JP2002195338A - Damping force controller for shock absorber, and shock absorber hydraulic oil temperature predicting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control a damping force by a shock absorber by suppressing the temperature rise of the hydraulic oil in the shock absorber. SOLUTION: A microcomputer 65 estimates a hydraulic oil temperature Te and judges an off-road traveling by a program processing, and controls the damping force of the shock absorber 10 according to the judged and estimated results. When the estimated temperature Te is less than a specified temperature or the off-road traveling is not judged, by using a sprung mass absolute acceleration detected by an acceleration sensor 61 and a sprung mass- unsprung mass relative speed detected by a stroke sensor 62, the opening of a variable restriction mechanism 50 is set to a target opening corresponding to a target number of steps determined according to the vertical motions of the sprung mass member and unsprung mass member. When the estimated temperature Te is equal to or higher than the specified temperature and the off-road traveling is judged, the target number of steps is changed to change the opening of the variable restriction mechanism 50 to a larger side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force control device for a shock absorber for controlling the damping force of a shock absorber interposed between an unsprung member and a sprung member of a vehicle, and to the shock absorber. The present invention also relates to a hydraulic oil temperature estimating device for a shock absorber for estimating a hydraulic oil temperature of a shock absorber.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Publication No.
As shown in Japanese Patent Publication No. 2 (1993), a cylinder interposed between a unsprung member and a sprung member of a vehicle and filled with hydraulic oil and divided into upper and lower chambers by a piston; And a variable throttle mechanism for changing the opening of the communication passage, and a damping force control device for a shock absorber that generates a damping force with respect to vertical vibration of a sprung member with a vertical movement of a piston with respect to a unsprung member. Estimating the temperature of the hydraulic oil of the shock absorber, and setting the drive speed of an actuator provided in the variable throttle mechanism to change the opening of the communication passage so as to increase as the estimated temperature increases. It is known to control the degree appropriately and with good responsiveness.

In this damping force control device, the vertical acceleration of the sprung member is detected, the number of zero crosses per unit time of the detected vertical acceleration is measured, and based on the measured number of zero crosses, By estimating the temperature of the hydraulic oil of the shock absorber by deriving a temperature increase that increases as the number of zero crossings increases, and adding this temperature increase to the current temperature of the hydraulic oil to update the temperature of the hydraulic oil, I have to.

[0004]

In the above-mentioned prior art, no consideration is given to suppressing a rise in the temperature of the hydraulic oil of the shock absorber.
The function of the shock absorber may not be fully exhibited. For example, when the temperature of the hydraulic oil becomes extremely high, the sealing function of the seal member disposed in each part of the shock absorber is reduced, and the malfunction of the actuator due to a change in the magnetic characteristics of the electromagnetic actuator in the variable throttle mechanism occurs. Sometimes. Further, in this type of shock absorber, when the temperature of the hydraulic oil changes, the damping coefficient changes even if the opening degree of the communication passage is the same. High damping force may not be generated. Further, in the above-described conventional temperature estimation, the temperature of the hydraulic oil is estimated based on the frequency of zero crossing of the vertical acceleration of the sprung member without considering the opening degree of the communication passage and the like. bad.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to address the above-described problems, and has as its object to suppress a rise in the temperature of the hydraulic oil of a shock absorber and to reduce the shock absorber even when the temperature of the hydraulic oil changes. It is an object of the present invention to provide a damping force control device for a shock absorber in which the control accuracy of the damping force is kept high. Another object of the present invention is to provide a hydraulic oil temperature estimating device for a shock absorber that accurately estimates the temperature of the hydraulic oil.

According to the present invention, there is provided a cylinder interposed between an unsprung member and a sprung member of a vehicle, filled with hydraulic oil and divided into upper and lower chambers by a piston, and a communication passage between the upper and lower chambers. A variable throttle mechanism for changing an opening degree, which is applied to a damping force control device for a shock absorber that generates a damping force with respect to a vertical vibration of a sprung member with respect to a unsprung member accompanied by a vertical movement of a piston. It is.

[0007] The first structural feature of the present invention is as follows.
Target opening degree determining means for determining a target opening degree of the variable throttle mechanism in accordance with a vertical motion state of a sprung member; temperature estimating means for estimating a temperature of hydraulic oil in the shock absorber; Road surface state detecting means for detecting a road surface state; target opening degree correcting means for correcting the determined target opening degree in accordance with the estimated temperature of the hydraulic oil and the detected state of the traveling road surface; Opening control means for outputting a control signal corresponding to the target opening to the variable throttle mechanism to control the opening of the communication passage to the corrected target opening.

In this case, the road surface state detecting means may be configured to detect the state of the road surface of the vehicle based on, for example, the magnitude of vibration of at least one of the sprung member and the unsprung member.

[0009] In the first structural feature configured as described above, in a situation where the temperature of the hydraulic oil of the shock absorber is high and the vehicle travels on a rough road (off-road), the target opening degree is reduced. The correcting means corrects the target opening determined by the target opening determining means based on the temperature of the hydraulic oil estimated by the temperature estimating means and the state of the traveling road surface detected by the road surface state detecting means. For example, the target opening correction means may be configured such that when the estimated temperature of the hydraulic oil is equal to or higher than a predetermined temperature and the state of the traveling road surface detected by the road surface state detection means is a bad road surface, the target opening degree is corrected. The target opening determined by the determining means is changed to a larger side, and otherwise the target opening determined is not changed.

