Damping device for a vehicle

Abstract

A damping device for a vehicle includes a sub-frame to which a wheel's vibration is transmitted, a plurality of supports arranged between the sub-frame and a vehicle body and configured to change a rigidity of each support in a prescribed direction in accordance with an excitation current supplied thereto, and a controller configured to control the excitation current supplied to each support, wherein the controller is configured to set a target elastic center of the sub-frame, and individually calculate the excitation current supplied to each support so as to match an actual elastic center of the sub-frame to the target elastic center.

Description

TECHNICAL FIELD

[0001] The present application relates to a vibration damping device for a vehicle. BACKGROUND

[0002] In recent years, in consideration of vulnerable people such as the elderly and children among traffic participants, active efforts have been made to provide sustainable traffic systems for these people. In order to achieve this goal, research and development have been closely followed in order to further improve the safety and convenience of traffic by developing the livability of vehicles.

[0003] In order to improve the livability of vehicles, it is preferable to improve the vibration damping performance of the vehicle cabin. Conventionally, research and development of vehicle vibration damping devices have been actively conducted. For example, Japanese Patent No. 6576412 discloses a vehicle including a sub-frame, a plurality of supports arranged between the sub-frame and a vehicle body, the supports being configured such that the stiffness of each support varies according to an excitation current supplied thereto, and an ECU configured to supply the excitation current to each support.

[0004] However, in the above conventional technology, the ECU is configured to supply the excitation current of the same value to the plurality of supports. Therefore, if the ECU supplies the excitation current to each support when the vehicle is turning, the stiffness of the plurality of supports simultaneously and uniformly increases, which can cause the vibration of the sub-frame to be easily transmitted to the vehicle body via the plurality of supports. SUMMARY

[0005] In view of the above background, an object of the present application is to improve the vibration damping performance in the vehicle cabin by preventing the vibration of the sub-frame from being transmitted to the vehicle body via the plurality of supports, and thus to contribute to the development of sustainable traffic systems.

[0006] In order to achieve this object, one aspect of the present application provides a vibration damping device 11 for a vehicle 1, the vibration damping device including: a sub-frame 13 to which the vibration of a wheel 2 is transmitted; a plurality of supports 15 arranged between the sub-frame and a vehicle body 4, the plurality of supports being configured such that the stiffness of each support in a prescribed direction varies according to an excitation current supplied thereto; and a controller 18 configured to control the excitation current supplied to each support, wherein the controller is configured to: set a target elastic center of the sub-frame; and individually calculate the excitation current supplied to each support so as to match an actual elastic center of the sub-frame to the target elastic center.

[0007] According to this aspect, by individually calculating the excitation current supplied to each support, it is possible to prevent the stiffness of the plurality of supports from simultaneously and uniformly increasing. Therefore, it is possible to prevent the vibration of the subframe from being transmitted to the vehicle body via the plurality of supports. Thus, it is possible to improve the vibration damping performance in the vehicle cabin, and thus it is possible to improve the livability of the vehicle. Therefore, it is possible to contribute to the development of a sustainable transportation system. Furthermore, by setting the target elastic center of the subframe and matching the actual elastic center of the subframe with the target elastic center, it is possible to freely adjust the moment generated on the subframe.

[0008] In the above aspect, preferably, the vibration damping device further includes a yaw rate sensor 16 configured to detect a yaw rate of the vehicle body, and a vehicle speed sensor 17 configured to detect a vehicle speed, wherein the controller is configured to calculate a reference current value based on the yaw rate and the vehicle speed, calculate a correction coefficient of each support based on the target elastic center, and individually calculate the excitation current supplied to each support by correcting the reference current value based on the correction coefficient of each support.

[0009] According to this aspect, it is possible to supply an appropriate size of excitation current to the plurality of supports in accordance with the yaw rate, the vehicle speed, and the target elastic center.

[0010] In the above aspect, preferably, the plurality of supports include a first support and a second support arranged at a certain interval in a vertical direction perpendicular to the prescribed direction, and in a case where a distance in the vertical direction between the target elastic center and the first support is defined as a first distance and a distance in the vertical direction between the target elastic center and the second support is defined as a second distance, the controller is configured to calculate the correction coefficient of the first support by dividing the second distance by a sum of the first distance and the second distance, and calculate the correction coefficient of the second support by dividing the first distance by the sum of the first distance and the second distance.

[0011] According to this aspect, it is possible to easily and appropriately calculate the correction coefficient of each support.

[0012] In the above aspect, preferably, the controller is configured to store a correction coefficient table defining the correction coefficient of each support, and calculate the correction coefficient of each support by referring to the correction coefficient table.

