POWER TRANSMISSION DEVICE AND DRIVE UNIT

Abstract

A power transmission device comprising: an annular stationary part; an output shaft with a recessed surface; a drive shaft with a pressure section; a pair of first rolling elements arranged circumferentially opposite each other with respect to the pressure section; and a pair of intermediate objects arranged between the respective first rolling element and the pressure section. The recessed surface comprises a pair of pressure surfaces and a bottom surface comprising a pair of cam surfaces, each having the respective first rolling element arranged on a radially outer side, and a pair of guide surfaces, each having the respective intermediate object clamped between the first rolling element, the guide surface, and the pressure section, and arranged on a radially outer side.The distance between each cam face and the inner circumferential surface gradually increases with increasing proximity to the corresponding pressure surface. The distance between a section of each cam face that is closer to the corresponding guide surface and the inner circumferential surface is smaller than the diameter of each first rolling element. The pressure section presses the central object between the first rolling element and the guide surface as it moves circumferentially outward from a state in which it is located circumferentially at a central section of the recessed surface.

Description

[Technical field]

[0001] The present disclosure relates to a power transmission device and a drive unit. [State of the art]

[0002] Power transmission devices transmit torque generated by a motor or the like. Such a power transmission device is used, for example, in a drive unit that powers an arm or the like of an industrial robot. A power transmission device comprises a drive shaft, onto which torque is applied, and an output shaft, which delivers torque. An object to be driven is connected to the output shaft. Therefore, the weight or similar force of the object (hereinafter referred to as the "external force") can act on the output shaft. If the output shaft rotates due to the external force, the position of the object is not maintained. Therefore, in a power transmission device according to patent literature 1, the output shaft does not rotate even when an external force acts on the output shaft.

[0003] The following describes the details of the power transmission device from patent literature 1. The power transmission device from patent literature 1 comprises an annular stationary part, an output shaft with a cam surface facing the inner circumferential surface of the stationary part, a cylindrical roller arranged between the stationary part and the cam surface, and a drive shaft with a pressure section arranged circumferentially to the cylindrical roller. When an external force acts on the output shaft and the output shaft rotates, the cylindrical roller is clamped between the stationary part and the cam surface, thus restricting the rotation of the output shaft. When a torque is applied to the drive shaft, the pressure section presses against the cylindrical roller.As a result, the cylindrical roller clamped between the stationary part and the cam surface moves, thereby releasing the locking state. [Citation list][Patent literature]

[0004] [Patent Literature 1] Japanese Patent No. 4621156 [Summary][Technical Task]

[0005] When torque is applied to the input shaft, an external force acting in the same direction as the torque on the output shaft may occur. In such cases, the cylindrical roller clamped between the stationary part and the cam surface moves, even when pressed through the pressure area, and the cam surface moves in the same direction, potentially clamping the cylindrical roller between the stationary part and the cam surface again. This results in repeated alternating states of unlocked and locked operation, which can cause an input and output element to rotate intermittently. Therefore, it is desirable to develop a power transmission device in which this phenomenon of repeated unlocking and locking (hereinafter referred to as jerking) is unlikely to occur.Furthermore, it is conventionally desirable to reduce the torque required for unlocking.

[0006] The present disclosure was made taking into account the foregoing, and one objective of the present disclosure is to provide a power transmission device and a drive unit that are able to reduce the torque required for unlocking while suppressing the occurrence of the jerking phenomenon. [Solution to the problem]

[0007] To solve the problem described above, a power transmission device comprises: an annular stationary part with an inner circumferential surface; an output shaft with an outer circumferential surface facing the inner circumferential surface and a recessed surface extending radially inward from the outer circumferential surface; a drive shaft with a pressure section accommodated in the recessed surface; a pair of first rolling elements accommodated in the recessed surface and arranged circumferentially opposite the pressure section; and a pair of intermediate objects, each of which is arranged between the corresponding first rolling element and the pressure section. The recessed surface comprises: a bottom surface extending circumferentially and facing radially toward the inner circumferential surface; and a pair of contact surfaces extending radially outward from opposite circumferential ends of the bottom surface.The base surface comprises: a pair of cam surfaces, each having the corresponding first rolling element located on a radially outer side; and a pair of guide surfaces, each having the corresponding intermediate object located on a radially outer side. The distance between each cam surface and the inner circumferential surface gradually increases with increasing proximity to the corresponding pressure surface. The distance between a section of each cam surface closer to the corresponding guide surface and the inner circumferential surface is less than the diameter of each first rolling element. The distance between a section of each cam surface closer to the corresponding pressure surface and the inner circumferential surface is greater than the diameter of each first rolling element. The intermediate object is located between the first rolling element, the guide surface, and the pressure section.The pressure section presses the central object between the first rolling element and the guide surface as it moves circumferentially outward, starting from a state where it is located circumferentially in a central section of the recessed surface. The central object is either a second rolling element with a smaller diameter than the first rolling element or a wedge-shaped body with a wedge surface that gradually narrows in the direction in which the wedge-shaped body is pressed through the pressure section.

