Vehicle vibration suppression device

Abstract

The present invention provides a vehicle vibration suppression device that can suppress vibrations generated in the bearings supporting the differential case. [Solution] Between the bearing 40 and the housing 26, there is a plurality of piezoelectric elements, one pair 50a, 50b and the other pair 50c, 50d, which are arranged symmetrically with respect to the axis CL. When the differential case rotation speed Nd is greater than or equal to a first predetermined value N1 (Nd≧N1), piezoelectric power generation control is performed, which generates electricity from the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d). As a result, when the differential case rotation speed Nd is high, greater than or equal to a first predetermined value N1 (Nd≧N1), electricity is generated from the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d) due to vibrations generated in the bearing 40, and the vibrations generated in the bearing 40 are absorbed as generated power, thus suppressing vibrations generated in the bearing 40.

Description

Technical Field

[0001] The present invention relates to a vibration suppression device for a vehicle equipped with a differential device.

Background Art

[0002] Differential devices mounted on vehicles are well known. For example, the differential device described in Patent Document 1 is such a device. Patent Document 1 discloses a lubrication structure of lubricating oil in a differential case in a differential device in which the differential case is supported by a non-rotating housing via bearings.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the differential device as described above, when the vehicle is traveling at high speed, that is, when the rotational speed of the differential case is high, there is a problem that vibration occurs in the bearings due to the radial clearance of the bearings and the runout of the drive shaft fitted to the differential case.

[0005] The present invention has been made against the background of the above circumstances, and an object thereof is to provide a vibration suppression device for a vehicle that can suppress vibration generated in the bearings that support the differential case.

Means for Solving the Problems

[0006] The gist of the first invention is a vibration suppression device for a vehicle equipped with a differential device in which the differential case is supported by a non-rotating housing via a bearing, (b) the vibration suppression device comprises a plurality of pairs of piezoelectric elements arranged between the bearing and the housing so as to be symmetrical with respect to the axis of the bearing, and (c) when the rotational speed of the differential case is greater than or equal to a first predetermined value, piezoelectric power generation control is performed, which generates electricity from the voltage output by the piezoelectric elements. [Effects of the Invention]

[0007] According to the first invention, the vibration suppression device includes a plurality of pairs of piezoelectric elements arranged symmetrically with respect to the axis of the bearing between the bearing and the housing, and when the rotational speed of the differential case is greater than or equal to a first predetermined value, piezoelectric power generation control is performed to generate electricity from the voltage output by the piezoelectric elements. As a result, when the rotational speed of the differential case is greater than or equal to a high first predetermined value, electricity is generated from the voltage output by the piezoelectric elements due to vibrations generated in the bearing, and the vibrations generated in the bearing are absorbed as generated power, thereby suppressing vibrations generated in the bearing. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates the schematic configuration of a vehicle to which the present invention is applied. [Figure 2] This diagram illustrates vibrations that occur in bearings. [Figure 3] This diagram illustrates an example of the configuration of a vibration suppression device. [Figure 4] This is a flowchart illustrating the key aspects of the control operation example of a vibration suppression device. [Figure 5] This diagram illustrates an example of the power generation operation of a piezoelectric element in a vibration suppression device. [Figure 6] This figure illustrates another embodiment of the vibration suppression device and corresponds to Figure 3. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily depicted accurately. [Examples]

[0010] Figure 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied. In Figure 1, the vehicle 10 includes a prime mover 12, such as an engine or electric motor, a transmission 14 that changes the rotation speed of the prime mover 12, a pair of left and right drive wheels 16 and 18, and a differential device 30 connected to the pair of left and right drive wheels 16 and 18 via a pair of left and right drive shafts 20. The above "left and right" refers to left and right with respect to the forward direction of the vehicle 10.

[0011] The differential device 30 is a known differential gear device that transmits the drive torque transmitted from the transmission 14 via the propeller shaft 22 to the drive wheels 16 and 18, which are connected via the drive shaft 20, while allowing differential between them. The propeller shaft 22 is connected to the final gear 24, and torque is transmitted to the differential case 32 by the meshing of the final gear 24 and the differential ring gear 32a, which is integrally connected to the differential case 32. The differential case 32 is rotatably supported around the axis CL by a housing 26, which is a non-rotating member fixed to the vehicle body via bearings 40 and 42.

