JPS60151110A - Road-surface state detector - Google Patents

Abstract

PURPOSE:To aim at improvements in steerability and stability for driving a car, by taking frequency components equivalent to both springing and unspringing resonant values individually out of the vibration inputted into the car, while comparing them with each of the specified reference values, and making it so as to judge a road state according to size in the comparison. CONSTITUTION:On the basis of vibration to be transmitted to a car body, a road state sensor 1 makes a road surface detection signal DS input into each of processing circuits 30 and 40. The circuit 30 outputs an unspringing road surface signal RS1 upon comparing an unspringing road state signal, proportional to size of the surface unevenness, with the unspringing reference voltage Rref1. Likewise, the circuit 40 outputs a springing road state signal RS2. A damping force regulating actuator 56 is driven via microcomputer 65 and a drive circuit 60, while a damping force select signal is inputted into a judging level setting circuit 70 whereby the damping force is selected where it should be, according to the road state. With this constitution, steerability and stability for driving a car are improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a road surface condition detection device for detecting the quality of a road surface condition.

[Prior art]

Conventional road surface condition detection devices include, for example, those that use stroke sensors attached to shock absorbers that make up the suspension, ultrasonic vehicle height sensors attached to the vehicle body, etc. Based on the detection signals of these sensors, The unevenness of the road surface is detected from the magnitude of the displacement, etc.
It was used to judge good roads and bad roads. By controlling the damping force of the shock absorber depending on the quality of the road surface, the suspension characteristics are changed to improve the handling stability and ride comfort of the vehicle.

[Problems with conventional technology]

However, in such conventional road surface condition detection devices, the amount of displacement detected by the sensor is compared with a predetermined reference value set in advance, and the quality of the road surface is determined based on the magnitude of the displacement detected by the sensor. Since the reference value does not change even if the characteristics of the device change, there is a problem in that even if the vehicle is driven on the same road, the determination results differ depending on the difference in the suspension characteristics.

[Purpose of the invention]

This invention was made by focusing on such conventional problems, and it is possible to separate frequency components corresponding to unsprung resonance and frequency components corresponding to unsprung resonance from vibrations input to a vehicle from the road surface. Individually extract these unsprung and spring main resonance frequency components to predetermined reference values according to the characteristics of the suspension device.

The purpose of the present invention is to solve the above problem by determining the condition of the road surface based on the magnitude of the road surface.

[Structure of the invention]

Accordingly, the present invention provides a road surface condition detector that detects vibrations from a road surface applied to a vehicle through a suspension whose damping force or spring constant is controlled according to road surface conditions, and outputs a signal corresponding to the vibrations. , receives a signal from the road surface condition detector, extracts a frequency component corresponding to unsprung resonance of the vehicle from the signal, and compares the unsprung resonance frequency component with a predetermined reference value. a first signal processing circuit that outputs an unsprung road surface condition signal corresponding to the result;
receiving a signal from the road surface condition detector and extracting a frequency component corresponding to unsprung resonance of the vehicle from the signal;
and a second signal processing circuit that compares the spring main resonance frequency component with a predetermined reference value and outputs a sprung road surface condition signal corresponding to the result, the first signal processing circuit and the first signal processing circuit. a reference value setting circuit that sets at least one of the respective reference values in the second signal processing circuit according to the control state of the suspension, and the reference value setting circuit sets at least one of the respective reference values in the second signal processing circuit according to the control state of the suspension, and The present invention relates to a road surface condition detection device that detects road surface conditions.

[Basics of invention]

Incidentally, unevenness of the road surface causes unsprung resonance in a vehicle, which is resonance between the front and rear axle suspensions and wheels, and unsprung resonance, which is caused by rolling or bouncing of the vehicle. High frequency vibrations with a relatively low amplitude of 13 Hz cause unsprung resonance to occur due to low frequency vibrations with a relatively high amplitude of 1-2 Hz.

