Linear Actuator

Abstract

To provide a linear actuator which secures a spacer where a component such as a bolt is arranged at the middle point of a rack gear.SOLUTION: A linear actuator includes a rail, and a pinion unit which is slidably engaged with the rail. The rail includes a rack gear extending in the longitudinal direction of the rail. At least one non-tooth section at a distance L1 is provided at the middle point of the tooth row of the rack gear. The pinon unit includes two pinion gears engaged with the rack gear, and a motor for driving the pinion gears. The two pinion gears are arranged at a distance L2 between centers in the longitudinal direction of the rail. The distance L1 is two pieces or more of tooth pitches of the rack gear, and is shorter than the distance L2 between the centers.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a linear actuator using a rack gear and a pinion gear. [Background technology]

[0002] A linear actuator is sometimes used to electrically slide a vehicle seat. A linear actuator is a device that allows a pinion unit to reciprocate along a rail. The linear actuator may also be a device in which the pinion unit is constrained to the floor and the rail can reciprocate relative to the pinion unit.

[0003] The seat slide device disclosed in Patent Document 1 corresponds to a type of linear actuator. The seat slide device includes a lower rail attached to the floor and an upper rail fixed to the seat. The upper rail is slidably engaged with the lower rail. The lower rail includes a rack gear, and the upper rail includes a pinion gear and a motor (electric motor). The pinion gear of the upper rail is engaged with the rack gear of the lower rail. The motor drives the pinion gear, causing the upper rail including the pinion gear to move along the rack gear. In other words, the seat moves along the longitudinal direction of the lower rail.

[0004] In this specification, a component equipped with a rack gear is referred to as a rail, and a component equipped with a pinion gear and a motor is referred to as a pinion unit. In an electric seat slide device, the lower rail corresponds to the rail, and the upper rail corresponds to the pinion unit. The linear actuator disclosed in this specification may be of a type in which the rail is fixed to the base of the machine and the pinion unit moves on the rail, or of a type in which the pinion unit is fixed to the base of the machine and the rail moves. For convenience of explanation, both types will be expressed as "the pinion unit is attached so as to be slidable relative to the rail." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-193007 Summary of the Invention [Problem to be solved by the invention]

[0006] A rack gear is fixed to a long, narrow rail. Other components (e.g., a floor panel) are also fixed to the rail. There is a risk of interference between the rack gear and the bolts that secure the other components. For example, in the case of an electric seat slide device, the bottom plate of a rail (lower rail) is fixed to the floor panel with bolts, and the rack gear is fixed to the bottom plate. In this case, interference between the bolts and the rack gear can be avoided by forming a notch on the underside of the rack gear with a row of teeth on its upper surface and configuring the rack gear so that the bolt head is located in the space of the notch. However, in this case, the rack gear must be attached to the rail after the rail is attached to the floor panel, which is time-consuming. This specification provides a linear actuator that provides space for placing components such as bolts midway through the row of teeth of the rack gear. [Means for solving the problem]

[0007] The linear actuator disclosed in this specification includes a rail and a pinion unit that slidably engages with the rail. The rail includes a rack gear that extends along the longitudinal direction of the rail. At least one toothless section of distance L1 is provided midway along the tooth row of the rack gear. The pinion unit includes two pinion gears that engage with the rack gear and a motor that drives the pinion gears. The two pinion gears are arranged longitudinally of the rail, separated by a center distance L2. The distance L1 is at least two tooth pitches of the rack gear and is shorter than the center distance L2.

[0008] The linear actuator disclosed in this specification has a toothless section in the tooth row of the rack gear. Components such as bolts can be placed in this toothless section. Meanwhile, two pinion gears are attached to the pinion unit so that it can move beyond the toothless section. When one pinion gear passes through the toothless section, the other pinion gear engages with the rack gear, allowing the pinion unit to move beyond the toothless section. The toothless section may be a notch provided in the tooth row of a single rack gear. Alternatively, the rack gear may include a first rack gear and a second rack gear aligned in a straight line, spaced a distance L1 apart. The space between the first rack gear and the second rack gear corresponds to the toothless section. When the linear actuator is used in a seat slide device, the rail corresponds to the lower rail, and the pinion unit corresponds to the upper rail.

