Shift barrel for transmission

Abstract

To provide a shift barrel 1 used for a transmission for a vehicle, etc. that in the case where an end part 4 disengaging with a link mechanism 6 for rotating the shift barrel is formed as a separate part from a body portion 2 with a groove 3 formed thereon and engaging with a shift fork and is configured to connect with the body portion, enables rotation of the body portion even if a bearing supporting an end part of the separate part becomes unable to rotate and can hold a shift stage changeover function.SOLUTION: A shift barrel for a transmission includes: a body portion in which a groove engaging with a shift fork is formed on the surface; and first and second end parts each rotatably supported by a bearing at both ends of the body portion. The first end part 5 engages with a link mechanism for rotating the shift barrel and is formed integrally with the body portion. The second end part 4 is formed as a separate part from the body portion and is connected to the end on the opposite side to the first end part of the body portion so as to be slidable in the rotating direction relative to the body portion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a structure of a shift barrel of a transmission. [Background technology]

[0002] In the case of a type in which a shift barrel (or a shift drum) is used in a transmission for a vehicle such as an automobile, when changing gear stages, a cylindrical shift barrel is rotated by an actuator, and a shift fork is displaced in the axial direction of the gear train along a groove formed on the surface of the shift barrel, thereby changing the position of the gear. Various structures of such a shift barrel have been proposed. For example, Patent Document 1 proposes that the end of the shift drum on the side where a rotational force is input is supported by a bearing member having an inner diameter substantially equal to the outer diameter of the shift drum, and that the end is provided with a shaft portion that is coaxial with the shift drum and has a smaller diameter than the shift drum, and that a mechanism for rotating the shift drum is connected to the end of the shaft portion to reduce the size of the transmission. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication 2019-178753 Summary of the Invention [Problem to be solved by the invention]

[0004] Regarding the shift barrel in the above-mentioned transmission, various configurations have been considered to reduce its weight. One of such configurations is to make the wall thickness of the shift barrel as thin as possible, while increasing its diameter and preventing the cross-sectional area from becoming too small, thereby suppressing the decrease in strength due to the weight reduction. Increasing the diameter of the shift barrel in this way is also advantageous in that the amount of cutting can be reduced when cutting the surface of a round bar material to form a groove in the work of the shift barrel. The work of making the shift barrel into a cylindrical shape is performed by boring the inside of the round bar material by drilling a hole from one end of the round bar material using a drill, so the adjustment of the wall thickness can be achieved by appropriately selecting the outer diameter of the drill.

[0005] Even when adopting a configuration in which the diameter of the shift barrel is increased as described above, it is preferable that the dimensions of the bearings that rotatably support both ends of the shift barrel are as small as possible. Therefore, even in a design in which the diameter of the shift barrel is increased, it is possible to make the diameter of the ends supported by the bearings smaller than that of the portion between them. In this case, since the inside of the round bar material is hollowed out by inserting a drill from one end as described above, it is necessary to prepare at least one of the ends of the shift barrel machined to a small diameter as a separate body and connect it to the one machined to a large diameter (the shift barrel main body part). In other words, when the diameter of the shift barrel is increased without increasing the dimensions of the bearings that support the ends of the shift barrel, a method is adopted in which at least one end formed to a small diameter is divided and prepared and connected to the shift barrel main body part formed to a large diameter. In this regard, the shift barrel has a groove that engages with the shift fork formed on its surface as described above, and for the gear shifting operation, one end is rotated by an actuator to displace the shift fork. Therefore, one of the two ends of the shift barrel supported by the bearing engages with the link mechanism connected to the actuator and has the function of converting the displacement force from the actuator into rotation of the shift barrel, so the end engaged with the link mechanism is preferably formed integrally with the shift barrel body in which the groove engaged with the shift fork is formed (in a configuration in which the end engaged with the link mechanism is formed separately and connected to the shift barrel body, if the connection part slips, the displacement from the actuator will not be transmitted to the rotation of the shift barrel.) Therefore, it is preferable that the end formed separately from the shift barrel body be the end on the side not engaged with the link mechanism.

[0006] Incidentally, as described above, when the shift barrel body and the end portion not engaged with the link mechanism are formed separately and connected, the end portion only needs to be supported by a bearing to rotatably support the shift barrel body, so there is no need to precisely adjust the angular position of the end portion and the end portion may be slidable in the rotational direction relative to the shift barrel body. In this way, when the end portion of the separate body is slidable in the rotational direction relative to the shift barrel body, even if the bearing supporting the end portion is damaged and cannot rotate, the shift barrel body can rotate following the link mechanism, and the gear shifting function is maintained, which is advantageous. This knowledge is utilized in the present invention.

