Centrifugal clutch and method for regeneration or modification of clutch characteristics of centrifugal clutch

Abstract

Provided are: a centrifugal clutch that can simplify the job of replacing assist cam pieces as well as the job of assembling the centrifugal clutch; and a method for regeneration or modification of the clutch characteristics of the centrifugal clutch. A centrifugal clutch 200 is provided with a clutch weight 240 and an assist cam piece 220 on a drive plate 210 that is rotationally driven by the driving force of an engine. The clutch weight 240 has formed therein a weight-side follower part 245 that is rotationally displaced to the clutch-outer 250 side and that also rides up on the assist cam piece 220. The assist cam piece 220 is formed in an approximately square shape in plan view, and has, on the four lateral faces thereof, a first cam surface 221, a second cam surface 222, a third cam surface 223, and a fourth cam surface 224 that selectively slide against the weight-side follower part 245. In addition, in the assist cam piece 220, a mounting hole 225 is formed at a decentered position in a cross section of the assist cam piece.

Description

Centrifugal clutch and method for restoring or changing clutch characteristics in centrifugal clutch

[0001] This invention relates to a centrifugal clutch that blocks the transmission of rotational driving force to the driven side until the engine reaches a predetermined rotational speed, and transmits the rotational driving force to the driven side when the engine reaches the predetermined rotational speed.

[0002] Centrifugal clutches have been used in motorcycles, brush cutters, and the like to transmit rotational drive force to a driven side when the engine reaches a predetermined rotation speed. For example, Patent Document 1 below discloses a centrifugal clutch including a drive plate that is rotationally driven by the rotational drive force from the engine and a clutch weight that is rotatably supported on the drive plate and opens radially outward as the drive plate rotates, thereby being pressed against the clutch outer. In this case, the centrifugal clutch includes a pair of cam-forming protrusions (hereinafter referred to as "assist cam bodies") and a driven part between the drive plate and the clutch weight, and is configured so that the pair of cams can quickly and forcefully press the clutch weight against the clutch outer.

[0003] Japanese Patent Application Laid-Open No. 2018-9675

[0004] However, the centrifugal clutch described in Patent Document 1 has a problem in that the preparation of the assist cam body, which is configured in a roller shape, is complicated when replacing the assist cam body or when assembling the centrifugal clutch.

[0005] For example, in a conventional centrifugal clutch, if the assist cam body needs to be replaced due to wear or damage, a new assist cam body must be prepared, and even if it is desired to change the clutch characteristics of the centrifugal clutch by changing the cam characteristics formed by the assist cam body and the driven part, a new assist cam body that exhibits the desired cam characteristics must be prepared separately.Furthermore, in the process of assembling multiple types of centrifugal clutches with different cam characteristics (clutch characteristics), an assist cam body must be prepared for each desired cam characteristic.

[0006] The present invention has been made to address the above-mentioned problems, and its purpose is to provide a centrifugal clutch and a method for restoring or changing the clutch characteristics of a centrifugal clutch that can simplify the work of replacing an assist cam body or the work of assembling a centrifugal clutch.

[0007] In order to achieve the above object, the present invention is characterized by comprising a drive plate that is rotated by receiving a driving force from a drive source, a plurality of clutch weights that are displaced so as to contact or move away from the cylindrical surface of the clutch outer by the centrifugal force caused by the rotation of the drive plate, an assist cam body that has a cam surface and is rotatably mounted on the drive plate, and a weight-side follower part that is mounted on the clutch weight and is pressed by the cam surface of the assist cam body when the clutch weight is displaced, and the assist cam body has a plurality of cam surfaces formed thereon, and one of these plurality of cam surfaces presses the weight-side follower part.

[0008] According to this, because the centrifugal clutch has multiple cam surfaces formed on the assist cam body, the desired cam characteristics can be obtained by attaching the desired cam surface to the drive plate so that it faces the weight-side driven portion, simplifying the work of replacing the assist cam body or the work of assembling the centrifugal clutch. In this case, the centrifugal clutch can maintain the cam characteristics or restore changed cam characteristics by forming the multiple cam surfaces that make up the assist cam body in the same shape, and can change the cam characteristics by forming the multiple cam surfaces in different shapes.

[0009] Another feature of the present invention is that in the centrifugal clutch, the assist cam body has at least one of the multiple cam surfaces formed as a flat surface, and the weight-side follower part is formed as a flat surface that makes surface contact with the cam surface formed as a flat surface.

[0010] According to this, the centrifugal clutch reduces the surface pressure by having the assist cam body and the weight side follower part in surface contact, thereby suppressing deterioration or damage to the assist cam body and the weight side follower part and allowing the cam to exhibit stable characteristics over a long period of time.

[0011] Another feature of the present invention is that in the centrifugal clutch, at least one of the multiple cam surfaces of the assist cam body is formed by a curved surface, and the weight side follower part is formed by a curved surface that makes surface contact or line contact with the cam surface formed by the curved surface.

[0012] According to this, since the assist cam body of the centrifugal clutch is formed with a convex or concave curved surface, the two can be configured to have surface contact or line contact depending on the shape of the weight-side driven part. In other words, in the centrifugal clutch according to the present invention, the assist cam body formed with a curved surface can be used in common for centrifugal clutches having weight-side driven parts that require surface contact and centrifugal clutches having weight-side driven parts that require line contact.

[0013] Another feature of the present invention is that in the centrifugal clutch, the assist cam body is formed such that the lengths of at least two of the multiple cam surfaces in a direction parallel to the rotational center axis of the assist cam body are different from each other.

[0014] According to this, the centrifugal clutch has at least two of the multiple cam surfaces that make up the assist cam body that have different lengths in the direction parallel to the rotational center axis of the assist cam body (i.e., they are formed with different shapes), so that the cam characteristics, i.e., the clutch characteristics, can be changed by changing the cam surface relative to the weight side follower.

[0015] Another feature of the present invention is that in the centrifugal clutch, the assist cam body is formed such that the distances from the rotational center axis of the assist cam body to at least two of the multiple cam surfaces are different from each other.

[0016] According to this, the centrifugal clutch is formed such that at least two of the multiple cam surfaces constituting the assist cam body are spaced apart from each other by different distances from the rotational axis of the assist cam body. Here, the distances of the two cam surfaces from the rotational axis of the assist cam body refer to the distances to the rotational axis at corresponding positions on the two cam surfaces, e.g., the distances (shortest distances) to the closest portions of the two cam surfaces from the rotational axis of the assist cam body. In other words, the rotational axis of the assist cam body is located eccentrically with respect to the outer surface including the cam surfaces in a cross section perpendicular to the direction of the rotational axis of the assist cam body. As a result, the centrifugal clutch can change the surface pressure (in other words, the cam thrust) by changing the cam surface relative to the weight-side driven part, thereby changing the cam characteristics, i.e., the clutch characteristics.

