JPS60213516A - Road condition detector - Google Patents

Abstract

PURPOSE:To provide accurately identified road condition which is free from any influence of temperature of working fluid by providing a reference value setting circuit which determines both the reference values of a primary and a secondary signal processing circuit according to a signal detected by a temperature detector. CONSTITUTION:A road condition detector 1 generates a detected signal DS which shows a road condition. The signal DS is sent to a primary and a secondary signal processing circuit 20 and 30 provided for judging the road condition. One input terminal of the comparator 25 in a circuit 20 receives the output signal DV1 of an AC-DC converting circuit 24 while the other input terminal thereof receives a reference level voltage VR1 from a discriminating reference level setting circuit 40. Once reference level voltages VR1 and VR2 according to the temperature of working fluid in a shock absorber are determined in the circuit 40, if a signal DS generated from a detector 1 is varied under the influence of attenuating force of the shock absorber, the variation can be compensated so that the circuit 40 generates an accurately identifying signal.

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]

As a conventional road surface condition detection device, for example, Japanese Patent Application Laid-Open No. 58
There is one disclosed in Publication No.-30542. This item includes a variable orifice that is incorporated into a hydraulic shock absorber and whose flow cross-sectional area can be adjusted to change the damping force of the cylinder, and a variable orifice that is incorporated into the shock absorber to change the flow cross-sectional area of the variable orifice. a vehicle height sensor that electrically detects the vehicle height value of the vehicle; and a control circuit that supplies exciting current to the solenoid based on the detection signal of the vehicle height sensor to reduce the flow cross-sectional area of the variable orifice. The damping force of the shock absorber is increased under a predetermined vehicle height condition,
Based on the detection signal of the vehicle height sensor, the unevenness of the road surface is detected from the magnitude of the displacement, etc., to determine whether the road is good or bad, and the damping force of the shock absorber is controlled according to the quality of the road surface. The suspension characteristics were changed to improve vehicle handling stability and ride comfort.

[Problems with conventional technology]

However, in such conventional road surface condition detection devices, the amount of displacement detected by the vehicle height sensor is compared with a predetermined reference value set in advance, and the quality of the road surface is determined based on the magnitude. Since the reference value does not change even if the characteristics of the suspension device change, there is a problem in that even when driving on the same road, the determination results differ depending on the difference in the suspension characteristics. In other words, a characteristic of a suspension device is that the damping force changes due to changes in viscosity due to temperature changes in the hydraulic oil of the shock absorber that makes up the suspension, and the damping force has temperature dependence. Damping force decreases. Therefore, the damping force is thick in cold regions and warm regions (different, and the damping force is also different when the vehicle starts and when the hydraulic oil temperature reaches a steady state. Therefore, the damping force is different when the hydraulic oil temperature is in a steady state. If the judgment level of the road surface condition is set based on the damping force characteristics of the shock absorber at the time, the damping force will be too high or too low. There were problems such as road surface information changing due to changes in hydraulic oil temperature, resulting in errors in road surface condition detection.

[Purpose of the invention]

This invention was made by focusing on these conventional problems, and it is possible to separate frequency components corresponding to sprung mass resonance and frequency components corresponding to sprung mass resonance from vibrations input to a vehicle from the road surface. The above problem can be solved by extracting these unsprung and main spring resonance frequency components individually and comparing them with a predetermined reference value according to the temperature dependent characteristics of the suspension device and determining the road surface condition based on the magnitude. It aims to solve the problem.

[Structure of the invention]

In order to achieve the above object, the present invention provides a temperature detector for detecting the temperature of a working fluid in a suspension device in which vibrations are transmitted from the road surface through the wheels and the working fluid applies a damping force or a spring constant; A road condition detector that detects vibrations applied from the road surface and outputs a corresponding signal; and a device that receives a detection signal from the road condition detector and selects a signal corresponding to the vehicle's sprung resonance frequency. a first signal processing circuit that extracts a frequency component, compares the sprung resonance frequency component with a predetermined reference value, and outputs an unsprung road surface condition signal corresponding to the result; and the road surface condition detection circuit. receives a signal from the device, extracts a frequency component corresponding to the vehicle's sprung resonance frequency from that signal, compares the spring main resonance frequency component with a predetermined reference value, and responds to the result. a second signal processing circuit that outputs a sprung road surface condition signal, and respective reference values in the first signal processing circuit and the second signal processing circuit are set based on the detection signal of the temperature detector. The present invention is characterized by comprising a reference value setting circuit.

