Patent Description:
Conventionally, vehicles such as four-wheeled vehicles and two-wheeled vehicles are equipped with a wet multiple-plate clutch device in order to transmit or cut off a rotational driving force of the prime mover such as an engine to the driven body such as a wheel. Generally, in the wet multiple-plate clutch device, the rotational driving force is transmitted or cut off by pressing two plates arranged to face each other in the lubricating oil against each other.

In this case, one of the two plates includes the wet friction plate in which a friction material is provided in a circumferential direction on a surface of a flat plate annular core metal. For example, in a friction plate (hereinafter referred to as a "wet friction plate") in a laser processing method of a friction plate, and in the friction plate in a laser processing apparatus disclosed in PATENT LITERATURE <NUM> below, a recess (hereinafter referred to as a "fine groove") formed of minute irregularities or a groove is formed on a surface of the friction material by a laser beam. Thus, the wet friction plate can control retention property and discharge property of the lubricating oil on the friction material. PATENT LITERATURE <NUM> discloses a segment type friction material as a wet friction material which is structured by bonding a plurality of segment pieces lined with spaces and a pulling-in portion using an adhesive (thermosetting resin) on a core metal of steel plate of a flat ring shape with a plurality of oil grooves passing through in the radial direction on both sides are provided and by bonding the same similarly on the back surface of the core metal. PATENT LITERATURE <NUM> discloses a segment friction material as a wet friction material, on which drag torque reducing grooves are provided only on top surfaces of part of segment pieces among thirty pieces of segment pieces. A series of drag torque reducing grooves extend over five segment pieces along a direction almost at right angles to a straight line connecting a center point thereof and a center O of a circumference. The series of drag torque reducing grooves are provided at three places on the circumference. Thereby, discharge of ATF is promoted without reducing a lining area and an oil film is formed on the top surface of the segment piece. PATENT LITERATURE <NUM> discloses a method for producing a pattern of depressions in the friction surface of a friction component for a frictionally operating device, preferably a multiplate clutch or multiplate brake. After the preparation of the friction component, the pattern of depressions is produced by nontraditional material removal, removal of material preferably being accomplished in a contactless manner, particularly preferably with the aid of a laser beam.

However, in the laser processing method of the wet friction plate and the laser processing apparatus described in PATENT LITERATURE <NUM>, since the fine groove is formed by irradiating a friction material portion on the wet friction plate with the laser beam, there is a problem that efficiency of work of forming the fine groove is low. In particular, in the wet friction plate in which the friction material is intermittently provided in the circumferential direction on the core metal of the wet friction plate, there is a problem that the work of positioning the core metal on a processing head on a processing stage and the control of repeating irradiation and interruption of the laser beam for each friction material on the core metal is complicated.

The present invention has been made to address the above problems. An object of the present invention is to provide a method for manufacturing a wet friction plate, whereby the efficiency of the work of forming the fine groove on the friction material can be improved, the wet friction plate, and a wet multiple-plate clutch device having the wet friction plate.

In order to achieve the object described above, a feature of the present invention is a method for manufacturing a wet friction plate in which a friction material is provided in a circumferential direction on a surface of a core metal formed in a flat plate annular shape, the method including: a friction material fixing step of attaching a plurality of the friction materials to the surface of the core metal; and a fine groove forming step of forming a recessed fine groove on a surface of the friction material by irradiating the core metal with laser beam while being displaced with respect to the core metal. In the fine groove forming step, the fine groove is formed on the surface of the friction material by continuously emitting the laser beam without interruption between an exposed portion of a plate surface of the core metal and the friction material.

According to the feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, the fine groove is formed on the surface of the friction material by continuously emitting the laser beam without interruption between the exposed portion on the plate surface of the core metal and the friction material. Therefore, positioning accuracy of the core metal with respect to a laser head that emits the laser beam can be relaxed. Further, irradiation control of the laser beam can also be simplified. Therefore, the efficiency of the work of forming the fine groove on the friction material can be improved. In this case, the fine groove is formed in a shape that a portion dug in a recessed cross-sectional shape having a groove width of <NUM> or less and <NUM> or more, a depth of <NUM> or less and <NUM> or more, extends intermittently or continuously long.

Further, another feature of the present invention is the method for manufacturing the wet friction plate, in which in the friction material fixing step, the friction materials are arranged on the surface of the core metal with a gap in the circumferential direction and attached onto the core metal, and in the fine groove forming step, the fine groove is formed on the surface of the friction material by continuously emitting the laser beam without interruption between the gap on the core metal and the friction material.

According to the other feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, the fine groove is formed on the surface of the friction material by continuously emitting the laser beam without interruption between the gap between the friction materials and the friction material. Therefore, the positioning accuracy of the core metal with respect to the laser head that emits the laser beam can be relaxed. Further, the irradiation control of the laser beam can be simplified. Therefore, the efficiency of the work of forming the fine groove on the friction material can be improved.

Another feature of the present invention is that in the method for manufacturing the wet friction plate, in the fine groove forming step, when the laser beam is irradiated onto the core metal, the laser beam is started to be emitted outside the core metal.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, in the fine groove forming step, when the laser beam is irradiated onto the core metal, the laser beam is started to be emitted outside the core metal. Therefore, since the exposed portion or the friction material on the core metal is prevented from being irradiated with unstable laser beam at the time of emission and immediately after the emission, the fine groove can be stably formed.

