GB1559314A

GB1559314A - Flywheel

Info

Publication number: GB1559314A
Application number: GB36258/76A
Authority: GB
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1975-09-04
Filing date: 1976-09-01
Publication date: 1980-01-16
Also published as: FR2323057B1; FR2323057A1; DE2639784A1; DE2639784C2

Description

(54) FLYWHEEL (71) We, HONDA GIKEN KOGYO KABUSHIKI KAISHA, a Japanese corporation of 27-8, 6 chome, Jingumae Shibuya-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to flywheels and to methods of manufacturing flywheels.

Flywheels to be used in small internal combustion engines have been heretofore obtained generally by casting.

The structure of such a flywheel has been that it has had a flat web portion to be fitted to a driving shaft, such as a crankshaft, and a cylindrical rim portion extending co-axially from the outer periphery of the web portion.

The web portion has been in the form of a deep dish-shaped body provided centrally with a hole so that the body may be fitted to a driving shaft, the flywheel mass being obtained mostly by the rim portion.

In casting such a flywheel, the taper needed for extraction has to be considered in shaping the pattern for the rim portion.

Because of differences between individual moulds, precision in the cast flywheels is hard to obtain. Therefore, mechanical steps such as grinding and finishing the cast cylindrical rim portion are required. Furthermore, to produce flywheels suited to different engines, it is necessary to vary the flywheel mass by varying the rim portion but to achieve this different moulds have to be used.

Thus, there are various problems in obtaining a flywheel by casting and it has also been considered to form a flywheel by shaped ing a steel plate blank instead of by casting.

In this connection it has been considered to form the rim portion, which is an important part of the flywheel mass, for example, from a cylindrical body made from a thick steel plate. However, in the case where increase or decrease in the flywheel mass if desired to be accomplished during production it is necessary to vary the thickness of the plate.

Because steel plates are standardized, this leads to problems. Merely to elongate the rim portion overall to increase mass leads to size and other problems. On the other hand, if the rim portion is formed from thin steel plate, many of the following problems will occur. Because of the thin steel plate, a strain will be produced. If the plate is drawn and moulded, a spring-back in the radial direction is likely to occur. Precision is hard to obtain. If the flywheel mass is to be increased, and this is achieved by elongating the rim portion in the axial direction, not only the problem of size, but also the problem of spring-back and stain, become grea- ter.

If the cylindrical part is formed of two or three portions fitted one within the other this is rather troublesome and complicated, and precision is difficult to obtain.

According to the present invention there is provided a flywheel comprising a dishshaped web portion and a rim portion provided around the periphery of the web portion; the rim portion being formed from a steel plate blank and having continuous undulations with adjacent undulations in close contact with each other and having an inner surface portion which is substantially smooth and continuous in the axial direction of the flywheel. In one form the undulations rise and fall in the radial direction of the flywheel and the smooth and continuous inner surface portion is defined by the innermost boundaries of the undulations whilst in another form the undulations rise and fall in the axial direction of the flywheel and the smooth and continuous inner surface portion is defined by the innermost undulation. The web portion may be formed separately from the rim portion and thereafter integrally joined to the rim portion, or the web portion and the rim portion may be in one piece.

The invention also provides a first method of manufacturing a flywheel that includes the steps of compressing in its axial direction a cylindrical blank formed from steel plate, thereby to form a rim portion of the flywheel having continuous undulations that rise and fall in the radial direction of the blank with adjacent undulations in close contact with each other and defining an inner surface portion of said rim portion which is substantially smooth and continuous in the axial direction and integrally joining the rim portion so formed to the periphery of a dish-shaped web portion.

Further, the invention provides a second method of manufacturing a flywheel including the steps of drawing a steel plate blank integrally to shape in one piece a cylindrical rim portion and a dish-shaped web portion at one end of the cylindrical rim portion, and compressing the cylindrical rim portion in its axial direction to form undulations that rise and fall in the radial direction with adjacent undulations in close contact with each other and defining an inner surface portion which is substantially smooth and continuous in the axial direction.

