JPH08104122A - Suspension control device - Google Patents

Abstract

PURPOSE: To always provide the appropriate damping force in a suspension control device by compensating change of damping coefficient due to the temperature of working oil of a hydraulic shock absorber. CONSTITUTION: A suspension spring 3 and a hydraulic shock absorber 4 are interposed between the body 1 of a vehicle and a wheel 2. Vibration of the body 1 is detected by an acceleration sensor 6 fitted to the body 1, an objective damping coefficient is computed at real time by means of a controller 7 based on the detected signal, drive of the actuator of the hydraulic shock absorber 4 is controlled so as to adjust damping force, and hence damping and posture control of the body are carried out. Control gains for high temperature and low temperature K=K1 , K2 are set by a temperature compensation circuit 9 based on the detected signal of a temperature sensor 8 fitted to the hydraulic shock absorber 4, change of damping coefficient due to temperature change of the working coil of the hydraulic shock absorber 4 is compensated by correcting the control signal of the controller 7, and hence appropriate damping force is always provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension controller for controlling a damping force of a hydraulic shock absorber interposed between a vehicle body side and a wheel side of a vehicle such as an automobile by a controller.

[0002] The suspension system of an automobile includes a vehicle body side (spring)
Between the wheel and the wheel side (Unsprung), a suspension spring and a damping force adjustment type hydraulic shock absorber (hereinafter referred to as hydraulic shock absorber) arranged in parallel are provided to drive the damping force adjustment valve of the hydraulic shock absorber. There is a suspension control device in which an actuator to be controlled is controlled by a controller.

In this type of suspension control device, the actuator is controlled by the controller on the basis of vehicle acceleration, vehicle height, road surface condition, running condition, driver's selection, etc. detected by various sensors provided in the vehicle, By appropriately adjusting the damping force of the hydraulic shock absorber, vertical vibration of the vehicle body and posture control are performed to improve riding comfort and steering stability.

An example of such a suspension control device is disclosed in Japanese Patent Laid-Open No. 5-330325.

[0005]

By the way, in the above-mentioned conventional suspension control device, when adjusting the damping force of the hydraulic shock absorber, the controller controls the vehicle acceleration,
Output signal to the actuator obtained by calculating the target damping force (damping coefficient) based on the vehicle height, road condition, running condition, driver's selection, etc., and multiplying this by a preset constant control gain. The damping force of the hydraulic shock absorber is adjusted by.

In general, this control gain is assumed to be a normal operating state of the hydraulic shock absorber (a state in which the temperature of the hydraulic oil rises to some extent due to the operation), and a desired damping force can be obtained in this state. Has been decided.

Therefore, immediately after the vehicle starts running, etc., when the oil temperature of the hydraulic shock absorber is low, the viscosity of the hydraulic oil is high, so the damping force actually generated by the hydraulic shock absorber is higher than the target value. Become power. For this reason, there arises a problem that the riding comfort is deteriorated.

The present invention has been made in view of the above points, and a suspension control device that can always obtain an appropriate damping force by compensating for a change in the damping force of the hydraulic shock absorber due to the temperature of the hydraulic oil. The purpose is to provide.

[0009]

In order to solve the above problems, the present invention provides a damping force adjusting valve of a damping force adjusting hydraulic shock absorber interposed between a vehicle body side and a wheel side of a vehicle. In a suspension control device in which an actuator to be switched is controlled by a controller to obtain a desired damping force, the controller controls the damping force when the temperature is low according to the temperature of the hydraulic oil of the damping force adjustable hydraulic shock absorber. The force adjusting valve is characterized by comprising temperature compensating means for correcting the output signal to the actuator so as to increase the damping coefficient when the damping coefficient is small and the temperature is high.

[0010]

With this construction, the temperature compensating means corrects the output signal to the actuator in accordance with the temperature of the hydraulic oil, and when the temperature is low, the damping coefficient of the damping force adjusting valve is made small and When becomes high, the damping coefficient is increased to always obtain an appropriate damping force regardless of the temperature state of the damping force adjusting hydraulic shock absorber.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS. 1 to 8. FIG. 1 is a diagram showing the entire suspension control device, and for convenience, shows only one wheel of the vehicle.

In FIG. 1, reference numeral 1 is a vehicle body (sprung) of the vehicle, and 2 is wheels (unsprung).
A suspension spring 3 (compression spring) and a hydraulic shock absorber 4 are arranged in parallel with each other between the side and the wheel 2 side. In FIG. 1, 5 indicates a road surface.