[0012] Furthermore, the vehicle 10 is equipped with a vibration suppression device 60. The vibration suppression device 60 includes piezoelectric elements 50 (50a, 50b, 50c, 50d), piezoelectric elements 52 (52a, 52b, 52c, 52d), a piezoelectric element control circuit 62, a battery 64, an electronic control device 66, and the like.

[0013] The piezoelectric element 50 is positioned between the outer diameter surface of the bearing 40 and the housing 26, and the piezoelectric element 52 is positioned between the outer diameter surface of the bearing 42 and the housing 26. A pair (two) of conductive wires is connected to the electrodes of each piezoelectric element 50 and 52, and each conductive wire is connected to the piezoelectric element control circuit 62. The piezoelectric elements 50 and 52 are so-called piezoelectric elements that, for example, generate a voltage between the electrodes when a load is applied in a certain direction (hereinafter referred to as the displacement direction) causing expansion and contraction displacement in the element, and expand and contract in the displacement direction when a voltage (power) is applied between the electrodes.

[0014] The piezoelectric element control circuit 62 controls the operation of each of the piezoelectric elements 50 and 52. There are three operating states: detection mode, power generation mode, and drive mode. Switching between modes and control operations are performed based on control commands from the electronic control device 66, which will be described later. In detection mode, the voltage Vpd output by each of the piezoelectric elements 50 and 52 is detected by the application of a load and output to the electronic control device 66. The magnitude of the displacement due to the load, i.e., the magnitude of the vibration, is detected by the magnitude of the voltage Vpd. In power generation mode, the voltage Vpd output from the piezoelectric elements 50 and 52 is converted into rechargeable power through processes such as rectification and step-up / step-down processing, and charged to the battery 64. In drive mode, applied power is generated from the stored power of the battery 64 through processes such as application direction control and step-up / step-down processing, and applied to the piezoelectric elements 50 and 52, causing the piezoelectric elements 50 and 52 to operate as actuators that expand and contract in the direction of displacement. The battery 64 is a power storage device capable of transferring power.

[0015] The electronic control unit 66 functions as a controller for controlling the piezoelectric elements 50 and 52, and includes a so-called microcomputer. The electronic control unit 66 outputs a piezoelectric element control command signal Spd to the piezoelectric element control circuit 62, which commands the operating state (detection mode, power generation mode, drive mode) of each of the piezoelectric elements 50 and 52, and the applied power in the case of drive mode. In addition, the piezoelectric element control circuit 62 supplies the electronic control unit 66 with the voltage Vpd output by each of the piezoelectric elements 50 and 52 in detection mode.

[0016] In addition, the electronic control unit 66 is supplied with the transmission output rotational speed No based on the detection value by the transmission output rotational speed sensor 70 provided in the vehicle 10. The transmission output rotational speed No corresponds to the differential case rotational speed Nd of the differential case 32. Note that the electronic control unit 66 may be realized as one of the functional blocks of the control device that performs various controls of the vehicle 10.

[0017] By the way, in the differential device 30, when the vehicle 10 is traveling at high speed, that is, when the rotational speed of the differential case 32 is high, there has been a problem that vibrations occur in the bearings 40 and 42 due to the radial clearances of the bearings 40 and 42 and the runout of the drive shaft 20 fitted to the differential case 32.

[0018] FIG. 2 is a diagram for explaining an example of the vibration generated in the bearings 40 and 42, where the horizontal axis represents the frequency component of the vibration and the vertical axis represents the vibration level. When the rotational speed of the differential case 32 is high, N - order vibrations occur in which the frequency components of the generated vibrations cover higher orders.

[0019] FIG. 3 is a diagram for explaining an example of the configuration of the vibration suppression device 60. In the vibration suppression device 60, the piezoelectric element 50 and the piezoelectric element 52 are symmetric about the vehicle width direction of the vehicle 10 and have the same configuration. Therefore, hereinafter, the piezoelectric element 50 will be described and the description of the piezoelectric element 52 will be omitted. FIG. 3(a) is a cross - sectional view of the periphery of the piezoelectric element 50 in the vibration suppression device 60 as viewed from directly above the vehicle 10 with the axis CL as the center. Further, FIG. 3(b) is a schematic view of the bearing 40 and the piezoelectric element 50 in FIG. 3(a) as viewed from the left side of the vehicle with the axis CL as the center. In FIGS. 3(a) and (b), the conductive wires connected to the electrodes are omitted for each of the piezoelectric elements 50.

