Vehicle vibration isolation device

Abstract

To enhance the anti-vibration performance within a vehicle interior by suppressing transmission of vibrations of a sub frame to a vehicle body via a plurality of mounts.SOLUTION: A vehicular anti-vibration device 11 includes: a sub frame 13 to which vibrations of wheels 2 are transmitted; a plurality of mounts 15FL, 15FR, 15RL and 15RR which are arranged between the sub frame 13 and a vehicle body 4, and are configured to change rigidities in a predetermined direction when exciting currents IFL, IFR, IRL and IRR are supplied; and a control device 18 that controls the exciting currents IFL, IFR, IRL and IRR supplied to the plurality of mounts 15FL, 15FR, 15RL and 15RR. The control device 18 sets a target elastic center of the sub frame 13, and individually calculates the exciting currents IFL, IFR, IRL and IRR supplied to the plurality of mounts 15FL, 15FR, 15RL and 15RR so as to make an actual elastic center of the sub frame 13 consistent with the target elastic center.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a vibration isolator for a vehicle.

Background Art

[0002] In recent years, efforts have been actively made to consider people in vulnerable positions such as the elderly and children among traffic participants and to provide such people with access to a sustainable transportation system. Toward that realization, research and development for further improving traffic safety and convenience through the development of vehicle habitability has drawn attention.

[0003] In order to improve vehicle habitability, it is preferable to enhance the vibration isolation performance inside the vehicle cabin. Therefore, conventionally, research and development of vehicle vibration isolators have been actively carried out. For example, Patent Document 1 discloses a vehicle including a subframe, a plurality of mounts arranged between the subframe and the vehicle body and configured to change rigidity when an excitation current is supplied, and an ECU that supplies an excitation current to the plurality of mounts.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above prior art, the ECU is configured to supply the same value of excitation current to a plurality of mounts. Therefore, when the ECU supplies an excitation current to the plurality of mounts during vehicle turning or the like, there is a risk that the vibration of the subframe is easily transmitted to the vehicle body through the plurality of mounts because the rigidity of the plurality of mounts increases simultaneously and uniformly.

[0006] In view of the above background, the present invention aims to improve vibration damping performance inside the vehicle cabin by suppressing the transmission of subframe vibrations to the vehicle body via multiple mounts. Furthermore, it aims to contribute to the development of sustainable transportation systems. [Means for solving the problem]

[0007] To solve the above problems, one aspect of the present invention provides a vehicle vibration damping device (11) comprising: a subframe (13) on which vibrations of a wheel (2) are transmitted; a plurality of mounts (15) arranged between the subframe and the vehicle body (4) and configured such that the rigidity in a predetermined direction changes when an excitation current is supplied; and a control device (18) that controls the excitation current supplied to the plurality of mounts, wherein the control device sets a target elastic center of the subframe and individually calculates the excitation current supplied to the plurality of mounts in order to make the actual elastic center of the subframe coincide with the target elastic center.

[0008] According to this embodiment, by individually calculating the excitation current supplied to multiple mounts, it is possible to suppress the simultaneous and uniform increase in the rigidity of multiple mounts. Therefore, it is possible to suppress the transmission of vibrations of the subframe to the vehicle body via multiple mounts. This improves the vibration damping performance inside the vehicle cabin and enhances the comfort of the vehicle, thereby contributing to the development of sustainable transportation systems. Furthermore, by setting a target elastic center of the subframe and matching the actual elastic center of the subframe with the target elastic center, it becomes possible to arbitrarily adjust the moment generated in the subframe.

[0009] In the above embodiment, the vehicle vibration damping device further comprises a yaw rate sensor (16) for detecting the yaw rate of the vehicle body and a vehicle speed sensor (17) for detecting the vehicle speed, and the control device may individually calculate the excitation current supplied to the plurality of mounts by calculating a reference current value based on the yaw rate and the vehicle speed, calculating a correction coefficient for each mount based on the target elastic center, and correcting the reference current value based on the correction coefficient for each mount.

[0010] According to this embodiment, an appropriate excitation current can be supplied to multiple mounts based on the yaw rate, vehicle speed, and target elastic center.

[0011] In the above embodiment, the plurality of mounts include first and second mounts spaced apart in an orthogonal direction perpendicular to the predetermined direction, and the orthogonal distance between the target elastic center and the first mount is defined as the first distance, and the orthogonal distance between the target elastic center and the second mount is defined as the second distance. The control device may calculate the correction coefficient for the first mount by dividing the second distance by the sum of the first distance and the second distance, and calculate the correction coefficient for the second mount by dividing the first distance by the sum of the first distance and the second distance.

