JP2009137545A - Damping force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve riding feeling by suppressing not only vertical vibration of an upper spring A but also longitudinal vibration in the case that vibration of a lower spring B is strong. <P>SOLUTION: A specific damping coefficient Ct at which addition of vectors of an upper spring vertical acceleration and a upper spring front-rear acceleration is minimized is calculated and stored beforehand from relation of a damping coefficient of a shock absorber and a vertical acceleration of the upper spring and the damping coefficient of the shock absorber and a front-rear acceleration of the upper spring. In the case that vibration of a lower spring resonant frequency band exceeds a threshold value, the damping coefficient of the shock absorber is set to be the specific damping coefficient Ct. Thus, both the bounce and longitudinal vibration of the upper spring A can be reduced in a well-balanced manner and the riding feeling is improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a damping force control device for a vehicle that controls damping force of a shock absorber provided at each wheel position of the vehicle.

Conventionally, for example, as shown in Patent Document 1, a low-frequency sprung resonance frequency component is cut from a detection signal of a sprung acceleration sensor to extract an unsprung resonance frequency component. A technique is known that grasps the unsprung vibration state and controls the damping coefficient of the shock absorber. In this patent document 1, when the unsprung vibration is not intense (when there is no unsprung flapping), the damping coefficient of the shock absorber is controlled to a high damping coefficient corresponding to the sprung speed. Steering stability is achieved by damping control that suppresses sprung vibration. If the unsprung vibration is intense (if the unsprung part flutters), the damping coefficient of the shock absorber is controlled to a constant low damping coefficient, and the unsprung vibration is absorbed by the shock absorber. To improve the ride comfort.
JP-A-5-104927

  However, in Patent Document 1, when the vibration (vertical acceleration) in the unsprung resonance frequency band is large, the damping coefficient is set to a low damping coefficient. However, when the damping coefficient is lowered, the ride comfort may be worsened. is there. FIG. 3A shows the relationship between the damping coefficient and the vertical acceleration on the spring, and FIG. 3B shows the relationship between the damping coefficient and the longitudinal acceleration on the spring. As can be seen from this figure, when the damping coefficient is lowered, the vertical acceleration on the spring decreases, but the longitudinal acceleration on the spring increases, so the influence of longitudinal vibration increases depending on the damping coefficient setting. Ride comfort deteriorates.

  The present invention has been made to address the above-described problems, and aims to improve riding comfort by suppressing not only vertical vibration on the spring but also longitudinal vibration when the vibration under the spring is intense. To do.

  In order to achieve the above object, the present invention is characterized in that a shock absorber is provided between each of the unsprung and sprung at each wheel position of the vehicle so that the damping coefficient can be changed. In a vehicle damping force control apparatus for controlling a damping coefficient of an absorber, unsprung vibration detecting means for detecting a vibration state in an unsprung resonance frequency band at each wheel position, and the vibration level in the detected unsprung resonance frequency band. Is greater than the reference level, the damping coefficient of the shock absorber is determined as the relationship between the damping coefficient of the shock absorber and the vertical acceleration on the spring, and the damping coefficient of the shock absorber and the longitudinal acceleration on the spring. From this relationship, the specific attenuation coefficient is used as the attenuation coefficient that minimizes the sum of the vectors of the vertical acceleration and the longitudinal acceleration. In that a spring under damping control means for setting, based on the coefficient of.

  In this case, the unsprung vibration detecting means includes a vertical acceleration detecting means for detecting the vertical acceleration under the spring or the unsprung at each wheel position, and vibration in the unsprung resonance frequency band from the detected vertical acceleration signal. There can be provided unsprung vibration component extraction means for extracting the component.

  In the present invention, the unsprung vibration detecting means detects the vibration state in the unsprung resonance frequency band at each wheel position. For example, the vertical acceleration detection means detects the sprung or unsprung vertical acceleration, and the unsprung vibration component extraction means extracts the vibration component in the unsprung resonance frequency band from the detected vertical acceleration signal. When the detected vibration level in the unsprung resonance frequency band exceeds the reference level, the unsprung vibration suppression control means sets the damping coefficient of the shock absorber based on the specific damping coefficient.

  This specific damping coefficient is based on the relationship between the damping coefficient of the shock absorber and the vertical acceleration on the spring, and the relationship between the damping coefficient of the shock absorber and the longitudinal acceleration on the spring. Is set to the attenuation coefficient. The attenuation coefficient that minimizes the sum of the vertical acceleration and longitudinal acceleration vectors can be obtained, for example, by calculating an attenuation coefficient having a minimum square root of a value obtained by adding the square of the vertical acceleration and the square of the longitudinal acceleration. The relationship between the damping coefficient of the shock absorber and the vertical acceleration on the spring, and the relationship between the damping coefficient of the shock absorber and the longitudinal acceleration on the spring can be related by an arithmetic expression or the like.

  The unsprung vibration control means sets the damping coefficient of the shock absorber based on the specific damping coefficient when the vibration level in the unsprung resonance frequency band detected by the unsprung vibration detecting means exceeds the reference level. In this case, it is preferable to set the damping coefficient of the shock absorber to the same value as that of the specific damping coefficient. However, if the damping coefficient of the shock absorber is changed in multiple stages, the damping coefficient is not necessarily the same as the specific damping coefficient. There are cases where it is not possible. In such a case, the damping coefficient of the shock absorber is set to a settable value closest to the specific damping coefficient.

  As a result, according to the present invention, both the vertical vibration and the longitudinal vibration on the spring can be reduced with good balance, and the riding comfort is improved.

  Another feature of the present invention is that, based on the relationship between the damping coefficient of the shock absorber and the vertical acceleration on the spring, and the relationship between the damping coefficient of the shock absorber and the longitudinal acceleration on the spring, the vertical acceleration and the above Specific damping coefficient acquisition means for acquiring the damping coefficient that minimizes the sum of the longitudinal acceleration vectors as the specific damping coefficient, and the unsprung vibration suppression control means has a vibration level in the detected unsprung resonance frequency band as a reference level. The damping coefficient of the shock absorber is set based on the specific damping coefficient acquired by the specific damping coefficient acquisition means.

