Electromagnetic damper

An electromagnetic damper includes a torque detection unit that detects a torsional torque of an output shaft of an electric motor or a torsional torque of a transmission shaft, which transmits an external vibration to the electric motor, and a control device that controls the electric motor. The control device controls the electric motor so as to cancel the torsional torque detected by the torque detection unit.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-022791, filed Feb. 9, 2015, entitled “Electromagnetic Damper.” The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to an electromagnetic damper that inputs an external vibration to an output shaft of an electric motor and generates a damping force with respect to the external vibration by using the electric motor.

2. Description of the Related Art

In Japanese Unexamined Patent Application Publication No. 2006-057668, the purpose thereof is to improve ride comfort of a vehicle, even with a shock absorber that generates a damping force by utilizing an electromagnetic force of a motor (paragraph [0007], abstract). A shock absorber D of Japanese Unexamined Patent Application Publication No. 2006-057668 is provided with a motion conversion mechanism T for converting linear relative motion between a vehicle body B and an axle into rotary motion and a motor M to which rotary motion converted by the motion conversion mechanism T is transmitted. In the shock absorber D, the motor M is fixed to a vehicle body B side, the motion conversion mechanism T is interposed between the vehicle body B and the axle, a sprung side connection mass is reduced, and a force for transmitting input of a vibration from an axle side to the vehicle body B side is reduced. In doing so, ride comfort of the vehicle is improved (Abstract).

The motor M is connected to a control device (not shown) and an external power source (not shown) in such a manner that the motor M is capable of controlling rotary torque of a rotor1, and the motor M is adjusted so as to obtain a desired damping force. Furthermore, by actively driving the motor M, the shock absorber D is made to function not only as a shock absorber but also as an actuator (paragraph [0016]).

In the shock absorber D (electromagnetic damper) of Japanese Unexamined Patent Application Publication No. 2006-057668, an inertia force (or an inertia moment) is generated when the motion conversion mechanism T converts linear relative motion between the vehicle body B and the axle into rotary motion and when the rotor1of the motor M generates rotary torque. With such a configuration in which the inertia force is relatively large, if acceleration of input (for example, input from a road surface) to the shock absorber D is large, the inertia force suppresses changes in stroke of the shock absorber D. Consequently, the vibration damping function of the shock absorber D may not be fully exhibited (for example, in a case where the shock absorber D is used in a suspension device of a vehicle, ride comfort of the vehicle may be reduced).

SUMMARY

The present application describes an electromagnetic damper capable of improving a vibration damping characteristic.

An electromagnetic damper according to an aspect of an embodiment inputs an external vibration to an output shaft of an electric motor, generates, in the electric motor, a damping force with respect to the external vibration, and includes: a torque detection unit that detects a torsional torque of the output shaft of the electric motor or a torsional torque of a transmission member such as a transmission shaft that transmits the external vibration to the electric motor; and a control device that controls the electric motor so as to cancel the torsional torque detected by the torque detection unit.

According to the aspect of the embodiment, the electric motor is controlled so as to cancel a torsional torque of the output shaft of the electric motor or a torsional torque of the transmission member that transmits an external vibration to the electric motor. The torsional torque contains a disturbance factor such as an inertia force. Therefore, the influence of the disturbance factor is reduced by transmitting the power of the electric motor to the output shaft or the transmission member while suppressing the torsional torque, and thereby a target value of the power of the electric motor can be realized with greater certainty. As a result, a vibration damping characteristic of the electromagnetic damper (for example, in a case where the electromagnetic damper is installed on a suspension device of a vehicle, ride comfort of the vehicle) can be improved.

Furthermore, with a configuration in which the torque detection unit detects a torsional torque of the output shaft of the electric motor, if the ratio of the inertia of the electric motor (rotor, etc.) to the inertia of the entire electromagnetic damper is high, it is possible to easily cancel the inertia of the electric motor.

The electromagnetic damper may include a threaded shaft as the transmission member and a nut screwed onto the threaded shaft, and may convert linear motion of the nut with respect to the threaded shaft into rotary motion of the threaded shaft and transmit the rotary motion of the threaded shaft to the output shaft of the electric motor.

