C is provided, in which a vehicle speed detected by a vehicle speed detecting means B is judged whether the speed exceeds a given value or not. And the spring constant of the variable spring mechanism A is made to be set so that a differentiation value between a front and rear wheel side spring constants takes a positive value by a spring constant setting means D when YES is judged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for a vehicle suspension,
In particular, for vehicle suspensions that are equipped with at least each front wheel or rear wheel a variable spring constant spring mechanism that can change the spring constant in at least two levels, high and low, the spring constant of the variable spring constant spring mechanism is controlled according to the vehicle speed. The present invention relates to a control device for a vehicle suspension.

[Conventional technology]

As a conventional vehicle suspension control device, for example, ITSUBIS old new model car manual GALANTE
The one disclosed in TERNAΣJ, August 1983, published by Mitsubishi Motors Corporation, No. 1), pages 1 to 137, is known.

In this conventional example, the spring constant and damping force are configured to be changeable in two stages, soft side and hard side, by the same actuator, and both can be changed to the soft side or hard side at the same time. be. For example, when the vehicle speed reaches a predetermined value or higher as detected by the vehicle speed sensor, the spring constant and damping force are simultaneously changed to the hard side to suppress sprung vibrations of the vehicle.

[Problem that the invention seeks to solve]

However, in the above conventional example, although the spring constant and damping force are both maintained on the soft side at low vehicle speeds, at least the spring constant is controlled to be switched according to the vehicle speed. No consideration was given to the balance of spring constants. Therefore, if the spring constant of the front wheel suspension (hereinafter referred to as the front wheel spring constant) is higher than the spring constant of the rear wheel suspension (hereinafter referred to as the rear wheel spring constant), this will occur frequently when driving at low speeds. This reduces the amount of dive during sudden braking and causes less change in the vehicle body, but there is a problem in that the pitching phenomenon increases due to input from undulating roads when driving at high speeds, which significantly impairs the stability of the vehicle. On the other hand, if the front wheel spring constant is lower than the rear wheel spring constant, pitching during high-speed running is reduced, but there is a problem in that dive during low-speed running becomes large.

Therefore, this invention was made by focusing on the problems of the prior art, and when the vehicle speed exceeds a predetermined value,
The difference between the front wheel spring constant kF and the rear wheel spring constant kR is -
The spring constant of each variable spring constant spring mechanism is set so that kF takes a positive value, thereby reducing the pitching phenomenon in high-speed driving conditions where the vehicle speed exceeds a predetermined value, and improving driving stability and ride comfort. The purpose is to

[Means for solving problems]

In order to achieve the above object, as shown in the basic configuration diagram of FIG. In a vehicle suspension provided on one side, a vehicle speed detecting means for detecting the vehicle speed, a vehicle speed determining means for determining whether the vehicle speed according to the vehicle speed detecting means exceeds a predetermined value, and a vehicle speed determining means for determining whether the vehicle speed exceeds a predetermined value by the vehicle speed determining means. Spring constant setting for setting the spring constant of the variable spring constant spring mechanism so that -kF takes a positive value in the difference value between the front wheel spring constant kF and the rear wheel spring constant kF when it is determined that the spring constant exceeds the value. It is characterized by being equipped with means. .

[Effect]

In this invention, the vehicle speed is detected by the vehicle speed detection means, and the vehicle speed determination means determines whether the vehicle speed is in a high-speed running state exceeding a predetermined value.

When the vehicle speed determination means determines that the vehicle is in a high-speed driving state, the spring constant setting means sets the difference value kl-kF between the front wheel spring constant kF and the rear wheel spring constant 8 to take a positive value. A spring constant of a variable spring constant spring mechanism provided on at least one of the front wheel side and the rear wheel side is set.

Therefore, the phase difference between the relative stroke of the front wheels and the relative stroke of the rear wheels in a high-speed running state becomes small, thereby making it possible to suppress the pitching phenomenon.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 to 6 are diagrams showing an embodiment of the present invention.

In FIG. 2, 1 indicates a vehicle body side member forming a part of the vehicle body, 2 indicates a wheel (for example, a front left wheel), and 3 indicates a suspension arm as a wheel side member connected to the wheel 2. As shown in the figure, a suspension drive section 10, which forms part of the vehicle suspension, is interposed between the vehicle body side member 1 and the suspension arm 3.

In this embodiment, the suspension drive unit 10 includes a variable spring constant spring mechanism 1) that can vary the spring constant between the vehicle body side member 1 and the suspension arm 3, and a spring constant variable spring mechanism 1) between the vehicle body side member 1 and the suspension arm 3. The shock absorber 12 suppresses minute vibrations.