  In the present invention, the specific attenuation coefficient is acquired by the specific attenuation coefficient acquisition means. For example, the specific attenuation coefficient acquisition unit can store the specific attenuation coefficient in the storage unit in advance, and read and acquire the specific attenuation coefficient from the storage unit. Alternatively, an arithmetic expression or a map representing the relationship between the damping coefficient of the shock absorber and the vertical acceleration on the spring and the relationship between the damping coefficient of the shock absorber and the longitudinal acceleration on the spring is stored in advance as storage data in the storage means. The specific attenuation coefficient can be acquired based on the association data stored in the storage means. Further, for example, when the specific attenuation coefficient is changed according to the traveling state of the vehicle, a map or an arithmetic expression relating the traveling state and the specific attenuation coefficient is stored in the storage unit in advance as association data. The specific attenuation coefficient can be acquired based on the association data stored in the storage means.

  The unsprung vibration suppression control unit is configured to perform a shock based on the specific damping coefficient acquired by the specific damping coefficient acquisition unit when the vibration level in the unsprung resonance frequency band detected by the unsprung vibration detection unit exceeds a reference level. Set the damping coefficient of the absorber. Therefore, both the vertical vibration and the longitudinal vibration on the spring can be reduced with good balance, and the riding comfort is improved.

  Another feature of the present invention is that relative position detecting means for detecting the relative position of the unsprung direction relative to the sprung at each wheel position, and the specific damping coefficient is changed according to the detected relative position. And a specific damping coefficient changing means corresponding to the vehicle height.

  The relationship between the damping coefficient of the shock absorber and the longitudinal acceleration on the spring is, for example, the forward tilt angle of the shock absorber (angle with respect to the vertical line of the shock absorber axis) or the longitudinal elastic main axis opposite angle of the suspension (with respect to the horizontal line of the longitudinal elastic main axis). It depends on the angle. These angles change according to the vehicle height, that is, the relative position of the unsprung and unsprung directions relative to the sprung. Therefore, in the present invention, the relative position detecting means detects the relative position of the unsprung direction relative to the sprung, and the vehicle height corresponding specific damping coefficient changing means changes the specific damping coefficient in accordance with the detected relative position. .

  For example, the vehicle height corresponding specific damping coefficient changing means stores in the storage means association data such as a map or an arithmetic expression for deriving a specific damping coefficient corresponding to the relative position of the unsprung direction relative to the sprung in the vertical direction. It is possible to employ a configuration in which a specific damping coefficient is set according to the relative position of the unsprung and unsprung directions with respect to the sprung using the association data stored in the storage means during traveling. In addition, the relative position in the vertical direction of the unsprung state with respect to the sprung has the same meaning as the relative position in the vertical direction on the spring with respect to the unsprung state. In short, it means the relative position in the vertical direction between the sprung and unsprung. Is.

  As a result, according to the present invention, the specific damping coefficient becomes more appropriate, and both the vertical vibration and the longitudinal vibration on the spring can be reduced with a better balance, and riding comfort is improved.

  Another feature of the present invention is that vehicle speed detecting means for detecting a vehicle speed and vehicle speed-specific specific attenuation coefficient changing means for changing the specific attenuation coefficient in accordance with the detected vehicle speed are provided.

  The relationship between the damping coefficient of the shock absorber and the longitudinal acceleration on the spring varies depending on the vehicle speed. Therefore, in the present invention, the vehicle speed detecting means detects the vehicle speed, and the specific attenuation coefficient changing means corresponding to the vehicle speed changes the specific attenuation coefficient according to the detected vehicle speed.

  For example, the specific attenuation coefficient changing means corresponding to the vehicle speed stores association data such as a map or an arithmetic expression for deriving the specific attenuation coefficient corresponding to the vehicle speed in the storage means, and the association stored in the storage means during the vehicle traveling. A configuration in which a specific attenuation coefficient corresponding to the vehicle speed is set using data can be employed.

  As a result, according to the present invention, the specific damping coefficient becomes more appropriate, and both the vertical vibration and the longitudinal vibration on the spring can be reduced with a better balance, and riding comfort is improved.

  A specific damping coefficient corresponding to the combination of both the unsprung relative position of the unsprung and the vehicle speed and the vehicle speed is stored in the storage means as association data such as a map or an arithmetic expression so that the vehicle is traveling. A configuration in which a specific attenuation coefficient corresponding to the relative position and the vehicle speed is set using the association data stored in the storage unit may be employed.

  Hereinafter, a vehicle damping force control apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a vehicle damping force control apparatus as a first embodiment. This damping force control device includes a shock absorber 10 and a coil spring 20 between the vehicle body BD and the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr, respectively. Hereinafter, the left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr are simply referred to as wheels W when the front, rear, left and right are not specified.

  The shock absorber 10 is interposed between a suspension member 14 such as a lower arm or a knuckle that holds each wheel W so as to be swingable in the vertical direction with respect to the vehicle body BD, and the vehicle body BD. The shock absorber 10 includes a cylinder 11 and a piston rod 12 inserted in the cylinder 11 so as to be movable up and down. The lower end of the cylinder 11 is connected to a suspension member 14 (for example, a lower arm), and the piston rod 12 Is fixed to the vehicle body BD. The coil spring 20 is provided in parallel with the shock absorber 10. The cylinder 11 is partitioned into upper and lower chambers R1 and R2 by a piston 13 that slides liquid-tightly on the inner peripheral surface thereof.

  A variable throttle mechanism 30 is assembled to the piston 13. The variable throttle mechanism 30 switches the degree of opening of the communication path for communicating between the upper and lower chambers R1 and R2 of the cylinder 11 in a plurality of stages by the operation of an actuator 31 constituting a part thereof. According to this switching step, when the opening degree of the communication path increases, the damping force of the shock absorber 10 is set to the soft side, and when the opening degree of the communication path decreases, the damping force of the shock absorber 10 is set to the hard side. It is like that. As the actuator 31, for example, an electric motor is used, and the opening degree of the communication path is changed by changing the rotation angle (rotation position) of the electric motor stepwise. The variable throttle mechanism 30 may be of a type that continuously adjusts the opening degree of the communication path that allows the upper and lower chambers R1, R2 of the cylinder 11 to communicate with each other.