[0013] According to this aspect, it is possible to easily and appropriately calculate the correction coefficient of each support.

[0014] In the above aspect, preferably, the plurality of supports are configured so that a rigidity of each support in the up-and-down direction varies according to the excitation current supplied thereto, the sub-frame has a vibration input point into which a vibration of the wheel is input, and the controller is configured to set the target elastic center so that a front-and-rear position of the vibration input point matches a front-and-rear position of the target elastic center.

[0015] According to this aspect, the pitch moment generated at the sub-frame can be suppressed. Therefore, the vibration of the sub-frame can be more effectively prevented from being transmitted to the vehicle body via the plurality of supports.

[0016] In the above aspect, preferably, the vibration damping device further includes a vehicle speed sensor configured to detect a vehicle speed, wherein the plurality of supports are configured so that a rigidity of each support in the lateral direction varies according to the excitation current supplied thereto, and the controller is configured to change the target elastic center in the front-and-rear direction based on the vehicle speed.

[0017] According to this aspect, the direction and the magnitude of the yaw moment can be adjusted according to the vehicle speed.

[0018] Therefore, according to the above aspect, the vibration of the sub-frame can be prevented from being transmitted to the vehicle body via the plurality of supports. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a plan view showing a vehicle to which the vibration damping device for a vehicle according to the first embodiment is applied;

[0020] Figure 2 is a rear view showing the vibration damping device according to the first embodiment;

[0021] Figure 3 is a sectional view showing a support according to the first embodiment;

[0022] Figure 4 is a functional block diagram showing the vibration damping device according to the first embodiment;

[0023] Figure 5 is a schematic view showing a state in which a magnetic field according to the first embodiment is applied to a magnetic medium;

[0024] Figures 6A to 6C is a side view showing a setting method 1 of a target elastic center and a calculation method 1 of a correction coefficient of each support according to the first embodiment;

[0025] Figure 7A and Figure 7B is a plan view showing a setting method 2 of a target elastic center and a calculation method 2 of a correction coefficient of each support according to the first embodiment;

[0026] Figure 8 This is a functional block diagram illustrating a vibration damping device for a vehicle according to a second embodiment; and

[0027] Figure 9 A table of correction coefficients according to the second embodiment is shown. Detailed Implementation

[0028] (First Implementation)

[0029] The following text will refer to Figures 1 to 7B The first embodiment of the present invention will be described below.

[0030] <Shock damping device for vehicles 11>

[0031] Figure 1 This is a plan view of vehicle 1, which utilizes a vehicle damping device 11 (hereinafter simply referred to as "dampening device 11") according to a first embodiment. The damping device 11 includes: a subframe 13 connected to the left and right front wheels 2 (in an embodiment of wheels) via left and right arms 3; and left and right suspensions 14 arranged between the left and right arms 3 and the vehicle body 4. Figure 1 (Only their outlines are shown in the image) between; four brackets 15FL, 15FR, 15RL and 15RR, which are arranged between the subframe 13 and the body 4; a yaw rate sensor 16, which is configured to detect the yaw rate Y of the vehicle 1; a vehicle speed sensor 17, which is configured to detect the vehicle speed V; and a controller 18, which is configured to control the four brackets 15FL, 15FR, 15RL and 15RR based on the yaw rate Y and the vehicle speed V.

[0032] <Subframe 13>

[0033] refer to Figure 1 and Figure 2 The subframe 13 of the shock absorber 11 is located below the front of the vehicle body 4. In the plan view, the subframe 13 has a generally rectangular outline. The subframe 13 supports the on-board component 21. The on-board component 21 includes, for example, a drive source (such as an internal combustion engine or an electric motor) for driving the vehicle 1. Furthermore, the on-board component 21 may include a generator, differential gear, fuel tank, transmission, etc. Figure 1 Vehicle-mounted component 21 is omitted from the diagrams other than those shown.

[0034] refer to Figure 2 The vibration of the front wheel 2 based on the road surface input Z is transmitted to the subframe 13 via the left and right arms 3. More specifically, the vibration of the front wheel 2 based on the road surface input Z is input to the vibration input point B of the subframe 13 via the left and right arms 3. For example, the vibration input point B of the subframe 13 is the point where the subframe 13 is connected to the left and right arms 3.

[0035] <Left and right suspension 14>

[0036] The left and right suspensions 14 of the damping device 11 each include a spring and a shock absorber (neither shown). In this embodiment, the left and right suspensions 14 are respectively arranged between the left and right arms 3 and the vehicle body 4. In another embodiment, the left and right suspensions 14 may be respectively arranged between the left and right front wheels 2 and the vehicle body 4. Except... Figure 1 and Figure 2 The left and right suspensions 14 are omitted from the diagrams other than those shown.

