JP2910348B2 - 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 suspension control device for a vehicle provided with a vibration damper having a variable damping force generation characteristic, the function of adjusting the damping force generation characteristic being improved.

[0002]

2. Description of the Related Art In a vehicle provided with a vibration damper having a variable damping force generation characteristic, a 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 detection means exceeds the reference change rate (Vref) calculated by the reference change rate calculation means. Vehicles having a controller for switching the damper to a low damping force generating state have already been developed.

According to this vehicle, the damper is always in a state of generating a high damping force, and when vibration starts to occur, the state is switched to a state of generating a low damping force to reduce the vibration generated in the vehicle body. Further, a technology for learning and updating the reference change rate (Vref) in accordance with the road surface condition has been developed (Japanese Patent Laid-Open No. Hei 3-
No. 96414). In this technique, the learning change rate (Vref) is lower than the current reference change rate (Vref).
G) calculating means, and the detected damping force change rate (V)
Means for calculating a frequency at which the reference change rate exceeds the learning change rate (Vref G), and a reference change rate (Vref) based on the calculated frequency.
And a reference change rate learning means comprising means for learning and updating.

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, when the vehicle travels on a good road for a long time, the reference change rate (Vref) is learned and updated at a low level, and the attenuator can be switched to a low damping force generating state with 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. When a vehicle travels on a wet road surface, a phenomenon called hydroplaning may occur. When this phenomenon occurs, the contact force of the wheels is lost, and the damping force change rate (V) generated in the damper is in a very small state. According to the prior art, the learning of the reference change rate (Vref) is also progressing during this time, so that the reference change rate is rapidly learned and updated to a low value as in the case of traveling on a super-good road. . As a result, when or immediately after the hydroplaning phenomenon disappears and the wheel recovers the ground contact force, the reference change rate (Vref) becomes too low as compared with the actual road surface condition. Therefore, immediately after the hydroplaning phenomenon disappears, the state is switched to the low damping force generation state in response to the small vibration that does not need to be switched to the low damping force generation state. In an extreme case, the state is switched to a low damping force generation state by a slight vibration when the ground force is recovered. Therefore, in the present invention, the reference change rate (Vref) is determined by the occurrence of the hydroplaning phenomenon.
The purpose of the present invention is to develop a suspension control device that prevents erroneous learning of the vehicle and prevents erroneous switching after the hydroplaning phenomenon disappears.

[0006]

In order to solve the above-mentioned problems, a suspension control device whose concept is schematically shown in FIG. 1, that is, a damping force generation characteristic in which a force for damping vibration generated in a vehicle body is variable. Variable vibration damper F, damping force change rate detecting means E that outputs a signal corresponding to the change rate (V) of the damping force generated by the variable vibration damper F, and the current reference change Means C1 for calculating a learning change rate (Vref G) at a level lower than the rate (Vref), and the damping force change rate (V) detected by the damping force change rate detecting means E is used to calculate the learning change rate. A frequency calculating means C2 for calculating a frequency exceeding the learning change rate (Vref G) calculated by the means C1, and a reference change rate (Vref) is learned and updated based on the frequency calculated by the frequency calculating means C2. Reference change rate having means C3 The learning means C and the damping force change rate (V) detected by the damping force change rate detecting means E correspond to the reference change rate (V) learned and updated by the reference change rate learning means C.
ref), a controller D that switches the variable damping force generation characteristic variable vibration damper F to a low damping force generating state is used to determine whether or not the vehicle has a hydroplaning phenomenon. A suspension control device has been developed in which a means A for viewing and a means B for inhibiting the learning process of the reference change rate learning means C while the occurrence of the hydroplaning phenomenon is detected by the viewing means are added. . As the hydroplaning detecting means A, for example, the means described in JP-A-63-263159 can be used.