[0012] According to this embodiment, the correction coefficient for each mount can be easily and appropriately calculated.

[0013] In the above embodiment, the control device stores a correction coefficient table that defines the correction coefficient for each mount, and may calculate the correction coefficient for each mount by referring to the correction coefficient table.

[0014] According to this embodiment, the correction coefficient for each mount can be easily and appropriately calculated.

[0015] In the above embodiment, the plurality of mounts are configured such that their vertical rigidity changes when the excitation current is supplied, the subframe has vibration input points to which the vibration of the wheels is input, and the control device may set the target elastic center such that the longitudinal position of the vibration input points coincides with the longitudinal position of the target elastic center.

[0016] According to this embodiment, the pitch moment generated in the subframe can be suppressed. Therefore, the transmission of vibrations from the subframe to the vehicle body via multiple mounts can be suppressed more effectively.

[0017] In the above embodiment, the vehicle vibration damping device further comprises a vehicle speed sensor for detecting vehicle speed, the plurality of mounts are configured such that their rigidity in the lateral direction changes when the excitation current is supplied, and the control device may change the target elastic center in the longitudinal direction based on the vehicle speed.

[0018] According to this embodiment, the direction and magnitude of the yaw moment can be adjusted according to the vehicle speed. [Effects of the Invention]

[0019] According to the above embodiment, it is possible to suppress the transmission of vibrations from the subframe to the vehicle body via multiple mounts. [Brief explanation of the drawing]

[0020] [Figure 1] Plan view showing a vehicle to which the vehicle vibration damping device according to the first embodiment is applied. [Figure 2] Rear view showing a vehicle vibration damping device according to the first embodiment. [Figure 3] Cross-sectional view showing the mount according to the first embodiment. [Figure 4] Functional block diagram showing a vehicle vibration damping device according to the first embodiment. [Figure 5] A schematic diagram showing the state in which a magnetic field is applied to the magnetic medium according to the first embodiment. [Figure 6]Side view showing the method for setting the target elastic center 1 and the method for calculating the correction coefficient for each mount 1 according to the first embodiment. [Figure 7] Plan view showing the method for setting the target elastic center 2 and the method for calculating the correction coefficient for each mount 2 according to the first embodiment. [Figure 8] Functional block diagram showing a vehicle vibration damping device according to the second embodiment. [Figure 9] Table showing the correction coefficient table according to the second embodiment. [Modes for carrying out the invention]

[0021] (First Embodiment) The first embodiment of the present invention will be described below with reference to Figures 1 to 7.

[0022] <Vehicle vibration damping device 11> Figure 1 is a plan view showing a vehicle 1 to which a vehicle vibration damping device 11 according to the first embodiment (hereinafter abbreviated as "vibration damping device 11") is applied. The vibration damping device 11 comprises a subframe 13 connected to the left and right front wheels 2 (an example of wheels) via left and right arm members 3, left and right suspensions 14 positioned between the left and right arm members 3 and the vehicle body 4 (only the outer shape is shown in Figure 1), four mounts 15FL, 15FR, 15RL, and 15RR positioned between the subframe 13 and the vehicle body 4, a yaw rate sensor 16 for detecting the yaw rate Y of the vehicle 1, a vehicle speed sensor 17 for detecting the vehicle speed V, and a control device 18 for controlling the four mounts 15FL, 15FR, 15RL, and 15RR based on the yaw rate Y and vehicle speed V.

[0023] <Subframe 13> Referring to Figures 1 and 2, the subframe 13 of the vibration damping device 11 is located below the front of the vehicle body 4. The subframe 13 has a roughly rectangular shape in plan view. The subframe 13 supports the on-board components 21. The on-board components 21 include, for example, a drive source for driving, such as an internal combustion engine or an electric motor. Furthermore, the on-board components 21 may also include a generator, differential gear, fuel tank, transmission, etc. The on-board components 21 are omitted from the illustration except in Figure 1.

[0024] Referring to Figure 2, vibrations from the front wheels 2 based on the road surface input Z are transmitted to the subframe 13 via the left and right arm members 3. More specifically, vibrations from the front wheels 2 based on the road surface input Z are input to the vibration input point B of the subframe 13 via the left and right arm members 3. For example, the vibration input point B is the connection point between the left and right arm members 3 on the subframe 13.

