JP2687704B2 - Suspension control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a vehicle suspension control device,
In particular, the present invention relates to a device capable of controlling switching of damping force characteristics of a shock absorber in a manner adapted to the running state of a vehicle.

[Prior Art] In order to adapt the suspension characteristics of a vehicle to the running state of the vehicle, a shock absorber is provided on each of a pair of left and right wheels, the damping force characteristics of which can be switched between hard and soft, and each shock absorber. A pair of left and right detectors are installed to detect the time change rate of the damping force that is actually occurring in each of the above. ・ When the detected time change rate exceeds the switching reference value (Vref), the damping force of the shock absorber A vehicle equipped with a controller for switching the characteristics from hard to soft has been developed, and an example thereof is disclosed in Japanese Patent Laid-Open No. 64-67407.

In the technology described in the publication, a piezo element for enlarging and reducing the orifice is built in the shock absorber, and a voltage is applied to the piezo element to extend the orifice, thereby enlarging the orifice and weakly resisting vibration (that is, generating Adjust to a so-called soft state where the damping force is weak,
On the contrary, by not applying a voltage, the piezoelectric element is contracted to reduce the orifice, and the resistance to vibration is adjusted to be large (that is, a so-called hard state in which a large damping force is obtained).

Also, in this technique, each shock absorber is provided with a piezo element having a property of being polarized by receiving stress, and a current flowing through the piezo element is input to a controller. The current flowing through the piezo element corresponds to a value obtained by time-differentiating the amount of charge polarized in proportion to the stress, so that the time change rate of the damping force actually generated by each shock absorber is detected.

The controller compares this rate of change with the switching reference value,
When the detected rate of change is less than the reference value, the damping force characteristic is hardened, and when the detected rate of change exceeds the reference value when the vehicle approaches the unevenness, the damping force characteristic is softly switched.

As a result, the damping force characteristic is always maintained to be hard and the posture of the vehicle is stabilized, and when the road surface condition deteriorates, it is switched to soft to secure the riding comfort.

In the technique disclosed in JP-A-64-67407, the switching reference value is increased / decreased according to the vehicle speed or whether braking is being performed, so that the damping force switching control is performed in a manner adapted to the running state. ing.

Further, Japanese Patent Laid-Open No. 60-82423 discloses a technique for forcibly making the damping force characteristic hard during sudden braking.

[Problems to be Solved by the Invention] The above-described conventional technique is capable of obtaining both a stable vehicle posture and a comfortable ride in a well-balanced manner, and performs a very excellent control. However, if the left and right wheels are running differently,
For example, in the case of so-called straddle running in which the right wheel runs on snow and the left wheel runs on a dry road, the damping force change rates of the left and right wheels may differ greatly, and the damping force characteristics may differ between the left and right wheels. In such a case, the road surface friction coefficients that the left and right wheels pass through are greatly different, and therefore, when braking is applied, the posture change is more likely to occur than during normal braking that does not run across. Therefore, if only straddle running is taken into consideration, Japanese Patent Laid-Open No.
As in the case of 82423, it is sufficient to maintain the damping force characteristics in a hard state at all times during sudden braking, but this way the damping force characteristics can be switched softly even when there are large irregularities during non-crossing braking. There is a problem that the riding comfort becomes poor.

Therefore, the present invention proposes a device in which switching of damping force characteristics is controlled in a manner optimal for straddle traveling during straddle traveling.

[Means for Solving the Problems] The above-mentioned problems are provided in a device whose system configuration is schematically shown in FIG. 1, that is, in each of a pair of left and right wheels,
A pair of left and right shock absorbers 2L, 2R capable of switching the damping force characteristics between hardware and software, and a pair of left and right detection devices 4L, 4R for detecting the values relating to the damping force actually occurring in each of the shock absorbers. A vehicle equipped with a shock absorber controller 6 that switches the damping force characteristic of the shock absorber from hard to soft when the value detected by the detection device exceeds a switching reference value (Vref), and travels from the running state of the vehicle. Means for determining whether the vehicle is in the middle or not, and means 12 for inputting a signal corresponding to whether the vehicle is being braked or not are added to the shock absorber controller 6, and the shock absorber controller 6 is being braked. In addition, if the condition for straddling is satisfied, the switching reference value (Vref) should be set to a value larger than that under other conditions. It is solved that were built a procedure 6a which are the suspension control system according to claim.