Another feature of the present invention is that in the method for manufacturing the wet friction plate, in the fine groove forming step, when the laser beam is irradiated onto the friction material, the laser beam is started to be emitted at the exposed portion of the core metal.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, in the fine groove forming step, when the laser beam is irradiated onto the core metal, the laser beam is started to be emitted at the exposed portion of the core metal. Therefore, since the friction material on the core metal is prevented from being irradiated with the unstable laser beam at the time of emission and immediately after the emission, the fine groove can be stably formed.

Another feature of the present invention is that the method for manufacturing the wet friction plate includes a resin layer forming step of forming a resin layer by applying a resin material to at least a part of the exposed portion of the core metal prior to the fine groove forming step.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, the resin layer forming step of forming the resin layer made of a layer of the resin material on at least a part of the exposed portion of the core metal is performed prior to the fine groove forming step. Therefore, it is possible to prevent or reduce formation of the fine groove in the exposed portion of the core metal.

Another feature of the present invention is that in the method for manufacturing the wet friction plate, the resin layer forming step is performed prior to the friction material fixing step, and in this step, the resin layer is formed on an entire surface of the core metal, and in the friction material fixing step, the friction material is attached onto the resin layer.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, the resin layer forming step is performed prior to the friction material fixing step, and in this step, the resin layer is formed on the entire surface of the core metal. Therefore, the resin layer can be easily and quickly formed on the surface of the core metal.

Another feature of the present invention is that in the method for manufacturing the wet friction plate, in the resin layer forming step, the resin layer is formed to be transparent or translucent to the extent that the surface of the core metal can be visually recognized.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, the resin layer is formed to be transparent or translucent to the extent that the surface of the core metal can be visually recognized. Therefore, since the exposed portion on the surface of the core metal can be visually recognized, appearance inspection of the wet friction plate is not hindered. Further, it is possible to confirm how much of the fine groove is formed in the exposed portion on the surface of the core metal by irradiating the laser beam.

Another feature of the present invention is that the method for manufacturing the wet friction plate further includes a resin layer removing step of removing the resin layer exposed on the core metal.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, the resin layer removing step of removing the resin layer exposed on the core metal is further performed. Therefore, it is possible to prevent an increase in weight due to formation of the resin layer and deterioration in appearance due to the resin layer remaining.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, in the fine groove forming step, the fine groove is formed to extend spirally in the circumferential direction in the core metal.

According to another feature of the present invention configured as described above, in the method for manufacturing the wet friction plate, the fine groove is formed to extend spirally in the circumferential direction in the core metal. Therefore, the fine groove can be continuously formed by continuously irradiating the laser beam without interruption. Therefore, a homogeneous fine groove can be formed in a short time.

The present invention can be implemented not only as an invention of the method for manufacturing the wet friction plate, but also as an invention of the wet friction plate, and the wet multiple-plate clutch including the wet friction plate.

Specifically, the wet friction plate is a wet friction plate in which a friction material is provided in a circumferential direction on a surface of a core metal formed in a flat plate annular shape, and a recessed fine groove may be formed in both an exposed portion of a plate surface of the core metal and the friction material in a state of being continuously connected in a plan view between the exposed portion and the friction material. According to the wet friction plate configured as described above, the same operational effects as the method for manufacturing the wet friction plate can be expected.

In this case, in the wet friction plate, preferably, regarding the frictional material, a plurality of the friction materials is provided in the circumferential direction on the surface of the core metal with a gap interposed therebetween, and the fine groove is formed in a concave shape continuously connected in a plan view between the gap and the friction material on the core metal. According to the wet friction plate configured as described above, the same operational effects as the method for manufacturing the wet friction plate can be expected.

In these cases, in the wet friction plate, preferably, a resin layer made of a resin material is further formed on at least a part of the exposed portion of the core metal. According to the wet friction plate configured as described above, the same operational effects as the method for manufacturing the wet friction plate can be expected.

The wet friction plate is a wet friction plate in which a friction material is provided in a circumferential direction on a surface of a core metal formed in a flat plate annular shape, a recessed fine groove is formed in the friction material on the core metal, and a resin layer made of a resin material may be formed on at least a part of an exposed portion of a plate surface of the core metal. According to the wet friction plate configured as described above, the same operational effects as the method for manufacturing the wet friction plate can be expected.

In these cases, in the wet friction plate, preferably, the resin layer is formed on the entire surface of the core metal, and the friction material is attached onto the resin layer. According to the wet friction plate configured as described above, the same operational effects as the method for manufacturing the wet friction plate can be expected.

In these cases, in the wet friction plate, preferably, the resin layer is formed to be transparent or translucent to the extent that the surface of the core metal can be visually recognized. According to the wet friction plate configured as described above, the same operational effects as the method for manufacturing the wet friction plate can be expected.

In these cases, in the wet friction plate, preferably, the fine groove is formed to extend spirally in the circumferential direction in the core metal. According to the wet friction plate configured as described above, the same operational effects as the method for manufacturing the wet friction plate can be expected.

Specifically, in a wet multiple-plate clutch device in which an opposing plate is disposed to face a drive side plate that is rotationally driven by a prime mover through a gap and a lubricating oil, and a rotational driving force is transmitted or cut off between the two plates when the two plates are in close contact with each other or separated from each other, at least one of the drive side plate and the opposing plate may be the wet friction plate according to any one of claims <NUM> to <NUM>. According to the wet multiple-plate clutch device configured as described above, the same operational effects as the method for manufacturing the wet friction plate, and the wet friction plate can be expected.