An acceleration sensor 6 for detecting the vertical acceleration is attached to the vehicle body 1, and the acceleration sensor 6 is connected to a controller 7. Then, the controller 7 performs a predetermined calculation based on the detection signal from the acceleration sensor 6 to appropriately set the target value C of the damping force (damping coefficient) of the hydraulic shock absorber 4 to determine the damping force of the hydraulic shock absorber 4. A control signal is output to an actuator (not shown) that drives the regulating valve.

A temperature sensor 8 is attached to the hydraulic shock absorber 4, and the temperature sensor 8 is connected to a temperature compensation circuit 9 (temperature compensation means) of the controller 7. And
The temperature compensating circuit 9 corrects the target value of the damping coefficient based on the detection signal from the temperature sensor 8 so as to compensate for the change in the damping force due to the temperature of the hydraulic shock absorber 4.

Next, a specific structure of the hydraulic shock absorber 4 will be described.

As shown in FIG. 2, the hydraulic shock absorber 4 is divided into a cylinder 10 into an oil chamber 12 in which an oil liquid is sealed by a free piston 11 and a gas chamber 13 in which a high pressure gas is sealed. The oil chamber 12 is divided into two chambers, an upper chamber 12a and a lower chamber 12b, by a piston 14 slidably fitted in the cylinder 10, and a piston rod 15 is connected to the piston 14 and One end extends to the outside of the cylinder 10 through the upper chamber 12a.

The piston 14 is provided with an extension side passage 16 and a contraction side passage 17 which connect the upper and lower chambers 12a and 12b. When the oil liquid in the upper chamber 12a reaches a predetermined pressure during the extension stroke of the piston rod 15, the extension side passage 16 is opened to allow the oil liquid to flow from the upper chamber 12a side to the lower chamber 12b side. A normally-closed extension-side valve 18 is provided to generate a damping force having a valve characteristic. In addition, in the contraction side passage 17, when the oil liquid in the lower chamber 12b reaches a predetermined pressure during the contraction stroke, the valve is opened to allow the oil liquid to flow from the lower chamber 12b side to the upper chamber 12a side. A normally-closed compression-side valve 19 for generating a characteristic damping force is provided.

The piston 14 further includes upper and lower chambers 12a and 12a.
An extension-side bypass passage 20 and a contraction-side bypass passage 21 are provided to connect between b. Extension side bypass passage 20
Is provided with a check valve 22 that allows only the flow of the oil liquid from the upper chamber 12a side to the lower chamber side.
A check valve 23 that allows only the flow of the oil liquid from the lower chamber 12b side to the upper chamber 12a side is provided in the.

A disk-shaped shutter 24 is rotatably provided inside the piston 14 as a damping force adjusting valve for opening and closing the expansion-side and compression-side bypass passages 20 and 21. As shown in FIG. 3, the shutter 24 is provided with a pair of elongated holes 25 and 26 that extend in the circumferential direction so as to face the extension-side and contraction-side bypass passages 20 and 21, respectively.
The long holes 25 and 26 are opened at one end side and small at the other end side, and by rotating the shutter 24, the communication passage areas of the extension side and the contraction side bypass passages 20 and 21 become larger when one becomes smaller. Further, the shape is such that when one is increased, the other is decreased so that the other gradually increases or decreases.

An operation rod 27 is connected to the shutter 24. The operation rod 27 is inserted into the piston rod 15 to extend to the outside, and a tipping motor 28 (actuator) fixed to the piston rod 15 at the tip thereof. ) Are connected.

The shutter 24 is rotated by the stepping motor 28 to adjust the passage areas of the extension side and contraction side bypass passages 20 and 21, so that the solid line in FIG. 4 (only the orifice characteristic is shown). In addition, it is possible to obtain a damping coefficient that is a combination of different types (stretch side / shrink side: hard / soft or stretch side / shrink side: soft / hard) on the stretch side and the shrink side (FIG. 3 and See (a), (b), (c) of FIG. 4). In the suspension control device, due to such damping force characteristics,
The controller 7 can quickly obtain an accurate damping force.
It is possible to reduce the burden of.

In the hydraulic shock absorber 4, the cylinder 10 is connected to the wheel 2 side, the piston rod 15 is connected to the vehicle body 1 side, and the stepping motor 28 is connected to the controller 7.