The electromagnetic damper may include a rack gear formed on the side of the transmission member and a pinion gear formed on the side of the output shaft of the electric motor, and may convert linear motion of the transmission member into rotary motion by using the rack gear and the pinion gear and transmit rotary motion of the pinion gear to the output shaft of the electric motor.

The electromagnetic damper may include a rotary arm that rotates around the output shaft of the electric motor, and the torque detection unit may detect a torsional torque of the output shaft of the electric motor or a torsional torque of the rotary arm.

The electromagnetic damper may be installed in a suspension device of a vehicle. In this case, the control device may reduce a degree of canceling the torsional torque as a steering angle or a steering angle speed of a steering increases. Consequently, if the vehicle travels on a curved road, for example, the damping force of the electromagnetic damper can be reduced while the influence of the inertia force is being relatively maintained. Therefore, the steering responsiveness or the stability of the operation can be improved, and in addition, ride comfort is improved.

The control device may reduce a degree of canceling the torsional torque as a vehicle speed of the vehicle increases. Consequently, a degree of canceling the torsional torque is reduced as the vehicle speed increases, and therefore, the stability of the vehicle in a high vehicle speed region can be ensured.

The control device may include a reference control amount calculation section (a reference control amount calculator) that calculates a reference control amount of the electric motor, a correction control amount calculation section (a correction control amount calculator) that calculates a correction control amount by correcting the reference control amount, and an electric motor control section (an electric motor controller) that controls the electric motor on the basis of the correction control amount. The correction control amount calculation section may calculate the correction control amount by reflecting a difference between the torsional torque and a torque corresponding to the reference control amount in the reference control amount. Consequently, a disturbance factor included in the torsional torque can be accurately excluded.

The torque detection unit may be a magnetostrictive torque sensor, for example. Consequently, a torsional torque of the output shaft of the electric motor or a torsional torque of the transmission member can be accurately detected.

According to the present application, a vibration damping characteristic of the electromagnetic damper can be improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A. One Embodiment

A1. Configuration of Vehicle10

A1-1. Overall Structure of Vehicle10

FIG. 1is a simplified diagram illustrating a part of a vehicle10in which an electromagnetic damper12(hereinafter also referred to as “damper12”) according to one embodiment is mounted. The damper12of the embodiment constitutes a part of a suspension device of the vehicle10. The suspension device includes a spring (for example, a coil spring) in addition to the damper12. Furthermore, the vehicle10is provided with sensors14and a battery16. Note that the dampers12are installed on the front wheels (left front wheel and right front wheel) and the rear wheels (left rear wheel and right rear wheel). Alternatively, the damper12may be installed on the front wheels only or the rear wheels only.

The sensors14include a torque sensor20, a vehicle speed sensor22, a steering angle sensor24, and a current sensor26. The torque sensor20detects a torsional torque Td (hereinafter also referred to as “torque Td” or “detected torque Td”) applied to a part (an output shaft60of a motor56to be described later) of the damper12.

As the torque sensor20of the embodiment, a magnetostrictive torque sensor, for example, may be used. Note that although two torque sensors20are shown inFIG. 1, those torque sensors are identical and are illustrated in order to indicate that the torque sensor20is included in the sensors14and in order to indicate the position of the torque sensor20in the damper12(especially the damper body30).

The vehicle speed sensor22detects vehicle speed V[km/h] of the vehicle10. The steering angle sensor24detects steering angle θst[°] of a steering28. The current sensor26detects input/output current [A](hereinafter referred to as “motor current Imot”) of the motor56of the damper12. Note that the motor56of the embodiment is a three-phase alternating current (AC) motor and therefore, the current sensor26detects currents of multiple phases (U-phase, V-phase, and W-phase) and calculates motor current Imot as a d-axis current (a torque component) obtained by dq-converting these currents.

The battery16is a lead battery, for example, but may be another type of battery or power storage device (for example, a lithium ion battery, a generator, a fuel cell, or a capacitor).

A1-2-1. Overview of Damper12

As illustrated inFIG. 1, the damper12has a damper body30, an inverter32, and an electronic control unit34(hereinafter referred to as “ECU34”).