[0008] To achieve the aforementioned objective, a drive unit according to one aspect of the present disclosure comprises a motor and the power transmission device described above. The torque generated by the motor is transmitted to the drive shaft. [Advantageous effects of the invention]

[0009] According to a power transmission device and a drive unit of the present disclosure, the occurrence of jerking is suppressed and the torque required for unlocking is also reduced. [Brief description of the drawings] Fig. Figure 1 is a schematic representation of a power transmission device of a first embodiment, viewed from an axial direction; Fig. 2 is a sectional view along line II-II in Fig. 1; Fig. Figure 3 is an enlarged view showing one of the recessed areas in Fig. 1 is shown enlarged; Fig. 4 is an enlarged view showing part of Fig. 3 is enlarged; Fig. Figure 5 is a diagram illustrating an operating state of the power transmission device of the first embodiment, specifically a diagram at the time of the start of the torque input; Fig. Figure 6 is a diagram illustrating an operating state of the power transmission device of the first embodiment, and is in particular a diagram at the time of release of a locked state; Fig. 7 is a diagram illustrating an operating state of the power transmission device of the first embodiment, and is in particular a diagram in a state in which a first roller is in contact with a pressure surface; Fig. Figure 8 is a diagram representing an operating state of the power transmission device of the first embodiment, specifically a diagram at the time when the first roller begins to move backward in the second direction of rotation; Fig. Figure 9 is a diagram showing the time at which the input of a torque to a drive shaft (first direction of rotation) begins in a state in which an external force (first direction of rotation) acts on an output shaft in the power transmission device of the first embodiment; Fig. Figure 10 is a diagram at the time when the torque input into the drive shaft (first direction of rotation) begins in a state in which an external force (second direction of rotation) acts on the output shaft in the power transmission device of the first embodiment; Fig. Figure 11 is an enlarged view showing one of the recessed surfaces of a power transmission device of a first modification; Fig. Figure 12 is a diagram showing a state in which a pressure section presses on a pressure surface via a first roller in the power transmission device of the first modification; Fig. Figure 13 is an enlarged view showing one of the recessed surfaces of a power transmission device of a second modification; Fig. 14 is a diagram showing a state in which a pressure section presses on a pressure surface via a second roller and a first roller in the power transmission device of the second modification; Fig. Figure 15 is a partial cross-sectional view in which the environment of a pressure surface in a power transmission device of a third modification is shown enlarged; Fig. Figure 16 is an enlarged view showing one of the recessed surfaces of a power transmission device of a fourth modification; Fig. Figure 17 is a schematic diagram showing one of the recessed surfaces of the power transmission device of a fifth modification viewed from the axial direction; Fig. Figure 18 is a schematic diagram illustrating the configuration of a drive unit of a second embodiment; and Fig. Figure 19 is a schematic diagram showing the configuration of a drive unit of a sixth modification of. [Description of the embodiments]

[0010] The embodiments according to this disclosure are described in detail with reference to the drawings. This disclosure is not limited to the content of the following description. Furthermore, the components described below include those that are readily conceivable to those skilled in the art, as well as those that are essentially the same. Moreover, the components described below can be combined as required. First embodiment

[0011] Fig. Figure 1 is a schematic representation of a power transmission device of a first embodiment, viewed from the axial direction. Fig. 2 is a sectional view along line II-II in Fig. 1. As in Fig. Figure 1 shows a power transmission device 100 according to the first embodiment comprising a stationary part 1, an output shaft 2, a drive shaft 3, a plurality of first rollers (first rolling elements) 4 and a plurality of second rollers (second rolling elements) 5.

[0012] The fixed part 1 is an annular part. An inner circumferential surface 10 and an outer circumferential surface 11 of the fixed part 1 are circular around the central axis X. Hereinafter, a direction parallel to the central axis X of the inner circumferential surface 10 is referred to as the axial direction. A direction orthogonal to the central axis X is referred to as the radial direction. A direction around the central axis X is referred to as the circumferential direction.

[0013] As in Fig. As shown in Figure 2, the output shaft 2 comprises an inner ring section 20 arranged within the stationary part 1, and an output shaft body 21 projecting axially to one side from the inner ring section 20. The drive shaft 3 comprises a torque transmission section 30 arranged within the stationary part 1, and a drive shaft body 31 projecting axially from the torque transmission section 30 to the other side.

[0014] With respect to the axial direction, the direction in which the drive shaft body 31 projects from the perspective of the torque transmission section 30 is referred to as the first direction X1. The direction in which the output shaft body 21 projects from the perspective of the inner ring section 20 is referred to as the second direction X2. With respect to the circumferential direction, the description is given based on a case viewed from the second direction X2, as shown in Fig. Figure 1 illustrates the following. The leftward rotation direction (counterclockwise) viewed from the second direction X2 is designated as the first rotation direction L1. The rightward rotation direction (clockwise) viewed from the second direction X2 is designated as the second rotation direction L2.

[0015] As in Fig. As shown in Figure 1, an outer circumferential surface 22 of the inner ring section 20 faces the inner circumferential surface 10 of the stationary part 1. The diameter of the outer circumferential surface 22 is essentially equal to the diameter of the inner circumferential surface 10 of the stationary part 1. The inner ring section 20 is rotatably arranged on the inner circumferential side of the stationary part 1.

[0016] Three radially inwardly recessed surfaces 23 are formed on the outer circumferential surface 22 of the inner ring section 20. A pressure section 34 of the drive shaft 3, described later, two (a pair) first rollers 4 and two (a pair) second rollers 5 are accommodated in each recessed surface 23.

[0017] As in Fig. As shown in Figure 2, the outer diameter of the torque transmission section 30 corresponds essentially to the diameter of the inner circumferential surface 10 of the stationary part 1. The torque transmission section 30 is rotatably arranged on the inner circumferential side of the stationary part 1. The torque transmission section 30 comprises a disk-shaped disk section 33, which is arranged in the first direction X1 with respect to the inner ring section 20, and pressure sections 34 that project from the disk section 33 in the second direction X2.

[0018] As in Fig. As shown in Figure 1, each of the first rollers 4 and the second rollers 5 is a cylindrical roller formed in a columnar shape. The diameter of the first rollers 4 is denoted by H1 (see Figure 1). Fig. 1) The second rollers 5 have a diameter of H2 (see Fig. 1), which is smaller than that of the first rollers 4.

