Actuator for stabilizer

Abstract

To provide a stabilizer actuator that can efficiently adjust the torsion of the output shaft. [Solution] A stabilizer actuator A comprises a motor M having a cylindrical drive shaft 2 inside a case C, an output shaft 1 inserted through the drive shaft 2 and rotating relative to the drive shaft 2, and a reduction mechanism G that reduces the rotational drive of the motor M and transmits it to the first end 1a of the output shaft 1, and a first measuring unit provided between the case C and the drive shaft 2 to detect the rotational state of the drive shaft 2, a second measuring unit provided between the case C and the second end 1b of the output shaft 1 to detect the rotational state of the second end 1b, and a calculation unit ECU that calculates the torsional state of the output shaft 1 based on the difference between the detection result of the first measuring unit and the detection result of the second measuring unit.

Description

Technical Field

[0001] The present invention relates to an actuator that is capable of relatively torsionally driving stabilizer bars respectively connected to, for example, left and right wheels of a vehicle by motor drive.

Background Art

[0002] Conventionally, as such an actuator for a stabilizer, there is one disclosed in Patent Document 1, for example (see paragraphs

[0028] to

[0032] and Figs. 1 to 4).

[0003] This actuator for a stabilizer includes a first torsion bar 2 on one side, a second torsion bar 3 on the other side, and an actuator 4. The first torsion bar 2 is connected and fixed to a housing 5. Meanwhile, the second torsion bar 3 is connected and fixed to an output shaft 12 that is driven via a speed reduction gear 9 including a motor 7 and a planetary gear 8.

[0004] The second torsion bar 3 is connected to a planetary carrier 13 via a decoupling mechanism. The decoupling mechanism includes an inner star-shaped member 24 that holds a planetary gear 23, and an outer star-shaped member 25 arranged coaxially with the inner star-shaped member 24. A connection release piece 28 that is elastically torsionally deformable is arranged between the inner star-shaped member 24 and the outer star-shaped member 25.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0006] In the conventional stabilizer actuator described above, the first torsion bar 2 and the second torsion bar 3 are positioned at the ends of the housing 5, and since the length of the torsion bars cannot be sufficiently secured, the rigidity is high. A decoupling is provided between the second torsion bar 3 and the reduction gear 9, and since there is a difference between the rotation angle of the motor 7 and the amount of twist of the second torsion bar 3, it is necessary to detect the amount of twist of the torsion bar itself. However, because the rigidity of the torsion bar is high and the amount of twist is small, a dedicated torque sensor is required to detect minute twist angles.

[0007] However, there are various types of torque sensors. Magnetostrictive torque sensors detect the voltage change that occurs when a magnetic material is twisted by torque, changing its magnetic properties. Optical fiber torque sensors detect the phase change of light caused by the expansion and contraction of an optical fiber due to strain from torque acting on a rotating shaft. Electromagnetic induction torque sensors detect the change in electromagnetic induction that occurs within a rotating shaft due to the action of torque.

[0008] On the other hand, motors equipped with conventional stabilizer actuators often have resolvers to detect the rotation angle. The resolver distributes the primary and secondary windings to the drive shaft and bearing of the motor, which rotate relative to each other, and detects the alternating current generated by the change in the relative position of the two windings due to the rotation of the motor.

[0009] In conventional actuators, in order to improve the accuracy of motor-driven control of a torsion bar, it is necessary to match and compare the detected torsion bar twist value with the detected motor rotation angle value to adjust this twist. These two detected values ​​are AC current and voltage, which require matching effort, and since torque sensors are commonly used to detect the torsion bar twist, the matching effort for these detected values ​​has been a problem.

[0010] Furthermore, even when the torsion bar and actuator are directly connected without a decoupling mechanism as in conventional technology, the matching process is still necessary, and there is the inconvenience of the torsion bar being too short to measure torsional deformation. Thus, conventional actuators still have issues that need to be resolved, and there is a need for a stabilizer actuator that can accurately detect the torsional state of the left and right torsion bars and efficiently adjust the torsional state. [Means for solving the problem]

[0011] (Feature composition) The characteristic configuration of the stabilizer actuator according to the present invention is: Inside the case, A motor having a cylindrical drive shaft, An output shaft inserted through the drive shaft and rotating relative to the drive shaft, The system includes a reduction mechanism that reduces the rotational drive of the motor and transmits it to the first end of the output shaft, A first measuring unit is provided between the case and the drive shaft to detect the rotational state of the drive shaft, A second measuring unit is provided between the case and the second end of the output shaft to detect the rotational state of the second end, The device includes a calculation unit ECU that calculates the torsional state of the output shaft based on the difference between the detection result of the first measurement unit and the detection result of the second measurement unit.

