Acceleration reduction device

Abstract

The present invention provides an acceleration reduction device that can rotate two racks at approximately the same rotational speed. [Solution] The acceleration reduction device comprises a first rack having a plurality of first teeth arranged around a first central axis, a first pinion that meshes with the first teeth, a first drive device for rotating the first pinion, a second rack having a plurality of second teeth arranged around the first central axis, a second pinion that meshes with the second teeth, a second drive device for rotating the second pinion, and a first driver that inputs a common electrical signal to the first drive device and the second drive device, wherein the diameter of the pitch circle of the plurality of first teeth is different from the diameter of the pitch circle of the plurality of second teeth, and the reduction ratio of the first rack and the first pinion and the reduction ratio of the second rack and the second pinion are set so that the first rack and the second rack rotate in unison around the first central axis.

Description

Technical Field

[0001] The present invention relates to an acceleration reduction device.

Background Art

[0002] When a vehicle or a transport robot travels, an acceleration in the direction along the surface acts on a passenger on the seat surface of the vehicle seat or an object on the top surface of the table of the transport robot. Conventionally, research and development of an acceleration reduction device capable of reducing the acceleration have been carried out.

[0003] The acceleration reduction device causes a member such as a seat or a table having a surface on which a person or an object rides to perform a pendulum motion, for example, during acceleration or deceleration or when traveling on an inclined surface. Thereby, the acceleration reduction device can reduce the acceleration in the direction along the surface acting on the person or the object.

[0004] For example, a rack and pinion mechanism causes a member such as a seat or a table to perform a pendulum motion. That is, the rack and pinion mechanism has an arc-shaped rack connected to the member and a pinion that rotates the rack. For example, a driving device including a motor and a speed reducer rotates the pinion, so that the arc-shaped rack rotates.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] It is also conceivable that multiple rack-and-pinion mechanisms could be mounted together on a component such as a seat or table, and work together to cause the component to move like a pendulum. In this case, if the distance between the central axis of the pendulum motion and the multiple racks is the same, multiple drive units driven by a single driver can rotate the multiple racks at approximately the same rotational speed.

[0007] However, it is not always possible to arrange multiple racks so that the distance between each rack and the central axis of the pendulum motion is approximately the same. If the distance between the central axis of the pendulum motion and the multiple racks differs, the pitch circle diameters of the multiple racks will differ from each other, and the reduction ratios of the multiple rack-and-pinion mechanisms will also differ. In this case, it becomes difficult to rotate multiple racks at approximately the same rotational speed with a single driver. In other words, the arrangement of racks is limited in conventional configurations.

[0008] The present invention has been made in view of the above, and provides an acceleration reduction device that can rotate two racks at approximately the same rotational speed when a common electrical signal is input from one driver to two drive devices, even if the distance between the central axis and the two racks is different. [Means for solving the problem]

[0009] The acceleration reduction device according to the present invention comprises: a first rack having a plurality of first teeth arranged around a virtual first central axis; a first pinion that meshes with the plurality of first teeth; a first drive device configured to rotate the first pinion; a second rack having a plurality of second teeth arranged around the first central axis; a second pinion that meshes with the plurality of second teeth; a second drive device configured to rotate the second pinion; and a first driver that inputs a common electrical signal to the first drive device and the second drive device. The first and second racks are spaced apart from each other in the first axial direction along the first central axis, the diameter of the pitch circle of the plurality of first teeth is different from the diameter of the pitch circle of the plurality of second teeth, and the reduction ratio of the first rack and the first pinion and the reduction ratio of the second rack and the second pinion are set such that when the first driver inputs the electrical signal to the first drive unit and the second drive unit, the first rack and the second rack rotate in alignment with the first pinion and the second pinion around the first central axis. [Effects of the Invention]

[0010] According to the acceleration reduction device of the present invention, even if the distance between the first central axis and the first rack and the distance between the first central axis and the second rack are different, when a common electrical signal is input from one first driver to the first drive unit and the second drive unit, the first rack and the second rack can be rotated at approximately the same rotational speed. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic side view showing a part of a vehicle according to one embodiment. [Figure 2] Figure 2 is a perspective view showing the acceleration reduction device of the above embodiment. [Figure 3] Figure 3 is a side view showing the acceleration reduction device of the above embodiment. [Figure 4]Figure 4 is a perspective view showing the acceleration reduction device in which the second rotating mechanism of the above embodiment is rotated. [Figure 5] Figure 5 is a schematic front view showing the first rotation mechanism of the above embodiment. [Modes for carrying out the invention]

[0012] Below, an acceleration reduction device 10 according to one embodiment will be described with reference to Figures 1 to 5. Note that in this specification, the components of an embodiment and their descriptions may be described using multiple expressions. The components and their descriptions are examples and are not limited by the expressions used herein. Components may also be identified by names different from those used herein. Furthermore, components may also be described using expressions different from those used herein.

[0013] Figure 1 is a schematic side view showing a part of the vehicle 1 according to this embodiment. As shown in Figure 1, the acceleration reduction device 10 of this embodiment is mounted on a vehicle 1 such as an automobile. The acceleration reduction device 10 can reduce the longitudinal and lateral acceleration of the vehicle 1 acting on the occupants of the vehicle 1, for example. Note that the acceleration reduction device 10 is not limited to this example.

[0014] As shown in each drawing, the X, Y, and Z axes are defined herein for convenience. The X, Y, and Z axes are orthogonal to each other. The X axis extends in the left-right direction of vehicle 1. The Y axis extends in the front-rear direction of vehicle 1. The Z axis extends in the up-down direction of vehicle 1.

[0015] Furthermore, the X, Y, and Z directions are defined herein. The X direction is the direction along the X axis and includes the +X direction (right) indicated by the X-axis arrow and the -X direction (left) which is the opposite direction of the X-axis arrow. The Y direction is the direction along the Y axis and includes the +Y direction (forward) indicated by the Y-axis arrow and the -Y direction (backward) which is the opposite direction of the Y-axis arrow. The Z direction is the direction along the Z axis and includes the +Z direction (up) indicated by the Z-axis arrow and the -Z direction (downward) which is the opposite direction of the Z-axis arrow.

[0016] The acceleration reduction device 10 is not limited to the vehicle 1 and may be mounted on other devices such as an autonomous driving robot (autonomous mobile body). In this case, the acceleration reduction device 10 reduces the acceleration in the longitudinal and lateral directions acting on the object being transported by the autonomous driving robot.

[0017] As shown in FIG. 1, the vehicle 1 of the present embodiment includes an acceleration reduction device 10, a floor 11, and a seat 12. The acceleration reduction device 10 is provided between the floor 11 and the seat 12. Note that the acceleration reduction device 10 may be provided at other positions.

[0018] The floor 11 has a plurality of floor surfaces 11a, 11b, 11c. The floor surface 11a is located below the floor surfaces 11b, 11c. For example, the occupant of the vehicle 1 places their feet on the floor surface 11a. The floor surface 11b is located between the floor surface 11a and the floor surface 11c in the Y direction. The floor surface 11c is spaced apart from the floor surface 11a in the -Y direction and is located above the floor surfaces 11a, 11b. For example, luggage is placed on the floor surface 11c.