Hereinafter, an embodiment of a wet friction plate, a wet multiple-plate clutch device having the wet friction plate, and a method for manufacturing the wet friction plate according to the present invention will be described with reference to the drawings. <FIG> is a cross-sectional view illustrating an outline of an overall configuration of a wet multiple-plate clutch device <NUM> having a wet friction plate <NUM> according to the present invention. <FIG> is a plan view illustrating an outline of an external configuration of the wet friction plate <NUM> according to the present invention included in the wet multiple-plate clutch device <NUM> illustrated in <FIG>. <FIG> is a partially enlarged side view of the wet friction plate <NUM> schematically illustrating a configuration within a broken line circle <NUM> shown in <FIG> as viewed from the inside of a core metal <NUM>. It should be noted that each of the drawings referred to in the present specification is schematically illustrated for facilitating understanding of the present invention, and for example, some components are exaggerated. Therefore, dimensions and ratios between the components may be different. The wet multiple-plate clutch device <NUM> is a mechanical device for transmitting or cutting off a driving force of an engine (not shown) which is a prime mover in a two-wheeled vehicle (motorcycle) to a wheel (not shown) which is a driven body. The wet multiple-plate clutch device <NUM> is disposed between the engine and a transmission (not shown).

The wet multiple-plate clutch device <NUM> includes a housing <NUM> made of an aluminum alloy. The housing <NUM> is formed in a bottomed cylindrical shape, and is a member that constitutes a part of a housing of the wet multiple-plate clutch device <NUM>. An input gear <NUM> is fixed to a left side surface of the housing <NUM> illustrated in the drawing by a rivet 102b via a torque damper 102a. The input gear <NUM> is rotationally driven by meshing with a drive gear (not shown) that is rotationally driven by driving the engine. On an inner peripheral surface of the housing <NUM>, a plurality of (eight in the present embodiment) clutch plates <NUM> is respectively held by spline fitting so that they can be displaced in an axial direction of the housing <NUM> and can rotate integrally with the housing <NUM>.

The clutch plate <NUM> is a flat plate annular component that is pressed against the wet friction plate <NUM> described below. The clutch plate <NUM> is formed by punching a thin plate material made of an SPCC (cold rolled steel plate) material in an annular shape. Oil grooves (not shown) having a depth of several µm to several tens µm to hold a lubricating oil described below are respectively formed on both side surfaces (front and back surfaces) of the clutch plates <NUM>. Further, each of the both side surfaces (front and back surfaces) of the clutch plate <NUM> in which the oil groove is formed is subjected to surface hardening treatment for the purpose of improving wear resistance. Since the surface hardening treatment is not directly related to the present invention, a description thereof will be omitted.

Inside the housing <NUM>, a friction plate holder <NUM> formed in a substantially cylindrical shape is disposed concentrically with the housing <NUM>. A large number of spline grooves are formed in the axial direction of the friction plate holder <NUM> on an inner peripheral surface of the friction plate holder <NUM>. A shaft <NUM> is spline-fitted into the spline grooves. The shaft <NUM> is a shaft body formed in a hollow shape. One end (A right end in the drawing) of the shaft <NUM> rotatably supports the input gear <NUM> and the housing <NUM> via a needle bearing 105a, and fixedly supports the friction plate holder <NUM> to fit the spline via a nut 105b. That is, the friction plate holder <NUM> rotates integrally with the shaft <NUM>. On the other hand, the other end (left end in the drawing) of the shaft <NUM> is connected to the transmission (not shown) in the two-wheeled vehicle.

In a hollow portion of the shaft <NUM>, a shaft-like push rod <NUM> is disposed to penetrate the one end (right end in the drawing) of the shaft <NUM> in a state of protruding therefrom. An end (A left end of the drawing) opposite to an end of the push rod <NUM> protruding from the one end (right end of the drawing) of the shaft <NUM> is connected to a clutch operating lever (not shown) of the two-wheeled vehicle. The push rod <NUM> slides in the hollow portion of the shaft <NUM> in the axial direction of the shaft <NUM> by operating the clutch operating lever.

On an outer peripheral surface of the friction plate holder <NUM>, a plurality of (seven in this embodiment) wet friction plates <NUM> is respectively held by spline fitting so that they can be displaced in the axial direction of the friction plate holder <NUM> and can rotate integrally with the friction plate holder <NUM> with the clutch plates <NUM> interposed therebetween.

On the other hand, a predetermined amount of the lubricating oil (not shown) is filled in the friction plate holder <NUM>, and three tubular support columns 104a are formed therein (only one is shown in the drawing). The lubricating oil is supplied between the wet friction plate <NUM> and the clutch plate <NUM> to absorb frictional heat generated between the wet friction plate <NUM> and the clutch plate <NUM> and prevent a friction material <NUM> from being worn.

The three tubular support columns 104a are formed to project outward (rightward in the drawing) in the axial direction of the friction plate holder <NUM>. A pressing cover <NUM>, which is disposed concentrically with the friction plate holder <NUM>, is assembled via bolts 108a, receiving plates 108b, and coil springs 108c. The pressing cover <NUM> is formed in a substantially disk shape having an outer diameter substantially the same as the outer diameter of the wet friction plate <NUM>. The pressing cover <NUM> is pressed toward the friction plate holder <NUM> by the coil springs 108c. A release bearing 107a is provided at a position facing the right end in the drawing of the push rod <NUM>, at an inner center of the pressing cover <NUM>.

