Clutch structure

A clutch structure includes a rotary shaft, a cylinder, and a clutch. An outer peripheral fitting surface of the rotary shaft includes an engagement groove. The engagement groove extends in an axial direction along a rotation axis of the rotary shaft. A clutch cover of the clutch includes an engagement protrusion. The engagement protrusion protrudes inwardly in a radial direction with respect to the rotation axis from an inner peripheral surface of an annular inner edge of the clutch cover. The engagement protrusion engages in the engagement groove to hinder the clutch cover from rotating about the rotation axis relative to the rotary shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2017-065811, filed Mar. 29, 2017, entitled “Clutch Structure.” The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to a clutch structure.

2. Description of the Related Art

In the related art, there is known a clutch structure including a rotary shaft that is rotatably disposed, a cylindrical member that is rotatably disposed on the outside of the rotary shaft in such a manner that the cylindrical member and the rotary shaft are on the same axis, and a clutch portion that switches between a disconnected state in which the rotary shaft is allowed to rotate relative to the cylindrical member and a connected state in which rotation of the rotary shaft relative to the cylindrical member is hindered (see, for example, Japanese Unexamined Patent Application Publication No. 2014-181744).

A clutch portion of a clutch structure described in Japanese Unexamined Patent Application Publication No. 2014-181744 includes a clutch piston that is disposed at the outer periphery of an input shaft, which serves as a rotary shaft, in such a manner as to be capable of sliding in an axial direction and a clutch cover that includes an annular inner edge portion fixed to the outer periphery of the input shaft in such a manner as to form an oil chamber, to which a hydraulic fluid is supplied, between the clutch cover and the clutch piston.

In the related art, a known example of such a method of fixing a clutch cover onto a rotary shaft is a method of fixing a clutch cover onto a rotary shaft by fitting an annular inner edge portion of the clutch cover onto the outer periphery of the rotary shaft and accommodating a circlip (also referred to as a retaining ring) into an annular clip groove. In this case, a space between the rotary shaft and the clutch cover is sealed by an O-ring in order to hermetically seal an oil chamber.

SUMMARY

According to one aspect of the present invention, a clutch structure includes a rotary shaft that is rotatably supported, a cylindrical member that is rotatably disposed on the outside of the rotary shaft in such a manner that the cylindrical member and the rotary shaft are on the same axis, and a clutch portion that switches between a disconnected state in which the cylindrical member is allowed to rotate relative to the rotary shaft and a connected state in which rotation of the cylindrical member relative to the rotary shaft is hindered. The clutch portion includes a clutch piston that is disposed at an outer periphery of the rotary shaft in such a manner as to be capable of sliding in an axial direction, a clutch cover that is fixed to the outer periphery of the rotary shaft in such a manner as to form, between the clutch cover and the clutch piston, an oil chamber to which a hydraulic fluid used for causing the clutch piston to operate is supplied, and a seal member that hermetically seals a space between the rotary shaft and the clutch cover. The clutch cover includes an annular inner edge portion that is fitted onto the outer periphery of the rotary shaft in a fitting direction, which is parallel to the axial direction, and a cover-side contact surface that has a ring-like shape and that rises outward in a radial direction from an end edge of the annular inner edge portion, the end edge facing the fitting direction. The rotary shaft has an outer peripheral fitting surface onto which the annular inner edge portion of the clutch cover is fitted on an outside of the outer peripheral fitting surface, a shaft-side contact surface that rises outward in the radial direction from an end edge of the outer peripheral fitting surface, the end edge facing the fitting direction, and that comes into contact with the cover-side contact surface, an annular clip groove in which a circlip is accommodated, the circlip fixing in place the annular inner edge portion of the clutch cover, which is fitted to the outer peripheral fitting surface and which is in contact with the shaft-side contact surface, by pressing the annular inner edge portion from a side opposite to a side on which the shaft-side contact surface is present, and an engagement groove that is formed in the outer peripheral fitting surface along the axial direction. The clutch cover further includes an engagement protruding portion that protrudes inwardly in the radial direction from an inner peripheral surface of the annular inner edge portion and that engages in the engagement groove in such a manner as to hinder the clutch cover from rotating relative to the rotary shaft.