[0037] <Four brackets: 15FL, 15FR, 15RL, 15RR>

[0038] refer to Figure 1 The four supports 15FL, 15FR, 15RL, and 15RR of the vibration damping device 11 are respectively arranged at the left front corner, right front corner, left rear corner, and right rear corner of the sub-frame 13. The front supports 15FL and 15FR and the rear supports 15RL and 15RR are arranged at certain intervals in the front-rear direction. In the following text, unless there is no need to distinguish them, these four supports 15FL, 15FR, 15RL, and 15RR will be simply referred to as "support 15".

[0039] refer to Figure 3 Each support 15 is composed of a variable stiffness support, the stiffness of which can be changed. Support 15 includes: an inner tube 23; an excitation coil 24; a support rubber component 25; an outer tube 26; upper and lower cores 27; and upper and lower magnetic media 28. In the following description of support 15, "radial outer" and "radial inner" refer to the outer and inner sides in the radial direction of an axis A extending vertically around the center of support 15.

[0040] The inner tube 23 of the bracket 15 is made of magnetic material. The inner tube 23 has a cylindrical shape around axis A. The inner tube 23 is fixed to the lower surface of the vehicle body 4 by means of fastening member 31 including bolt 31A and nut 31B. A notch 32 is provided on the outer peripheral surface of the inner tube 23.

[0041] The excitation coil 24 of the support 15 has a cylindrical shape around axis A. The excitation coil 24 is arranged radially outward of the inner tube 23. The radially inward portion of the excitation coil 24 fits into the recess 32 of the inner tube 23.

[0042] The support rubber component 25 of the bracket 15 has a cylindrical shape around axis A. The support rubber component 25 is arranged radially outside the inner tube 23 and the excitation coil 24. The vertical length of the support rubber component 25 matches the vertical length of the excitation coil 24.

[0043] The outer tube 26 of the bracket 15 is made of a magnetic material. The outer tube 26 is cylindrical in shape around the axis A. The outer tube 26 is arranged radially outward of the inner tube 23, the excitation coil 24, and the bracket rubber member 25. The upper and lower lengths of the outer tube 26 are greater than those of the excitation coil 24 and the bracket rubber member 25. The outer tube 26 is fitted in a fitting hole 13A provided in the sub-frame 13, and is thus fixed to the sub-frame 13.

[0044] Each core 27 of the bracket 15 includes a tubular portion 34 that is cylindrical in shape around the axis A, and a ring-shaped flange portion 35 that extends radially outward from one vertical end of the tubular portion 34 (the end away from the excitation coil 24). The tubular portion 34 is arranged radially outward of the inner tube 23. The tubular portion 34 is arranged on one vertical side of the radially outer portion of the excitation coil 24. The flange portion 35 is arranged on one vertical side of the bracket rubber member 25 and the outer tube 26.

[0045] Each magnetic medium 28 of the bracket 15 is composed of a magneto-rheological elastomer (MRE). In another embodiment, the magnetic medium 28 can be composed of a magneto-rheological fluid (MRF) or a magneto-rheological compound (MRC). The magnetic medium 28 is arranged within a space defined by the bracket rubber member 25, the outer tube 26, and the respective core 27.

[0046] <Yaw rate sensor 16>

[0047] Reference Figure 1 For example, the yaw rate sensor 16 of the damping device 11 is arranged near the center of gravity of the vehicle body 4. The yaw rate sensor 16 detects the yaw rate Y (the angular rate around the vertical axis) of the vehicle body 4 and outputs the detected yaw rate Y to the controller 18.

[0048] <Vehicle speed sensor 17>

[0049] The vehicle speed sensor 17 of the damping device 11 is composed of, for example, a wheel speed sensor provided in the wheels (the front wheels 2 and the rear wheels 5). The vehicle speed sensor 17 detects the vehicle speed V and outputs the detected vehicle speed V to the controller 18.

[0050] <Controller 18>

[0051] The controller 18 of the damping device 11 is composed of an electronic control unit (ECU) including an arithmetic processing unit (a processor such as a CPU and an MPU) and a storage device (a memory such as a ROM and a RAM). The controller 18 can be composed of one hardware or can be composed of a unit of a plurality of hardware members.