[0019] The vehicle 1 has, for example, a battery under the floor surface 11b. The floor 11 is formed such that the floor surface 11b is higher than the floor surface 11a in order to form a space for arranging the battery. Note that other components such as a propeller shaft or a drive shaft may be arranged under the floor surface 11b.

[0020] The seat 12 in the example of FIG. 1 is, for example, a rear seat. Note that the seat 12 is not limited to this example. The seat 12 has a seating surface 12a. For example, the occupant of the vehicle 1 sits on the seating surface 12a. The seating surface 12a faces generally in the +Z direction as a whole.

[0021] The acceleration reduction device 10 includes a first rotation mechanism 21, a second rotation mechanism 22, and an electronic control unit (ECU) 23. Note that the acceleration reduction device 10 may omit the second rotation mechanism 22.

[0022] The first rotating mechanism 21 is attached to the floor 11 and is interposed between the floor 11 and the second rotating mechanism 22. The second rotating mechanism 22 is attached to the seat 12 and is interposed between the seat 12 and the first rotating mechanism 21. Note that the positions of the first rotating mechanism 21 and the second rotating mechanism 22 are not limited to this example. For example, the second rotating mechanism 22 may be interposed between the floor 11 and the first rotating mechanism 21, and the first rotating mechanism 21 may be interposed between the seat 12 and the second rotating mechanism 22.

[0023] FIG. 2 is a perspective view showing the acceleration reduction device 10 of the present embodiment. FIG. 3 is a side view showing the acceleration reduction device 10 of the present embodiment. FIG. 4 is a perspective view showing the acceleration reduction device 10 in which the second rotating mechanism 22 of the present embodiment is rotated. FIG. 5 is a front view schematically showing the first rotating mechanism 21 of the present embodiment.

[0024] In the present embodiment, the first rotating mechanism 21 can cause the seat 12 to perform a pendulum motion approximately in the X direction (left - right direction). Specifically, the first rotating mechanism 21 can rotate the second rotating mechanism 22 and the seat 12 around the first central axis Ax1 shown in FIG. 5 with respect to the floor 11. The first central axis Ax1 is a virtual central axis of the rotation of the seat 12.

[0025] In the present embodiment, the first central axis Ax1 is located above the first rotating mechanism 21 and the second rotating mechanism 22 and extends substantially in the Y direction (front - rear direction of the vehicle 1). Note that the first central axis Ax1 may be located below the first rotating mechanism 21 and the second rotating mechanism 22, or may extend in other directions. For example, the first central axis Ax1 may extend substantially in the X direction (left - right direction of the vehicle 1). In this case, the first rotating mechanism 21 can cause the seat 12 to perform a pendulum motion approximately in the Y direction (front - rear direction).

[0026] On the other hand, the second rotation mechanism 22 can cause the seat 12 to move like a pendulum in approximately the Y direction (forward and backward direction). Specifically, the second rotation mechanism 22 can rotate the seat 12 relative to the first rotation mechanism 21 around the second central axis Ax2 shown in Figure 1. The second central axis Ax2 is the virtual central axis of rotation of the seat 12.

[0027] In this embodiment, the second central axis Ax2 is located above the second rotation mechanism 22 and extends substantially in the X direction. That is, the direction in which the second central axis Ax2 extends (the second axial direction) intersects (orthogonal in this embodiment) the direction along the first central axis Ax1 (the first axial direction).

[0028] The second central axis Ax2 may be located below the second rotating mechanism 22, or it may extend in other directions. For example, if the direction in which the second central axis Ax2 extends intersects with the direction along the first central axis Ax1, the second central axis Ax2 may extend approximately in the Y direction (the front-to-back direction of the vehicle 1). In this case, the second rotating mechanism 22 can cause the seat 12 to move like a pendulum in approximately the X direction (left-to-right direction). When the first rotating mechanism 21 rotates the second rotating mechanism 22, the second central axis Ax2 also rotates around the first central axis Ax1.

[0029] As shown in Figure 2, the first rotating mechanism 21 includes a base 31, a front actuator 32, and a rear actuator 33. The first rotating mechanism 21 is not limited to two actuators (front actuator 32 and rear actuator 33), but may have three or more actuators.

[0030] The base 31 includes a front support plate (first support part) 41, a plurality of front support rollers 42, a plurality of front guide rollers (first rollers) 43, and a rear support plate (second support part) 44 as shown in Figure 4, a plurality of rear support rollers 45 and a plurality of rear guide rollers (second rollers) 46 as shown in Figure 5, and a connecting member 47 as shown in Figure 4.

[0031] As shown in Figure 1, the front support plate 41 is attached to the floor surface 11a of the floor 11 so as to extend from the floor surface 11a in approximately the +Z direction. The front support plate 41 is formed in the shape of a plate, for example, positioned along the XZ plane. As shown in Figure 3, the front support plate 41 has a rear surface 41a. The rear surface 41a is formed to be approximately flat and faces approximately in the -Y direction.

[0032] As shown in Figure 2, multiple front support rollers 42 are attached to the front support plate 41. Each of the multiple front support rollers 42 is attached to a shaft that protrudes approximately in the -Y direction from the rear surface 41a of the front support plate 41.

[0033] Each front support roller 42 is rotatable around its central axis relative to the front support plate 41. The central axis of the front support roller 42 extends approximately in the Y direction. Each of the multiple front support rollers 42 has a bearing and can rotate smoothly. As shown in Figure 5, the multiple front support rollers 42 are arranged at intervals around a first central axis Ax1.

[0034] As shown in Figure 2, multiple front guide rollers 43 are attached to the front support plate 41. Each of the multiple front guide rollers 43 is fitted, for example, into a groove that penetrates the front support plate 41 in approximately the Y direction. As shown in Figure 3, a portion of the front guide rollers 43 protrudes from the rear surface 41a of the front support plate 41 in approximately the -Y direction.

[0035] Each front guide roller 43 is rotatable relative to the front support plate 41 around its central axis (third central axis) Axr, as shown in Figure 5. The central axis Axr extends radially perpendicular to the first central axis Ax1. Multiple front guide rollers 43 are arranged at intervals around the first central axis Ax1.

[0036] As shown in Figure 1, the rear support plate 44 is attached to the floor surface 11b of the floor 11 so as to extend from the floor surface 11b in approximately the +Z direction. That is, the rear support plate 44 is spaced approximately in the -Y direction from the front support plate 41. In other words, the front support plate 41 and the rear support plate 44 are spaced apart from each other in the direction along the first central axis Ax1 (the first axial direction).

[0037] The rear support plate 44 is formed in the shape of a plate, for example, positioned along the XZ plane. As shown in Figure 2, the rear support plate 44 has a front surface 44a. The front surface 44a is formed to be substantially flat and oriented substantially in the +Y direction.

[0038] Multiple rear support rollers 45 are attached to the rear support plate 44. Each of the multiple rear support rollers 45 is attached to a shaft that protrudes approximately in the +Y direction from the front surface 44a of the rear support plate 44.

