JPH0829657B2 - Suspension control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a suspension control device, and more specifically, to a state of vibration generated in a vehicle due to a change in a road surface, and a shock based on the detected state of vibration. The present invention relates to a suspension control device that changes a damping force characteristic of an absorber and controls vehicle body vibration.

[Prior Art] As a device for preventing the vibration of the vehicle, that is, the "flapping" of the vehicle, that is, the cycle is relatively long such as about 1 second, which is disclosed in JP-A-62-80111. There is a suspension controller. This suspension controller
When the tilt of the vehicle is detected by monitoring changes in vehicle height, and when tilt is detected, the tilt is prevented by setting the damping force generation pattern of the shock absorber to the high damping force side and making the suspension hard. Met.
To detect tilt from vehicle height change, the frequency of vehicle height change is a frequency near the sprung resonance frequency (around 1.0 [Hz]), and the magnitude of vehicle height change exceeds a preset threshold value. At that time, it was determined that the vehicle had a sickness.

[Problems to be Solved by the Invention] Although the above configuration is excellent for preventing vehicle tilt, there is a problem that tilt prevention may be incomplete depending on running conditions such as the number of passengers and the load capacity. It was For example, if the average vehicle height or the pattern of vehicle height changes significantly due to changes in the number of passengers or the loading capacity in the driving conditions, the difference between the vehicle height change value and a predetermined threshold value is reduced or expanded as a whole. As a result, it is conceivable that a small change in vehicle height may be judged as a tilt, or an erroneous judgment may not be made even if a large tilt occurs, which may reduce the accuracy of the tilt detection, resulting in incomplete prevention of the tilt. It was

Also, even if the damping force pattern generated by the shock absorber itself changes over time, and the vehicle height change pattern also changes, the difference between the vehicle height change value and the threshold value decreases or increases overall. As a result, erroneous determination may occur and the accuracy of the tilt detection may decrease, resulting in incomplete prevention of the tilt.

An object of the suspension control device of the present invention is to solve the above-mentioned problems and to realize accurate flapping prevention by compensating for changes in running conditions such as the number of passengers and changes over time.

Configuration of the Invention The configuration of the present invention that achieves the above object will be described below.

[Means for Solving the Problem] As illustrated in FIG. 1, the suspension control device of the present invention includes a vibration state detecting means M1 for detecting a vibration state generated in a vehicle due to a change in a road surface, and the detected vibration state M1. From the vibration state of the vehicle, the sprung resonance component extracting means M3 for extracting a frequency component near the sprung resonance frequency among the vibration components, and the magnitude of the extracted sprung resonance component on the extension side threshold value or the contraction side. In a suspension control device including a high damping force maintaining means M4 for maintaining a high level of the damping force of the shock absorber M2 when the threshold value is exceeded, when the vehicle is in a sprung vibration state near the sprung resonance frequency, The frequencies at which the magnitude of the extracted sprung mass resonance component exceeds the extension side threshold value or the contraction side threshold value are compared, and the extension is performed on the side where both the frequencies are about the same. Threshold correction means for correcting side threshold value and contraction side threshold value
It is characterized by having M5 and.

[Operation] In the suspension control device of the present invention having the above-described configuration, the state of vibration generated in the vehicle due to the change of the road surface is detected by the vibration state detection means M1, and the detected vehicle vibration state (for example, vehicle height change, From the change in the damping force generated by the shock absorber M2 when the vehicle height changes), a frequency component near the sprung resonance frequency, which is the tilt component of the vehicle, of the vibration component is extracted by the sprung resonance component extraction means M3. . If the magnitude of the extracted sprung resonance component exceeds the extension side threshold value or the contraction side threshold value, the high damping force maintaining means M4 determines that the vehicle tilt has been detected, and determines the degree of the damping force of the shock absorber M2. Keep it high to prevent tilting. The expansion side threshold value and the contraction side threshold value are corrected by the threshold value correction means M5. The correction is that when the vehicle is in a sprung vibration state near the sprung resonance frequency, the frequency at which the magnitude of the sprung resonance component exceeds the extension side threshold value or the contraction side threshold value is compared. It is done on the degree side. In this way, correction is performed to maintain a predetermined relationship between the vibration state of the vehicle and the expansion-side threshold value and the contraction-side threshold value when the vehicle is in the sprung vibration state near the sprung resonance frequency. As a result, even if driving conditions such as the number of passengers and the load capacity change and the vibration state of the vehicle changes, the change is compensated by the correction of the threshold value, and the high damping force maintaining means M4 can detect the tilt well. Go to and perform accurate vehicle tilt prevention.

[Embodiment] In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of the suspension control device of the present invention will be described below.

FIG. 2 is a schematic configuration diagram showing the overall configuration of the suspension control device 1, FIG. 3 (A) is a sectional view in which the shock absorber is partially broken, and FIG. 3 (B) is a schematic view of the shock absorber. FIG.