[0017] Another feature of the present invention is that in the centrifugal clutch, the assist cam body is formed in a substantially rectangular shape in a plan view and has two or more and four or less cam surfaces.

[0018] According to this, the centrifugal clutch has an assist cam body that is formed in a substantially rectangular shape in plan view and has two or more and four or less cam surfaces, so that one assist cam body can exhibit up to four cam characteristics. Note that the term "substantially rectangular" in plan view of the assist cam body does not necessarily mean a strict quadrilateral shape, but rather means that the assist cam body is formed in various rectangular shapes such as a square or rectangle even if the corners or sides are strictly curved.

[0019] Another feature of the present invention is that in the centrifugal clutch, the assist cam body is formed in a substantially triangular shape in a plan view and has two or more and three or less cam surfaces.

[0020] According to this, the centrifugal clutch has an assist cam body that is formed into a substantially triangular shape in plan view and has two or three cam surfaces, so that one assist cam body can exhibit up to three cam characteristics. Note that the term "substantially triangular" in plan view of the assist cam body does not necessarily mean a strict triangular shape, but rather means that the assist cam body is formed into various triangular shapes such as an equilateral triangle, an isosceles triangle, or a right-angled triangle, even if the corners or sides are strictly curved.

[0021] Another feature of the present invention is that in the centrifugal clutch, the assist cam body has at least two cam surfaces of the plurality of cam surfaces that have different surface roughnesses.

[0022] According to this, the centrifugal clutch has at least two of the multiple cam surfaces that make up the assist cam body having different surface roughnesses, resulting in different shapes, so that the cam characteristics, i.e., the clutch characteristics, can be changed by changing the cam surface relative to the weight side follower.

[0023] Furthermore, the present invention can be implemented not only as an invention of a centrifugal clutch, but also as an invention of a method for restoring or changing the clutch characteristics of a centrifugal clutch.

[0024] Specifically, the method for restoring or changing clutch characteristics in a centrifugal clutch includes a drive plate that rotates by receiving a driving force from a drive source, multiple clutch weights that are displaced by centrifugal force generated by the rotation of the drive plate so as to contact or separate from the cylindrical surface of the clutch outer, an assist cam body having a cam surface and rotatably mounted on the drive plate, and a weight-side follower portion that is mounted on the clutch weight and is pressed by the cam surface of the assist cam body when the clutch weight is displaced, the assist cam body having multiple cam surfaces, one of which presses the weight-side follower portion, and at least two of the multiple cam surfaces that make up the assist cam body may be formed to have the same or different cam characteristics, and the cam surface of the assist cam body may be changed so that the cam surface with the same or different cam characteristics presses the weight-side follower portion. This method for restoring or changing clutch characteristics in a centrifugal clutch can be expected to achieve the same effects as those of the centrifugal clutch described above.

[0025] 1 is a plan sectional view schematically showing the configuration of a power transmission mechanism equipped with a centrifugal clutch according to the present invention. FIG. 2 is a side view of the centrifugal clutch as seen from line 2-2 shown in FIG. 1. FIG. 3 is a perspective view showing how an assist cam body is assembled to a drive plate in the centrifugal clutches shown in FIGS. 1 and 2, respectively. FIG. 4 is a perspective view showing how a clutch weight is assembled to a drive plate in the centrifugal clutches shown in FIGS. 1 and 2, respectively. FIG. 5 is a partially enlarged view showing the centrifugal clutch shown in FIG. 2 in a clutch-off state in which the clutch shoe is not in contact with the clutch outer. FIG. 6 is a partially enlarged view showing the centrifugal clutch shown in FIG. 5 in a clutch-on state in which the clutch shoe is pressed against the clutch outer. FIG. 7 is a partially enlarged view showing the state in which the clutch weight rotates radially inward of the drive plate in the centrifugal clutch shown in FIG. 5. FIG. 8 is a partially enlarged view for explaining the cam angle when the first cam surface of the assist cam body slides on the weight-side driven portion of the clutch weight in the centrifugal clutch shown in FIG. 5. FIG. 9 is a partially enlarged view for explaining the cam angle when the third cam surface of the assist cam body slides on the weight-side driven portion of the clutch weight in the centrifugal clutch shown in FIG. 5. FIG. 10 is a plan view showing a schematic external configuration of an assist cam body according to a modified example of the present invention. (A) to (C) show schematic diagrams of the external configuration of an assist cam body according to another modified example of the present invention, where (A) is a plan view of an assist cam body that is rectangular in plan view, (B) is a plan view of an assist cam body that includes an arc-shaped cam surface on its cam surface, and (C) is a plan view of an assist cam body in which a mounting hole is formed in an eccentric position in a cross section. (A) to (C) show schematic diagrams of the external configuration of an assist cam body according to another modified example of the present invention, where (A) is a plan view of an assist cam body that is equilateral triangular in plan view, (B) is a plan view of an assist cam body in which a cam surface is formed into an arc-shaped cam surface, and (C) is a plan view of an assist cam body in which a mounting hole is formed in an eccentric position in a cross section. (A) and (B) show schematic diagrams of the external configuration of an assist cam body according to another modified example of the present invention, where (A) is a plan view of an assist cam body that is elliptical in plan view, and (B) is a plan view of an assist cam body in which a mounting hole is formed in an eccentric position in a cross section.10A and 10B are perspective views showing the outline of the external configuration of an assist cam body according to another modified example of the present invention, and a state in which an assist cam body according to another modified example of the present invention is attached to a drive plate.

[0026] An embodiment of a centrifugal clutch according to the present invention will now be described with reference to the drawings. Fig. 1 is a plan cross-sectional view schematically showing the configuration of a power transmission mechanism 100 equipped with a centrifugal clutch 200 according to the present invention. Fig. 2 is a side view of the centrifugal clutch 200 as seen from line 2-2 shown in Fig. 1. In this case, the upper half of Fig. 1 shows the state in which the movable driven plate 134 is closest to the fixed driven plate 131, and the lower half shows the state in which the movable driven plate 134 is furthest from the fixed driven plate 131.