〔Example〕

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

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

First, to explain the configuration, in FIG. 1, 1 is a road surface condition detector, and as shown in FIG. , outputs a detection signal representing the road surface condition according to the vibration transmitted as a load from the road surface to the suspension strut 2 via the wheels.

Suspension strut 2 is shock absorber 3
and a coil spring 4 arranged concentrically on the outside of the shock absorber 3.
The lower end of the shock absorber 3 is seated on a lower spring plate 6 fixed to the outer cylinder 5 of the shock absorber 3, and the upper end thereof is seated on the lower surface of a ring-shaped upper spring plate 7.

The upper spring plate 7 is the shock absorber 3
The piston rod 8 is relatively rotatably supported via a bearing 1o by a bearing holder 9 fitted onto the upper end of the piston rod 8.

The suspension strut 2 is fixed at its upper end to a vehicle body side member 13 via a mounting insulator 12 interposed between a bearing holder 9 and an insulator plate 11, and a mounting eye 14 provided at a lower end is attached to a wheel. It is attached between the vehicle body side and the wheel side by being fixed to the side member (as shown in the figure).

Further, a cover plate 15 is fitted on the inside of the bearing holder 9 at the upper end of the piston rod 8, and a road surface condition detector 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 nut 16. 17 is a dust cover, and 18 is a lead wire of the road surface condition detector 1.

As shown in FIG. 1, the detection signal DS from the road surface condition detector 1 is transmitted through an amplifier circuit, if necessary, to a first signal DS for determining the road surface condition, such as the size of road irregularities and their continuous condition.
and a second signal processing circuit 30, respectively.

The first signal processing circuit 20 is an AC converter comprised of a bypass filter 21 to which the detection signal DS from the road surface condition detector 1 is supplied, and a full-wave rectifier circuit 22 and a rectifying and smoothing circuit 23 to which the output FH thereof is supplied. - It is composed of a DC conversion circuit 24 and a comparator 25 to which a DC level output AD consisting of the effective value of the unsprung resonance frequency component outputted from the conversion circuit 24 is supplied.

Here, the bypass filter 21 filters a relatively high frequency component (12 to 13H) corresponding to the sprung mass resonance frequency included in the detection signal DS input from the road surface condition detector 1.
In order to separate and extract z), the cutoff frequency is 3 to 5.
It is set to Hz.

Further, the comparator 25 has the above-mentioned A on one input side.
The output signal DVI of the C-DC conversion circuit 24 is supplied, and the reference level voltage VR from the determination reference level setting circuit 40, which will be described later, is supplied to the other input side, and DVI < VR.
A comparison output that becomes low level (L) when DVl≧VRt and becomes high level (H) when DVl≧VRt is output as the unsprung road surface condition determination signal CSt. Therefore, the magnitude of the unsprung resonance frequency component included in the vibration input from the road surface can be determined based on the unsprung road surface condition determination signal C3I.

The second signal processing circuit 30 includes a low-pass filter 31 to which the detection signal DS from the road/surface condition detector l is supplied, a bypass filter 3'2 that removes the DC signal component in the output signal FL, and An AC-DC conversion circuit 35 comprising a full-wave rectification circuit 33 and a rectification and smoothing circuit 34 to which an output signal is supplied, and a DC level output DV2 consisting of the effective value of the unsprung resonance frequency component output from this conversion circuit 35. and a comparator 36 to which is supplied.

Here, the low-pass filter 31 filters relatively low-frequency frequency components (1 to 2 Hz) corresponding to medium to sprung mass resonance included in the detection signal DS input from the road surface condition detector 1.
), the cutoff frequency is 3 to 5H.
It is set to z.

Further, the comparator 36 has the above-mentioned A on one input side.
The output signal DV2 of the C-DC conversion circuit 35 is supplied, and the reference level voltage VR2 from the determination reference level setting circuit 40, which will be described later, is supplied to the other input side, and DV2 < VH.
2, a comparison output that becomes low level (L) and becomes high level (H) when D2≧vR2 is output as the sprung road surface condition determination signal C82. Therefore, the magnitude of the sprung mass resonance frequency component included in the vibration input from the road surface can be determined based on this sprung mass road surface condition signal C32.

The judgment reference level setting circuit 40 is supplied with a detection signal DT from a temperature detector 41 that detects the working fluid temperature of the shock absorber 3 on its input side, and based on this detection signal DT, A reference level voltage V'R1 on the spring side and a reference level voltage VR2 on the sprung side are set. This judgment reference level setting circuit 4
0 is the reference level voltage VRt according to the characteristic curve shown in FIG. 6 for the working fluid temperature as shown in FIG.
, VR2.