[0025] <Left and right suspension 14> The left and right suspensions 14 of the vibration isolation device 11 have springs and shock absorbers (neither of which are shown). In this embodiment, the left and right suspensions 14 are positioned between the left and right arm members 3 and the vehicle body 4, but in other embodiments, the left and right suspensions 14 may be positioned between the left and right front wheels 2 and the vehicle body 4. The left and right suspensions 14 are omitted from the illustration except in Figures 1 and 2.

[0026] <4 mounts for 15FL, 15FR, 15RL, 15RR> Referring to Figure 1, the four mounts 15FL, 15FR, 15RL, and 15RR of the vibration isolation device 11 are positioned at the front left corner, front right corner, rear left corner, and rear right corner of the subframe 13, respectively. The front mounts 15FL and 15FR and the rear mounts 15RL and 15RR are spaced apart in the front-to-back direction. Hereafter, when the four mounts 15FL, 15FR, 15RL, and 15RR are not distinguished, they will simply be referred to as "mount 15".

[0027] Referring to Figure 3, the mount 15 is composed of a variable-rigidity mount whose rigidity can be changed. The mount 15 includes an inner cylinder 23, an excitation coil 24, a mount rubber 25, an outer cylinder 26, upper and lower cores 27, and upper and lower magnetic media 28. In the following description of the mount 15, when "radially outward" or "radially inward" is used, it refers to the radially outward or inward direction with respect to axis A extending vertically from the center of the mount 15.

[0028] The inner cylinder 23 of the mount 15 is made of a magnetic material. The inner cylinder 23 is cylindrical in shape with axis A as its center. The inner cylinder 23 is fixed to the underside of the vehicle body 4 by a fastening member 31 consisting of a bolt 31A and a nut 31B. A recess 32 is provided on the outer circumferential surface of the inner cylinder 23.

[0029] The excitation coil 24 of the mount 15 is cylindrical in shape with axis A as its center. The excitation coil 24 is positioned radially outward of the inner cylinder 23. The radially inward portion of the excitation coil 24 is fitted into a recess 32 of the inner cylinder 23.

[0030] The mounting rubber 25 of the mount 15 is cylindrical in shape with axis A as its center. The mounting rubber 25 is positioned radially outward from the inner cylinder 23 and the excitation coil 24. The vertical width of the mounting rubber 25 matches the vertical width of the excitation coil 24.

[0031] The outer cylinder 26 of the mount 15 is made of a magnetic material. The outer cylinder 26 is cylindrical with axis A as its center. The outer cylinder 26 is positioned radially outward of the inner cylinder 23, the excitation coil 24, and the mount rubber 25. The vertical width of the outer cylinder 26 is greater than the vertical width of the excitation coil 24 and the mount rubber 25. The outer cylinder 26 is fixed to the subframe 13 by fitting into a fitting hole 13A provided in the subframe 13.

[0032] The core 27 of the mount 15 has a cylindrical tube portion 34 centered on axis A, and an annular flange portion 35 extending radially outward from one end of the tube portion 34 in the vertical direction (the end furthest from the excitation coil 24). The tube portion 34 is located radially outward of the inner cylinder 23. The tube portion 34 is located on one side in the vertical direction of the radially outward portion of the excitation coil 24. The flange portion 35 is located on one side in the vertical direction of the mount rubber 25 and the outer cylinder 26.

[0033] The magnetic medium 28 of the mount 15 is composed of a magnetic viscoelastic elastomer (MRE). In other embodiments, the magnetic medium 28 may be composed of a magnetic viscoelastic fluid (MRF) or a magnetic viscoelastic compound (MRC). The magnetic medium 28 is located in the space defined by the mount rubber 25, the outer cylinder 26, and the core 27.

[0034] <Yaw rate sensor 16> Referring to Figure 1, the yaw rate sensor 16 of the vibration isolation device 11 is positioned, for example, near the center of gravity of the vehicle body 4. The yaw rate sensor 16 detects the yaw rate Y (angular velocity around the vertical axis) of the vehicle body 4 and outputs the detected yaw rate Y to the control device 18.

[0035] <Vehicle speed sensor 17> The vehicle speed sensor 17 of the vibration isolation device 11 is composed of, for example, wheel speed sensors provided on each of the multiple wheels (front wheels 2 and rear wheels 5). The vehicle speed sensor 17 detects the vehicle speed V and outputs the detected vehicle speed V to the control device 18.

[0036] <Control device 18> The control device 18 of the vibration isolation device 11 is an electronic control unit (ECU) that includes a processing unit (CPU, MPU, etc.) and a memory device (ROM, RAM, etc.). The control device 18 may be configured as a single piece of hardware, or as a unit consisting of multiple pieces of hardware.