[0027] The power transmission mechanism 100 equipped with this centrifugal clutch 200 is a mechanical device that is provided between an engine and a rear wheel, which is a drive wheel, mainly in a motorcycle such as a scooter, and transmits or cuts off the rotational driving force to the rear wheel while automatically changing the reduction ratio according to the engine speed. Specifically, the centrifugal clutch 200 is a mechanical device that cuts off the transmission of the rotational driving force to the driven side until the engine reaches a predetermined speed, and transmits the rotational driving force to the driven side when the engine reaches the predetermined speed.

[0028] (Configuration of Centrifugal Clutch 200) This power transmission mechanism 100 mainly includes a transmission 101 and a centrifugal clutch 200. The transmission 101 is a mechanical device that continuously reduces the rotational driving force from an engine (not shown) and transmits it to the centrifugal clutch 200, and is mainly configured with a drive pulley 110, a V-belt 120, and a driven pulley 130. Of these, the drive pulley 110 is a mechanical device that is provided on a crankshaft 111 extending from the engine and is directly driven to rotate by the rotational driving force of the engine, and is mainly configured with a fixed drive plate 112 and a movable drive plate 113.

[0029] The fixed drive plate 112 is a component that rotates while sandwiching and holding the V-belt 120 together with the movable drive plate 113, and is made of metal material formed into a conical cylindrical shape. This fixed drive plate 112 is fixedly attached to the crankshaft 111 with its convex surface facing the movable drive plate 113 (engine side). In other words, the fixed drive plate 112 always rotates integrally with the crankshaft 111. In addition, multiple heat dissipation fins 112a are provided on the concave surface of the fixed drive plate 112 radially from the axis of the crankshaft 111.

[0030] The movable drive plate 113 is a component that rotates while sandwiching and holding the V-belt 120 together with the fixed drive plate 112, and is made of a metal material such as aluminum formed into a conical cylindrical shape. The movable drive plate 113 is attached to the crankshaft 111 with its convex surface facing the fixed drive plate 112. In this case, the movable drive plate 113 is attached via an impregnated bushing onto a sleeve bearing 114 that is fixedly fitted to the crankshaft 111, and is attached to the sleeve bearing 114 so that it can slide axially and circumferentially.

[0031] Meanwhile, a plurality of roller weights 115 are provided on the concave surface of the movable drive plate 113, and are pressed by a ramp plate 116. The roller weights 115 are components that cooperate with the ramp plate 116 to press the movable drive plate 113 toward the fixed drive plate 112 by displacing radially outward as the rotation speed of the movable drive plate 113 increases, and are made of a metal material such as aluminum formed into a cylindrical shape. The ramp plate 116 is a component that presses the roller weights 115 toward the movable drive plate 113, and is made by bending a metal plate such as aluminum toward the movable drive plate 113.

[0032] The V-belt 120 is a component for transmitting the rotational driving force of the drive pulley 110 to the driven pulley 130, and is formed in the shape of an endless ring with a core wire covered with an elastic material such as rubber. The V-belt 120 is disposed between the fixed drive plate 112 and the movable drive plate 113, and between the fixed driven plate 131 and the movable driven plate 134 of the driven pulley 130, and is stretched between the drive pulley 110 and the driven pulley 130.

[0033] The driven pulley 130 is a mechanical device that is driven to rotate by the rotational driving force from the engine transmitted via the drive pulley 110 and the V-belt 120, respectively, and is mainly composed of a fixed driven plate 131 and a movable driven plate 134, respectively.

[0034] The fixed driven plate 131 is a component that rotates while sandwiching and holding the V-belt 120 together with the movable driven plate 134, and is made of a metal material such as aluminum formed into a conical cylindrical shape. The fixed driven plate 131 is fixedly attached to the driven sleeve 132 with the convex surface facing the movable driven plate 134.

[0035] The driven sleeve 132 is a cylindrical metal (e.g., aluminum) part that rotates integrally with the fixed driven plate 131, and is attached to the drive shaft 133 via a bearing so as to be relatively rotatable. The drive shaft 133 is a metal (e.g., steel) rotating shaft that drives the rear wheel of the motorcycle on which the power transmission mechanism 100 is mounted, via a transmission (not shown). In this case, the rear wheel of the motorcycle is attached to one end (the right end in the figure) of the drive shaft 133.

[0036] The movable driven plate 134 is a component that rotates while sandwiching and holding the V-belt 120 together with the fixed driven plate 131, and is made of a metal material such as aluminum formed into a conical cylindrical shape. The movable driven plate 134 is fitted onto the driven sleeve 132 so as to be axially slidable, with the convex surface facing the fixed driven plate 131.

[0037] Meanwhile, a torque spring 135 is provided on the concave surface of movable driven plate 134, between it and drive plate 210 of centrifugal clutch 200. Torque spring 135 is a coil spring that elastically presses movable driven plate 134 toward fixed driven plate 131. In other words, this transmission 101 continuously changes the engine speed depending on the relative size of the diameter of the V-belt 120 defined by the distance between fixed drive plate 112 and movable drive plate 113, and the diameter of the V-belt 120 defined by the distance between fixed driven plate 131 and movable driven plate 134. Centrifugal clutches 200 are provided on the tip ends of driven sleeve 132 and drive shaft 133.

[0038] The centrifugal clutch 200 is a mechanical device that transmits or cuts off the rotational driving force of the engine transmitted via the transmission 101 to the drive shaft 133, and is mainly composed of a drive plate 210, three clutch weights 240, and a clutch outer 250.

[0039] The drive plate 210 is a component that rotates integrally with the driven sleeve 132, and is configured as a stepped disk made of a metal material such as aluminum. More specifically, as shown in Figures 3 and 4, the drive plate 210 has a flat bottom 211 with a through-hole 211a formed in the center thereof, through which the driven sleeve 132 passes, and a cylindrical portion 212 that stands upright around the bottom 211, and a flange-like protruding flange 213 formed at the tip of the cylindrical portion 212. Three swing support pins 214, three cam body support pins 217, and three damper support pins 230 are provided on the flange 213 along the circumferential direction, each at equal intervals.

[0040] The swing support pin 214 is a component for rotatably supporting one end of a clutch weight 240 (described later) and swinging the other end, and is configured as a stepped metal rod. In this case, the swing support pin 214 is fixedly attached to the flange portion 213 with an attachment bolt 214a. This swing support pin 214 supports the clutch weight 240 while its outer periphery passes through a pin slide hole 241 of the clutch weight 240 via a fulcrum-side slide member 215. In this case, a side plate 216 is attached to the tip of the swing support pin 214 that protrudes through the pin slide hole 241 with an E-ring 214b, and the clutch weight 240 is supported while being sandwiched between the attachment bolt 214a and the side plate 216.