As illustrated in <FIG> in detail, the wet friction plate <NUM> is configured to include oil grooves <NUM> and friction materials <NUM> on a flat plate annular core metal <NUM>. The core metal <NUM> is a member that serves as a base of the wet friction plate <NUM>. The core metal <NUM> is formed by punching the thin plate material made of the SPCC (cold rolled steel plate) material in a substantially annular shape. In this case, an internal tooth-shaped spline <NUM> to be spline-fitted with the friction plate holder <NUM> is formed on an inner peripheral portion of the core metal <NUM>.

A side surface of the wet friction plate <NUM> facing the clutch plate <NUM>, that is, a ring-shaped plate surface of the core metal <NUM> facing the clutch plate <NUM>, is provided with a plurality of (<NUM> pieces in this embodiment) small piece-shaped friction members <NUM> via a resin layer <NUM>, in a circumferential direction of the core metal <NUM> via the oil grooves <NUM> formed of gaps.

The resin layer <NUM> is a portion for preventing or reducing formation of a fine groove <NUM> in the plate surface of the core metal <NUM> by the laser beam used when forming a fine groove <NUM> in the friction material <NUM>, and for fixing the friction material <NUM> on the core metal <NUM>. More specifically, the resin layers <NUM> include an adhesive made of a thermosetting resin, and are respectively formed on entire both surfaces of the core metal <NUM> with a substantially uniform thickness. In this case, the resin layers <NUM> are also formed respectively on both side surfaces of the spline <NUM>.

The resin layer <NUM> is formed to have a thickness that can fix the friction material <NUM> on the core metal <NUM> and can prevent or reduce the formation of the fine groove <NUM> in the plate surface of the core metal <NUM>. Specifically, the resin layer <NUM> is preferably <NUM> or more and <NUM> or less, and more preferably <NUM> or more and <NUM> or less. In this embodiment, the resin layer <NUM> is formed to have a thickness of <NUM> from the surface of the core metal <NUM>. In this case, the resin layer <NUM> is formed to be transparent or translucent to the extent that the surface of the core metal <NUM> can be visually recognized by a human.

As the thermosetting resin constituting the resin layer <NUM>, a phenol resin, a modified phenol resin, an epoxy resin, a urea resin, an unsaturated polyester resin, a polyurethane resin, or a polyimide resin can be used. In this embodiment, the resin layer <NUM> is made of a phenol resin. Further, as the resin constituting the resin layer <NUM>, various elastomers (for example, nitrile rubber-based or chloroprene rubber-based) can be used in addition to the thermosetting resin. In the cases, the resin constituting the resin layer <NUM> does not necessarily have to have adhesiveness. That is, the resin layer <NUM> may be made of at least a resin capable of preventing or reducing the formation of the fine groove <NUM> in the plate surface of the core metal <NUM>. As a material for fixing the friction material <NUM> on the core metal <NUM>, an adhesive made of a substance different from the resin constituting the resin layer <NUM> may be used.

The fine groove <NUM> is a portion on the core metal <NUM> that is concavely removed when the fine groove <NUM> is formed on the surface of the friction material <NUM>. The fine groove <NUM> is formed in a groove shape extending arcuately so as to be continuously connected to the fine groove <NUM> in a plan view of the wet friction plate <NUM>, on a portion other than a portion covered with the friction material <NUM> on the surface of the core metal <NUM> provided with the friction material <NUM>, that is, on an exposed portion <NUM> on the plate surface of the core metal <NUM>. In this embodiment, the fine groove <NUM> is formed so that a groove width thereof is about <NUM>, a depth of the deepest portion is about <NUM>, and a cross-sectional shape thereof is an arc shape. The fine grooves <NUM> are formed to form three annular rings in a plan view of the wet friction plate <NUM>, together with the fine grooves <NUM>. In this case, the three annular rings are configured to be concentric rings centered on a core of the core metal <NUM>.

The oil groove <NUM> is a flow path for guiding the lubricating oil between an inner peripheral edge and an outer peripheral edge of the core metal <NUM> of the wet friction plate <NUM>. Further, the oil groove <NUM> is also an oil holding portion for allowing the lubricating oil to be present between the wet friction plate <NUM> and the clutch plate <NUM>. The oil groove <NUM> is formed as a gap between the friction materials <NUM> adjacent to each other. In this embodiment, the oil grooves <NUM> include fan-shaped portions between four small pieces of friction materials <NUM> and four small pieces of friction materials <NUM>, and portions formed to extend linearly between the four friction materials <NUM> arranged between two fan-shaped oil grooves <NUM>.

The friction material <NUM> increases a frictional force against the clutch plate <NUM>. The friction material <NUM> is made of a small piece of paper material attached in the circumferential direction of the core metal <NUM>. In the present embodiment, the friction materials <NUM> are configured such that eight groups of small pieces are arranged in the circumferential direction of the core metal <NUM> via eight fan-shaped oil grooves <NUM>, and in the group of small pieces, four quadrangular pieces extending in the circumferential direction of the core metal <NUM> are arranged in the circumferential direction of the core metal <NUM> via three linear oil grooves <NUM>. The fine groove <NUM> is formed on the surface of the friction material <NUM>. Note that the friction material <NUM> may be made of a material capable of increasing the frictional force between the wet friction plate <NUM> and the clutch plate <NUM>. The friction material <NUM> can be made of a material other than the paper material, for example, a cork material, a rubber material, a glass material, or the like.