A1-2-2-1. Overview of Damper Body30

As illustrated inFIG. 1, the damper body30is provided with a connection section40, an inner tube42, and a nut44as members on the side of a wheel (not shown). Furthermore, the damper body30is provided with an outer tube50, a threaded shaft52, a bearing54, and a motor56as members on the side of a vehicle body58.

The connection section40is fixed to a knuckle (not shown) of a suspension device, thereby being connected to a wheel. When an external vibration is input to the connection section40from a wheel side and the connection section40is applied with, for example, an upward thrust (a so-called damping direction) inFIG. 1, the inner tube42and the nut44move upward relative to the outer tube50, thereby rotating the threaded shaft52. In doing so, vibration of the spring of the suspension device can be damped by generating a reaction force from the motor56with respect to the threaded shaft52.

As a basic configuration of the damper body30, an existing feature (see, for example, Japanese Unexamined Patent Application Publication No. 2006-057668, the entire contents of which are incorporated herein by reference) may be used.

The motor56of the embodiment is of a three-phase AC brushless type, but is not limited thereto. The output shaft60of the motor56is connected to or fixed to the threaded shaft52via a coupling62. The motor56generates power (reaction force) in the threaded shaft52on the basis of the electric power supplied from the battery16in response to an instruction from the ECU34. In addition, the motor56may output a generated electric power to the battery16by performing electric power generation (regeneration) on the basis of power input to the threaded shaft52from the wheel side.

The inverter32has a three-phase full-bridge configuration, performs DC-AC conversion to convert direct current (DC) into three-phase alternating current, and supplies the three-phase alternating current to the motor56. The inverter32may supply to the battery16direct current obtained by AC-DC conversion associated with regeneration operation.

As illustrated inFIG. 1, the ECU34has an input/output section70, an arithmetic section72, and a storage section74. The input/output section70inputs/outputs signals to/from the sensors14, the inverter32, etc.

The arithmetic section72controls each section of the damper12and is provided with a reference control amount calculation section80, a correction control amount calculation section82, and a motor control section84. In the embodiment, the reference control amount calculation section80, the correction control amount calculation section82, and the motor control section84are realized by executing control programs stored in the storage section74.

The reference control amount calculation section80calculates a reference control amount Uref of the motor56. The reference control amount Uref is a reference value (a value before correction) of a variable amount for controlling the motor56and is a target reference force Fref_tar[N] in the embodiment. The target reference force Fref_tar is a reference value of a force generated in the motor56.

The correction control amount calculation section82calculates a correction control amount Ucor by correcting the reference control amount Uref. The correction control amount Ucor is obtained by correcting the reference control amount Uref to cancel a disturbance factor such as inertia, and is a target motor current Imot_tar in the embodiment. The motor control section84controls the motor56via the inverter32on the basis of the correction control amount Ucor.

The storage section74stores data and various programs such as a control program used in the arithmetic section72.

A2. Control in the Embodiment

A2-1. Overall Flow

FIG. 2is a flowchart illustrating overall flow of control of the ECU34of the embodiment. In step S1, the reference control amount calculation section80of the ECU34calculates a reference control amount Uref. In step S2, the correction control amount calculation section82of the ECU34calculates a correction control amount Ucor. In step S3, the motor control section84of the ECU34operates the inverter32on the basis of the correction control amount Ucor to control the motor56.

A2-2. Calculation of Reference Control Amount Uref

As described above, the reference control amount Uref is a reference value of a variable amount for controlling the motor56and is a target reference force Fref_tar[N] in the embodiment. The ECU34calculates a reference control amount Uref by using, for example, the same method as in Japanese Unexamined Patent Application Publication No. 2004-237824 or Japanese Unexamined Patent Application Publication No. 2009-078761, the entire contents of which are incorporated herein by reference.