[0041] The fulcrum-side sliding member 215 is a component disposed between the swing support pin 214 and the pin slide hole 241 to improve the sliding property between them, and is made of a cylindrical resin material. The fulcrum-side sliding member 215 has an inner diameter and an outer diameter that allow it to rotate and slide relative to the swing support pin 214 and the pin slide hole 241, respectively, that is, is formed with dimensional tolerances that provide a clearance fit relative to the swing support pin 214 and the pin slide hole 241, respectively.

[0042] Furthermore, a heat-resistant and abrasion-resistant thermoplastic resin or thermosetting resin, preferably an engineering plastic or super engineering plastic, can be used as the resin material constituting the fulcrum-side sliding member 215. Specifically, polyether ether ketone resin (PEEK), polyphenylene sulfide resin (PPS), polyamide-imide resin (PAI), fluororesin (PTFE), or polyimide resin (PI) can be used as the thermoplastic resin, and diallyl phthalate resin (PDAP), epoxy resin (EP), or silicone resin (SI) can be used as the thermosetting resin.

[0043] The side plate 216 is a component that prevents the three clutch weights 240 from coming off the swing support pins 214, and is made of a metal material formed into a ring shape. The side plate 216 is disposed on the opposite side of the drive plate 210 from the three clutch weights 240, facing each of the clutch weights 240.

[0044] The cam body support pin 217 is a component for supporting the assist cam body 220 in a rotatable state, and is made up of a stepped metal rod. The cam body support pin 217 is fixedly attached by a mounting bolt 217 a onto the flange 213 that faces the portion of the clutch weight 240 closer to the tip end of the clutch weight 240 than the pin slide hole 241.

[0045] Assist cam body 220 is a component for generating a cam thrust that presses clutch weight 240 toward clutch outer 250, and is configured by forming a resin material into a substantially rectangular cylindrical shape in a plan view. More specifically, assist cam body 220 is configured by the same resin material as fulcrum side sliding member 215, and is configured to include first cam surface 221, second cam surface 222, third cam surface 223, fourth cam surface 224, and mounting holes 225.

[0046] First cam surface 221, second cam surface 222, third cam surface 223, and fourth cam surface 224 are portions against which weight-side follower portion 245 of clutch weight 240 is pressed and slides, thereby generating a cam thrust, which is a pressing force against clutch weight 240. These first cam surface 221, second cam surface 222, third cam surface 223, and fourth cam surface 224 respectively constitute four side surfaces of assist cam body 220, which is formed into a substantially square cylindrical shape in a plan view. Here, the term "substantially" in "substantially rectangular" or "substantially square" means not only a strict rectangular or square shape but also a substantially rectangular or square shape, and "substantially" hereinafter has the same meaning.

[0047] In this embodiment, the first cam surface 221 and the third cam surface 223 are formed to extend parallel to each other and form side surfaces opposite each other, while the second cam surface 222 and the fourth cam surface 224 are formed to extend parallel to each other in directions perpendicular to the first cam surface 221 and the third cam surface 223 and form side surfaces opposite each other. In this case, the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224 are formed to have the same shape and the same surface roughness. Furthermore, the four corners of the assist cam body 220 are each formed into a convex arc-shaped curved surface.

[0048] The mounting hole 225 is a through-hole through which the cam body support pin 217 provided on the drive plate 210 passes in a rotatable and slidable manner, and is formed with an inner diameter that allows the cam body support pin 217 to rotate and slide, i.e., with a dimensional tolerance that provides a so-called clearance fit with the cam body support pin 217. The mounting hole 225 is formed in a position that is shifted from the center of gravity of the assist cam body 220 in a plan view, i.e., an eccentric position. Specifically, the mounting hole 225 is formed in a position between the first cam surface 221 and the third cam surface 223 that is biased toward the third cam surface 223, and with the center of the cylinder being the central position between the second cam surface 222 and the fourth cam surface 224.

[0049] The damper receiving pin 230 is a component for supporting the damper 231, and is made of a metal rod. The damper 231 is a component that guides the swinging motion of the other end of the clutch weight 240 to move toward or away from the clutch outer 250, and acts as a buffer when the other end is separated from the clutch outer 250, and is made of a cylindrical elastic body such as rubber or elastomer. The damper 231 is fixedly fitted onto the outer circumferential surface of the damper receiving pin 230.

[0050] The three clutch weights 240 are components that transmit or block the rotational driving force from the engine to the drive shaft 133 by contacting or separating from the clutch outer 250 via the clutch shoe 243 depending on the rotation speed of the drive plate 210, and are made by forming a metal material (e.g., zinc) into a curved shape that extends circumferentially around the drive plate 210.

[0051] These clutch weights 240 are each rotatably supported at one end by a fulcrum-side sliding member 215 and a swing support pin 214 that pass through a pin slide hole 241, and are connected at the other end to the adjacent clutch weight 240 by a connecting spring 242 made of a metal coil spring, and are pulled toward the inside of the drive plate 210. In other words, the clutch weights 240 are supported on the drive plate 210 via the swing support pin 214, fulcrum-side sliding member 215, and pin slide hole 241, with the outer periphery of the other end swingable relative to the clutch outer 250 via a clutch shoe 243.

[0052] 2, in order to make it easier to understand the configuration of the clutch weights 240, one of the three clutch weights 240 is shown cut away at two locations along different thickness directions. Also, in FIG. 2, the rotational drive directions of the drive plate 210 and the clutch outer 250 in the centrifugal clutch 200 are indicated by dashed arrows.

[0053] The pin slide hole 241 is a portion of the drive plate 210 that rotatably and slidably fits onto the swing support pin 214, and is configured as a through hole that penetrates the clutch weight 240 in the thickness direction. The pin slide hole 241 is formed in an elongated hole shape so that when the clutch shoe 243 comes into contact with the clutch outer 250, the one end side of the clutch weight 240 is displaced rearward in the rotational drive direction of the drive plate 210. In this embodiment, the pin slide hole 241 is formed so as to extend in an arc shape toward the front side in the rotational drive direction of the drive plate 210.

[0054] The clutch shoe 243 is a component for increasing the frictional force against the inner peripheral surface of the clutch outer 250, and is configured by forming a friction material into an arc-shaped plate. The clutch shoe 243 is provided on the outer peripheral surface of each clutch weight 240 on the tip side opposite the pin slide hole 241.

[0055] In addition, on the surface of each clutch weight 240 facing the drive plate 210, an assist cam body accommodating section 244 is formed with a concave recessed shape to cover the assist cam body 220, and a damper groove 246 is formed with a concave recessed shape to cover the damper 231.

