Vibration suppression device for vehicle

Abstract

The invention provides a vibration suppression device for a vehicle capable of suppressing vibration generated in a bearing supporting a differential housing. A plurality of piezoelectric elements are provided between the bearing and the housing, the piezoelectric elements being a pair of piezoelectric elements on one side and a pair of piezoelectric elements on the other side which are arranged symmetrically with respect to the axial center, and performing piezoelectric power generation control when the rotational speed of the differential case is equal to or greater than a first predetermined value, and performing piezoelectric power generation control when the rotational speed of the differential case is equal to or greater than a second predetermined value. The piezoelectric power generation control generates power according to the voltage output by the piezoelectric element. Thus, when the rotational speed of the differential case is equal to or greater than a high-speed first prescribed value, power is generated from the voltage output by the piezoelectric element due to the vibration generated in the bearing, and the vibration generated in the bearing is absorbed as the generated power, so that the vibration generated in the bearing is suppressed.

Description

Technical Field

[0001] This invention relates to a vibration suppression device for a vehicle equipped with a differential. Background Technology

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

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-100504 Summary of the Invention

[0004] In the differential device described above, there is a problem that when the vehicle is traveling at high speed, that is, when the differential housing rotates at high speed, the bearing vibrates due to the radial clearance of the bearing or the oscillation of the drive shaft that is fitted with the differential housing.

[0005] The present invention was made against the background described above, and its object is to provide a vibration suppression device for a vehicle that can suppress vibrations generated in the bearing supporting the differential housing.

[0006] The purpose of the first invention is to (a) provide a vibration suppression device for a vehicle, the vehicle having a differential assembly, the differential housing of the differential assembly being supported by a bearing on a non-rotating housing, wherein the vibration suppression device for the vehicle, (b) provides a plurality of piezoelectric elements between the bearing and the housing, the piezoelectric elements being a pair of piezoelectric elements symmetrically arranged about the axis of the bearing, and (c) perform piezoelectric power generation control when the rotational speed of the differential housing is above a first predetermined value, the piezoelectric power generation control generating electricity based on the voltage output by the piezoelectric elements.

[0007] Invention Effects

[0008] According to the first invention, the vibration suppression device includes a plurality of piezoelectric elements between the bearing and the housing. These piezoelectric elements are a pair symmetrically arranged about the axis of the bearing. When the rotational speed of the differential housing is above a first predetermined value, piezoelectric power generation control is performed, generating electricity based on the voltage output by the piezoelectric elements. Thus, when the rotational speed of the differential housing is above a high first predetermined value, electricity is generated based on the voltage output by the piezoelectric elements due to vibrations generated in the bearing. The vibrations generated in the bearing are absorbed as generated electricity, thereby suppressing the vibrations in the bearing. Attached Figure Description

[0009] Figure 1 This is a diagram illustrating the general structure of a vehicle to which the present invention is applied.

[0010] Figure 2 This is a diagram illustrating the vibrations generated in the bearing.

[0011] Figure 3 This is a diagram illustrating an example of the structure of a vibration suppression device.

[0012] Figure 4 This is a flowchart illustrating the main parts of the control operation of the vibration suppression device.

[0013] Figure 5 This diagram illustrates an example of the power generation operation of the piezoelectric element in a vibration suppression device.

[0014] Figure 6 This is a diagram illustrating another embodiment of the vibration suppression device, and is equivalent to... Figure 3 The image. Detailed Implementation

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the parts are not necessarily depicted accurately.

[0016] [Example 1]

[0017] Figure 1 This is a diagram illustrating the schematic structure of the vehicle 10 to which the present invention is applied. Figure 1 In this vehicle 10, for example, there are: a prime mover 12 such as an engine or an 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 that is connected to the pair of left and right drive wheels 16 and 18 via a pair of left and right drive shafts 20. In addition, the term "left and right" refers to left and right relative to the direction of travel of the vehicle 10.

[0018] The differential assembly 30 is a known differential gear assembly that transmits the drive torque from the transmission 14 via the drive shaft 22 to the drive wheels 16 and 18 connected to them via the drive shaft 20, allowing differential movement between them. The drive shaft 22 is connected to the final drive gear 24, and the torque is transmitted to the differential housing 32 through the engagement of the final drive gear 24 with the differential ring gear 32a integrally connected to the differential housing 32. The differential housing 32 is fixed to the non-rotating component of the vehicle body, namely the outer shell 26, via bearings 40 and 42 in a manner that allows it to rotate about the axis CL.