A2-3. Calculation of Correction Control Amount Ucor

A2-3-1. Basic Concept

The correction control amount Ucor of the embodiment is used to cancel a disturbance factor such as inertia of the damper body30. In the embodiment, the inertia of a rotor (hereinafter also referred to as “motor rotor”) (not shown) of the motor56is relatively large in the damper body30. Consequently, by canceling the inertia of the motor rotor, it is possible to easily bring the output of the motor56close to the reference control amount Uref (target reference force Fref_tar).

A2-3-2. Specific Processing

FIG. 3is a block diagram illustrating a configuration for controlling the motor56of the embodiment, focusing on the calculation of a correction control amount Ucor. As illustrated inFIG. 3, the correction control amount calculation section82of the ECU34has a target motor current calculation section100, a vehicle speed reflection correction section102, and a steering angle reflection correction section104.

A2-3-2-2. Target Motor Current Calculation Section100

The target motor current calculation section100(hereinafter also referred to as “calculation section100”) calculates a target motor current Imot_tar as a correction control amount Ucor. As illustrated inFIG. 3, the calculation section100has a first current converter110, a torque converter112, a first subtracter114, a second current converter116, and a second subtracter118.

The first current converter110converts a target reference force Fref_tar[N] as a reference control amount Uref into a current value (target reference current Iref_tar)[A]. The torque converter112converts the target reference force Fref_tar into a torque value (target reference torque Tref_tar)[Nm].

The first subtracter114calculates a difference ΔT1between a second correction torque Tc2output from the steering angle reflection correction section104and a target reference torque Tref_tar output from the torque converter112. The second current converter116converts the difference ΔT1[Nm] calculated in the first subtracter114into a current value (F/B current Ifb)[A]. The second subtracter118calculates a difference, as a target motor current Imot_tar, between the target reference current Iref_tar output from the first current converter110and the F/B current Ifb output from the second current converter116and outputs the target motor current Imot_tar to the motor control section84.

A2-3-2-3. Vehicle Speed Reflection Correction Section102

The vehicle speed reflection correction section102(hereinafter also referred to as “correction section102”) reflects a vehicle speed V in the detected torque Td detected by the torque sensor20. As illustrated inFIG. 3, the correction section102has a vehicle speed-first gain map120(hereinafter also referred to as “map120”), a first rate limit processing section122, and a vehicle speed reflection amplifier124(hereinafter also referred to as “first amplifier124”).

FIG. 4shows one example of the contents of the vehicle speed-first gain map120according to the embodiment. The map120stores a relationship between vehicle speed V and first gain G1and outputs a first gain G1in accordance with a vehicle speed V output from the vehicle speed sensor22.

The first gain G1is a gain for weighting a disturbance factor (especially inertia force) on the basis of the vehicle speed V. As illustrated inFIG. 4, when the vehicle speed V is between zero and V1, the first gain G1increases as the vehicle speed V increases. When the vehicle speed V is between V1and V2, the first gain G1is constant. When the vehicle speed V exceeds V2, the first gain G1decreases as the vehicle speed V increases. Note that the vehicle speed V1may be any value between 50 and 120 km/h, for example. Furthermore, the vehicle speed V2may be any value between 80 and 180 km/h, for example.

The first gain G1is used as a gain for the detected torque Td in the first amplifier124. Therefore, when the first gain G1increases, the detected torque Td is output to the first subtracter114while the detected torque Td is being kept close to the original value.

As the detected torque Td (to be precise, the second correction torque Tc2) output to the first subtracter114approaches the original value, the absolute value of the F/B current Ifb to be subtracted in the second subtracter118increases, and thereby the target motor current Imot_tar decreases. Meanwhile, as the detected torque Td (to be precise, the second correction torque Tc2) output to the first subtracter114becomes smaller than the original value, the absolute value of the F/B current Ifb to be subtracted in the second subtracter118decreases, and thereby the target motor current Imot_tar increases. Therefore, by using the first gain G1, a degree of feedback of the detected torque Td can be weakened as the vehicle speed V increases.

The first rate limit processing section122limits the absolute value of a difference between the previous value and the current value of the first gain G1output from the map120so as not to exceed a predetermined threshold and outputs the first gain G1to the vehicle speed reflection amplifier124.