According to another aspect of the present invention, a clutch structure includes a rotary shaft, a cylinder, and a clutch. The rotary shaft is rotatable about a rotation axis. The rotary shaft includes an outer peripheral fitting surface, a shaft-side contact surface, and an annular clip groove. The outer peripheral fitting surface is provided about the rotation axis and includes an engagement groove extending in an axial direction along the rotation axis. The shaft-side contact surface extends outwardly in a radial direction with respect to the rotation axis from an end edge of the outer peripheral fitting surface in the axial direction. The annular clip groove is provided in an outer periphery of the rotary shaft about the rotation axis and extends in a peripheral direction with respect to the rotation axis such that the outer peripheral fitting surface is between the shaft-side contact surface and the annular clip groove in the axial direction. A circlip is mounted in the annular clip groove. The cylinder is provided on an outside of the rotary shaft in the radial direction. The clutch is to switch between a disconnected state in which the cylinder rotates about the rotation axis relative to the rotary shaft and a connected state in which rotation of the cylinder about the rotation axis relative to the rotary shaft is hindered. The clutch includes a clutch piston and a clutch cover. The clutch piston is provided at the outer periphery of the rotary shaft to be slidable in the axial direction. The clutch cover is provided at the outer periphery of the rotary shaft such that an oil chamber is defined between the clutch cover and the clutch piston. A hydraulic fluid is to be supplied to the oil chamber to slidably move the clutch piston in the axial direction. The clutch cover includes an annular inner edge, a cover-side contact surface, an engagement protrusion, and a packing. The annular inner edge is fitted onto the outer peripheral fitting surface of the rotary shaft such that the annular inner edge is provided on an outside of the outer peripheral fitting surface of the rotary shaft in the radial direction. The circlip presses the annular inner edge in a fitting direction to fix the annular inner edge in place in the axial direction. The fitting direction is one direction from the annular clip groove to the shaft-side contact surface in the axial direction. The cover-side contact surface has a ring shape and extends outwardly in the radial direction from an end edge of an inner peripheral surface of the annular inner edge in the fitting direction. The cover-side contact surface is in contact with the shaft-side contact surface in the axial direction. The engagement protrusion protrudes inwardly in the radial direction from the inner peripheral surface of the annular inner edge. The engagement protrusion engages in the engagement groove to hinder the clutch cover from rotating about the rotation axis relative to the rotary shaft. The packing hermetically seals between the rotary shaft and the clutch cover.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present disclosure will be described below with reference to the drawings. As illustrated inFIG. 1anFIG. 2, a clutch structure1according to the present embodiment is used in, for example, a transmission mounted on an automobile and includes a rotary shaft2that is rotatably supported, an outer drum3serving as a cylindrical member (a cylinder) that is rotatably disposed on the outside of the rotary shaft2in such a manner that the outer drum3and the rotary shaft2are on the same axis, and a clutch portion4(a clutch) that is interposed between the rotary shaft2and the outer drum3.

The clutch portion4switches between a disconnected state in which the rotary shaft2is allowed to rotate relative to the outer drum3and a connected state in which rotation of the rotary shaft2relative to the outer drum3is hindered. Hindering the relative rotation between the outer drum3and the rotary shaft2implies that rotation of the outer drum3and rotation of the rotary shaft2are synchronized with each other.

The clutch portion4includes a clutch piston5that is disposed at the outer periphery of the rotary shaft2in such a manner as to be capable of sliding in an axial direction and a clutch cover6that is fixed to the outer periphery of the rotary shaft2. The clutch cover6forms an oil chamber7between the clutch cover6and the clutch piston5, and a hydraulic fluid that is used for causing the clutch piston5to operate is supplied to the oil chamber7. In order to form the oil chamber7, O-rings8aand8b(packing) each of which serves as a seal member are disposed between the rotary shaft2and the clutch cover6.

The following components are disposed in the outer drum3: an inner hub9that is fixed to the rotary shaft2in such a manner as to be capable of rotating relative to the outer drum3and to be concentric with the outer drum3, a plurality of outer discs10that are disposed on the inner peripheral surface of the outer drum3in such a manner as to rotate integrally with one another, a plurality of inner plates11that are disposed on the outer peripheral surface of the inner hub9in such a manner as to rotate integrally with one another, and the above-mentioned clutch piston5that generates friction between the outer discs10and the inner plates11by pressing the outer discs10and that synchronizes rotation of the outer drum3and rotation of the inner hub9with each other.