Therefore, in a situation where the sprung member vibrates strongly against the unsprung member due to running on a rough road and the temperature of the hydraulic oil rises from a high state to a higher temperature, the sprung member is accompanied by the vibration against the unsprung member. Since the amount of heat generated by the movement of the hydraulic oil can be reduced, the temperature rise of the hydraulic oil can be suppressed. As a result, according to the first structural feature, a decrease in the sealing function of the sealing member disposed at each part of the shock absorber is suppressed, and the malfunction of the variable throttle mechanism is eliminated, so that the damping force by the shock absorber is reduced. Control can always be performed accurately.

A second structural feature of the present invention is a target damping coefficient determining means for determining a target damping coefficient of the shock absorber in accordance with a vertical motion state of a sprung member, Temperature estimating means for estimating the temperature of the hydraulic oil, and target opening degree determining means for determining a target opening degree of the variable throttle mechanism in accordance with the determined target damping coefficient and the estimated temperature of the hydraulic oil, There is provided an opening control means for outputting a control signal corresponding to the determined target opening to the variable throttle mechanism to control the opening of the communication passage to the determined target opening.

[0012] In the second structural feature configured as described above, even if the temperature of the hydraulic oil changes and the damping coefficient for the same opening changes, the target opening determining means determines the target damping coefficient. The target opening of the variable throttle mechanism is determined according to the target damping coefficient determined by the means and the temperature of the hydraulic oil estimated by the temperature estimating means. For example, the target opening degree determining means may use the data prepared in advance to represent the relationship between the temperature of the hydraulic oil, the opening degree of the communication passage, and the damping coefficient of the shock absorber, and set the damping coefficient of the shock absorber to It is configured to determine a target opening of the variable throttle mechanism so as to be set to the determined target attenuation coefficient.

Therefore, the opening degree of the variable throttle mechanism is set so that the damping coefficient of the shock absorber becomes the target damping coefficient irrespective of the temperature of the hydraulic oil. As a result, according to the second structural feature, even if the temperature of the hydraulic oil changes, the performance of the shock absorber can be sufficiently exhibited, and the control accuracy of the damping force by the shock absorber is kept high. be able to.

A third structural feature of the present invention is that speed detecting means for detecting a vertical speed of the sprung member with respect to the unsprung member, an opening degree set by the variable throttle mechanism, and A calorific value calculating means for calculating a calorific value according to the detected vertical speed; an outside air temperature detecting means for detecting an outside air temperature; and the operating oil based on the calculated calorific value and the detected outside air temperature. And a temperature calculating means for calculating the temperature of the shock absorber.

[0015] In the third structural feature configured as described above, the calorific value calculating means generates heat in accordance with the opening set by the variable throttle mechanism and the vertical speed detected by the speed detecting means. Calculate the amount. For example, the calorific value calculating means derives the damping force generated by the shock absorber according to the opening set by the variable throttle mechanism and the detected vertical speed, and calculates the damping force and the derived damping force. The heat generation amount is updated by adding the product of the detected vertical speed to the current heat generation amount.

The temperature calculating means calculates the temperature of the hydraulic oil based on the calculated calorific value and the outside air temperature detected by the outside air temperature detecting means. For example, the temperature calculation means includes a heat radiation amount calculation means for calculating a heat radiation amount using the current temperature of the hydraulic oil calculated by the temperature calculation means and the detected outside air temperature; and Subtracting means for calculating the temperature of the hydraulic oil by subtracting the calculated heat release amount.

Therefore, according to the third structural feature, in the calculation of the heat generation amount, the opening degree of the communication passage and the vertical speed of the sprung member are considered. More specifically, the calorific value is calculated in consideration of the damping force generated by the shock absorber and the power determined according to the vertical speed of the sprung member. Further, the heat radiation amount is calculated in consideration of the current temperature of the hydraulic oil and the detected outside air temperature, and the temperature of the hydraulic oil is estimated in consideration of the heat generation amount and the heat radiation amount. Is accurately estimated.

Further, in the third structural feature, a vehicle speed detecting means for detecting a speed of the vehicle is added, and the heat radiation amount calculating means is provided in accordance with the detected speed of the vehicle. Preferably, the heat radiation amount calculated using the temperature and the outside air temperature is corrected.

According to this, it is considered that the cooling by the outside air, that is, the amount of heat released to the outside air changes according to the speed of the vehicle, so that the temperature of the hydraulic oil can be more accurately estimated.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a vehicle shock absorber and an electric control device thereof according to the embodiment.

The shock absorber 10 includes a lower arm 21 (unsprung member) connected to a wheel 20 (unsprung member).
The shock absorber 10 is provided with a spring 40 in parallel with the vehicle body 30 (a sprung member). The shock absorber 10 has a lower end connected to the lower arm 21 and a cylinder 11 in which hydraulic oil is sealed. The cylinder 11 is divided into upper and lower chambers R1 and R2 by a piston 12 which slides on the inner peripheral surface in a liquid-tight manner. The piston 12 has a piston rod 13
Is connected to the vehicle body 30 via the

A variable throttle mechanism 50 is mounted on the piston 12. The variable aperture mechanism 50 includes a step motor 51 as an electric actuator that constitutes a part thereof.
Thereby, the opening degree of the communication path for communicating between the upper and lower chambers R1 and R2 of the cylinder 11 is switched to a plurality of stages (hereinafter, the number of stages corresponding to the plurality of stages is referred to as a step number P). The number of steps P is the minimum number of steps Pmin and the maximum number of steps Pm
It is set between the step numbers Pmin to Pmax defined by ax, and the opening degree of the communication path increases as the step number increases, that is, the shock absorber 10 is set from the hard side to the soft side. means.