The first amplifier124multiplies the detected torque Td output from the torque sensor20by the first gain G1output from the first rate limit processing section122to calculate a first correction torque Tc1and outputs the first correction torque Tc1to the steering angle reflection correction section104.

The steering angle reflection correction section104(hereinafter also referred to as “correction section104”) reflects steering angle speed Vθst in the first correction torque Tc1output from the vehicle speed reflection correction section102. The positions of the vehicle speed reflection correction section102and the steering angle reflection correction section104may be exchanged. As illustrated inFIG. 3, the correction section104has a steering angle speed calculator130, a steering angle speed-second gain map132(hereinafter also referred to as “map132”), a second rate limit processing section134, and a steering angle speed reflection amplifier136.

The steering angle speed calculator130(hereinafter also referred to as “calculator130”) calculates a steering angle speed Vθst[°/sec] as a time differential value of steering angle θst[° ].

FIG. 5shows one example of the contents of the steering angle speed-second gain map132according to the embodiment. The map132stores a relationship between steering angle speed Vθst and second gain G2and outputs a second gain G2in accordance with a steering angle speed Vθst output from the calculator130.

The second gain G2is a gain for weighting a disturbance factor (especially inertia force) on the basis of the steering angle θst or the steering angle speed Vθst. As illustrated inFIG. 5, when the steering angle speed Vθst is between zero and Vθ1, the second gain G2increases as the steering angle speed Vθst increases. When the steering angle speed Vθst exceeds Vθ1, the second gain G2is constant. The action of the second gain G2is the same as the action of the first gain G1. That is, by using the second gain G2, a degree of feedback of the detected torque Td can be weakened as the steering angle speed Vθst increases.

The second rate limit processing section134limits the absolute value of a difference between the previous value and the current value of the second gain G2output from the map132so as not to exceed a predetermined threshold and outputs the second gain G2to the steering angle speed reflection amplifier136. The steering angle speed reflection amplifier136multiplies the first correction torque Tc1output from the vehicle speed reflection correction section102by the second gain G2output from the second rate limit processing section134to calculate a second correction torque Tc2and outputs the second correction torque Tc2to the first subtracter114of the target motor current calculation section100.

A2-4. Control of Motor Control Section84

The motor control section84(hereinafter also referred to as “control section84”) controls the motor56via the inverter32on the basis of the correction control amount Ucor (target motor current Imot_tar) output from the correction control amount calculation section82. More specifically, the control section84controls the duty ratio of a switching element (not shown) of the inverter32so as to realize the target motor current Imot_tar. In doing so, the control section84uses the motor current Imot detected by the current sensor26.

A3. Effects of the Embodiment

According to the embodiment, the motor56(electric motor) is controlled so as to cancel the torsional torque Td of the output shaft60of the motor56(FIGS. 2 and 3). The torsional torque Td contains a disturbance factor such as an inertia force. Therefore, the influence of the disturbance factor is reduced by transmitting the power of the motor56to the output shaft60or the threaded shaft52(transmission shaft) while suppressing the torsional torque Td, and thereby the target value (target reference force Fref_tar) of the power of the motor56can be realized with greater certainty. As a result, a vibration damping characteristic of the electromagnetic damper12(for example, ride comfort of the vehicle10) can be improved.

Furthermore, with a configuration in which the torque sensor20(torque detection unit) detects a torsional torque Td of the output shaft60of the motor56, if the ratio of the inertia of the motor56(motor rotor, etc.) to the inertia of the entire electromagnetic damper12is high, it is possible to easily cancel the inertia of the motor56.

In the embodiment, the ECU34weakens a degree of feedback of the detected torque Td as the steering angle speed Vθst increases (FIGS. 3 and 5). In other words, the ECU34reduces a degree of canceling the torsional torque Td as the steering angle speed Vθst increases. Consequently, if the vehicle10travels on a curved road, for example, the damping force of the electromagnetic damper12can be reduced while the influence of the inertia force is being relatively maintained. Therefore, the steering responsiveness or the stability of the operation can be improved, and in addition, ride comfort is improved.