As shown in FIG. 2, the suspension control device 1 of the present embodiment has a shock absorber 2FL, 2FR, which can change the damping force in two steps.
2RL and 2RR, and an electronic control unit 4 connected to each of these shock absorbers and controlling the damping force thereof. Each shock absorber 2FL, 2FR, 2RL, 2RR is
Between the left and right front and rear wheels 5FL, 5FR, 5RL, 5RR suspension lower arms 6FL, 6FR, 6RL, 6RR and the vehicle body 7, the coil springs 8FL, 8FR, 8RL, 8RR are installed side by side.

The shock absorbers 2FL, 2FR, 2RL, 2RR are, as described later, a piezo load sensor that detects the force acting on the shock absorbers 2FL, 2FR, 2RL, 2RR, and a shock absorber.
Each of the 2FL, 2FR, 2RL and 2RR has a built-in piezo actuator that switches the setting of the generation pattern of the damping force with respect to the stroke.

Next, the structure of each of the shock absorbers 2FL, 2FR, 2RL, 2RR will be described. The above shock absorbers 2FL, 2FR,
Since the structures of 2RL and 2RR are all the same, here the left front wheel 5
Take the shock absorber 2FL on the FL side as an example. Further, in the following description, reference numerals of the respective members provided on the respective wheels indicate, as necessary, the left front wheel 5FL, the right front wheel 5FR, the left rear wheel 5RL,
The subscripts FL, FR, RL, RR corresponding to the right rear wheel 5RR shall be added, and the subscripts shall be omitted when there is no difference between the respective wheels.

As shown in FIG. 3 (A), the shock absorber 2 is fixed to the suspension lower arm 6 (FIG. 2) via the wheel side member 11a at the lower end on the cylinder 11 side, while being inserted into the cylinder 11. The upper end of the rod 13 is fixed to the vehicle body 7 together with the coil spring 8 via the bearing 7a and the vibration-proof rubber 7.

Inside the cylinder 11, an internal cylinder 15, a connecting member 16, and a cylindrical member 17 connected to the lower end of the rod 13, and a main piston 18 slidable along the inner peripheral surface of the cylinder 11 are provided. . A piezo load sensor 25 and a piezo actuator 27 are housed in the internal cylinder 15 connected to the rod 13 of the shock absorber 2.

The main piston 18 is externally fitted to the tubular member 17,
A seal member 19 is interposed on the outer periphery fitted to the cylinder 11. Therefore, inside the cylinder 11, the main piston 18
Is divided into a first liquid chamber 21 and a second liquid chamber 23. As shown in FIG. 3 (B), a backup member 28 is screwed to the distal end of the cylindrical member 17, and a spacer 29 and a leaf valve 30 are formed between the cylindrical member 17 together with the main piston 18. The leaf valve 31 and the collar 32 are pressed and fixed to the backup member 28 on the side of the member 17 respectively.
Further, a main piston 34 and a spring 35 are interposed between the leaf valve 31 and the backup member 28 and urge the leaf valve 31 and the main piston 18 in the direction.

When the main piston 18 is stopped, the leaf valves 30 and 31 close the expansion side passage 18a and the contraction side passage 18b provided on the main piston 18 on one side, and the main piston 18 indicates the arrow. It opens to one side as it moves in the A or B direction. Therefore, the hydraulic oil filled in both liquid chambers 21 and 23 moves between both liquid chambers 21 and 23 through either of the passages 18a and 18b as the main piston 18 moves. In this way, when the movement of the hydraulic oil between the liquid chambers 21 and 23 is limited to the passages 18a and 18b, the damping force generated with respect to the movement of the rod 13 is large, and the suspension characteristic becomes hard. .

Stored inside the internal cylinder 15 Piezo load sensor 25
The piezo actuator 27 is shown in FIGS. 3 (A) and (B).
As shown in, an electrostrictive element laminated body is formed by laminating piezoelectric ceramic thin plates with electrodes sandwiched therebetween. Each electrostrictive element of the piezoelectric load sensor 25 is polarized by the force acting on the shock absorber 2, that is, the damping force. Therefore, the piezo load sensor
If the output of 25 is taken out as a voltage signal by a circuit having a predetermined impedance, the rate of change of damping force can be detected.