The fine groove <NUM> is a portion for defining retention property and discharge property of the lubricating oil on the friction material <NUM>. The fine groove <NUM> is formed in a concave shape on the surface of the friction material <NUM>. In this embodiment, the fine groove <NUM> is formed in a groove shape extending arcuately in the circumferential direction of the core metal <NUM>. In this case, in the present embodiment, the fine groove <NUM> is formed so that the groove width is about <NUM>, the depth of the deepest portion is about <NUM>, and the cross-sectional shape is the arc shape. The fine grooves <NUM> are formed to form the three annular rings in a plan view of the wet friction plate <NUM>, together with the fine grooves <NUM>. In this case, the three annular rings are configured to be concentric rings centered on the core of the core metal <NUM>. As a matter of course, the cross-sectional shape of the fine grooves <NUM> and <NUM> may be a shape other than the arc shape, for example, a rectangular shape or a triangular shape.

Next, a method of manufacturing the wet friction plate <NUM> configured as described above will be described with reference to <FIG>. First, an operator prepares the core metal <NUM> and the friction material <NUM> as a first step. Specifically, the core metal <NUM> is formed into the annular shape having the spline <NUM> by separate press working by the operator. Further, the friction material <NUM> is formed in a strip shape by separate papermaking process. Since the press working and the papermaking process are conventionally known methods, descriptions thereof will be omitted.

Subsequently, as a second step, the operator forms the resin layer <NUM> on each of two plate surfaces of the core metal <NUM>. Specifically, as illustrated in <FIG>, the operator can form the resin layer <NUM> obtained by curing the resin layer raw material, by applying the resin layer raw material made of a liquid thermosetting resin, which is a raw material of the resin layer <NUM>, to each of entire two plate surfaces of the core metal <NUM> using a tool such as a brush or a roller, and then by heating and drying. In this case, the operator can form the resin layer <NUM> by applying the raw material to the surface of the core metal <NUM> once or a plurality of times. Note that in <FIG>, the resin layer <NUM> is shown by hatching. This second step corresponds to a resin layer forming step according to the present invention.

Subsequently, as a third step, the operator attaches the friction material <NUM> to the two plate surfaces of the core metal <NUM>. Specifically, the operator applies a liquid adhesive to the entire surface of the resin layer <NUM> on the core metal <NUM> using the tool such as the brush or the roller. Thereafter, the operator places the friction material <NUM> thereon before the adhesive dries, and then dries the resin raw material. In this embodiment, as the adhesive, the resin layer raw material made of the liquid thermosetting resin, which is the same as the raw material of the resin layer <NUM>, is used. That is, the resin raw material constituting the resin layer <NUM> is made of the adhesive. Further, in this case, the operator may form the friction material <NUM> into small pieces by cutting the friction material <NUM> extending in a strip shape while being placed on the core metal <NUM>. Alternatively, the operator may place the friction material <NUM>, which is formed in small pieces in advance, on the core metal <NUM>. Thus, the friction material <NUM> is fixed on the resin layer <NUM> on the core metal <NUM>.

In the third step, the operator may also apply the adhesive only at a position where the friction material <NUM> is disposed, or only in an annular shape in the circumferential direction in which the friction material <NUM> is disposed. Further, when the resin layer <NUM> is made of the adhesive, the operator may arrange the friction material <NUM> immediately after applying the resin layer raw material in the second step onto the core metal <NUM>, and may cure the resin layer raw material. That is, the second step and the third step can be performed at the same time. The third step corresponds to a friction material fixing step according to the present invention.

Subsequently, as a fourth step, the operator forms the fine groove <NUM> in the friction materials <NUM> attached to the both surfaces of the core metal <NUM>. In this case, the operator uses a laser processing apparatus <NUM> to form the fine groove <NUM>. Here, the laser processing apparatus <NUM> is a mechanical apparatus for forming the fine groove <NUM> by irradiating the friction material <NUM> on the core metal <NUM> with a laser beam L. The laser processing apparatus <NUM> is a known mechanical apparatus, and detailed description thereof will be omitted. However, a configuration thereof will be briefly described with reference to <FIG>.

The laser processing apparatus <NUM> is mainly configured to include a laser oscillator (not shown), a laser adjusting optical system (not shown), a laser head <NUM>, a work table <NUM>, and a control device (not shown). The laser oscillator is a mechanical device for emitting the laser beam L for forming the fine groove <NUM> in the friction material <NUM>. In this embodiment, the laser oscillator is configured as an oscillator that emits a pulsed laser beam having a frequency of <NUM>, an output of <NUM> W, and a short pulse width such as nanoseconds, picoseconds, femtoseconds, or the like. The laser adjusting optical system includes optical components including various optical elements such as a lens and a mirror, an optical fiber and the like, and the optical components guide the laser beam L emitted by the laser oscillator to the laser head <NUM> while making various adjustments such as correction of its beam diameter, beam shape and aberration.