The electric control device includes an acceleration sensor 61, a stroke sensor 62, a vehicle speed sensor 63, and an outside air temperature sensor 6.
4 is provided. The acceleration sensor 61 is assembled to a member on the vehicle body 30 side near the wheel 20 and detects an acceleration in a vertical direction of the vehicle body 30 with respect to an absolute space (hereinafter, referred to as a sprung absolute acceleration) Xbdd. The sprung absolute acceleration Xbdd represents an upward acceleration by a positive value, and represents a downward acceleration by a negative value. Stroke sensor 6
Numeral 2 is assembled between the vehicle body 30 and the lower arm 21 to detect a vertical relative displacement amount (hereinafter, referred to as a sprung-unsprung relative displacement amount) Xs of the vehicle body 30 with respect to the wheel 20 and the lower arm 21. . Note that the sprung-unsprung relative displacement Xs is a positive value that increases from a reference value (the upward displacement of the piston 12 and the piston rod 13 with respect to the cylinder 11, that is, the shock absorber 1).
0 indicates a displacement amount on the extension side, and a negative value indicates a decrease amount from the reference value (a displacement amount of the piston 12 and the piston rod 13 with respect to the cylinder 11 in a downward direction, that is, a displacement amount of the shock absorber 10 on a contraction side). . Vehicle speed sensor 63
Detects the running speed (vehicle speed) V of the vehicle. The outside air temperature sensor 64 detects the outside air temperature Ta.

Each of these sensors 61 to 64 is connected to a microcomputer 65. The microcomputer 65 repeatedly executes the damping force control program of FIG. 2 and the oil temperature estimation program of FIG. 6 every predetermined short time under the control of a built-in timer, and
While controlling the opening degree of 0, the temperature Te of the hydraulic oil in the cylinder 11 is estimated. This microcomputer 65
Is connected to a drive circuit 66 that controls the rotation of the step motor 51 according to a control signal from the computer 65.

Next, the operation of the embodiment configured as described above will be described. After turning on an ignition switch (not shown), the microcomputer 65 repeatedly executes the damping force control program of FIG. 2 every predetermined short time. The execution of this program is started in step S10,
In step S12, the sprung absolute acceleration Xbdd and the sprung-unsprung relative displacement Xs are input from the acceleration sensor 61 and the stroke sensor 62, and the vehicle speed sensor 63
The vehicle speed V is input from. After the processing in step S12,
In step S14, a target step number calculation routine for determining a target opening degree (corresponding to the target step number Pd) of the variable throttle mechanism 50 is executed, and in step S16, a state of a traveling road surface of the vehicle is determined. Execute the offload determination routine.

The execution of the target step number calculation routine is started in step S100 in FIG. 3, and is executed in step S102.
In the above, the sprung absolute speed Xbd representing the absolute vertical speed of the vehicle body 30 is calculated by integrating the inputted sprung absolute acceleration Xbdd. Next, step S
At 104, the inputted sprung-unsprung relative displacement X
By differentiating s, a sprung-unsprung relative speed Xsd representing a vertical speed relative to the wheel 20 and the lower arm 21 of the vehicle body 30 is calculated.

Next, at step S106, it is determined whether or not the product of the sprung absolute speed Xbd and the sprung-unsprung relative speed Xsd is positive.
It is determined whether 0 is in a vibration suppression state or a vibration state. The vibration state refers to a state in which the vehicle body 30 is pushed up or down due to unevenness of the traveling road surface. In this state, the sprung absolute speed Xbd and the sprung-unsprung relative speed Xsd are opposite to each other. Sign. Further, the vibration damping state means that the vehicle body 30 is
In this state, the sprung absolute speed Xbd and the sprung-unsprung relative speed Xsd have the same sign.

If the shock absorber 10 is in the vibrating state, "NO" is determined in step S106, and the target step number Pd is set to the maximum step number Pmax in step S108. This is because when the shock absorber 10 is in the vibrating state, the shock absorber 10 is set to be soft, so that the vehicle body 30 described above can be used.
This is to avoid a large push-up and pull-down.

On the other hand, if the shock absorber 10 is in the vibration damping state, "YES" is determined in step S106, and the target step number Pd is determined by the processing in steps S110 and S112. These steps S112,
The processing of S114 is for determining the target number of steps Pd based on the well-known skyhook theory.
2, the target damping force Fd is calculated by multiplying the predetermined skyhook coefficient Csk by the sprung absolute speed Xbd. Next, in step S112, the target number of steps Pd corresponding to the sprung-unsprung relative speed Xsd and the target damping force Fd is determined with reference to a damping force table prepared in advance in the microcomputer 65.

This damping force table is provided for each step P (Pmin to Pmax) of the shock absorber 10.
The relationship between the unsprung relative speed Xsd and the damping force F is obtained by actual measurement or simulation, and as shown in the characteristic graph of FIG. Number of steps P (Pmin ~ Pm
ax) is stored in the form of a table. Therefore, in the process of step S112, the number of steps Pk having a characteristic curve closest to the position on the graph of FIG. 4 determined by the calculated sprung absolute speed Xbd and the target damping force Fd is set as the target step number Pd. You. In the present embodiment, the target step number Pd is determined based on the skyhook theory.
The target step number Pd for damping the vibration of the vehicle body 30 may be determined by another method according to the vertical motion state of the vehicle body 30. Step S10
After the processing of steps S8 and S112, the execution of the target step number calculation routine is terminated in step S114.