On a smooth road such as a paved road, the force transmitted from the road surface to the vehicle is small, and both the unsprung and main resonance frequency components appear small. ), the main spring resonance frequency component appears small, but the unsprung resonance frequency component appears large. Furthermore, there is a gravel road with many bumps (hereinafter referred to as a rough road).

), the unsprung and spring main resonance frequency components are both thick (appearing), and roads with temporary irregularities such as manhole bulges and road joints appearing in places on the paved road (hereinafter referred to as large uneven roads). ), only the spring main resonance frequency component appears significantly for each temporary unevenness.Therefore, it is difficult to determine how the detection signals corresponding to the unsprung and spring main resonance frequency components differ from the reference voltage corresponding to the reference frequency. By checking whether there is a relationship, it is possible to determine whether the road on which the vehicle is traveling is a good road, a slightly bad road, a very bad road, a large uneven road, etc.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

1 to 3 are diagrams showing one embodiment of the present invention.

First, to explain the configuration, reference numeral 1 in FIG. 1 is a road surface condition detection sensor, which is a specific example of a road surface condition detector. The suspension strut 2 that makes up the device
It detects vibrations transmitted from the road surface to the suspension stranoto 2 through the wheels, and outputs a signal representing the road surface condition according to the vibrations.

Suspension strand 2 is shock absorber 3
and a coil spring 4 arranged concentrically on the outside of the shock absorber 3.
Its lower end is seated on a lower spring plate 1-6 fixed to the outer cylinder 5 of the shock absorber 3, and its upper end is seated on the lower surface of an upper spring plate 7 in a ring shape. The upper spring plate 7 is relatively rotatably supported via a bearing 10 by a hair ring holder 9 fitted onto the upper end of the piston rod 8 of the shock absorber 2. This allows the suspension strut 2 to rotate during steering. Displacement is allowed.

Such hair ring holder 9 and insulator plate 1
mounting insulator 1 interposed between
2, the upper end of the suspension strut 2 is fixed to the vehicle body side member 13, and the lower end of the suspension strut throat 2 is fixed to the wheel side member ( (Route in the figure).

Further, a cover plate 15 is fitted onto the inside of the bearing holder 9 at the upper end of the piston rod 8, and a road surface condition detection sensor 1 is inserted between the cover plate 15 and the bearing holder 9. It is tightened and fixed to the piston rod 8 by a NAND 16. 17 is a dust cover.

The shock absorber 3 is constructed so that its damping force can be changed in three stages by changing the area of the orifice provided in the piston part, as shown in a cross-section of the main part in FIG. ing. This shock absorber 3 is controlled by control signals from the control circuit shown in FIG. 1, and has three damping force levels as shown in FIG. software).

That is, in FIG. 4, 50 is an outer cylinder, 51 is an inner cylinder, and 52 is a piston. The inner cylinder 51 and the piston 52 are integrally formed, and the piston 52 allows the inside of the outer cylinder 50 to It is defined into a liquid chamber 53 and a lower liquid chamber 54. The inner cylinder 51 is provided with a radial hole 51a, and the piston 52 is provided with an axial hole 52a.
Both holes 51a and 52a are communicated with each other through a communication hole 55a provided in a rotor 55 built into the rotor 55.

The opening on the radial hole 51a side of the communication hole 55a is branched into four directions, and the two opposing openings have different cross-sectional areas, and the remaining two openings have different cross-sectional areas than the other two. It is formed smaller than the Therefore, depending on the stopping position of the rotor 55, the upper liquid chamber 54 and the lower liquid chamber 55 are communicated by three types of liquid paths with different flow rates, and the damping force is set in three levels: hard, normal, and soft depending on each branch path. can be switched to

The rotor 55 is also internally fixed in the inner cylinder 51.
Drive shaft 56 of step motor 5G, which is an actuator
a, and the liquid path is switched by driving a step motor 56. A disk 57 made of an insulator is fixed to the drive shaft 56a.
There are three types of conductive patterns 57a, 57b, 57 on the top surface of the
c are arranged concentrically. A stator 58 fixed to the inner cylinder 51 faces above the disc 57, and three brushes 58a provided on the lower surface of the stator 58 are connected to the conductive patterns 57a, 57b, and 57c. They are in sliding contact with each other.