[0012] (effect) This stabilizer actuator configuration can be applied to a suspension, for example, to dampen vertical movement occurring in the left and right wheels of a vehicle. Since vibrations in the wheels often differ between the left and right sides, the output shaft of the actuator is rotated in one direction or the other according to the vibration conditions of the suspension in order to effectively absorb this difference between the left and right sides.

[0013] In this configuration, a motor and reduction mechanism equipped with a first measuring unit are connected to the first end of the output shaft that outputs the motor's drive rotation, and a second measuring unit is connected to the second end. This allows the torsional state of the output shaft to be calculated from the difference between the detection result of the first measuring unit and the detection result of the second measuring unit, thereby allowing the state of the left and right suspensions to be determined.

[0014] The actuator can be further connected to left and right stabilizer bars, and the ECU (Electronic Control Unit) can accurately understand the suspension state by considering the elastic characteristics of the stabilizer bars used. Therefore, by using an actuator with this configuration, a high-quality active stabilizer can be constructed through a simple modification of the suspension.

[0015] (Feature composition) In the stabilizer actuator according to the present invention, the reduction mechanism is composed of a harmonic drive gear, the first measuring unit is equipped with a first resolver, and the second measuring unit is equipped with a second resolver.

[0016] (effect) This configuration detects the torsional state of the output shaft using two resolvers that easily detect rotation angles. Therefore, unlike conventional methods using torque sensors, the torsional state of the output shaft can be determined quickly and accurately.

[0017] Furthermore, many motors are equipped with resolvers for rotation detection, and by unifying both measurement units to resolvers, the overall configuration can be simplified while making it easier to compare detection data. This configuration is also advantageous in terms of cost.

[0018] Furthermore, in this configuration, since the reduction mechanism is a harmonic drive gear system, the play between components is significantly reduced compared to planetary gear mechanisms, etc. Therefore, the detection of the torsional state of the output shaft becomes more accurate.

[0019] (Feature composition) In the stabilizer actuator according to the present invention, it is advantageous that the output shaft includes a torsion region R1 that includes the first end portion, has a first diameter, and is formed over a length that is half or more of the output shaft, and a large-diameter region R2 that includes the second end portion and has a second diameter larger than the first diameter.

[0020] (Effect) In this configuration, the first end portion to which the speed reduction mechanism is connected is provided in the torsion region R1 having the small first diameter, and the second end portion to which the second measurement unit is connected is provided in the large-diameter region R2. With this configuration, the torsional deformation of the output shaft can be caused to occur mainly in the torsion region R1, and grasping the formation length of the torsion region R1 enables more accurate detection of the torsional state of the output shaft.

[0021] In this configuration, the second measurement unit is attached to the large-diameter region R2 including the second end portion, and the torsional deformation occurring in the large-diameter region R2 is slight. Therefore, strict accuracy is not required for the mounting position of the second measurement unit, and the mounting work of the second measurement unit becomes easier.

[0022] The first diameter and the length of the torsion region R1 are preferably set as appropriate according to the elastic characteristics and the like of the stabilizer bar connected to the actuator. [Brief Description of the Drawings]

[0023] [Figure 1] Cross-sectional view showing the configuration of the stabilizer actuator according to the first embodiment [Figure 2] Perspective view showing the main part configuration of the actuator according to the first embodiment [Figure 3] Cross-sectional view showing the configuration of the actuator according to the second embodiment [Figure 4] Perspective view showing the decoupling configuration according to the second embodiment [Mode for Carrying Out the Invention]

[0024] [First Embodiment] (Overview) Figure 1 shows, for example, an actuator A for a stabilizer according to the present invention (hereinafter referred to as "actuator A"). In a typical vehicle suspension, stabilizer bars B (hereinafter referred to as "bar B") are provided on the left and right wheels to mitigate vertical vibrations of the left and right wheels. In this actuator A, the left and right bars B are separated, and actuator A is provided between them. This actuator A can improve ride comfort by controlling the amount of twist of the left and right bars B and adjusting the difference in vertical movement of the left and right wheels. In this configuration, actuator A detects the twisting state of the bar B using an output shaft 1 provided inside actuator A.