Next, the effect will be explained. Now, assuming that the temperature of the working fluid of Shosoku Absorber 3 is in a steady state and that the damping force does not change due to temperature changes, if you are driving on a very rough road with undulations and gravel on the surface. As shown in FIG. 3 (al), when the road surface condition detector 1 A detection signal DS on which frequency components are superimposed is output.Therefore, a high level (H) road surface condition determination signal C is output from the comparator 25 of the first signal processing circuit 20.
3I is output, and the second signal processing circuit 30 outputs a high level (I) road surface condition determination signal C32, and these road surface condition determination signals C81 and C32 cause
It can be determined that the road is very bad.

In addition, even if the road surface is flat, when driving on a rough road with gravel etc. on the surface, the road surface condition detector 1 detects an amplitude with a low frequency as shown in A detection signal DS is output in which an unsprung resonant frequency component having a large amplitude and a high frequency is superimposed on a sprung resonant frequency component with a relatively small amplitude.Therefore, the comparator 25 of the first signal processing circuit 20 The level (H) road surface condition determination signal C8l is output, and the comparator 36 of the second signal processing circuit 30 outputs the low level (I,
) is output, and from these road surface condition determination signals C8l and C32, it can be determined that the road is slightly rough.

Furthermore, when driving on a flat road with no unevenness, the road surface condition detector 1 outputs a signal with a waveform as shown in FIG. 3 (C1), and the unsprung resonance frequency component included in the signal and the sprung mass resonance frequency 1 wave number components are both small, and each AC-DC conversion circuit 24 .
DC voltage VDI output from 35.

Both VD2 levels are low, and both DC voltages VD1°VD
2 are smaller than the reference values V Rl' and V R2, respectively, the comparator 25 of the first signal processing circuit 20 outputs a low level (L) unsprung road surface condition determination signal C3I.
is output, and the comparator 3 of the second signal processing circuit 30
6 or Lamoreau level (L) sprung road surface condition determination signal C
32 is output.

Therefore, in the output state of such a signal, it can be determined that the road surface on which the vehicle is traveling is a good road with no unevenness.

Furthermore, after passing a temporary unevenness such as a manhole on a good road, the road surface condition detector 1
As shown in l, only the sprung resonance frequency component has a large amplitude, and the amplitude of the sprung resonance frequency component is small, so
The first signal processing circuit 20 outputs a low level (L) road surface condition determination signal C3I, and the second signal processing circuit 30 or 3 2 outputs a high level (H) road surface condition determination signal C32. Based on these, it can be determined that the passage is temporary.

The above can be summarized as shown in the table below.

In this way, based on the respective output signals of the first signal processing circuit 20 and the second signal processing circuit 30, the road is divided into a good road, a slightly bad road, a very bad road, a large road, etc. The quality of the road surface, such as a bumpy road, can be easily and quickly determined.

Incidentally, first, vibrations corresponding to the unevenness of the road surface are transmitted to the road surface condition detector 1 via the wheels and the shock absorber 3, and a detection signal DS corresponding to the transmitted force is outputted. Here, the transmission force F is explained based on the suspension model diagram shown in FIG. 4 as shown in the following equation.

F=C(XI −X2) ・・・・・・・・・・・・+
11C... Attenuation constant x1 of shock absorber 3...
- Position of sprung mass (ml) x2...Position of unsprung mass (m2) In the same figure, k is the spring constant of the coil spring, and k2 is the spring constant of the wheel.

As is clear from this equation (1), when the damping force of the shock absorber 3 is changed and its damping constant C changes,
The transmission force F changes accordingly. Therefore, the detection signal DS output from the road surface condition detector 1 no longer corresponds accurately to the vibration component according to the actual road surface condition due to the change in the transmission force. In other words, the relationship between the damping force of the shock absorber 3 and the piston speed is such that when the temperature of the working fluid sealed inside is used as a parameter, the damping force decreases as the working fluid temperature rises, as shown in FIG. As a result, the detection level of the detection signal DS of the road surface condition detector 1 decreases.

Therefore, in the present invention, the temperature of the working fluid of the shock absorber 3 is detected by the temperature detector 41, and the detection signal DT
is supplied to the determination reference level setting circuit 40. In this determination reference level setting circuit 40, reference level voltages R1 and VH2 adapted to the working fluid temperature are set by a function generator having a characteristic curve shown in FIG. 6 based on the detection signal DT, and these are set in the first and the comparators 25 and 36 of the second signal processing circuit 20 and the second signal processing circuit 30, respectively.
In this way, by setting the reference level voltages VRI and VRz according to the working fluid temperature of the shock absorber 3 in the judgment reference level setting circuit 40, the road surface condition detection signal DS output from the road surface condition detector 1 can be adjusted. Even though it is affected by the damping force of the shock absorber ＼3,
It is possible to compensate for the variation due to this influence and output an accurate road surface condition determination signal.