[0056] The assist cam body accommodating portion 244 is the portion where the weight side follower portion 245 that rides on the assist cam body 220 is formed, and is formed in the shape of a groove that opens onto the inner peripheral surface of the clutch weight 240 and extends radially outward, and the innermost portion is formed in a concave shape so as not to come into contact with the assist cam body 220.

[0057] The weight-side follower 245 is a part that cooperates with the assist cam body 220 to displace the clutch weight 240 toward the clutch outer 250, and is configured with a smooth flat surface facing the rear side in the rotational drive direction of the drive plate 210. More specifically, the weight-side follower 245 has a sliding surface that is pressed in surface contact against one of the first to fourth cam surfaces 221 to 224 of the assist cam body 220 and is formed on a flat surface that extends linearly rearward and outward in the rotational drive direction of the drive plate 210.

[0058] The damper groove 246 is the part that houses the damper 231 in a sandwiched state, and is formed in the shape of a groove that opens to the inner surface of the clutch weight 240 and extends while curving along the rotational displacement direction in which the clutch weight 240 approaches or moves away from the clutch outer 250.

[0059] Clutch outer 250 is a component that rotates integrally with drive shaft 133, and is configured by forming a metal material into a cup shape that covers the outer circumferential surface of drive plate 210 and clutch weight 240. In other words, clutch outer 250 is configured to have a cylindrical surface 251 that comes into frictional contact with clutch shoe 243 of clutch weight 240 that is displaced toward the outer periphery of drive plate 210.

[0060] (Assembly of Centrifugal Clutch 200) Next, a description will be given of the assembly work of the centrifugal clutch 200 configured as described above. Regarding the assembly work of the centrifugal clutch 200, only the part directly related to the present invention, i.e., the work before and after assembling the assist cam body 220, will be described.

[0061] The worker prepares three assist cam bodies 220 for one drive plate 210. In this case, the drive plate 210 has three swing support pins 214, three cam body support pins 217, and three damper receiving pins 230 each mounted on the flange 213 (see FIG. 3).

[0062] Next, the worker attaches the assist cam body 220 to each of the three cam body support pins 217. Specifically, the worker passes the cam body support pins 217 through the mounting holes 225 in the assist cam body 220. In this case, the worker fits the assist cam body 220 onto the cam body support pins 217 with one of the first cam surface 221 to the fourth cam surface 224 of the assist cam body 220, which slides on the weight-side follower 245 of the clutch weight 240, facing the weight-side follower 245. In this embodiment, the worker fits the assist cam body 220 onto the cam body support pins 217 with the first cam surface 221 of the assist cam body 220 facing the weight-side follower 245 of the clutch weight 240 (see FIG. 4 ).

[0063] Next, the worker prepares three each of the fulcrum-side sliding members 215 and dampers 231, and fits the fulcrum-side sliding members 215 onto the swing support pins 214, and also fits the dampers 231 onto the damper receiving pins 230. Next, the worker prepares three each of the clutch weights 240 and connecting springs 242, and connects the three clutch weights 240 in an annular shape with the connecting springs 242.

[0064] Next, the worker attaches the connected body, in which the three clutch weights 240 are connected in an annular shape by the connecting springs 242, to the drive plate 210. Specifically, the worker places the three clutch weights 240 on the drive plate 210 by passing the swing support pins 214 of the drive plate 210 through the pin slide holes 241 in the clutch weights 240. In this case, the assist cam bodies 220 that fit onto the cam body support pins 217 are positioned in the respective assist cam body accommodating portions 244 of the respective clutch weights 240, and the dampers 231 that fit onto the damper receiving pins 230 are positioned in the respective damper grooves 246.

[0065] Next, the worker prepares one side plate 216 and three E-rings 214b, and arranges the side plate 216 so that it covers the three clutch weights 240. In this case, the worker arranges the side plate 216 so that each swing support pin 214 penetrates the side plate 216, and then fits the E-rings 214b onto the tip ends of each swing support pin 214 that has penetrated the side plate 216, thereby fixing the side plate 216 onto the clutch weights 240. In this way, the worker can assemble the main parts of the centrifugal clutch 200.

[0066] (Operation of Centrifugal Clutch 200) Next, operation of the centrifugal clutch 200 configured as described above will be described with reference to Figures 5 to 7. Note that the E-ring 214b, side plate 216, and connecting spring 242 are omitted from Figures 5 to 7. Also, in Figures 6 and 7, the rotational drive directions of the drive plate 210 and clutch outer 250 in the centrifugal clutch 200 are indicated by thick dashed arrows. Also, in Figure 7, the rotational direction of the assist cam body 220 is indicated by thin dashed arrows.

[0067] This centrifugal clutch 200 functions as part of a power transmission mechanism 100 that is disposed between the engine and the rear drive wheel of a motorcycle (e.g., a scooter). First, when the engine is idling, the centrifugal clutch 200 cuts off the transmission of driving force between the engine and the drive shaft 133, as shown in Figure 5. Specifically, in the centrifugal clutch 200, the rotational driving force of the engine transmitted via the transmission 101 drives the drive plate 210 to rotate, thereby driving the clutch weight 240 to rotate.

[0068] However, in this case, the centrifugal clutch 200 is in a clutch-off state in which the centrifugal force acting on the clutch weight 240 is smaller than the elastic force (tensile force) of the connecting spring 242, and the clutch shoe 243 does not contact the cylindrical surface 251 of the clutch outer 250, so the rotational driving force of the engine is not transmitted to the drive shaft 133. In this clutch-off state, the weight-side follower 245 is pressed against the first cam surface 221 of the assist cam body 220 by the elastic force (tensile force) of the connecting spring 242, and maintains a state of contact.

[0069] Furthermore, in this clutch-off state, the clutch weight 240 is pulled by the tensile force of the connecting spring 242 (the connecting spring 242 hooked at a position adjacent to the weight-side follower 245) of the two connected connecting springs 242, which pulls the clutch weight 240 from a position farther from the swing support pin 214. In this case, because the pin slide hole 241 is formed in an elongated hole shape, the clutch weight 240 is displaced toward the connecting spring 242 hooked at a position adjacent to the weight-side follower 245. As a result, the swing support pin 214 is positioned at the rear end of the pin slide hole 241 in the rotational drive direction of the drive plate 210 (see FIG. 5).