[0009] The distance between the two end teeth on either side of the toothless section of the rack gear should be an integer multiple of the tooth pitch. This allows the pinion gear to smoothly re-engage with the rack gear after passing through the toothless section. The distance between the two end teeth refers to the distance from the center of one end tooth to the center of the other end tooth.

[0010] The pinion unit preferably includes one idle gear, and two pinion gears are preferably engaged with the idle gear. The two pinion gears are interlocked via the idle gear. This configuration allows the two pinion gears to easily rotate synchronously. This feature, combined with the fact that the spacing between the end teeth on both sides of the toothless section is an integer multiple of the tooth pitch, allows the pinion gear to more smoothly re-engage with the rack gear after passing through the toothless section.

[0011] The size of the end teeth (the teeth located on both sides of the toothless section) is preferably smaller than the other teeth on the rack gear, and the height of the end teeth is greater than the distance between the bottom of the rack gear tooth valley and the tip of the pinion gear tooth when the rack gear and pinion gear are engaged. Making the end teeth smaller than the other teeth allows the pinion gear to re-engage more smoothly after passing through the toothless section.

[0012] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a side view of a seat including a linear actuator (seat slide device) according to an embodiment. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. 1 is a diagram showing the engagement relationship between a rack gear and two pinion gears (1). [Figure 5] FIG. 10 is a diagram showing the engagement relationship between the rack gear and two pinion gears (2). [Figure 6] FIG. 10 is a diagram showing the engagement relationship between the rack gear and two pinion gears (3). [Figure 7] FIG. 4 is a diagram showing the engagement relationship between the rack gear and two pinion gears (4). [Figure 8] 10A and 10B are diagrams illustrating a modified example of a seat slide device. [Figure 9] FIG. 10 is a side view of the end of the rack gear (first modified example of the rack gear). [Figure 10] FIG. 10 is a side view of the end of the rack gear (second modified example of the rack gear). [Figure 11] FIG. 10 is a side view of the end of the rack gear (third modified example of the rack gear). [Figure 12] FIG. 10 is a side view of the end of the rack gear (fourth modified example of the rack gear). [Figure 13] FIG. 10 is a side view of the end of the rack gear (fifth modified example of the rack gear). [Figure 14] FIG. 10 is a side view of the end of the rack gear (sixth modified example of the rack gear). DETAILED DESCRIPTION OF THE INVENTION

[0014] (Example) A linear actuator of the example will be described with reference to the drawings. The linear actuator of the example is a seat slide device 2 arranged between a floor panel and a seat. FIG. 1 shows a side view of the seat slide device 2 attached to a floor panel 90 of an automobile. The seat slide device 2 is composed of a lower rail 10 and an upper rail 20. The lower rail 10 is long. The upper rail 20 is attached to the lower rail 10 so as to be movable (slidable) in its longitudinal direction. As will be described in detail later, the upper rail 20 can be moved along the lower rail 10 by a motor. When a user turns on a switch (not shown), the motor rotates, and the upper rail 20 (seat) moves along the lower rail 10. The lower rail 10 corresponds to the rail of the linear actuator, and the upper rail 20 corresponds to the pinion unit of the linear actuator.

[0015] The lower rails 10 are fixed to a floor panel 90 of the vehicle body. The upper rails 20 are attached to the bottom of a seat 91. The upper rails 20 are attached to the bottom of the seat 91 via a frame (not shown). A pair of seat slide devices 2 are attached to one seat 91. Each of the pair of upper rails 20 is attached to the left and right sides of the bottom of the seat 91. Each of the pair of lower rails 10 is fixed to the floor panel 90 so as to correspond to each of the pair of upper rails 20.