Next, the hydraulic shock absorber 4 by the controller 7
The damping force control will be described with reference to the flowchart shown in FIG.

As shown in FIG. 5, when the engine of the vehicle is started (ignition switch is turned on) and the controller 9 is energized, the control software is executed from step S1 and the control flow is started.

First, in step S2, the controller 7 is initialized. Next, in step S3, it is determined whether the control cycle t has elapsed. If the control period t has not elapsed (No), the process returns to the upstream, and if the control period t has elapsed (Yes), the process proceeds to step S4.

In step S4, the damping force control signal calculated in step S8, which will be described later, is output in the previous control cycle t to drive the stepping motor 28, and the process proceeds to step S5. In step S5, other outputs such as output of signals to various indicators are performed, and the process proceeds to step S6. In step S6,
The detection signal is read from each sensor such as the acceleration sensor 6 and the temperature sensor 8, and the process proceeds to step S7.

In step S7, based on the detection signal from the temperature sensor 8, the temperature compensation circuit 9 sets the control gain K corresponding to the temperature change of the damping coefficient of the hydraulic shock absorber 4, and the process proceeds to step S8.

In step S8, the target value of the damping force (damping coefficient) of the hydraulic shock absorber 4 is calculated based on the detection signals of the respective sensors read in step S6, and the control gain K set in step S7 is multiplied. A control signal in which a change in the damping force due to the temperature of the hydraulic shock absorber 4 is corrected is calculated.

Next, the control flow of the temperature compensation subroutine of the hydraulic shock absorber 4 in step S7, which is the main part of the present invention, will be described with reference to the flowchart shown in FIG.

As shown in FIG. 6, the control flow is started from the step, and at the step, based on the detection signal of the temperature sensor 8 read at step S7 of the main routine, the actual temperature of the hydraulic shock absorber 4 (hydraulic oil Temperature) is equal to or higher than the setting T ₁ or not. If the temperature of the hydraulic shock absorber 4 is equal to or higher than the set temperature T ₁ (yes), proceed to the step, set the control gain K = K ₁ for high temperature, and if the temperature is lower than the set temperature T ₁ (no), proceed to the step. Then, the control gain K = K ₂ for low temperature is set, the process returns to the main routine (step), and the process proceeds to step S8.

Next, the control gain K for high temperature and low temperature
(= K ₁ , K ₂ ) will be described.

As shown in FIG. 7, the relationship between the temperature of the hydraulic oil of the hydraulic shock absorber 4 and the viscosity is such that the viscosity is high at low temperatures and decreases at higher temperatures, and is substantially stable above a certain temperature. Become. On the other hand, the pressure loss of the viscous fluid when passing through the fixed orifice is proportional to the viscosity of the fluid. Therefore, the damping force (damping coefficient) by the orifice of the hydraulic shock absorber 4 becomes larger at low temperature than at normal temperature (high temperature) when the hydraulic shock absorber is in a normal operating state, and the damping force characteristic is shown in FIG. As shown (only the damping force characteristic on the extension side when the shutter 24 is fixed is shown), the inclination of the orifice characteristic becomes large. As a result, a large damping force is generated when the temperature is low compared to when the temperature is high.

Paying attention to this point, the control gain K for low temperature K
₂ is set so that the damping coefficient of the hydraulic shock absorber 4 becomes smaller than the control gain K ₁ for high temperature. And
By setting the set temperature T ₁ that serves as a reference for switching between high temperature and low temperature to a temperature near the temperature at which the hydraulic oil has a stable viscosity, it is possible to effectively prevent an increase in damping force at low temperatures.

The operation of this embodiment having the above-mentioned structure will be described below.

A vibration component generated by the unevenness of the road surface while the vehicle is running is input from the wheel 2 and transmitted to the vehicle body 1 via the suspension spring 3 and the hydraulic shock absorber 4 to vibrate the vehicle body. This vibration is detected by the acceleration sensor 6 attached to the vehicle body 1, and the controller 7 is detected based on this detection signal.
The target damping coefficient is calculated in real time, and the drive of the stepping motor is controlled to adjust the damping force of the hydraulic shock absorber 4 to perform damping and attitude control of the vehicle body.