[0025] (motor) The actuator A of this embodiment is equipped with a substantially cylindrical case C. The case C encloses the stator Mb, which is arranged around the rotor Ma of the motor M, and is compactly constructed to facilitate integration into a suspension system. A drive shaft 2 is inserted into the center of the rotor Ma. The drive shaft 2 has a hollow structure. An output shaft 1, described later, is inserted inside the drive shaft 2 in a manner that allows it to rotate relative to the drive shaft 2.

[0026] Various types of motors M can be used. However, one capable of detecting the rotation angle of the drive shaft 2 should be used. In this embodiment, a stepping motor equipped with a resolver 3 is used. Both ends of the drive shaft 2 of the motor M are supported by the case C by a first bearing 41 and a second bearing 42. The first resolver 31 is provided on one of the ends of the drive shaft 2.

[0027] The first resolver 31 includes an inner primary winding attached to the drive shaft 2 of the motor M and an outer secondary winding attached to the case C. As the motor M rotates, the relative position of the primary and secondary windings changes, generating an alternating current. This detected value is an analog signal because it is a current value, but unlike when using a conventional torque sensor, it is possible to quickly and accurately grasp the torsional state of the output shaft 1.

[0028] (Deceleration mechanism) The rotation of the drive shaft 2 is reduced by a reduction mechanism G located on the opposite side of the rotor Ma from the first resolver 31, and transmitted to one of the two ends of the output shaft 1, the first end 1a. In this embodiment, the reduction mechanism G is composed of, for example, a harmonic drive gear.

[0029] For example, as shown in Figure 1, the reduction mechanism G is housed in the case C adjacent to the motor M, and after significantly reducing the rotational speed of the drive shaft 2 of the motor M, it rotates the output shaft 1.

[0030] The drive shaft 2 is supported at both ends by a first bearing 41 and a second bearing 42, and one end is provided with, for example, a spline-shaped engaging portion Ga. The wave generator Gb engages with this engaging portion Ga by extrapolating. The wave generator Gb has a pair of arms that extend radially with respect to the rotation axis X, and ball members Gc that press against the flexspline Gd described later are provided at the ends of both arms.

[0031] The ball member Gc presses the substantially cylindrical external gear of the flexspline Gd from the inside outward. The pressed external teeth mesh with the internal teeth of the annular circular spline Ge located further outside. Multiple external teeth of the flexspline Gd near the portion pressed by the ball member Gc mesh with the internal teeth of the circular spline Ge, and the position of the internal teeth that mesh with the external teeth moves as the wave generator Gb rotates. The number of teeth on the external teeth is formed to be slightly less than the number of teeth on the internal teeth, so that the meshing position of the internal teeth and the external teeth changes by the difference in the number of teeth during one rotation of the wave generator Gb. This allows the drive rotation of the motor M to be transmitted to the output shaft 1 while being significantly reduced in speed.

[0032] The end of the flexspline Gd opposite to the external teeth becomes the output section Gf that acts on the output shaft 1. This output section Gf is also cylindrical, and its outer surface is pivotally supported on the inner surface of the case C via the third bearing 43. Splines, for example, are formed on the inner surface of the output section Gf and the outer surface of the output shaft 1, and the rotation of the motor M is transmitted to the output shaft 1.

[0033] By using a harmonic drive gear mechanism as the reduction mechanism G, the reduction mechanism G can be configured to be extremely compact, and the rotational speed of the motor M can be significantly reduced. In addition, the internal teeth of the circular spline Ge and the external teeth of the flexspline Gd mesh without backlash using multiple teeth, resulting in smooth reduction operation.

[0034] Furthermore, it is easy to set the reverse efficiency value to zero or negative for reverse input from the output shaft 1. By providing a reduction mechanism G with a reverse efficiency of zero or less, self-locking properties are achieved. For example, even when reverse input due to the raising and lowering of the wheels acts on the output shaft 1 during vehicle operation, no driven rotation occurs in the motor M. Therefore, when the vehicle height is not being actively adjusted, the output shaft 1 can function as a normal stabilizer bar B simply by stopping the power supply to the motor M.