The laser head <NUM> is an optical device that emits the laser beam L guided from the laser adjusting optical system to the work table <NUM> and collects it on the wet friction plate. The laser head <NUM> is configured to be displaceable in three axial directions of the X-axis direction, the Y-axis direction, and the Z-axis direction, which are orthogonal to each other with respect to the work table <NUM>. The work table <NUM> is a device that detachably holds the core metal <NUM>, to which the friction material <NUM> is attached, at a position facing the laser head <NUM>. Note that a positional relationship between the laser head <NUM> and the work table <NUM> is relative. Therefore, as a matter of course, a configuration in which the work table <NUM> is displaced instead of the laser head <NUM> may be adopted.

The control device includes a microcomputer including a CPU, a ROM, a RAM, and the like, and comprehensively controls overall operation of the laser processing device <NUM>. Specifically, the control device controls operations of the laser oscillator, the laser adjusting optical system, and the laser head <NUM> according to an instruction of the operator, and irradiates the friction material <NUM> with the laser beam L while displacing the laser beam, to form the fine groove <NUM>.

In the fourth step, the operator holds the core metal <NUM> to which the friction material <NUM> is attached on the work table <NUM>. Thereafter, the operator instructs the control device of the laser processing apparatus <NUM> to machine the fine groove <NUM>. In response to the instruction, the control device emits the laser beam L from the laser head <NUM> while displacing the laser beam L on the friction material <NUM> by displacing the laser head <NUM> in the X-axis direction and the Y-axis direction, to form the fine groove <NUM>.

Specifically, as illustrated in <FIG>, the control device starts irradiating the exposed portion <NUM> of the core metal <NUM> with the laser beam L. The control device displaces the laser head <NUM> in an annular shape starting from a position P1 while maintaining a state in which the laser light L is continuously emitted, and stops emitting the laser light L when the laser head <NUM> returns to the position P1. Thus, in the core metal <NUM>, annular fine grooves <NUM> and <NUM>, which are continuously connected in a plan view, are respectively formed on the surfaces of the exposed portion <NUM> and the friction material <NUM>. Note that in <FIG>, a circular orbit on which the laser beam L is displaced is shown by a broken line.

In this case, since the resin layer <NUM> is formed on the surface of the core metal <NUM>, as the fine groove <NUM>, a recessed groove having a narrower groove width and/or a shallower depth is formed as compared with a case where the resin layer <NUM> is not formed. According to experiments by the present inventors, it was confirmed that by forming the thickness of the resin layer <NUM> in a thickness of <NUM>, the depth of the groove can be reduced by <NUM>% to <NUM>% to be shallower. Then, the control device performs an annular displacement at other two positions P2 and P3 in a radial direction of the core metal <NUM> together with emission of the laser beam L in the same manner as described above, so that the annular fine grooves <NUM> and <NUM> are respectively formed. The fourth step corresponds to a fine groove forming step according to the present invention.

Subsequently, the operator takes out the core metal <NUM> from the work table <NUM>. Thus, a work of forming the fine groove <NUM> on one surface side of the core metal <NUM> is completed. Therefore, the operator turns over the core metal <NUM> on which the fine grooves <NUM> and <NUM> are formed, and performs the same operation on the other surface, so that the three annular fine grooves <NUM> and <NUM> are formed on the other surface. Thus, the operator can form the fine grooves <NUM> respectively on the surfaces of the friction materials <NUM> on the both surfaces of the core metal <NUM>. Thereafter, the operator performs a friction characteristic adjusting step and an inspection step to complete the wet friction plate <NUM>. Since they are not directly related to the present invention, their description will be omitted.

Next, an operation of the wet friction plate <NUM> configured as described above will be described. As described above, the wet friction plate <NUM> is assembled and used in the wet multiple-plate clutch device <NUM>. Then, as described above, the wet multiple-plate clutch device <NUM> is disposed between the engine and the transmission in the vehicle, and transmits and cuts off the driving force of the engine to the transmission in response to the operation of the clutch operating lever by a driver of the vehicle.

That is, when the driver (not shown) of the vehicle operates the clutch operating lever (not shown) to retract the push rod <NUM> (displace it to the left side of the drawing), a tip of the push rod <NUM> does not press the release bearing 107a, and the pressing cover <NUM> presses the clutch plate <NUM> by an elastic force of the coil spring 108c. Thus, the clutch plate <NUM> and the wet friction plate <NUM> are pressed against and frictionally connected to each other while being displaced toward a receiver 104b formed in a flange shape on the outer peripheral surface of the friction plate holder <NUM>. As a result, the driving force of the engine transmitted to the input gear <NUM> is transmitted to the transmission via the clutch plate <NUM>, the wet friction plate <NUM>, the friction plate holder <NUM> and the shaft <NUM>.

On the other hand, when the driver of the vehicle operates the clutch operating lever (not shown) to move the push rod <NUM> forward (displace it to the right side of the drawing), the tip of the push rod <NUM> presses the release bearing 107a, the pressing cover <NUM> is displaced to the right side of the drawing while resisting the elastic force of the coil spring 108c, and the pressing cover <NUM> and the clutch plate <NUM> are separated from each other. Thus, the clutch plate <NUM> and the wet friction plate <NUM> are displaced toward the pressing cover <NUM>, a state in which the clutch plate <NUM> and the wet friction plate <NUM> are pressed against and connected to each other is released, and they are separated from each other. As a result, the driving force is not transmitted from the clutch plate <NUM> to the wet friction plate <NUM>, and transmission of the driving force of the engine transmitted to the input gear <NUM> to the transmission is cut off.