[0007] Thus, the main object of the present invention is to provide a shift barrel used in a transmission of a vehicle or the like, in which the end portion not engaged with the link mechanism for rotating the shift barrel is formed separately from the shift barrel main body portion having a groove formed therein that engages with the shift fork, and is configured to be connected to the shift barrel main body portion, such that by connecting the shift barrel main body portion and the separate end portion so as to be slidable in the rotational direction around its axial direction, the shift barrel main body portion can rotate even if the bearing supporting the separate end portion becomes unable to rotate, thereby enabling the gear shifting function to be maintained. [Means for solving the problem]

[0008] According to the present invention, the above object is achieved by a shift barrel of a transmission, the shift barrel including a main body portion having a groove formed on its surface for engaging with a shift fork, and first and second ends rotatably supported by bearings at both ends of the main body portion, the first end engaging with a link mechanism for rotating the shift barrel and being integrally formed with the main body portion, and the second end being formed separately from the main body portion and being connected to the end of the main body portion opposite the first end so as to be slidable in the rotational direction relative to the main body portion.

[0009] In the above configuration, the "transmission" may be any type of transmission that employs a shift barrel mounted on a vehicle such as an automobile. The "shift barrel" may be a cylindrical member in a normal manner, with a groove formed on its surface to engage with a shift fork, and one end (first end) of the shift barrel engaged with a link mechanism connected to an actuator that generates a force to rotate the shift barrel when changing gears. The bearings that rotatably support the first and second ends may be any bearings that are normally used in this field. The connection between the main body portion and the second end portion that is slidable in the rotational direction may be in any manner, but typically may be in a state in which the outside of the second end portion is fitted into the inside of the open end of the main body portion.

[0010] According to the above configuration, the second end not engaged with the link mechanism is formed separately from the main body and the first end of the shift barrel, and is connected to be slidable in the rotational direction, so that even if the bearing rotatably supporting the second end becomes unable to rotate, the main body in which the groove engaging with the shift fork is formed can rotate, so that even if the bearing rotatably supporting the second end breaks down, the gear shift can be changed and the vehicle can be kept in a running state. In addition, when the shift barrel is assembled into the transmission, the second end does not require precise angular alignment, and there is no need for a jig for this purpose, which is advantageous.

[0011] In the above configuration, if the connection between the main body portion and the second end portion is adjusted so that the sliding resistance between them is greater than the rotational resistance of the bearing under normal conditions, then even if the main body portion is able to rotate in the event of a bearing failure, the force or time required for rotation will increase, and by detecting this increase in force or time, it is possible to detect a bearing failure, which is advantageous. Effect of the Invention

[0012] According to the above-mentioned configuration of the shift barrel of the present invention, by connecting the main body of the shift barrel and the separate end portion so as to be slidable in the rotational direction around the axis, even if the bearing supporting the separate end portion becomes unable to rotate, the main body is maintained in a rotatable state, and the gear shifting function can be maintained. As explained in "Problems to be Solved by the Invention", the configuration of the shift barrel of the present invention is advantageously applied when the first and second ends are formed to have a smaller diameter than the main body portion when the diameter of the main body portion is increased while the thickness of the main body portion is reduced, and in that case, the weight of the shift barrel can be more effectively reduced.

[0013] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view taken along the axial direction of a shift barrel according to the present embodiment. [Diagram 2] FIG. 2(A) is a schematic cross-sectional view along the axial direction of the main body portion of the shift barrel according to this embodiment, FIG. 2(B) is a schematic diagram of a link mechanism connected to the shift barrel, and FIG. 2(C) is a schematic cross-sectional view along the axial direction of an end portion formed separately from the main body portion of the shift barrel according to this embodiment. [Explanation of symbols]

[0015] 1...shift barrel, 2...shift barrel main body, 3...shift fork engagement groove, 4...separate end (second end), 5...main body end (first end), 6...link mechanism, 7...center bolt, 8...positioning pin, 9, 10...bearing BEST MODE FOR CARRYING OUT THEINVENTION

[0016] The present invention will now be described in detail with reference to some preferred embodiments thereof with reference to the accompanying drawings, in which like reference numerals indicate like parts.