Here, the suspension drive unit IO is provided for each of the front and rear wheels, and performs vibration suppression, etc., separately for each wheel, and the spring constant is controlled to be switched by a command from a controller 20, which will be described later.

The variable spring constant spring mechanism 1) includes a vehicle body side member 1
and an auxiliary tank 16 having an auxiliary air chamber G with a fixed volume; The main air chamber F and the auxiliary air chamber G are connected by a pipe line 17 that connects the main air chamber F and the auxiliary air chamber G. The switching valve (electromagnetic switching valve) 18 is configured to switch the switch to either a communication state or a cutoff state. Therefore, the excitation coil of the switching valve 1B is energized by an excitation current from a controller 20, which will be described later.
When valve 8 is set to "open", the main air chamber F and auxiliary air chamber G are in communication, and the spring constant can be changed to the soft side.On the other hand, when valve 18 is de-energized and set to "closed", the rain By setting the air chamber F to the Gt-blocking state, the spring constant is determined only by the volume of the main air chamber F, and the spring constant can be changed to the hard side.

In this embodiment, the spring constant of each spring constant variable spring mechanism 1) on the front wheel side is k F when on the hard side.
When H+ is on the soft side, krL (kFL< krlI)
and each spring constant variable spring mechanism 1 on the rear wheel side.
) spring constant kR is kR□ on the hard side.

'it (k RL < k R1)) on the soft side
It is set to take k RL < k as a whole.
It is set so that FL<kRH<kFll.

Furthermore, in this embodiment, the shock absorber 12 includes:
A hydraulic type is used, and its damping force is set constant, and the spring constant variable spring mechanism 1) is constructed and arranged so as to speed up the damping of vibrations.

On the other hand, a vehicle speed sensor 22 for detecting vehicle speed, which forms part of the vehicle suspension, and the aforementioned controller 20 are provided at predetermined positions on the vehicle body.

In this embodiment, the vehicle speed sensor 22 uses an optical method to detect the rotation speed of the output shaft of the transmission, and sends a vehicle speed signal DV, which is a pulse signal with a period corresponding to this, to the controller 2.
It is designed to output to .

In addition, as shown in FIG. 2, the controller 20 uses a control microcomputer 24 to set the excitation current ■ as a spring constant setting signal to each spring constant in accordance with a digital control signal SC from the microcomputer 24. The driving circuit 26F126R is configured to provide output to the switching valve 18 of the variable spring mechanism 1).

Among these, the drive circuit 26F sets the spring constant kR for the front wheels (first front right wheel), and the drive circuit 26R sets the spring constant kR for the rear wheels (rear left, rear right wheels). They are each inserted so that

Each of the drive circuits 26F and 26R does not output the excitation current I when the input control Shingo SC is at the logic L (low) level, and outputs the excitation current I of a predetermined value when it is at the logic H (high) level. It has become.

Of these, the microcomputer 24 includes at least an interface circuit 28, an arithmetic processing bag W30, a RAM, an R
The interface circuit 28 is composed of an I10 board and the like.

The arithmetic processing device 30 also includes an interface circuit 28
The above-mentioned vehicle speed signal DV is read through the vehicle speed signal DV, and the corresponding vehicle speed V is calculated, and based on this data, calculations and other processing described later are performed. Furthermore, storage device 3
2 stores in advance predetermined programs, fixed data, storage tables, etc. necessary for the execution of the arithmetic processing device 30, and is also capable of sequentially storing processing results of the arithmetic processing device 30. Here, the arithmetic processing unit 30 outputs the control signal SC at the logic H level when the spring constant command values SF and SR stored in the storage device 32 are at the logic value "1" according to a predetermined program, S,,SR
When the logic value is "0", the control signal S of logic L level
It is designed to output C.

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

When the ignition switch (not shown) of the vehicle is turned on, control by this device is started. That is, detection by the vehicle speed sensor 20 is started, and this detection signal DV is supplied to the controller 20. Then, the arithmetic processing unit 30 in the microcomputer 24 of the controller 20 executes the main program shown in FIG. 3, which has been stored in a predetermined area of the storage device 32 in advance.

First, in step (3) in FIG. 3, the arithmetic processing device 30:
Set the initial value of memory data. This initial value setting clears the vehicle speed value V in the vehicle speed/value storage area of the storage device 32, and also clears the front wheel spring constant command value SF in the front wheel spring constant storage area and the rear wheel spring constant command value SF in the rear wheel spring constant storage area. This is done by setting a logical value rOJ to the spring constant command value SR.

