JP2853392B2 - Suspension control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damper in which the characteristic of generating a force for attenuating vibration generated between a vehicle body and wheels is variable, that is, a large damping force is generated if the characteristic is adjusted to a high damping force generating characteristic. The present invention relates to a suspension device capable of reducing vibrations rapidly and adjusting the low damping force generation characteristics to generate only a small damping force and gradually reducing vibrations.

[0002]

2. Description of the Related Art In a vehicle provided with a vibration damper having a variable damping force generation characteristic, damping force change rate detecting means for outputting a signal corresponding to a change rate V of the damping force generated by the damper, Means for calculating the reference change rate Vref, and when the change rate V detected by the damping force change rate detecting means exceeds the reference change rate Vref calculated by the reference change rate calculating means, the attenuator generates a low damping force. Vehicles with a controller for switching to a state have already been developed.

According to this vehicle, the damper is normally in a state where a high damping force is generated, and when the vibration starts to be generated, the state is switched to a state where a low damping force is generated, so that the vibration generated in the vehicle body can be reduced. Further, a technology of learning and updating the reference change rate Vref in accordance with the road surface condition has been developed (Japanese Patent Laid-Open No. 3-96).
No. 414). In this technique, the current reference change rate Vre
means for calculating the learning change rate Vref G at a level lower than f;
A means for calculating a frequency exceeding fG and a reference change rate learning means for learning and updating the reference change rate Vref based on the calculated frequency are added.

If the reference change rate learning means is added, the reference change rate Vref is learned and updated in accordance with the running state of the vehicle. For example, if the vehicle travels on a good road for a long time, the reference change rate Vref is learned and updated so that the damper can be switched to a low damping force generating state with a small vibration. While traveling on a good road for a long time, the passenger becomes sensitive to even a slight vibration. Therefore, by learning the reference change rate, the attenuator can be switched in a manner that matches the human sense.

[0005]

However, this technique still has points to be improved. In the prior art, the frequency at which the actual damping force change rate exceeds the reference change rate is calculated. Here, since a sufficient learning opportunity or a sufficient number of data is required to calculate a reliable frequency, the frequency calculation period cannot be shortened unnecessarily. In the actual technology, the frequency of the past one second is learned. Therefore, when the road surface state changes in a short time, learning is delayed, and the reference change rate Vref may not correspond to the road surface state. Therefore, in the present invention, a suspension control device capable of following a change in road surface condition at high speed is developed.

[0006]

In order to solve the above-mentioned problems, according to the present invention, a suspension control device whose concept is schematically shown in FIG. 1 is provided, that is, a vibration generated between a vehicle body and wheels is damped. A variable damping force generation characteristic vibration damper C having a variable force, and a damping force change rate detecting means for outputting a signal V corresponding to a change rate of the damping force generated by the variable damping force generation characteristic vibration damper C. E, the damping force change rate detecting means E
The actual damping force change rate extreme value calculating means D for calculating the extreme value VP of the damping force change rate signal detected in step 1, the target damping force change rate extreme value indicating means A for indicating the target extreme value VT, the actual damping force change rate The actual extreme value VP calculated by the extreme value calculating means D is compared with the target extreme value VT indicated by the target damping force change rate extreme value indicating means A. If the actual extreme value VP exceeds the target extreme value VT, When the actual extreme value VP falls below the target extreme value VT, the variable damping force generation characteristic vibration damper C is set to a high damping force. And a controller B for adjusting the characteristics of the suspension to the side that generates the suspension.