The clutch cover6includes an annular inner edge portion (an annular inner edge)12that is fitted onto the outer periphery of the rotary shaft2in a fitting direction, which is parallel to the axial direction, and a cover-side contact surface13that has a ring-like shape and that rises outward in a radial direction from an end edge of the annular inner edge portion12, the end edge facing the fitting direction.

The rotary shaft2has an outer peripheral fitting surface14that has a ring-like shape, a shaft-side contact surface15, an annular clip groove (a circlip groove)17, and engagement grooves18. The annular inner edge portion12of the clutch cover6is fitted onto the outside of the outer peripheral fitting surface14. The shaft-side contact surface15rises outward in the radial direction from an end edge of the outer peripheral fitting surface14, the end edge facing the fitting direction, and comes into contact with the cover-side contact surface13. A circlip16that fixes the clutch cover6to the rotary shaft2is accommodated in the annular clip groove17. The engagement grooves18are formed in the outer peripheral fitting surface14along the axial direction. Note that the fitting direction is one way direction of the axial direction from the annular clip groove17to the shaft-side contact surface15.

The circlip16fixes in place the annular inner edge portion12of the clutch cover6, which is fitted to the outer peripheral fitting surface14and which is in contact with the shaft-side contact surface15, by pressing the annular inner edge portion12against the outer peripheral fitting surface14and the shaft-side contact surface15from the side opposite to the side on which the shaft-side contact surface15is present.

FIG. 3illustrates the state of the clutch cover6when viewed from the outside in the axial direction, andFIG. 4is a perspective view of a principal portion of the clutch cover6. As illustrated inFIG. 3andFIG. 4, the clutch cover6further includes engagement protruding portions (engagement protrusions)19that protrude inwardly in the radial direction from the inner peripheral surface of the annular inner edge portion12and each of which engages in a corresponding one of the engagement grooves18in such a manner as to hinder the clutch cover6from rotating relative to the rotary shaft2.

Recesses20that prevent the circlip16from coming into contact with the clutch cover6are each formed in a region of the annular inner edge portion12of the clutch cover6in which a corresponding one of the engagement protruding portions19is present, the region extending in the circumferential direction (the peripheral direction with respect to the axis), or in a region of the annular inner edge portion12including the above-mentioned region extending in the circumferential direction.

When mounting the clutch cover6onto the rotary shaft2, in a state where the O-ring8bis accommodated in a corresponding one of annular grooves formed in the outer periphery of the rotary shaft2, the clutch cover6is moved with respect to the rotary shaft2from the side opposite to the side on which the clutch piston5is disposed while the clutch cover6is in a position in which the recesses20of the clutch cover6face the side opposite to the side on which the clutch piston5is disposed, and the annular inner edge portion12of the clutch cover6is fitted onto the outside of the outer peripheral fitting surface14of the rotary shaft2.

When the above fitting operation is performed, the positional relationship between the clutch cover6and the rotary shaft2in the circumferential direction is adjusted in such a manner that the engagement protruding portions19of the clutch cover6are fitted into the corresponding engagement grooves18of the rotary shaft2. In addition, the clutch cover6is moved for performing the fitting operation until the cover-side contact surface13comes into contact with the shaft-side contact surface15. In this case, the O-ring8bis crushed by a corresponding portion of the inner peripheral surface of the clutch cover6, and as a result, a space between the rotary shaft2and the clutch cover6is hermetically sealed.

Subsequently, the circlip16is inserted into the annular clip groove17of the rotary shaft2. As a result, the annular inner edge portion12of the clutch cover6is pressed against and fixed onto the shaft-side contact surface15, and the mounting of the clutch cover6is completed.

When the clutch structure1is caused to operate, since the engagement protruding portions19of the clutch cover6engage in the corresponding engagement grooves18of the rotary shaft2, relative rotation between the rotary shaft2and the clutch cover6is hindered. This prevents wear of the O-ring8b, which is disposed between the rotary shaft2and the clutch cover6.

In addition, even in the case where a stress is concentrated at a portion of the annular clip groove17due to uneven distribution of the pressure between contact surfaces of the circlip16and the annular clip groove17, in which the circlip16is accommodated, generated as a result of an end gap22of the circlip16forming a step or being twisted, the circlip16does not rotate relative to the annular clip groove17, and thus, a fatigue failure is prevented from occurring in the annular clip groove17.