[0020] As shown in FIG. 3(a), the piezoelectric element 50 is located at the position where the action line FL (see the two - dotted chain line in the figure) indicating the direction in which the load acts on the bearing 40 intersects the outer diameter surface 40a, and is arranged between the outer diameter surface 40a and the housing 26 in a direction in which the displacement direction is the radial direction of the bearing 40.

[0021] Next, Figure 3(b) will explain the arrangement of each piezoelectric element 50 (50a, 50b, 50c, 50d) in the circumferential direction of the bearing 40. In Figure 3(b), the circumferential position of the bearing 40 (hereinafter referred to as phase) is defined by the clockwise rotation angle θ of the axis CL from phase A, which is the front side of the vehicle in the longitudinal direction of the vehicle 10. Piezoelectric elements 50a and 50b form a pair, and as shown in Figure 3(b), piezoelectric element 50a is positioned on the outer diameter surface 40a of phase A, and piezoelectric element 50b is positioned on the outer diameter surface 40a of phase C (rotation angle θ = 180°), which is symmetrical with respect to the axis CL with respect to piezoelectric element 50a. Similarly, piezoelectric elements 50c and 50d form the other pair, with piezoelectric element 50c positioned on the outer diameter surface 40a at phase B, where the rotation angle θ = 90°, and piezoelectric element 50d positioned on the outer diameter surface 40a at phase D (at rotation angle θ = 270°), which is symmetrical with respect to the axis CL with respect to piezoelectric element 50c. Thus, the piezoelectric element 50 is provided with multiple piezoelectric elements, one pair of piezoelectric elements 50a and 50b, and the other pair of piezoelectric elements 50c and 50d.

[0022] Figure 4 is a flowchart illustrating the main parts of a control operation example of the vibration suppression device 60, and is a flowchart illustrating a control operation example of vibration suppression occurring in the bearing 40, performed by the electronic control device 66. This flowchart is executed repeatedly, for example.

[0023] In Figure 4, each step in the flowchart corresponds to a function of the electronic control unit 66. First, in step S10 (the step will be omitted hereafter), it is determined whether the differential case rotation speed Nd is high. This determination is made, for example, by determining whether the differential case rotation speed Nd is greater than or equal to a first predetermined value N1. The first predetermined value N1 is set in advance, either by design or experiment, to a suitable value that allows it to be determined that the differential case rotation speed Nd is high and that Nth-order vibration may occur due to play in the radial clearance of the bearing 40 or runout of the drive shaft 20 fitted into the differential case 32. If the determination in S10 is negative, this routine is terminated.

[0024] If the determination in S10 is affirmative, in S20 it is determined whether the differential case rotation speed Nd is greater than or equal to the allowable rotation speed, that is, whether it is greater than or equal to the second predetermined value N2 which is greater than the first predetermined value N1. If the determination in S20 is negative, in S30 piezoelectric power generation control is performed to set the operating state of each piezoelectric element 50 (50a, 50b, 50c, 50d) to power generation mode and generate electricity, and this routine is terminated. As a result, if the first predetermined value N1 ≤ differential case rotation speed Nd < second predetermined value N2, electricity is generated from the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d) due to vibrations generated in the bearing 40, and the generated power is charged to the battery 64. Therefore, since the vibrations generated in the bearing 40 are absorbed as generated power, the vibrations generated in the bearing 40 are suppressed.

[0025] If the judgment in S20 is affirmed, that is, if the differential case rotation speed Nd is greater than or equal to the second predetermined value N2, piezoelectric displacement control is performed from S40 to S60. First, in S40, the operating state of the piezoelectric elements 50 (50a, 50b, 50c, 50d) is set to detection mode. Next, in S50, the phase in which a large displacement (vibration) occurs in the bearing 40 is identified from the voltage Vpd of each piezoelectric element 50 (50a, 50b, 50c, 50d). This identification is performed, for example, as follows. Figure 5 is a graph showing the change in the voltage Vpd (vertical axis) output by each piezoelectric element 50 (50a, 50b, 50c, 50d) over the period of one rotation of the differential case 32 (horizontal axis), and is an example of a case where a large displacement occurs in the phase SV (position of rotation angle θ=θv) in Figure 3(b). By applying the magnitude and correlation of the changes in the voltage Vpd of each detected piezoelectric element 50 (50a, 50b, 50c, 50d) to calculation formulas or maps that have been determined in advance through design or experiment, the rotation angle θv is calculated, and the phase SV with the largest displacement (hereinafter referred to as the specific phase) is identified. The specific phase SV corresponds to the "maximum position" in this invention.