That is, the inertia force associated with the operation of the damper12is proportional to the sprung acceleration or the unsprung acceleration of the damper12, and therefore, the phase of the inertia force advances by 90 degrees with respect to the generation of the damping force which is proportional to the sprung or unsprung speed. In the embodiment, a degree of feedback of the torsional torque Td is weakened as the steering angle speed Vθst increases, and therefore, the torque of the motor56is kept relatively high and the ground load is increased transiently, and thereby it is possible to make the posture of the wheel difficult to change. Consequently, the phase delay of generation of a lateral force of the wheel is reduced and response to the steering angle θst can be made more quickly, and thereby the steering responsiveness or the stability of the operation can be improved.

In the embodiment, the ECU34weakens a degree of feedback of the torsional torque Td as the vehicle speed V increases (FIGS. 3 and 4). In other words, the ECU34reduces a degree of canceling the torsional torque Td as the vehicle speed V increases. Consequently, a degree of feedback of the torsional torque Td is weakened (or a degree of cancellation is reduced) as the vehicle speed V increases, and therefore, with the same action as the steering angel speed Vθst, the stability of the vehicle10in a high vehicle speed region can be ensured.

In the embodiment, the ECU34is provided with the reference control amount calculation section80, which calculates a target reference force Fref_tar as a reference control amount Uref of the motor56(electric motor), the correction control amount calculation section82, which calculates a target motor current Imot_tar as a correction control amount Ucor by correcting the target reference force Fref_tar, and the motor control section84(electric motor control section), which controls the motor56on the basis of the target motor current Imot_tar (FIGS. 1 and 3). The correction control amount calculation section82reflects a difference ΔT1between the torsional torque Td and the torque (target reference torque Tref_tar) corresponding to the target reference force Fref_tar in the target reference force Fref_tar to calculate the target motor current Imot_tar (FIGS. 2 and 3). Thereby a disturbance factor included in the torsional torque Td can be accurately excluded.

In the embodiment, a magnetostrictive torque sensor is used as the torque sensor20(torque detection unit) (FIG. 1). Thereby the torsional torque Td of the output shaft60of the motor56(electric motor) can be accurately detected.

The configuration of the electromagnetic damper is not limited to the embodiment, and various configurations may be adopted on the basis of the description in the specification. For example, the following configurations can be adopted.

B1. Application Target

In the embodiment, the example in which the electromagnetic damper12is applied to the vehicle10(especially the suspension device) is explained. However, the application of the damper12is not limited thereto from the viewpoint of, for example, controlling the motor56so as to cancel a torsional torque Td. For example, the electromagnetic damper12may be applied to another device (for example, a manufacturing device or an elevator) that requires a vibration damping performance.

In the embodiment, the damper body30having the configuration illustrated inFIG. 1is used (FIG. 1). However, the damper body30is not limited thereto from the viewpoint of, for example, controlling the motor56so as to cancel a torsional torque Td. For example, a configuration of electromagnetic hydraulic hybrid type, ball screw type, rack pinion type, direct type (linear motor), or the like may be used as long as the configuration uses an actuator that uses the motor56.

B2-1-1. First Variation

FIG. 6is a simplified diagram illustrating a part of a vehicle10A in which an electromagnetic damper12a(hereinafter also referred to as “damper12a”) according to a first variation is mounted. The same components as the embodiment (FIG. 1) are denoted by the same reference signs, and explanations thereof are omitted. InFIG. 6, sensors14, except for a torque sensor20, are not shown.

The damper12ahas a damper body30a, an inverter32, and an electronic control unit34(ECU34). The damper body30ais provided with a connection section40, an outer tube50, a motor56, and a connection mechanism150as members on the side of a wheel (not shown). Furthermore, the damper body30ais provided with an inner tube42, a nut44, and a connection member152as members on the side of a vehicle body58.

An output shaft60of the motor56and a threaded shaft52are rotatably connected to the connection mechanism150. The connection mechanism150has a housing160, bearings162,164, a threaded-shaft-side pulley166, an endless belt168, a motor-side pulley170, and a bearing172.