Since the conductive patterns 57a, 57b, and 57c are electrically conductive to each other, but have different lengths, the signals generated at the two lead terminals differ depending on the stopping position of the disk 57.

By feeding these signals to the drive circuit of the shock absorber 3, the step motor 56
drive control is performed. 59 is a signal take-out line;
It is connected to the three brushes 58a, respectively.

As shown in an enlarged view in FIG. 3, the road surface condition detection sensor 1 includes a disc part 20a fixed to the hair ring boulder 9 and having an opening at the center, and a cylindrical part 20b extending downward from the center part. a mounting plate 20, an annular plate 21 fixed to the cover plate 15 and into which the cylindrical portion 20b of the mounting plate 20 is inserted, and a piezoelectric element sandwiched between the annular plate 21 and the mounting plate 20. The device piezoelectric element 22 is composed of a pair of piezoelectric bodies 23 having a bimorph structure and formed in a ring shape, and an electrode plate 24 also formed in a ring shape. A pair of piezoelectric bodies 23 are disposed on both sides facing each other and are polarized in opposite directions. Then, a lead wire 25 is led out from a part of the outer peripheral edge of the electrode plate 24, and a ground wire (not shown) is led out from the opposite side of the piezoelectric body 23 from the electrode plate 24, and this is connected to the vehicle body side member 13. It is grounded, and the other outer peripheral surfaces are insulated and coated with an insulating resin material 26.

The road surface condition detection sensor 1 includes a suspension system I.
- A load corresponding to 31 supported by Rano 1-2 will be applied, and a detection signal corresponding to the front vehicle's human force due to pushing up from the road surface etc. will be output.

In this case, if the piezoelectric body 23 as described above is applied as the road surface condition detection sensor 1, the characteristics of the piezoelectric body 23 will not be sensitive to the load that is applied steadily, and For example, a positive output voltage is output for a change in load, and a negative output voltage for a decrease in load is output as a detection signal corresponding to the magnitude of the fluctuating load.

Therefore, it is insensitive to stationary loads, and a load detection signal corresponding only to changes is outputted.

The detection signal DS of this road surface condition detection sensor l is shown in FIG.
The detection signal DS has a waveform in which vibration components such as A) are superimposed, and the detection signal DS is transmitted through an amplifier circuit if necessary to detect the size of road irregularities, their continuous state, etc., as shown in Fig. 1. A first signal processing circuit 30 and a second signal processing circuit for determining the road surface condition.
and a signal processing circuit 40, respectively.

The first signal processing circuit 30 receives the detection signal DS from the road surface condition detection sensor 1, extracts a frequency component corresponding to the unsprung resonance of the vehicle from the signal, and combines the unsprung resonance frequency component with a predetermined This circuit compares a reference value to determine its magnitude, and is comprised of a bypass filter 31, a full-wave rectifier circuit 32, a rectifier and smoothing circuit 33, and a comparator 34.

The bypass filter 31 has a frequency of 3 to 5 Hz to extract a frequency component (12 to 13 Hz) corresponding to unsprung resonance from the detection signal DS input from the road surface condition detection sensor 1.
It is set to cut the Hz frequency component.

A predetermined frequency component is cut out and passed through the bypass filter 3.
The spring signal H3I having a waveform as shown in FIG. 6(B) output from 1 is full-wave rectified by the full-wave rectifier circuit 32 to produce a rectified signal with a waveform as shown in FIG. 6(C). AS! This is input to the rectifying and smoothing circuit 33.