[0016] The X direction of the coordinate system in the drawing corresponds to the longitudinal direction of the lower rail 10 and the upper rail 20. The longitudinal direction of the rail (X direction) will be referred to as the rail longitudinal direction hereinafter. The Y direction of the coordinate system in the drawing corresponds to the rail lateral direction. The rail lateral direction will be referred to as the rail lateral direction hereinafter. The +Z direction of the coordinate system in the drawing indicates upward.

[0017] Fig. 2 shows a front view of the seat slide device 2. Fig. 2 is a view of the seat slide device 2 seen along the longitudinal direction of the rail. Fig. 3 shows a side view of the seat slide device 2. Fig. 3 is a side view of the seat slide device 2 seen along line III-III in Fig. 2.

[0018] The cross section of the lower rail 10 cut along a plane perpendicular to the rail longitudinal direction has a groove shape, and the lower rail 10 has a bottom plate 11 and a pair of side plates 19 extending upward from both ends of the bottom plate 11 in the rail short direction. The lower rail 10 also has a rack gear 12 extending along the rail longitudinal direction. The rack gear 12 is fixed to the bottom plate 11. Note that gear teeth of the rack gear 12 are not shown in Figures 2 and 3.

[0019] A groove is formed in the floor panel 90, and the lower rail 10 is disposed in the groove of the floor panel 90. The lower rail 10 is fixed to the floor panel 90 by a bolt 93. The head of the bolt 93 is disposed midway between the rows of teeth of the rack gear 12 in the longitudinal direction of the rail. The rack gear 12 is provided with a notch 13 that is open upward, and the head of the bolt 93 is disposed in the notch 13. The rack gear 12, the bottom plate 11, and the floor panel 90 are fastened together by the bolt 93.

[0020] The upper rail 20 is provided with a plurality of rollers 28. The rollers 28 are provided at the four corners of a main body 29 of the upper rail 20. The rollers 28 abut against the bottom plate 11 of the lower rail 10. The four rollers 28 allow the upper rail 20 to move smoothly along the lower rail 10. The upper portion of the side plate 19 of the lower rail 10 is curved in an inverted U shape, and the rollers 28 are accommodated in the space between the bottom plate 11 and the upper curved portion of the side plate 19. In Figure 3, the main body 29 and rollers 28 of the upper rail 20 are drawn with imaginary lines.

[0021] The upper rail 20 is provided with two pinion gears (a first pinion gear 21 and a second pinion gear 22), one idle gear 23, and a motor 24. Note that in FIGS. 2 and 3, the first pinion gear 21, the second pinion gear 22, and the idle gear 23 are depicted in a simplified manner, with the gear teeth not shown. The first pinion gear 21 and the second pinion gear 22 are engaged with the rack gear 12, and the idle gear 23 is engaged with both the first pinion gear 21 and the second pinion gear 22. The motor 24 drives the idle gear 23 via a reducer (not shown). When the motor 24 drives the idle gear 23, the first pinion gear 21 and the second pinion gear 22 rotate synchronously in conjunction with the idle gear 23. When the motor 24 drives the first pinion gear 21 and the second pinion gear 22, the upper rail 20 moves along the rack gear 12 (i.e., the lower rail 10). In other words, the upper rail 20 moves electrically.

[0022] The gear engagement relationship will be explained with reference to Figure 4-7. In Figure 4-7, the main body 29 and rollers 28 of the upper rail 20 are not shown. The side plate 19 of the lower rail 10 is also not shown. In Figure 4-7, there is a gap between the engaged gears, but this gap is provided for convenience to make the drawing easier to see. Naturally, it is better to have as little backlash between the engaged gears as possible.