Next, the offload determination routine of step S16 in FIG. 2 will be described. This off-road determination routine is started in step S200 in FIG.
In step S202, the unsprung absolute acceleration Xadd used as an index for off-road determination is calculated together with the sprung absolute acceleration Xbdd. Specifically, step S12
The second order differentiation of the sprung-unsprung relative displacement amount Xs input in step 2 is performed, and the sprung-unsprung relative acceleration Xsdd (= d ² Xs / dt ² )
And the calculated sprung-unsprung relative acceleration Xsdd
To a frequency component near the resonance frequency of the unsprung member (for example,
10 to 13 Hz), and a band-pass filter process is performed to calculate an unsprung absolute acceleration Xadd. Regarding the sprung absolute acceleration Xbdd, the sprung absolute acceleration Xbdd subjected to the band-pass filter processing for extracting a frequency component near the resonance frequency of the sprung member is calculated in step S2 described later.
08 and S228 may be used as an index for off-road determination.

After the process in step S202, it is determined in step S204 whether the offload flag OFF is "0". The off-road flag OFF indicates the state of the traveling road surface, and indicates a flat road by "0" and "1".
Represents a rough road with a lot of unevenness, that is, off-road. now,
If the offload flag OFF is set to “0”, “YES” is determined in the step S204, and the step S204 is performed.
Proceeding to 206, it is determined whether the vehicle speed V is equal to or lower than the predetermined vehicle speed V0. The process of step S206 is one condition for determining off-road travel because it is not possible to run at high speed when the vehicle is traveling off-road. Therefore, if the vehicle speed V is higher than the predetermined vehicle speed V0, "NO" is determined in the step S206, and the execution of the offload determination routine is ended in the step S224 while keeping the offload flag OFF at "0". I do.

On the other hand, if the vehicle speed V is equal to or lower than the predetermined vehicle speed V0, "YES" is determined in step S206, and the sprung absolute acceleration Xbdd is determined in steps S208 and S210.
Xbdd |, | X
It is determined whether add | is greater than or equal to predetermined values X01 and X02, respectively. If the absolute values | Xbdd | and | Xadd | are less than the predetermined values X01 and X02, respectively, both steps S20
In both steps S210 and S210, “NO” is determined, and the execution of the offload determination routine is terminated in step S224 while the offload flag OFF is maintained at “0”. Also,
If the absolute value | Xbdd | is equal to or greater than a predetermined value X01, or if the absolute value | Xadd | is equal to or greater than a predetermined value X02, it is determined "YES" in either step S208 or S210, and the process proceeds to step S212. move on.

In step S212, it is determined whether the timer count value TM1 is larger than "0".
The timer count value TM1 is set to a predetermined value TM10 (> 0) by the process of step S214, and is then down-counted by a predetermined value until it becomes "0" or less by a program process (not shown). It is used for measuring the time corresponding to. now,
If the timer count value TM1 is equal to or smaller than "0", "NO" is determined in the step S212, and the timer count value TM1 is set to a predetermined value TM10 in a step S214.
After the process of step S214, when the offload determination routine is newly executed, "YES" is determined in step S212, that is, the timer count value TM1 is determined to be greater than "0", and the frequency count value CNT1 is determined in step S216. “1” is added, and the process proceeds to step S218. The frequency count value CNT1 is set to "0" by an initialization process (not shown) when the ignition switch is turned on.

In step S218, it is determined whether the frequency count value CNT1 is equal to or greater than a predetermined value CNT10. If the frequency count value CNT1 is less than the predetermined value CNT10, "NO" is determined in the step S218, and the step S22 is performed while keeping the offload flag OFF at "0".
At 4, the execution of the offload determination routine is temporarily terminated. If the frequency count value CNT1 is equal to or larger than the predetermined value CNT10, "YES" is determined in the step S218, and the offload flag OFF is changed to "1" in a step S220. Then, in step S222, the timer count value T
M1 and the frequency count value CNT1 are each returned to "0", and the execution of the offload determination routine is temporarily ended in step S224.

By the processing in steps S204 to S222, the vehicle speed V is equal to or less than the predetermined vehicle speed V0, and the absolute value | Xbdd | of the sprung absolute acceleration Xbdd is equal to or greater than the predetermined value X01 or the absolute value | Xadd of the unsprung absolute acceleration Xadd. | Is the predetermined value X02
If the above condition is satisfied a predetermined number of times (corresponding to the predetermined value CNT10) within the time corresponding to the predetermined value TM10, the offload flag OFF is changed to "1". In other words, when the frequency at which the condition is satisfied is higher than the predetermined frequency, the offload flag OFF is changed to "1".

In this way, the offload flag is turned off.
Is set to "1", "N" is set in step S204.
O "is determined, and the process proceeds to step S226 and subsequent steps. In step S226, it is determined whether the vehicle speed V is higher than a predetermined vehicle speed V0. In step S228, it is determined whether the absolute value | Xbdd | of the sprung absolute acceleration Xbdd is less than a predetermined value X01. In step S230, it is determined whether the absolute value | Xadd | of the unsprung absolute acceleration Xadd is less than a predetermined value X02. The vehicle speed V is higher than the predetermined vehicle speed V0, the absolute value | Xbdd | of the sprung absolute acceleration Xbdd is less than the predetermined value X01, and the absolute value | Xadd | of the unsprung absolute acceleration Xadd is less than the predetermined value X02. Only when all three conditions are satisfied, step S2
It is determined "YES" in all of steps 26 to S230, and the process proceeds to step S232 and subsequent steps. If any one of the three conditions is not satisfied, it is determined as “NO” in any of steps S226 to S230, and the off-road flag is turned off.
In step S224, the execution of the offload determination routine is temporarily terminated while keeping the value of "1".