The housing160has a threaded-shaft-side holding section174and a motor-side holding section176. The threaded-shaft-side holding section174fixes and supports the outer tube50and rotatably supports the threaded shaft52via the bearings162,164. The motor-side holding section176rotatably supports the output shaft60of the motor56via the bearing172. The motor-side holding section176also fixes and supports a side wall of the motor56.

The threaded-shaft-side pulley166is fixed to the threaded shaft52. The motor-side pulley170is fixed to the output shaft60of the motor56.

When an external vibration is input to the connection section40from a wheel side and the connection section40is applied with, for example, an upward thrust (a so-called damping direction) inFIG. 6, the outer tube50moves upward relative to the inner tube42and the nut44, thereby rotating the threaded shaft52. A rotational force of the threaded shaft52is transmitted to the output shaft60of the motor56via the threaded-shaft-side pulley166, the endless belt168, and the motor-side pulley170. In doing so, vibration of the spring of the suspension device can be damped by generating a reaction force from the motor56with respect to the threaded shaft52.

B2-1-2. Second Variation

FIG. 7is a simplified diagram illustrating a part of a vehicle10B in which an electromagnetic damper12b(hereinafter also referred to as “damper12b”) according to a second variation is mounted. The same components as the embodiment (FIG. 1) are denoted by the same reference signs, and explanations thereof are omitted. InFIG. 7, sensors14, except for a torque sensor20, are not shown.

The damper12bhas a damper body30b, an inverter32, and an electronic control unit34(ECU34). The damper body30bis provided with a connection section40and an inner rod200(rack shaft) as members on the side of a wheel (not shown). Furthermore, the damper body30bis provided with an outer tube50a, a pinion shaft202, and a motor56as members on the side of a vehicle body58. An output shaft60of the motor56is provided with a torque sensor20. The motor56is fixed to a housing204. As a relationship betweenFIG. 1andFIG. 6, the members on the side of the wheel and the members on the side of the vehicle body58may be exchanged.

A rack tooth212(rack gear) is formed on the inner rod200. A pinion214(pinion gear) is formed on the pinion shaft202. The rack tooth212and the pinion214form a rack and pinion mechanism210. The pinion shaft202is connected to the output shaft60of the motor56.

When an external vibration is input to the connection section40from a wheel side and the connection section40is applied with, for example, an upward thrust (a so-called damping direction) inFIG. 7, the inner rod200is displaced toward the outer tube50a, thereby rotating the pinion shaft202. A rotational force of the pinion shaft202is transmitted to the output shaft60of the motor56. In doing so, vibration of the spring of the suspension device can be damped by generating a reaction force from the motor56with respect to the pinion shaft202.

As a basic configuration of the damper body30b, an existing feature (see, for example, Japanese Unexamined Patent Application Publication No. 2009-150465, the entire contents of which are incorporated herein by reference) may be used.

B2-1-3. Third Variation

FIG. 8is a simplified diagram illustrating a part of a vehicle10C in which an electromagnetic damper12c(hereinafter also referred to as “damper12c”) according to a third variation is mounted. The same components as the embodiment (FIG. 1) are denoted by the same reference signs, and explanations thereof are omitted. InFIG. 8, sensors14, except for a torque sensor20, are not shown.

The damper12chas a damper body30c, an inverter32, and an electronic control unit34(ECU34). The damper body30cis provided with a connection section40aand a rotary arm250(hereinafter also referred to as “arm250”) as members on the side of a wheel (not shown). Furthermore, the damper body30cis provided with a reduction gear252and a motor56as members on the side of a vehicle body. An output shaft60of the motor56is provided with a torque sensor20. As a relationship betweenFIG. 1andFIG. 6, the members on the side of the wheel and the members on the side of the vehicle body58may be exchanged.

The connection section40a(pivotally connected to one (first) end of the arm250) is fixed to a knuckle (not shown) of a suspension device, thereby being connected to a wheel, while the other (second) end of the arm250is fixed to the output shaft of the motor56so that the arm250swingably moves around the other end to rotate together with the output shaft of the motor56. When an external vibration is input to the connection section40afrom a wheel side and the connection section40ais applied with, for example, an upward thrust (a so-called damping direction) inFIG. 8, the rotary arm250starts to rotate around a rotation axis Ax. In doing so, vibration of the spring of the suspension device can be damped by generating a reaction force from the motor56with respect to the rotary arm250via the reduction gear252.