The piezo actuator 27 is formed by stacking electrostrictive elements that expand and contract with good response when a high voltage is applied to increase the expansion and contraction amount, and directly drives the piston 36. When the piston 36 is moved in the direction of arrow B in FIG. 3 (B), the plunger 37 and the spool 41 having an H-shaped cross section are also moved in the same direction via the hydraulic oil in the oil tight chamber 33. Thus, the spool 41 at the position (origin position) shown in FIG.
Moves in the direction B in the figure, the sub-flow passage 16c connected to the first liquid chamber 21 and the sub-flow passage 3 of the bush 39 connected to the second liquid chamber 23.
It will be connected to 9b. The sub-flow passage 39b is further communicated with the flow passage 17a in the tubular member 17 through an oil hole 45a provided in the plate valve 45, so that the spool 41
Moves in the direction of arrow B, as a result, the flow rate of the hydraulic oil flowing between the first liquid chamber 21 and the second liquid chamber 23 increases.
In other words, the shock absorber 2 switches its damping force characteristic from the state of large damping force (hard) to the side of small damping force (soft) when the piezo actuator 27 expands due to the application of a high voltage, and when the charge is discharged and contracts, the damping occurs. Restores the force characteristics to the state of high damping force (hard).

The amount of movement of the leaf valve 31 provided on the lower surface of the main piston 18 is regulated by the spring 35 as compared with the leaf valve 30. Also, the plate valve 45 has an oil hole.
An oil hole 45b having a larger diameter than 45a is provided outside the oil hole 45a, and when the plate valve 45 moves in the direction of the bush 39 against the urging force of the spring 46, the hydraulic oil passes through the oil hole 45b. Can be moved. Therefore, regardless of the position of the spool 41, the hydraulic oil flow rate when the main piston 18 moves in the arrow B direction becomes larger than when the main piston 18 moves in the arrow A direction. That is, the damping force is changed depending on the moving direction (expansion side and contraction side) of the main piston 18 to further improve the characteristics of the shock absorber. A hydraulic oil supply passage 38 is provided between the oil tight chamber 33 and the first liquid chamber 21 together with a check valve 38a to keep the hydraulic oil flow rate in the oil tight chamber 33 constant.

Next, regarding the electronic control unit 4 for switching and controlling the generation pattern of the damping force of the shock absorber 2
This will be described with reference to the drawings.

The electronic control unit 4 includes, as sensors for detecting the traveling state of the vehicle, a piezo load sensor 25 of each shock absorber 2, a steering sensor 50 for detecting a steering angle of a steering wheel (not shown), and a traveling speed of the vehicle. A vehicle speed sensor 51 for detecting a shift position, a shift position sensor 52 for detecting a shift position of a transmission (not shown), a stop lamp switch 53 for issuing a signal when a brake pedal (not shown) is depressed, and the like are connected.

The electronic control unit 4 that outputs a control signal to the above-described piezo actuator 27 based on these detection signals is well known.
The CPU 4a, the ROM 4b, and the RAM 4c are mainly configured as an arithmetic logic operation circuit, and an input unit 4e and an output unit 4f which are connected to each other via a common bus 4d perform input / output with the outside.

In addition to the electronic control unit 4, a damping force detection circuit 54 to which the piezo load sensor 25 is connected, and a low pass filter 55 as a band pass filter to which the damping force detection circuit 54 is connected.
A waveform shaping circuit 57 to which the high-pass filter 56, the steering sensor 50 and the vehicle speed sensor 51 are connected, a high voltage applying circuit 58 connected to the piezo actuator 27, and a power supply from a battery 61 via an ignition switch 63. A so-called switching regulator type high voltage power supply circuit 62 that outputs a driving voltage for driving, a constant voltage power supply circuit 64 that transforms the voltage of the battery 61 to generate an operating voltage (5v) of the electronic control unit 4 and the like are provided. There is. Of the above configuration, the damping force detection circuit 54, the high-pass filter 56, the waveform shaping circuit 57, the shift position sensor 52, the stop lamp switch 53 are output to the input section 4e, while the high voltage application circuit 58 and the high voltage power supply circuit 62 are output. It is connected to each part 4f.

Damping force detection circuit 54 is for each piezo load sensor 25FL, 25FR, 25
It consists of four detection circuits provided corresponding to RL and 25RR, each of which detects the shock absorber 2 from the road surface.
The voltage signal output from the circuit including the piezo load sensor 25 according to the acting force received by the
In addition to outputting to the CPU 4a, a signal obtained by integrating this voltage signal is output to the CPU 4a and the low pass filter 55 as a damping force detection signal. The components that have passed through the low-pass filter 55 and the high-pass filter 56 are output to the CPU 4a.

Of the damping force detection signals output from the damping force detection circuit 54, in the embodiment, the damping force detection signals of the shock absorbers 2RL and 2RR of the left and right rear wheels 5RL and 5RR are output to the low pass filter 55.

The low pass filter 55 of the embodiment passes a signal having a frequency of about 1.3 [Hz] or less. On the other hand, the high pass filter 56 passes a signal having a frequency of about 1.0 [Hz] or higher. Therefore, when the damping force detection signal output from the damping force detection circuit 54 passes through the low-pass filter 55 and the high-pass filter 56, a spring having a frequency of 1.0 [Hz] or more and a frequency of 1.3 [Hz] or less is included in the components of the damping force detection signal. A sprung resonance component signal, which is a signal having a frequency near the upper resonance frequency, is extracted. An example of the sprung resonance component signal thus obtained is shown in the graph of FIG.