[0039] Each rear support roller 45 is rotatable around its central axis relative to the rear support plate 44. The central axis of the rear support roller 45 extends approximately in the Y direction. Each of the multiple rear support rollers 45 has a bearing and can rotate smoothly. As shown in Figure 5, the multiple rear support rollers 45 are arranged at intervals around a first central axis Ax1.

[0040] As shown in Figure 4, multiple rear guide rollers 46 are attached to the rear support plate 44. Each of the multiple rear guide rollers 46 is fitted, for example, into a groove that penetrates the rear support plate 44 in approximately the Y direction. A portion of the rear guide rollers 46 protrudes from the front surface 44a of the rear support plate 44 in approximately the +Y direction.

[0041] Each rear guide roller 46 is rotatable around its central axis (fourth central axis) Axr relative to the rear support plate 44. As shown in Figure 5, the multiple rear guide rollers 46 are arranged around the first central axis Ax1.

[0042] As shown in Figure 2, the connecting member 47 extends in a substantially Y direction along the floor surface 11b of the floor 11. The connecting member 47 is attached to the front support plate 41 and the rear support plate 44. The connecting member 47 may also be attached to the floor surface 11b.

[0043] The front actuator 32 includes a first drive unit 51 and a first rack and pinion mechanism 52. The first drive unit 51 may also be referred to as, for example, a motor gearbox.

[0044] The first drive unit 51 is attached to the front support plate 41. That is, the front support plate 41 supports the first drive unit 51. The first drive unit 51 includes, for example, a motor 51a and a reduction gear 51b as shown in Figure 2, and an output shaft 51c as shown in Figure 5.

[0045] Motor 51a is, for example, a DC motor. However, motor 51a may be of other types. The reduction gear 51b reduces the rotation of the motor 51a's shaft and transmits it to the output shaft 51c. The output shaft 51c protrudes from the reduction gear 51b in approximately the -Y direction. The output shaft 51c protrudes from the rear surface 41a of the front support plate 41, for example, by passing through a hole provided in the front support plate 41.

[0046] The first drive unit 51 rotates the output shaft 51c relative to the front support plate 41 around the central axis Axm1 of the output shaft 51c. The central axis Axm1 extends in the Y direction. That is, the central axis Axm1 extends in the direction in which the first central axis Ax1 extends (the first axial direction).

[0047] The first drive unit 51 drives the first rack and pinion mechanism 52 by rotating the output shaft 51c. The first rack and pinion mechanism 52 has a first rack 55 and a first pinion 56.

[0048] As shown in Figure 2, the first rack 55 is located between the front support plate 41 and the rear support plate 44. The first rack 55 may be provided in other locations. The first rack 55 is formed in the shape of a plate, for example, arranged along the XZ plane. The first rack 55 has a front surface 55a, a lower edge 55b, and a plurality of first teeth 55c.

[0049] The front surface 55a is formed to be substantially flat and faces approximately in the +Y direction. As shown in Figure 3, the front surface 55a of the first rack 55 and the rear surface 41a of the front support plate 41 face each other with a gap between them. In this embodiment, the front surface 55a is spaced apart from the front guide rollers 43. However, the multiple front guide rollers 43 may be in constant contact with the front surface 55a.

[0050] As shown in Figure 5, the lower edge 55b is provided at the end of the first rack 55 on the radially outer side. The lower edge 55b extends in an arc shape around the first central axis Ax1. In this embodiment, the lower edge 55b as a whole is oriented approximately in the -Z direction.

[0051] Each of the multiple first teeth 55c protrudes radially outward from the lower edge 55b. That is, the multiple first teeth 55c protrude approximately in the -Z direction (downward) from the lower edge 55b. The multiple first teeth 55c are arranged around the first central axis Ax1. The lower edge 55b forms the tooth roots of the multiple first teeth 55c.

[0052] A groove 58 is provided in the first rack 55. The groove 58 is recessed in the direction approximately -Y from the front surface 55a of the first rack 55 and extends in an arc shape around the first central axis Ax1. The groove 58 may also penetrate the first rack 55 in the direction approximately Y.

[0053] Multiple front support rollers 42 are housed in the groove 58. The front support rollers 42 can support the first rack 55 by contacting the inner surface of the first rack 55 that defines the groove 58. Since the multiple front support rollers 42 are arranged around the first central axis Ax1 and the groove 58 extends around the first central axis Ax1, the first rack 55 can rotate around the first central axis Ax1 relative to the base 31.

[0054] The first pinion 56 is attached to the output shaft 51c of the first drive unit 51. Therefore, the central axis Axm1 of the output shaft 51c is also the central axis of the first pinion 56. The first drive unit 51 rotates the output shaft 51c, thereby rotating the first pinion 56 around the central axis Axm1 of the output shaft 51c.

[0055] The first pinion 56 has an outer circumferential surface 56a and a plurality of pinion teeth 56b. The outer circumferential surface 56a is a substantially cylindrical curved surface that extends along the central axis Axm1 of the output shaft 51c. The plurality of pinion teeth 56b protrude from the outer circumferential surface 56a so as to be aligned around the central axis Axm1. The outer circumferential surface 56a forms the tooth roots of the plurality of pinion teeth 56b.

[0056] In this embodiment, the first pinion 56 is located below the first rack 55. Multiple pinion teeth 56b of the first pinion 56 mesh with multiple first teeth 55c of the first rack 55. Therefore, when the first drive unit 51 rotates the output shaft 51c, the first pinion 56 rotates, and the first rack 55 rotates (oscillates) around the first central axis Ax1 relative to the first pinion 56. The first pinion 56 may be positioned above the first rack 55 or at other positions, depending on the direction in which the first teeth 55c face.

[0057] As shown in Figure 3, the rear actuator 33 has a second drive unit 61 and a second rack and pinion mechanism 62. The second drive unit 61 may also be referred to as, for example, a motor gearbox.

[0058] The second drive unit 61 is attached to the rear support plate 44. That is, the rear support plate 44 supports the second drive unit 61. The second drive unit 61 has, for example, a motor 61a and a reduction gear 61b as shown in Figure 3, and an output shaft 61c as shown in Figure 5.

[0059] Motor 61a is, for example, the same DC motor as motor 51a of the first drive unit 51. The reduction gear 61b is, for example, the same reduction gear as reduction gear 51b of the first drive unit 51. Note that motor 61a and reduction gear 61b are not limited to this example.

[0060] The reduction gear 61b reduces the rotation of the motor 61a shaft and transmits it to the output shaft 61c. The output shaft 61c protrudes from the reduction gear 61b in approximately the +Y direction. The output shaft 61c passes through a hole provided in the rear support plate 44, for example, and protrudes from the front surface 44a of the rear support plate 44.

[0061] The second drive unit 61 rotates the output shaft 61c around its central axis Axm2 relative to the rear support plate 44. As shown in Figure 5, the central axis Axm2 extends in the Y direction. That is, the central axis Axm2 extends in the direction in which the first central axis Ax1 extends (the first axial direction).