[0023] As described above, the rack gear 12 has a notch 13 that is open upward. The rack gear 12 has no teeth within the area of ​​the notch 13. The area of ​​the notch 13 (i.e., the area without teeth) will be referred to as the toothless section 14 below. The toothless section 14 is provided midway through the row of teeth of the rack gear 12. The head of the bolt 93 is located in the toothless section 14. The bolt 93 passes through the bottom of the notch 13, the bottom plate 11 of the lower rail 10, and the floor panel 90 to secure them together.

[0024] The toothless section 14 is provided to ensure space for placing the head of the bolt 93 on the narrow bottom plate 11. The toothless section 14 has a length of a distance L1 along the longitudinal direction of the rail. The distance L1 is equal to or greater than two tooth pitches of the rack gear 12. In Figures 4-7, gear teeth are drawn in imaginary lines in the toothless section 14 to help understand the relationship between the distance L1 and the tooth pitch. The symbol Pt in Figure 4 indicates the tooth pitch. In this embodiment, the distance L1 of the toothless section 14 is longer than twice the tooth pitch Pt and shorter than three times the tooth pitch Pt.

[0025] Two pinion gears (a first pinion gear 21 and a second pinion gear 22) are attached to the upper rail 20. The two pinion gears are aligned in the longitudinal direction of the rail. The two pinion gears are arranged at a center distance L2 along the longitudinal direction of the rail. The two pinion gears (the first pinion gear 21 and the second pinion gear 22) have the same shape. The two pinion gears (the first pinion gear 21 and the second pinion gear 22) have the same diameter and the same number of gear teeth. As described above, the idle gear 23 is engaged with both the first pinion gear 21 and the second pinion gear 22, and the motor 24 drives the first pinion gear 21 and the second pinion gear 22 via the idle gear 23. The first pinion gear 21 and the second pinion gear 22, which have the same shape, rotate synchronously through one idle gear 23, and therefore rotate smoothly while engaging with the rack gear 12.

[0026] 4 to 7, it is assumed that the upper rail 20 moves in the direction indicated by the thick arrow A (to the left). However, for convenience of illustration, the lower rail 10 moves from left to right in the order of Fig. 4 to Fig. 7. The toothless section 14 moves from left to right in the order of Fig. 4 to Fig. 7.

[0027] In Figure 4, the toothless section 14 is located forward in the direction of travel of the upper rail 20. The distance L1 of the toothless section 14 is equal to or greater than two tooth pitches Pt of the rack gear 12. Therefore, when the first pinion gear 21 reaches the toothless section 14, the first pinion gear 21 disengages from the rack gear 12 and spins freely (Figure 5). However, because the second pinion gear 22 remains engaged with the rack gear 12, the upper rail 20 can continue to move.

[0028] As the upper rail 20 moves further, the first pinion gear 21 re-engages with the rack gear 12 (see FIG. 6). The distance L3 between the two end teeth 15a, 15b located on both sides of the toothless section 14 is an integer multiple of the tooth pitch Pt. In this embodiment, the distance L3 is three times the tooth pitch Pt (see FIG. 4). The distance L3 between the end teeth 15a, 15b refers to the distance from the center of one end tooth 15a to the center of the other end tooth 15b. Therefore, after passing through the toothless section 14 while rotating, the first pinion gear 21 can smoothly re-engage with the rack gear 12. The location indicated by the thick arrow B in FIG. 6 indicates the location where the end tooth 15a and the first pinion gear 21 re-engage. The first pinion gear 21 rotates idly while passing through the toothless section 14, but when it re-engages with the rack gear 12, the crest of the end tooth 15a and the trough of the first pinion gear 21 match.

[0029] As the upper rail 20 moves further leftward, the second pinion gear 22 passes through the toothless section 14 (FIG. 7). At this time, the second pinion gear 22 rotates freely, but the first pinion gear 21 remains engaged with the rack gear 12, allowing the upper rail 20 to move forward. As with the first pinion gear 21, the second pinion gear 22 can also smoothly re-engage with the rack gear 12.

