JPH06179316A - Control device for vehicle suspension - Google Patents

Abstract

PURPOSE:To reduce the peak of body vibration when running over a protuberance while driving on a favorable road and improve vibration astringency by detecting the protuberance run-over while driving on a favorable road and thereby changing and controlling threshold value to a small value and maintaining a damper immovably to a low damping force characteristic, when the vertical displacement speed of a spring top is within the range of the threshold value. CONSTITUTION:A suspension control device is provided with a threshold value change control means 6, which is composed of a protuberance run-over judging unit 61 for making judgment of running over a protuberance when the vertical relative displacement speed between the top and the bottom of a spring exceeds a protuberance identification set value alpha and a threshold value change setting unit 62, which sets the threshold value to a small value delta for a certain time based on the judgment of the protuberance run-over judging unit 61 and then restores the threshold value to an original large value delta upon elapse of a certain time. While running on a favorable road, the control of riding comfortablenss preference is carried out by improving vibration isolatability against vibration input of high frequency and small amplitude near a spring bottom resonance frequency band. Improvement of vibration astringency is aimed by enabling the spring top vertical displacement speed to easily exceed the dead band.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle suspension control device.

[0002]

2. Description of the Related Art Research has been made in the past to switch the damping force of a damper in real time according to the vibration condition of a vehicle in order to further improve riding comfort, one of which has been disclosed in Japanese Patent Laid-Open No.
It is disclosed in Japanese Patent Publication No. 1-163011.

This prior art is a damping force variable damper (shock absorber) capable of switching between a hard damping force characteristic on both the extension side and the compression side and a soft damping force characteristic on both the extension side and the compression side. The vertical displacement speed of the sprung body (that is, the vehicle body) and the vertical relative displacement speed (suspension speed) between the sprung body and the unsprung body are detected, and these are upward (for example, +) or downward (for example, −). The damping force characteristic of the damper is switched to a hard characteristic when both are upward or downward, and a soft characteristic when one is upward and the other is downward. It is the one.

[0004]

The above is based on the theory of the skyhook damper (a virtual model in which one wheel suspension is regarded as one degree of freedom and a damping effect is exerted on an absolute space). It is approximated by a damping force variable damper mounted at a position, and has an effect that the ride comfort can be improved by optimizing the vehicle body vibration near the natural frequency (1-2 Hz) of the vehicle body. However, on the other hand, in the above-mentioned conventional control, the damper characteristics are switched even by the high-frequency, small-amplitude vibration input centered on the unsprung resonance frequency band, and control for such high-frequency, small-amplitude vibration is performed. Has a problem in that follow-up is mechanically difficult, leading to deterioration in ride comfort due to delay in follow-up, and a decrease in durability becomes a problem due to an increase in the number of switching times.

For the purpose of solving the above-mentioned problems, the present applicant has previously set a threshold value δ on the vertical displacement speed on the spring, and within the range where the vertical displacement speed on the spring is less than the threshold value δ, the vertical displacement on the spring is set. High-frequency, small-amplitude vibration is maintained by maintaining soft or slightly soft damping force characteristics on both the extension side and compression side, regardless of whether the speed direction and the suspension stroke speed direction are the same or opposite. A control method and a control device were developed to improve the vibration insulation property against the input and reduce the switching frequency of the damper so as to improve the durability. Japanese Patent Application No. 3-135432 and Japanese Patent Application No. 3-135432. Thirteen
Patent pending as 5433.

As described above, in the method of setting the threshold value δ for the sprung vertical displacement speed by fixing it to a certain constant value, the damper is always soft or slightly soft on both the extension side and the compression side during running on a good road. Since the damping force characteristic is maintained, there is a problem that when a good road has a projection and the vehicle rides over it, the peak of the vehicle body vibration is large and the convergence is poor and the ride feeling becomes fluffy.

An object of the present invention is to solve the above-mentioned problems of the suspension control device in which the threshold value is set for the vertical displacement speed on the spring.