[0037] Referring to Figure 4, the control device 18 controls the excitation current I of the mount 15 (excitation current I of the mount 15FL). FL Excitation current I of mount 15FR FR Excitation current I of mount 15RL RL , and the excitation current I of Mount 15RR RR This is a device that controls the following. The control device 18 includes, as functional components, a reference current value calculation unit 41, a target elastic center setting unit 42, and a current value correction unit 43.

[0038] <Reference current value calculation unit 41> The reference current value calculation unit 41 of the control device 18 stores a reference current value map Mr. The reference current value map Mr is a map that defines the relationship between the yaw rate Y, the vehicle speed V, and the reference current value Ir. For example, the lines v1, v2, and v3 in Figure 4 show the relationship between the yaw rate Y and the reference current value Ir when the vehicle speed V = v1, v2, and v3 (where v1 > v2 > v3), respectively. The reference current value map Mr is set so that the reference current value Ir increases as the yaw rate Y increases. The reference current value map Mr is set so that the reference current value Ir increases as the vehicle speed V increases.

[0039] The reference current value calculation unit 41 calculates the reference current value Ir by referring to the reference current value map Mr based on the yaw rate Y and vehicle speed V. The reference current value calculation unit 41 outputs the calculated reference current value Ir to the current value correction unit 43.

[0040] <Target elastic center setting section 42> The target elastic center setting unit 42 of the control device 18 sets the target elastic center Et (target rotation center) of the subframe 13. Based on the set target elastic center Et, the target elastic center setting unit 42 determines the correction coefficient C for each mount 15 (the correction coefficient C for mount 15FL FL , the correction coefficient C for mount 15FR FR , the correction coefficient C for mount 15RL RL , and the correction coefficient C for mount 15RR RR ). Note that the method for setting the target elastic center Et and the method for calculating the correction coefficient C for each mount 15 will be described later. The target elastic center setting unit 42 outputs the calculated correction coefficient C for each mount 15 to the current value correction unit 43.

[0041] <Current value correction unit 43> Based on the reference current value Ir output from the reference current value calculation unit 41 and the correction coefficient C for each mount 15 output from the target elastic center setting unit 42, the current value correction unit 43 of the control device 18 individually calculates the excitation current I supplied to the excitation coil 24 of the mount 15. More specifically, the current value correction unit 43 individually calculates the excitation current I supplied to the excitation coil 24 of the mount 15 by correcting the reference current value Ir based on the correction coefficient C for each mount 15.

[0042] For example, the current value correction unit 43 multiplies the reference current value Ir by the correction coefficient C for mount 15FL FL to calculate the excitation current I for mount 15FL FL . Similarly, the current value correction unit 43 multiplies the reference current value Ir by the correction coefficients C for mounts 15FR, 15RL, and 15RR FR , C RL , C RR to calculate the excitation currents I for mounts 15FR, 15RL, and 15RR FR , I RL , I RR .

[0043] <Change in the rigidity of mount 15> Referring to Figure 5, the magnetic medium 28 of the mount 15 is formed by dispersing magnetic particles 46 (e.g., iron powder) in an elastic body 45 such as silicone rubber. When an external magnetic field (see dashed arrow in Figure 5) is applied to the magnetic medium 28, the magnetic particles 46 are arranged in a chain-like manner along the direction of the magnetic field, thereby hindering the movement of the elastic body 45 in a direction perpendicular to the direction of the magnetic field. As a result, the viscosity of the magnetic medium 28 in the direction perpendicular to the direction of the magnetic field increases, and the rigidity of the mount 15 in the direction perpendicular to the direction of the magnetic field increases.

[0044] Referring to Figure 3, when an excitation current I is supplied to the excitation coil 24 of the mount 15, the excitation coil 24 generates a magnetic field (see dashed arrow in Figure 3). As a result, a magnetic field in the vertical direction is applied to the magnetic medium 28 in region R1 of Figure 3. Therefore, the viscosity of the magnetic medium 28 in the horizontal direction (front, back, left, and right directions) increases, and the rigidity of the mount 15 in the horizontal direction increases. Also, in region R2 of Figure 3, a magnetic field in the horizontal direction (more specifically, the radial direction centered on axis A) is applied to the magnetic medium 28. Therefore, the viscosity of the magnetic medium 28 in the vertical direction increases, and the rigidity of the mount 15 in the vertical direction increases.