A load from the clutch cover6in the axial direction is applied from the annular inner edge portion12to the inner wall of the annular clip groove17of the rotary shaft2, the inner wall being located on the side opposite to the side on which the clutch cover6is disposed. As illustrated inFIG. 5, the annular clip groove17is not formed in the engagement grooves18of the rotary shaft2, and thus, in the case where the annular inner edge portion12does not have the recesses20, the load is applied more intensively to portions in the vicinity of the engagement grooves18. Arrows inFIG. 5indicate a vector that represents the magnitude and direction of the load.

In addition, the uneven application of the load varies depending on the positional relationship between the end gap22of the circlip16and one of the engagement grooves18, and when the end gap22is close to one of the engagement grooves18as illustrated inFIG. 6, the load is more concentrated at the portion in the vicinity of the engagement groove18.

In contrast, according to the present embodiment, as illustrated inFIG. 7, the recesses20, which prevent the circlip16from coming into contact with the clutch cover6, are formed in the regions in the circumferential direction in which the engagement protruding portions19of the clutch cover6, which engage in the corresponding engagement grooves18, are present. Therefore, in these regions, the load from the clutch cover6will not directly applied to a side wall of the annular clip groove17. As a result, the likelihood of a stress being concentrated at portions of the annular clip groove17in the vicinity of the engagement grooves18is reduced, so that a fatigue failure is prevented from occurring in the annular clip groove17.

As described above, according to the present embodiment, since the relative rotation between the rotary shaft2and the clutch cover6is hindered by the engagement of the engagement protruding portions19of the clutch cover6and the engagement grooves18of the rotary shaft2, wear of the O-ring8bmay be prevented, and a function of the O-ring8bmay be maintained. In addition, since the circlip16does not rotate relative to the annular clip groove17, a fatigue failure may be prevented from occurring in the annular clip groove17.

Since the recesses20, which prevent the circlip16from coming into contact with the clutch cover6, are formed, the likelihood of a stress being concentrated at the portions of the annular clip groove17in the vicinity of the engagement grooves18may be reduced, and a fatigue failure may be prevented from occurring in the annular clip groove17.

Since a fatigue failure may be prevented from occurring in the annular clip groove17, the diameter of the bottom of the annular clip groove17may be reduced, and also the depth of the annular clip groove17may be increased. As a result, the engagement allowance of the circlip16may be increased. Therefore, the diameter and width of the circlip16may be reduced, and a reduction in the size of the clutch structure1may be achieved.

A clutch structure according to a first aspect of the present disclosure (which is, for example, a clutch structure1according to an embodiment, and the same applies to the following) includes a rotary shaft (which is, for example, a rotary shaft2according to the embodiment, and the same applies to the following) that is rotatably supported, a cylindrical member (which is, for example, an outer drum3according to an embodiment, and the same applies to the following) that is rotatably disposed on the outside of the rotary shaft in such a manner that the cylindrical member and the rotary shaft are on the same axis, and a clutch portion (which is, for example, a clutch portion4according to the embodiment, and the same applies to the following) that switches between a disconnected state in which the cylindrical member is allowed to rotate relative to the rotary shaft and a connected state in which rotation of the cylindrical member relative to the rotary shaft is hindered. The clutch portion includes a clutch piston (which is, for example, a clutch piston5according to the embodiment, and the same applies to the following) that is disposed at an outer periphery of the rotary shaft in such a manner as to be capable of sliding in an axial direction, a clutch cover (which is, for example, a clutch cover6according to the embodiment, and the same applies to the following) that is fixed to the outer periphery of the rotary shaft in such a manner as to form, between the clutch cover and the clutch piston, an oil chamber (which is, for example, an oil chamber7according to the embodiment, and the same applies to the following) to which a hydraulic fluid used for causing the clutch piston to operate is supplied, and a seal member (which is, for example, an O-ring8baccording to the embodiment, and the same applies to the following) that hermetically seals a space between the rotary shaft and the clutch cover. The clutch cover includes an annular inner edge portion (which is, for example, an annular inner edge portion12according to the embodiment, and the same applies to the following) that is fitted onto the outer periphery of the rotary shaft in a fitting direction, which is parallel to the axial direction, and a cover-side contact surface (which is, for example, a cover-side contact surface13according to the embodiment, and the same applies to the following) that has a ring-like shape and that rises outward in a radial direction from an end edge of the annular inner edge portion, the end edge facing the fitting direction. The rotary shaft has an outer peripheral fitting surface (which is, for example, an outer peripheral fitting surface14according to the embodiment, and the same applies to the following) onto which the annular inner edge portion of the clutch cover is fitted on an outside of the outer peripheral fitting surface, a shaft-side contact surface (which is, for example, a shaft-side contact surface15according to the embodiment, and the same applies to the following) that rises outward in the radial direction from an end edge of the outer peripheral fitting surface, the end edge facing the fitting direction, and that comes into contact with the cover-side contact surface, an annular clip groove (which is, for example, an annular clip groove17according to the embodiment, and the same applies to the following) in which a circlip (which is, for example, a circlip16according to the embodiment, and the same applies to the following) is accommodated, the circlip fixing in place the annular inner edge portion of the clutch cover, which is fitted to the outer peripheral fitting surface and which is in contact with the shaft-side contact surface, by pressing the annular inner edge portion from a side opposite to a side on which the shaft-side contact surface is present, and an engagement groove (which is, for example, an engagement groove18according to the embodiment, and the same applies to the following) that is formed in the outer peripheral fitting surface along the axial direction. The clutch cover further includes an engagement protruding portion (which is, for example, an engagement protruding portion19according to the embodiment, and the same applies to the following) that protrudes inwardly in the radial direction from an inner peripheral surface of the annular inner edge portion and that engages in the engagement groove in such a manner as to hinder the clutch cover from rotating relative to the rotary shaft.