[0008]

SUMMARY OF THE INVENTION The present invention uses a damper whose damping force characteristics can be switched, depending on whether the direction of vertical displacement velocity on the spring and the direction of suspension stroke velocity are the same or different. Alternatively, a vehicle suspension control device that performs switching control of the damping force characteristics of the damper depending on whether the direction of the vertical displacement speed on the spring is upward or downward, wherein a threshold value is set for the vertical displacement speed on the spring, When the vertical displacement speed is within the range of the threshold, the damper is fixedly held to have a low damping force characteristic. It is characterized in that threshold change control means for controlling the change is provided.

[0009]

In the above, during normal running on a good road, the threshold value of the vertical displacement speed on the spring is set to a relatively large value, which allows vibration isolation against high-frequency and small-amplitude vibration inputs near the unsprung resonance frequency band. When the rider rides over a bump on a good road, the threshold value is changed to a small value. Is more likely to exceed the threshold value, that is, the dead zone, and as a result, damping control by the damping force characteristic switching control of the damping force variable damper is accurately performed, the peak of vehicle body vibration due to riding over the protrusion is reduced, and the vibration convergence is improved. Be peeled off.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and shows an example in which the present invention is applied to the invention of Japanese Patent Application No. 3-135433 mentioned above as a prior patent.

That is, in the first embodiment, the front, rear, left and right 4
As a damper for each suspension of the wheel, as shown in FIG. 1 (A), a characteristic a of high damping force on both the extension side and the compression side (shown by a solid line) and a characteristic b of low damping force on both the extension side and the compression side (dotted line) 2) and a damping force variable damper known in the related art, which can switch the two damping force characteristics by an electric signal.

FIG. 1B is a model diagram in which a controller 5 for controlling the one-wheel model of the suspension equipped with the damping force variable damper is combined, and 1 is a damping force variable damper (hereinafter simply referred to as a damper). 2 is a suspension spring, 3 is a vertical acceleration sensor for detecting vertical acceleration on the spring, 4 is a suspension stroke sensor for detecting vertical relative displacement between the sprung portion and the unsprung portion, that is, a suspension stroke. The sensors 3 and 4 are attached to each suspension. Also, in FIG. 1 (B), M1 and K
1 represents the unsprung, that is, the tire mass and spring constant,
M2 is the sprung mass of the vehicle body, K2 is the spring constant of the suspension spring 2, C is the damping coefficient of the damper 1, and X0 is
Is the vertical displacement of the road surface, X1 is the vertical displacement under the spring, and X2 is the vertical displacement on the spring.

The controller 5 includes an integrating circuit 51 for obtaining the vertical displacement speed on the spring from the detection signal of the vertical acceleration sensor 3 and a vertical relative displacement speed between the sprung and unsprung springs from the detection signal of the suspension stroke sensor 4, that is, The integrating circuit 5 is provided with a differentiating circuit 52 for obtaining the suspension stroke speed.
The absolute value of the vertical displacement velocity on the spring obtained by 1 (the vertical displacement velocity direction is represented by a sign of + for the upward direction and − for the downward direction) is a threshold value δ selected and set by the threshold value change control means 6 described later. If it is δ or more, the direction of the suspension stroke speed obtained by the differentiating circuit 52 (the upward sign is represented by + and the downward sign is represented by −) and the vertical direction. It is judged whether the direction of the displacement velocity is the same or different, and if it is the same, the high damping force characteristic a is selected, and if it is different, the low damping force characteristic b is selected, and the damping of the damper 1 is selected. Generates a signal to switch force characteristics. When the vertical displacement speed is less than the threshold value δ, the low damping force characteristic b is selected and a signal for causing the damper 1 to have the low damping force characteristic is emitted. Reference numeral 6 denotes a threshold value change control means for changing and controlling a threshold value δ of the vertical displacement speed on the spring, and the threshold value change control means 6 determines a projection crossover judging section for judging a projection crossing on a good road from the information of the suspension stroke speed. 61, and a threshold value change setting unit 62 that changes and sets the threshold value δ to a small value for a certain period of time in response to the signal when the projection / ride-over determination unit 61 determines that the road / projection is over a good road.