Steps S232 to S238 are similar to steps S212 to S218 described above.
The timer count value TM2, the frequency count value CNT2 and the predetermined values TM20 and CNT20 are the same as the timer count value T described above.
M1, frequency count value CNT1, and predetermined values TM10, CNT
It corresponds to 10. As a result, the vehicle speed V is equal to or higher than the predetermined vehicle speed V0, and the absolute value | X of the sprung absolute acceleration Xbdd is obtained.
bdd | is less than a predetermined value X01 and the absolute value | Xadd | of the unsprung absolute acceleration Xadd is less than a predetermined value X02. If the above conditions are satisfied, the offload flag OFF is changed to "0". In other words,
When the frequency at which the above three conditions are satisfied is higher than a predetermined frequency,
The offload flag OFF is changed to "0". On the other hand, if the above three conditions are not satisfied a predetermined number of times (corresponding to the predetermined value CNT20) within the time corresponding to the predetermined value TM20, the offload flag OFF is kept set to "1".

As a result, the off-road flag OFF is set to "1" by the off-road determination routine when the vehicle is traveling on a rough road (off-road) having a lot of unevenness on the road surface. On the other hand, when the vehicle is traveling on a flat road, the off-road flag OFF is set to "
It is kept at 0 ".

Returning to the description of the damping force control program in FIG. 2, after the execution of the off-load determination routine in step S16, the current estimated oil temperature Te is set to a predetermined high predetermined temperature To in step S18. It is determined whether or not this is the case.

Here, a method of deriving the current estimated temperature Te will be described. This estimated temperature Te is derived by executing the oil temperature estimation program of FIG.
This program is repeatedly executed every predetermined short time in parallel with the damping force control program from the time the ignition switch is turned on.

The execution of the oil temperature estimating program is started in step S30, and in step S32, the sprung-unsprung relative displacement Xs, the vehicle speed V and the vehicle speed are obtained from the stroke sensor 62, the vehicle speed sensor 63 and the outside air temperature sensor 64. The outside air temperature Ta is input. In step S34, the input sprung-unsprung relative displacement amount Xs is differentiated with respect to time to obtain a sprung-unsprung relative speed Xsd (= dXs / dt).
Is calculated.

Next, in step S36, the variable throttle mechanism 50 is referred to by referring to the aforementioned damping force table (see FIG. 4).
, The damping force F currently generated by the shock absorber 10 is derived from the current step number P and the sprung-unsprung relative speed Xsd. In this case, the current number of steps P is
By the processing in step S24 described later, the variable aperture mechanism 5
This is set at the time of opening control of 0.

After the processing in step S36, step S
At 38, the current damping force F is added to the calorific value Q1 calculated last time.
The current calorific value Q1 is updated by the calculation of the following expression 1 in which the product of the sprung-unsprung relative speed Xsd is added. Equation 1 corresponds to calculating the heat value Q1 (= ∫F · Xsd · dt) by an integration operation for integrating the heat rate F · Xsd.

[0045]

[Equation 1] Q1 = Q1 + F.Xsd

The product F · Xsd of the damping force F and the sprung-unsprung relative speed Xsd in the above equation (1) corresponds to the power (work per unit time) accompanying the displacement of the piston 12. The heat value Q1 is initially set to "0" by a program process (not shown) at the time of ignition (when the ignition is turned on). By executing the calculation of Equation 1, the power of the shock absorber 10 (piston 12) is integrated, and the calorific value of the shock absorber 10 is calculated.

Next, at step S40, a heat radiation coefficient K1 corresponding to the vehicle speed V is derived by referring to the heat radiation coefficient table. In this heat dissipation coefficient table, the heat dissipation coefficient K1 that changes according to the vehicle speed V is obtained by actual measurement or simulation, and the value of the heat dissipation coefficient K1 with respect to the vehicle speed V is stored in the form of a table as shown in the characteristic graph of FIG. Things. Note that, as the vehicle speed V increases, the cooling effect of the hydraulic oil improves, so that the radiation coefficient K2 increases as the vehicle speed V increases. Then, in step S42, the current heat release amount Q2 is calculated by multiplying the result obtained by subtracting the input outside air temperature Ta from the previously calculated hydraulic oil estimated temperature Te by the derived heat release coefficient K1 and the following equation (2). Update. The estimated temperature Te in the following equation (2) is initially (when the ignition is turned on) the outside air temperature Ta detected by the outside air temperature sensor 64 by a program process (not shown).
Is set to

[0048]

[Equation 2] Q2 = K1 · (Te−Ta)

After the processing in step S42, step S
In step 44, the current estimated temperature Te of the hydraulic oil is calculated by executing the calculation of the following equation 3 in which the heat release amount Q2 is subtracted from the calculated heat release amount Q1, and the execution of the oil temperature estimation routine is ended in step S46. I do. The coefficients K2 and K3 are predetermined constants.