In a state where the clutch plate <NUM> and the wet friction plate <NUM> are in frictional contact with each other, the fine groove <NUM> formed on the surface of the friction material <NUM> improves the discharge property of the lubricating oil present on the friction material <NUM> to the outside of the friction material <NUM>. Further, in a state where the clutch plate <NUM> and the wet friction plate <NUM> are separated from each other, the fine groove <NUM> formed on the surface of the friction material <NUM> improves the retention property by the friction material <NUM> of the lubricating oil present on the friction material <NUM>.

As can be understood from the above description of the operation, according to the above embodiment, in the wet friction plate <NUM> and the method for manufacturing the wet friction plate, the fine groove <NUM> is formed on the surface of the friction material <NUM> by continuously emitting the laser beam L without interruption between the exposed portion <NUM> on the plate surface of the core metal <NUM> and the friction material <NUM>. Therefore, positioning accuracy of the core metal <NUM> with respect to the laser head <NUM> that emits the laser beam L can be relaxed. Further, irradiation control of the laser beam L can also be simplified. Therefore, efficiency of the work of forming the fine groove <NUM> on the friction material <NUM> can be improved.

Furthermore, the implementation of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention. In the modifications described below, the same components as the wet friction plate <NUM> in the above embodiment are denoted by the same reference numerals as the reference numerals given to the wet friction plate <NUM>, and descriptions thereof will be omitted.

For example, in the above embodiment, the resin layer <NUM> is made of a resin material having adhesiveness to the friction material <NUM>. However, the resin layer <NUM> does not necessarily have to have adhesiveness. The resin layer <NUM> may have a function of hindering progress of the laser beam L or reducing light intensity of the laser beam L. Therefore, the resin layer <NUM> can be made of a resin material that does not have adhesiveness to the friction material <NUM>. In this case, the friction material <NUM> is fixed on the core metal <NUM> by the adhesive applied onto the core metal <NUM> or onto the resin layer <NUM> made of the resin material having no adhesiveness.

In the above embodiment, the resin layer <NUM> is formed to be transparent or translucent to the extent that the surface of the core metal <NUM> can be visually recognized by a human. However, the resin layer <NUM> can also be formed to be opaque so that the surface of the core metal <NUM> cannot be visually recognized. In this case, the resin layer <NUM> can be formed in a mirror surface color or a metallic color that reflects the laser beam L, in addition to a dark color such as black.

In the above embodiment, the resin layer <NUM> is formed on each of the entire two plate surfaces of the core metal <NUM>. However, the resin layer <NUM> may be formed on a portion in which the friction material <NUM> is not provided on the plate surface of the core metal <NUM>, that is, on at least a part of the exposed portion <NUM> which is a portion exposed to the outside, more specifically, on a path where the laser beam L is displaced when the fine groove <NUM> is formed in the friction material <NUM>. Therefore, the resin layer <NUM> may be formed only on the exposed portion <NUM> in which the friction material <NUM> is not provided on the plate surface of the core metal <NUM>. Alternatively, as illustrated in <FIG>, the resin layer <NUM> may also be formed only in a region extending in an annular shape in the circumferential direction, corresponding to a radial range of the fine groove <NUM> formed in the friction material <NUM>. Note that in <FIG>, the resin layer <NUM> is shown by hatching.

In the above embodiment, the wet friction plate <NUM> is configured such that the resin layer <NUM> is formed on each of the two plate surfaces of the core metal <NUM>. Thus, in the wet friction plate <NUM>, it is possible to prevent or reduce the formation of the fine groove <NUM> in the exposed portion <NUM> of the core metal <NUM>. However, if it is permissible for the fine groove <NUM> to be formed in the exposed portion <NUM> of the core metal <NUM>, the wet friction plate <NUM> can also be configured such that the resin layer <NUM> is omitted. This can simplify the configuration of the wet friction plate <NUM>. Further, since the resin layer forming step can be omitted also in the manufacturing process of the wet friction plate, a manufacturing load can be reduced.

In the wet friction plate <NUM>, the resin layer <NUM> formed on each of the two plate surfaces of the core metal <NUM> can also be removed after the fine groove <NUM> is formed. Specifically, the operator can perform a resin layer removing step of removing the resin layer <NUM> formed on each of the two plate surfaces of the core metal <NUM> by using a chemical such as an organic solvent or by cutting. This can prevent an increase in weight due to formation of the resin layer <NUM> and deterioration in appearance due to the resin layer <NUM> remaining.

In the above embodiment, the fine groove <NUM> is formed in an annular shape that intermittently extends in the circumferential direction of the core metal <NUM>, and is formed in a continuous annular shape together with the fine groove <NUM> as a whole. However, the fine groove <NUM> is formed in a shape that can control the retention property and discharge property of the lubricating oil on the friction material <NUM>. Therefore, the fine groove <NUM> can be formed in a shape other than the annular shape, for example, in a spiral shape that extends intermittently in the circumferential direction of the core metal <NUM> as illustrated in each of <FIG> and <FIG>, and can be formed in a continuous spiral shape together with the fine groove <NUM> as a whole. Further, as illustrated in <FIG>, the fine groove <NUM> may also be formed in a linear shape or a curved shape in the radial direction of the core metal.