  The entire member provided on the upper portion with the coil spring 20 as a boundary and supported by the coil spring 20 is referred to as a sprung A. In this example, the vehicle body BD corresponds to the sprung A. The entire member provided at the lower part with the coil spring 20 as a boundary is referred to as an unsprung B. In this example, the suspension member 14, the wheels Wfl to Wrr, the brake (not shown), and the like correspond to the unsprung B.

  The damping force control device includes a damping force control unit 40 that controls the operation of the actuator 31 to control the damping force of the shock absorber 10. The damping force control unit 40 (hereinafter referred to as damping force ECU 40) includes a microcomputer including a CPU, a ROM, a RAM, and the like as a main part. Sensors 41fl, 41fr, 41rl, 41rr are connected.

  The sprung vertical acceleration sensors 41fl, 41fr, 41rl, and 41rr are respectively mounted on the sprung A corresponding to the left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr, and the vertical direction of the sprung A with respect to the absolute space at the mounting position. The sprung accelerations Gzfl, Gzfr, Gzrl and Gzrr are detected. The sprung vertical accelerations Gzfl to Gzrr detected by the sprung vertical acceleration sensors 41fl to 41rr indicate that acceleration is generated upward with respect to the vehicle when positive, and downward with respect to the vehicle when negative. This means that the acceleration of.

  The damping force ECU 40 calculates damping coefficients corresponding to the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr, and switches the opening of the communication passage of each cylinder 11 according to the damping coefficient, thereby damping the shock absorbers 10. Control power independently. Since the damping force control of each shock absorber 10 is performed in the same manner for each wheel Wfl, Wfr, Wrl, Wrr, the following description is not given separately for each wheel Wfl, Wfr, Wrl, Wrr. . Hereinafter, the sprung vertical acceleration sensors 41fl, 41fr, 41rl and 41rr are simply referred to as a sprung vertical acceleration sensor 41, and the detected sprung vertical accelerations Gzfl, Gzfr, Gzrl and Gzrr are simply referred to as a sprung vertical acceleration Gz. Call.

Next, the relationship between the damping coefficient C of the shock absorber 10 and the vertical acceleration and longitudinal acceleration of the sprung A will be described.
The unsprung B vibrates violently in the unsprung resonance frequency band (for example, 8 Hz to 16 Hz) due to rough road traveling or the like. Such vibration of the unsprung resonance frequency of the unsprung B is generally called fluttering. Therefore, the flutter of unsprung B can be detected by extracting the unsprung resonance frequency band component from the vertical acceleration signal detected by the sprung vertical acceleration sensor 41. When fluttering of this unsprung B occurs, transmission of unsprung vibration to the sprung A can be suppressed by changing the damping coefficient of the shock absorber 10.

式中において、ｍ₁は、ばね下質量を表し、ｍ₂は、ばね上Ａの１輪分の質量を表す。また、図２に示すように、Ｋ_cはホイルレイト、Ｋ_uはアッパーサポート剛性を表す。また、Ｋ_tzはタイヤの上下剛性を表す。ｓはラプラス演算子である。 The vertical acceleration of the sprung A in the unsprung resonance frequency band (hereinafter referred to as the sprung vertical acceleration Gz) can be expressed by the following equation (1) using the damping coefficient C of the shock absorber 10.

In the formula, m ₁ represents the unsprung mass, and m ₂ represents the mass of one wheel of the sprung A. Further, as shown in FIG. 2, K _c is the wheel rate, the K _u represents the upper support rigidity. K _tz represents the vertical rigidity of the tire. s is a Laplace operator.

式（２）中において、ｆ（ｓ）、ｈ（ｓ）は、以下の通りである。

The unsprung vibration also generates vibrations in the front-rear direction of the sprung A. This longitudinal vibration of the sprung A can also be suppressed by changing the damping coefficient of the shock absorber 10. The longitudinal acceleration of the sprung A in the unsprung resonance frequency band (hereinafter referred to as the sprung longitudinal acceleration Gx) can be expressed by the following equation (2) using the damping coefficient C of the shock absorber 10.

In the formula (2), f (s) and h (s) are as follows.

As shown in FIG. 2, the parameters in the equation are: K _x is the longitudinal elastic principal axis rigidity (the entire member such as the link mechanism that connects the wheel W to the vehicle body BD is regarded as one longitudinal elastic principal axis, and Direction stiffness), K _θ is the stiffness when the axle carrier rotates around the spindle axis, α is the forward tilt angle of the shock absorber 10 (angle formed with the vertical line of the axis of the shock absorber 10), and β is the longitudinal elastic main shaft. Diagonal angle (upward angle relative to the horizontal line of the front and rear elastic main shaft), H is the vertical distance between the center of gravity of the axle carrier and the front and rear elastic main shaft, L is the distance in the horizontal direction between the center of gravity of the axle carrier and the axis of the shock absorber 10 Represents. Also, K _tx is the front-rear direction stiffness tire, the P _x driving stiffness, W is the vertical load of one wheel component, I _t is the moment of inertia of the tire and wheel, V is vehicle speed, r ₀ is the radius of the constant partial tire dynamic load . Also, ε is a value obtained by dividing the tire dynamic load radius variation by the tire static load radius (tire deflection) variation. That is, it is a value represented by (tire dynamic load radius variation / tire static load radius variation). The other parameters are the same as those described in Expression (1).

  FIGS. 3 and 4 show examples of two suspension devices in which the sprung vertical acceleration Gz and the sprung longitudinal acceleration Gx are calculated based on the equations (1) and (2). In both figures, (a) represents the relationship between the damping coefficient C of the shock absorber 10 and the magnitude (absolute value) of the sprung vertical acceleration Gz in the unsprung resonance frequency band, and (b) represents the damping of the shock absorber 10. This represents the relationship between the coefficient C and the magnitude (absolute value) of the sprung longitudinal acceleration Gx in the unsprung resonance frequency band. The reason why the two examples have different characteristics is that the configuration of the suspension device is different.