[0050]

[Equation 3] Te = K2 · Q1-K3 · Q2

In such an oil temperature estimation routine,
The calorific value Q1 is calculated in consideration of the damping force F generated by the shock absorber 10 and the power determined by the sprung-unsprung relative speed Xsd, and the current operating oil temperature Te and the outside air temperature Ta. Thus, the heat release amount Q2 is calculated. Then, the estimated temperature Te of the hydraulic oil is calculated based on the heat generation amount Q1 and the heat release amount Q2, so that the estimated temperature Te is accurately calculated.

Further, since the cooling by the outside air, that is, the heat radiation amount Q2 to the outside air is calculated in consideration of the vehicle speed V using the heat radiation coefficient K1, the heat radiation amount Q2 is accurately calculated, and the estimated temperature Te is also accurately calculated. Well calculated. In the present embodiment, the heat radiation coefficient K1 is changed according to the vehicle speed V. However, if some error is allowed, the heat radiation coefficient K1 may be a constant.

Returning to the explanation of the damping force control program in FIG. 2, if the estimated temperature Te calculated by executing the oil temperature estimating program is lower than the predetermined temperature To, it is determined "NO" in step S18. Then, the process proceeds to step S24. In step S24, a control signal for controlling the number of steps of the variable aperture mechanism 50 to be the target step number Pd determined in the target step number calculation routine of step S14 is output to the drive circuit 66. In this step S24, the variable aperture mechanism 50
Is updated to the target step number Pd.

In response to the control signal, the drive circuit 66 controls the rotation of the step motor 51 to a rotational position corresponding to the target step number Pd. Step motor 51
Sets the number of steps P (corresponding to the opening) of the variable throttle mechanism 50 to the target number of steps Pd. As a result, the opening degree of the variable throttle mechanism 50 is set to the target opening degree corresponding to the target step number Pd, and a damping force corresponding to the target opening degree is generated to suppress the vibration of the vehicle body 30.

If the estimated temperature Te is equal to or higher than the predetermined temperature To, "YES" is determined in the step S18, and the process proceeds to a step S20. In step S20, it is determined whether or not an offload flag OFF indicating a determination result obtained by executing the offload determination routine in step S16 is "1". In this case, if the vehicle is not traveling off-road and the off-road flag OFF is "0",
In step S20, "NO" is determined, and step S24
In the same manner as described above, the number of steps of the variable throttle mechanism 50 is set and controlled to the target step number Pd calculated by the target step number calculation routine in step S14.

On the other hand, if the estimated temperature Te is equal to or higher than the predetermined temperature To and the vehicle is running off-road and the off-road flag OFF is "1", both steps S18 and S18 are performed.
At 20, both are determined to be “YES,” and the process proceeds to step S 22. In step S22, the target step number Pd is changed to the maximum step number Pmax,
To set and control the number of steps P of the variable aperture mechanism 50 to the target number of steps Pd (maximum number of steps Pmax). And
In step S26, the execution of the damping force control program ends once. Thus, in this state, the variable aperture mechanism 5
The opening degree of 0 is set to the maximum, that is, the damping coefficient of the shock absorber 10 is set to the minimum damping coefficient (the softest).

As can be understood from the above description of operation, according to the above embodiment, when the estimated temperature Te of the hydraulic oil is equal to or higher than the predetermined temperature To and the vehicle is traveling on an off-road (bad road). , The opening of the variable throttle mechanism 50 is set to the maximum. Therefore, the vehicle 3
In a situation where the vibration of the zero wheel 20 and the lower arm 21 is severe and the temperature of the hydraulic oil is further increased from a high state, the amount of heat generated by the movement of the hydraulic oil accompanying the movement of the piston 12 can be suppressed to a small value. In addition, a rise in the temperature of the hydraulic oil can be suppressed. As a result, a reduction in the sealing function of the sealing members disposed at various parts of the shock absorber 10 is suppressed, and the operation of the step motor 51 is eliminated, so that the control of the damping force by the shock absorber 10 can always be accurately performed. .

Next, a description will be given of a modification in which the method of calculating the target number of steps in the above embodiment is modified. In this modification, as shown in FIG. 8, the processing of steps S110 and S112 of the target step number calculation routine of FIG.
120 and S122. Other parts are the same as in the above embodiment.

In step S120, the predetermined skyhook damping coefficient Csk, the sprung absolute speed Xbd calculated in the process of step S102, and the sprung-unsprung relative speed Xsd calculated in the process of step S104 are used. The target damping coefficient Cd of the shock absorber 10 based on the skyhook theory is calculated by executing the following equation (4).

[0060]

## EQU4 ## Cd = Csk.Xbd / Xsd

In step S122, referring to the damping coefficient table prepared in advance in the microcomputer 65, the estimated temperature Te calculated by the oil temperature estimating program described above and the calculated target damping coefficient Cd are corresponded. The target step number Pd is determined. This damping coefficient table is stored in each step P of the shock absorber 10.
(Pmin to Pmax) for each operating oil temperature Te and damping coefficient C
Is obtained by actual measurement or simulation, and as shown in the characteristic graph of FIG.
The value of the damping coefficient C with respect to step P (Pmin to Pm
ax) is stored in the form of a table. Therefore, in the process of step S122, the number of steps Pk having the characteristic curve closest to the position on the graph of FIG. 9 determined by the calculated estimated temperature Te and the target attenuation coefficient Cd is set as the target number of steps Pd.