At this time, the temperature compensating circuit 9 of the controller 7 sets the control gain K according to the temperature of the hydraulic shock absorber 4 (operating oil temperature) and corrects the control signal to the stepping motor 28, thereby changing the temperature. The appropriate damping force can always be obtained by compensating for the change in the damping coefficient of the hydraulic shock absorber. As a result, immediately after the vehicle starts running,
When the temperature of the hydraulic shock absorber 4 is low, the control gain K ₂ for low temperature is set to prevent an increase in damping force,
Further, in a normal temperature state in which the temperature of the hydraulic shock absorber 4 is high, by setting the control gain K ₁ for high temperature, it is possible to prevent the decrease of the damping force and improve the riding center and the steering stability.

Next, the second embodiment of the present invention will be described with reference to FIG.
And it demonstrates with reference to FIG. The second embodiment is
The configuration is generally the same as that of the first embodiment except that the means for detecting and determining the temperature of the hydraulic shock absorber 4 is different, and the control flow of the controller is also the same.
Since it is the same except that the flow of the subroutine for setting the control gain is different, the same parts as those in the first embodiment are designated by the same reference numerals, and only different parts will be described in detail.

As shown in FIG. 9, in the suspension controller according to the second embodiment, a vehicle speed sensor 29 is provided instead of the temperature sensor 8 of the first embodiment shown in FIG.
The vehicle speed sensor 29 is connected to the temperature compensation circuit 30 of the controller 7. The temperature compensation circuit 30 is a vehicle speed sensor.
Based on the detection signal from 29, the target value of the damping coefficient is corrected so as to compensate the change in the damping force due to the temperature of the hydraulic shock absorber 4.

Next, the control flow for setting the control gain K by the temperature compensation circuit 30 of the controller 7 will be described with reference to the flowchart of FIG.

As shown in FIG. 10, the control flow is started from the step, and at the step, the traveling distance from the time when the controller 7 is energized to the present based on the detection of the vehicle speed sensor 29 read at step S7 of the main routine is shown. Accumulate and proceed to the step. In step, it is determined whether or not the traveling distance integrated in step is equal to or greater than the set value L ₁ . If the total traveled distance is greater than or equal to the set value L ₁ (yes), proceed to step to set the control gain K = K ₁ for high temperature, and if less than the set value L ₁ (no), proceed to step to low temperature. After setting the control gain K = K ₂ for the control, the process returns to the main routine (step) and proceeds to step S8.

In this way, the control gain K (= K ₁ , K ₂ ) is set by judging the temperature state of the hydraulic shock absorber 4 on the basis of the correlation between the integrated travel distance and the temperature rise of the hydraulic shock absorber 4. By doing so, similarly to the first embodiment, it is possible to compensate for the change in the damping coefficient of the hydraulic shock absorber 4 due to the temperature and always obtain an appropriate damping force.

Next, the third embodiment of the present invention will be described with reference to FIG.
And it demonstrates with reference to FIG. In addition, in the third embodiment,
The configuration is generally the same as that of the first embodiment except that the means for detecting and determining the temperature of the hydraulic shock absorber 4 is different, and the control flow of the controller is also the same.
Since it is the same except that the flow of the subroutine for setting the control gain is different, the same parts as those in the first embodiment are designated by the same reference numerals, and only different parts will be described in detail.

As shown in FIG. 11, in the suspension control device according to the third embodiment, a vehicle height sensor 31 is provided instead of the temperature sensor 8 of the first embodiment shown in FIG.
The vehicle height sensor 31 is connected to the temperature compensation circuit 32 of the controller 7. Then, the temperature compensation circuit 32 is a vehicle height sensor.
Based on the detection signal from 31, the target value of the damping coefficient is corrected so as to compensate for the change in the damping force due to the temperature of the hydraulic shock absorber 4.

Next, the control flow for setting the control gain by the temperature compensation circuit 32 of the controller 7 will be described with reference to the flowchart of FIG.

As shown in FIG. 12, the control flow is started from the step, and in the step, the controller 7 is energized based on the detection of the vehicle height sensor 31 read in the step S7 of the main routine until the vehicle height is increased to the present. The displacement amount is integrated and the process proceeds to the step. In step, it is determined whether or not the vehicle height displacement amount integrated in step is equal to or more than a set value H ₁ . If the accumulated vehicle height displacement is greater than or equal to the set value H ₁ (yes), proceed to step K for high temperature control gain K
= K ₁ is set, and when the accumulated vehicle height displacement amount is less than H ₁ (NO), the process proceeds to step, the control gain K = K ₂ for low temperature is set, and the process returns to the main routine (step), Go to step S8.