[0019] 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, etc.

[0020] Piezoelectric element 50 is disposed between the outer diameter surface of bearing 40 and housing 26, and piezoelectric element 52 is disposed between the outer diameter surface of bearing 42 and housing 26. A pair (2) of conductive wires are connected to the electrodes of each of piezoelectric element 50 and 52, and the conductive wires are respectively connected to piezoelectric element control circuit 62. Piezoelectric elements 50 and 52 are, for example, so-called piezoelectric elements with the following characteristics: when a load is applied in a certain direction (hereinafter, denoted as the displacement direction) to cause the element to expand or contract, a voltage is generated between the electrodes, and when a voltage (electric power) is applied between the electrodes, expansion or contraction is generated along the displacement direction.

[0021] The piezoelectric element control circuit 62 controls the operation of piezoelectric elements 50 and 52 respectively. The operating states include detection mode, power generation mode, and drive mode. Switching between or controlling each mode is based on control commands from the electronic control device 66, described later. In detection mode, the voltage Vpd output by piezoelectric elements 50 and 52 is detected by applying a load and output to the electronic control device 66. The magnitude of the displacement caused by the load, i.e., the magnitude of the vibration, is detected based on the magnitude of the voltage Vpd. In power generation mode, the voltage Vpd output from piezoelectric elements 50 and 52 is converted into electricity that can be charged through rectification or buck-boost processing, and the battery 64 is charged. In drive mode, power is generated from the stored power in the battery 64, for example, by applying directional control or buck-boost processing, and applied to the piezoelectric elements 50 and 52, acting as actuators that cause the piezoelectric elements 50 and 52 to extend or retract in the displacement direction. The battery 64 is an energy storage device capable of power transmission and reception.

[0022] The electronic control device 66 functions as a controller for controlling the piezoelectric elements 50 and 52, and is configured to include a microcomputer. The electronic control device 66 outputs piezoelectric element control circuit 62 the operating state (detection mode, power generation mode, drive mode) of each of the piezoelectric elements 50 and 52, and the piezoelectric element control command signal Spd for applying power in drive mode. Furthermore, the voltage Vpd output by the piezoelectric elements 50 and 52 in detection mode is supplied from the piezoelectric element control circuit 62 to the electronic control device 66.

[0023] Furthermore, the transmission output speed No, based on the detected value by the transmission output speed sensor 70 provided by the vehicle 10, is supplied to the electronic control unit 66. The transmission output speed No corresponds to the differential housing speed Nd of the differential housing 32. In addition, the electronic control unit 66 can also be implemented as one of the functional blocks of the control device for performing various controls on the vehicle 10.

[0024] In the differential device 30, there is a problem that when the vehicle 10 is traveling at high speed, that is, when the rotational speed of the differential housing 32 is high, the bearings 40 and 42 vibrate due to the radial clearance of the bearings 40 and 42 or the oscillation of the drive shaft 20 that is fitted with the differential housing 32.

[0025] Figure 2 This diagram illustrates an example of vibration generated in bearings 40 and 42. The horizontal axis represents the frequency components of the vibration, and the vertical axis represents the vibration level. When the differential housing 32 rotates at high speed, the frequency components of the vibration are generated at the higher Nth order.

[0026] Figure 3 This is a diagram illustrating an example of the structure of the vibration suppression device 60. In the vibration suppression device 60, the piezoelectric element 50 and the piezoelectric element 52 are symmetrical about each other in the width direction of the vehicle 10 and have the same structure. Therefore, the piezoelectric element 50 will be described below, and the piezoelectric element 52 will be omitted. Figure 3 (a) is a cross-sectional view of the area surrounding the piezoelectric element 50 in the vibration suppression device 60, viewed vertically above the vehicle 10 with the axis CL as the center. Furthermore, Figure 3 (b) Viewed from the left side of the vehicle with the axle CL as the center. Figure 3 A schematic diagram of bearing 40 and piezoelectric element 50 in (a). Additionally, in Figure 3 In (a) and (b), the conductive lines connecting to the respective electrodes of the piezoelectric element 50 are omitted.

[0027] like Figure 3 As shown in (a), the piezoelectric element 50 is positioned at the intersection of the line of action FL (double-dotted line in the reference figure) indicating the direction of the load applied to the bearing 40 and the outer diameter surface 40a, and is positioned between the outer diameter surface 40a and the housing 26, with the displacement direction being radial in the bearing 40.