[0070] Next, centrifugal clutch 200 transmits the rotational driving force of the engine to drive shaft 133 in response to an increase in engine speed due to accelerator operation by the rider of the motorcycle. Specifically, in centrifugal clutch 200, as the engine speed increases, the centrifugal force acting on clutch weight 240 becomes greater than the elastic force (tensile force) of connecting spring 242, causing clutch weight 240 to rotate radially outward around swing support pin 214. That is, as shown in FIG. 6 , as the engine speed increases, clutch weight 240 rotates toward cylindrical surface 251 of clutch outer 250 while resisting the elastic force of connecting spring 242 and the sliding resistance between damper 231 and damper groove 246, causing clutch shoe 243 to come into contact with cylindrical surface 251.

[0071] When the clutch shoe 243 comes into contact with the cylindrical surface 251, the clutch weight 240 receives a reaction force in the direction opposite to the rotational drive direction via the clutch shoe 243. In this case, the pin slide hole 241 is formed as an elongated hole along the circumferential direction of the drive plate 210, and the swing support pin 214 is located at the rear end of the pin slide hole 241 in the rotational drive direction of the drive plate 210. In other words, the clutch weight 240 is allowed to move rearward in the rotational drive direction of the drive plate 210, so the clutch weight 240 is relatively displaced in the direction opposite to the rotational drive direction of the drive plate 210 due to the reaction force received via the clutch shoe 243.

[0072] As a result, the weight-side follower 245 formed on the clutch weight 240 is pressed strongly against the assist cam body 220, as shown in Figure 7. In this case, the assist cam body 220 is rotatably supported by the cam body support pin 217, and therefore rotates counterclockwise in the figure due to the pressure from the weight-side follower 245 (see the thin dashed arrow in Figure 7). As a result, the clutch weight 240 is pressed radially outward toward the clutch outer 250 as the weight-side follower 245 rides up onto the assist cam body 220 while rotating the assist cam body 220, and the clutch shoe 243 is pressed against the cylindrical surface 251.

[0073] As a result, in the centrifugal clutch 200, after the clutch shoe 243 comes into contact with the cylindrical surface 251 of the clutch outer 250, the clutch shoe 243 is pressed against the cylindrical surface 251 in an extremely short time (in other words, instantaneously), and the clutch weight 240 is wedged between the assist cam body 220 and the clutch outer 250. This causes the centrifugal clutch 200 to enter a clutch-on state in which the rotational driving force of the engine is completely transmitted to the drive shaft 133.

[0074] In this clutch-on state, the centrifugal clutch 200 maintains a state in which the clutch shoe 243 is pressed against the cylindrical surface 251 of the clutch outer 250, so the drive plate 210 and the clutch outer 250 are rotated integrally. As a result, the motorcycle can run by rotating the rear wheel using the rotational driving force of the engine.

[0075] On the other hand, when the engine speed decreases, centrifugal clutch 200 cuts off the transmission of the rotational driving force of the engine to drive shaft 133. Specifically, as the engine speed decreases, the centrifugal force acting on clutch weight 240 becomes smaller than the elastic force (tensile force) of connecting spring 242, and clutch weight 240 rotates radially inward around swing support pin 214.

[0076] In this case, the pin slide hole 241 is formed as an elongated hole that follows the circumferential direction of the drive plate 210, and the swing support pin 214 is located slightly forward of the rear end of the pin slide hole 241 in the rotational drive direction of the drive plate 210. In other words, since the clutch weight 240 is allowed to be displaced forward in the rotational drive direction of the drive plate 210, the elastic force (tensile force) of the connecting spring 242 causes the clutch weight 240 to rotate relatively to the drive plate 210 toward the front in the rotational drive direction of the drive plate 210.

[0077] As a result, the weight-side driven part 245 rotates the assist cam body 220 clockwise as shown in the figure, and the clutch weight 240 is rotationally displaced forward in the rotational drive direction of the drive plate 210 and radially inward, returning to its original position (the position during idling) (see FIG. 5). In other words, the centrifugal clutch 200 enters a clutch-off state in which the clutch shoe 243 does not contact the clutch outer 250 and does not transmit rotational drive force.

[0078] Next, we will explain how to change the cam surface of the assist cam body 220. This centrifugal clutch 200 can reproduce or change the cam characteristics by changing the orientation of the assist cam body 220 incorporated in the centrifugal clutch 200 and changing the cam surfaces (first cam surface 221, second cam surface 222, third cam surface 223, and fourth cam surface 224) that press against the weight-side driven part 245.

[0079] Specifically, the worker removes the centrifugal clutch 200 from the motorcycle in which it is installed, and then removes the side plate 216. Next, the worker removes the three clutch weights 240 connected by the connecting springs 242 from the drive plate 210. This exposes the three assist cam bodies 220 on the drive plate 210 (see FIGS. 3 and 4).

[0080] Next, the operator rotates the assist cam body 220 held by the cam body support pin 217 around the axis of the cam body support pin 217. In this case, the operator rotates the assist cam body 220 in a direction such that any one of the second cam surface 222, the third cam surface 223, and the fourth cam surface 224 faces the weight-side driven portion 245 of the clutch weight 240. Here, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224 are formed at different positions relative to the rotation center axis O (the central axis of the mounting hole 225) than the first cam surface 221, so that the cam characteristics can be changed. It should be noted that the operator may, of course, remove the assist cam body 220 held by the cam body support pin 217, change its orientation, and then hold it again on the cam body support pin 217.

[0081] In this embodiment, the worker rotates the assist cam bodies 220 around the axis of the cam body support pin 217 so that the third cam surface 223 faces the weight-side driven portion 245 of the clutch weight 240. In this case, the worker rotates all three assist cam bodies 220 so that the same cam surface faces the weight-side driven portion 245. Then, the worker attaches the clutch weights 240 and the side plates 216 in the same manner as in the assembling work of the centrifugal clutch 200 described above to complete the centrifugal clutch 200, and then reassembles the centrifugal clutch 200 into the motorcycle.

[0082] This allows the operator to change the clutch characteristics by changing the cam characteristics of centrifugal clutch 200. Specifically, as shown in Figures 8 and 9, when assist cam body 220 is set (oriented) so that first cam surface 221 faces weight-side driven part 245, the cam angle is larger and the cam thrust is reduced compared to when assist cam body 220 is set (oriented) so that first cam surface 221 faces weight-side driven part 245, thereby reducing the pressing force with which clutch weight 240 presses clutch outer 250. In other words, first cam surface 221, second cam surface 222, third cam surface 223, and fourth cam surface 224 correspond to cam surfaces according to the present invention.

[0083] Here, the cam angle is the angle between a normal to a line passing through the sliding portion where the assist cam body 220 and the weight-side follower 245 come into contact with each other and the rotational drive center of the drive plate 210, and a sliding direction line at the sliding portion. In this case, if the sliding portion is a surface contact, the sliding direction line is the center position of the length of the sliding portion in the sliding direction. Furthermore, if at least one of the assist cam body 220 and the weight-side follower 245 is a curved surface, the sliding direction line is a tangent to the curved surface at the sliding portion. The larger this cam angle, the smaller the assist thrust, and the smaller the cam angle, the greater the assist thrust.