[0052] Reference Figure 4 The controller 18 is to control the excitation current I of each bracket 15 (the excitation current I of the bracket 15FL, the excitation current I of the bracket 15FR, the excitation current I of the bracket 15RL, and the excitation current I of the bracket 15RR). FL, the excitation current I of the support 15FR FR , the excitation current I of the support 15RL RL , and the excitation current I of the support 15RR RR ). The controller 18 includes, as functional components, a reference current value calculating unit 41, a target elastic center setting unit 42, and a current value correcting unit 43.

[0053] <Reference current value calculating unit 41>

[0054] The reference current value calculating unit 41 of the controller 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, Figure 4 The straight lines vl, v2, and v3 in FIG. 7 respectively indicate the relationship between the yaw rate Y and the reference current value Ir when the vehicle speed V is vl, v2, and v3 (vl > v2 > v3). 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.

[0055] The reference current value calculating unit 41 calculates the reference current value Ir by referring to the reference current value map Mr based on the yaw rate Y and the vehicle speed V. The reference current value calculating unit 41 outputs the calculated reference current value Ir to the current value correcting unit 43.

[0056] <Target elastic center setting unit 42>

[0057] The target elastic center setting unit 42 of the controller 18 sets the target elastic center Et (target rotation center) of the subframe 13. The target elastic center setting unit 42 sets the correction coefficient C (correction coefficient C FL of the support 15FL, the correction coefficient C FR of the support 15FR, the correction coefficient C RL of the support 15RL, and the correction coefficient C RR of the support 15RR) of each support 15 based on the set target elastic center Et. The setting method of the target elastic center Et and the calculation method of the correction coefficient C of each support 15 will be described later. The target elastic center setting unit 42 outputs the calculated correction coefficient C of each support 15 to the current value correcting unit 43.

[0058] <Current value correcting unit 43>

[0059] The current value correction unit 43 of the controller 18 individually calculates the exciting current I supplied to the exciting coil 24 of each of the brackets 15 based on the reference current value Ir output from the reference current value calculation unit 41 and the correction coefficient C of each of the brackets 15 output from the target elastic center setting unit 42. More specifically, the current value correction unit 43 individually calculates the exciting current I supplied to the exciting coil 24 of each of the brackets 15 by correcting the reference current value Ir based on the correction coefficient C of each of the brackets 15.

[0060] For example, the current value correction unit 43 calculates the exciting current I of the bracket 15FL by multiplying the reference current value Ir by the correction coefficient C of the bracket 15FL FL . Similarly, the current value correction unit 43 calculates the exciting currents I FL , I FR , and I RL of the brackets 15FR, 15RL, and 15RR by multiplying the reference current value Ir by the correction coefficients C RR , C FR , and C RL of the brackets 15FR, 15RL, and 15RR, respectively. RR .

[0061] <Change in rigidity of the bracket 15>

[0062] Referring to Figure 5 , each of the magnetic mediums 28 of each of the brackets 15 is formed by mixing magnetic particles 46 (e.g., iron powder) into an elastomer 45 (e.g., silicone rubber). When a magnetic field (see dotted arrows in Figure 5 ) is applied from the outside to the magnetic medium 28, the magnetic particles 46 align like a chain in the direction of the magnetic field, thereby preventing the elastomer 45 from moving in a direction perpendicular to the direction of the magnetic field. Thus, the viscosity of the magnetic medium 28 in the direction perpendicular to the direction of the magnetic field increases, and thus the rigidity of the bracket 15 in the direction perpendicular to the direction of the magnetic field increases.

[0063] Referring to Figure 3 , when the exciting current I is supplied to the exciting coil 24 of each of the brackets 15, the exciting coil 24 generates a magnetic field (see dotted arrows in Figure 3 ). Thus, in the region R1 of Figure 3 , a magnetic field in the up-down direction is applied to each of the magnetic mediums 28. Thus, the viscosity of the magnetic medium 28 in the horizontal direction (the front-back direction and the lateral direction) increases, and thus the rigidity of the bracket 15 in the horizontal direction increases. Further, in the region R2 of Figure 3 , a magnetic field in the horizontal direction (more precisely, a radial direction about the axis A) is applied to the magnetic medium 28. Thus, the viscosity of the magnetic medium 28 in the up-down direction increases, and thus the rigidity of the bracket 15 in the up-down direction increases.

[0064] <Setting method 1 of target elastic center Et and calculation method 1 of correction coefficient C of each support 15>

[0065] Figure 6A The state in which the front-and-rear position of each vibration input point B of the sub frame 13 and the front-and-rear position of the actual elastic center Ea (actual rotation center: hereinafter referred to as "actual elastic center Ea") are deviated from each other is shown. In this state, when the vibration of the front wheel 2 based on the road surface input Z is input to the sub frame 13 via the vibration input point B, the pitch moment Mp corresponding to the distance Q in the front-and-rear direction between the actual elastic center Ea and the vibration input point B is generated at the sub frame 13. Therefore, the vibration of the sub frame 13 can be amplified.