[0007]

With this configuration, the correspondence between the road surface condition and the damping force generation characteristic at that time is determined by the extreme value V of the damping force change rate V.
It is grasped by P. If the road surface is rough but the high damping force generation characteristic is set, a large damping force change rate V occurs, and the actual extreme value VP increases. If the road surface is good and the low damping force generation characteristic is set, the actual extreme value VP becomes small with only a small damping force change rate V. The actual extreme value VP is an appropriate value when it is adjusted to a low damping force generation characteristic on a rough road surface and to a high damping force generation characteristic on a good road. In the device according to the present invention, the actual extreme value VP is compared with the target extreme value VT, and if the actual extreme value VP is higher than the target extreme value VT, the actual extreme value VP If the value is lower than the target extreme value VT, it is adjusted to the high damping force generation characteristic side. For this reason, it is adjusted with good followability to a low damping force generation state on a rough road surface and to a high damping force generation state on a good road.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 2, reference numeral 20 shows a vibration damper having a variable damping force generation characteristic, which is assembled between a suspension lower arm 22 supporting wheels 24 and the vehicle body 2 to attenuate vibration between the vehicle body 2 and the wheels 24.
The attenuator 20 attenuates the vibration by the flow resistance when the working fluid filled in the piston upper chamber 12 and the lower chamber 18 passes through the flow path 15 as the piston 14 moves up and down. In addition, sub-flow paths 10, 16 for communicating the upper piston chamber 12 with the lower chamber 18 and a piezo actuator 8 for opening and closing the same are incorporated.

The piezo actuator 8 is composed of a piezoelectric element laminate, a displacement enlarging mechanism, a plunger, and an orifice whose flow path area can be switched in multiple stages by the plunger. open. When a voltage of +450 volts is applied to the piezoelectric element laminate, the throttle opens to the maximum, the flow passage area between the piston upper chamber 12 and the lower chamber 18 becomes maximum, and the characteristic is adjusted to generate the smallest damping force. . As the applied voltage decreases, the diaphragm area decreases, and the state is adjusted so as to gradually generate a large damping force. When the applied voltage is zero, the diaphragm area becomes zero and the characteristic is adjusted to generate the largest damping force.

In order to detect the damping force generated in the damper 20, that is, the force acting on the piston rod 6, a piezo sensor 4 is incorporated between the rod 6 and the vehicle body 2. The piezo sensor 4 is composed of a laminated body of piezoelectric elements that polarizes according to the applied force. Since the current flowing through the electrode is equal to the differential amount of the polarization charge, a signal corresponding to the rate of change of the damping force is obtained. Reference numeral 26 in the figure denotes a sensor for detecting the traveling speed of the vehicle. The vehicle speed signal SP from the vehicle speed sensor 26 and the damping force change rate signal V from the piezo sensor 4 are input to the microcomputer system 32 via the I / O 34. The microcomputer system 32 constitutes part of the target damping force change rate extreme value indicating means A, the actual damping force change rate extreme value calculating means D, and the controller B, and includes an I / O 34, a RAM 36, a CPU 38, and a R.
The OM 40 and the I / O 42 are connected by a common bus 44.

The high voltage generating circuit 46 generates a DC voltage of 450 volts, and the switching circuit 48 applies 450 volts directly to the piezo actuator 8 or lowers the voltage according to a control signal from the microcomputer 32. 400, 350, 300, ~ 5,
The switching is performed in a state where 0 volt is applied or no voltage is applied. The switching circuit has 10 terminals, 450 V when the first terminal is turned on, 400 V when the second terminal is turned on, 50 V when the ninth terminal is turned on, and 10 V when the ninth terminal is turned on. When turned on, it applies zero volts. The first terminal turns on and
When 50 volts is applied, the vibration attenuator 20 is adjusted to the softest state (hereinafter referred to as level 1) as shown in FIG. When the tenth terminal is turned on and no voltage is applied, the vibration attenuator is adjusted to the hardest state (level 10) as shown in FIG. And this attenuator is 1
The damping force generation characteristics are switched in the zero stage.

Next, the target damping force change rate extreme value indicating means A will be described with reference to FIGS. In this embodiment, the target damping force change rate extreme value indicating means A is constituted by the microcomputer 32, and the microcomputer 32 calculates the target extreme value VT by executing the processing of FIG.
The process of FIG. 3 is programmed to be repeatedly executed in a T1 cycle (this is set in a unit of several seconds in which the vehicle speed can largely change). Step 100 is to read the signal SP of the vehicle speed sensor 26 first, and then to step 1
At 02, the target extreme value VT is searched. Where the target extreme value VT
As shown in FIG. 4, RO is previously associated with the vehicle speed SP.
The target extreme value VT stored in M40 is searched for and calculated. After execution of the above processing, the process returns to the main routine.