[0019] The three in Fig. The virtual lines W1, W2, and W3 shown in Figure 1 are straight lines extending radially from the central axis X and spaced at 120° intervals. The internal shape of the stationary part 1 is rotationally symmetric about the central axis X in three directions. This means that if the stationary part 1 is divided circumferentially into three parts along the virtual lines W1, W2, and W3, each of the divided shapes is identical to the others. One of the three divisions is described below.

[0020] Fig. Figure 3 is an enlarged view of one of the recessed surfaces from Fig. 1. A virtual line W4 in Fig. Line 3 extends circumferentially from the central axis X through a central section of the recessed surface 23. The recessed surface 23 is symmetrical about the virtual line W4. More precisely, the recessed surface 23 has a lower surface 24 and a pair of pressed surfaces 25. The lower surface 24 comprises a central surface 26 located at a central circumferential section of the lower surface 24, a pair of cam surfaces 27 located at opposite circumferential ends of the lower surface 24, and a pair of guide surfaces 28 located between the central surface 26 and the cam surfaces 27. Hereinafter, the circumferential direction in which the cam surface 27 is arranged, viewed from the central surface 26, is referred to as the outer circumferential side. Conversely, the circumferential direction in which the central surface 26 is arranged, viewed from the cam surface 27, is referred to as the inner circumferential side.

[0021] A first roller 4 is arranged on a radially outer side with respect to the cam surface 27. The radius M1 from the central axis X to the cam surface 27 gradually decreases as the distance from a pressed surface 25 is reduced. Therefore, the distance M2 between the inner circumferential surface 10 of the stationary part 1 and the cam surface 27 gradually increases as the distance from the pressed surface 25 is reduced.

[0022] When the first roller 4 moves towards the guide surface 28, it is clamped between the cam surface 27 and the inner circumferential surface 10, thus locking the output shaft 2. That is, the distance M2 from a part of the cam surface 27 closer to the guide surface 28 to the inner circumferential surface 10 is smaller than the diameter H1 of the first roller 4 (see Fig. 1).

[0023] If, however, the first roller 4 moves towards the pressed surface 25, the first roller 4 is loosely attached, without being clamped between the cam surface 27 and the inner circumferential surface 10 (unlocked state). That is, the distance M2 from a section of the cam surface 27 that is closer to the pressed surface 25 to the inner circumferential surface 10 is greater than the diameter H1 of the first roller 4 (see Fig. 1).

[0024] The details of the locked state are described below. If a first roller 4, which is arranged in the first direction of rotation L1 with respect to the pressure section 34, is wedged, the rotation of the output shaft 2 in the first direction of rotation L1 is restricted. Conversely, if a first roller 4, which is arranged in the second direction of rotation L2 with respect to the pressure section 34, is wedged, the rotation of the output shaft 2 in the second direction of rotation L2 is restricted.

[0025] As in Fig. As shown in Figure 3, the central surface 26 is formed in a linear shape orthogonal to the virtual line W4. In the present disclosure, the central surface 26 need not be linear, but can be formed in an arc shape around the central axis X.

[0026] Fig. 4 is an enlarged view showing part of Fig. Figure 3 is shown enlarged. A second roller 5 is arranged radially outside the guide surface 28. The second roller 5 is in contact with the guide surface 28. The circumferential position of the second roller (second rolling element) 5 is located between (in the middle) the first roller (first rolling element) 4 and the pressure section 34. In the following, the second roller (second rolling element) 5 can also be referred to as the middle object.

[0027] The guide surface 28 is located radially inwards, while extending circumferentially outwards. Therefore, as the second roller 5 moves circumferentially outwards along the guide surface 28, the magnitude of the movement increases radially inwards.

[0028] The shortest distance (see Fig. 4) The distance between the first roller 4 and the guide surface 28 in the locked state is designated H3. The shortest distance H3 is smaller than the diameter H2 (see Fig. 1) of the second roller 5. The center point X5 of the second roller 5 is located radially outside the line indicating the shortest distance H3. As the first roller 4 moves circumferentially outward, the shortest distance H3 moves radially inward (circumferentially outward), as indicated by the arrow Y in Fig. 4 is displayed. This means that the second roller 5 can move radially inwards (outwards in the circumferential direction).

[0029] The pressed surface 25 is a surface with which the first roller 4 comes into contact. The pressed surface 25 is linear from a radially inner end 25a to a radially outer end 25b. The outer end 25b is arranged circumferentially outwards with respect to a virtual line W5 drawn from the central axis X to the inner end 25a. That is, the pressed surface 25 is inclined circumferentially outwards.

[0030] A helical spring 50 is provided as an elastic element between the pressed surface 25 and the first roller 4. The helical spring 50 is arranged in a compressed state relative to its natural length. The first roller 4 is constantly pre-tensioned inwards in the circumferential direction by the helical spring 50. Therefore, even without the application of an external force to the output shaft 2, the first roller 4 is clamped between the inner circumferential surface 10 and the cam surface 27 (locked state).

[0031] A hole 51 is formed in the pressed surface 25. Part of the coil spring 50 is housed in the hole 51. When the first roller 4 moves circumferentially outwards, the coil spring 50 is housed in the hole 51, and the first roller 4 comes into contact with the pressed surface 25 (see Fig. 7). As in Fig. As shown in Figure 1, the hole 51 penetrates a pressed surface 25 and another recessed surface 23 on the back side of the pressed surface 25. That is, the hole 51 connects the inner sides of the recessed surfaces 23, which lie next to each other in the circumferential direction. A coil spring 50 preloads two first rollers 4.

[0032] As in Fig. As shown in Figure 4, the printing section 34 has a pair of lateral surfaces 35 that point outwards in the circumferential direction, an inner surface 36 that points radially inwards, and a pair of central object printing surfaces 37 that are formed at corner sections where the lateral surfaces 35 and the inner surface 36 intersect.