[0007]

According to the suspension control apparatus having the above configuration, while the hydroplaning detecting means A does not detect the occurrence of the hydroplaning phenomenon, the reference change rate (Vref) is changed to the road surface state in the same manner as in the prior art. Learned and updated accordingly. Therefore, the reference change rate (Vref
) Is adjusted to an appropriate value. When the occurrence of the hydroplaning phenomenon is detected by the hydroplaning detecting means A, the learning prohibiting means B operates to prohibit learning and updating of the reference change rate (Vref). Therefore, during the occurrence of the hydroplaning phenomenon, the reference change rate (Vref) is maintained at the value at the time of occurrence of the hydroplaning phenomenon. In this way, the reference change rate is prevented from being erroneously learned and updated to a low value during the occurrence of the hydroplaning phenomenon.

[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 has a piezoelectric element laminated body, a displacement enlarging mechanism, and a piston. When +500 volts is applied from a high voltage generating circuit 46 to be described later, the piezoelectric element laminated body expands and the sub flow path 10 Communication is made between the sixteen. In this state, the working fluid can flow between the upper piston chamber 12 and the lower chamber 18 via the sub-flow paths 10 and 16, so that the damping force generated by the damper 20 is small, that is, a so-called soft state.

On the other hand, when minus 100 volts is applied to the piezo actuator 8, the piezoelectric element laminate contracts and shuts off between the sub-flow paths 10 and 16. In this state,
Since the working fluid can flow only through the flow path 15, a state in which a large damping force is generated, that is, a so-called hard state. Note that, once the piezoelectric element laminate contracts, the contracted state continues even if the applied voltage is set to zero thereafter.

A piezo sensor 4 is incorporated between the rod 6 and the vehicle body 2 to detect the damping force generated in the damper 20, that is, the force acting on the piston rod 6. 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.

An example of an attenuator for varying the damping force generation characteristic using a piezo actuator 8 and an attenuator for obtaining a signal corresponding to a damping force change rate using a piezo sensor 4 are described in the Toyota Soarer new car manual, The details are described in May 1991 (issued by Toyota Motor Corporation), pp. 3-35-42.

In the drawing, reference numeral 30 denotes a stop lamp switch which is turned on while the brake is operated and the vehicle is being braked. In the figure, reference numeral 26 denotes a sensor for detecting the speed of the driven wheel (the front wheel in this embodiment). Brake signal from stop lamp switch 30, front wheel speed sensor 26
And the damping force change rate signal from the piezo sensor 4 are input to the microcomputer system 32 via the I / O 34. The microcomputer system 32 is a part of the hydroplaning detection means A,
It constitutes a part of the learning prohibiting means B, the reference change rate learning means C, and the controller D, and includes an I / O 34, a RAM 3
6, a CPU 38, a ROM 40, and an I / O 42 connected by a common bus 44.

The high voltage generating circuit 46 generates a voltage of 500 volts, and the switching circuit 48 applies a plus 500 volt to the piezo actuator 8 according to a control signal from the microcomputer 32,
The three states of applying minus 100 volts or not applying voltage are switched. Microcomputer 32, high voltage generation circuit 46, and switching circuit 48
Constitutes the controller D.

Next, a process of detecting a hydroplaning phenomenon performed by the microcomputer 32 will be described with reference to FIG. The processing in FIG. 3 is programmed to be repeatedly executed at short time intervals. In FIG. 3, step 50 is a step for initializing the clock counter CHP to zero. Thereafter, in step 52, the signal of the front wheel speed sensor 26 is read and recorded in the FS1. Step 54 is to increment the clock counter CHP by one, and step 56 is to repeat the loop of steps 54 and 56 once CHP after execution of step 52. After Step 52 is executed, Steps 54 and 56 are repeated once CHP, that is, when a predetermined time has elapsed, then, at Step 58, the signal of the front wheel speed sensor 26 is read again and stored in FS2.