[0030] In this way, the seat slide device 2 of the embodiment provides the rack gear 12 with the toothless section 14, allowing the bolt 93 to be positioned midway along the tooth row of the rack gear 12. The upper rail 20, which has two pinion gears (the first pinion gear 21 and the second pinion gear 22), can move smoothly beyond the toothless section 14. The distance L1 of the toothless section 14 is shorter than the center-to-center distance L2 between the two pinion gears (the first pinion gear 21 and the second pinion gear 22). This is because if the toothless section 14 were longer than the center-to-center distance L2, both pinion gears would fall within the toothless section. Preferably, the distance L3 between the end teeth 15a, 15b is shorter than the center-to-center distance L2. Components other than bolts may be positioned in the toothless section 14.

[0031] (Modification) A modified seat slide device 2a will be described with reference to FIG. 8. The upper rail 20 of the seat slide device 2a is the same as the upper rail 20 of the seat slide device 2 of the embodiment. The main body and rollers of the upper rail 20 are also omitted from FIG. 8. The modified seat slide device 2a includes two rack gears 12a, 12b. The two rack gears 12 are arranged at a distance L1 along the rail longitudinal direction. The space of distance L1 between the two rack gears 12a, 12b corresponds to the toothless section 14. The head of the bolt 93 is located in the toothless section 14. The distance L1 is equal to or greater than two tooth pitches of the rack gear and is shorter than the center-to-center distance L2 of the two pinion gears. Furthermore, the distance L3 between the end teeth 15a, 15b on both sides of the toothless section 14 is an integer multiple of the tooth pitch of the rack gears 12a, 12b. The distance L3 is shorter than the center-to-center distance L2.

[0032] The seat slide device 2a is also electrically driven by the motor 24. In the seat slide device 2a as well, the upper rail 20 can move smoothly beyond the toothless section 14.

[0033] Next, variations in the shape of the end teeth of the rack gear will be described with reference to Figures 9-14. The rack gear 112 in Figure 9-14 corresponds to the rack gear 12 in Figure 2-8. The pinion gear 121 in Figure 9-14 corresponds to the first pinion gear 21 in Figure 2-8. The pinion gear 121a shown in phantom lines approaches the rack gear 112 from the right and indicates the pinion gear just before engaging with the rack gear 112.

[0034] 9-14, the teeth located at the ends of the rack gear 112 are referred to as end teeth 115 (115a, 115b, 115c), the teeth next to the end teeth 115 are referred to as subsequent teeth 116 (116a, 116b, 116c), and the other teeth are referred to as normal teeth 117. The end teeth 115 may also be teeth located next to a toothless section.

[0035] In the example of Figure 9, the size of the end tooth 115a is smaller than the normal tooth 117 in a side view of the rack gear 112. In the example of Figure 9, the next tooth 116 has the same size as the normal tooth 117. The height H1 of the end tooth 115a is smaller than the height H2 of the normal tooth 117. The height H1 of the end tooth 115a is larger than the distance H3 between the tooth tip of the pinion gear 121 engaged with the rack gear 112 and the tooth trough of the rack gear 112. By making the end tooth 115a smaller, the pinion gear 121 that has passed through the toothless section can more easily engage with the rack gear 112. "Height H1 > distance H3" is a necessary condition for the pinion gear 121 to engage with the end tooth 115a.

[0036] In the example of FIG. 10 , in a side view of the rack gear 112, the size of the end tooth 115a is smaller than the normal tooth 117, and the size of the next tooth 116a is larger than the end tooth 115a but smaller than the normal tooth 117. The height H1 of the end tooth 115a is smaller than the height H2 of the normal tooth 117. The height H1 of the end tooth 115a is larger than the distance H3 between the tooth tip of the pinion gear 121 engaged with the rack gear 112 and the tooth trough of the rack gear 112. The height H4 of the next tooth 116a is larger than the height H1 of the end tooth 115a but smaller than the height H2 of the normal tooth 117. By gradually decreasing the tooth height from the center of the rack gear 112 toward the end, the pinion gear 121 that has reached the end of the rack gear 112 can more easily engage with the rack gear 112.