[0033] A side surface 35 has an inner surface 351, which is arranged radially inwards, and an outer side surface 352, which is arranged radially outwards with respect to a radially central section of the side surface 35. The outer side surface 352 is arranged circumferentially outwards, since it extends radially outwards and projects circumferentially outwards from the inner surface 351.

[0034] One in Fig. The virtual line W6 shown in section 4 is a straight line that is orthogonal to the virtual line W4 (see Fig. 3) runs. The inner surface 36 extends along the virtual line W6. The central object pressure surfaces 37 are linear. In a state where the pressure section 34 is located in the center circumferentially, the central object pressure surfaces 37 are in contact with the second rollers 5. When the pressure section 34 moves outward circumferentially, a central object pressure surface 37 presses against a second roller 5. The pressed second roller 5 is pressed between the first roller 4 and the guide surface 28.

[0035] The central object pressure surface 37 is oriented such that the pressed second roller 5 moves between the first roller 4 and the guide surface 28. The central object pressure surface 37 of the present embodiment is arranged such that it shifts radially outwards as it extends circumferentially outwards, and is inclined such that it intersects the virtual line W6.

[0036] Next, the operation of the power transmission device of the first embodiment will be described. First, the initial state of the power transmission device 100 (a state in which neither torque nor external force is applied) will be described.

[0037] As in Fig. As shown in Figure 3, a pair of first rollers 4 are pressed by coil springs 50 and moved inwards in the circumferential direction. The first roller 4 is clamped between the inner circumferential surface 10 and the cam surface 27. This means that the output shaft 2 is in the locked position in its initial state.

[0038] In the initial state, the side surfaces 35 of the printing section 34 do not touch the first rollers 4. The central object printing surfaces 37 of the printing section 34 touch the second rollers 5. The second roller 5 touches both the first roller 4 and the guide surface 28.

[0039] Next, a case is described in which, in the initial state, a torque is applied to the drive shaft body 31 (see Fig. 2) is applied to the power transmission device 100. The following description first describes a state in which no external force acts on the output shaft 2. The same process occurs in cases where the direction of the input torque is in the first direction of rotation L1 and in the second direction of rotation L2. Therefore, the following describes the case in which the direction of the torque is the first direction of rotation L1.

[0040] Fig. Figure 5 is a diagram illustrating an operating state of the power transmission device of the first embodiment, specifically a diagram at the time of the start of the torque input. As shown in Fig. 5 shown, when a torque in the first direction of rotation L1 is applied to the drive shaft body 31 (see Fig. 2) When a load A is applied in the first direction of rotation L1, it is transferred to the pressure section 34. The side surface 35 of the pressure section 34 is not in contact with the first roller 4 in the initial state. Therefore, at the beginning of the torque input, the pressure section 34 does not press against the first roller 4.

[0041] On the other hand, the pressure section 34 is in contact with the second roller 5. Therefore, the pressure section 34, with its central object pressure surface 37, presses against the second roller 5, and the second roller 5 accepts a load B from the pressure section 34. As a result, the second roller 5 is pressed between the first roller 4 and the guide surface 28. Then, the separate loads B1 and B2 act on the first roller 4 and the guide surface 28. When the load B1 acting on the first roller 4 is resolved, it contains, in addition to a radially outward-directed component, a component in the first direction of rotation, L1.

[0042] Fig. Figure 6 is a diagram illustrating an operating state of the power transmission device of the first embodiment, and is in particular a diagram at the time when a locked state is released. Therefore, as shown in Figure 6, the diagram shows the movement of the power transmission device of the first embodiment. Fig. Figure 6 shows the first roller 4 in the first direction of rotation L1, thereby releasing the state (locked state) of jamming between the inner circumferential surface 10 and the cam surface 27.

[0043] Meanwhile, the load B2 acting on the guide surface 28 comprises (see Fig. 5) A component in the second direction of rotation L2, and a torque in the second direction of rotation L2, acts on the output shaft 2. This torque is a load that moves the cam surface 27 relative to the first roller 4 in the second direction of rotation L2. From the foregoing, it follows that the load B2 includes the torque for unlocking and reduces the torque required for unlocking.

[0044] When the locked state is released, the pressure section 34 begins to move in the first direction of rotation L1. The second roller 5 begins to move radially inward along the guide surface 28. As the second roller 5 moves radially inward, the distance between the first roller 4 and the pressure section 34 decreases, and as shown in Fig. As shown in Figure 6, the side surface 35 of the pressure section 34 comes into contact with the first roller 4. Therefore, after the locked state is released, the first roller 4 accepts a load C from the pressure section 34 and moves in the first direction of rotation L1 while compressing the helical spring 50. Even after the locked state is released, the first roller 4 accepts the load B1 for a while (see Figure 6). Fig. 5) from the second roller 5.

[0045] Fig. Figure 7 is a diagram illustrating an operating state of the power transmission device of the first embodiment, and is in particular a diagram in a state in which a first roller is in contact with a pressing surface. As in Fig. As shown in Figure 7, the first roller 4 comes into contact with the pressed surface 25 when the first roller 4 moves to a certain degree in the first direction of rotation L1. After contact with the first roller 4, the pressure section 34 presses down on the pressed surface 25 via the first roller 4 (see arrows D1 and D2 in Figure 7). Fig. 7) As a result, the torque in the first direction of rotation L1 is transferred to the output shaft 2, and the output shaft 2 rotates in the first direction of rotation L1.