[0084] In this embodiment, the first cam surface 221 of the assist cam body 220 is changed to a third cam surface 223. This makes it possible to change the cam characteristics generated between the assist cam body 220 and the weight-side follower part 245. However, the second cam surface 222 and the fourth cam surface 224 of the assist cam body 220 have the same shape and are formed at the same position relative to the rotation center axis O (the center axis of the mounting hole 225). Therefore, the assist cam body 220 can maintain or reproduce the same cam characteristics by changing between the second cam surface 222 and the fourth cam surface 224.

[0085] As can be understood from the above operation explanation, according to the above embodiment, the centrifugal clutch 200 has multiple cam surfaces formed on the assist cam body 220, from the first cam surface 221 to the fourth cam surface 224, so that the desired cam characteristics can be obtained by setting (orienting) the desired cam surface on the drive plate 210 so that it faces the weight side follower part 245, and the replacement work of the assist cam body 220 or the assembly work of the centrifugal clutch 200 can be simplified.

[0086] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the scope of the present invention. In the description of each modification, the same parts as those in the above-described embodiment are designated by the same reference numerals, and redundant description will be omitted.

[0087] For example, in the above embodiment, the assist cam body 220 has the mounting hole 225, which serves as the rotational axis O of the assist cam body 220, formed at a position offset toward the third cam surface 223 between the first cam surface 221 and the third cam surface 223 in a plan view, and at a central position between the second cam surface 222 and the fourth cam surface 224. However, the assist cam body 220 may also have the mounting hole 225, which serves as the rotational axis O of the assist cam body 220, formed at a central position between the first cam surface 221 and the third cam surface 223 in a plan view, and at a position offset to one side between the second cam surface 222 and the fourth cam surface 224.

[0088] That is, in the centrifugal clutch 200, the distances from the central axis O of rotation of at least two of the multiple cam surfaces constituting the assist cam body 220 to the assist cam body 220 can be formed to be different from each other. In other words, the centrifugal clutch 200 can be configured so that the central axis O of rotation of the assist cam body 220 passes through a position different from the position of the center of gravity in a cross section of the assist cam body 220 that is perpendicular to the central axis O of rotation. Therefore, in the assist cam body 220, the mounting hole 225 that serves as the central axis O of rotation of the assist cam body 220 can also be formed at a position offset to one side between the first cam surface 221 and the third cam surface 223, and at a position offset to one side between the second cam surface 222 and the fourth cam surface 224 in a plan view.

[0089] On the other hand, the centrifugal clutch 200 can also be configured so that the distances from the rotational center axis O of the assist cam body 220 to each of the multiple cam surfaces constituting the assist cam body 220 are the same. In other words, the centrifugal clutch 200 can be configured so that the rotational center axis O of the assist cam body 220 passes through the center of gravity of the assist cam body 220 in a cross section perpendicular to the rotational center axis O. Specifically, as shown in FIG. 10 , the assist cam body 220 can be provided with mounting holes 225 at positions equidistant from the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224. In this way, the assist cam body 220 can be configured to have four cam surfaces (the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224) having the same cam characteristics.

[0090] In the above embodiment, the assist cam body 220 is formed to have a substantially square shape in a plan view and includes the first to fourth cam surfaces 221 to 224. That is, the assist cam body 220 is formed to have four cam surfaces and is substantially rectangular in a plan view. However, the assist cam body 220 may be formed to have a plurality of cam surfaces (at least two). Therefore, the assist cam body 220 can be formed to have various shapes in a plan view, such as a substantially rectangular shape other than a substantially square, a substantially polygonal shape such as a triangle or pentagon, a substantially elliptical shape, or an irregular shape.

[0091] Specifically, the assist cam body 220 can be formed into a substantially rectangular shape in a plan view, as shown in Figures 11(A) to 11(C). In this case, the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224 can be formed as flat, linear surfaces as shown in Figure 11(A), or some or all of the cam surfaces can be formed as convex (or concave) curved surfaces as shown in Figure 11(B). Furthermore, as shown in Figure 11(C), the assist cam body 220 can have an attachment hole 225, which serves as the center of rotation, formed at an eccentric position in a cross section of the assist cam body 220 (a cross section perpendicular to the central axis of rotation O).

[0092] For example, the assist cam body 220 can be formed in a substantially triangular shape in plan view, as shown in Figures 12(A) to 12(C). In this case, the first cam surface 221, the second cam surface 222, and the third cam surface 223 can be formed as flat, linearly extending surfaces as shown in Figure 12(A), or some or all of the cam surfaces can be formed as convex (or concave) curved surfaces as shown in Figure 12(B). The assist cam body 220 can also be formed as an equilateral triangle, an isosceles triangle, or a right-angled triangle in plan view. Furthermore, the assist cam body 220 can have a mounting hole 225, which serves as the center of rotation, formed at an eccentric position in a cross section of the assist cam body 220 (a cross section perpendicular to the rotation center axis O), as shown in Figure 12(C).

[0093] 13, the assist cam body 220 may be formed into a polygonal shape such as a substantially pentagonal shape in plan view. In this case, the first cam surface 221, the second cam surface 222, the third cam surface 223, the fourth cam surface 224, and the fifth cam surface 226 may be formed into a flat surface extending linearly or a curved surface that is convexly (or concavely) curved. Furthermore, the assist cam body 220 may have a mounting hole 225, which serves as the center of rotation, formed at an eccentric position in a cross section of the assist cam body 220 (a cross section perpendicular to the central axis of rotation O).

[0094] Also, for example, the assist cam body 220 can be formed into an oval shape as shown in Fig. 14(A). In this case, the assist cam body 220 can have a mounting hole 225, which serves as the center of rotation, formed at an eccentric position in the cross section of the assist cam body 220 (a cross section perpendicular to the central axis of rotation O), as shown in Fig. 14(B).

[0095] Furthermore, in the above embodiment, the assist cam body 220 is configured such that the lengths of the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224 in the direction parallel to the rotation center axis O are the same. However, the assist cam body 220 can also be configured such that the lengths of at least two cam surfaces among the multiple cam surfaces, such as the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224, in the direction parallel to the rotation center axis O are different from each other.