[0026] Next, in S60, the piezoelectric element 50 closest to the specific phase SV identified in S50 is set to drive mode. The closest piezoelectric element 50 is the one whose distance between the specific phase SV (rotation angle θ=θv) and the rotation angle is the smallest. For example, in Figure 3(b), piezoelectric element 50a is set to drive mode if 0°≦θv≦45° or 315°<θv≦360°, piezoelectric element 50c if 45°<θv≦135°, piezoelectric element 50b if 135°<θv≦225°, and piezoelectric element 50d if 225°<θv≦315°. Power is then applied to the piezoelectric element 50 set to drive mode to generate a displacement in the direction that cancels out the displacement value detected in S50, and this routine is terminated. The power application is, for example, a specific phase SV as shown in Figure 3(b). When the piezoelectric element 50a is set to drive mode, power is generated and applied in such a way as to cancel out the displacement of the voltage Vpd of the piezoelectric element 50a detected in Figure 5. As a result, if the differential case rotation speed Nd becomes faster than the second predetermined value N2, which is the allowable rotation speed, and vibrations become large, the piezoelectric element 50 generates a displacement in a direction that cancels out the vibrations, thereby suppressing vibrations generated in the bearing 40. The second predetermined value N2 is set in advance, either experimentally or through design, to a suitable value that can be determined to be large when vibrations become large.

[0027] As described above, the vibration suppression device 60 of this embodiment is provided between the bearing 40 and the housing 26, and consists of one pair of piezoelectric elements 50a, 50b and the other pair of piezoelectric elements 50c, 50d, which are arranged symmetrically with respect to the axis CL. When the differential case rotation speed Nd is greater than or equal to a first predetermined value N1 (Nd≧N1), piezoelectric power generation control is performed, which generates electricity from the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d). As a result, when the differential case rotation speed Nd is high, greater than or equal to a first predetermined value N1 (Nd≧N1), electricity is generated from the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d) due to vibrations generated in the bearing 40, and the vibrations generated in the bearing 40 are absorbed as generated power, thus suppressing vibrations generated in the bearing 40.

[0028] Furthermore, according to the vibration suppression device 60 of this embodiment, when the differential case rotation speed Nd is greater than or equal to a second predetermined value N2 (Nd≧N2>N1) which is greater than a first predetermined value N1, instead of piezoelectric power generation control, a specific phase SV of vibration occurring in the bearing 40 is identified from the voltage Vpd output by the piezoelectric element 50, and piezoelectric displacement control is performed by applying power to the piezoelectric element 50 located near the specific phase SV to generate a displacement in the direction of suppressing vibration. As a result, when the differential case rotation speed Nd becomes faster than or equal to the second predetermined value N2 which is the allowable rotation speed, and vibrations become large, the piezoelectric element 50 generates a displacement in the direction of canceling out the vibrations, thereby suppressing vibrations occurring in the bearing 40.

[0029] Furthermore, according to the vibration suppression device 60 of this embodiment, the piezoelectric element 50 is positioned between the outer diameter surface 40a of the bearing 40 and the housing 26. This provides the effects described above.

[0030] Furthermore, with the vibration suppression device 60 of this embodiment, the control operation of the flowchart in Figure 6 is similarly applied to the bearing 42 on which the piezoelectric element 52 is located, and the same effects as described above can be obtained.

[0031] Next, other embodiments of the present invention will be described. In the following description, parts common to multiple embodiments will be denoted by the same reference numerals and their descriptions will be omitted. [Examples]

[0032] The vibration suppression device 80 is an improved version of the vibration suppression device 60 of Example 1, with the addition of piezoelectric elements 54 (54a, 54b, 54c, 54d). It includes a piezoelectric element control circuit (not shown), a battery, an electronic control device, etc., corresponding to the addition of the piezoelectric elements 54. Figure 6 is a diagram illustrating an example of the configuration of the vibration suppression device 80, and corresponds to Figure 3 of Example 1 described above.