In this way, the hydraulic shock absorber 4 is based on the correlation between the accumulated vehicle displacement and the temperature rise of the hydraulic shock absorber 4.
By setting the control gain K (= K ₁ , K ₂ ) by judging the temperature state of No. 2, the change of the damping coefficient of the hydraulic shock absorber due to the temperature is compensated similarly to the first embodiment, and an appropriate value is always obtained. A damping force can be obtained.

In the above embodiment, the control gain K is set to 2
Although the change of the damping coefficient due to the temperature of the hydraulic shock absorber 4 is compensated by switching to the stage, the present invention is not limited to this, and a larger number of control gains are set according to the temperature characteristic of the hydraulic shock absorber 4. The control gain can be continuously set and adjusted. In this case, the change in viscosity is particularly large at low temperatures, so it is advisable to decrease the damping coefficient in response to temperature changes at low temperatures, that is, as the temperature decreases.

In the above embodiment, the vibration and posture control is performed on the basis of the detection signal of the acceleration sensor 6 mounted on the vehicle body 1. However, the present invention is not limited to this, and the hydraulic pressure is controlled by the controller. As long as it controls the damping force of the shock absorber, it can also be applied to those that perform vibration and attitude control by other methods, such as those that control based on the detection signal of the vehicle height sensor. The present invention can be applied not only to the automatic force control in real time, but also to the one in which the driver operates the controller to manually switch the force.

[0050]

As described above in detail, according to the suspension control device of the present invention, the temperature compensating means for correcting the output signal to the actuator in the controller according to the temperature of the hydraulic oil of the damping force adjusting type hydraulic shock absorber. By providing
By correcting the output signal to the actuator according to the temperature of the hydraulic oil, it is possible to always obtain an appropriate damping force regardless of the temperature state of the damping force adjusting hydraulic shock absorber. as a result,
Immediately after the vehicle starts running, when the temperature of the hydraulic shock absorber is low, the damping force is prevented from increasing, and when the temperature is high, the damping force is prevented from decreasing and riding stability and steering stability are improved. It has an excellent effect that it can be done.

[Brief description of drawings]

FIG. 1 is a block diagram showing a suspension device according to a first embodiment of the present invention.

2 is a longitudinal sectional view of a damping force adjusting hydraulic shock absorber of the apparatus of FIG. 1. FIG.

3 is a plan view of a shutter of the apparatus of FIG.

4 is a diagram showing a relationship between a rotational position of a shutter and an attenuation coefficient (orifice characteristic) of the apparatus shown in FIG.

5 is a flowchart showing a control procedure by a controller of the apparatus of FIG.

6 is a flowchart showing a procedure for setting a control gain by a temperature compensation circuit of the controller of the apparatus of FIG.

FIG. 7 is a diagram showing temperature characteristics of viscosity of hydraulic oil of a hydraulic shock absorber.

FIG. 8 is a diagram showing a change in damping force characteristic of the hydraulic shock absorber with temperature of hydraulic oil.

FIG. 9 is a block diagram showing a suspension device according to a second embodiment of the present invention.

10 is a flowchart showing a procedure for setting a control gain by a temperature compensation circuit of the controller of the apparatus shown in FIG.

FIG. 11 is a block diagram showing a suspension device according to a third embodiment of the present invention.

12 is a flowchart showing a procedure for setting a control gain by a temperature compensation circuit of the controller of the apparatus shown in FIG.

[Explanation of symbols]

 1 Vehicle Body 2 Wheels 4 Damping Force Adjustable Hydraulic Shock Absorber 7 Controller 9 Temperature Compensation Circuit (Temperature Compensation Means)

Claims (1)

[Claims] 1. A controller controls an actuator for switching a damping force adjusting valve of a damping force adjusting type hydraulic shock absorber interposed between a vehicle body side and a wheel side of a vehicle to obtain a desired damping force. In the suspension control device described above, the controller reduces the damping coefficient of the damping force adjusting valve when the temperature is low and decreases the damping coefficient when the temperature is high, according to the temperature of the hydraulic oil of the damping force adjusting hydraulic shock absorber. A suspension control device comprising temperature compensating means for compensating an output signal to the actuator so as to increase the size.