[0062] The second drive unit 61 drives the second rack and pinion mechanism 62 by rotating the output shaft 61c. The second rack and pinion mechanism 62 includes a second rack 65 and a second pinion 66.

[0063] As shown in Figure 2, the second rack 65 is located between the front support plate 41 and the rear support plate 44. The second rack 65 may be provided in other locations. The second rack 65 is spaced apart from the first rack 55 in the -Y direction. That is, the first rack 55 and the second rack 65 are spaced apart from each other in the direction along the first central axis Ax1 (the first axial direction). Also, since the first central axis Ax1 extends in the Y direction (front-rear direction), the first rack 55 and the second rack 65 are spaced apart from each other in the horizontal direction.

[0064] The second rack 65 is formed, for example, as a plate that is arranged along the XZ plane. The second rack 65 has a rear surface 65a as shown in Figure 3, an upper edge 65b as shown in Figure 5, and a plurality of second teeth 65c.

[0065] As shown in Figure 3, the rear surface 65a is formed to be substantially flat and faces approximately in the -Y direction. The rear surface 65a of the second rack 65 and the front surface 44a of the rear support plate 44 face each other with a gap between them. In this embodiment, the rear surface 65a is spaced apart from the rear guide rollers 46. However, the multiple rear guide rollers 46 may be in constant contact with the rear surface 65a.

[0066] As shown in Figure 5, the upper edge 65b is provided at the end of the second rack 65 on the radially inward side. The upper edge 65b extends in an arc shape around the first central axis Ax1. In this embodiment, the upper edge 65b as a whole is oriented approximately in the +Z direction.

[0067] Each of the multiple second teeth 65c protrudes radially inward from the upper edge 65b. That is, the multiple second teeth 65c protrude approximately in the +Z direction (upward) from the upper edge 65b. The multiple second teeth 65c are arranged around the first central axis Ax1. The upper edge 65b forms the tooth roots of the multiple second teeth 65c.

[0068] A groove 68 is provided in the second rack 65. The groove 68 is recessed in the direction approximately +Y from the rear surface 65a of the second rack 65 and extends in an arc shape around the first central axis Ax1. The groove 68 may also penetrate the second rack 65 in the direction approximately Y.

[0069] Multiple rear support rollers 45 are housed in the groove 68. The rear support rollers 45 can support the second rack 65 by contacting the inner surface of the second rack 65 that defines the groove 68. Since the multiple rear support rollers 45 are arranged around the first central axis Ax1 and the groove 68 extends around the first central axis Ax1, the second rack 65 can rotate around the first central axis Ax1 relative to the base 31.

[0070] The second pinion 66 is attached to the output shaft 61c of the second drive unit 61. Therefore, the central axis Axm2 of the output shaft 61c is also the central axis of the second pinion 66. The second drive unit 61 rotates the output shaft 61c, thereby rotating the second pinion 66 around the central axis Axm2 of the output shaft 61c.

[0071] The second pinion 66 has an outer circumferential surface 66a and a plurality of pinion teeth 66b. The outer circumferential surface 66a is a substantially cylindrical curved surface that extends along the central axis Axm2 of the output shaft 61c. The plurality of pinion teeth 66b protrude from the outer circumferential surface 66a so as to be aligned around the central axis Axm2. The outer circumferential surface 66a forms the tooth roots of the plurality of pinion teeth 66b.

[0072] In this embodiment, the second pinion 66 is located above the second rack 65. Multiple pinion teeth 66b of the second pinion 66 mesh with multiple second teeth 65c of the second rack 65. Therefore, when the second drive unit 61 rotates the output shaft 61c, the second pinion 66 rotates, and the second rack 65 rotates (oscillates) around the first central axis Ax1 relative to the second pinion 66. The second pinion 66 may be positioned below the second rack 65 or at other positions, depending on the direction in which the second teeth 65c face.

[0073] Furthermore, in this embodiment, the central axis Axm1 of the output shaft 51c of the first drive unit 51 and the central axis Axm2 of the output shaft 61c of the second drive unit 61 are located below the first central axis Ax1. The central axis Axm2 is located in a straight line connecting the first central axis Ax1 and the central axis Axm1. That is, the first central axis Ax1, the central axis Axm1, and the central axis Axm2 are aligned in a straight line in the radial direction. Note that the central axes Axm1 and Axm2 may be positioned at other locations.

[0074] The multiple first teeth 55c of the first rack 55 and the multiple second teeth 65c of the second rack 65 are all aligned around the first central axis Ax1. However, the diameter of the pitch circle Pc1 of the multiple first teeth 55c is different from the diameter of the pitch circle Pc2 of the multiple second teeth 65c.

[0075] In this embodiment, the first rack 55 is located below the second rack 65. Therefore, the multiple first teeth 55c of the first rack 55 are spaced further apart from the first central axis Ax1 than the multiple second teeth 65c of the second rack 65. That is, the diameter of the pitch circle Pc1 is larger than the diameter of the pitch circle Pc2.

[0076] The reduction ratio i1 of the first rack and pinion mechanism 52 and the reduction ratio i2 of the second rack and pinion mechanism 62 are set to be approximately equal. Specifically, the difference between the reduction ratio i1 of the first rack 55 and the first pinion 56 and the reduction ratio i2 of the second rack 65 and the second pinion 66 should be set to 1% or less of the reduction ratio i1. However, the difference between the reduction ratio i1 and the reduction ratio i2 may be 1% or more.

[0077] For example, in the calculation of the reduction ratio i1, the number of teeth of the multiple first teeth 55c of the first rack 55 is 689. Note that the number of teeth of the multiple first teeth 55c in the calculation of the reduction ratio i1 is not the actual number of teeth of the first teeth 55c, but the number of teeth of the first teeth 55c when the multiple first teeth 55c are arranged 360° around the first central axis Ax1. The number of teeth of the first teeth 55c can be calculated, for example, based on the diameter of the pitch circle Pc1 and the pitch of the multiple first teeth 55c.

[0078] The first pinion 56 has 20 teeth on its multiple pinion teeth 56b. Therefore, the reduction ratio i1 of the first rack 55 and the first pinion 56 is 34.45 (34.45:1).

[0079] In calculating the reduction ratio i2, the number of teeth of the multiple second teeth 65c of the second rack 65 is 585. Note that the number of teeth of the multiple second teeth 65c in the calculation of the reduction ratio i2 is not the actual number of teeth of the second teeth 65c, but the number of teeth of the second teeth 65c when the multiple second teeth 65c are arranged 360° around the first central axis Ax1. The number of teeth of the second teeth 65c can be calculated, for example, based on the diameter of the pitch circle Pc2 and the pitch of the multiple second teeth 65c.

[0080] The second pinion 66 has 17 teeth on its multiple pinion teeth 66b. Therefore, the reduction ratio i2 of the second rack 65 and the second pinion 66 is approximately 34.41 (34.41:1).