[0045] <Method 1 for setting the target elastic center Et and method 1 for calculating the correction coefficient C for each mount> Figure 6(a) shows a state where the longitudinal position of the vibration input point B and the longitudinal position of the actual elastic center Ea of the subframe 13 (actual rotation center: hereinafter referred to as "actual elastic center Ea") are misaligned. In this state, when vibrations from the front wheel 2 based on the road surface input Z are input to the subframe 13 via the vibration input point B, a pitch moment Mp corresponding to the longitudinal distance Q between the actual elastic center Ea and the vibration input point B is generated in the subframe 13. This may amplify the vibration of the subframe 13.

[0046] In contrast, Figure 6(b) shows a state in which the longitudinal position of the vibration input point B coincides with the longitudinal position of the real elastic center Ea of the subframe 13. In this state, even if vibrations from the front wheel 2 are input to the subframe 13 via the vibration input point B, the pitch moment Mp described above is unlikely to occur in the subframe 13, and mainly translational motion W (vertical motion) occurs in the subframe 13. This suppresses the amplification of vibrations in the subframe 13 and improves the handling stability of the vehicle 1.

[0047] Therefore, as shown in Figure 6(c), the target elastic center setting unit 42 sets the target elastic center Et such that the position of the vibration input point B in the longitudinal direction coincides with the position of the target elastic center Et in the longitudinal direction. Furthermore, the target elastic center setting unit 42 calculates a correction coefficient C for each mount 15 based on the set target elastic center Et. For example, the target elastic center setting unit 42 calculates the correction coefficient C for the front mounts 15FL and 15FR (an example of the first mount) using the following equation (1). FL , C FR The correction coefficient C for the rear mounts 15RL and 15RR (an example of the second mount) is calculated using the following equation (2). RL , C RR The following is calculated. In equations (1) and (2) below, Da represents the distance in the longitudinal direction between the target elastic center Et and the front mounts 15FL and 15FR (an example of the first distance: hereinafter referred to as "distance Da"). In equations (1) and (2) below, Db represents the distance in the longitudinal direction between the target elastic center Et and the rear mounts 15RL and 15RR (an example of the second distance: hereinafter referred to as "distance Db"). C FL =C FR =Db / (Da+Db)...(1) C RL =C RR =Da / (Da+Db)...(2)

[0048] As is clear from equation (1) above, the target elastic center setting unit 42 divides the distance Db by the sum of the distance Da and the distance Db, thereby calculating the correction coefficient C of the front mounts 15FL and 15FR. FL , C FRThe following is calculated. Furthermore, as is clear from equation (2) above, the target elastic center setting unit 42 calculates the correction coefficient C of the rear mounts 15RL and 15RR by dividing the distance Da by the sum of the distance Da and the distance Db. RL , C RR Calculate.

[0049] For example, if the target elastic center Et is moved backward from the position shown in Figure 6(c), the distance Da in equation (1) above increases, while the distance Db in equation (2) above decreases. As a result, the correction coefficient C of the front mounts 15FL and 15FR changes. FL , C FR The size decreases, and the correction coefficient C of the rear mounts 15RL and 15RR RL , C RR Because it becomes larger, the excitation current I of the front mounts 15FL and 15FR FL , I FR The excitation current of the rear mounts 15RL and 15RR decreases, and I RL , I RR This increases the vertical stiffness of the front mounts 15FL and 15FR, and the vertical stiffness of the rear mounts 15RL and 15RR increases, causing the actual elastic center Ea to move backward. On the other hand, if the target elastic center Et is moved forward from the position shown in Figure 6(c), the actual elastic center Ea will move forward by the opposite of the above. In this way, by determining the correction coefficient C for each mount 15 using equations (1) and (2) above, the actual elastic center Ea can be made to match the target elastic center Et.

[0050] <Method 2 for setting the target elastic center Et and method 2 for calculating the correction coefficient C for each mount 15> As shown in Figure 7(a), when the actual elastic center Ea of the subframe 13 is located in front of the vibration input point B, a yaw moment is generated in the subframe 13 in a direction that coincides with the turning direction of the vehicle body 4 when the vehicle body 4 turns, thus improving the turning ability of the vehicle body 4. Therefore, when the vehicle 1 is traveling at low speeds, it is preferable that the actual elastic center Ea of the subframe 13 is located in front of the vibration input point B in order to improve the turning ability of the vehicle body 4.

[0051] On the other hand, as shown in Figure 7(b), when the actual elastic center Ea of the subframe 13 is located behind the vibration input point B, a yaw moment opposite to the turning direction of the vehicle body 4 is generated in the subframe 13 when the vehicle body 4 turns, thus improving the stability of the vehicle body 4. Therefore, when the vehicle 1 is traveling at high speed, it is preferable that the actual elastic center Ea of the subframe 13 be located behind the vibration input point B in order to improve the stability of the vehicle body 4.