The CPU 4a of the electronic control unit 4 uses the various detection signals described above, for example, the damping force change rate detection signal and the damping force detection signal output from the damping force detection circuit 54, the sprung resonance component that has passed through the low-pass filter 55 and the high-pass filter 56. signal,
Based on the output signal from the waveform shaping circuit 57 that waveform-shapes and outputs the detection signal of the vehicle speed sensor 51 or the like to a signal suitable for processing in the CPU 4a, and further based on the processing result of itself, the road surface state, the running state of the vehicle, etc. Can be determined. CPU4a
Outputs a control signal to the high voltage application circuit 58 provided corresponding to each wheel based on such a determination.

The high voltage application circuit 58 is a circuit that applies the voltage of +500 V or −100 V output from the high voltage power supply circuit 62 to the piezo actuator 27 according to a control signal from the CPU 4a. Accordingly, the damping force switching signal causes the piezo actuator 27 to expand (when +500 V is applied) or contract (when -100 V is applied), and the hydraulic oil flow rate is switched, so that the damping force characteristic of the shock absorber 2 is soft or hard. Is switched to. That is, the damping force characteristic of each shock absorber 2 is such that when the high voltage is applied to extend the piezo actuator 27, the first shock absorber 2 inside the shock absorber 2 is caused by the spool 41 (FIG. 3 (B)) described above. When the flow rate of the hydraulic fluid flowing between the liquid chamber 21 and the second liquid chamber 23 increases, the damping force becomes small, and when the piezo actuator 27 is contracted by discharging the electric charge by the negative voltage, the operation is performed. Since the oil flow rate decreases, the damping force becomes large.

Next, the damping force control performed by the electronic control unit 4 of the suspension control unit 1 of the present embodiment having the above-mentioned configuration will be described based on the flowcharts of FIGS. 6, 7, and 8. Each routine shown in each figure is repeatedly executed by an interruption process at predetermined fixed time intervals. The processing contents of each routine are as follows.

Damping Force Control Routine (Fig. 6) Normally, damping force control for switching the setting of the damping force generation pattern of the shock absorber 2 according to the road surface condition is performed.
When the start condition for the tilt prevention is satisfied, the setting of the shock absorbers 2 of all four wheels is switched to a high damping force generation pattern in preference to this damping force control, and the tilt is prevented by making the suspension hard. . Further, when the ending condition of the tilt prevention is satisfied, the execution of the tilt prevention is ended and the damping force control is returned to the road surface condition.

Anti-rotation control routine (FIGS. 7 (A) and (B)) The sprung resonance component signal that has passed through the low-pass filter 55 and the high-pass filter 56 remains outside the range of the extension side threshold value and the contraction side threshold value. After a lapse of a predetermined time, it is determined that the start condition of the tilt prevention execution is satisfied, because it is a sign of the tilt occurrence. Further, during the execution of the tilt prevention, it is determined that the ending condition of the tilt prevention execution is satisfied when a predetermined time elapses while the sprung mass resonance component signal remains within another threshold range.

Threshold correction routine (Fig. 8) In the tilt prevention control routine, the number of times the sprung resonance component signal deviates from the expansion side threshold value and the condition for starting the tilt prevention is satisfied, and the sprung resonance component signal contracts. Compared with the number of times that the start condition was satisfied after deviating from the threshold,
The threshold value on the extension side and the threshold value on the contraction side are corrected so that the number of times is approximately the same.

In the embodiment, the swing prevention control routine and the threshold value correction routine are independently performed for the shock absorbers 2RL, 2RR of the left and right rear wheels 5RL, 5RR.

Hereinafter, the details of each routine will be described in order from the damping force control routine (FIG. 6).

When the damping force control routine is started, it is first determined whether or not the hardware priority switching flag HF is set to the value 1 (step 100). The hardware priority switching flag HF is a flag that is set to a value of 1 in step 130, which will be described later, when the conditions for starting the anti-sway prevention are satisfied in the anti-sway control routine (FIG. 7).

If the hardware priority switching flag HF is not value 1 (step
100) performs a normal damping force control process (step 110) based on the road surface condition. The outline of the damping force control processing is to judge the traveling state (steering angle, vehicle speed, etc.) based on the detection signals from various sensors, and to determine the damping force change rate detection signal and the damping force detection signal from the damping force detection circuit 54. The road surface condition is judged, and the high and low settings of the damping force generation pattern of the shock absorber 2 are switched according to the results of these judgments.
It means making the suspension soft or hard. Generally speaking, if the condition of the road surface is bad, it is made soft, and if the road surface is flat, it is made hard.