[0035] (Output axis) The output end of the reduction mechanism G is spline-engaged, for example, to the first end 1a of the output shaft 1. A third bearing 43 is provided on the outer side of this spline engagement, and the output shaft 1 is rotatably supported by the case C via the output end. The other end of the output shaft 1, the second end 1b, is rotatably supported by the case C by a fourth bearing 44. A first bar B1 is connected to the first end 1a of the output shaft 1 via a first connecting part J1. A second bar B2 is connected to the second end 1b of the output shaft 1 via a second connecting part J2. These connections ensure that the output shaft 1 is connected to the first bar B1 and the second bar B2 without any play.

[0036] Furthermore, actuator A itself is not fixed to the vehicle body; rather, the intermediate points of the first bar B1 and the second bar B2 are rotatably attached to the vehicle body. As a result, when actuator A is driven, the first bar B1 and the second bar B2 twist relative to each other, correcting the vehicle's roll behavior.

[0037] As shown in Figure 1, the diameter of the output shaft 1 is varied along its longitudinal direction. Of this, the region including the first end 1a and extending for more than half the length of the output shaft 1 is defined as a torsional region R1 with a first diameter φ1. The region including the vicinity of the second end 1b is defined as a large-diameter region R2 with a second diameter φ2 that is larger than the first diameter φ1.

[0038] Specifically, the first end portion 1a, where the connection between the inner region of the rotor Ma and the wave drive gear is provided, is defined as the torsional region R1, and the portion where the second resolver 32 is attached is defined as the large-diameter region R2. In particular, the longitudinal length of the torsional region R1 is precisely defined.

[0039] By creating a small-diameter torsional region R1, the occurrence of torsional deformation is concentrated in this region, making it easier to detect the torsional state of the output shaft 1. Furthermore, by understanding the length of the torsional region R1, the detection of the torsional state of the output shaft 1 becomes more accurate. However, if the torsional stiffness is reduced excessively, torsional deformation will concentrate on the output shaft 1 before torsional deformation occurs in the first bar B1 and the second bar B2. Therefore, the torsional characteristics of the output shaft 1 are set considering the torsional characteristics of the first bar B1 and the second bar B2.

[0040] For example, if the torsional rigidity of output shaft 1 is excessively high compared to the torsional characteristics of the first bar B1 and the second bar B2, it becomes difficult to accurately detect vertical movement of the left and right wheels. On the other hand, if the torsional rigidity of output shaft 1 is excessively low, it will not be able to adequately absorb the vertical differential of the left and right wheels, and the durability of output shaft 1 will decrease. Therefore, the torsional rigidity of output shaft 1 should be set to approximately the same level as the torsional rigidity of the first bar B1 and the second bar B2 as a basic principle, and the combination of actuator A and the first bar B1 and the second bar B2 should be set according to the vehicle's usage.

[0041] Furthermore, the second resolver 32 is positioned in the large-diameter region R2 to allow for a tolerance in the mounting position of the second resolver 32. Most of the torsional deformation of the output shaft 1 occurs in the small-diameter torsional region R1. Therefore, even if there is some error in the installation position of the second resolver 32 within the range of the large-diameter region R2, it will not affect the detected value of the second resolver 32. This configuration simplifies the assembly of actuator A.

[0042] (Method for detecting the amount of torsion of the output shaft) In order to calculate the relative torsion of the first bar B1 and the second bar B2, the actuator A of this embodiment detects the torsion of the output shaft 1. As shown in Figure 1, a first measuring unit is provided between the case C and the drive shaft 2 to detect the rotational state of the drive shaft 2, such as the rotation angle, and a second measuring unit is provided between the case C and the second end 1b of the output shaft 1 to detect the rotational state of the second end 1b, such as the rotation angle.

[0043] Specifically, a first resolver 31 is provided as the first measurement unit, extending from the drive shaft 2 of the motor M to the case C. A second resolver 32 is provided as the second measurement unit, extending from the output shaft 1 to the case C. Both the first resolver 31 and the second resolver 32 are equipped with two windings. In the case of the first resolver 31, the inner primary winding is provided on the drive shaft 2, and the outer secondary winding is provided on the case C. Similarly, in the case of the second resolver 32, the inner primary winding is provided on the output shaft 1, and the outer secondary winding is provided on the case C. An ECU (Electronic Control Unit) is provided outside the actuator A, and it calculates the relative torsional rotation angle in the torsional region R1 of the output shaft 1 from the difference between the detected value of the first resolver 31 and the detected value of the second resolver 32.