The rectifying and smoothing circuit 33 is composed of, for example, an AC-DC converter, and from its effective value, a corresponding voltage output FSI as shown in FIG. 6(D) is outputted to the comparator 34. The voltage output F S 1 from the rectifying and smoothing circuit 33 inputted to the positive terminal of the comparator 34 is determined to be different in magnitude from the reference value voltage Vrefl corresponding to a predetermined reference frequency inputted from the negative terminal. The unsprung road surface condition signal R3i as shown in FIG. 6(E) corresponding to the comparison result is outputted from the comparator 34. Therefore, this spring-1/road surface condition signal R3
I can determine the magnitude of the unsprung resonance frequency included in the vibration input from the road surface.

The second signal processing circuit 40 receives the detection signal DS from the road surface condition detection sensor 1, extracts a frequency component corresponding to the unsprung resonance of the vehicle from the signal, and combines the unsprung resonance frequency component with a predetermined base. ! (This is a circuit that compares the bird value and determines its magnitude, and is composed of a 1'J-pass filter 41, a bypass filter 42, a full-wave rectifier circuit 43, a rectifier smoothing circuit 44, and a comparator 45. There is.

The low-pass filter 41 extracts a frequency component (1 to 2 Hz) corresponding to the spring resonance from the detection signal DS input from the road surface condition detection sensor 1.
5 II It is set to cut the z frequency component. The sprung mass signal 1-3 having a waveform as shown in FIG. 6(F) with predetermined frequency components cut and outputted from the low-pass filter 41 is processed by the bypass filter 42 to 0.2 to 0.31-1 z. The DC frequency component of is removed from the high-pass filter 42 (FIG. 6 CG).
The unsprung resonance frequency component (1-2 Hz) as shown in
Only the sprung signal H32 is output.

Sprung signal 1-I S 2 from bypass filter 42
For example, it is full-wave rectified by the full-wave rectifier circuit 43 (Fig. 6 (1)).
A rectified signal AS2 having a waveform as shown in is obtained, and this is input to the rectifying and smoothing circuit 44. The rectifying and smoothing circuit 44 is a false 6
For example, 'jLQQ is performed by an AC-DC converter, and a corresponding voltage output FS2 as shown in FIG. 6(1) is output from the effective value to the comparator 45.

The voltage output FS2 from the rectifying flat IFh circuit 44 inputted to the positive αji1 terminal of the comparator 45 is between the base tp-value voltage ■rcf2 corresponding to the predetermined base 2% frequency inputted from the negative terminal of the comparator 45. The magnitudes thereof are compared, and a sprung road surface condition signal RS2 as shown in FIG. 6(J) corresponding to the comparison result is outputted from the comparator 45. Therefore, this sprung road surface condition signal RS
2, it is possible to determine the magnitude of the unsprung resonance frequency included in the vibration human force from the road surface.

The first signal processing circuit 30 and the second signal processing circuit 4
The reference value voltage Vrefl input to the negative terminal of each comparator 34.45 at 0.0.

The value of Vref2 is set by a constant level setting circuit 70 of 1'.

The determination level setting circuit 70 includes a base on the spring -F side ((() a level setting unit 71 for setting the value voltage Vrel'l, an analog switch, a cheer 2, and a base on the spring side!1().

Setting unit 73 for setting the value voltage Vref2
It consists of analog switch, analog switch, and cheer 4. The level setting section 71 on the lower side of the spring includes resistors R1-R2 and R3-R.
4. From the voltage dividing circuit using R5-RG, the level setting section 73 on the spring upper side is connected to the resistors R7-R8, R9-RIOL.
It consists of a voltage dividing circuit using Rl 1-R12, and three types of base l(C'- voltages are generated respectively) by the operation of each analog switch 72, 74.

Further, the analog switches 72 and 74 branch and receive a control signal output from a microcomputer 65, which is a specific example of a control circuit for switching and controlling the damping force of the shock absorber 3, and set the damping force using the control signal. A reference value voltage Vref corresponding to the damping force applied is sent to each comparator 34, 45. FIG. 7 shows an example of the relationship between the four damping forces (soft, normal, heart) of the shock absorber 3 and the reference voltage values (Vra, 'Vrb, Vrc).