In the above embodiment, the friction material <NUM> is provided by arranging a plurality of small pieces intermittently in the circumferential direction of the core metal <NUM> via the gap forming the oil groove <NUM>. However, the friction material <NUM> is appropriately provided according to a specification of the wet multiple-plate clutch device <NUM>. Therefore, as illustrated in <FIG>, the friction material <NUM> can also be formed in an annular shape that continuously extends in the circumferential direction of the core metal <NUM>. That is, the wet friction plate <NUM> can be configured so that the oil groove <NUM> is omitted. In this case, the fine groove <NUM> can be formed in an annular shape or a spiral shape that extends continuously or intermittently in the circumferential direction of the core metal <NUM>.

In the above embodiment, in the wet friction plate <NUM>, the fine groove <NUM> is formed in the exposed portion <NUM> of the core metal <NUM>. However, depending on formation mode of the resin layer <NUM> formed on the exposed portion <NUM>, it is possible to prevent the fine groove <NUM> from being formed in the exposed portion <NUM>. Specifically, by increasing the thickness of the resin layer <NUM> or by reducing permeability of the laser beam L to improve reflectance or absorptance of the light, it is possible to prevent the fine groove <NUM> from being formed in the exposed portion <NUM>. Note that the fine groove <NUM> may be formed in the resin layer <NUM> due to heat when the laser beam L is absorbed by the resin layer <NUM> or when the fine groove <NUM> is formed in the exposed portion <NUM>.

In the configuration described in the above embodiment, in the fine groove forming step of the fourth step, the laser beam L is started to be emitted on the exposed portion <NUM> of the core metal <NUM>, and the laser beam L is displaced and irradiated onto the friction material <NUM>. This prevents the friction material <NUM> on the core metal <NUM> from being irradiated with the unstable laser beam L at the time of emission and immediately after the emission, so that the fine groove <NUM> can be stably formed. However, in the fine groove forming step, as illustrated in <FIG>, the emission of the laser beam L is started at a position P4 outside the core metal <NUM> (inside the core metal <NUM> in <FIG>), and the laser light L can also be displaced and irradiated onto the exposed portion <NUM> of the core metal <NUM> or onto the friction material <NUM>. This prevents the exposed portion <NUM> of the core metal <NUM> or the friction material <NUM> from being irradiated with the unstable laser beam at the time of emission and immediately after the emission, so that the fine grooves <NUM> and <NUM> can be stably formed. In the wet friction plate <NUM> illustrated in <FIG>, a spiral fine groove <NUM> is continuously formed from the inner peripheral side to the outer peripheral side of the core metal <NUM>, and then the emission of the laser beam L is stopped after the laser beam L is continuously emitted through an outer peripheral portion of the friction material <NUM> up to a position P5 outside an outer peripheral portion of the core metal <NUM>.

In the above embodiment, the wet friction plate <NUM> is held by the friction plate holder <NUM>, which is rotationally driven integrally with the shaft <NUM>. That is, the wet friction plate <NUM> is used as an opposing plate, and the opposing plate is disposed to face the clutch plate <NUM> that is rotationally driven by the rotational driving force of the engine, and is rotationally driven integrally with the shaft <NUM> that is an output shaft of the wet multiple-plate clutch device <NUM>. However, the wet friction plate <NUM> can also be used as the clutch plate <NUM> as a drive side plate that is rotationally driven by the rotational driving force of the engine.

In the above embodiment, the laser processing apparatus <NUM> is configured such that the laser head <NUM> can be displaced in three axial directions, which are orthogonal to each other in the X-axis direction, the Y-axis direction, and the Z-axis direction. However, if the laser machining apparatus <NUM> is configured such that the fine groove <NUM> can be formed on the friction material <NUM> on the core metal <NUM>, another configuration can be employed. Therefore, the laser processing apparatus <NUM> can be configured such that a galvano scanner or a polygon mirror is provided in the laser head <NUM> to scan the laser beam L in the X-axis direction and the Y-axis direction, in place of or in addition to displacement of the laser head <NUM> and/or the work table <NUM>. Further, the laser processing apparatus <NUM> can also be configured to hold the core metal <NUM> to which the friction material <NUM> is attached on the work table <NUM> configured to be movable or fixed such that the core metal <NUM> on the work table <NUM> is rotated or scanned with the laser beam L in the X-axis direction and the Y-axis direction.

In the above embodiment, an example in which the wet friction plate according to the present invention is used as the wet friction plate <NUM> used in the wet multiple-plate clutch device <NUM> has been described. However, the wet friction plate according to the present invention may be any wet friction plate used in oil. The wet friction plate according to the present invention can also be used as the wet friction plate used in a braking device for braking rotational motion by the prime mover in addition to the wet multiple-plate clutch device <NUM>.

Claim 1:
A method for manufacturing a wet friction plate (<NUM>) in which a friction material (<NUM>) is provided in a circumferential direction on a surface of a core metal (<NUM>) formed in a flat plate annular shape, the method comprising:
a friction material fixing step of attaching a plurality of the friction materials to the surface of the core metal (<NUM>); and
a fine groove forming step of forming a recessed fine groove (<NUM>) on a surface of the friction material (<NUM>) by irradiating the core metal with laser beam while being displaced with respect to the core metal (<NUM>), wherein
in the fine groove forming step, the fine groove (<NUM>) is formed on the surface of the friction material (<NUM>) by continuously emitting the laser beam without interruption between an exposed portion of a plate surface of the core metal (<NUM>) and the friction material (<NUM>).