[0052] Therefore, the target elastic center setting unit 42 sets the target elastic center Et of the subframe 13 in front of the vibration input point B when the vehicle speed V output from the vehicle speed sensor 17 is equal to or greater than a predetermined threshold speed (when the vehicle 1 is traveling at high speed). On the other hand, the target elastic center setting unit 42 sets the target elastic center Et of the subframe 13 behind the vibration input point B when the vehicle speed V output from the vehicle speed sensor 17 is less than the above threshold speed (when the vehicle 1 is traveling at low speed). In this embodiment, the target elastic center setting unit 42 changes the target elastic center Et in two stages in the longitudinal direction, but in other embodiments, the target elastic center setting unit 42 may change the target elastic center Et in three or more stages in the longitudinal direction.

[0053] The target elastic center setting unit 42 sets a correction coefficient C for each mount 15 based on the set target elastic center Et. For example, the target elastic center setting unit 42 sets the correction coefficient C for the front mounts 15FL and 15FR (an example of the first mount) according to equation (3) below. FL , C FR The correction coefficient C for the rear mounts 15RL and 15RR (an example of the second mount) is calculated using the following formula (4). RL , C RR The following is calculated. Note that Dc in equations (3) and (4) below represents the distance in the longitudinal direction between the target elastic center Et and the front mounts 15FL and 15FR (an example of the first distance: hereinafter referred to as "distance Dc"). Also, Dd in equations (3) and (4) below represents the distance in the longitudinal direction between the target elastic center Et and the rear mounts 15RL and 15RR (an example of the second distance: hereinafter referred to as "distance Dd"). C FL =C FR =Dd / (Dc+Dd)...(3) C RL =C RR =Dc / (Dc+Dd)...(4)

[0054] As is clear from equation (3) above, the target elastic center setting unit 42 divides the distance Dd by the sum of the distances Dc and Dd to obtain the correction coefficient C of the front mounts 15FL and 15FR. FL , C FR The following is calculated. Furthermore, as is clear from equation (4) above, the target elastic center setting unit 42 calculates the correction coefficient C of the rear mounts 15RL and 15RR by dividing the distance Dc by the sum of the distance Dc and the distance Dd. RL , C RR Calculate.

[0055] Referring to Figure 7(a), when the target elastic center Et is set forward of the vibration input point B, the distance Dd in equations (3) and (4) above becomes larger than the distance Dc in equations (3) and (4) above. As a result, the correction coefficient C of the front mounts 15FL and 15FR becomes larger. FL , C FR The correction coefficient C for the rear mounts 15RL and 15RR. RL , C RR Because it becomes larger than the front mounts 15FL and 15FR, the excitation current I FL , I FR The excitation current I of the rear mounts 15RL and 15RR RL , I RR This becomes larger than the actual elastic center Ea. As a result, the lateral stiffness of the front mounts 15FL and 15FR becomes greater than the lateral stiffness of the rear mounts 15RL and 15RR, so that the actual elastic center Ea is positioned in front of the vibration input point B. Referring to Figure 7(b), if the target elastic center Et is set behind the vibration input point B, the actual elastic center Ea is positioned behind the vibration input point B due to the opposite effect. In this way, by determining the correction coefficient C for each mount 15 using equations (3) and (4) above, the actual elastic center Ea can be made to match the target elastic center Et.

[0056] <Method 3 for setting the target elastic center Et and method 3 for calculating the correction coefficient C for each mount 15> The target elastic center setting unit 42 sets the target elastic center Et in the same manner as the target elastic center setting method 1 described above. Alternatively, the target elastic center setting unit 42 may set the target elastic center Et in the same manner as the target elastic center setting method 2 described above.

[0057] The target elastic center setting unit 42 calculates a correction coefficient C for each mount 15 based on the set target elastic center Et. More specifically, the target elastic center setting unit 42 uses computer simulations or the like to calculate the target spring ratios for the front mounts 15FL, 15FR and the rear mounts 15RL, 15RR according to the target elastic center Et. Furthermore, the target elastic center setting unit 42 sets a correction coefficient C for each mount 15 based on the calculated target spring ratios.