The road surface condition detection sensor 1 and the first signal processing circuit 30
, a second signal processing circuit 40 , and a determination level setting circuit 7
0 constitutes a road surface condition detection device. 8(A) to 8(D) are graphs showing the output waveforms of the road surface condition detection sensor 1. FIG. 8(A) shows a good road, FIG. 8(B) shows a slightly rough road, Figure (C) shows the detection signal when the vehicle is traveling on a very rough road, and Figure (D) shows the detection signal when the vehicle is traveling on a highly uneven road.

Next, the overall operation will be explained.

First, the road surface condition detection sensor 1 detects the road surface condition based on vibrations transmitted from the road surface to the vehicle body via the suspension struts 2, and detects waveform signals as shown in FIGS. 8(A) to 8(D). The detection signal DS is input to the first signal processing circuit 30 and the second signal processing circuit 40, respectively. In the first signal processing circuit 30, an unsprung road surface condition signal obtained in proportion to the size of the unevenness of the road surface detected by the road surface condition detection sensor 1, and a reference value voltage Vrefl on the unsprung side which is a reference value. are compared, and an unsprung road surface condition signal R3I corresponding to the result is generated.

On the other hand, in the second signal processing circuit 40, the unsprung road surface condition signal obtained in proportion to the size of the unevenness of the road surface detected by the road surface condition detection sensor 1 and the reference value voltage on the sprung side which is the reference value. Vref2 is compared, and a sprung road surface condition signal R32 corresponding to the result is generated.

Now, assuming that the damping force of the shock absorber 3 does not change, when driving on a good road, the road surface condition detection sensor 1
A signal having a waveform as shown in FIG. 8(A) is output from the circuit 30, and both the unsprung resonance frequency component and the unsprung resonance frequency component included in the signal are small, and the first signal processing circuit 30
and each rectifying and smoothing circuit 33.4 of the second signal processing circuit 40
The values of the voltage outputs FSI and FS2 output from 4 are both low, and both voltage outputs FSI and FS2 are respectively at the reference value Vr.
efl is smaller than Vref2, the comparator 34 of the first signal processing circuit 30 outputs the low level (L) unsprung road surface condition signal R3I, and the comparator 45 of the second signal processing circuit 40 also outputs the low level A sprung road surface condition signal R32 (L) is output. Therefore, in the output state of such a signal, it is determined that the road surface on which the vehicle is traveling is a good road with no unevenness.

Furthermore, when driving on a slightly rough road, the road surface condition detection sensor 1 outputs a signal with a waveform as shown in FIG. 8(B).
The unsprung resonant frequency component included in that signal is high, but the unsprung resonant frequency component is low, so the comparator 34 outputs a high-level unsprung state signal R3I, while the comparator 45 outputs a low-level unsprung state signal R3I. A working status signal R52 is output. Therefore, in the output state of such a signal, it is determined that the road surface on which the vehicle is traveling is a slightly rough road.

Furthermore, when driving on a very rough road, the road surface condition detection sensor 1
outputs a signal with a waveform as shown in FIG.
5 outputs a spring work state detection signal R3I and a spring work state detection signal R32, both of which are at high level. Therefore, in the output state of such a signal, it is determined that the road surface on which the vehicle is traveling is extremely bad.

Furthermore, when driving on a highly uneven road, the road surface condition detection sensor 1 outputs a signal with a waveform as shown in FIG. The lower resonance frequency component is high, the comparator 34 outputs a low level spring work state detection signal R3I, and the comparator 45 outputs a high level spring work state FF.

A detection signal R32 is output. Therefore, in the output state of such a signal, it is determined that the road surface on which the vehicle is traveling is highly uneven.

The above is summarized in a table in FIG. 9, and in this way, based on each output signal of the first signal processing circuit 30 and the second signal processing circuit ti40, the magnitude of the unevenness of the road, its continuous state, etc. Accordingly, it is possible to easily and quickly determine whether the road surface is good or bad, such as a good road, a slightly bad road, a very bad road, a road with large bumps, etc.