  As can be seen from this example, the sprung vertical acceleration Gz decreases by decreasing the damping coefficient C, but the sprung longitudinal acceleration Gx has a region that increases by decreasing the damping coefficient C. For example, in the example shown in FIG. 4, when the damping coefficient C is lower than around 1600 N · s / m, the sprung longitudinal acceleration Gx increases as the damping coefficient C decreases. In the example shown in FIG. 3, the sprung longitudinal acceleration Gx increases in the entire region of the damping coefficient C as the damping coefficient C decreases.

  When the unsprung B flutters due to traveling on a rough road or the like, by reducing the damping coefficient C, the vibration of the unsprung B can be absorbed and the transmission to the sprung A can be suppressed. As can be seen from FIG. 4, if the damping coefficient C is lowered too much, the effect of the sprung longitudinal acceleration Gx appears greatly, and the riding comfort deteriorates.

  Therefore, in the present embodiment, the damping coefficient Ct (hereinafter, this damping coefficient Ct is a specific damping coefficient) that minimizes the sum of the vectors so as to balance the sprung vertical acceleration Gz and the sprung longitudinal acceleration Gx. Ct) is calculated in advance, and when the vibration state in the resonance frequency band of the unsprung B is intense, the damping force of the shock absorber 10 is controlled using this specific damping coefficient Ct. The sprung longitudinal acceleration Gx changes according to the vehicle height and the vehicle speed as described in the second and third embodiments to be described later. In the first embodiment, the vehicle height and the vehicle speed are set to standard values. The specific attenuation coefficient Ct is calculated in advance with the value fixed.

この平方根の値が最小となる特定減衰係数Ｃｔは、予め計算され減衰力ＥＣＵ４０のＲＯＭ内に制御プログラムとともに記憶される。尚、特定減衰係数Ｃｔが得られる可変絞り機構３０の連通路の開度を記憶するようにしてもよい。 The sum Gt of the vectors of the sprung vertical acceleration Gz and the sprung longitudinal acceleration Gx is the square of the sprung vertical acceleration Gz calculated by the above equation (1) and the sprung longitudinal acceleration Gx calculated by the above equation (2). It can be expressed as the following equation (3) as the square root of the sum of squares.

The specific damping coefficient Ct that minimizes the square root value is calculated in advance and stored in the ROM of the damping force ECU 40 together with the control program. Note that the opening degree of the communication path of the variable throttle mechanism 30 that obtains the specific damping coefficient Ct may be stored.

  Next, the unsprung vibration suppression control process performed by the damping force ECU 40 will be described. FIG. 5 is a flowchart showing an unsprung vibration suppression control routine. This unsprung vibration damping control routine is stored as a control program in the ROM of the damping force ECU 40, is activated by turning on an ignition switch (not shown), and is repeated for each wheel W independently at a predetermined short cycle. It is.

  The damping force ECU 40 performs not only the unsprung vibration suppression control but also various damping force control processes in parallel, but the other damping force control processes do not form the features of the present invention and are general. Therefore, in this embodiment, the configuration for performing other damping force control is omitted from the configuration of the damping force control device. Other damping force controls include, for example, vehicle speed sensitive control, anti-dive control, anti-squat control, roll attitude control, tilt control, and rough sensitive control.

  When the unsprung vibration suppression control routine is activated, the damping force ECU 40 reads the sprung vertical acceleration signal Gz detected by the sprung vertical acceleration sensor 41 in step S11. Subsequently, in step S12, the damping force ECU 40 extracts a frequency component in the unsprung resonance frequency band (for example, 8 Hz to 16 Hz) from the sprung vertical acceleration signal Gz by bandpass filter processing. Therefore, the signal obtained by this bandpass filter process is an acceleration signal corresponding to the unsprung B vibration state. Thereby, the flapping state of the unsprung B can be detected.

  Subsequently, in step S13, the damping force ECU 40 determines whether or not the magnitude Gzf (the absolute value of acceleration) of the frequency component extracted by the bandpass filter process exceeds the reference value Gz0 (threshold value). . That is, it is determined whether or not the vibration level of the unsprung B exceeds the reference level.

  When the damping force ECU 40 determines in step S13 that the magnitude of vibration Gzf in the unsprung resonance frequency band exceeds the reference value Gz0, in step S14, the damping coefficient C is changed to the above-described specific damping coefficient Ct. Set. The specific damping coefficient Ct is stored in a storage element such as a ROM of the damping force ECU 40, and is acquired by reading from the storage element in step S14. The configuration in which the specific attenuation coefficient Ct is read out and acquired from the storage element corresponds to the specific attenuation coefficient acquisition means of the present invention.

  The damping force ECU 40 changes the damping coefficient of the shock absorber 10 by switching the communication opening degree of the cylinder 11. In this case, the communication opening degree corresponding to the specific damping coefficient Ct is selected. That is, the damping force ECU 40 stores the correspondence relationship between the damping coefficient and the communication opening degree in a storage element such as a ROM, and sets the communication opening degree corresponding to the specific damping coefficient Ct from this correspondence relationship. In the shock absorber 10 of the present embodiment, the communication opening degree is switched to a plurality of stages by the variable throttle mechanism 30. Therefore, when the communication opening degree at which the specific damping coefficient Ct is obtained cannot be set, the specific damping is performed. A communication opening degree that provides a damping coefficient closest to the coefficient Ct is selected.

  In the first embodiment, the specific damping coefficient Ct is a fixed value calculated in advance, and therefore, as one of the communication openings that can select a plurality of dedicated communication openings for obtaining the specific attenuation coefficient Ct. It may be prepared in the variable throttle mechanism 30 and switched to this dedicated communication opening degree. In addition, when the shock absorber 10 of a type that can continuously change the communication opening is employed, the communication opening is set to a specific damping coefficient Ct.