[0066] In contrast, Figure 6B The state in which the front-and-rear position of each vibration input point B of the sub frame 13 matches the front-and-rear position of the actual elastic center Ea is shown. In this state, even if the vibration of the front wheel 2 is input to the sub frame 13 via the vibration input point B, the pitch moment Mp described above is unlikely to be generated at the sub frame 13, and the translational motion W (vertical motion) is likely to be mainly generated at the sub frame 13. Therefore, it is possible to prevent the vibration of the sub frame 13 from being amplified, and to improve the steering stability of the vehicle 1.

[0067] Therefore, as Figure 6C shown in FIG. 1, the target elastic center setting unit 42 sets the target elastic center Et so that the front-and-rear position of the vibration input point B matches the front-and-rear position of the target elastic center Et. In addition, the target elastic center setting unit 42 calculates the correction coefficient C of each support 15 based on the set target elastic center Et. For example, the target elastic center setting unit 42 calculates the correction coefficient C of the front supports 15FL, 15FR (front side supports: the example of the first supports) by the following formula (1) FL , C FR , and calculates the correction coefficient C of the rear supports 15RL, 15RR (rear side supports: the example of the second supports) by the following formula (2) RL , C RR . "Da" in the following formulas (1) and (2) indicates the distance in the front-and-rear direction between the target elastic center Et and the front supports 15FL, 15FR (the example of the first distance: hereinafter referred to as "distance Da"). "Db" in the following formulas (1) and (2) indicates the distance in the front-and-rear direction between the target elastic center Et and the rear supports 15RL, 15RR (the example of the second distance: hereinafter referred to as "distance Db").

[0068] C FL = C FR = Db / (Da+Db)...(1)

[0069] C RL = C RR = Da / (Da+Db)...(2)

[0070] From the above equation (1), it is clear that the target elastic center setting unit 42 calculates the correction coefficients C FL , C FR of the front brackets 15FL, 15FR by dividing the distance Db by the sum of the distances Da and Db. Further, from the above equation (2), it is clear that the target elastic center setting unit 42 calculates the correction coefficients C RL , C RR of the rear brackets 15RL, 15RR by dividing the distance Da by the sum of the distances Da and Db.

[0071] For example, when the target elastic center Et moves rearward from the position in Figure 6C , the distance Da in the above equation (1) increases, and the distance Db in the above equation (2) decreases. Therefore, the correction coefficients C FL , C FR of the front brackets 15FL, 15FR decrease, and the correction coefficients C RL , C RR of the rear brackets 15RL, 15RR increase. Therefore, the exciting currents I FL , I FR of the front brackets 15FL, 15FR decrease, and the exciting currents I RL , I RR of the rear brackets 15RL, 15RR increase. Therefore, the rigidity of the front brackets 15FL, 15FR in the up-and-down direction decreases, and the rigidity of the rear brackets 15RL, 15RR in the up-and-down direction increases. Therefore, the actual elastic center Ea moves rearward. In contrast, when the target elastic center Et moves forward from the position in Figure 6C , the actual elastic center Ea moves forward due to the effect opposite to the above case. Therefore, by determining the correction coefficients C of each bracket 15 in accordance with the above equations (1) and (2), it is possible to match the actual elastic center Ea with the target elastic center Et.

[0072] <Setting method 2 of target elastic center Et and calculation method 2 of correction coefficients C of each bracket 15>

[0073] As Figure 7AAs shown, when the actual elastic center Ea of the subframe 13 is positioned further forward than the vibration input point B, a yaw moment is generated at the subframe 13 in a direction matching the turning direction of the vehicle body 4 when the vehicle body 4 turns, thus improving the turning performance of the vehicle body 4. Therefore, it is preferable that the actual elastic center Ea of the subframe 13 is positioned further forward than the vibration input point B when the vehicle 1 is traveling at low speed, thereby improving the turning performance of the vehicle body 4.

[0074] In comparison, such as Figure 7B As shown, when the actual elastic center Ea of the subframe 13 is positioned further back than the vibration input point B, a yaw moment is generated at the subframe 13 in the opposite direction to the turning direction of the vehicle body 4 when the vehicle body 4 turns, thereby improving the stability of the vehicle body 4. Therefore, it is preferable that when the vehicle 1 is traveling at high speed, the actual elastic center Ea of the subframe 13 is positioned further back than the vibration input point B, thereby improving the stability of the vehicle body 4.