[0081] The difference between reduction ratio i1 and reduction ratio i2 is approximately 0.04. On the other hand, 1% of reduction ratio i1 is approximately 0.34. As described above, the difference between reduction ratio i1 and reduction ratio i2 is less than 1% of reduction ratio i1. Note that the number of teeth of the multiple first teeth 55c, the number of teeth of the multiple pinion teeth 56b, the number of teeth of the multiple second teeth 65c, the number of teeth of the multiple pinion teeth 66b, reduction ratio i1, and reduction ratio i2 described above are merely examples and do not limit the number of teeth and reduction ratios.

[0082] As shown in Figure 4, the second rotation mechanism 22 includes a seat base 71, a right actuator 72, and a left actuator 73. The second rotation mechanism 22 is not limited to two actuators (right actuator 72 and left actuator 73), but may have three or more actuators.

[0083] The seat base 71 includes a base frame 81, a plurality of support rollers 82, and a seat frame 83.

[0084] The base frame 81 is provided between the first rack 55 and the second rack 65 and is connected to the first rack 55 and the second rack 65. In other words, the base frame 81 is attached to the first rotating mechanism 21.

[0085] Each support roller 82 is mounted on the base frame 81 so as to be rotatable around its central axis. The central axis of the support roller 82 extends in the direction along the second central axis Ax2 (the second axial direction). The multiple support rollers 82 have bearings and can rotate smoothly. The multiple support rollers 82 are arranged around the second central axis Ax2.

[0086] The seat frame 83 includes a right rail 85, a left rail 86, a plurality of beams 87, and a wire frame 88. The right rail 85 and the left rail 86 are each formed in a plate shape and arranged to be approximately perpendicular to the direction along the second central axis Ax2 (the second axial direction). The right rail 85 is spaced approximately in the +X direction from the left rail 86. That is, the right rail 85 and the left rail 86 are spaced apart from each other in the direction along the second central axis Ax2 (the second axial direction).

[0087] Multiple beams 87 each connect the right rail 85 and the left rail 86. The wire frame 88 is attached to the right rail 85 and the left rail 86 and coupled to the seat 12. The wire frame 88 holds, for example, the cushion of the seat 12.

[0088] A groove 89 is provided in both the right rail 85 and the left rail 86. The groove 89 extends around a second central axis Ax2. Multiple support rollers 82 are housed in each of the two grooves 89.

[0089] Multiple support rollers 82 can support the right rail 85 and the left rail 86 by contacting the inner surface that defines the groove 89. Since the multiple support rollers 82 are arranged around the second central axis Ax2 and the groove 89 extends around the second central axis Ax2, the right rail 85 and the left rail 86 can rotate around the second central axis Ax2 relative to the base frame 81.

[0090] The light actuator 72 includes a third drive unit 91 and a third rack and pinion mechanism 92. The third drive unit 91 may also be referred to as, for example, a motor gearbox.

[0091] The third drive unit 91 is attached to the light rail 85. The third drive unit 91 includes, for example, a motor, a reduction gear, and an output shaft. The reduction gear transmits the rotation of the motor shaft to the output shaft.

[0092] The third drive unit 91 drives the third rack and pinion mechanism 92 by rotating its output shaft. The third rack and pinion mechanism 92 includes a third rack 95 and a third pinion 96.

[0093] The third rack 95 is attached to the base frame 81. The third rack 95 is located between the right rail 85 and the left rail 86. The third rack 95 may be provided in other locations. The third rack 95 is formed in a plate shape, for example, arranged perpendicular to the direction along the second central axis Ax2 (the second axial direction). The third rack 95 has an upper edge 95a and a plurality of third teeth 95b.

[0094] The upper edge 95a extends in an arc shape around the second central axis Ax2 and is oriented toward the second central axis Ax2. In this embodiment, the upper edge 95a as a whole is oriented approximately in the +Z direction. Each of the multiple third teeth 95b protrudes from the upper edge 95a toward the second central axis Ax2. That is, the multiple third teeth 95b protrude from the upper edge 95a approximately in the +Z direction (upward). The multiple third teeth 95b are arranged around the second central axis Ax2. The upper edge 95a forms the tooth roots of the multiple third teeth 95b.

[0095] The third pinion 96 is attached to the output shaft of the third drive unit 91. The third drive unit 91 rotates the third pinion 96 around its central axis. The central axis of the third pinion 96 extends in the direction along the second central axis Ax2 (the second axial direction).

[0096] In this embodiment, the third pinion 96 is positioned above the third rack 95. Multiple teeth of the third pinion 96 mesh with multiple third teeth 95b of the third rack 95. Therefore, when the third drive unit 91 rotates the third pinion 96, the third rack 95 rotates (oscillates) around the second central axis Ax2 relative to the third pinion 96. The third pinion 96 may be positioned below the third rack 95 or at other positions, depending on the direction in which the third teeth 95b face.

[0097] The left actuator 73 includes a fourth drive unit 101 and a fourth rack and pinion mechanism 102. The fourth drive unit 101 may also be referred to as, for example, a motor gearbox.

[0098] The fourth drive unit 101 is mounted on the left rail 86. The fourth drive unit 101 has, for example, a motor, a reduction gear, and an output shaft. The motor and reduction gear of the fourth drive unit 101 are the same as those of the third drive unit 91. Note that the fourth drive unit 101 is not limited to this example.

[0099] The fourth drive unit 101 drives the fourth rack and pinion mechanism 102 by rotating the output shaft of the fourth drive unit 101. The fourth rack and pinion mechanism 102 includes a fourth rack 105 and a fourth pinion 106.

[0100] The fourth rack 105 is attached to the base frame 81. Also, as described above, the third rack 95 is attached to the base frame 81. That is, the first rotating mechanism 21 is attached to the second rotating mechanism 22. When the first rack 55 and the second rack 65 rotate around the first central axis Ax1 relative to the base 31, the second rotating mechanism 22 also rotates around the first central axis Ax1 relative to the base 31.

[0101] The fourth rack 105 is located between the right rail 85 and the left rail 86. The fourth rack 105 may be located at other positions. The fourth rack 105 is spaced apart from the third rack 95 in the -X direction. That is, the third rack 95 and the fourth rack 105 are spaced apart in the direction along the second central axis Ax2 (the second axial direction). Furthermore, since the second central axis Ax2 extends approximately in the X direction (left-right direction), the third rack 95 and the fourth rack 105 are spaced apart in the horizontal direction.

[0102] The fourth rack 105 is formed in a plate shape, for example, arranged perpendicular to the direction along the second central axis Ax2 (the second axial direction). The fourth rack 105 has an upper edge 105a and a plurality of fourth teeth 105b.

[0103] The upper edge 105a extends in an arc shape around the second central axis Ax2 and is oriented toward the second central axis Ax2. In this embodiment, the upper edge 105a as a whole is oriented approximately in the +Z direction. Each of the multiple fourth teeth 105b protrudes from the upper edge 105a toward the second central axis Ax2. That is, the multiple fourth teeth 105b protrude from the upper edge 105a approximately in the +Z direction (upward). The multiple fourth teeth 105b are arranged around the second central axis Ax2. The upper edge 105a forms the tooth roots of the multiple fourth teeth 105b.