In this embodiment, the actual extreme value calculating means D is also constituted by the microcomputer 32, and the microcomputer 32 executes the processing of FIG.
Is calculated. The processing in FIG. 5 is programmed to be repeatedly executed at a cycle T2 set to several milliseconds.

Step 200 is to determine whether the damping force change rate signal V of the piezo sensor 4 is positive or negative. When the signal is negative, the extreme value VP is set to zero (step 224), and when the change rate V is increasing. Is set to a flag FF indicating "1" (step 226). As long as the value is negative, the process is once terminated.

If the damping force change rate V is positive, the read change rate V becomes positive and then compared with the maximum value VP up to the present (step 202). If it exceeds the maximum value up to the present, the maximum value VP is updated (step 220). On the other hand, if it is less than the maximum value VP, the step 220 is skipped. As a result, the maximum value after the damping force change rate V becomes positive is set to VP. Step 202
"Yes" corresponds to the case where the damping force change rate V is increasing, and in this case, 1 is set to the flag FF.

When the damping force change rate V is positive, and when the damping force change rate starts to decrease, step 202 becomes negative. At this time, the flag FF is set to zero in step 206. At this time, it is compared in step 204 whether or not the previous time was also falling. If the last time the vehicle is descending, the result of step 204 is negative (because the flag FF is zero at step 206 at the start of the downward movement), and the process is temporarily terminated. On the other hand, if the previous time was on the rise and the current time the first time it was falling, step 204 is YES. That is, the processing after step 206 is executed only immediately after the change rate V changes from rising to falling. At this time, the maximum value up to that point, that is, the extreme value VP is calculated.

Step 208 and subsequent steps are processing for adjusting the damping force generation characteristics. The microcomputer 32, the switching circuit 48, and the high voltage generation circuit 46 which execute this processing and this processing constitute the controller B. . Step 208 is to calculate the difference VD between the actual extreme value VP calculated in step 220 and the target extreme value VT calculated in step 102 in FIG. 3, and if the actual extreme value VP is greater, a positive value is obtained. If VD is lower than the actual extreme value VP, a negative VD is calculated. The positive VD is calculated when the actual extreme value is too large, and the attenuator needs to be adjusted to the soft side. On the other hand, when a negative VD is calculated, it is necessary to correct the attenuator to the hard side. This relationship is illustrated in FIG. 7, in which the vertical axis indicates the level correction amount ΔL. The level correction amount ΔL is set in accordance with the difference between the actual extreme value VP and the target extreme value VT such that the actual extreme value VP substantially matches the target extreme value VT. This relationship is mapped and stored in the ROM 40. In this embodiment, not only the damping force generation characteristic is simply corrected to the soft / hard side, but the larger the difference between the actual extreme value and the target extreme value is, the larger the correction is made, so that the characteristic approaches the target extreme value in a shorter time. The level correction amount ΔL is set. When the level correction amount ΔL is calculated in this way, the current level is corrected in step 212. Steps 214 to 218 are for securing the level L among 1 to 10.

With the above processing, the level of the damping force generation characteristic of the attenuator 20 is corrected, and the extreme value VP of the damping force change rate is corrected to the target extreme value VT. As a result, if the damping force generation characteristic is too hard compared to the road surface condition, it is adjusted to a moderately soft side, and if it is too soft, it is adjusted to a moderately hard side. It is adjusted to. Here, the adjustment of the damping force generation characteristic is performed with extremely high responsiveness as compared with the conventional learning method, and the adjustment function of the attenuator is utilized to the maximum.