In step 60, it is determined whether or not the signal of the stop lamp switch 30 is off. If the brake is operated, the result is "no", the hydroplaning is not detected, and the process is temporarily terminated. If the brake is not operated, the result is YES in step 60, and then the speed difference FS1-FS of the front wheels read in steps 52 and 58.
2, that is, the change width of the speed is compared with a predetermined value ΔFS.
Here, ΔFS is a value slightly larger than the maximum value of the change width of the driven wheel speed that can occur during the non-operation of the brake, that is, the maximum value of the deceleration width during the operation of the engine brake. It will not be. However, when the hydroplaning phenomenon occurs in the vehicle, the contact force of the driven wheel is lost, so that the force for rotating the driven wheel is not applied, and the driven wheel speed drops rapidly. For this reason, if hydroplaning occurs, step 62 becomes YES, and in this case, the flag FHP for determining the occurrence of hydroplaning is set to 1 (step 6).
4). Steps 62 and 64 are repeated while hydroplaning is occurring and the front wheel speed is decreasing. If hydroplaning continues for a long time and the speed of the front wheels is sufficiently reduced, step 62 starts to be negative. In this case, in step 66, it is determined whether or not the front wheels have recovered the contact force and the front wheel speed has started to increase. If the front wheel speed starts to increase, it is determined that the hydroplaning phenomenon has disappeared, and the flag FHP is set to zero (step 68). On the other hand, while the hydroplaning phenomenon continues, the flag FHP
Is maintained at 1 (step 68 is skipped).

By repeatedly executing the process of FIG. 3, flag FHP is set to 1 while hydroplaning is occurring, and flag FHP is set to zero when hydroplaning is not occurring. The occurrence of the hydroplaning phenomenon is detected in this manner, and the stop lamp switch 30, the front wheel speed sensor 26, and the microcomputer 32 involved in the execution of this processing constitute the hydroplaning detection means A.

FIG. 4 shows a control routine for switching the damping force generation characteristic, and this process is also repeatedly executed at short time intervals. In step 100, a process of reading the damping force change rate signal output from the piezo sensor 4 is performed. Step 110
Is the reference change rate Vre calculated as described below.
Compare with f. If the actual rate of change V exceeds the reference rate of change Vref, step 110 is affirmative, and a plus 500 volts is applied to the attenuator 20 to switch to soft (step 160). Here, the flag FHS for determining the soft / hard state of the attenuator 20 is set to 1 to indicate software (step 150), and the timer T is set to zero (step 140).

If the vibration is gradually damped by switching to the software, and the damping force change rate V begins to fall below the reference change rate Vref, the result in step 110 is NO. At this time, the flag FHS is referred to (step 120), and if it is 1 indicating a soft state, step 170 is executed next. In step 170, it is determined whether or not a predetermined time has elapsed after V <Vref. Unless the predetermined time has elapsed, step 170 becomes no and time is counted in step 180. During this time, the soft state is maintained. That is, +500 volts is continuously applied to the piezo actuator 8. When this loop is repeated TS times, that is, when the condition of V <Vref continues for TS times, step 170 becomes YES, and the attenuator 20 is switched to hardware with the flag FHS set to zero (steps 190 and 130). That is, a voltage of minus 100 volts is applied to the piezo actuator 8.

After the attenuator 20 has returned to the hard state in this way, if V <Vref, the result of step 110 is no, and the result of step 120 is no.
Hold hard. That is, the piezo actuator 8
Do not apply voltage to If V> Vref while the attenuator 20 is switched to hardware, the above-described soft switching process starting from step 140 is performed. In this manner, the attenuator 20 is switched to soft when V> Vref, and is returned to hard when the condition of V <Vref continues for a predetermined time. A controller D is constituted by the switching circuit 48, the high-voltage generation circuit 46, and the microcomputer 32 involved in the processing of FIG.