By the way, the road surface condition detection sensor 1 detects the transmission force input from the wheels and transmitted to the shock absorber 3. The transmission force F, which is not shown in FIG. 10, can be explained based on a suspension model diagram as follows.

F=C(xi-Ω2) C... Damping constant λ1 of the shock absorber 3... Displacement of sprung mass (ml) 2... Unsprung mass (ff
12) Displacement amount In the same figure, kl is the spring constant of the coil spring, and k2 is the spring constant of the wheel.

As is clear from this equation, when the damping force of the shock absorber 3 is changed to change its damping constant C, the transmitted force F changes accordingly.

Therefore, as in the present invention, the damping force switching signal is input to the determination level setting circuit 70 at the time when the damping force is switched, and the change in the signal level of the road surface condition detection sensor 1 that is assumed from the damping force level at that time is Correspondingly, the road surface condition can be accurately determined by changing the reference value voltage Vref, which is a criterion for determining the road surface condition, and comparing the reference value voltage Vref corresponding to the suspension characteristics with the detection signal.

That is, when determining the road surface condition, the damping force is controlled to be switched in three stages, for example, as shown in FIG.
For example, the damping force is set to -1 when driving on a good road, normal when driving on a slightly rough road, and soft when driving on a very rough road. ), a damping force switching signal is input from the microcomputer 65 to the judgment level setting circuit 70 at the time when the damping force is switched. The judgment level setting circuit 70 sets the reference value voltage (Vrefl>Vref2) corresponding to the damping force as shown in FIG.
), that is, when the damping force is in the soft position, the corresponding low reference value voltage Vra is set, and when the damping force is in the normal position, the corresponding medium reference value voltage Vra is set.
When the damping force is in the hard position, the corresponding high reference value voltage Vrc is applied to each comparator 34 of the first and second signal processing circuits 30 and 40, respectively.
, 45.

For this reason, the detection signal from the road surface condition detection sensor 1 is compared with the reference value voltage Vref that takes into account the suspension characteristics of the vehicle when seated, and the sprung and unsprung road surface condition signals R31°R32 corresponding to the results are generated. The signals are output from the first and second signal processing circuits 30 and 40, respectively.

Therefore, when controlling the damping force of the shock absorber 3 on a road such as the one shown in FIG. Considering the control to change to
It decreases at the same time as the damping force is switched, but even if the vibration caused by the human input decreases, the first or second signal processing circuit 30.
Since the levels of the signals outputted from 40 are approximately equal, it is possible to accurately determine the road surface condition as a good road or a slightly bad road, regardless of the characteristics of the suspension device.

Therefore, if the reference value voltage Vref is not changed in accordance with the damping force, the road surface condition detection sensor 1 detects when the damping force changes from the hard position for driving on a good road to the normal position for driving on a slightly rough road. The force F is reduced, the output of the first signal processing circuit 30 changes to low level, and it is determined that the road is good, so the damping force is switched to the original hard position. Then, when the damping force is switched to the hard position, the output of the first signal processing circuit 30 changes to high level again, so the damping force is switched to the normal position again, and this is repeated, causing control hunting. However, in the present invention, since the reference value voltage (ref) is controlled according to the suspension characteristics, the above-mentioned control)\inching does not occur.

In this way, the road surface condition can be detected in detail by taking into account the suspension characteristics of the vehicle, and the damping force of the shock absorber, the air spring constant of the vehicle height adjustment device, the stiffness of the stabilizer, etc. of the suspension system can be controlled depending on the road surface condition. By doing so, the handling, stability, etc. of the vehicle can be improved.

In this embodiment, the road surface condition detection sensor 1 having the piezoelectric element 22 is used as the road surface condition detector, but other sensors may also be used, such as a vehicle height sensor that detects the relative displacement between the sprung portion and the unsprung portion. A sensor, an acceleration sensor that detects the acceleration of the displacement, or the like can be used. Furthermore, even if a strain gauge or the like is used in place of the piezoelectric element 22, the same effect as in the embodiment described above can be obtained.