After the damping force control process (step 110), the tilt prevention control routine (FIG. 7) independently performed for the left and right wheels 5RL and 5RR each time this routine is repeated,
It is determined whether or not one of the right and left tilt prevention start flags SF R and SF L is set to the value 1 (step 12).
0). The left and right tilt prevention start flags SF R, SF L are set to the value 1 when the start conditions for the tilt prevention execution are satisfied in the respective tilt prevention control routines. If one of the tilt prevention start flags SF R and SF L is also set (step 120), the above-mentioned hardware priority switching flag HF is set to the value 1 (step 130) and this routine is once terminated.

On the other hand, when the hardware priority switching flag HF has a value of 1 (step 100), the swing prevention execution process (step 140) is performed. In the tilting prevention execution process, a process of setting the shock absorbers 2 of all four wheels to a high damping force generation pattern is performed prior to the result of the normal damping force control process (step 110) based on the road surface condition, If the suspension is soft, switch to hard; if it is hard, keep it hard.

After the tilt-prevention execution process (step 140), it is determined whether or not both the end flags EF R and EF L are set to the value 1 in the left-right tilt-prevention control routine (FIG. 7) (step 150). . Both end flags EF R, EF L
Is set to the value 1 (step 150), it is considered that the occurrence of the flapping has been eliminated, and the above hardware priority switching flag HF is reset to the value 0 (step 160), and this processing is temporarily terminated. In this way, when the hardware priority switching flag HF is reset to the value 0, in the next routine execution,
Normal damping force control processing based on the road surface condition (Step 11
0) is performed, and if the road surface is in poor condition, the suspension is softened, and if the road surface is flat, the suspension is hardened.

Next, the start flag SF R, SF L and the end flag EF R, EF L of the tilt prevention referred to in the damping force control routine are referred to.
A tilt prevention control routine for determining the value of is described with reference to the flowcharts of FIGS. 7 (A) and 7 (B).
Although the tilt prevention control routine is independently performed for the left and right wheels 5RL and 5RR, the processing for each wheel is the same, and therefore will be described without distinction.

When this routine is started, as shown in FIG. 7 (A), is the hardware priority switching flag HF set to the value 1 after reading the damping force data P constituting the sprung mass resonance component signal (step 200)? It is determined whether or not (step 210). When the hardware priority switching flag HF is not set to the value 1 (step 210), the normal damping force control according to the road surface condition is being performed, and the step 22
The processing for determining the start condition of the tilt prevention execution shown after 0 is executed. On the other hand, when the hardware priority switch flag HF is set to the value 1 (step 210), the tilt prevention is being executed, and the end condition for the tilt prevention execution shown in FIG. 7B is determined. Shift to the processing that does.

When the determination process of the start condition is started, first, it is determined whether the suspension is soft or hard (step 220), each threshold value set according to the soft or hard and the damping force data P previously read (step 200). ) Is determined (steps 230 and 240).
That is, in the soft setting, whether the damping force data P is higher than the expansion side threshold value + SL1 or lower than the contraction side threshold value -SL2, or the expansion side threshold value + SL1 and the contraction side threshold value. -Determine whether it is within the range of SL2 (step 230). In the hard setting, whether the damping force data P exceeds the extension side threshold + SL3,
It is determined whether it is below the contraction side threshold −SL4 or is within the range between the expansion side threshold value + SL3 and the contraction side threshold value −SL4 (step 240). For example, in the example in which the suspension shown in FIG. 5 is initially set to soft, the damping force data P is within the range of the extension side threshold value + SL1 and the compression side threshold value −SL2 before time t1. Judgment is made, and it is judged that it exceeds + SL1 at time t1.

The absolute values of the expansion thresholds + SL1 (soft) and + SL3 (hard) are set to values that are relatively larger than the absolute values of the contraction thresholds -SL2 (soft) and -SL4 (hard), respectively. Has been done. This is to compensate for the difference in the damping force generation pattern between when the shock absorber 2 expands and when it contracts. In addition, the absolute value of the threshold value for hardware + SL3, -SL4 is the threshold value for software + SL1,
− It is determined to be relatively larger than the absolute value of SL2. This is for compensating that the level of the damping force generated while the vehicle is running is higher in the hard setting than in the soft setting even on the same road surface.

As described above, as a result of judging the magnitude relationship between the damping force data P and the respective threshold values according to the soft and hard settings of the suspension, the damping force data P is the extension side threshold value + SL1 and the contraction side threshold value −SL1. If it is within the range of SL2 (soft), or expansion threshold + SL3 and compression threshold -S
If it is within the range of L4 (hard), it is considered that the precursor of the tilt occurrence is not detected, and after resetting the timer t1 which determines whether it is the precursor of the tilt occurrence described later (step
250), the tilt prevention start flag SF is reset to a value of 0 (step 260), the process returns to return and this routine is once terminated.