[0075] Therefore, when the vehicle speed V output from the vehicle speed sensor 17 is equal to or greater than a predetermined speed threshold (when the vehicle 1 is traveling at high speed), the target elastic center setting unit 42 sets the target elastic center Et of the sub-frame 13 further back than the vibration input point B. Conversely, when the vehicle speed V output from the vehicle speed sensor 17 is less than the speed threshold (when the vehicle 1 is traveling at low speed), the target elastic center setting unit 42 sets the target elastic center Et of the sub-frame 13 further forward than the vibration input point B. In another embodiment, when the vehicle speed V is equal to or greater than the speed threshold, the target elastic center setting unit 42 can set the target elastic center Et of the sub-frame 13 further forward than the vibration input point B, and when the vehicle speed V is less than the speed threshold, it sets the target elastic center Et of the sub-frame 13 further back than the vibration input point B. In this embodiment, the target elastic center setting unit 42 changes the target elastic center Et in the longitudinal direction in two stages. In another embodiment, the target elastic center setting unit 42 can change the target elastic center Et in the longitudinal direction in three or more stages.

[0076] The target elastic center setting unit 42 sets the correction coefficient C for each support 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 supports 15FL and 15FR (an embodiment of the first support) using the following formula (3). FL C FR The correction coefficient C of the posterior stents 15RL and 15RR (the embodiment of the second stent) is calculated using the following formula (4). RL C RRIn formulas (3) and (4) below, “Dc” represents the distance in the front-rear direction between the target elastic center Et and the front supports 15FL and 15FR (an embodiment of the first distance, hereinafter referred to as “distance Dc”). In formulas (3) and (4) below, “Dd” represents the distance in the front-rear direction between the target elastic center Et and the rear supports 15RL and 15RR (an embodiment of the second distance, hereinafter referred to as “distance Dd”).

[0077] C FL =C FR =Dd / (Dc+Dd)...(3)

[0078] C RL =C RR =Dc / (Dc+Dd)...(4)

[0079] From the above formula (3), it can be understood that the target elastic center setting unit 42 calculates the correction coefficient C of the front support 15FL and 15FR by dividing the distance Dd by the sum of the distances Dc and Dd. FL C FR Furthermore, it can be understood from the above formula (4) that the target elastic center setting unit 42 calculates the correction coefficient C of the rear supports 15RL and 15RR by dividing the distance Dc by the sum of the distances Dc and Dd. RL C RR .

[0080] refer to Figure 7A When the target elastic center Et is set further forward than the vibration input point B, the distance Dd in formulas (3) and (4) above becomes larger than the distance Dc in formulas (3) and (4) above. Therefore, the correction coefficient C of the front brackets 15FL and 15FR is... FL C FR The correction factor C becomes greater than that of the rear bracket 15RL and 15RR. RL C RR Large. Therefore, the excitation current I of the front brackets 15FL and 15FR is large. FL I FR The excitation current I becomes greater than that of the rear support 15RL and 15RR. RL I RR Therefore, the front supports 15FL and 15FR have greater lateral stiffness than the rear supports 15RL and 15RR. Consequently, the actual elastic center Ea is positioned further forward than the vibration input point B. (Reference) Figure 7BWhen the target elastic center Et is set further rearward than the vibration input point B, the actual elastic center Ea is disposed further rearward than the vibration input point B due to the opposite effect. Therefore, by determining the correction coefficient C of each of the suspensions 15 according to the above Equations (3) and (4), the actual elastic center Ea can be matched with the target elastic center Et.

[0081] <Setting method 3 of target elastic center Et and calculation method 3 of correction coefficient C of each suspension 15>

[0082] The target elastic center setting unit 42 sets the target elastic center Et by the same method as the setting method 1 of the target elastic center Et. Alternatively, the target elastic center setting unit 42 can set the target elastic center Et by the same method as the setting method 2 of the target elastic center Et.

[0083] The target elastic center setting unit 42 calculates the correction coefficient C of each of the suspensions 15 based on the set target elastic center Et. More specifically, the target elastic center setting unit 42 calculates the target spring ratio of the front suspensions 15FL, 15FR and the rear suspensions 15RL, 15RR from the target elastic center Et using computer simulation or the like. In addition, the target elastic center setting unit 42 sets the correction coefficient C of each of the suspensions 15 based on the calculated target spring ratio.

[0084] For example, in the case where the target spring ratio of the front suspensions 15FL, 15FR and the rear suspensions 15RL, 15RR is 1:X, the target elastic center setting unit 42 sets the correction coefficient C of the front suspensions 15FL, 15FR by the following Equation (5) FL , FR and sets the correction coefficient C of the rear suspensions 15RL, 15RR by the following Equation (6) RL , RR .