  Thus, by setting the damping coefficient of the shock absorber 10 based on the specific damping coefficient Ct, the vertical vibration and the front-back vibration of the sprung A are reduced with a good balance. Therefore, riding comfort is improved.

  The damping force ECU 40 once ends the unsprung vibration suppression control routine when the damping coefficient of the shock absorber 10 is set by the process of step S14. The unsprung vibration suppression control routine is repeated at a predetermined short cycle.

  If it is determined in step S13 that the magnitude of vibration Gzf in the unsprung resonance frequency band does not exceed the reference value Gz0, there is no need to perform unsprung vibration control, so the unsprung vibration control routine is temporarily performed as it is. finish. In this case, the damping coefficient of the shock absorber 10 is controlled to a damping coefficient set by other damping force control, for example, vehicle speed sensitive control.

  According to the damping force control apparatus of the first embodiment described above, when the vibration level of the unsprung B exceeds the reference level, the sum of the vectors of the vertical acceleration and the longitudinal acceleration of the sprung A is minimized. Since the damping force of the shock absorber 10 is controlled based on the specific damping coefficient Ct, the vertical vibration and the front-rear vibration of the sprung A are reduced in a well-balanced manner. As a result, riding comfort is improved.

Second Embodiment
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in that the specific attenuation coefficient Ct is changed according to the vehicle height, and the other configuration is the same as that of the first embodiment. As shown in FIG. 6, the damping force control apparatus of the second embodiment includes vehicle height sensors 42 fl, 42 fr, 42 rl, 42 rr that detect the relative positions of the unsprung B with respect to the sprung A in the vertical direction. , Wrl, Wrr, and a configuration for outputting vehicle height signals Xfl, Xfr, Xrl, Xrr detected by vehicle height sensors 42fl, 42fr, 42rl, 42rr to the damping force ECU 40 according to the first embodiment. It is added to the device.

  The vehicle height sensors 42fl, 42fr, 42rl, 42rr are provided between the unsprung B and the sprung A corresponding to the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr, respectively. Vehicle heights Xfl, Xfr, Xrl, and Xrr corresponding to displacements with respect to the reference vehicle height are detected from the vertical relative positions of the left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr, that is, the distance between them. A positive value is taken when the detected vehicle height is higher than the reference vehicle height, and a negative value is taken when the detected vehicle height is lower than the reference vehicle height. Since the damping force control of each shock absorber 10 is performed in the same manner for each wheel Wfl, Wfr, Wrl, Wrr, the following description will be made separately for each wheel Wfl, Wfr, Wrl, Wrr. Do not do. Hereinafter, the vehicle height sensors 42fl, 42fr, 42rl, and 42rr are simply referred to as the vehicle height sensor 42, and the detected vehicle heights Xfl, Xfr, Xrl, and Xrr are simply referred to as the vehicle height X.

  As shown in the above-described equation (2), the sprung longitudinal acceleration Gx changes according to the forward tilt angle α and the longitudinal elastic main axis opposite angle β of the shock absorber 10. Further, the forward tilt angle α and the longitudinal elastic principal axis opposite angle β of the shock absorber 10 vary depending on the vehicle height X, that is, the relative position in the vertical direction of the unsprung B with respect to the sprung A, and are uniquely determined from the relative positions. . For example, in the simple model shown in FIG. 2, the greater the vehicle height X, the smaller the forward inclination angle α of the shock absorber 10 and the larger the longitudinal elastic main axis opposite angle β. Therefore, by substituting (α, β) corresponding to the vehicle height X into the equation (2), the longitudinal acceleration Gx of the sprung A in the unsprung resonance frequency band can be expressed using the damping coefficient C.

  Therefore, finally, the specific damping coefficient Ct that minimizes the sum of the vectors of the sprung vertical acceleration Gz and the sprung longitudinal Gx can be calculated in advance according to the vehicle height X. Accordingly, in the damping control device of the second embodiment, a map (association data) that defines the relationship between the vehicle height X and the specific damping coefficient Ct as shown in FIG. 7 is stored in the ROM of the damping force ECU 40. The specific attenuation coefficient Ct can be acquired from the vehicle height X detected while the vehicle is running. This map was created by calculating in advance a specific damping coefficient Ct corresponding to a change in the vehicle height X based on the equations (1), (2), and (3) with the vehicle speed fixed at a standard value. It is stored in the ROM of the damping force ECU 40. In this example, when the vehicle height X is lower than the reference vehicle height, the specific damping coefficient Ct is set to a larger value than when the vehicle height X is higher than the reference vehicle height. The association data may be stored not only in the ROM but also in other storage means.

  Next, the unsprung vibration suppression control process performed by the damping force ECU 40 will be described. FIG. 8 is a flowchart showing an unsprung vibration suppression control routine as the second embodiment. This unsprung vibration damping control routine is stored as a control program in the ROM of the damping force ECU 40, is activated by turning on an ignition switch (not shown), and is repeated for each wheel W independently at a predetermined short cycle. It is.

  When the unsprung vibration suppression control routine is activated, the damping force ECU 40 reads the sprung vertical acceleration signal Gz detected by the sprung vertical acceleration sensor 41 in step S21. Subsequently, in step S22, the damping force ECU 40 extracts the frequency component of the unsprung resonance frequency band (for example, 8 Hz to 16 Hz) from the unsprung vertical acceleration signal Gz by the bandpass filter process. Detects flapping status.

  Subsequently, in step S23, the damping force ECU 40 determines whether or not the magnitude Gzf (absolute value of acceleration) of the frequency component extracted by the bandpass filter process exceeds the reference value Gz0 (threshold value). . That is, it is determined whether or not the vibration level of the unsprung B exceeds the reference level.