[0028] Next, using Figure 3 (b) The arrangement of the piezoelectric elements 50 (50a, 50b, 50c, 50d) in the circumferential direction of the bearing 40 is described. Figure 3In (b), with phase A on the front side of the vehicle 10 in the longitudinal direction as a reference, the circumferential position of the bearing 40 (hereinafter referred to as phase) is defined by a clockwise rotation angle θ about the axis CL from phase A. Piezoelectric elements 50a and 50b constitute a pair on one side, as shown... Figure 3 As shown in (b), piezoelectric element 50a is disposed on the outer diameter surface 40a of phase A, and piezoelectric element 50b is disposed on the outer diameter surface 40a of phase C (rotation angle θ = 180°) at a position symmetrical to piezoelectric element 50a about the axis CL. Similarly, piezoelectric elements 50c and 50d form a pair on the other side, with piezoelectric element 50c disposed on the outer diameter surface 40a of phase B at a rotation angle θ = 90°, and piezoelectric element 50d disposed on the outer diameter surface 40a of phase D (rotation angle θ = 270°) at a position symmetrical to piezoelectric element 50c about the axis CL. Thus, there are multiple piezoelectric elements 50, namely, a pair of piezoelectric elements 50a and 50b on one side and a pair of piezoelectric elements 50c and 50d on the other side.

[0029] Figure 4 This is a flowchart illustrating the main part of the control operation example of the vibration suppression device 60, and it is a flowchart illustrating the control operation example of vibration suppression generated in the bearing 40 executed by the electronic control device 66. This flowchart is executed repeatedly, for example.

[0030] exist Figure 4 In this flowchart, each step corresponds to the function of the electronic control device 66. First, in step S10 (hereinafter, steps are omitted), it is determined whether the differential housing speed Nd is high speed. This determination is made, for example, by determining whether the differential housing speed Nd is a first predetermined value N1 or higher. The first predetermined value N1 is, for example, a preferred value that can be pre-designed or experimentally set to determine that the differential housing speed Nd is high speed and that N vibrations can be generated due to the radial clearance of the bearing 40 or the oscillation of the drive shaft 20, which is fitted with the differential housing 32. If the determination in S10 is negative, this routine ends.

[0031] If the determination in S10 is affirmative, in S20, it is determined whether the differential housing speed Nd exceeds the permissible speed, that is, whether it exceeds the second specified value N2, which is greater than the first specified value N1. If the determination in S20 is negative, in S30, piezoelectric power generation control is performed to set the operating state of each of the piezoelectric elements 50 (50a, 50b, 50c, 50d) to power generation mode, and the routine ends. Thus, when the first specified value N1 ≤ differential housing speed Nd < the second specified value N2, power is generated based on the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d) due to the vibration generated in the bearing 40, and the generated power charges the battery 64. Therefore, the vibration generated in the bearing 40 is absorbed as generated power, and thus the vibration generated in the bearing 40 is suppressed.

[0032] If the determination in S20 is affirmed, that is, if the differential housing speed Nd is greater than or equal to the second predetermined value N2, piezoelectric displacement control is performed in 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 determined based on the voltage Vpd of each of the piezoelectric elements 50 (50a, 50b, 50c, 50d). This determination is performed, for example, as follows. Figure 5 This is a graph showing the shift of the voltage Vpd (vertical axis) output by the piezoelectric elements 50 (50a, 50b, 50c, 50d) during rotation of the differential housing 32 (horizontal axis), for example, Figure 3 (b) is an example of a large displacement of phase SV (position with rotation angle θ = θv). By applying the magnitude and correlation of the voltage Vpd of the detected piezoelectric elements 50 (50a, 50b, 50c, 50d) to a pre-designed or experimentally derived formula or mapping table, the rotation angle θv is calculated, and the phase with the large displacement (hereinafter referred to as the specific phase) SV is determined. The specific phase SV corresponds to the "maximum position" of this invention.