[0046] When the pressure section 34 presses on the pressed surface 25 via the first roller 4, the section of the side surface 35 in contact with the first roller 4 is not the inner surface 351, but the outer surface 352. The outer surface 352 is designed to run substantially parallel to the pressed surface 25. Therefore, a load D1 acting on the first roller 4 from the outer surface 352 is a normal vector of the pressed surface 25. Consequently, the loss of the torque transmitted from the pressure section 34 to the output shaft 2 is extremely low, and the torque is transmitted efficiently.

[0047] Since the pressed surface 25 is inclined, the first roller 4 is pressed against the pressed surface 25 and moves radially outwards (see arrow E in Fig. 7) Therefore, the distance between the inner circumferential surface 10 of the stationary part 1 and the first roller 4 is small.

[0048] As in Fig. As shown in Figure 7, the second roller 5 is separated from the central object pressure surface 37 when the radial inward movement of the second roller 5 increases. Thus, when the pressure section 34 presses on the pressed surface 25 via the first roller 4, the second roller 5 is not subjected to pressure by the pressure section 34.

[0049] Fig. Figure 8 is a diagram illustrating an operating state of the power transmission device of the first embodiment, specifically a diagram at the time when the first roller begins to move backward in the second direction of rotation. As shown in Fig. As shown in Figure 8, when the torque input to the drive shaft body 31 is released, the first roller 4 is pressed by the coil spring 50 and moves in the second direction of rotation L2 (see arrow F in Figure 8). Fig. 8) If the first pulley 4 moves to some extent in the second direction of rotation L2, it will, as in Fig. 3 shown, clamped between the cam surface 27 and the inner circumferential surface 10 (locked state).

[0050] Meanwhile, an oil film of constant thickness forms on the inner circumferential surface 10 of the stationary part 1. This means that the oil film is also present between the inner circumferential surface 10 of the stationary part 1 and the first roller 4. To lock the output shaft 2, the first roller 4 must cut through the oil film. If the thickness of the oil film between the inner circumferential surface 10 and the first roller 4 is large, there is a possibility that the first roller 4 will not be able to easily cut through the oil film, and thus the output shaft 2 will not be locked.

[0051] As in Fig. As shown in Figure 7, the distance between the inner circumferential surface 10 and the first roller 4 decreases when the first roller 4 is pressed against the pressed surface 25. This means that the thickness of the oil film between the inner circumferential surface 10 and the first roller 4 decreases. Therefore, according to the present embodiment, the first roller 4 slightly shears off the oil film located between the first roller 4 and the inner circumferential surface 10, thereby reliably locking the output shaft 2.

[0052] When the first roller 4 moves in the second direction of rotation L2, the second roller 5, which is in contact with the first roller 4, is also subjected to a load in the second direction of rotation L2. The second roller 5 is lifted radially outwards along the guide surface 28 (see arrow G in ). Fig. 8). This brings the second roller 5 into contact with the central object printing surface 37 of the printing section 34 (see Fig. 3).

[0053] Fig. Figure 9 is a diagram showing the point in time when the input of torque to the drive shaft (first direction of rotation) begins in a state where an external force (first direction of rotation) acts on the output shaft in the power transmission device of the first embodiment. The following describes a case in which an external force in the same direction (first direction of rotation L1) acts on the output shaft 2 at the point in time when the input of torque to the drive shaft 3 begins. The cause of the jerking is that when the locked state is released after the first rollers 4 have moved in the first direction of rotation L1, the output shaft 2 also rotates in the first direction of rotation L1 due to an external force (see arrow J1 in Figure 9). Fig. 9) and then the first rollers 4 are clamped again between the inner circumferential surface 10 and the cam surfaces 27.

[0054] As in Fig. As shown in Figure 9, a load B2 acts on the guide surface 28 when the pressure section 34 presses the second roller 5 between the first roller 4 and the guide surface 28 at the beginning of the torque input into the drive shaft 3. The load B2 includes a component in the second direction of rotation L2. Therefore, it prevents the output shaft 2 from rotating in the first direction of rotation L1. That is, it prevents the first rollers 4 from being clamped again between the inner circumferential surface 10 and the cam surfaces 27, thus preventing the occurrence of jerking.

[0055] Fig. Figure 10 is a diagram showing the point in time when the input of torque to the drive shaft (first direction of rotation) begins in a state where an external force (second direction of rotation) acts on the output shaft in the power transmission device of the first embodiment. On the other hand, as shown in Fig. As shown in Figure 10, the pressure section 34 moves the first roller 4 over the second roller 5 (see arrows B and B1) when the input of torque (first direction of rotation L1) into the drive shaft 3 begins in a state where an external force in the opposite direction (second direction of rotation L2) acts on the output shaft 2. The first roller 4 then moves to press the pressed surface 25 in the first direction of rotation L1. As a result, the output shaft 2 rotates in the first direction of rotation L1 (see arrow J2). Consequently, the first rollers 4 are not clamped between the inner circumferential surface 10 and the cam surfaces 27, thus preventing jerking.

[0056] Although the power transmission device 100 of the first embodiment was described above, the present disclosure is not limited to the example described in the first embodiment. A modification is described below in which a part of the power transmission device 100 of the first embodiment is modified. Only the differences from the power transmission device 100 described above are described in the following description. First modification

[0057] Fig. Figure 11 is an enlarged view showing one of the recessed surfaces of a force transmission device of a first modification. A force transmission device 100A of the first modification differs from that of the first embodiment in that the entire side surface 35A of the pressure section 34 is flat. That is, the outer surface 352, which projects circumferentially outwards from the inner surface 351, is not formed on the side surface 35A of the first modification.