  If the damping force ECU 40 determines in step S23 that the magnitude Gzf of vibration in the unsprung resonance frequency band exceeds the reference value Gz0, the vehicle height X detected by the vehicle height sensor 42 in step S24. Is read. Subsequently, in step S25, the damping force ECU 40 refers to a map that defines the relationship between the vehicle height X and the specific damping coefficient Ct shown in FIG. 7, and obtains the specific damping coefficient Ct corresponding to the detected vehicle height X. . A configuration in which the specific attenuation coefficient Ct is changed according to the vehicle height X corresponds to the vehicle height-specific specific attenuation coefficient changing means of the present invention. Moreover, the structure which calculates | requires this specific attenuation coefficient Ct from a map corresponds to the specific attenuation coefficient acquisition means of this invention.

  The specific attenuation coefficient Ct may be calculated sequentially using equations (1), (2), and (3). For example, the association data for associating the vehicle height X with (α, β) is stored in advance in the storage means using a map or the like. Then, (α, β) corresponding to the vehicle height X detected in step S24 is obtained from the association data, and the obtained (α, β) is substituted into equation (2). Finally, the sum of the vectors of the vertical acceleration Gz and the longitudinal acceleration Gx of the sprung A is minimized by using the formula (2) into which (α, β) is substituted and the formulas (1) and (3). A specific attenuation coefficient Ct is calculated.

  When the specific damping coefficient Ct is obtained in step S25, the damping force ECU 40 subsequently sets the damping coefficient of the shock absorber 10 to the specific damping coefficient Ct in step S26 and once ends the unsprung vibration suppression control routine. . In this case, since the shock absorber 10 is of a type that changes the damping coefficient by switching the communication opening of the cylinder 11 in a plurality of stages, if the communication opening that provides the specific damping coefficient Ct cannot be set, the specific damping A communication opening degree that provides a damping coefficient closest to the coefficient Ct is selected. In addition, when the shock absorber 10 of the type which can change a communication opening continuously is employ | adopted, it sets to the communication opening which can obtain specific damping coefficient Ct.

  As a result, the damping coefficient of the shock absorber 10 is set to the optimum specific damping coefficient Ct corresponding to the vehicle height X, so that the vertical vibrations and the longitudinal vibrations of the sprung A can be further reduced in a balanced manner. it can.

  On the other hand, if it is determined in step S23 that the magnitude Gzf of vibration in the unsprung resonance frequency band does not exceed the reference value Gz0, there is no need to perform unsprung vibration control. It ends as it is. In this case, the damping coefficient of the shock absorber 10 is controlled to a damping coefficient set by other damping force control, for example, vehicle speed sensitive control.

  According to the damping force control apparatus of the second embodiment described above, the specific damping coefficient Ct is acquired according to the vehicle height X of the traveling vehicle, and therefore the specific damping coefficient Ct becomes a more appropriate value. Therefore, the vertical vibration and the front-back vibration of the sprung A can be further reduced in a balanced manner. As a result, riding comfort is further improved.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. The third embodiment is different from the first embodiment in that the specific damping coefficient Ct is changed according to the vehicle speed, and the other configuration is the same as that of the first embodiment. As shown in FIG. 9, the damping force control device of the third embodiment employs a configuration in which a vehicle speed sensor 43 that detects the traveling speed of the vehicle is added to the damping force control device of the first embodiment. The vehicle speed sensor 43 is connected to the damping force ECU 40 and outputs a signal representing the vehicle speed V to the damping force ECU 40.

  As shown in Equation (2), the sprung longitudinal acceleration Gx changes according to the vehicle speed V. Accordingly, the specific damping coefficient Ct that minimizes the sum of the vectors of the sprung vertical acceleration Gz and the sprung longitudinal Gx can be calculated in advance according to the vehicle speed V. Therefore, in the damping control device of the third embodiment, a map (association data) that defines the relationship between the vehicle speed V and the specific damping coefficient Ct as shown in FIG. 10 is stored in the ROM of the damping force ECU 40, and The specific attenuation coefficient Ct can be acquired from the vehicle speed V detected while the vehicle is running. This map was created by fixing the vehicle height to a standard value and calculating in advance the specific damping coefficient Ct corresponding to the change in the vehicle speed V based on the equations (1), (2), and (3). It is stored in the ROM of the damping force ECU 40. In this example, the specific damping coefficient Ct is set to a small value as the vehicle speed V increases. The association data may be stored not only in the ROM but also in other storage means.

  Next, the unsprung vibration suppression control process performed by the damping force ECU 40 will be described. FIG. 11 is a flowchart showing an unsprung vibration suppression control routine as the third embodiment. This unsprung vibration damping control routine is stored as a control program in the ROM of the damping force ECU 40, is activated by turning on an ignition switch (not shown), and is repeated for each wheel W independently at a predetermined short cycle. It is.

  When the unsprung vibration suppression control routine is activated, the damping force ECU 40 reads the sprung vertical acceleration signal Gz detected by the sprung vertical acceleration sensor 41 in step S31. Subsequently, in step S32, the damping force ECU 40 extracts the frequency component of the unsprung resonance frequency band (for example, 8 Hz to 16 Hz) from the unsprung vertical acceleration signal Gz by bandpass filter processing, thereby Detects flapping status.

  Subsequently, in step S33, the damping force ECU 40 determines whether or not the magnitude Gzf (absolute acceleration value) of the frequency component extracted by the bandpass filter process exceeds the reference value Gz0 (threshold value). . That is, it is determined whether or not the vibration level of the unsprung B exceeds the reference level.

  If the damping force ECU 40 determines in step S33 that the magnitude of vibration Gzf in the unsprung resonance frequency band exceeds the reference value Gz0, the vehicle speed V detected by the vehicle height sensor 43 is determined in step S34. Read. Subsequently, in step S35, the damping force ECU 40 refers to a map that defines the relationship between the vehicle speed V and the specific damping coefficient Ct shown in FIG. 10, and obtains the specific damping coefficient Ct corresponding to the detected vehicle speed V. The configuration in which the specific damping coefficient Ct is changed according to the vehicle speed V corresponds to the vehicle speed-specific specific damping coefficient changing means of the present invention. Moreover, the structure which calculates | requires this specific attenuation coefficient Ct from a map corresponds to the specific attenuation coefficient acquisition means of this invention. Instead of the map, equations (1), (2), and (3) may be stored in the storage means, and the specific attenuation coefficient Ct may be calculated sequentially during traveling using these equations. .