When the absolute value of the suspension stroke speed is equal to or larger than the projection determination set value α, the projection overpass determination unit 61 compares whether or not the absolute value of the suspension stroke speed is equal to or larger than the projection determination set value α. Is it judged that it is over the projection,
Alternatively, when the absolute value of the suspension stroke speed is equal to or larger than the protrusion determination set value α and is equal to or larger than the set value α ′ for a predetermined time (for example, 0.02 seconds) or more, it is determined that the vehicle is over the protrusion, and a signal is issued. The threshold change setting unit 62 sets the threshold δ
Is set to a small value δ ′ (for example, a value of about 50% of δ), and is returned to the original threshold value δ after a predetermined time t (for example, about 3 seconds) is changed. In the above, the control may be such that the threshold value is gradually returned from δ ′ to δ after the predetermined time t elapses after the threshold value is changed to the small value δ ′.

As described above, the threshold value changing control means 6 sets the threshold value δ for determining the dead zone of the damping force characteristic switching control of the damper 1.
By changing and setting to a small value δ ′ for a certain period of time when riding over bumps during running on a good road and returning to the original large value δ after the lapse of the certain time, during normal running on a good road When the threshold value δ is set to be large (the dead band region of the sprung vertical displacement speed is set to be large), vibration control with good vibration insulation and good ride comfort is performed for high-frequency, small-amplitude vibration inputs, and while driving on a good road. When the projection is crossed over, the threshold δ is reduced to a small value δ ′
As a result, the sprung vertical displacement speed that occurs when the vehicle overhangs the protrusion easily leaves the dead zone region, whereby the damping force characteristic switching control of the damping force variable damper 1 is performed for the vibrations that occur when the vehicle overhangs the protrusion, and the vehicle body based on the overpassing of the vehicle It is possible to reduce the peak of vibration and improve the vibration convergence. After a certain period of time has passed after switching to δ ′, that is, after the vehicle body vibrations have converged, the threshold value returns to the original large value δ, and vibration suppression control with good vibration insulation is performed against high-frequency, small-amplitude vibrations under the spring. .

FIG. 2 shows a second embodiment of the present invention and shows an example in which the present invention is applied to the invention of Japanese Patent Application No. 3-135432 mentioned above as a prior application. That is, in this example, as the damping force variable damper 1 equipped on the front, rear, left and right four-wheel suspension, as shown in FIG. 2A, the extension side is soft (low damping force) and the compression side is hard (high damping force). ) Which is hard (high damping force) on the extension side and soft (low damping force) on the compression side which is soft (low damping force) on both the extension side and the compression side. A damping force variable damper is used which has three modes, a third mode c '(shown by a chain line), which is slightly soft (slightly low damping force), and these modes are switched by an electric signal. Vertical displacement speed on the spring obtained by integrating the detection signal of the vertical acceleration sensor 3 for detecting the vertical acceleration on the spring by the integration circuit 51 of the controller 5 (the upward / downward displacement speed is indicated by + in the upward direction and − in the downward direction). The absolute value of Determine whether less than [delta], the third is less than [delta]
If the mode c'is selected and is δ or more, it is determined whether the direction of the vertical displacement speed is upward or downward. If the mode is upward, the second mode b'is selected. If the mode is downward, the first mode a is selected. ′ Is selected and a signal for switching the mode of the damping force variable damper 1 is issued according to the selection. Therefore, in this example, the suspension stroke sensor 4 and the differentiating circuit 52 can be omitted and the switching frequency of the damper 1 can be further reduced as compared with the first embodiment shown in FIG.

In this embodiment, the protrusion crossover judging section 61 of the threshold value change control means 6 for changing and setting the threshold value δ is
For example, a band pass filter (BPF) or a high pass filter (HPF) that passes the detection signal of the vertical acceleration sensor 3 (the vertical acceleration signal on the spring) only through the unsprung resonance frequency band,
Low-pass filter (LPF) or frequency analyzer (FF
T) and the like, and a determination circuit 61b for determining whether or not the vehicle is over a bump on a good road based on the vertical acceleration signal processed by the signal processing circuit 61a. The threshold change setting unit 62 changes and sets the threshold value δ to a small value δ ′ (for example, a value of about 50% of δ) in response to the lowered projection crossing determination signal, and after the predetermined time t (for example, about 3 seconds) has passed, the original δ is set. To return to. in this case,
Control may be performed such that the threshold value is gradually returned from δ ′ to δ within a predetermined time t after switching to δ ′.