Next, the calculation and learning processing of the reference change rate will be described with reference to FIGS. First, FIG.
This is a process for detecting whether or not ref needs to be corrected, and is repeatedly executed at predetermined time intervals. Step 200 is a process for counting the number of executions of this process. In the next process of FIG. 6, every time C reaches i, C is cleared to zero. Step 210 is the attenuator 20
Is determined to be a high damping force generation state (hard and FHS = 0) or a low damping force generation state (soft and FHS = 1). If it is in the hard state, the result is NO, and in step 214, a learning reference rate Vref G at a level corresponding to 80% of the reference change rate Vref at that time is calculated. On the other hand, if it is in the soft state, a learning reference rate Vref G at a level corresponding to 40% of the reference change rate Vref at that time is calculated in step 212.

Next, at step 220, it is compared whether or not the currently detected damping force change rate V is equal to or higher than the learning reference rate VrefG. If V <Vref G, zero is set to the flag FF indicating that (step 230), and the process is temporarily terminated. When V> Vref G, it is then compared whether or not the flag FF is zero (step 240). Step 260
When V> Vref G, 1 is set in the flag FF.
<Vref G, and this time is when V> Vref G. If V> Vref G in the previous time, step 240 is negative. Therefore, the number of times that V <Vref G is changed to V> Vref G is counted as N incremented in step 250. That is, the number of times that the actual change rate V exceeds the learning reference rate Vref G is counted by N.

Step 199 is applied to this frequency detection processing. In this step 199, the process after step 200 is skipped while the flag FHP is set to 1 due to the occurrence of the hydroplaning phenomenon.
That is, step 199 serves to prohibit the counting of the frequency N during the occurrence of the hydroplaning phenomenon.

Next, the learning process of the reference change rate Vref shown in FIG. 6 will be described. In step 320, the processing in FIG.
The comparison is performed to determine whether or not the processing has been performed. If the processing has not been performed i times, the processing is temporarily terminated without correcting Vref. This process is for comparing whether or not a period sufficient to learn whether Vref needs to be corrected depending on the road surface condition has elapsed. If it is compared in step 320 that sufficient learning opportunities have been given, step 33
At 0, C is cleared to zero, and at step 410, N is cleared to zero, and the processing of FIG. 5 is restarted from the beginning.

In step 340, the current vehicle speed (SP) is read. In step 350, the reference reference change rate V stored in the ROM 40 in association with the vehicle speed in the relationship shown in FIG.
Calculate base. In step 360, the detected frequency N
And the difference ΔN between the target frequency Nref and the target frequency Nref. Step 37
At 0, the sign of the frequency difference ΔN is compared. Here, if the reference change rate Vref is too high compared to the road surface condition and the actual damping force change rate V is difficult to exceed the learning change rate VrefG, the frequency difference becomes negative. Is reduced by a predetermined amount (β). On the other hand, the reference change rate Vref is too low compared to the road surface condition, and the actual damping force change rate V is equal to the learning change rate Vre.
If fG is easily exceeded, the frequency becomes positive, and in step 380, the correction width ΔV of the reference change rate is increased by a predetermined amount (β). By this processing, if the good road continues, V <Vref G easily occurs, and the correction width ΔV becomes negative. On the other hand, if bad road continues, V
> Vref G and the correction width ΔV becomes positive. The reference reference change rate Vbase is corrected using the correction width ΔV calculated as described above, and is actually changed to step 1 in FIG.
The reference change rate Vref used in step 10 is determined.

When such a process is repeated, the reference change rate Vref gradually decreases while the vehicle is traveling on a good road, and when almost the optimum value, ΔV becomes close to zero, and the optimum value is maintained. It is being done. Step 310 is added in this learning process. In this processing, the execution of the learning / updating process of the reference change rate after step 320 is prohibited while hydroplaning occurs and the flag FHP is 1, and the learning is prohibited during the generation of hydroplaning by step 310. And the reference change rate V
ref is maintained at the value when hydroplaning occurred.