  When the specific damping coefficient Ct is obtained in step S35, the damping force ECU 40 subsequently sets the damping coefficient of the shock absorber 10 to the specific damping coefficient Ct in step S36 and temporarily ends the unsprung vibration suppression control routine. . In this case, since the shock absorber 10 is of a type that changes the damping coefficient by switching the communication opening of the cylinder 11 in a plurality of stages, if the communication opening that provides the specific damping coefficient Ct cannot be set, the specific damping A communication opening degree that provides a damping coefficient closest to the coefficient Ct is selected. In addition, when the shock absorber 10 of the type which can change a communication opening continuously is employ | adopted, it sets to the communication opening which can obtain specific damping coefficient Ct.

  Thereby, since the damping coefficient of the shock absorber 10 is set to the optimum specific damping coefficient Ct corresponding to the vehicle speed V, the vertical vibration and the front-back vibration of the sprung A can be further reduced in a balanced manner. .

  On the other hand, if it is determined in step S33 that the magnitude Gzf of vibration in the unsprung resonance frequency band does not exceed the reference value Gz0, there is no need to perform unsprung vibration control. It ends as it is. In this case, the damping coefficient of the shock absorber 10 is controlled to a damping coefficient set by other damping force control, for example, vehicle speed sensitive control.

  According to the damping force control apparatus of the third embodiment described above, the specific damping coefficient Ct is obtained according to the vehicle speed V of the traveling vehicle, and therefore the specific damping coefficient Ct becomes a more appropriate value. Therefore, the vertical vibration and the front-back vibration of the sprung A can be further reduced in a balanced manner. As a result, riding comfort is further improved.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described. The damping force control device according to the fourth embodiment is a combination of the second embodiment and the third embodiment. As shown in FIG. 12, each wheel Wfl, Wfr, Wrl, Wrr is applied to the sprung A. Configuration in which vehicle height sensors 42fl, 42fr, 42rl, 42rr (hereinafter simply referred to as vehicle height sensor 42) for detecting the relative position in the vertical direction of unsprung B and vehicle speed sensor 43 are added to the first embodiment. Is adopted. The vehicle height sensor 42 and the vehicle speed sensor 43 are the same as those described in the second embodiment and the third embodiment.

  As described in the second and third embodiments, the sprung longitudinal acceleration Gx represented by the expression (2) changes according to the vehicle height X and the vehicle speed V. Therefore, the specific damping coefficient Ct that minimizes the sum of the vectors of the sprung vertical acceleration Gz and the sprung longitudinal Gx can be calculated in advance according to the vehicle height X and the vehicle speed V. Therefore, in the damping control device of the fourth embodiment, a map (association data) that defines the relationship between the vehicle height X and the specific damping coefficient Ct for each vehicle speed V as shown in FIG. The specific attenuation coefficient Ct can be acquired from the vehicle height X and the vehicle speed V detected during the traveling of the vehicle. This map is created by calculating in advance a specific damping coefficient Ct corresponding to changes in the vehicle height X and the vehicle speed V based on the equations (1), (2), and (3). Is stored within. The association data may be stored not only in the ROM but also in other storage means.

  Next, the unsprung vibration suppression control process performed by the damping force ECU 40 will be described. FIG. 14 is a flowchart showing an unsprung vibration suppression control routine as the fourth embodiment. This unsprung vibration damping control routine is stored as a control program in the ROM of the damping force ECU 40, is activated by turning on an ignition switch (not shown), and is repeated for each wheel W independently at a predetermined short cycle. It is.

  When the unsprung vibration suppression control routine is activated, the damping force ECU 40 reads the sprung vertical acceleration signal Gz detected by the sprung vertical acceleration sensor 41 in step S41. Subsequently, in step S42, the damping force ECU 40 extracts the frequency component of the unsprung resonance frequency band (for example, 8 Hz to 16 Hz) from the sprung vertical acceleration signal Gz by bandpass filter processing, thereby Detects flapping status.

  Subsequently, in step S43, the damping force ECU 40 determines whether or not the magnitude Gzf (the absolute value of acceleration) of the frequency component extracted by the bandpass filter process exceeds the reference value Gz0 (threshold value). . That is, it is determined whether or not the vibration level of the unsprung B exceeds the reference level.

  If the damping force ECU 40 determines in step S43 that the vibration magnitude Gzf of the unsprung resonance frequency band exceeds the reference value Gz0, the vehicle height X detected by the vehicle height sensor 42 in step S44. Is read. Subsequently, in step S45, the vehicle speed V detected by the vehicle speed sensor 43 is read.

  Next, in step S46, the damping force ECU 40 refers to a map that defines the relationship between the vehicle height X and the specific damping coefficient Ct for each vehicle speed V as shown in FIG. 13, and detects the detected vehicle height X and vehicle speed V. A specific attenuation coefficient Ct corresponding to is obtained. Note that instead of the map, similar to the above-described embodiment, the calculation may be performed sequentially using equations (1), (2), and (3).

  When the specific damping coefficient Ct is obtained in step S46, the damping force ECU 40 subsequently sets the damping coefficient of the shock absorber 10 to the specific damping coefficient Ct in step S47 and temporarily ends the unsprung vibration damping control routine. . In this case, since the shock absorber 10 is of a type that changes the damping coefficient by switching the communication opening of the cylinder 11 in a plurality of stages, if the communication opening that provides the specific damping coefficient Ct cannot be set, the specific damping A communication opening degree that provides a damping coefficient closest to the coefficient Ct is selected. In addition, when the shock absorber 10 of the type which can change a communication opening continuously is employ | adopted, it sets to the communication opening which can obtain specific damping coefficient Ct.

  As a result, the damping coefficient of the shock absorber 10 is set to the optimum specific damping coefficient Ct according to the vehicle height X and the vehicle speed V, so that the vertical vibrations and the vibrations in the front-rear direction of the sprung A are further reduced in a balanced manner. can do.