[0058] For example, if the target spring ratio of the front mounts 15FL and 15FR and the rear mounts 15RL and 15RR is 1:X, the target elastic center setting section 42 adjusts the correction coefficient C of the front mounts 15FL and 15FR according to equation (5) below. FL , C FR Set the following equation (6) and the correction coefficient C of the rear mounts 15RL and 15RR RL , C RR Set it. C FL =C FR =1 C RL =C RR =X

[0059] <Effects of the First Embodiment> In the first embodiment described above, the control device 18 increases the reference current value Ir as the yaw rate Y increases (see the reference current value map Mr in Figure 4). Therefore, as the yaw rate Y increases in accordance with the turning of the vehicle 1, the reference current value Ir increases, and the excitation current I supplied to the mount 15 also increases, thereby increasing the rigidity of the mount 15. This improves the handling stability of the vehicle 1 when it is turning.

[0060] On the other hand, if the rigidity of multiple mounts 15 increases simultaneously and uniformly, there is a risk that vibrations from the subframe 13 will be more easily transmitted to the vehicle body 4 via the multiple mounts 15. Therefore, the control device 18 individually calculates the excitation current I supplied to each of the multiple mounts 15. This makes it possible to suppress the simultaneous and uniform increase in the rigidity of multiple mounts 15. As a result, it is possible to suppress the transmission of vibrations from the subframe 13 to the vehicle body 4 via the multiple mounts 15, thereby improving the vibration damping performance inside the vehicle cabin.

[0061] Furthermore, the control device 18 sets a target elastic center Et for the subframe 13 and aligns the actual elastic center Ea of the subframe 13 with the target elastic center Et. This makes it possible to arbitrarily adjust the moments (e.g., pitch moment and yaw moment) generated in the subframe 13.

[0062] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figures 8 and 9. Descriptions that overlap with the first embodiment of the present invention will be omitted as appropriate.

[0063] <Vehicle vibration isolation device 51> Figure 8 is a functional block diagram showing a vehicle vibration damping device 51 (hereinafter abbreviated as "vibration damping device 51") according to the second embodiment. Note that, apart from the four mounts 53FL, 53FR, 53RL, and 53RR and the control device 54, the configuration of the vibration damping device 51 is the same as in the first embodiment, so a description is omitted.

[0064] <4 mounts for 53FL, 53FR, 53RL, 53RR> The four mounts 53FL, 53FR, 53RL, and 53RR of the vibration isolation device 51 are positioned at the front left corner, front right corner, rear left corner, and rear right corner of the subframe 13, respectively, similar to the four mounts 15FL, 15FR, 15RL, and 15RR of the first embodiment. Hereafter, when the four mounts 53FL, 53FR, 53RL, and 53RR are not distinguished, they will simply be referred to as "mount 53".

[0065] Each mount 53 is equipped with three excitation coils 56X, 56Y, and 56Z. When current is supplied to excitation coil 56X, it generates a magnetic field perpendicular to the X-axis direction (front-to-back direction), thereby increasing the rigidity of mount 53 in the X-axis direction. When current is supplied to excitation coil 56Y, it generates a magnetic field perpendicular to the Y-axis direction (left-to-right direction), thereby increasing the rigidity of mount 53 in the Y-axis direction. When current is supplied to excitation coil 56Z, it generates a magnetic field perpendicular to the Z-axis direction (up-down direction), thereby increasing the rigidity of mount 53 in the Z-axis direction. In this way, mount 53 is configured to independently change the rigidity in the three axial directions.

[0066] <Control device 54> The control device 54 includes, as functional components, a reference current value calculation unit 58, a target elastic center setting unit 59, and a current value correction unit 60. Note that the configuration of the reference current value calculation unit 58 is the same as that of the reference current value calculation unit 41 according to the first embodiment, and therefore its description is omitted.

[0067] <Target elastic center setting section 59> Referring to Figure 9, the target elastic center setting unit 59 of the control device 54 stores a correction coefficient table T. The correction coefficient table T defines the correction coefficient C for each axial direction of the mount 53 according to the vehicle speed V. For example, the correction coefficient table T defines the correction coefficient C for the X-axis direction of the mount 53FL. FLX , Mount 53FL Y-axis correction coefficient C FLY , and the Z-axis correction coefficient C of mount 53FL FLZ It specifies the following. Similarly, the correction factor table T specifies the correction factors C for the X, Y, and Z axes of mounts 53FR, 53RL, and 53RR, respectively.

[0068] The target elastic center setting unit 59 calculates the correction coefficient C for each axial direction of the mount 53 by referring to the correction coefficient table T based on the vehicle speed V output from the vehicle speed sensor 17. The target elastic center setting unit 59 outputs the set correction coefficient C for each axial direction of the mount 53 to the current value correction unit 60.