In this way, the road surface condition is detected in detail taking into consideration the suspension characteristics of the vehicle, and depending on the road surface condition, for example, the damping force of the shock absorber of the suspension device, the air spring constant of the vehicle height adjustment device, or the rigidity of the stabilizer is adjusted. By controlling the above, it is possible to improve the handling, stability, etc. of the vehicle.

In this embodiment, a case has been described in which the road surface condition detector l is attached to the suspension strut 2, but in the case of a suspension having a coil spring, the road surface condition detector l is installed between the upper end of the coil spring and the vehicle body side. You may arrange|position the container 1.

In addition, the road surface condition detector 1 is not limited to a piezoelectric element, and may also be used, for example, a vehicle height detector that detects the relative displacement □ between the sprung mass and the unsprung mass, or a vehicle height detector that detects the acceleration of the displacement. An acceleration detector or the like can be used for detection. Furthermore, a strain gauge or the like is used instead of a piezoelectric element to
4. The above embodiments.

A similar effect can be obtained.

Furthermore, the temperature detector 41 that detects the temperature of the working fluid of the shock absorber 3 is not limited to directly detecting the temperature of the working fluid as shown above; 7 6 It is also possible to estimate the fluid temperature.

In addition, the first signal processing circuit 20 and the second signal processing circuit 30 detect the peak values of the unsprung resonance frequency component and the sprung resonance frequency component separated and extracted from the road surface condition detection signal DS, and Even if the value is compared with the reference value, the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As explained above, in this invention, the unsprung resonance frequency component of the vehicle included in the detection signal from the road surface condition detector according to the road surface condition such as the size and continuity of road surface irregularities, the presence or absence of gravel, etc. The road surface condition is determined by individually extracting the sprung mass resonance frequency components and comparing them with a reference level signal, and the reference level signal, which is the basis for the determination, is changed according to the temperature of the working fluid of the suspension device. This allows the road surface condition, such as the roughness of the road surface, to be determined by the vibrations from the road surface that are directly applied to the vehicle.
Accurate judgment can be made without being affected by the working fluid temperature. Therefore, for example, 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 controlled in a fine-grained manner (and appropriately) according to the road surface condition, and the maneuverability and stability of the vehicle can be improved. The effect is that it 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 a state in which the road surface condition detector according to the present invention is assembled to a suspension device, and FIG.
dl is an output waveform diagram of the road surface condition detector according to the road surface condition, FIG. 4 is a suspension model diagram of the vehicle, and FIG. 5 is a relationship between piston speed and damping force using working fluid temperature as a parameter. The graph, FIG. 6, is a graph showing the relationship between working fluid temperature and reference level voltage. 1... Road surface condition detector, 2... Suspension strut (suspension device), 3...
...Shock absorber, 20...First signal processing circuit, 30...Second signal processing circuit, 2
1...Bypass filter, 24.35...
...AC-DC conversion circuit. 9 31...Low pass filter, 25.36...
... Comparator, 40 ... Judgment reference level setting circuit. Patent applicant Nissan Motor Co., Ltd. agent Patent attorney Tetsuya Mori Agent Patent attorney Yoshiaki Naito Agent Patent attorney Shimizu Authorized agent Patent attorney Horiku double length 0 Ward dimensions

Claims (2)

[Claims] (1) A temperature detector that detects the temperature of the working fluid of a suspension device that transmits vibrations from the road surface through the wheels and that applies a damping force or spring constant using the working fluid, and a temperature sensor that detects vibrations from the road surface that are applied to the vehicle body. a road surface condition detector that outputs a signal corresponding to the detected signal; a first signal processing circuit that compares the magnitude of the upper resonance frequency component with a predetermined reference value and outputs an unsprung road surface condition signal corresponding to the result; and a first signal processing circuit that receives a signal from the road surface condition detector and outputs the signal. extracts a frequency component corresponding to the sprung mass resonance frequency of the vehicle from among them, compares the magnitude of the sprung mass resonance frequency component with a predetermined reference value, and outputs a sprung mass road surface condition signal corresponding to the result. a second signal processing circuit; and a reference value setting circuit that sets respective reference values in the first signal processing circuit and the second signal processing circuit based on the detection signal of the temperature detector. Features: Road surface condition detection device. (2) The road surface condition detection device according to claim 1, wherein the road surface condition detector is constituted by a load detector provided on a vehicle body mounting portion of a shock absorber constituting the suspension.