[0104] The fourth pinion 106 is mounted on the output shaft of the fourth drive unit 101. The fourth drive unit 101 rotates the fourth pinion 106 around its central axis. The central axis of the fourth pinion 106 extends in the direction along the second central axis Ax2 (the second axial direction).

[0105] In this embodiment, the fourth pinion 106 is located above the fourth rack 105. The multiple teeth of the fourth pinion 106 mesh with the multiple fourth teeth 105b of the fourth rack 105. Therefore, when the fourth drive unit 101 rotates the fourth pinion 106, the fourth rack 105 rotates (oscillates) around the second central axis Ax2 relative to the fourth pinion 106. The fourth pinion 106 may be positioned below the fourth rack 105 or at other positions, depending on the direction in which the fourth teeth 105b face.

[0106] In this embodiment, the diameter of the pitch circle of the plurality of third teeth 95b is equal to the diameter of the pitch circle of the plurality of fourth teeth 105b. Furthermore, the reduction ratio of the third rack 95 and the third pinion 96 is approximately equal to the reduction ratio of the fourth rack 105 and the fourth pinion 106.

[0107] As a variation, the diameters of the pitch circles of the multiple third teeth 95b and the diameters of the pitch circles of the multiple fourth teeth 105b may be different from each other. In this case, the difference between the reduction ratio of the third rack 95 and the third pinion 96 and the reduction ratio of the fourth rack 105 and the fourth pinion 106 should be set to 1% or less of the reduction ratio of the third rack 95 and the third pinion 96. However, the difference between the reduction ratio of the third rack 95 and the third pinion 96 and the reduction ratio of the fourth rack 105 and the fourth pinion 106 may be 1% or more.

[0108] As shown in Figure 1, the ECU23 has a first driver 111 and a second driver 112. The ECU23 further includes a processing unit such as a CPU, memory such as ROM and RAM, and an accelerometer. The processing unit controls the first driver 111 and the second driver 112 based on a program read from memory, for example.

[0109] The motor 51a of the first drive unit 51 and the motor 61a of the second drive unit 61 are connected in parallel to the first driver 111. Therefore, the first driver 111 inputs a common electrical signal to the motor 51a of the first drive unit 51 and the motor 61a of the second drive unit 61. For example, the first driver 111 inputs a common voltage (voltage signal) to the motor 51a of the first drive unit 51 and the motor 61a of the second drive unit 61.

[0110] The motors of the third drive unit 91 and the fourth drive unit 101 are connected in parallel to the second driver 112. Therefore, the second driver 112 inputs a common electrical signal to the motors of the third drive unit 91 and the fourth drive unit 101. For example, the second driver 112 inputs a common voltage (voltage signal) to the motors of the third drive unit 91 and the fourth drive unit 101.

[0111] For example, the ECU23 obtains the acceleration acting on the vehicle 1 from an acceleration sensor. Depending on the acceleration in the X direction acting on the vehicle 1, the ECU23 inputs a common voltage from the first driver 111 to the motor 51a of the first drive unit 51 and the motor 61a of the second drive unit 61.

[0112] The first drive unit 51 is driven by the input voltage and rotates the first pinion 56. This causes the first rack 55 to rotate around the first central axis Ax1. Furthermore, the second drive unit 61 is driven by the input voltage and rotates the second pinion 66. This causes the second rack 65 to rotate around the first central axis Ax1.

[0113] The motor 51a of the first drive unit 51 and the motor 61a of the second drive unit 61 are the same motor. Also, the reduction gear 51b of the first drive unit 51 and the reduction gear 61b of the second drive unit 61 are the same reduction gear. Furthermore, a common voltage is input to both the first drive unit 51 and the second drive unit 61. Therefore, the rotational speed of the first pinion 56 driven by the first drive unit 51 and the rotational speed of the second pinion 66 driven by the second drive unit 61 are approximately the same.

[0114] The reduction ratio i1 of the first rack 55 and the first pinion 56 is approximately equal to the reduction ratio i2 of the second rack 65 and the second pinion 66. Therefore, the rotational speed of the first rack 55 and the rotational speed of the second rack 65 are approximately the same. Consequently, the first rack 55 and the second rack 65 can rotate together around the first central axis Ax1. In other words, the first rack 55 and the second rack 65 can rotate parallel to each other around the first central axis Ax1, preventing them from twisting.

[0115] For example, when the first drive unit 51 and the second drive unit 61 are started, the load acting on the first drive unit 51 may be different from the load acting on the second drive unit 61. In this case, the rotational speed of the first pinion 56 and the rotational speed of the second pinion 66 will be different. As a result, the rotational speed of the first rack 55 will be different from that of the second rack 65, and the first rack 55 and the second rack 65 will be tilted at an angle with respect to the first central axis Ax1.

[0116] When the first rack 55 tilts, a portion of the first rack 55 approaches the front support plate 41. In this case, the front guide roller 43 contacts the front surface 55a of the first rack 55, supporting the first rack 55.

[0117] The front guide roller 43 contacts the first rack 55, which rotates around the first central axis Ax1, thereby restricting the first rack 55 from approaching the front support plate 41, and also rolls on the front surface 55a of the first rack 55. The front guide roller 43 keeps the first rack 55 and the front support plate 41 separated from each other, and allows the first rack 55 to rotate smoothly around the first central axis Ax1.

[0118] Furthermore, when the second rack 65 tilts, a portion of the second rack 65 approaches the rear support plate 44. In this case, the rear guide roller 46 contacts the rear surface 65a of the second rack 65, supporting the second rack 65.

[0119] The rear guide roller 46 contacts the second rack 65, which rotates around the first central axis Ax1, thereby restricting the second rack 65 from approaching the rear support plate 44, and rolling on the rear surface 65a of the second rack 65. The rear guide roller 46 keeps the second rack 65 and the rear support plate 44 separated from each other, and allows the second rack 65 to rotate smoothly around the first central axis Ax1.

[0120] As the first rack 55 and the second rack 65 continue to rotate around the first central axis Ax1, the load acting on the first drive unit 51 and the second drive unit 61 becomes approximately equal over time. As a result, the rotational speed of the first rack 55 and the rotational speed of the second rack 65 become approximately the same, and the tilt of the first rack 55 and the second rack 65 is eliminated. However, the first rack 55 and the second rack 65 may remain tilted with respect to the first central axis Ax1.

[0121] The ECU 23 drives the first drive unit 51 and the second drive unit 61 in response to the acceleration in the X direction acting on the vehicle 1, thereby rotating the first rack 55 and the second rack 65 to a desired angle around the first central axis Ax1. As a result, the second rotation mechanism 22 and the seat 12 also rotate around the first central axis Ax1.

[0122] As the seat 12 rotates, the seat surface 12a tilts. As a result, the acceleration in the X direction acting on the occupant on the seat surface 12a is distributed between acceleration along the seat surface 12a and acceleration perpendicular to the seat surface 12a. Therefore, the acceleration acting on the occupant on the seat surface 12a along the seat surface 12a is reduced, and the acceleration in the X direction felt by the occupant is reduced.