  On the other hand, if it is determined in step S43 that the magnitude Gzf of vibration in the unsprung resonance frequency band does not exceed the reference value Gz0, there is no need to perform unsprung vibration control. It ends as it is. In this case, the damping coefficient of the shock absorber 10 is controlled to a damping coefficient set by other damping force control, for example, vehicle speed sensitive control.

  According to the damping force control apparatus of the fourth embodiment described above, the specific damping coefficient Ct is acquired in accordance with the vehicle height X and the vehicle speed V of the traveling vehicle, so that the specific damping coefficient Ct becomes a more appropriate value. . Therefore, the vertical vibration and the front-back vibration of the sprung A can be further reduced in a balanced manner. As a result, riding comfort is further improved.

  Although the vehicle damping force control device as an embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention. .

  For example, in this embodiment, the flapping state of the unsprung B is detected by extracting the frequency component of the unsprung resonance frequency band from the sprung vertical acceleration signal Gz detected by the sprung vertical acceleration sensor 41. In place of the upper vertical acceleration sensor 41, an unsprung vertical acceleration sensor (not shown) for detecting the vertical acceleration of the unsprung B is provided, and the frequency in the unsprung resonance frequency band is determined from the unsprung acceleration signal detected by the unsprung vertical acceleration sensor. The fluttering state of the unsprung B may be detected by extracting the component.

  Moreover, you may make it detect the vibration state of the unsprung B using other sensors, such as a piezo sensor. In the present embodiment, the unsprung resonance frequency band is set to 8 Hz to 16 Hz and the bandpass filter processing is performed. However, the unsprung resonance frequency band can be appropriately changed according to the suspension characteristics and the like.

It is a schematic block diagram of the damping-force control apparatus concerning 1st Embodiment. It is the simple model figure shown in order to demonstrate the specification of a suspension apparatus. It is a characteristic view showing the relationship between the damping coefficient, the sprung vertical acceleration, and the sprung longitudinal acceleration. It is a characteristic view showing the relationship between the damping coefficient, the sprung vertical acceleration, and the sprung longitudinal acceleration. It is a flowchart showing the unsprung vibration suppression control routine concerning 1st Embodiment. It is a schematic block diagram of the damping-force control apparatus concerning 2nd Embodiment. The reference map for acquiring the specific attenuation coefficient concerning 2nd Embodiment is represented. It is a flowchart showing the unsprung vibration suppression control routine concerning 2nd Embodiment. It is a schematic block diagram of the damping-force control apparatus concerning 3rd Embodiment. The reference map for acquiring the specific attenuation coefficient concerning 3rd Embodiment is represented. It is a flowchart showing the unsprung vibration suppression control routine concerning 3rd Embodiment. It is a schematic block diagram of the damping-force control apparatus concerning 4th Embodiment. The reference map for acquiring the specific attenuation coefficient concerning 4th Embodiment is represented. It is a flowchart showing the unsprung vibration suppression control routine concerning 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Shock absorber, 11 ... Cylinder, 12 ... Piston rod, 13 ... Piston, 14 ... Suspension member, 20 ... Coil spring, 30 ... Variable aperture mechanism, 31 ... Actuator, 40 ... Damping Force control unit (damping force ECU), 41fl, 41fr, 41rl, 41rr..., Sprung vertical acceleration sensor, 42fl, 42fr, 42rl, 42rr ... vehicle height sensor, 43 ... vehicle speed sensor, Wfl, Wfr, Wrl, Wrr ... ... wheel, A ... sprung, B ... unsprung, BD ... vehicle body, C ... damping coefficient, Ct ... specific damping coefficient, Gx ... sprung longitudinal acceleration, Gz ... sprung vertical acceleration, X …… Vehicle height, α …… Anti-tilt angle of shock absorber, β …… Angle on front and rear elastic main axis.

Claims (5)

A vehicle damping force control device that includes a shock absorber that is interposed between an unsprung portion and a sprung portion at each wheel position of the vehicle to change a damping coefficient, and controls the damping coefficient of each shock absorber. In
Unsprung vibration detecting means for detecting the vibration state of the unsprung resonance frequency band at each wheel position;
When the detected vibration level of the unsprung resonance frequency band is higher than a reference level, the shock absorber damping coefficient is determined as the relationship between the shock absorber damping coefficient and the vertical acceleration on the spring, and the shock. Based on the relationship between the damping coefficient of the absorber and the longitudinal acceleration on the spring, a spring that is set based on the specific damping coefficient is defined as a damping coefficient that minimizes the sum of the vectors of the vertical acceleration and the longitudinal acceleration. A damping force control device comprising: a lower damping control means. From the relationship between the damping coefficient of the shock absorber and the vertical acceleration on the spring and the relationship between the damping coefficient of the shock absorber and the longitudinal acceleration on the spring, the sum of the vectors of the vertical acceleration and the longitudinal acceleration is minimum. Specific attenuation coefficient acquisition means for acquiring the attenuation coefficient as a specific attenuation coefficient,
The unsprung vibration suppression control means is configured to obtain a specific damping coefficient obtained by the specific damping coefficient obtaining means when the vibration level of the detected unsprung resonance frequency band exceeds a reference level. 2. The damping force control device according to claim 1, wherein the damping force control device is set based on a coefficient. The unsprung vibration detecting means includes
Vertical acceleration detecting means for detecting the vertical acceleration of the sprung or unsprung at each wheel position;
The damping force control device according to claim 1, further comprising: an unsprung vibration component extracting unit that extracts a vibration component in an unsprung resonance frequency band from the detected vertical acceleration signal. A relative position detecting means for detecting a relative position of the unsprung direction relative to the sprung at each wheel position;
The damping force control according to any one of claims 1 to 3, further comprising vehicle height-specific specific damping coefficient changing means for changing the specific damping coefficient in accordance with the detected relative position. apparatus. Vehicle speed detection means for detecting the vehicle speed;
The damping force control device according to any one of claims 1 to 4, further comprising: a vehicle speed specific damping coefficient changing unit that changes the specific damping coefficient in accordance with the detected vehicle speed.

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