When performing bandpass filter processing in the signal processing circuit 61a, when the value after bandpass filter processing is equal to or greater than a set value, or the value is equal to or greater than the set value continues for a predetermined time (eg, 0.02 seconds) or more. When I did
The determination circuit 61b determines that it is over the protrusion. When performing high-pass filter processing, sprung resonance (1 to
Gain near 2Hz decreases and unsprung resonance (10-20Hz)
Use a high pass filter that does not reduce the gain of (near),
When the absolute value of the value after high-pass filtering is equal to or greater than the set value, or when the absolute value is equal to or greater than the set value for a predetermined time (for example, 0.
When it continues for more than 02 seconds, the determination circuit 61b determines that it is over the protrusion. When performing low-pass filter processing, the vibration transfer characteristics of the suspension (around 1 to 2 Hz) are approximated by a low-pass filter, and the difference between the sprung vertical acceleration signal and the signal value after low-pass filtering is calculated, and the difference Is greater than or equal to a certain set value, or when the state of being greater than or equal to the set value continues for a predetermined time or longer, the determination circuit 61b determines to be over the projection. When a frequency analyzer (FFT) is used, the FFT processed value in the sprung resonance frequency range and the FFT processed value in the unsprung resonance frequency range are calculated, and the ratio of these FFT processed values is calculated. If it exceeds the value or the rate of change of that value (the ratio of the above two FFT processed values) exceeds a certain value (eg 1.2),
The determination circuit 61b determines that it is over the protrusion.
In the above description, the signal processing circuit 61a is omitted, and when the absolute value of the detection value of the vertical acceleration sensor 3 is equal to or greater than the set value or when the state of being equal to or greater than the set value continues for a predetermined time or longer, the determination circuit 61b You may judge it to get over a protrusion.

In the embodiment of FIG. 2 as well, as in the embodiment of FIG. 1, the threshold value δ for determining the dead zone of the damping force characteristic switching control of the damper 1 is variably controlled by the threshold value changing control means 6. During normal running on a good road, the threshold δ is set to a large value to improve vibration isolation against high-frequency and small-amplitude vibration input near the unsprung resonance frequency band, and vibration control with priority on ride comfort is performed. In the case where the projection is crossed over, the threshold value is switched to a small value δ ′ for a certain period of time and the damping force characteristic switching control of the damper 1 is performed, so that the peak of the vehicle body vibration due to overcoming the projection is reduced and the convergence of the vehicle body vibration is also reduced. Improves and eliminates the fluffy feeling when riding over bumps on good roads.

Note that the reference numerals in FIG. 2B correspond to those in FIG.
The same reference numerals as in FIG.

In the first embodiment shown in FIG. 1,
Although an example of detecting the over-projection on a good road from the information on the suspension stroke speed is shown, the over-projection on a good road can be detected from the vertical acceleration information on the signal processed signal similarly to the embodiment of FIG. You may

In the second embodiment shown in FIG. 2, the damping force characteristic switching control of the damping force variable damper 1 is performed only by the information on the vertical displacement speed on the spring obtained by integrating the vertical acceleration on the spring. However, since it is configured such that the information about the suspension stroke speed is not required, it is preferable to detect the over-projection on a good road from the vertical acceleration information on the spring as shown in the figure, but other than damping force characteristic switching control. When the suspension stroke sensor is equipped for some purpose (for example, for vehicle height control), the suspension stroke speed information obtained by differentiating the detection signal of the suspension stroke sensor from the embodiment of FIG. You may make it detect the overrun of a protrusion by the same method. The control mode in this case is as shown in the flowchart of FIG.