[0058] In the first modification of the power transmission device 100A, the pressure section 34 also presses on the second roller 5 at the beginning of the torque input to the drive shaft 3 (see arrow B). Then, loads B1 and B2, which are separate from each other, act on the first roller 4 and the guide surface 28. Therefore, even if an external force acts on an output shaft 2 in the same direction as the torque applied to the drive shaft 3, the rotation of the output shaft 2 in the first direction of rotation L1 is suppressed. It follows from the above that, in the first modification of the power transmission device 100A, similar to the first embodiment, the first rollers 4 are prevented from being clamped again between the inner circumferential surface 10 and the cam surfaces 27, and the occurrence of jerking is avoided.Furthermore, according to the first modification, similar to the first embodiment, the torque required for unlocking can be reduced.

[0059] Fig. Figure 12 is a diagram illustrating a condition in which a pressure section presses on a pressure surface via a first roller in the power transmission device of the first modification. According to the power transmission device 100A of the first modification, the side surface 35A of the pressure section 34, which presses on the pressure surface via the first roller 4, is not parallel to the pressure surface 25. That is, a load K acting from the side surface 35A on the first roller 4 is not a normal vector of the pressure surface 25. Therefore, compared to the first embodiment, the loss of torque transmitted from the pressure section 34 to the output shaft 2 is large. Second modification

[0060] Fig. Figure 13 is an enlarged view showing one of the recessed surfaces of a power transmission device of a second modification. As in Fig. As shown in Figure 13, a power transmission device 100B of the second modification differs from the first modification in that the shape of a guide surface 28B is different. The guide surface 28B of the second modification is formed in an arc shape whose center lies on the central axis X. A virtual line W7 is an extension line of a load B2 acting on the guide surface 28B. In this second modification as well, the load B2 acting on the guide surface 28B includes a component in the second direction of rotation L2, and rotation in the first direction of rotation L1 by an output shaft 2 is suppressed. That is, in the second modification, the jerking hardly occurs. Furthermore, according to the second modification, similar to the first embodiment, the torque required for unlocking can be reduced.

[0061] Comparing the load B2 of the second modification (see Fig. 13) with the load B2 of the first embodiment (see Fig. 5) In the first embodiment, the load B2 is oriented circumferentially. This means that the torque acting on the output shaft 2 in the second direction of rotation L2 is greater in the first embodiment than in the second modification. Therefore, the first embodiment is preferable because jerking is less likely to occur and the torque required for unlocking can be reduced.

[0062] Fig. Figure 14 is a diagram illustrating a state in which a pressure section presses on a pressure surface via a second roller and a first roller in the force transmission device of the second modification. According to the guide surface 28B of the second modification, the second roller 5, which is pressed by the central object pressure surface 37, does not move radially inwards (does not move) even when moving circumferentially outwards. That is, since the distance between the pressure section 34 and the first roller 4 does not decrease, the side surface 35A does not come into contact with the first roller 4. Therefore, the pressure section 34 presses, as shown in Figure 14. Fig. 14 shows, via the second roller 5 to the first roller 4, thereby transmitting a torque to the output shaft 2. Third modification and fourth modification

[0063] Fig. Figure 15 is a partial cross-sectional view in which the area of ​​a pressed surface in a power transmission device of a third modification is shown enlarged. Fig. Figure 16 is an enlarged view showing one of the recessed surfaces of a power transmission device of a fourth modification. As in Fig. As shown in Figure 15, a power transmission device 100C of the third modification differs from the first embodiment in that a hole 51C does not penetrate. As shown in Figure 15, a power transmission device 100C of the third modification differs from the first embodiment in that it has no through hole 51C. Fig. As shown in Figure 16, a power transmission device 100D of the fourth modification differs from the first embodiment in that the coil springs 50 are not included. Even in the third and fourth modifications, as described above, the occurrence of jerking, similar to that in the first embodiment, is avoided.

[0064] The first to fourth modifications have been described above. In addition, three recessed surfaces 23 are formed on the output shaft 2 of the first embodiment; however, the number of recessed surfaces 23 is not specifically limited in the present disclosure. Although the pressure sections 34 and the first rollers 4 are separated from each other in the initial state in the first embodiment, the pressure sections 34 can bear against the first rollers 4 in the present disclosure. Accordingly, the first rollers 4 bear the load B1 exerted by the second rollers 5 (see Fig. 5 and others) and also take on a load from the pressure sections 34 to move circumferentially outwards, thereby releasing the locked state.

[0065] In the first embodiment, the example described uses a cylindrical roller as the rolling elements (first rolling element and second rolling element); however, the present disclosure may also use a sphere. Similarly, with respect to the middle object, the first embodiment described an example using the second roller (second rolling element) 5; however, the present disclosure may use a wedge body as the middle object, having a wedge surface that gradually narrows in the direction in which the wedge body is pressed through the pressure section 34 (see arrow B in Figure 1). Fig. 11) An example using the wedge body is described below in a fifth modification. Fifth modification

[0066] Fig. Figure 17 is a schematic diagram showing one of the recessed surfaces of the power transmission device of a fifth modification, viewed from the axial direction. A power transmission device 100E of the fifth modification differs from the first embodiment in that a wedge body 105 is used instead of the second roller (second rolling element) 5. The wedge body 105 is a square prism, which, viewed from the axial direction, has a square shape. Therefore, the wedge body 105 has four surfaces (first surface 111, second surface 112, third surface 113, and fourth surface 114).

[0067] The first surface 111 is oriented towards a printing section 34 and faces a central object pressure surface 37. In the fifth embodiment, as in Fig. As shown in Figure 17, a tiny gap is formed between the first surface 111 and the central object pressure surface 37; however, in the present disclosure, the first surface 111 can be in contact with the central object pressure surface 37. The second surface 112 is located on the back side of the first surface 111. The third surface 113 is in contact with a guide surface 28. The wedge body 105 moves as it slides on the guide surface 28 when it is pressed by the pressure section 34 (see arrow N in Figure 17). Fig. 17).