[0069] <Current value correction unit 60> The current value correction unit 60 of the control device 54 calculates the excitation current I for each axial direction of the mount 53 individually by correcting the reference current value Ir based on the correction coefficient C for each axial direction of the mount 53. For example, the current value correction unit 60 calculates the excitation current I for each axial direction of the mount 53 based on the reference current value Ir and the correction coefficient C FLX , C FLY , C FLZ By multiplying these together, the excitation current I for each axial direction of the mount 53 is obtained. FLX , I FLY , I FLZ These are calculated individually. The current value correction unit 60 outputs the calculated excitation current I for each axial direction of the mount 53 to the excitation coils 56X, 56Y, and 56Z of the mount 53. As a result, the rigidity of the mount 53 changes independently in each axial direction.

[0070] <Effects of the second embodiment> As described above, in the second embodiment, the control device 54 independently changes the axial rigidity of the mount 53. This makes it possible to simultaneously suppress the pitch moment, roll moment, and yaw moment generated in the subframe 13. Consequently, the current required to ensure handling stability can be reduced, and the increase in vibration and noise can be suppressed.

[0071] Furthermore, the correction coefficient table T specifies the axial correction coefficient C of the mount 53 according to the vehicle speed V. This makes it easy to set the axial correction coefficient C of the mount 53 according to the vehicle speed V.

[0072] <Modified form of the second embodiment> In the second embodiment, the mount 53 is configured to independently change the stiffness in three axial directions. On the other hand, if a mount is used in which the stiffness in three axial directions is interdependent (see the first embodiment), the control device 54 may predetermine the priority of the three axial directions and output an excitation current I so that the stiffness of the mount 53 in the axial direction with the highest priority matches the target value.

[0073] This concludes the description of specific embodiments, but the present invention is not limited to the above embodiments or modifications and can be broadly modified and implemented. [Explanation of Symbols]

[0074] 1: Vehicle 2: Front wheel (an example of a wheel) 4: Vehicle body 11: Vehicle vibration isolation device 13: Subframe 15: Mount 16: Yaw rate sensor 17: Vehicle speed sensor 18: Control device 51: Vehicle vibration isolation device 53: Mount 54: Control device B: Vibration input point C: Correction factor Da: distance Db: distance Dc: distance Dd: distance Ea: Actual elastic center Et: Target elastic center I: Excitation current Ir: Reference current value T: Correction coefficient table V:Vehicle speed Y: Yaw rate

Claims

1. A vibration damping device for vehicles, The subframe through which wheel vibrations are transmitted, A plurality of mounts are positioned between the subframe and the vehicle body, and are configured such that their rigidity in a predetermined direction changes when an excitation current is supplied to them. A yaw rate sensor for detecting the yaw rate of the vehicle body, A vehicle speed sensor that detects vehicle speed, The system includes a control device that controls the excitation current supplied to the plurality of mounts, The control device is The target elastic center of the subframe is set, In order to make the actual elastic center of the subframe coincide with the target elastic center, A reference current value is calculated based on the yaw rate and the vehicle speed. Based on the target elastic center, a correction coefficient is calculated for each mount. A vehicle vibration damping device that calculates the excitation current supplied to each of the multiple mounts individually by correcting the reference current value based on the correction coefficient for each of the mounts.

2. The plurality of mounts include first and second mounts that are spaced apart in a front-to-back direction perpendicular to the predetermined direction, When the distance in the front-rear direction between the target elastic center and the first mount is defined as the first distance, and the distance in the front-rear direction between the target elastic center and the second mount is defined as the second distance, The vehicle vibration damping device according to claim 1, wherein the control device calculates the correction coefficient of the first mount by dividing the second distance by the sum of the first distance and the second distance, and calculates the correction coefficient of the second mount by dividing the first distance by the sum of the first distance and the second distance.

3. The vehicle vibration damping device according to claim 1, wherein the control device stores a correction coefficient table that defines the correction coefficient for each mount, and calculates the correction coefficient for each mount by referring to the correction coefficient table.

4. The aforementioned plurality of mounts are configured such that their rigidity in the vertical direction changes when the excitation current is supplied. The subframe has vibration input points to which the vibrations of the wheels are input, The vehicle vibration isolation device according to any one of claims 1 to 3, wherein the control device sets the target elastic center such that the position of the vibration input point in the longitudinal direction coincides with the position of the target elastic center in the longitudinal direction.

5. The plurality of mounts are configured such that their rigidity in the left-right direction changes when the excitation current is supplied, The vehicle vibration damping device according to any one of claims 1 to 3, wherein the control device changes the target elastic center in the longitudinal direction based on the vehicle speed.

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