[0033] Figure 6(a) is a cross-sectional view of the area around the piezoelectric elements 50 and 54 in the vibration suppression device 80, viewed from vertically above the vehicle 10 with the axis CL as the center. Figure 6(b) is a schematic diagram of the bearing 40 and piezoelectric element 50 in Figure 6(a), viewed from the left side of the vehicle with the axis CL as the center. Note that in Figures 6(a) and (b), the conductive wires connected to the electrodes of the piezoelectric elements 50 and 54 are omitted.

[0034] As shown in Figure 6(a), the piezoelectric element 54 is positioned between the left-side end face 40b of the bearing 40 and the housing 26, with its displacement direction parallel to the axis CL.

[0035] Next, Figure 6(b) will explain the arrangement of each of the piezoelectric elements 54 (54a, 54b, 54c, 54d) in the circumferential direction of the bearing 40. Piezoelectric elements 54a and 54b form one pair, and similar to piezoelectric element 50, piezoelectric element 54a is positioned on the end face 40b of phase A, and piezoelectric element 54b is positioned on the end face 40b of phase C, which is symmetrical with respect to piezoelectric element 54a with respect to the axis CL. Similarly, piezoelectric elements 54c and 54d form the other pair, and piezoelectric element 54c is positioned on the end face 40b of phase B, and piezoelectric element 54d is positioned on the end face 40b of phase D, which is symmetrical with respect to piezoelectric element 54a with respect to the axis CL. Thus, multiple piezoelectric elements are provided, consisting of one pair of piezoelectric elements 54a and 54b, and the other pair of piezoelectric elements 54c and 54d.

[0036] When the piezoelectric elements 54 (54a, 54b, 54c, 54d) are added, vibrations occur in the axial direction (axis CL direction) of the bearing 40 due to the meshing reaction force KF (see black arrow in the figure) between the final gear 24 and the differential ring gear 32a. In such cases, the control operation of the flowchart in Figure 6 is applied similarly to these vibrations, and the vibrations are suppressed.

[0037] As described above, in the vibration suppression device 80 of this embodiment, the piezoelectric element 54 is positioned between the axial end face 40b of the bearing 40 and the housing 26. This provides the same effect as in the previous embodiment 1 against vibrations occurring in the axial direction (axis CL direction) of the bearing 40.

[0038] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0039] For example, in the aforementioned Embodiments 1 and 2, one of the pair of piezoelectric elements was positioned in the longitudinal direction of the vehicle 10, and the other in the vertical direction. However, the orientation of the elements is not limited to this. The pair is arranged symmetrically with respect to the axis CL, and each element is positioned in a direction suitable for vibration suppression.

[0040] Furthermore, in the aforementioned Examples 1 and 2, the pair of piezoelectric elements arranged consisted of two pairs, one and the other, but this is not limited to two pairs. Multiple elements suitable for vibration suppression can be arranged as appropriate.

[0041] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of Symbols]

[0042] 10: Vehicle 26: Housing 30: Differential device 32: Differential case 40, 42: Bearing 40a: Outer diameter surface 40b: End face 50, 52, 54: Piezoelectric element 60, 80: Vibration suppression device CL: Axis center N1: First predetermined value N2: Second predetermined value Nd: Differential case rotation speed (rotation speed) Vpd: Voltage SV: Specific phase (maximum position)

Claims

1. A vibration suppression device for a vehicle equipped with a differential device in which the differential case is supported by a non-rotating housing via bearings, The vibration suppression device comprises a plurality of pairs of piezoelectric elements positioned between the bearing and the housing, such that they are symmetrically arranged relative to the axis of the bearing. If the rotational speed of the differential case is equal to or greater than a first predetermined value, piezoelectric power generation control is performed, which generates electricity from the voltage output by the piezoelectric element. A vehicle vibration suppression device characterized by the following features.

2. If the rotational speed of the differential case is greater than or equal to a second predetermined value (which is greater than the first predetermined value), the vibration suppression device, instead of the piezoelectric power generation control, identifies the maximum position of vibration occurring in the bearing from the voltage output by the piezoelectric element, and performs piezoelectric displacement control by applying power to the piezoelectric element located near the maximum position to generate a displacement in a direction that cancels out the vibration. The vehicle vibration suppression device according to feature 1.

3. The piezoelectric element is positioned between the outer diameter surface of the bearing and the housing. A vehicle vibration suppression device according to claim 1 or 2.

4. The piezoelectric element is positioned between the axial end face of the bearing and the housing. A vehicle vibration suppression device according to claim 1 or 2.

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