Next, in step (2), the arithmetic processing device 30 reads the input vehicle speed signal DV for a certain period of time, calculates the number of pulses per unit time or pulse interval, calculates the vehicle speed (2), and stores this in a predetermined area of the storage device 32. Updated and memorized.

Next, the process moves to step (2), and it is determined whether the vehicle speed (2) calculated in step (2) is equal to or greater than a preset upper limit vehicle speed reference value (2) r1 (see FIG. 4, for example, 50 km/h). This determination is to determine whether or not the vehicle is in a predetermined high-speed running state, and if V<Vr, it is determined that the vehicle is not yet in the predetermined high-speed running state and the process proceeds to step (2).

In this step (2), the arithmetic processing unit 30 calculates the currently set front and rear wheel spring constant command values SF and SR.
Since both have the logic value "0", the control signal SC at the logic L level is sent to the drive circuit 2 via the interface circuit 28.
Output to 6F and 26H. As a result, the drive circuit 26
F and 26R do not supply the excitation current I to each of the switching valves 18 of the variable spring constant spring mechanism 1) corresponding to the four wheels. As a result, each switching valve 18 becomes "closed," and the main air chamber F and the auxiliary air chamber G are cut off.
The spring constant is determined by the volume of the main air chamber F. Therefore, each spring constant has a higher hard side value)
CFH% kRH (krH>kR)), and suspension control is performed based on this.

Next, the processes of steps (2) to (2) are repeated again, and in step (2), the process waits until V≧Vrl. If ■≧Vrl is established in step ■, it is determined that the vehicle is in a predetermined high-speed running state, and the process then proceeds to step ■.

In this step (2), the arithmetic processing unit 30 applies logic to the front wheel spring constant command value SF stored in the front wheel spring constant area of the storage device 32 in order to set only the front wheel spring constant to a low soft side. Set the value rlJ and step ■
to move to.

In this step (2), the arithmetic processing unit 30 outputs a logic H level control signal SC to the drive circuit 26F via the interface circuit 28, and outputs a logic L level control signal SC to the drive circuit 26R.
A level control signal SC is output.

Thereby, the drive circuit 26F supplies a predetermined value of excitation current to each of the switching valves 18 of the front left and front right variable spring constant spring mechanisms 1). As a result, each switching valve 8 becomes "open", and the main air chamber F and the auxiliary air chamber G
are in communication, and each spring constant kF is determined by the sum of the volumes of the main air chamber F and the auxiliary air chamber G, so the spring constant kFL on the soft side is lower by the increase in volume. . In this state, L<k, and thus suspension control is performed.

Next, the process proceeds to step (2), where the current vehicle speed signal DV is read in the same manner as in step (2) described above, a vehicle speed V corresponding to this is calculated, and this is updated and stored.

Next, the process proceeds to step (2), and in order to determine whether or not the vehicle speed V has returned to the predetermined low-speed driving state from the high-speed driving state where the vehicle speed V once reached the above-mentioned upper limit vehicle speed reference value V, 1, the calculation in step (2) is performed. Lower limit vehicle speed reference value V that presets vehicle speed V
rll (However, v, , <V, , :V, g is, for example, 40
km/h). Here, the reason why the hysteresis characteristic (see Fig. 4) is provided as VrZ<V□ is to prevent the chuckling phenomenon in which the switching valve 18 repeats opening and closing operations when the vehicle speed V changes vibrationally near the reference value. This is to do so.

Then, in step ■ above, ■〉■,,! In this case, it is assumed that the vehicle speed V has not yet returned to the low-speed driving state of V,,2 or less, and the process proceeds to step ■, where the control signal S
Outputs C. As a result, the front wheel spring constant kF is maintained at the lower value kFL, and the rear wheel spring constant kR is maintained at the higher value kpu. Next, the processes of steps (2) to (2) are repeated, and in step (2), the process waits until V≦V'r2.

On the other hand, when it is determined in step (2) that ■≦■r2, it is assumed that the vehicle has returned to the predetermined low-speed running state, and the process then proceeds to step [phase].

In this step [phase], the arithmetic processing unit 30 uses the storage device 32 to return the front wheel spring constant to a predetermined high value.
The logical value rOJ is set to the front wheel spring constant command value S, and the process moves to step (2).

In this step (2), the control signal SC is outputted again in the same manner as in the step (2) described above, based on the logical value "0" of the front wheel spring constant command value S and the rear wheel spring constant command value SR. Therefore, the drive circuit 26F again stops supplying the excitation current I to the switching valve 18 of the variable spring constant spring mechanism 1) on the front wheel side. This gives each spring constant 2
and 8 are both determined by the volume of the main air chamber F only, so the higher values kFH and kRH (k□
<kFH).