[0123] Furthermore, the ECU 23 inputs a common voltage from the second driver 112 to the motor of the third drive unit 91 and the motor of the fourth drive unit 101, in accordance with the acceleration in the Y direction acting on the vehicle 1.

[0124] The third drive unit 91 is driven by the input voltage and rotates the third pinion 96. This causes the third rack 95 to rotate around the second central axis Ax2. Furthermore, the fourth drive unit 101 is driven by the input voltage and rotates the fourth pinion 106. This causes the fourth rack 105 to rotate around the second central axis Ax2.

[0125] The motor of the third drive unit 91 and the motor of the fourth drive unit 101 are the same motor. Also, the reduction gear of the third drive unit 91 and the reduction gear of the fourth drive unit 101 are the same reduction gear. Furthermore, a common voltage is input to both the third drive unit 91 and the fourth drive unit 101. Therefore, the rotational speed of the third pinion 96 driven by the third drive unit 91 and the rotational speed of the fourth pinion 106 driven by the fourth drive unit 101 are approximately the same.

[0126] The reduction ratio of the third rack 95 and the third pinion 96 is approximately equal to the reduction ratio of the fourth rack 105 and the fourth pinion 106. Therefore, the rotational speed of the third rack 95 and the rotational speed of the fourth rack 105 are approximately the same. Consequently, the third rack 95 and the fourth rack 105 can rotate in unison around the second central axis Ax2. In other words, the third rack 95 and the fourth rack 105 can rotate parallel to each other around the second central axis Ax2, preventing them from twisting.

[0127] The ECU 23 drives the third drive unit 91 and the fourth drive unit 101 in response to the acceleration in the Y direction acting on the vehicle 1, thereby rotating the third rack 95 and the fourth rack 105 to a desired angle around the second central axis Ax2. As a result, the seat 12 also rotates around the second central axis Ax2.

[0128] As the seat 12 rotates, the seat surface 12a tilts. As a result, the Y-direction acceleration acting on the occupant on the seat surface 12a is distributed between acceleration along the seat surface 12a and acceleration perpendicular to the seat surface 12a. Therefore, the acceleration acting on the occupant on the seat surface 12a along the seat surface 12a is reduced, and the Y-direction acceleration felt by the occupant is reduced.

[0129] In the vehicle 1 according to the embodiment described above, the acceleration reduction device 10 comprises a first rack 55, a first pinion 56, a first drive device 51, a second rack 65, a second pinion 66, a second drive device 61, and a first driver 111. The first rack 55 has a plurality of first teeth 55c arranged around a virtual first central axis Ax1. The first pinion 56 meshes with the plurality of first teeth 55c. The first drive device 51 is configured to rotate the first pinion 56. The second rack 65 has a plurality of second teeth 65c arranged around the first central axis Ax1. The second pinion 66 meshes with the plurality of second teeth 65c. The second drive device 61 is configured to rotate the second pinion 66. The first driver 111 inputs a common electrical signal to the first drive unit 51 and the second drive unit 61. The first rack 55 and the second rack 65 are spaced apart from each other in the first axial direction along the first central axis Ax1. The diameter of the pitch circle Pc1 of the multiple first teeth 55c is different from the diameter of the pitch circle Pc2 of the multiple second teeth 65c. The reduction ratio i1 of the first rack 55 and the first pinion 56, and the reduction ratio i2 of the second rack 65 and the second pinion 66 are set so that when the first driver 111 inputs an electrical signal to the first drive unit 51 and the second drive unit 61, the first rack 55 and the second rack 65 rotate in alignment with the first pinion 56 and the second pinion 66 around the first central axis Ax1.

[0130] With the above configuration, a single first driver 111 inputs a common electrical signal to the first drive unit 51 and the second drive unit 61, allowing the first rack 55 and the second rack 65 to rotate around the first central axis Ax1 at approximately the same rotational speed. As a result, when a member such as a sheet 12 or a table is attached to the first rack 55 and the second rack 65, the member can rotate around the first central axis Ax1 without twisting. Furthermore, since the acceleration reduction device 10 can drive two rack and pinion mechanisms with different pitch circle diameters at approximately the same rotational speed as described above, the degree of freedom (flexibility) of the layout of various parts can be improved. In addition, compared to the case where the first rack 55 and the second rack 65 are driven by separate drivers, the acceleration reduction device 10 can drive the first drive unit 51 and the second drive unit 61 with a single first driver 111, which in turn reduces costs and allows for miniaturization.

[0131] The first rack 55 and the second rack 65 are spaced apart from each other in the horizontal direction. The first pinion 56 is located above or below the first rack 55. The second pinion 66 is located above or below the second rack 65.

[0132] With the above configuration, the first rack 55 and the first pinion 56 are not aligned horizontally, nor are the second rack 65 and the second pinion 66 aligned horizontally. Therefore, the acceleration reduction device 10 can be made smaller in the horizontal direction compared to the case where the rack and pinion are aligned horizontally.

[0133] The first rack 55 is located below the second rack 65. The first pinion 56 is located below the first rack 55.

[0134] According to the above configuration, the first rack 55 is located lower than the second rack 65, and is therefore more susceptible to being covered in liquids, such as those spilled or splashed by the occupants of the vehicle 1, than the second rack 65. However, because the first pinion 56 is located below the first rack 55, the multiple first teeth 55c protrude approximately downward. Therefore, if the first rack 55 is covered in liquid, the liquid can be drained by gravity through the gaps between the multiple first teeth 55c.

[0135] The acceleration reduction device 10 comprises a first rotating mechanism 21, a second rotating mechanism 22, and a second driver 112. The first rotating mechanism 21 has a first rack 55, a first pinion 56, a first drive unit 51, a second rack 65, a second pinion 66, and a second drive unit 61. The second rotating mechanism 22 has a third rack 95, a third pinion 96, a third drive unit 91, a fourth rack 105, a fourth pinion 106, and a fourth drive unit 101. The third rack 95 has a plurality of third teeth 95b arranged around a virtual second central axis Ax2 and meshing with the third pinion 96. The third drive unit 91 is configured to rotate the third pinion 96. The fourth rack 105 has multiple fourth teeth 105b arranged around the second central axis Ax2 and meshing with the fourth pinion 106. The fourth drive unit 101 is configured to rotate the fourth pinion 106. The second driver 112 inputs a common electrical signal to the third drive unit 91 and the fourth drive unit 101. The second central axis Ax2 extends in a second axial direction intersecting the first axial direction. The third rack 95 and the fourth rack 105 are spaced apart from each other in the second axial direction. The first rotating mechanism 21 is attached to the second rotating mechanism.

[0136] With the above configuration, the combination of two rotating mechanisms (the first rotating mechanism 21 and the second rotating mechanism 22) allows the acceleration reduction device 10 to rotate a member such as a seat 12 around two axes, thereby more reliably reducing the acceleration acting on a person (occupant) or object on the member. Furthermore, at least one of the two rotating mechanisms (the first rotating mechanism 21) can drive two rack and pinion mechanisms with different rack pitch circle diameters at approximately the same rotational speed as described above, thereby improving the degree of freedom (flexibility) of the layout of various parts.