[0033] Next, in S60, the piezoelectric element 50 closest to the specific phase SV determined in S50 is set to drive mode. The closest piezoelectric element 50 is the element whose interval between the specific phase SV (rotation angle θ = θv) and the rotation angle is the smallest. For example, in Figure 3In (b), when 0°≤θv≤45° or 315°<θv≤360°, piezoelectric element 50a is set to drive mode; when 45°<θv≤135°, piezoelectric element 50c is set to drive mode; when 135°<θv≤225°, piezoelectric element 50b is set to drive mode; and when 225°<θv≤315°, piezoelectric element 50d is set to drive mode. Then, an electric current is applied to the piezoelectric element 50 set to drive mode to generate a displacement in a direction that counteracts the displacement value detected in S50, thus ending this routine. Regarding the application of electric current, for example, when… Figure 3 (b) In the case of a specific phase SV as shown and the piezoelectric element 50a being set to drive mode, to counteract the Figure 5 The voltage Vpd of the piezoelectric element 50a is detected and applied in a manner that generates and applies electrical power. Therefore, when the differential housing speed Nd rapidly reaches or exceeds the permissible speed (i.e., the second predetermined value N2) and vibration increases, the piezoelectric element 50 generates a displacement in the direction that counteracts the vibration, thus suppressing the vibration generated in the bearing 40. The second predetermined value N2 is pre-designed or experimentally set as a preferred value that indicates increased vibration.

[0034] As described above, the vibration suppression device 60 according to this embodiment includes a plurality of piezoelectric elements between the bearing 40 and the housing 26. These piezoelectric elements are a pair of piezoelectric elements 50a and 50b on one side and a pair of piezoelectric elements 50c and 50d on the other side, arranged symmetrically with respect to the shaft center CL. When the differential housing speed Nd is a first predetermined value N1 or higher (Nd≥N1), piezoelectric power generation control is performed to generate electricity based on the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d). Thus, when the differential housing speed Nd is a high-speed first predetermined value N1 or higher (Nd≥N1), electricity is generated based on the voltage output by the piezoelectric elements 50 (50a, 50b, 50c, 50d) due to the vibration generated in the bearing 40. The vibration generated in the bearing 40 is absorbed as generated electricity, thereby suppressing the vibration generated in the bearing 40.

[0035] Furthermore, according to the vibration suppression device 60 of this embodiment, when the differential housing speed Nd is greater than or equal to a second predetermined value N2 (Nd≥N2>N1) than the first predetermined value N1, piezoelectric displacement control is performed instead of piezoelectric power generation control: a specific phase SV of the vibration generated in the bearing 40 is determined based on the voltage Vpd output by the piezoelectric element 50, and power is applied to the piezoelectric element 50 disposed near the specific phase SV to generate a displacement in the direction of vibration suppression. Therefore, when the differential housing speed Nd rapidly becomes the allowable speed, i.e., the second predetermined value N2 or higher, and the vibration increases, the displacement in the direction of vibration cancellation generated by the piezoelectric element 50 is used to suppress the vibration generated in the bearing 40.

[0036] Furthermore, in the vibration suppression device 60 according to this embodiment, the piezoelectric element 50 is disposed between the outer diameter surface 40a of the bearing 40 and the housing 26. Thus, the effects described above can be obtained.

[0037] Furthermore, the vibration suppression device 60 according to this embodiment is similarly applicable to the bearing 42 on which the piezoelectric element 52 is disposed. Figure 6 The same effect as described above can be achieved by controlling the flowchart.

[0038] Next, another embodiment of the present invention will be described. Furthermore, in the following description, the same symbols are used to denote common parts of the embodiments, and the description is omitted.

[0039] [Example 2]

[0040] The vibration suppression device 80 is a device formed by adding piezoelectric elements 54 (54a, 54b, 54c, 54d) to the vibration suppression device 60 of Example 1, and includes a piezoelectric element control circuit (not shown), a battery, an electronic control device, etc., corresponding to the addition of the piezoelectric element 54. Figure 6 This is a diagram illustrating an example of the structure of the vibration suppression device 80, which is equivalent to the aforementioned Embodiment 1. Figure 3 The image.

[0041] Figure 6 (a) is a cross-sectional view of the piezoelectric elements 50 and 54 in the vibration suppression device 80, viewed vertically above the vehicle 10 with the axis CL as the center. Furthermore, Figure 6 (b) Viewed from the left side of the vehicle with the axle CL as the center. Figure 6 A schematic diagram of bearing 40 and piezoelectric element 50 in (a). Additionally, in Figure 6 In (a) and (b), the conductive lines connecting to the electrodes of piezoelectric element 50 and piezoelectric element 54 are omitted.

[0042] like Figure 6As shown in (a), the piezoelectric element 54 is positioned between the end face 40b on the left side of the bearing 40 and the housing 26, with the displacement direction parallel to the axis CL.