Next, the process moves to step (2) and the above-described process is repeated until the power is turned off.

Next, the effect will be explained according to the driving situation of the vehicle.

Assume that the ignition switch of the vehicle is now off and the vehicle is stopped. In this state, although the controller 20 is powered off, the drive circuits 26F and 26
Naturally, the excitation current (2) from R is not supplied, and the switching valve I8 of each variable spring constant spring mechanism 1) is "closed". Therefore, as mentioned above, the front wheel spring constant and the rear wheel spring constant kR are set to the higher value, □ and kRH (kr
u>kRH). In this state, changes in the posture of the vehicle body are sufficiently suppressed, and shaking of the vehicle body that occurs in response to changes in load due to people getting on and off the vehicle, etc. is prevented.

When the ignition switch is turned on from this state, the power to the controller 20 is turned on and the above-described processing is performed. At this time, since the spring constant command values SF and SR are initially set to the logical value "0", each of the spring constants kr and kR of the variable spring constant spring mechanism 1) is , as described above, are both set to high values kyg and kuM (k□>kRll), thereby preventing the vehicle body from shaking due to fluctuations in the load acting on the vehicle.

Then, when the engine is started from this power-on state and the vehicle enters a running state, the corresponding vehicle speed V is detected as described above. In a low-speed running state in which the vehicle speed V is less than the upper limit vehicle speed reference value Vr1, the processes of steps ■ to ■ in FIG. 3 described above are repeated and the process does not proceed to step ■. The control signal SC is maintained at a logic L level, and the front wheel spring constant and rear wheel spring constant kR are adjusted to kFH and k as described above.
R) l(kpn>kg□). Therefore, in this low vehicle speed state, control is performed with priority given to suppressing nose dive and scut due to sudden braking and sudden start.

Furthermore, when the vehicle speed is accelerated from this state and reaches or exceeds the upper limit vehicle speed reference value Vrl, the third
The processes in steps ■ and ■ in the figure are executed. This results in
As mentioned above, for the front wheel spring constant, only the lower value kF
L is immediately switched to L, and eventually the spring constant is kr (
=krt)<kr (=to*ll). Therefore,
In a high-speed driving state with an upper limit vehicle speed reference value V, , 1 or more, the front wheel spring constant is lowered by the rear wheel spring constant kR to make it softer, and the pitching phenomenon that accompanies driving on a undulating road is preferentially suppressed.

The reason for suppressing the pitching phenomenon during high-speed running will be explained with reference to FIGS. 5 and 6.

FIG. 5 shows the relative stroke of the front and rear wheels over time during free vibration after passing through a undulating road.

In the figure, for the relative stroke vibration of the front wheel, its angular frequency ω, = (k, /m,)'', and for the relative stroke vibration of the rear wheel, its angular frequency ωR = (kr
/m*)"". Kokote and mf are the front wheel loads, and ° and m are the rear wheel loads.

The relative stroke of the rear wheels changes later than the relative stroke of the front wheels, and the pitch angle φ is expressed as the difference between the front wheel stroke and the rear wheel stroke, so the pitch angle φ
becomes smaller as the phase difference between the curve of angular frequency ω and the angular frequency ω becomes smaller.

For example, ■ in FIG. 5 indicates a case where the spring constant is >k, and ■ in the figure indicates a case where the spring constant is lower than in the case of ■. Therefore, as the front wheel spring constant is lowered, the resonance frequency becomes smaller, its period becomes larger, and the phase between the relative strokes of the front and rear wheels becomes smaller. Therefore, pitching is suppressed.

FIG. 6 shows an example of a change in the pitch angle φ when passing through a undulating road as shown in FIG. 6 (1). ■ in (2) of the same figure
is the front wheel spring constant, > the rear wheel spring constant is 8, and ■
hani, -kR, and ■ hani, <kR. According to this, as described above, pitching is suppressed as the front wheel spring constant kF decreases. In addition, the same figure (1
), CF is the damping constant of the front wheel shock absorber,
CR is the damping constant of the shock absorber on the rear wheel side.

By the way, when the vehicle is decelerated from the above-mentioned high-speed running state, the processes of steps ① to ① in Fig. 3 are repeated until the vehicle speed V falls below the lower limit vehicle speed reference value v2, so the spring constant is
The aforementioned kF<kR is maintained, and the pitching phenomenon is suppressed. Then, when the vehicle speed V further decreases and falls below the lower limit vehicle speed reference value v2, step 0 is performed as described above.
．． ■, kr (= kro) > kg (=
kio). As a result, nose dive and scut caused by sudden braking and sudden starts, which often occur when driving at low speeds, are controlled to be more effectively reduced.