As can be understood from the above description, in this embodiment, the reference change rate learning means C and the learning prohibition means B are constituted by the microcomputer 32. That is, the learning rate-of-change calculating means C1 is constituted by the steps 212 and 214 in FIG. 5 and the microcomputer 32 executing the same, and the processing in FIG. 5 and the steps 320, 330 and 41 in FIG.
The frequency calculation means C2 is constituted by the processing of step S0 and the microcomputer 32 executing the processing. Further, the processing of steps 370, 380, 390, and 400 in FIG. Is configured. Further, the microcomputer 32 for executing the step 199 of FIG. 5 and the step 310 of FIG. 6 constitutes the learning inhibiting means B.

FIG. 7 is a diagram for explaining the operation obtained by this embodiment. Now, as shown in FIG. 7A, it is assumed that a hydroplaning phenomenon has occurred between times T1 and T2.
Then, the actual damping force change rate V becomes a very small value as exemplified in (b). Here, in the case of the conventional technique, the learning is continued even during the occurrence of hydroplaning.
ref rapidly decreases as indicated by "Vref follow".
Often, the minimum acceptable level of reference change is reached. Therefore, after the disappearance of the hydroplaning phenomenon, the attenuator 20 is switched to a low damping force generating state (soft) with a small vibration as shown at time T3. On the other hand, according to the present embodiment, since the learning of the reference change rate is prohibited during the occurrence of the hydroplaning phenomenon, the value of the reference change rate is set at the time of occurrence of the hydroplaning as shown by "Vref" in the figure. The value is maintained at the value, and it is not accidentally switched to the low damping force generation state after the disappearance of the hydroplaning.

In this embodiment, the occurrence of the hydroplaning phenomenon is detected from the change in the speed of the driven wheel. However, this is merely an example. For example, the occurrence of the hydroplaning phenomenon is determined from the speed difference between the drive wheel and the driven wheel. You may make it detect. Further, the processing for learning described here is merely an example, and various learning methods such as a method based on the time frequency of V> VrefG and a method in which Vref does not depend on the vehicle speed may be used.

[0030]

According to the present invention, since the learning of the reference change rate is prohibited during the occurrence of the hydroplaning phenomenon, the reference change rate is not learned to an abnormally small value during the hydroplaning phenomenon. It is possible to prevent an inconvenience in switching between hardware and software after the disappearance of the hydroplaning phenomenon.

[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 hydroplaning detection routine.

FIG. 4 is a damping force generation characteristic switching control routine.

FIG. 5 is a frequency detection interrupt routine.

FIG. 6 is a reference change rate learning routine.

FIG. 7 is a diagram showing an operation of the present embodiment in comparison with a conventional example.

FIG. 8 is a diagram showing a relationship between a vehicle speed and a reference reference change rate.

[Explanation of symbols]

 A hydroplaning detection means B learning inhibition means C reference change rate (Vref) learning means C1 learning change rate (Vref G) calculation means C2 frequency calculation means C3 reference change rate (Vref) learning / update means D controller E damping force change Rate (V) detecting means F Variable damping force generation characteristic variable vibration damper

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

Claims (1)

(57) [Claims] 1. A variable damping force generation characteristic vibration damper having a variable force for damping vibration generated in a vehicle body, and a rate of change (V) of a damping force generated by the variable damping force generation characteristic vibration damper. , A means for calculating a learning change rate (Vref G) at a level lower than the current reference change rate (Vref), and a damping force change rate detecting means. The changed damping force change rate (V) is the learning change rate (Vref) calculated by the learning change rate calculating means.
G) and a reference change rate (Vre) based on the frequency calculated by the frequency calculation means.
f) learning / updating means for learning / updating the reference change rate, wherein the damping force change rate (V) detected by the damping force change rate detecting means is a reference change learned / updated by the reference change rate learning means. A controller for switching the variable damping force generation characteristic variable type vibration damper to a low damping force generation state when the ratio (Vref) is exceeded. And a means for prohibiting the learning process of the reference change rate learning means while the occurrence of the hydroplaning phenomenon is detected by the viewing means.