[0037] In the example of FIG. 11, in a side view, the tip width W1 of the end tooth 115b is narrower than the tip width W2 of the normal tooth 117 (that is, tip width W1 < tip width W2). In the example of FIG. 11, the next tooth 116 has the same shape as the normal tooth 117. By narrowing the tip width W1 of the end tooth 115b, the pinion gear 121 that has passed through the toothless section can be more easily engaged with the rack gear 112.

[0038] In the example of FIG. 12, in a side view, the tip width W1 of the end tooth 115b is narrower than the tip width W2 of the normal tooth 117 (that is, tip width W1 < tip width W2). Further, the tip width W3 of the next tooth 116b is wider than the tip width W1 and narrower than the tip width W2 (W1 < W3 < W2). By gradually narrowing the tip width of the teeth from the center of the rack gear 112 toward the end, the pinion gear 121 that has reached the rack gear 112 can be more easily engaged with the rack gear 112.

[0039] In the example of FIG. 13, in a side view, the angle A1 of the side surface of the end tooth 115c on the rack gear end side is gentler than the angle A2 of the side surface of the normal tooth 117 (that is, angle A1 < angle A2). In the example of FIG. 13, the next tooth 116 has the same shape as the normal tooth 117. By making the angle A of the side surface of the end tooth 115c gentler, the pinion gear 121 that has passed through the toothless section can be more easily engaged with the rack gear 112.

[0040] In the example of FIG. 14, in a side view, the angle A1 of the side surface of the end tooth 115c on the rack gear end side is gentler than the angle A2 of the side surface of the normal tooth 117. The angle A3 of the side surface of the next tooth 116c on the rack gear end side is larger than the angle A1 and smaller than the angle A2 (angle A2 > angle A3 > angle A1). By gradually decreasing the angle of the side surface of the teeth from the center of the rack gear 112 toward the end, the pinion gear 121 that has reached the end of the rack gear 112 can be more easily engaged with the rack gear 112. The angles A1, A2, and A3 indicate the angles of the side surfaces of the teeth with respect to the longitudinal direction of the rail.

[0041] The height of the end tooth may be lower than the height of the normal tooth, and the tip width of the end tooth may be narrower than the tip width of the normal tooth.The height of the end tooth may be lower than the height of the normal tooth, and the angle of the side surface of the end tooth may be smaller than the angle of the side surface of the normal tooth.The tip width of the end tooth may be narrower than the tip width of the normal tooth, and the angle of the side surface of the end tooth may be smaller than the angle of the side surface of the normal tooth.The height of the end tooth may be lower than the height of the normal tooth, and the angle of the side surface of the end tooth may be smaller than the angle of the side surface of the normal tooth, and the tip width of the end tooth may be narrower than the tip width of the normal tooth.

[0042] Here are some points to note regarding the technology described in the embodiment. Two pinion gears (first pinion gear 21 and second pinion gear 22) are engaged with one idle gear 23. This configuration allows the two pinion gears to rotate precisely in synchronization. Therefore, each of the two pinion gears smoothly engages with the rack gear 12.

[0043] In the embodiment, the motor 24 directly drives the idle gear 23. The motor 24 may also directly drive the first pinion gear 21 (or the second pinion gear 22). Even when the motor 24 directly drives the first pinion gear 21 (second pinion gear 22), the second pinion gear 22 (first pinion gear 21) rotates via the idle gear 23. In this case, the first pinion gear 21 and the second pinion gear 22 rotate synchronously.

[0044] It is preferable that the two pinion gears (first pinion gear 21 and second pinion gear 22) are engaged with one idle gear 23. However, the two pinion gears (first pinion gear 21 and second pinion gear 22) may be interlocked via multiple idle gears 23. However, the two pinion gears must have the same shape and rotate at the same speed.