In each of the above-mentioned embodiments, the threshold value δ is changed and set in two steps, that is, the threshold value change control means 6 sets the threshold value based on the information about the suspension stroke speed or the signal-processed vertical acceleration on the spring. It is also possible to finely change and control δ in three steps of large, medium and small or in a plurality of steps of more than three steps.

[0025]

As described above, according to the present invention, the damper capable of switching the damping force characteristics is used, and whether the direction of the vertical displacement speed on the spring is the same as or different from the direction of the suspension stroke speed, or the spring is used. A controller for a vehicle suspension equipped with a controller that switches the damping force characteristic of the damper depending on whether the direction of the upper vertical displacement speed is upward or downward.
Within the range of the vibration, soft or slightly soft damping force characteristics are fixedly maintained to improve the vibration insulation for high-frequency and small-amplitude vibration inputs near the unsprung resonance frequency band, and vibration control with ride comfort priority. In this case, by providing a threshold value change control means for determining whether or not the projection gets over when traveling on a good road and changing and setting the threshold δ to a small value, when the projection gets over while traveling on a good road. The vehicle body vibration control is performed accurately, and the riding comfort can be further improved. In addition to the fact that the number of sensors does not need to be increased and the configuration is simple, it can bring a great practical effect. It is a thing.

[Brief description of drawings]

1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a diagram showing damping force characteristics of a variable damping force damper, and FIG. 1B is a one-wheel model of a suspension and a controller for controlling the same. It is a model drawing.

2A and 2B show a second embodiment of the present invention, in which FIG. 2A is a diagram showing a damping force characteristic of a variable damping force damper, and FIG. 2B is a one-wheel suspension model combined with a controller for controlling the same. It is a model drawing.

FIG. 3 is a flow chart showing an example of a control mode in another embodiment of the present invention.

[Explanation of symbols]

 1 Damping Force Variable Damper 2 Suspension Spring 3 Vertical Acceleration Sensor 4 Suspension Sensor 5 Controller 6 Threshold Change Controlling Means 51 Integrating Circuit 52 Differentiating Circuit 61 Protrusion Override Determination Section 62 Threshold Change Setting Section

Claims (3)

[Claims] 1. A damper provided on each of the front, rear, left and right suspensions is a damping force variable damper capable of switching between high damping force characteristics and low damping force characteristics in two steps, and a vertical displacement speed on a spring is within a threshold range. Within the range in which the vertical displacement speed on the spring exceeds the threshold value, the two directions of the vertical displacement speed and the vertical relative displacement speed between the unsprung and unsprung springs are in the following directions. In a vehicle suspension controller that controls switching of the damping force characteristics of the damper to the high damping force characteristics if they are the same, and to the low damping force characteristics if they are in different directions, it is possible to detect a constant overhang on a bumpy road during running on a good road. A vehicle suspension control device comprising threshold changing control means for changing the threshold to a small value for a time. 2. A damper installed on each of the front, rear, left and right suspensions, which has a first mode having characteristics of low damping force on the extension side and high damping force on the compression side, and high damping force on the extension side and low on the compression side. A damping mode variable damper having a second mode having damping force characteristics and a third mode having slightly lower damping force characteristics on both the expansion side and the compression side, and a damping force variable damper capable of switching these three modes is used. When the upper vertical displacement speed is within the threshold range, the third mode is selected, and when the vertical displacement speed on the spring exceeds the threshold value, the first mode is selected when the vertical displacement speed is downward. In a vehicle suspension control device that switches and controls the mode of the damper so that the second mode is set when the vehicle is in the upward direction, bumping over a bump on a good road is detected and the threshold value is changed to a small value for a certain period of time. Threshold change control means installed A control device for a vehicle suspension, which is characterized by being discontinued. 3. The vehicle suspension control device according to claim 1 or 2, wherein the threshold value changing control means is good on the basis of a vertical relative displacement velocity signal between the sprung and unsprung portions or a sprung vertical acceleration signal. It is characterized in that it is composed of a projection crossover judging unit for judging projection crossing over on a road, and a threshold value change setting unit for changing and setting a threshold value to a small value for a certain period of time in accordance with the projection crossover judging signal of the projection crossover judging unit. Control device for vehicle suspension.