[0017] Shift barrel configuration The shift barrel according to this embodiment is used in any transmission (not shown) of a type that employs a shift barrel in a vehicle such as an automobile. Referring to FIG. 1, the shift barrel 1 has a main body portion 2 having a groove 3 formed on its outer surface to engage with a shift fork (not shown) in a normal manner, and ends 4 and 5 rotatably supported by bearings 9 and 10 at both ends. Of these two ends, the end 5 on the left side in the figure is fixedly connected via a bolt 7 and a positioning pin 8 to a link mechanism 6 that transmits a rotational force that rotates the shift barrel 1 around an axis ax to change the gear stage. The end 5 is integrally molded with the main body portion 2 in which the groove 3 is formed, so that the rotation given from the link mechanism 6 is reliably transmitted to the main body portion 2. On the other hand, the end 4 on the right side in the figure is formed as a separate body from the main body portion 2 (see FIG. 2(C)) in this embodiment, as will be described later, and is connected to the main body portion 2. In this regard, as can be seen from the drawing, in the shift barrel 1, the groove 3 on the cylindrical outer surface has the function of displacing the shift fork, so in order to reduce weight, the main body portion 2 is formed into a hollow cylinder by hollowing out its interior 2a from one end. Thus, the end portion 4 formed as a separate body may be connected to the main body portion 2 by being inserted into the open end 2b.

[0018] In the above-mentioned configuration of the shift barrel 1, the end portion 5 connected to the link mechanism 6 and integrally formed with the main body portion 2 is required to be precisely aligned since the gear shift is performed according to the position in the rotation direction, but the end portion 4 not connected to the link mechanism only needs to hold the shift barrel 1 with a bearing, so strict alignment is not required. Rather, if the end portion 4 is rotatable with respect to the main body portion 2, the main body portion 2 can rotate even if the bearing 10 breaks down and becomes unable to rotate, and the gear shift function is maintained. Thus, in this embodiment, the end portion 4 is slidably connected to the main body portion 2, and the rotatable state of the shift barrel 1 is maintained even if the bearing 10 breaks down.

[0019] The sliding resistance at the abutting portion 4a between the main body portion 2 and the end portion 4 may be adjusted so as to be higher than the rotation resistance of the bearing 10 when it is normal. As a result, when the bearing 10 fails, the main body portion 2 slides against the end portion 4, and the force or time required to rotate the main body portion 2 increases more than usual, making it possible to detect an abnormality in the bearing 10.

[0020] In the above configuration, the main body portion 2 and the end portion 4 are formed separately, so that the diameter of the main body portion 2 can be increased without increasing the dimensions of the bearing. As explained in the "Summary of the Invention" section, one method of reducing the weight of the shift barrel 1 while maintaining its strength is to increase the diameter while reducing the thickness of the main body portion. However, even in this case, it is preferable not to increase the dimensions of the bearing, and in order to do so, it is necessary not to increase the diameter of the end portion surrounded by the bearing. In this regard, if one end portion 4 of both ends is formed separately and connected to the main body portion as in this embodiment, the diameter ra of the main body portion 2 can be increased while the diameter rb of the separate end portion 4 can be made smaller than that of the main body portion, so that the weight of the shift barrel 1 can be reduced.

[0021] Shift barrel assembly In the shift barrel of this embodiment, as shown in FIG. 2(A), the main body portion 2 and the end portion 5 are integrally formed, and as shown in FIG. 2(C), the end portion 4 is formed as a separate body from the main body portion 2. In the molding process, the end portion 4 may be formed by cutting the surface of a round bar material and boring the inside by drilling a hole. In the assembly process, the separate end portion 4 is fitted to the open end 2b of the main body portion 2 so as to be slidable in the rotational direction, and then, in a normal manner, the shift barrel 1 is assembled into the transmission while the end portion 4 and the end portion 5 are fitted into bearings, and then, the link mechanism 6 as shown in FIG. 2(B) may be fixedly connected to the end portion 5 of the main body portion 2 via a bolt 7 and a positioning pin 8 so as not to be displaced in the rotational direction relative to the main body portion 2.

[0022] The above description has been given in relation to the embodiment of the present invention, but it will be apparent to those skilled in the art that many modifications and changes can be easily made thereto, and that the present invention is not limited to the embodiment exemplified above, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A shift barrel for a transmission, comprising: a main body portion having a groove formed on its surface for engaging with a shift fork; and first and second ends rotatably supported by bearings at both ends of the main body portion, the first end engaging with a link mechanism for rotating the shift barrel and being formed integrally with the main body portion, and the second end being formed separately from the main body portion, the shift barrel being connected at an end of the main body portion opposite the first end to be slidable in a rotational direction relative to the main body portion.

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