[0043] Next, using Figure 6 (b) The arrangement of piezoelectric elements 54 (54a, 54b, 54c, 54d) in the circumferential direction of bearing 40 will be described. Piezoelectric elements 54a and 54b constitute a pair on one side. Similar to piezoelectric element 50, piezoelectric element 54a is disposed on the end face 40b of phase A, and piezoelectric element 54b is disposed on the end face 40b of phase C, which is symmetrical about the axis CL with respect to piezoelectric element 54a. Similarly, piezoelectric elements 54c and 54d constitute a pair on the other side. Piezoelectric element 54c is disposed on the end face 40b of phase B, and piezoelectric element 54d is disposed on the end face 40b of phase D, which is symmetrical about the axis CL with respect to piezoelectric element 54a. Thus, a plurality of piezoelectric elements are provided, namely a pair of piezoelectric elements 54a and 54b on one side and piezoelectric elements 54c and 54d on the other side.

[0044] By adding piezoelectric elements 54 (54a, 54b, 54c, 54d), and by bearing the meshing reaction force KF (refer to the black filled arrow in the figure) between the final drive gear 24 and the differential ring gear 32a, etc., vibration is generated in the axial direction (axis CL direction) of the bearing 40, which is similarly applicable. Figure 6 The vibration was suppressed by controlling the flowchart.

[0045] As described above, in the vibration suppression device 80 according to this embodiment, the piezoelectric element 54 is disposed between the axial end face 40b of the bearing 40 and the housing 26. Therefore, for vibrations generated in the axial direction (axis CL direction) of the bearing 40, the same effect as in the aforementioned embodiment 1 can be obtained.

[0046] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is also applicable to other methods.

[0047] For example, in the aforementioned Embodiments 1 and 2, one of the pair of piezoelectric elements is positioned in the longitudinal direction of the vehicle 10, and the other is positioned in the vertical direction, but the orientation is not limited to this. Under the condition that the pair are symmetrically arranged about the axis CL, one and the other are respectively positioned in a direction suitable for vibration suppression.

[0048] Furthermore, in the aforementioned Embodiments 1 and 2, the configured piezoelectric elements are two pairs, one pair on one side and one pair on the other side, but are not limited to two pairs. Multiple suitable configurations are suitable for vibration suppression.

[0049] Furthermore, the above is only one embodiment, and the present invention can be implemented in various ways with modifications and improvements based on the knowledge of those skilled in the art.

[0050] Symbol Explanation

[0051] 10 - Vehicle, 26 - Housing, 30 - Differential assembly, 32 - Differential housing, 40, 42 - Bearing, 40a - Outer diameter surface, 40b - End face, 50, 52, 54 - Piezoelectric element, 60, 80 - Vibration damping device, CL - Shaft, N1 - First specified value, N2 - Second specified value, Nd - Differential housing speed (rotational speed), Vpd - Voltage, SV - Specific phase (maximum position).

Claims

1. A vibration suppression device for a vehicle that is provided with a differential device, a differential case of the differential device being supported to a non-rotating housing via a bearing, the vibration suppression device for a vehicle being characterized in that, the vibration suppression device is provided with a plurality of piezoelectric elements between the bearing and the housing, the piezoelectric elements being a pair of piezoelectric elements that are symmetrically arranged with respect to an axis of the bearing, in a case where a rotational speed of the differential case is a first prescribed value or more, piezoelectric power generation control is performed, the piezoelectric power generation control generating power in accordance with a voltage output by the piezoelectric elements.

2. The vibration suppression device for a vehicle according to claim 1, characterized in that, the vibration suppression device, in a case where the rotational speed of the differential case is a second prescribed value that is greater than the first prescribed value or more, performs, instead of the piezoelectric power generation control, piezoelectric displacement control that determines a maximum position of vibration generated at the bearing in accordance with the voltage output by the piezoelectric elements and applies power to the piezoelectric elements arranged in the vicinity of the maximum position to cause the piezoelectric elements to generate displacement in a direction that cancels the vibration.

3. The vibration suppression device for a vehicle according to claim 1 or 2, characterized in that, the piezoelectric elements are arranged between an outer diameter surface of the bearing and the housing.

4. The vibration suppression device for a vehicle according to claim 1 or 2, characterized in that, the piezoelectric elements are arranged between an end surface in an axial direction of the bearing and the housing.

Images