[0045] A single rack gear may have multiple toothless sections. The lower rail may include three or more rack gears. Adjacent rack gears in the longitudinal direction of the rail may be spaced apart by a distance L1. Furthermore, the distance between a pair of end teeth located on both sides of a toothless section (distance L3 in FIG. 4) should be an integer multiple of the tooth pitch of the rack gear 112 and should be narrower than the center-to-center distance L2 of the two pinion gears.

[0046] A linear actuator in which two pinion gears engage with a rack gear can be applied to applications other than seat slide devices. The linear actuator disclosed in this specification has the following features: The linear actuator includes a rail and a pinion unit slidably attached to the rail. The rail includes a rack gear extending along the rail longitudinal direction. At least one toothless section of distance L1 is provided midway along the tooth row of the rack gear. The pinion unit includes two pinion gears that engage with the rack gear and a motor that drives the pinion gear. The two pinion gears are arranged in the rail longitudinal direction, separated by a center-to-center distance L2. The distance L1 is at least two tooth pitches of the rack gear and is shorter than the center-to-center distance L2. Preferably, the distance L3 between a pair of end teeth located on both sides of the toothless section is shorter than the center-to-center distance L2. In this linear actuator, the pinion unit can move beyond the toothless section.

[0047] The pinion unit can be moved relative to the rail by the motor. The pinion unit may be fixed to the floor and the rail may move, or the rail may be fixed to the floor and the pinion unit may move.

[0048] The pinion unit may be provided with rollers that allow it to move smoothly along the rail. The pinion unit is constrained so that it can move along the rail. The rollers 28 of the pinion unit (upper rail 20) are components that constrain the pinion unit so that it can move in the longitudinal direction of the rail.

[0049] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0050] 2, 2a: Seat slide device (linear actuator) 10: Lower rail 11: Bottom plate 12, 12a, 12b, 112: Rack gear 13: Notch 14: Toothless section 15a, 15b: End teeth 19: Side plate 20: Upper rail (pinion unit) 21: First pinion gear 22: Second pinion gear 23: Idle gear 24: Motor 28: Roller 29: Main body 90: Floor panel 91: Seat 93: Bolt 115a-115c: End teeth 116, 116a-116c: Next teeth 117: Regular teeth 121, 121a: Pinion gear

Claims

1. Rails and a pinion unit slidably attached to the rail; It is equipped with the rail is provided with a rack gear extending along the longitudinal direction of the rail, the rack gear having at least one toothless section of a distance L1 in the middle of a row of teeth, the pinion unit includes two pinion gears that engage with the rack gear and are arranged at a center distance L2 in the longitudinal direction, and a motor that drives the pinion gears, A linear actuator, wherein the distance L1 is equal to or greater than two tooth pitches of the rack gear and is shorter than the center-to-center distance L2.

2. 2. The linear actuator according to claim 1, wherein the interval between two end teeth located on both sides of the toothless section of the rack gear is an integer multiple of the tooth pitch.

3. 3. The linear actuator according to claim 1, wherein two of the pinion gears are engaged with one idler gear.

4. 2. The linear actuator according to claim 1, wherein an end tooth of the rack gear located adjacent to the toothless section is smaller in size than other teeth of the rack gear, and a height of the end tooth is greater than a distance between a bottom of a tooth valley of the rack gear and a tip of a tooth of the pinion gear when the rack gear and the pinion gear are engaged with each other.

5. The rack gear includes a first rack gear and a second rack gear, 2. The linear actuator according to claim 1, wherein the first rack gear and the second rack gear are arranged in the longitudinal direction with the toothless section spaced apart by a distance L1.

6. the rail is a lower rail fixed to a floor panel, The pinion unit is an upper rail attached to the lower part of the seat, 2. The linear actuator according to claim 1, wherein the lower rail and the upper rail constitute a seat slide device that moves a seat relative to a floor panel.

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