[0085] FL FR = 1...(5)

[0086] RL RR = X...(6)

[0087] <Effects of first embodiment>

[0088] In the first embodiment, the controller 18 increases the reference current value Ir as the yaw rate Y increases (see FIG. 6). Therefore, the actual elastic center Ea can be matched with the target elastic center Et. Figure 4 ​​​​The reference current value Ir is mapped to the stiffness of each support 15 by the reference current value mapping Mr. Therefore, when the yaw rate Y increases as the vehicle 1 turns, the reference current value Ir increases, and the excitation current I supplied to each support 15 also increases. Therefore, the stiffness of the support 15 increases, and thus the steering stability when the vehicle 1 turns can be improved.

[0089] Incidentally, if the stiffness of the plurality of supports 15 increases simultaneously and uniformly, the vibration of the sub-frame 13 can be transmitted to the vehicle body 4 via the plurality of supports 15. In light of this, the controller 18 individually calculates the excitation current I supplied to each support 15. Therefore, it is possible to prevent the stiffness of the plurality of supports 15 from increasing simultaneously and uniformly. Therefore, it is possible to prevent the vibration of the sub-frame 13 from being transmitted to the vehicle body 4 via the plurality of supports 15, and thus the in-vehicle damping performance can be improved.

[0090] Further, the controller 18 sets a target elastic center Et of the sub-frame 13, and matches the actual elastic center Ea of the sub-frame 13 with the target elastic center Et. Therefore, it is possible to freely adjust the moment (e.g., the pitch moment and the yaw moment) generated at the sub-frame 13.

[0091] (Second Embodiment)

[0092] Next, a second embodiment of the present application will be described with reference to Figure 8 and Figure 9 will be described. The explanation overlapping with the first embodiment of the present application will be appropriately omitted.

[0093] <Vehicle Damping Device 51 for Vehicle>

[0094] Figure 8 is a functional block diagram showing a vehicle damping device 51 for vehicle (hereinafter abbreviated as "vehicle damping device 51") according to the second embodiment. In the vehicle damping device 51, the components other than the four supports 53FL, 53FR, 53RL, and 53RR and the controller 54 are the same as those of the first embodiment. Therefore, the description of these same components will be omitted.

[0095] <Four Supports 53FL, 53FR, 53RL, and 53RR>

[0096] Like the four supports 15FL, 15FR, 15RL, and 15RR of the first embodiment, the four supports 53FL, 53FR, 53RL, and 53RR of the vehicle damping device 51 are arranged at the left front corner, the right front corner, the left rear corner, and the right rear corner of the sub-frame 13, respectively. Hereinafter, the four supports 53FL, 53FR, 53RL, and 53RR are simply referred to as "supports 53" when it is not necessary to distinguish.

[0097] Each of the yokes 53 has three exciting coils 56X, 56Y, and 56Z. When current is supplied to the exciting coil 56X, the exciting coil 56X generates a magnetic field in a direction perpendicular to the X-axis direction (the front-rear direction), thereby increasing the rigidity of the yoke 53 in the X-axis direction. When current is supplied to the exciting coil 56Y, the exciting coil 56Y generates a magnetic field in a direction perpendicular to the Y-axis direction (the lateral direction), thereby increasing the rigidity of the yoke 53 in the Y-axis direction. When current is supplied to the exciting coil 56Z, the exciting coil 56Z generates a magnetic field in a direction perpendicular to the Z-axis direction (the up-down direction), thereby increasing the rigidity of the yoke 53 in the Z-axis direction. Thus, the yoke 53 is configured to independently change the rigidity in the three axial directions.

[0098] <Controller 54>

[0099] The controller 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. 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. Thus, the description thereof will be omitted.

[0100] <Target elastic center setting unit 59>

[0101] With reference to Figure 9 , the target elastic center setting unit 59 of the controller 54 stores a correction coefficient table T. The correction coefficient table T defines the correction coefficient C of each of the yokes 53 in each of the axial directions in accordance with the vehicle speed V. For example, the correction coefficient table T defines the correction coefficient C FLX of the yoke 53FL in the X-axis direction, the correction coefficient C FLY of the yoke 53FL in the Y-axis direction, and the correction coefficient C FLZ of the yoke 53FL in the Z-axis direction. Likewise, the correction coefficient table T defines the correction coefficients C of the yokes 53FR, 53RL, and 53RR in the X-axis, Y-axis, and Z-axis directions.