Furthermore, among the first signal processing circuit 30 and the second signal processing circuit 40, a frequency-voltage converter (F The same effect as in the above embodiment can also be obtained by using a -V converter).

〔Effect of the invention〕

As explained above, in the present invention, the unsprung resonance frequency component of the vehicle is detected based on the detection signal from the road surface condition detector that detects the road surface condition such as the size and continuity of road surface irregularities, the presence or absence of gravel, etc. and the unsprung resonant frequency component are individually extracted, and the road surface condition is determined based on the magnitude thereof, and the reference voltage value that is the basis for the determination is changed in accordance with the damping force of the suspension device or the control state of the spring constant. Therefore, the road surface condition, such as the degree of roughness of the road surface due to vibrations directly applied to the vehicle from the road surface, can be determined in detail in consideration of the suspension characteristics. Therefore, the characteristics of the suspension device, such as the damping force of the shock absorber, the spring constant of the vehicle height adjustment device, or the rigidity of the stabilizer, can be precisely and appropriately controlled depending on the road surface condition, and control hunting does not occur, and the vehicle The effect is that the maneuverability and stability of the vehicle can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a sectional view showing the road condition detector according to the present invention assembled into a suspension device, FIG. 3 is a sectional view showing a specific example of the road condition detector, and FIG. 4 is a sectional view of a shock absorber. A sectional view showing the main parts, FIG. 5 is a graph showing the relationship between piston speed and damping force, and FIGS.
(J) is an output waveform diagram of the road surface condition detector, Figure 7 is a graph showing the relationship between damping force and reference voltage, and Figure 8 (A)
-(D) are output waveform diagrams of the road surface condition detector corresponding to the road surface condition, and FIG. 9 shows the output waveforms of FIGS. Figure 10 is a military vehicle suspension model diagram, and Figure 11 is a diagram of the output waveform of the road surface condition detector when the damping force is switched and controlled on a slightly rough road. It is. 1...Road surface condition detection sensor (road surface condition detector)
, 3... Shock absorber, 20...
・Torii” board, 21... Circular board, 22...
・Piezoelectric element, 30...First signal processing circuit, 4
0...Second signal processing circuit, 31.42...
... Bypass filter, 32.43 ... Full wave rectifier circuit, 33.44 ... Rectifier smoothing circuit, 34
．． 45... Comparator, 5G... Step motor, 65... Control circuit, 70...
...Judgment Level Setting Circuit Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Tetsuya Mori Representative Patent Attorney Yoshiaki Naito Patent Attorney Tadashi Shimizu Representative Patent Attorney Yuze Horide Figure 4 Figure 5 Tamagogoso Low citrus wealth member powder, #thief Nanashima - vomit) - 1zeki prefecture

Claims (1)

[Claims] a road surface condition detector that detects vibrations from the road surface applied to the vehicle through a suspension whose damping force or spring constant is controlled according to the road surface conditions and outputs a signal corresponding to the vibrations; Upon receiving a signal, a frequency component corresponding to the unsprung resonance of the vehicle is extracted from the signal, and the unsprung road surface condition is determined by comparing the magnitude of the unsprung resonance frequency component with a predetermined reference value. a first signal processing circuit that outputs a signal; and a first signal processing circuit that receives a signal from the road surface condition detector, extracts a frequency component corresponding to the unsprung resonance of the vehicle from the signal, and extracts a frequency component corresponding to the unsprung resonance frequency component of the vehicle; a second signal processing circuit that compares the magnitude with a reference value and outputs a sprung road surface condition signal corresponding to the result; At least one of the reference values of
A road surface condition detection device comprising a reference value setting circuit that sets a reference value according to a control state of the suspension, and detects a head condition based on the sprung road surface condition signal and the sprung road surface condition signal. .