In the above embodiment, the damping force generation characteristic of the attenuator can be switched in ten stages. However, the number of stages is not limited to ten, and two or more stages are stepless (continuous). What is necessary is just to be able to adjust the damping force generation characteristic. In addition, although the example in which the damping force generation characteristic is switched by the piezo actuator 8 is illustrated, the invention is not limited to this, and the damping force generation characteristic may be switched by a motor or a solenoid coil. In the present embodiment, the extreme value is calculated only on the positive side of the damping force change rate V. However, the magnitude of the target extreme value may be compared using the extreme value on the negative side.

Further, the damping force generation characteristic may be adjusted by using both the difference between the actual extreme value and the target extreme value on the positive side and the difference between the actual extreme value and the target extreme value on the negative side. In this case, the amplitude of the damping force change rate is actually compared with the target amplitude, and the damping force generation characteristic is adjusted according to the magnitude. In this embodiment, the four wheels are individually switched, but the damping force generation characteristics of the four wheels may be simultaneously adjusted so that the average actual extreme value of the four wheels becomes the target extreme value.

In this embodiment, since the damping force generation characteristic is adjusted not by the damping force itself but by the extreme value of the damping force change rate, it is excellent in suppressing the tilt. When tilting (spring resonance of the vehicle body) occurs, the damping force itself is in a state where a large value is generated. At this time, if the extreme value of the damping force is compared with the target extreme value, the characteristic of the damping force generation is switched to the soft side due to the occurrence of the tilt.

However, in this embodiment, since the extreme value of the rate of change is used, the extreme value is small for low-frequency vibrations such as tilting, so that it is not erroneously switched to software. For this reason, according to the present embodiment, switching is performed in an optimum manner with respect to actual vehicle behavior.

[0023]

According to the present invention, whether the damping force generation characteristic is too hard or too soft with respect to the actual road surface condition is immediately determined by comparing the actual extreme value VP and the target extreme value VT. Since the damping force generation characteristics are adjusted based on the determination result, the damping force generation characteristics can follow the current road surface condition with good responsiveness, and the ability of the attenuator capable of switching the damping force generation characteristics is improved. It will be used effectively. As a result, the attenuator is adjusted to a state in which both riding comfort and running stability are realized in a well-balanced manner.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the concept of the present invention.

FIG. 2 is a system configuration diagram of an embodiment.

FIG. 3 is a routine for calculating a target extreme value VT.

FIG. 4 is a diagram showing a relationship between a target extreme value and a vehicle speed;

FIG. 5 is a diagram showing a switching routine of a damping force generation characteristic.

FIG. 6 is a diagram illustrating a relationship between a damping force and a vibration speed generated in various damping force generation characteristics (levels 1 to 10).

FIG. 7 is a diagram showing a relationship between a difference VD between an actual extreme value VP and a target extreme value VT and a level correction amount.

[Explanation of symbols]

 A target damping force change rate extreme value indicating means B controller C damping force generation characteristic variable vibration damper D actual damping force change rate extreme value calculating means E damping force change rate detecting means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B60G 17/00-23/00 F16F 9/50

Claims (1)

(57) [Claims] 1. A variable damping force generation characteristic vibration damper having a variable force for damping vibration generated between a vehicle body and wheels, and a rate of change of the damping force generated by the variable damping force generation characteristic vibration damper. Damping force change rate detection means for outputting a signal (V) corresponding to the following equation: actual damping force change rate extreme value calculation for calculating an extreme value (VP) of the damping force change rate signal detected by the damping force change rate detection means Means, a target damping force change rate extreme value indicating means for indicating a target extreme value (VT), and an actual extreme value (V) calculated by an actual damping force change rate extreme value calculating means.
P) is compared with the target extreme value (VT) indicated by the target damping force change rate extreme value indicating means, and when the actual extreme value (VP) exceeds the target extreme value (VT), the damping force generation characteristic variable. When the actual extreme value (VP) is lower than the target extreme value (VT), the variable vibration damper is changed to the characteristic on the side that generates low damping force. And a controller that adjusts the characteristics of the suspension.