[0044] When the first bar B1 and the second bar B2 twist and rotate relative to each other, a difference in height occurs between the left and right wheels. For example, when a vehicle is traveling on a right curve, the left front wheel moves closer to the vehicle body and the right front wheel moves further away from the vehicle body. In this case, the vehicle's driving posture can be restored by driving the motor M to equalize the detected values ​​of the first resolver 31 and the second resolver 32 or to reduce the difference between them.

[0045] By configuring both detection units with a first resolver 31 and a second resolver 32, the overall configuration is simplified, and the calculation of the detected values ​​becomes easier. This configuration is also advantageous in terms of cost. Furthermore, since the resolver can detect the relative rotation angle by the alternating current generated between opposing windings and has a simple structure, it is highly adaptable to various operating environments and has excellent durability. Therefore, when actuator A with this configuration is used as part of the suspension, which is the undercarriage structure of a vehicle, it provides high reliability.

[0046] [Second Embodiment] In the second embodiment, as shown in Figures 3 and 4, the output shaft 1 and the second bar B2 are integrated, and the output shaft 1 and the first bar B1 are connected by a decoupling D.

[0047] The decoupling D includes, for example, a concave outer portion D1 integrally formed at the end of the case C, into which a convex inner member D2 is coaxially inserted and arranged. In this state, a plurality of outer wall portions Da formed on the outer portion D1 and a plurality of inner wall portions Db formed on the inner member D2 are arranged alternately opposite each other, and an elastic member D3 made of a rubber material such as NBR is arranged between them.

[0048] By providing the decoupling D, the transmission of high-frequency micro-vibrations input from the wheels to the first bar B1 to the output shaft 1 is blocked, thereby improving the ride comfort of the vehicle. For example, when the vehicle is traveling on a road surface with slight irregularities, the torsional deformation of the first bar B1 is not transmitted to the second bar B2, and the slight high-frequency torsional deformation of both the first bar B1 and the second bar B2 is absorbed by the decoupling D.

[0049] On the other hand, when the vehicle is cornering, the relative torsion of the first bar B1 and the second bar B2 increases, and the compressive deformation of the elastic member D3 of the decoupling D is maximized while both bars B undergo torsional deformation. By providing the decoupling D in this way, the stabilizer as a whole exhibits low rigidity when the relative torsion of both bars B is small, and high rigidity is exhibited when the relative torsion exceeds a predetermined amount.

[0050] As in this configuration, measuring the amount of twist of the second bar B2 itself during the drive control of actuator A allows for a more accurate understanding of the vehicle's driving state. Furthermore, since the connection between the second bar B2 and the output shaft 1 is eliminated, play is reduced not only between these components but also throughout actuator A. This results in more accurate detection of the twist of the first bar B1 and the second bar B2. In addition, the drive operation of the first bar B1 and the second bar B2 becomes more responsive, and the cost of actuator A can be reduced due to the reduction in the number of parts. [Industrial applicability]

[0051] The stabilizer actuator of the present invention can be widely applied to stabilizers that, for example, actively adjust and control the roll state of the left and right front wheels or left and right rear wheels of a vehicle by motor drive. [Explanation of Symbols]

[0052] 1 Output shaft 1a 1st end 1b Second end 2 drive shafts 31 First resolver 32 Second resolver A Actuator for stabilizer C Case ECU calculation section G reduction mechanism M Motor R1 torsion area φ1 1st diameter R2 Large diameter region φ2 2nd diameter

Claims

1. Inside the case, A motor having a cylindrical drive shaft, An output shaft inserted through the drive shaft and rotating relative to the drive shaft, The system includes a reduction mechanism that reduces the rotational drive of the motor and transmits it to the first end of the output shaft, A first measuring unit is provided between the case and the drive shaft to detect the rotational state of the drive shaft, A second measuring unit is provided between the case and the second end of the output shaft to detect the rotational state of the second end, A stabilizer actuator comprising: a calculation unit ECU that calculates the torsional state of the output shaft based on the difference between the detection result of the first measurement unit and the detection result of the second measurement unit.

2. The stabilizer actuator according to claim 1, wherein the reduction mechanism is composed of a harmonic drive gear, the first measuring unit is equipped with a first resolver, and the second measuring unit is equipped with a second resolver.

3. The stabilizer actuator according to claim 1 or 2, wherein the output shaft includes a torsion region R1 that includes the first end and has a first diameter and is formed over a length of more than half the length of the output shaft, and a large-diameter region R2 that includes the second end and has a second diameter larger than the first diameter.

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