On the other hand, the damping force data P is the extension side threshold value + SL
If it is out of 1 (soft) and + SL3 (hard),
After setting the value 1 to the discrimination flag DF indicating that the damping force data P has deviated from the extension side thresholds + SL1, + SL3 (step 250), it is possible that the sign of the occurrence of the tilt is caught. A timer t1 for judging whether it is a sign of occurrence, that is, for judging whether the state in which the damping force data P deviates from the extension side threshold values + SL1, + SL3 continues for a predetermined period is incremented (step 260).

On the other hand, when the damping force data P is out of the contraction side threshold values -SL2 (soft) and -SL4 (hard), it is determined that the damping force data P is out of the expansion side threshold values + SL1, + SL3. After resetting the flag DF to the value 0, (step
290), a timer for determining whether or not the state where the damping force data P deviates from the shrinking side thresholds −SL2, −SL4 for a predetermined period of time on the assumption that there is a possibility of catching the occurrence of tilting.
Start t1 (step 280).

If you started timer t1, then
It is determined whether t1 has counted the determination period ΔTS (step 300).

While the timer t1 does not measure the determination period ΔTS (step 320), it is determined that the precursor of the tilting is not detected, and the tilting prevention start flag SF is reset to the value 0 (step 26).
0), exit to return and end this routine once.
For example, if the damping force data P once deviates from the range delimited by the respective thresholds but immediately falls within the range of the thresholds, the timer t1 is incremented (step 28).
0), immediately reset (step 250), judgment period Δ
Do not time TS.

When the timer t1 measures the judgment period ΔTS (step 30
In (0), the value 1 is set to the tilt prevention start flag HF on the assumption that the sign of the tilt occurrence has been detected (step 31).
0). Next, it is determined whether or not the determination flag DF is the value 1 (step 320), and if the value is 1, the damping force data P deviates from the extension side threshold values + SL1 (soft) and + SL3 (hard). Assuming that the tilt prevention start flag SF has been set, a process of adding 1 to the extension counter C1 that counts the total number of times (step 330) is performed. On the other hand, if the determination flag DF is not the value 1, the damping force data P is the shrinking side threshold value -SL.
If the tilt prevention start flag SF is set outside 2 (software) and -SL4 (hardware), the value 1 is added to the contraction side counter C2 that counts the total number of times (step 34).
Perform 0).

For example, in the example of FIG. 5, the damping force data P continuously exceeds the extension side threshold value + SL1 after the time t1, and in the tilt prevention control routine executed after the time t1, the damping force data It is continuously determined that the force data P is equal to or more than the extension side threshold value + SL1 (step 230). Therefore, the timer t1 is not reset but is incremented one after another (step 280), the determination period ΔTS is measured at the time t2, and it is determined that the sign of the tilt is caught, and the tilt prevention start flag SF is set to the value 1. (Step 310). In this case, since the damping force data P deviates from the extension side threshold value + SL1 and the tilting prevention start condition is satisfied, the value 1 is added to the counter C1 (step 330).

When the flapping prevention start flag SF is set to the value 1 (step 340) as described above, the hardware priority switching flag is set in the damping force control routine (FIG. 6) as described above.
HF is set to a value of 1 (step 130), and a tilt-prevention execution position process (step 140) for switching the setting of the damping force of the shock absorbers 2 of all four wheels to a high damping force is executed.

In the determination process of the start condition, the damping force data P
The reason why the range of each threshold value continuously deviates during the determination period ΔTs is added to the satisfaction condition for the start of the tilt prevention in order to supplement the characteristics of the low-pass filter 55, for example. Due to its characteristic, the low-pass filter 55 passes some high-frequency components unrelated to the tilt, but it is a requirement that the damping force data P be continuously out of the threshold range during the determination period ΔTs. By doing so, the misjudgment caused by the high frequency component falling immediately can be eliminated. Further, the determination period ΔTs is provided in order to slightly delay the timing of switching the suspension to the hard state and optimize the timing sensuously. In the case where the suspension is switched between two stages, soft and hard, like the device of this embodiment, the reason why the driver becomes hard if the precursor is caught before the occurrence of the tilt and the soft is switched to the hard This is because there is a risk of uncomfortableness and a sense of discomfort. It should be noted that the determination period ΔTs for such a purpose is a minute time as compared with the period of the vehicle tilting.

Next, the process of determining the end condition in FIG. 7B will be described.

In this judgment processing, first, it is judged whether or not the damping force data P is within the range of the extension side threshold value + SL5 and the contraction side threshold value -SL4 (see FIG. 5) (step 40).
0) is executed. Damping force data P is threshold value + SL5, -SL6
If it is out of the range, it is considered that the execution of the tilt prevention has ended, and the tilt of the vehicle occurs, and the timer t2 for measuring the judgment period ΔTe of the ending condition described later is reset (step 410), and the tilt prevention ends. The process of resetting the flag EF (step 420) is performed, and the present process is temporarily terminated.