[0137] The acceleration reduction device 10 further comprises a front support plate 41, a front guide roller 43, a rear support plate 44, and a rear guide roller 46. The front support plate 41 supports the first drive unit 51. The front guide roller 43 is mounted on the front support plate 41 so as to be rotatable about a central axis Axr that extends radially perpendicular to the first central axis Ax1, and is configured to contact a first rack 55 that rotates about the first central axis Ax1, thereby restricting the first rack 55 from approaching the front support plate 41, and rolling on the front surface 55a of the first rack 55. The rear support plate 44 supports the second drive unit 61. The rear guide roller 46 is mounted on the rear support plate 44 so as to be rotatable around a central axis Axr that extends radially perpendicular to the first central axis Ax1, and is configured to contact a second rack 65 that rotates around the first central axis Ax1, thereby restricting the second rack 65 from approaching the rear support plate 44, and rolling on the rear surface 65a of the second rack 65.

[0138] With the above configuration, for example, if the load acting on the first drive unit 51 is different from the load acting on the second drive unit 61, the rotational speed of the first rack 55 may differ from the rotational speed of the second rack 65. In this case, the first rack 55 and the second rack 65 twist with respect to the first central axis Ax1, causing the first rack 55 to approach the front support plate 41 and the second rack 65 to approach the rear support plate 44. The front guide roller 43 contacts the first rack 55 when it is close to the front support plate 41, thereby preventing the first rack 55 from contacting the front support plate 41 and guiding the first rack 55 to rotate smoothly around the first central axis Ax1. In other words, the front guide roller 43 can prevent the first rack 55 from contacting the front support plate 41 and becoming unable to rotate. Furthermore, the rear guide roller 46, by contacting the second rack 65 which is close to the rear support plate 44, prevents the second rack 65 from contacting the rear support plate 44 and guides the second rack 65 to rotate smoothly around the first central axis Ax1. In other words, the rear guide roller 46 can prevent the second rack 65 from contacting the rear support plate 44 and becoming unable to rotate. Even if the first rack 55 and the second rack 65 are twisted with respect to the first central axis Ax1, the imbalance in the load acting on the first rack 55 and the second rack 65 can be resolved over time as the first rack 55 and the second rack 65 continue to rotate. Therefore, the acceleration reduction device 10 can ultimately make the rotational speed of the first rack 55 and the rotational speed of the second rack 65 approximately the same. The acceleration reduction device 10 may also have either a front support plate 41 and a front guide roller 43, or a rear support plate 44 and a rear guide roller 46. Furthermore, for example, the right rail 85 may be provided with a guide roller that rolls on the surface of the third rack 95, and the left rail 86 may be provided with a guide roller that rolls on the surface of the fourth rack 105.

[0139] The first central axis Ax1, the central axis Axm1 of the first pinion 56, and the central axis Axm2 of the second pinion 66 are aligned in a straight line in the radial direction perpendicular to the first central axis Ax1.

[0140] The first rack 55 is generally set so that the first pinion 56 is centered within the first rack 55 under normal conditions. Similarly, the second rack 65 is generally set so that the second pinion 66 is centered within the second rack 65 under normal conditions. With this configuration, the acceleration reduction device 10 can prevent the first rack 55 and the second rack 65 from being misaligned around the first central axis Ax1, and for example, the width of the acceleration reduction device 10 in the X direction can be reduced.

[0141] Although embodiments of the present invention have been illustrated above, these embodiments and modifications are merely examples and are not intended to limit the scope of the invention. The above embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, combinations, and changes can be made without departing from the spirit of the invention. Furthermore, the configurations and shapes of each embodiment and modification can be partially replaced. [Explanation of symbols]

[0142] 10...Acceleration reduction device, 21...First rotation mechanism, 22...Second rotation mechanism, 41...Front support plate (first support part), 43...Front guide roller (first roller), 44...Rear support plate (second support part), 46...Rear guide roller (second roller), 51...First drive device, 55...First rack, 55c...First tooth, 56...First pinion, 61...Second drive device, 65...Second rack, 65c...Second Teeth, 66...Second pinion, 91...Third drive unit, 95...Third rack, 95b...Third tooth, 96...Third pinion, 101...Fourth drive unit, 105...Fourth rack, 105b...Fourth tooth, 106...Fourth pinion, 111...First driver, 112...Second driver, Ax1...First central axis, Ax2...Second central axis, Axr...Central axis (Third central axis, Fourth central axis), Pc1, Pc2...Pitch circle.

Claims

1. A first rack having multiple first teeth arranged around a virtual first central axis, A first pinion that meshes with the plurality of first teeth, A first drive device configured to rotate the first pinion, A second rack having a plurality of second teeth arranged around the first central axis, A second pinion that meshes with the aforementioned plurality of second teeth, A second drive device configured to rotate the second pinion, A first driver that inputs a common electrical signal to the first drive unit and the second drive unit, Equipped with, The first rack and the second rack are spaced apart from each other in the first axial direction along the first central axis. The diameter of the pitch circle of the plurality of first teeth is different from the diameter of the pitch circle of the plurality of second teeth. The reduction ratio of the first rack and the first pinion and the reduction ratio of the second rack and the second pinion are set such that when the first driver inputs the electrical signal to the first drive unit and the second drive unit, the first rack and the second rack rotate in alignment with the first central axis relative to the first pinion and the second pinion. Acceleration reduction device.

2. The first rack and the second rack are spaced apart from each other in the horizontal direction. The first pinion is located above or below the first rack. The second pinion is located above or below the second rack. The acceleration reduction device according to claim 1.

3. The first rack is located below the second rack. The first pinion is located below the first rack, The acceleration reduction device according to claim 2.

4. A first rotating mechanism having the first drive unit, the first pinion, the first drive unit, the second rack, the second pinion, and the second drive unit, A second rotating mechanism having a third rack, a third pinion, a third drive unit configured to rotate the third pinion, a fourth rack, a fourth pinion, and a fourth drive unit configured to rotate the fourth pinion, A second driver that inputs a common electrical signal to the third drive unit and the fourth drive unit, Furthermore, The third rack has a plurality of third teeth arranged around a virtual second central axis and meshing with the third pinion, The fourth rack has a plurality of fourth teeth arranged around the second central axis and meshing with the fourth pinion, The second central axis extends in a second axial direction intersecting the first axial direction, The third rack and the fourth rack are spaced apart from each other in the second axial direction. The first rotating mechanism is attached to the second rotating mechanism, The acceleration reduction device according to claim 1.

5. A first support portion that supports the first drive device, A first roller is mounted on the first support so as to be rotatable about a third central axis extending radially perpendicular to the first central axis, and is configured to contact the first rack which rotates about the first central axis, thereby restricting the first rack from approaching the first support and rolling on the surface of the first rack, A second support portion that supports the second drive device, A second roller is mounted on the second support so as to be rotatable about a fourth central axis extending radially perpendicular to the first central axis, and is configured to contact the second rack, which rotates about the first central axis, thereby restricting the second rack from approaching the second support and rolling on the surface of the second rack. The acceleration reduction device according to claim 1, further comprising:

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