[0096] 15, the assist cam body 220 can be formed so that the axial length of the mounting hole 225 in the fourth cam surface 224 is shorter than the lengths of the other cam surfaces. As a result, the centrifugal clutch 200 is formed with different shapes between the two cam surfaces, and the cam surface relative to the weight-side follower 245 is changed, thereby changing the cam characteristics, i.e., the clutch characteristics.

[0097] In the above embodiment, the assist cam body 220 is formed so that the surface roughness of the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224 is all the same. However, the assist cam body 220 may be formed so that the surface roughness of at least two of the multiple cam surfaces, such as the first cam surface 221, the second cam surface 222, the third cam surface 223, and the fourth cam surface 224, is different from one another. As a result, the centrifugal clutch 200 has different surface roughnesses between the two cam surfaces, and therefore, the cam characteristics, i.e., the clutch characteristics, can be changed by changing the cam surface relative to the weight-side follower part 245.

[0098] In the above embodiment, the assist cam body 220 is configured to be rotatably held by the cam body support pin 217 that stands on the drive plate 210. However, it is sufficient that the assist cam body 220 is rotatably supported on the drive plate 210. Therefore, for example, as shown in FIG. 16 , the assist cam body 220 can be configured such that a shaft portion 227 corresponding to the cam body support pin 217 protrudes from the underside of the assist cam body 220, and this shaft portion 227 is rotatably attached to an attachment hole 218 formed in the drive plate 210.

[0099] Furthermore, in the above embodiment, the assist cam body 220 is rotatably supported so as to freely rotate over 360° relative to the drive plate 210. However, the assist cam body 220 may also be rotatably supported so as to swing within a range in which it operates as a cam between the clutch weight 240, i.e., a range of 360° or less. In other words, the rotation of the assist cam body 220 includes forward and reverse rotation on the drive plate 210 over an angle of 360° or more, and forward and reverse rotation within an angle range of less than 360°.

[0100] In the above embodiment, the centrifugal clutch 200 is configured to be driven by the driving force output by the engine, which is an internal combustion engine. However, the centrifugal clutch 200 may also be configured to be driven by the driving force output by a driving source other than the engine, for example, an electric motor.

[0101] In the above embodiment, the centrifugal clutch 200 is configured to receive the rotational driving force output by the engine via the transmission 101. However, the centrifugal clutch 200 can also receive the driving force without passing through the transmission 101. For example, the centrifugal clutch 200 can be configured to receive the driving force directly from the driving source and be driven via an input member (e.g., a mechanical element such as a pulley or gear, such as the driven pulley 130) that rotates the drive plate 210. In other words, the centrifugal clutch 200 can be driven by receiving the driving force directly or indirectly from the driving source.

[0102] O...rotational center axis of assist cam body, 100...power transmission mechanism, 101...transmission, 110...drive pulley, 111...crankshaft, 112...fixed drive plate, 112a...heat dissipation fin, 113...movable drive plate, 114...sleeve bearing, 115...roller weight, 116...ramp plate, 120...V-belt, 130...driven pulley, 131...fixed driven plate, 132...driven sleeve, 133...drive shaft, 134...movable driven plate, 135...torque spring, 200...centrifugal clutch, 210...drive plate, 211...bottom, 211a...through hole, 212...tubular portion, 213...flange portion, 214...swing support pin, 214a...mounting bolt, 214b...E-ring, 215...fulcrum side sliding member, 216...side plate, 217...cam body support pin, 217a...mounting bolt, 218...mounting hole, 220...assist cam body, 221...first cam surface, 222...second cam surface, 223...third cam surface, 224...fourth cam surface, 225...mounting hole, 226...fifth cam surface, 227...shaft portion, 230...damper receiving pin, 231...damper, 240...Clutch weight, 241...Pin slide hole, 242...Connecting spring, 243...Clutch shoe, 244...Assist cam body accommodating portion, 245...Weight side follower portion, 246...Damper groove, 250...Clutch outer, 251...Cylindrical surface.

Claims

1. A centrifugal clutch comprising: a drive plate which is rotated by receiving a driving force from a driving source; a plurality of clutch weights which are displaced so as to contact or separate from the cylindrical surface of the clutch outer by the centrifugal force generated by the rotation of the drive plate; an assist cam body having a cam surface and rotatably mounted on the drive plate; and a weight-side follower part which is mounted on the clutch weight and is pressed by the cam surface of the assist cam body when the clutch weight is displaced, wherein the assist cam body has a plurality of cam surfaces formed thereon, and one of these plurality of cam surfaces presses against the weight-side follower part.

2. A centrifugal clutch as described in claim 1, wherein at least one of the plurality of cam surfaces of the assist cam body is formed as a flat surface, and the weight-side driven part is formed as a flat surface that comes into surface contact with the cam surface formed as a flat surface.

3. A centrifugal clutch as described in claim 1, wherein at least one of the plurality of cam surfaces of the assist cam body is formed of a curved surface, and the weight side driven part is formed of a curved surface that makes surface contact or line contact with the cam surface formed of the curved surface.

4. A centrifugal clutch as described in claim 1, wherein the assist cam body is formed such that the lengths of at least two of the plurality of cam surfaces in a direction parallel to the central axis of rotation of the assist cam body are different from each other.

5. A centrifugal clutch as described in claim 1, wherein the assist cam body is formed such that the distances of at least two of the plurality of cam surfaces from the central axis of rotation of the assist cam body are different from each other.

6. A centrifugal clutch as described in claim 1, wherein the assist cam body is formed in a substantially rectangular shape in a plan view, and the cam surfaces are formed in a number ranging from two to four.

7. A centrifugal clutch as described in claim 1, wherein the assist cam body is formed in a substantially triangular shape in a plan view, and the cam surfaces are formed in a number ranging from two to three.

8. A centrifugal clutch as described in claim 1, wherein the assist cam body has at least two of the plurality of cam surfaces each having a different surface roughness.

9. A method for reproducing or changing clutch characteristics in a centrifugal clutch comprising: a drive plate which is rotated by receiving a driving force from a driving source; a plurality of clutch weights which are displaced so as to come into contact with or separate from the cylindrical surface of the clutch outer by the centrifugal force caused by the rotation of the drive plate; an assist cam body having a cam surface and rotatably mounted on the drive plate; and a weight-side follower part which is mounted on the clutch weight and is pressed by the cam surface of the assist cam body when the clutch weight is displaced, the assist cam body having a plurality of cam surfaces formed thereon, one of which presses the weight-side follower part, the method comprising forming the cam characteristics of at least two of the plurality of cam surfaces constituting the assist cam body so as to be the same or different from each other, and changing the cam surface of the assist cam body so as to press the cam surface having the same or different cam characteristics against the weight-side follower part.

Images