As a basic configuration of the damper body30c, an existing feature (see, for example, Japanese Unexamined Patent Application Publication No. 2-227314, the entire contents of which are incorporated herein by reference) may be used.

In the embodiment, a three-phase AC brushless motor is used as the motor56, but is not limited thereto from the viewpoint of, for example, controlling the motor56so as to cancel a torsional torque Td. For example, the motor56may be a three-phase AC brush motor. In addition, the motor56may be a DC motor.

In the embodiment, the torque sensor20is arranged outside the motor56(FIGS. 1 and 6 to 8). However, the arrangement of the torque sensor20is not limited thereto from the viewpoint of, for example, detecting a torsional torque Td of a rotation shaft that transmits power of the motor56.

FIG. 9shows a variation of arrangement of the torque sensor20. As shown by a dashed line inFIG. 9, the torque sensor20may be arranged inside the motor56. Note that a double-dashed line inFIG. 9indicates the torque sensor20arranged outside the motor56.

In the embodiment, the torque sensor20is arranged so as to face the output shaft60of the motor56and detects a torsional torque Td of the output shaft60(the rotation shaft that transmits power of the motor56) (FIGS. 1 and 6 to 9). However, the detection of the torque sensor20is not limited thereto from the viewpoint of, for example, detecting a torsional torque Td of the rotation shaft that transmits power of the motor56.

For example, the torque sensor20may detect a torsional torque Td of the threaded shaft52(FIGS. 1 and 6), the pinion shaft202(FIG. 7) or the rotary arm250(FIG. 8). For example, inFIG. 6, the torque sensor20may be arranged on either the outer tube50or the threaded-shaft-side holding section174. If another rotation shaft is interposed between the output shaft60of the motor56and the threaded shaft52, a torsional torque Td of the rotation shaft may be used as a torsional torque Td of the output shaft60or the threaded shaft52.

B2-4-1. Correction Control Amount Calculation Section82

In the embodiment, the correction control amount calculation section82has both the vehicle speed reflection correction section102and the steering angle reflection correction section104(FIG. 3). However, the configuration of the correction control amount calculation section82is not limited thereto from the viewpoint of, for example, controlling the motor56so as to cancel a torsional torque Td. For example, the correction control amount calculation section82may have only one of the vehicle speed reflection correction section102and the steering angle reflection correction section104. Alternatively, the correction control amount calculation section82may have neither of the vehicle speed reflection correction section102and the steering angle reflection correction section104.

In the embodiment, the steering angle reflection correction section104adjusts the second gain G2on the basis of the steering angle speed Vθst (FIGS. 3 and 5). However, the adjustment of the steering angle reflection correction section104is not limited thereto from the viewpoint of, for example, adjusting a torsional torque Td according to the lateral acceleration of the vehicle10. For example, a steering angle θst itself, as an alternative to the steering angle speed Vθst, may be associated with the second gain G2. That is, as the steering angle θst (absolute value) increases, the second gain G2may be increased. Alternatively, the steering angle reflection correction section104may increase the second gain G2as a lateral acceleration (absolute value) detected by a lateral acceleration sensor (not shown) increases.

In the embodiment, the second subtracter118of the correction control amount calculation section82calculates the difference between the target reference current Iref_tar and the F/B current Ifb as the target motor current Imot_tar (FIG. 3). In other words, the correction control amount calculation section82reflects the difference ΔT1between the torque corresponding to the reference control amount Uref and the torsional torque Td in the reference control amount Uref with a unit of the current value [A] of the motor56. However, the unit is not limited thereto from the viewpoint of, for example, reflecting the difference between the torque corresponding to the reference control amount Uref and the torsional torque Td in the reference control amount Uref, and the calculation may be performed by using a different unit (such as torque [Nm] or force [N]).

In the embodiment, it is assumed that the ECU34is formed of a digital circuit (FIG. 1), but a part or the whole of the ECU34may be formed of an analog circuit.