[0102] The target elastic center setting unit 59 calculates the correction coefficient C of each of the yokes 53 in each of the axial directions with reference 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 of each of the yokes 53 in each of the axial directions to the current value correction unit 60.

[0103] <Current value correction unit 60>

[0104] The current value correction unit 60 of the controller 54 individually calculates the exciting current I of each of the yokes 53 in each of the axial directions by correcting the reference current value Ir based on the correction coefficient C of the yoke 53 in each of the axial directions. For example, the current value correction unit 60 calculates the exciting current I of the yoke 53FL in the X-axis direction by multiplying the reference current value Ir by the correction coefficient C FLX, C FLY and C FLZ to calculate the excitation current I FLX , I FLY and I FLZ of the yoke 53 FL in each axial direction. The current value correction unit 60 outputs the calculated excitation current I of the yoke 53 in each axial direction to the excitation coils 56X, 56Y and 56Z of the yoke 53. Thus, the stiffness of the yoke 53 in each axial direction is independently varied.

[0105] <Effects of the second embodiment>

[0106] As described above, in the second embodiment, the controller 54 independently varies the stiffness of each yoke 53 in each axial direction. Thus, the pitch moment, roll moment and yaw moment generated at the sub-frame 13 can be simultaneously suppressed. Therefore, the current required to ensure the steering stability can be reduced, and an increase in vibration and noise can be suppressed.

[0107] Further, the correction coefficient table T defines the correction coefficient C of each yoke 53 in each axial direction in accordance with the vehicle speed V. Thus, the correction coefficient C of the yoke 53 in each axial direction can be easily set in accordance with the vehicle speed V.

[0108] <Variations of the second embodiment>

[0109] In the second embodiment, each yoke 53 is configured to independently vary the stiffness thereof in three axial directions. In the case where the stiffness of the yoke 53 in the three axial directions is dependent on each other (refer to the first embodiment), the controller 54 can determine the priority of the three axes in advance, and output the excitation current I so that the stiffness of the yoke 53 in the axial direction having the highest priority conforms to the target value.

[0110] The specific embodiments of the application have been described hereinbefore, but the application should not be limited to the foregoing embodiments, and various modifications and changes can be made within the scope of the application.

Claims

1. A damping device for a vehicle, the damping device comprising: a sub-frame to which vibrations of a wheel are transmitted; a plurality of supports arranged between the sub-frame and a vehicle body and configured to vary a rigidity of each support in a prescribed direction in accordance with an excitation current supplied thereto; and a controller configured to control the excitation current supplied to each support, wherein the controller is configured to: set a target center of elasticity of the sub-frame; and individually calculate the excitation current supplied to each support so that an actual center of elasticity of the sub-frame matches the target center of elasticity.

2. The damping device according to claim 1, further comprising: a yaw rate sensor configured to detect a yaw rate of the vehicle body; and a vehicle speed sensor configured to detect a vehicle speed, wherein the controller is configured to: calculate a reference current value based on the yaw rate and the vehicle speed; calculate a correction coefficient of each support based on the target center of elasticity; and individually calculate the excitation current supplied to each support by correcting the reference current value based on the correction coefficient of each support. the plurality of supports include a first support and a second support arranged at an interval in a vertical direction perpendicular to the prescribed direction, and in a case where a distance in the vertical direction between the target center of elasticity and the first support is defined as a first distance and a distance in the vertical direction between the target center of elasticity and the second support is defined as a second distance, the controller is configured to: calculate the correction coefficient of the first support by dividing the second distance by a sum of the first distance and the second distance; and 3. The vibration damping device according to claim 2, wherein calculate the correction coefficient of the second support by dividing the first distance by the sum of the first distance and the second distance. the controller is configured to: store a correction coefficient table defining the correction coefficient of each support; and calculate the correction coefficient of each support by referring to the correction coefficient table.

4. The vibration damping device according to claim 2, wherein the plurality of supports are configured to vary a rigidity of each support in a vertical direction in accordance with the excitation current supplied thereto, the sub-frame has a vibration input point into which vibrations of the wheel are input, and the controller is configured to set the target center of elasticity so that a front-rear position of the vibration input point matches a front-rear position of the target center of elasticity.

5. The vibration damping device according to any one of claims 1 to 4, wherein 6. The damping device according to any one of claims 1 to 4, further comprising a vehicle speed sensor configured to detect a vehicle speed, the plurality of supports are configured to vary a rigidity of each support in a lateral direction in accordance with the excitation current supplied thereto, and the controller is configured to change the target center of elasticity in a front-rear direction based on the vehicle speed. ​ wherein ​ ​

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