On the other hand, in this embodiment, the above-described control is performed by keeping the rear wheel spring constant kR constant and decreasing the front wheel spring constant in a predetermined high-speed running state, so the sum of the spring constants in the high-speed running state is used. r kv (= ILr
t)+, +(=k-)J can be lowered as a whole, which can contribute to improving ride comfort during high-speed driving.

Here, a vehicle speed detection means is formed by the vehicle speed sensor 22 and the processing of steps (2) and (3) in FIG.
, (2) form a vehicle speed determination means, and the steps (2) to (2), (2) to (2) and the drive circuits 26F and 26R form a spring constant setting means.

In the above-mentioned embodiment, in a predetermined high-speed running state, the rear wheel spring constant kR is fixed and the front wheel spring constant k is fixed.
Although F was lowered to <kR, the present invention is not necessarily limited to this. For example, on the contrary, the front wheel spring constant may be fixed, and the rear wheel spring constant may be increased by I in a predetermined high-speed running state so that <k. In addition, it is possible to have multiple auxiliary air chambers with different volumes and switch the spring constant of the variable spring mechanism to three or more levels, or by adjusting the pressure of the air supplied to the main air chamber with a pressure regulating valve. , if the spring constant of the variable spring constant spring mechanism can be adjusted steplessly, the front and rear wheel spring constants k in a predetermined high-speed running condition
Both F and kR may be lowered (or raised) to make the front wheels relatively softer than the rear wheels.

Furthermore, in the above embodiment, both the front wheel side and the rear wheel side are equipped with a spring mechanism that can change the spring constant, but this can be installed only on one side as necessary, and the other side can be equipped with a spring mechanism that can change the spring constant. A configuration may also be adopted in which a spring mechanism with a fixed spring constant is provided.

Furthermore, in the embodiment described above, in addition to the spring constant control according to the vehicle speed, the lateral acceleration acting on the vehicle body may be detected and the roll suppression control may be performed in accordance with the detected lateral acceleration.

Furthermore, the values of the upper and lower vehicle speed reference values, the front wheel spring constants kFHs kFL, and the rear wheel spring constants kRH and kRL in the above embodiments may be determined arbitrarily as long as the above conditions are satisfied. However, if necessary, it may be set so that kiLskpt<kR□≦kFH.

Furthermore, in the above embodiments, the case where air is applied as the working fluid of the spring constant variable spring mechanism is explained, but the invention is not limited to this, and other gases or liquids such as oil and gas may be used in combination. It is also applicable to hydropneumatic suspensions.

Furthermore, in the embodiment described above, a case was explained in which a microcomputer was applied as a controller.
This can also be configured by combining electronic circuits such as comparison circuits and logic circuits.

〔Effect of the invention〕

As explained above, according to the present invention, when the vehicle speed exceeds a predetermined value, the difference value kR-kF between the front wheel spring constant kF and the rear wheel spring constant kR takes a positive value. Since the spring constant of the variable spring constant spring mechanism is set, it is possible to significantly reduce the pitching phenomenon in high-speed driving conditions where the vehicle speed exceeds a predetermined value, thereby improving driving stability and ride comfort during high-speed driving. You can get the same effect.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram showing an overview of the present invention, Fig. 2 is a schematic configuration diagram showing an embodiment of the invention, and Fig. 3 is a process for switching the spring constant by the controller in the embodiment of Fig. 2. A flowchart showing the procedure, FIG. 4 is an explanatory diagram explaining the relationship between vehicle speed and front wheel spring constant, and FIG. 5 is a graph explaining the relationship between front and rear wheel strokes and spring constant.
Figure 6 (1) is an explanatory diagram explaining the undulating road, Figure 6 (2)
) is a graph showing the relationship between spring constant and pitch angle change. In the figure, 1) is a variable spring constant spring mechanism, 20 is a controller, 22 is a vehicle speed sensor, 24 is a microcomputer, and 26F and 26R are drive circuits.

Claims (1)

[Claims] (1) A vehicle suspension comprising a variable spring constant spring mechanism capable of changing the spring constant in at least two high and low levels on at least one of the front wheels and the rear wheel, comprising a vehicle speed detecting means for detecting vehicle speed, and the vehicle speed. A vehicle speed determining means for determining whether the vehicle speed by the detecting means exceeds a predetermined value, and a front wheel spring constant k_F and a rear wheel spring constant k_R when the vehicle speed determining means determines that the vehicle speed exceeds a predetermined value. A control device for a vehicle suspension, comprising: a spring constant setting means for setting a spring constant of the variable spring constant spring mechanism so that the difference value k_R−k_F takes a positive value.