[Operation] Here, the controller 6 is input with a signal indicating whether or not the vehicle is traveling astride from the traveling state of the vehicle and a signal indicating whether the vehicle is being braked. When the condition to be satisfied is satisfied, the process for increasing the switching reference value (Vref) when switching the damping force characteristic from hard to soft is built-in, so when braking while straddling, it is especially Unless there is a large road surface input, that is, in the normal case, the damping force characteristic is almost always maintained in a hard state, and the vehicle attitude is stabilized.

[Embodiment] Next, an embodiment embodying the present invention will be described with reference to FIGS.

In FIG. 2, reference numeral 60 denotes a microcomputer, and the current flowing through the detection piezo element for detecting the damping force obtained by the left shock absorber 2L is I / O22, A /
It is possible to input to the CPU 34 via the D converter 28. Here, the detecting piezo element is the same as that described in JP-A-64-67407, and therefore, this current value corresponds to the time change rate of the damping force. Similarly right shock absorber
The 2R damping force change rate is also input to the CPU 34 via the I / O 24 and the A / D converter 30. In addition, the signal of the brake switch is also input to the CPU 34 via the I / O 26, and it is possible to input to the CPU 34 whether or not the braking is being performed.

The CPU 34 operates according to a program stored in the ROM 32, and outputs a signal indicating whether to apply a voltage to the drive circuits 44 to 46 via the I / Os 40 to 42 according to the processing result. When a signal for applying a voltage to the left drive circuit 44 is input, a high voltage is generated in the left drive circuit 44, and a high voltage is applied to the piezo element for switching the damping force characteristic of the left shock absorber 2L, and the high voltage is applied to the left shock absorber 2L. Make the damping force characteristic soft. Similarly, when a signal for applying a voltage is output to the right drive circuit 46, the right shock absorber 2R is adjusted to have a soft damping force characteristic. When the CPU 34 does not output the signal for applying the voltage, the damping force characteristic of the shock absorber is adjusted to be hard. As the piezo element for switching the damping force characteristic, a piezo element similar to that disclosed in JP-A-64-67407 is used.

A program for executing the processing procedure shown in FIGS. 3 and 4 is stored in the ROM 32.

FIG. 3 shows a processing procedure for instantaneously obtaining the amplitude difference between the left and right damping force change rates, which is repeatedly executed at a time interval sufficiently shorter than the vibration cycle.

Step S1 inputs the current flowing through the left detecting piezo element via the I / O22 and A / D converter 28, and then the current flowing through the right detecting piezo element through the I / O24 and A / D converter 30. Value is CPU3
Enter 4

Step S2 is a step of performing a process of determining whether or not the left damping force change rate is a maximum value, and specifically, whether the input damping force change rate has changed from an increasing tendency to a decreasing tendency is determined. Determine. If it is the maximum value, that value is set as the left maximum value (S3). After that, based on almost the same idea, the right maximum value (S5), left minimum value (S7), right minimum value (S
9) is set. As a result, the latest maximum value and minimum value are stored in each extreme value.

Based on the extreme value thus stored, step S1
At 0, the left and right amplitudes are obtained respectively, and at step S11 the amplitude difference is obtained.

As will be understood from the above, the difference between the amplitudes of the left and right damping force change rates is calculated by the processing of FIG. That is, the program for executing the process of FIG. 3, the ROM 32 for storing the program, the CPU 34, the RAM 36, etc. involved in the execution of the program constitute the left-right difference calculating means 8 of FIG. .

FIG. 4 shows a processing procedure for determining whether the left-right amplitude difference calculated in this way is equal to or more than a predetermined value. In this embodiment, whether the left-right difference is more than a predetermined value continuously for a predetermined time or more. Determine whether or not. The process of FIG. 4 is repeatedly executed at predetermined time intervals.

Now, in step S20 of FIG. 4, a process of determining whether or not the amplitude difference calculated in S11 of FIG. 3 is a predetermined value or more is executed. If the value is within the predetermined value, it means that the vehicle is not straddling. Therefore, in step S27, the switching reference value Vref is changed to the standard reference value Vref S
A predetermined ratio (this is the anti-dive correction coefficient K1BRK
Say) big. Here, K1BRK is Japanese Patent Laid-Open No. 60-8.
As disclosed in Japanese Patent No. 2423 or 64-67407, it is a correction coefficient for strengthening the hard holding tendency during braking to obtain an anti-dive effect. In this case, the counter C
Is cleared to zero (S26), and the number of times (that is, elapsed time) since the amplitude difference is increased by the counter C can be counted.