[0068] The fourth surface 114 is located on the back side of the third surface 113 and is in contact with the first roller (first rolling element) 4. The fourth surface 114 is not parallel to the third surface 113. The fourth surface 114 is inclined such that a distance Z (see Fig. 17) between the third surface 113 and the fourth surface 114, decreasing from the first surface 111 to the second surface 112. That is, the third surface 113 and the fourth surface 114 form wedge surfaces 110, which in the direction in which the wedge body is pressed through the pressure section 34 (see arrow N in Fig. 17), gradually becoming narrower.

[0069] According to the fifth modification described above, when the pressure section 34 moves, for example, in the first direction of rotation L1, the wedge body 105 receives a load from the pressure section 34 (see arrow N in Fig. 17) Accordingly, the wedge body 105 is pressed between the first roller 4 and the guide surface 28. As a result, similar to the first embodiment, loads N1 and N2, which serve to separate the first roller 4 and the guide surface 28 from each other, are exerted on them.

[0070] As described above, in the fifth embodiment, the use of the wedge body 105 also prevents the first roller 4 from being clamped again between the inner circumferential surface 10 and the cam surface 27, similar to the first embodiment, thus preventing the occurrence of jerking. Furthermore, according to the fifth embodiment, the torque required for unlocking can also be reduced, similar to the first embodiment.

[0071] Although the fifth embodiment was described above, the present disclosure is not limited with respect to the wedge body 105, which has the quadrilateral prism (a quadrilateral viewed from the axial direction) described in the fifth modification. In the present disclosure, it is sufficient to have the wedge surfaces 110 (third surface 113 and fourth surface 114). That is to say, the present disclosure can use a polygonal prism (polygon when viewed from the axial direction), such as a triangular prism (triangle when viewed from the axial direction) or a pentagonal prism (pentagon when viewed from the axial direction).Although the third surface 113 and the fourth surface 114, which form the wedge surfaces 110, are flat surfaces in the fifth modification, the third surface 113 and the fourth surface 114 only need to be flat in the direction in which the wedge body is pressed through the pressure section 34 (see arrow N in . Fig. 17), gradually becoming narrower. and the third surface 113 and the fourth surface 114 can be curved surfaces (arc-shaped when viewed from the axial direction).

[0072] Next, a drive unit 5000 is described, which includes the power transmission device 100 according to the first embodiment. Second embodiment

[0073] Fig. Figure 18 is a schematic diagram illustrating the configuration of a drive unit of a second embodiment. As in Fig. As shown in Figure 18, the drive unit 5000 comprises a motor 5001 and the power transmission device 100 described above. The motor 5001 is a device for generating torque. An output shaft (not shown) of the motor 5001 is connected to the drive shaft body 31 (in Figure 18). Fig. 18 not shown, see Fig. 2) connected to the power transmission device 100.

[0074] Such a drive unit 5000 is used, for example, for an electric pusher, a robotic arm, a lifting device, a transport robot, an electric cart, an electric bicycle, a mobility scooter, a trolley, a stroller, or the like. In other words, an electric pusher or the like is connected to the output shaft body 21 of the power transmission device 100. When the motor 5001 of the drive unit 5000 is driven, the torque is transmitted to the electric pusher or the like via the power transmission device 100.

[0075] Even if an external force acts on the electric slide or the like, and this external force is transmitted to the output shaft 2, the output shaft 2 does not rotate. Therefore, the electric slide connected to the output shaft 2 is not rotated, moved, or changed in position by the external force. Consequently, according to the drive unit 5000, no electromagnetic brake is required to restrict rotation due to an external force, thus reducing the power required.

[0076] The second embodiment has been described above. Although the drive unit 5000 of the second embodiment comprises the power transmission device 100 described in the first embodiment, the configuration in the present disclosure may include the power transmission devices described in the first to fifth modifications.

[0077] Fig. Figure 19 is a schematic diagram illustrating the configuration of a drive unit of a sixth modification. Although the drive unit 5000 of the second embodiment comprises the motor 5001 and the power transmission device 100, the drive unit in the present disclosure can be a drive unit 5000A of the sixth modification, comprising the motor 5001, the power transmission device 100, a speed reducer 5002, and a sensor 5003 that detects the angle of rotation or similar of an output shaft of the motor 5001, as shown in Fig. Figure 19 shows the speed reducer 5002, a device for increasing torque. In the sixth modification, an electric slide or similar device is connected to an output shaft 5004 of the speed reducer 5002.

[0078] Although in the sixth modification the torque generated by the motor 5001 is transmitted to the power transmission device 100 and the speed reducer 5002 in the sequence mentioned, the present disclosure can be modified with respect to the arrangement of the power transmission device 100 and the speed reducer 5002, and the torque can be transmitted to the speed reducer 5002 and the power transmission device 100 in the sequence mentioned.