On the other hand, when the damping force data P is within the range of the threshold values + SL5 and −SL6 (step 400), the damping force is small (in FIG. 5, for example, after time t3, time t5.
After that, since the end condition may be satisfied, the timer t2 that counts the determination period ΔTe is incremented (step 340), and it is determined whether the incremented timer t2 has counted the determination period ΔTe. Processing (step
440).

The timer t2 successively detects that the damping force data P is within the range delimited by the threshold values + SL5 and −SL6 (step 400) each time the tilt prevention control routine is repeated. Increment to (step 430)
Then, the determination period ΔTe is measured. For example, in the processing performed after time t3 shown in FIG. 5, since the damping force data P is within the threshold range, the timer t2 continues to count time, but at time t4, the damping force data P changes. Since it is out of the range, the timer t2 is reset (step 410) and the determination period ΔTS is not timed. In this way, when the timer t2 does not measure the judgment period ΔTS, it is considered that the tilt prevention may have ended and the tilt flag may be generated.
After the execution of the EF reset processing (step 420), the processing is temporarily terminated. In the damping force control routine (FIG. 6), the swing prevention execution process (step 140) is continuously executed.

On the other hand, in the processing performed after the time t5 shown in FIG. 5, the damping force data P continues to fall within the range of the threshold values + SL5 and −SL6, so the timer t2 measures the determination period ΔTS ( Step). Therefore, the timer t2 is
At the time t6 when the time of TS is measured, the end flag EF is set to the value 1 on the assumption that there is no occurrence of flapping even after the flapping prevention is finished (step 360).

As described above, when the prevention end flag EF of both routines is set in the swing prevention interrupt routine independently performed for the left and right rear wheels 5RL and 5RR, as described above, the damping force control routine (6th In the figure, the hardware priority switching flag HF is reset (steps 150 and 16).
0). After that, in the damping force control routine, the damping force control process (step 110) based on the normal road surface condition is performed, and if the road condition is bad, the suspension is made soft, and if the road surface is flat, it is made hard. In the example of FIG. 5, time t6
The end condition determination period ΔTe is timed, and the suspension is softened or hardened depending on the road surface condition.

The end condition determination period ΔTe guarantees that the damping force data P is within the threshold value + SL3, -SL4 range, and is longer than the period of vibration near the sprung resonance frequency. Is set. Further, the determination period ΔTe defines the minimum execution period of the tilt prevention, and is set to a period in which the effect of the tilt prevention is effectively obtained.

Next, the expansion-side threshold values + SL1 (soft) and + SL3 (hard) and the contraction-side threshold value -SL2 (used in the start condition determination process (FIG. 7A) of the tilt prevention control routine described above. A threshold value correction routine (Fig. 8) for correcting software and -SL4 (hardware) will be described.

When this routine is started, first, in the tilt prevention control routine (FIG. 7), the expansion side counter C that is incremented when the tilt prevention start flag SF is set to the value 1
1. A process of setting the total value of the contraction counter C2 to the sampling number A (step 500) is performed, and it is determined whether the sampling number A has reached a predetermined number A1 (step 510). If the number of sampling times A does not reach the predetermined number of times A1, the following processing is not performed and the process goes to "RTN".
This routine is ended once. When the number of sampling times A has reached the predetermined number of times A1, the value obtained by subtracting the value of the contraction side counter C2 from the value of the expansion side counter C1 is set to the subtraction value S (step 520), and the value of the subtraction value S is set. Is greater than the upper limit allowable value + Su, smaller than the lower limit allowable value −Sd, or within the range of the upper limit allowable value + Su and the lower limit allowable value −Sd (step 530).

If the subtraction value S is within the range of the upper limit allowable value + Su and the lower limit allowable value −Sd, the sprung resonance component signal and each threshold value have an appropriate relationship to detect the precursor of the tilting movement. Therefore, the thresholds are not corrected, the counters C1 and C2 are reset (step 540), the process goes to "RTN", and this routine is once terminated.

On the other hand, when the subtraction value S is larger than the upper limit allowable value + Su, the average of the damping force data P is the extension side threshold value + SL.
Since it is biased to the side of 1, + SL3, the process (step 550) of adding the correction value α to the expansion side threshold values + SL1, + SL3 and the contraction side threshold values -SL2, -SL4, respectively, Correction is performed to raise the range delimited by each threshold value to the whole.

On the other hand, when the subtraction value S is smaller than the lower limit allowable value −Sd, the average of the damping force data P is the shrinkage side threshold value −SL2, −SL.
Since it is biased to the side of 4, the process (step 560) of subtracting the correction value β from the expansion side thresholds + SL1, + SL3 and the contraction side thresholds -SL2, -SL4 is performed, and the expansion side threshold + SL1. ,
Correct the correction so that the range of + SL3 and the shrinking side thresholds -SL2, -SL4 are reduced to the whole.

After the correction (steps 550 and 560), the counters C1 and C2 are reset (step 540), the process goes to "RTN", and this routine is once terminated.