Step S21 is a process for timing, and since the process of FIG. 4 is executed at constant time intervals, as a result of the process of S21, when the determination in step S20 of the counter C changes from NO to YES ( That is, a number proportional to the time from when the amplitude difference starts to become equal to or larger than a predetermined value is stored.

In step S22, the counted C is the predetermined value C
This is a procedure for determining whether or not it is equal to 1. Here, the result is YES when the left and right amplitude difference continuously exceeds a predetermined value for a certain period of time or more. Since this state may be regarded as straddling traveling, in step S23, the anti-dive correction coefficient K2BRK during straddling braking is used to calculate the switching reference value Vref. Here, the anti-dive correction coefficient K2BRK for straddling braking
Is a value that is larger than the anti-dive correction coefficient K1BRK during non-spanning traveling, so even if there is vibration that causes the damping force characteristics to switch to fusoto during non-spanning braking, A tendency to keep it hard is given.

In this way, the difference between the left and right is compared with the predetermined value by the processing of step S20 in FIG. 4, and it is involved in the program for executing this, the ROM 32 storing the program, and the execution of the program. The CPU 34, the RAM 36, etc. constitute the comparison means 10 shown in FIG. Step S2
When 0 becomes yes (in this embodiment, S22
However, this is a process for preventing erroneous determination as straddle traveling when not straddling, and is not always necessary). A process for calculating a larger switching reference value Vref that strengthens is executed, and when the result is NO, a small switching reference value Vref having a stronger soft holding tendency than that is calculated in step S27.

As can be understood from the above, the control system 6 including the microcomputer 60 and the drive circuits 44 and 46 shown in FIG.
The reference numeral 2 functions as a combination of the left-right difference calculating means 8, the comparing means 10 and the shock absorber controller 6 shown in FIG.

In the above embodiment, during the straddle braking, the switching reference value when the damping force is softly switched is set to a value larger than the switching reference values during the other braking, so that the vehicle attitude is stabilized during the straddling braking. Is planned.

It should be noted that instead of this embodiment, when straddle braking is detected, the damping force characteristic may be forcedly maintained to be hard, and even in this case the vehicle attitude during straddle traveling can be stabilized. . Further, in the above embodiment, an example of detecting the straddle running on one of the front wheels or the rear wheels is shown, but instead, while straddle running is detected on either the front wheels or the rear wheels, or A large anti-dive correction coefficient K2BRK may be used while straddling traveling is detected on both the front and rear wheels.

Furthermore, in this embodiment, in order to detect the straddle running, a method of calculating the amplitude difference of the damping force change rate is adopted, but instead, the straddle running is detected from the left and right amplitude difference of the damping force itself. May be.

[Advantages of the Invention] According to the present invention, since the switching reference value of the damping force characteristic is made larger than the switching reference value at the time of non-spanning braking when braking under conditions where the road surface conditions on the left and right are different, At times, the hard holding tendency can be further strengthened as compared with non-spanning braking. Therefore, during straddle braking, the stabilization of the vehicle attitude is considered with priority, while during non-spanning braking, the damping force characteristics are switched in a manner that achieves both the stabilization of the vehicle attitude and the riding comfort. As described above, according to the present invention, the damping force characteristics can be switched in a more preferable mode as compared with the conventional method in which the straddle braking and the non-span braking are not distinguished.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the concept of an apparatus according to the present invention,
FIG. 2 is a system configuration diagram of an embodiment, and FIGS. 3 and 4 are diagrams showing a processing procedure used in the embodiment.

Claims (1)

(57) [Claims] 1. A pair of left and right shock absorbers provided on each of a pair of left and right wheels and capable of switching a damping force characteristic between hard and soft, and a value relating to a damping force actually occurring in each of the shock absorbers. In a vehicle equipped with a pair of left and right detection devices for detecting a shock absorber, and a shock absorber controller for switching the damping force characteristic of the shock absorber from hard to soft when the detection value by the detection device exceeds a switching reference value (Vref) A means for determining whether or not the vehicle is traveling from the traveling state, and means for inputting a signal corresponding to whether or not the vehicle is being braked to the shock absorber controller, and the shock absorber controller is provided with a braking means. In the middle, and when the condition for straddling is satisfied,
A suspension control device having a built-in processing procedure that uses a larger value as the switching reference value (Vref) than in other conditions.