Therefore, according to this modification, the opening degree of the variable throttle mechanism 50 is set so that the damping coefficient C of the shock absorber 10 becomes the target damping coefficient Cd irrespective of the temperature of the hydraulic oil. Even if the temperature of the hydraulic oil changes, the performance of the shock absorber 10 can be sufficiently exhibited, and the control accuracy of the damping force by the shock absorber 10 can be kept high. In this modification, the target damping coefficient Cd of the shock absorber 10 may be determined based on the vertical motion state of the sprung member by a method other than the method based on the skyhook theory.

In the above embodiment, the unsprung absolute acceleration Xadd is calculated based on the sprung-unsprung relative speed Xsd detected by the stroke sensor 62. However, instead of this, the lower arm 21 (unsprung member) may be assembled to an acceleration sensor, and the unsprung absolute acceleration Xadd detected by the sensor may be used. Further, a wheel speed sensor for detecting the wheel speed is provided, and the frequency near the resonance frequency of the wheel 20 (unsprung member) is added to the wheel speed detected by the sensor, its time differential value, or further its time differential value. It is also possible to apply band-pass filter processing for a pass band and use it as the unsprung absolute acceleration Xadd.

In the above embodiment, the acceleration sensor 6
By using the sprung absolute acceleration Xbdd detected by 1 and the sprung-unsprung relative displacement Xs detected by the stroke sensor 62, various physical quantities such as the speed and acceleration of the sprung and unsprung members are calculated. did. However, one of the two sensors 61 and 62 is omitted, and both sensors 61 and 62 are omitted.
Omitting both 1 and 62, the speed of the sprung and unsprung members,
A sensor for detecting another physical quantity such as acceleration may be provided, and a required physical quantity may be detected using an observer.

In the above embodiment, the vehicle speed V is detected by the vehicle speed sensor 63. However, the vehicle speed may be calculated based on the wheel speed detected by the wheel speed sensor.

In the off-road determination routine of the above embodiment, the absolute value | Xb of the sprung absolute acceleration Xbdd
Either dd | is equal to or more than a predetermined value X01 or the absolute value | Xadd | of the unsprung absolute acceleration Xadd is equal to or more than a predetermined value X02 is determined as the off-road determination condition of the vehicle. However, both that the absolute value | Xbdd | of the sprung absolute acceleration Xbdd is equal to or greater than a predetermined value X01 and that the absolute value | Xadd | of the unsprung absolute acceleration Xadd is equal to or greater than a predetermined value X02,
The off-road determination condition may be used. Further, other methods may be used as long as the off-road traveling of the vehicle can be determined.

Further, in the above-described embodiment and modified examples, the damping force table is used to derive the target step number Pd and the damping force F, the heat dissipation coefficient table is used to derive the heat dissipation coefficient K1, and the target step number Pd The damping coefficient table was used to derive. However, in these cases, instead of the tables, data other than the table indicating the relationship between various physical quantities (various parameters), for example, the relationship between the physical quantities is defined, that is, the spring for each step number P of the variable throttle mechanism is defined. The relationship between the upper-unsprung relative speed Xsd and the damping force F (see FIG. 4), the relationship between the vehicle speed V and the radiation coefficient K1 (see FIG. 7), and the hydraulic oil temperature Te for each step number P of the variable throttle mechanism. Data representing functions respectively defining the relationship with the attenuation coefficient C (see FIG. 9) is stored in the microcomputer 6 in advance.
5, the target number of steps Pd, the damping force F, and the heat radiation coefficient K1 may be derived using the same data.

In the above-described embodiment, when the estimated temperature Te of the hydraulic oil is equal to or higher than the predetermined temperature To and the vehicle is running on an off-road (bad road), the process of step S22 in FIG. Accordingly, the target step number Pd of the variable throttle mechanism 50 is set to the maximum target step number Pmax (maximum opening). However, since the present invention aims at suppressing the rise in the temperature of the hydraulic oil, in step S22, the target step number Pd set in step S14 of FIG. Value, that is, the opening degree of the shock absorber 10 is set to the target step number P set by the processing in step S14.
What is necessary is just to change to the side which becomes at least larger than the opening degree corresponding to d. In this case, for example, the higher the estimated temperature Te, the larger the target step number Pd can be changed.

Further, in the above-described embodiment and the modified example, the temperature Te of the hydraulic oil estimated by the oil temperature estimating program in FIG. 6 is changed to the condition for changing the target step number Pd in step S22 in FIG. 2 and the step S122 in FIG. Is used only for determining the target step number Pd, but the estimated temperature Te can be used for other purposes. For example, as described in the related art, the present invention can be used for controlling the driving speed of a step motor 51 as an actuator.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a shock absorber and a control device thereof according to an embodiment of the present invention.

FIG. 2 is a flowchart of a damping force control program executed by the microcomputer of FIG. 1;

FIG. 3 is a flowchart showing details of a target step number calculation routine of FIG. 2;

FIG. 4 is a characteristic graph showing a relationship between a sprung-unsprung relative speed and a damping force for each step number (each opening degree) of the variable throttle mechanism.

FIG. 5 is a flowchart showing details of an offload determination routine of FIG. 2;

FIG. 6 is a flowchart of an oil temperature estimating program executed by the microcomputer of FIG. 1;

FIG. 7 is a characteristic graph showing a relationship between a vehicle speed and a heat radiation coefficient.

FIG. 8 is a flowchart showing a modified example of the target step number calculation routine.