Therefore, the damping force data P is the extension side threshold value + SL1, + SL
As a result of comparing 3 or the number of times the shrinkage side threshold value -SL2, -SL4 is exceeded, when the number of times is deviated by a predetermined value or more, that is, the traveling conditions such as the number of passengers and the change with time of the shock absorber 2 are changed. The vibration state of the vehicle changes, the sprung resonance component signal (damping force data P), the extension side threshold value,
When a bias occurs in the relationship with the contraction-side threshold, each threshold is corrected so as to eliminate the bias. As a result, the sprung resonance component signal and the range of the extension side threshold value and the contraction side threshold value are maintained in a predetermined relationship, and the tilt prevention control routine (FIG. 7) and the damping force control routine (FIG. 6). By executing (1), it is possible to detect the precursor of the tilt occurrence with high accuracy and accurately prevent the tilt.

As described above, according to the suspension control device of the embodiment, the traveling condition such as the number of passengers and the change of the shock absorber 2 with time changes to change the vibration state of the vehicle. When a bias occurs in the relationship between the threshold value and the contraction-side threshold value, each threshold value is corrected so as to eliminate the bias, and therefore, the value of the sprung resonance component signal (damping force data P), The difference between each threshold value does not shrink or expand, the magnitude of the sprung resonance component is accurately determined, and it is possible to maintain good vehicle tilt detection accuracy.
It has an excellent effect that it is possible to accurately prevent the vehicle from tilting.

Further, since the suspension control device of the embodiment corrects each threshold value as needed when the number of times of execution of flapping prevention reaches the predetermined number of times A1, the threshold value of There is an advantage that the correction is performed quickly and the prevention is more accurate on such a road surface.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it is needless to say that the present invention can be implemented in various modes without departing from the scope of the present invention. For example, when there are a large number of passengers or when the traveling distance is long and the shock absorber is affected by changes over time, it is assumed that the vibration state of the vehicle will change, and the extension side threshold value and the contraction side threshold value are set in advance. The value may be corrected. Further, the sprung-side resonance component and the expansion-side threshold value and the contraction-side threshold value are not used for correction such that the predetermined correction values .alpha. And .beta. The magnitude of the correction value may not be changed according to the degree of the bias, or the correction value may be corrected by multiplying it by a threshold value instead of adjusting the correction value. Alternatively, the correction value may be added to or subtracted from the damping force data P.

Effects of the Invention As described in detail above, according to the suspension control device of the present invention, the vibration state of the vehicle when the vehicle is in the sprung vibration state near the sprung resonance frequency, the extension side threshold value,
Since the expansion side threshold value and the contraction side threshold value are corrected so that the predetermined relationship with the contraction side threshold value is maintained, running conditions such as the number of passengers and changes in the shock absorber with time change, and Even if the vibration state changes, the excellent effect that the detection accuracy of the vehicle tilt can be maintained well and the accurate vehicle tilt prevention can be realized is achieved.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a basic configuration of the present invention, FIG. 2 is a schematic configuration diagram showing an overall configuration of a suspension control device as one embodiment of the present invention, and FIG. FIG. 3 (B) is an enlarged sectional view of a main part of the shock absorber, FIG. 4 is a block diagram showing a configuration of an electronic control device of the present embodiment,
FIG. 5 shows a low pass filter 55 and a high pass filter 56.
6 is a graph showing an example of a damping force detection signal that has passed through, FIG. 6 is a flowchart showing a damping force control routine, FIGS. 7 (A) and 7 (B) are flowcharts showing a flapping prevention control routine, and FIG. 8 is a threshold. It is a flow chart which shows a value amendment routine. 2FL, 2FR, 2RL, 2RR …… Variable damping force type shock absorber 4 …… Electronic control unit 25FL, 25FR, 25RL, 25RR …… Piezo load sensor 27FL, 27FR, 27RL, 27RR …… Piezo actuator 54 …… Damping force detection Circuit 55 …… Low pass filter 56 …… High pass filter 58 …… High voltage application circuit 62 …… High voltage power supply circuit

Claims (1)

[Claims] 1. A vibration state detecting means for detecting a vibration state generated in a vehicle due to a change in a road surface, and a spring for extracting a frequency component near a sprung resonance frequency among vibration components from the detected vibration state of the vehicle. Upper resonance component extraction means and high damping force maintenance that maintains a high degree of damping force of the shock absorber when the magnitude of the extracted sprung resonance component exceeds the extension side threshold value or the contraction side threshold value In the suspension control device including means, when the vehicle is in a sprung vibration state near a sprung resonance frequency, the magnitude of the extracted sprung resonance component is equal to the extension side threshold value or the contraction side threshold value. The threshold frequency correcting means for comparing the exceeding frequencies and correcting the expansion-side threshold value and the contraction-side threshold value on the side where the both frequencies are about the same are provided. Spension control device.