[0079] It should be noted that the present disclosure may include combinations of the following configurations. (1) A power transmission device comprising the following: a ring-shaped fixed part with an inner circumferential surface; an output shaft with an outer circumferential surface facing the inner circumferential surface and a recessed surface set back radially inwards from the outer circumferential surface; a drive shaft with a pressure section received in the recessed area; a pair of first rolling elements, which are received in the recessed surface and arranged circumferentially opposite the pressure section; and a pair of medium objects, each of which is arranged between the corresponding first rolling element and the pressure section, wherein the recessed area includes: a base surface that extends circumferentially and faces the inner circumferential surface in a radial direction; and a pair of pressed surfaces extending radially outwards from opposite circumferential ends of the base surface, the floor area comprises: a pair of cam surfaces, each having the corresponding first rolling element arranged on a radially outer side; and a pair of guide surfaces, each featuring the corresponding central object located on a radially outer side, a distance between each cam surface and the inner circumferential surface gradually increases with increasing proximity to the corresponding pressing surface, a distance between a section of each cam surface that is closer to the corresponding guide surface and the inner circumferential surface is smaller than a diameter of each first rolling element, a distance between a section of each cam surface that is closer to the corresponding pressure surface and the inner circumferential surface is greater than the diameter of each first rolling element, the middle object is clamped between the first rolling element, the guide surface and the pressure section, The pressure section presses the central object between the first rolling element and the guide surface when the pressure section moves circumferentially outwards from a state in which the pressure section is located circumferentially in a central section of the recessed surface, and The middle object is either a second rolling element with a smaller diameter than the first rolling element or a wedge body with a wedge surface that gradually tapers in the direction in which the wedge body is pressed through the pressure section. (2) Power transmission device according to (1), wherein the guide surface is arranged radially inwards near the cam surface. (3) Power transmission device according to (2), wherein the printed section includes side surfaces, each pointing outwards in the circumferential direction, and if at least a part of each side surface presses on the corresponding pressure surface via the corresponding first rolling element, the part of the side surface is parallel to the corresponding pressure surface. (4) Power transmission device according to (1), wherein Each of the guide surfaces is formed in an arc shape around a central axis of the inner circumferential surface. (5) Power transmission device according to any of the specifications (1) to (4), wherein Each of the pressing surfaces is inclined outwards in the circumferential direction, with an outer end arranged in the radial direction of the pressing surface in the circumferential direction outside a virtual line extending from a central axis of the inner circumferential surface to an inner end in the radial direction of the pressing surface. (6) Power transmission device according to any of (1) to (5), further comprising: elastic bodies, each arranged between the pressure surface and the corresponding first rolling element, pre-tension the corresponding first rolling element in the direction of the pressure section. (7) Drive unit comprising: an engine; and the power transmission device according to one of (1) to (6), wherein the torque generated by the engine is transferred to the drive shaft. [List of reference symbols] 1. FIXED PART 2. Output shaft 3 DRIVE SHAFT 4 FIRST ROLE (FIRST ROLE ELEMENT) 5 SECOND ROLLER (SECOND ROLLING ELEMENT, CENTER OBJECT) 10 INNER CIRCUMFERENCE 20 INNER RING SECTION 23 RECESSED AREA 24 LOWER SURFACE 25 COMPRESSED SURFACE 26 CENTRAL AREA 27 CAM SURFACE 28, 28B GUIDE AREA 30 TORQUE TRANSMISSION SECTION 34 PRINT SECTION 35, 35A SIDE SURFACE 37 CENTER OBJECT PRINTING AREA 50 screw springs 51, 51C HOLE 100, 100A, 100B, 100C, 100D, 100E POWER TRANSMISSION DEVICE 105 WEDGE BODY (MEDIUM OBJECT) 110 WEDGE SURFACE 113 THIRD AREA 114 FOURTH AREA 351 INNER SURFACE 352 EXTERIOR SURFACE 5000, 5000A DRIVE UNIT QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 4621156

[0004]

Claims

[1] Power transmission device comprising: a ring-shaped fixed part with an inner circumferential surface; an output shaft with an outer circumferential surface facing the inner circumferential surface and a recessed surface set back radially inwards from the outer circumferential surface; a drive shaft with a pressure section received in the recessed area; a pair of first rolling elements, which are received in the recessed surface and arranged circumferentially opposite the pressure section; and a pair of medium objects, each of which is arranged between the corresponding first rolling element and the pressure section, wherein the recessed area includes: a base surface that extends circumferentially and faces the inner circumferential surface in a radial direction; and a pair of pressed surfaces extending radially outwards from opposite circumferential ends of the base surface, the floor area comprises: a pair of cam surfaces, each having the corresponding first rolling element arranged on a radially outer side; and a pair of guide surfaces, each featuring the corresponding central object located on a radially outer side, a distance between each cam surface and the inner circumferential surface gradually increases with increasing proximity to the corresponding pressing surface, a distance between a section of each cam surface that is closer to the corresponding guide surface and the inner circumferential surface is smaller than a diameter of each first rolling element, a distance between a section of each cam surface that is closer to the corresponding pressure surface and the inner circumferential surface is greater than the diameter of each first rolling element, the middle object is clamped between the first rolling element, the guide surface and the pressure section, The pressure section presses the central object between the first rolling element and the guide surface when the pressure section moves circumferentially outwards from a state in which the pressure section is located circumferentially in a central section of the recessed surface, and The middle object is either a second rolling element with a smaller diameter than the first rolling element or a wedge body with a wedge surface that gradually tapers in the direction in which the wedge body is pressed through the pressure section. [2] Power transmission device according to claim 1, wherein the guide surface is arranged radially inwards near the cam surface. [3] Power transmission device according to claim 2, wherein the printed section includes side surfaces, each pointing outwards in the circumferential direction, and if at least a part of each side surface presses on the corresponding pressure surface via the corresponding first rolling element, the part of the side surface is parallel to the corresponding pressure surface. [4] Power transmission device according to claim 1, wherein each of the guide surfaces is formed in an arc shape around a central axis of the inner circumferential surface. [5] Power transmission device according to one of claims 1 to 4, wherein each of the pressing surfaces is inclined outwards in the circumferential direction, wherein an outer end is arranged in the radial direction of the pressing surface in the circumferential direction outside a virtual line extending from a central axis of the inner circumferential surface to an inner end in the radial direction of the pressing surface. [6] Power transmission device according to any one of claims 1 to 4, further comprising: elastic bodies, each arranged between the pressure surface and the corresponding first rolling element, pre-tension the corresponding first rolling element in the direction of the pressure section. [7] Drive unit comprising: an engine; and the power transmission device according to one of claims 1 to 4, wherein the torque generated by the engine is transferred to the drive shaft.

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