According to the first aspect of the present disclosure, in the related art, an engagement protruding portion of a clutch cover and an engagement groove of a rotary shaft in which the engagement protruding portion engages are not provided, and thus, the clutch cover may sometimes rotate relative to the rotary shaft. In this case, there is a possibility that a seal member disposed between the clutch cover and the rotary shaft will wear and that a function of the seal member will deteriorate. In addition, there is a possibility that a stress will be concentrated at a portion of an annular clip groove due to uneven distribution of the pressure between contact surfaces of a circlip and the annular clip groove, in which the circlip is accommodated, generated as a result of an end gap of the circlip forming a step or being twisted, so that a fatigue failure will occur in the annular clip groove.

Regarding this, according to the first aspect of the present disclosure, since the engagement protruding portion of the clutch cover engages in the engagement groove of the rotary shaft in such a manner as to hinder relative rotation between the rotary shaft and the clutch cover, the above-mentioned wear of the seal member may be prevented, and a fatigue failure may be prevented from occurring in the annular clip groove.

A clutch structure according to a second aspect of the present disclosure, in the first aspect of the present disclosure, a recess (which is, for example, a recess20according to the embodiment, and the same applies to the following) that prevents the circlip from coming into contact with the clutch cover is formed in a region of the annular inner edge portion of the clutch cover in which the engagement protruding portion is present, the region extending in a circumferential direction.

According to the second aspect of the present disclosure, a load from the piston cover in the axial direction is applied to an inner wall of the annular clip groove of the rotary shaft, the inner wall being located on the side opposite to the side on which the clutch cover is disposed. The load is applied more intensively to a portion in the vicinity of the engagement groove because the inner wall is not formed in the engagement groove of the rotary shaft. In addition, this uneven application of the load varies depending on the positional relationship between an end gap of the circlip and the engagement groove, and when the end gap is close to the engagement groove, the load is more concentrated at the portion in the vicinity of the engagement groove.

Regarding this, according to the second aspect of the present disclosure, since the recess that prevents the above-mentioned circlip from coming into contact with the clutch cover is formed in the region extending in the circumferential direction, in which the engagement protruding portion of the clutch cover that engages in the engagement groove is present, the load from the clutch cover will not directly applied to a side wall of the annular clip groove in the region.

As a result, stress concentration at the annular clip groove in the vicinity of the engagement groove may be reduced, and a fatigue failure may be prevented from occurring in the annular clip groove. Consequently, the diameter of the bottom of the annular clip groove may be reduced, and also the depth of the annular clip groove may be increased. As a result, the engagement allowance of the circlip may be increased. Therefore, the diameter and width of the circlip may be reduced, and a reduction in the size of the clutch structure may be achieved.