FIG. 9 is a characteristic graph showing the relationship between the temperature of hydraulic oil and the damping coefficient of the shock absorber for each number of steps (each opening) of the variable throttle mechanism.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Shock absorber, 11 ... Cylinder, 12 ... Piston, 20 ... Wheel (unsprung member), 30 ... Car body (sprung member), 40 ... Spring, 50 ... Variable throttle mechanism, 5
DESCRIPTION OF SYMBOLS 1 ... Step motor, 61 ... Acceleration sensor, 62 ... Stroke sensor, 63 ... Vehicle speed sensor, 64 ... Outside air temperature sensor, 65 ... Microcomputer, 66 ... Drive circuit.

Claims (9)

[Claims] 1. A cylinder interposed between an unsprung member and a sprung member of a vehicle, filled with hydraulic oil and partitioned by a piston into upper and lower chambers, and an opening of a communication passage between the upper and lower chambers. And a variable throttle mechanism for changing a spring force. A damping force control device for a shock absorber that generates a damping force with respect to a vertical vibration of a sprung member with respect to a unsprung member with a vertical movement of a piston. Target opening degree determining means for determining a target opening degree of the variable throttle mechanism in accordance with a motion state in a direction; temperature estimating means for estimating a temperature of hydraulic oil in the shock absorber; and detecting a state of a traveling road surface of the vehicle. Road surface state detecting means to perform, target opening degree correcting means for correcting the determined target opening degree according to the estimated temperature of the hydraulic oil and the detected state of the traveling road surface, and the corrected target opening degree Opening control means for outputting a corresponding control signal to the variable throttle mechanism to control the opening of the communication passage to the corrected target opening, the damping force for a shock absorber. Control device. 2. The damping force control device for a shock absorber according to claim 1, wherein the target opening degree correcting means is configured to determine that the estimated temperature of the hydraulic oil is equal to or higher than a predetermined temperature and the road surface condition is changed. When the state of the traveling road surface detected by the detecting means is a bad road surface, the target opening determined by the target opening determining means is changed to a larger side, and otherwise, the determined target opening is changed. A damping force control device for a shock absorber that is configured not to change. 3. The damping force control device for a shock absorber according to claim 1, wherein said road surface condition detecting means is controlled based on a magnitude of vibration of at least one of a sprung member and a unsprung member. A damping force control device for a shock absorber configured to detect a state of a traveling road surface of a vehicle. 4. A cylinder interposed between an unsprung member and a sprung member of a vehicle, filled with hydraulic oil and partitioned by a piston into upper and lower chambers, and an opening of a communication passage between the upper and lower chambers. And a variable throttle mechanism for changing a spring force. A damping force control device for a shock absorber that generates a damping force with respect to a vertical vibration of a sprung member with respect to a unsprung member with a vertical movement of a piston. Target damping coefficient determining means for determining a target damping coefficient of the shock absorber according to a motion state in a direction; temperature estimating means for estimating a temperature of hydraulic oil in the shock absorber; and the determined target damping coefficient and A target opening determining means for determining a target opening of the variable throttle mechanism in accordance with the estimated temperature of the hydraulic oil; and a control signal corresponding to the determined target opening to the variable throttle. A damping force control device for a shock absorber, comprising: an opening control means for outputting the opening to the mechanism to control the opening of the communication passage to the determined target opening. 5. The damping force control device for a shock absorber according to claim 4, wherein the target opening degree determining means includes a temperature of the hydraulic oil, an opening degree of the communication passage, and a damping coefficient of the shock absorber. A shock absorber configured to determine a target opening of the variable throttle mechanism so that the damping coefficient of the shock absorber is set to the determined target damping coefficient using data prepared in advance that represents the relationship For damping force control. 6. A cylinder interposed between an unsprung member and a sprung member of a vehicle, filled with hydraulic oil and partitioned by a piston into upper and lower chambers, and an opening of a communication passage between the upper and lower chambers. And a variable throttle mechanism for changing the pressure of the piston. The hydraulic oil of the shock absorber for estimating the temperature of the hydraulic oil in the shock absorber that generates a damping force against the vertical vibration of the unsprung member of the sprung member with the vertical movement of the piston A temperature estimating device, comprising: speed detecting means for detecting a vertical speed of the sprung member with respect to the unsprung member; and a heating value according to an opening set by the variable throttle mechanism and the detected vertical speed. A calorific value calculating means for calculating the temperature of the hydraulic oil based on the calculated calorific value and the detected outside air temperature. A hydraulic oil temperature estimating device for a shock absorber, comprising a degree calculating means. 7. The hydraulic oil temperature estimating device for a shock absorber according to claim 6, wherein the temperature calculating means calculates a current hydraulic oil temperature and the detected outside air temperature calculated by the temperature calculating means. A heat radiation amount calculating means for calculating a heat radiation amount by using the heat radiation amount; and a subtraction means for calculating a temperature of the hydraulic oil by subtracting the calculated heat radiation amount from the calculated heat generation amount. Hydraulic oil temperature estimation device for shock absorber. 8. The apparatus for estimating hydraulic oil temperature of a shock absorber according to claim 7, further comprising: vehicle speed detecting means for detecting a speed of the vehicle; A hydraulic oil temperature estimating device for a shock absorber configured to correct a heat radiation amount calculated using the temperature of the hydraulic oil and the outside air temperature according to 9. The shock absorber operating oil temperature estimating device according to claim 6, wherein the calorific value calculating means is an opening set by the variable throttle mechanism. And the damping force generated by the shock absorber according to the detected vertical speed, and adding the product of the derived damping force and the detected vertical speed to the current heat generation amount, A hydraulic oil temperature estimating device for a shock absorber configured to update the temperature.