A further method of manufacturing a flywheel provided by the invention includes the steps of drawing a steel plate blank to form a flanged hat - shaped blank having a cylindrical rim portion, a web portion at one end of this rim portion, and a flange part at the other end of the rim portion and extending in the radial direction of the blank; supporting the web portion and the cylindrical rim portion; compressing the flange part towards the centre of the blank to shape the outer periphery of the cylindrical rim portion of the blank into a rim portion of the flywheel having undulations that rise and fall in the axial direction with adjacent undulations in close contact and with the radially innermost undulation defining an inner surface portion of the rim portion which is substantially smooth and continuous in the axial direction of the flywheel.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which Figure 1 is a sectional side view of a first form of flywheel; Figure 2 is a sectional side view of a second form of flywheel; Figure 3 is å sectional side view of a third form of flywheel- Figures 4A to 4E show, in sequence, steps in manufacturing the flywheel of Figure 1, Figure 4A being a sectional side view of a cylindrical blank, Figure 4B being a sectional side view of the blank after a preparatory working, Figure 4C being a sectional side view of part of the blank ready for being compressed in a shaping machine, Figure 4D showing the blank after it has been compressed and Figure 4E being a sectional side view on a larger scale of a portion of the rim of the finished flywheel; Figures 5A to 5E show, in sequence, steps in manufacturing the second form of flywheel, Figure 5A being a sectional side view of a drawn and shaped blank, Figure 5B being a sectional side view of the blank after a preparatory working, Figure 5C being a view similar to Figure 4C, Figure 5D being a view similar to Figure 4D and Figure 5E being a sectional side view on a larger scale of part of the finished flywheel; and Figures 6A to 6C show, in sequence, steps in manufacturing the third form of flywheel Figure 6A being a sectional side view of å drawn and shaped blank, Figure 6B being a sectional side view of a part of the rim of the blank as being compressed in a shaping machine and Figure 6C being a sectional side view on a larger scale of part of the finished flywheel.

Referring first to Figure 1, as shown in this Figure the flywheel 100 is dish-shaped and consists of a web portion 101 having in the centre thereof a hole 105 for mating with the end of a shaft, such as a crankshaft. The flywheel 100 also has a short cylindrical rim portion 110 having a certain thickness in the radial direction. The web portion 101 and rim portion 110 are formed from steel plate blanks, such as cold-rolled steel plates.

The web portion 101 is pressed and shaped to be of shallow dish-shape with a flat central part 102 having the hole 105 therein and a peripheral side part 103 that slopes towards the outer periphery from the central part 102, this peripheral side part 103 being of frusto-conical form. A flat flange part 104 parallel with the central part 102, is formed on the peripheral outer edge of the peripheral side part 103.

The rim portion 110 is formed by compressing a cylindrical blank in the axial direction so that the blank is folded into a shorter axial length and increased in radial thickness, the rim portion alternately rising and falling, that is undulating, in the radial direction. As illustrated in the drawing, the undulations 110 of the folded rim portion 110 have their respective axial end surfaces in close contact with each other. As a result, the inside and outside surfaces 112 and 113 of the rim portion 110 which are formed by the innermost and outermost boundaries of the undulations, are substantially continuous in the axial direction, and the inside surface 112 can be readily utilized as a base on which one or more permanent magnets may be mounted for forming a flywheel magneto for generating electric current.

The rim portion 110 is joined at one end surface 114 in the axial direction to the surface of the flange part 104 of the web portion 101, the inner and outer peripheries of these joined parts being integrally connected by, for example, welding.

Figure 2 shows a flywheel 100a in which a web portion 101a and rim portion 110a are in one piece formed from a steel plate blank.

In this case the web portion 101a is provided with a hole 105a in the centre thereof, a flat central part 102a, a frusto-conical peripheral side part 103a, and a flat outer peripheral flange part 104a. In this form the rim part 110a undulates in the radial direction as in the first form of Figure 1, the undulations lila extending in the axial direction from a bridging part 115 between the undulations lila and the flange part 104a. In this form also the rim portion 11 0a is formed by being folded in the axial direction, and has the axial end surfaces of its undulations lila in close contact.

Again the inside and outside surfaces 11 2a and 11 3a are substantially continuous and the inside surface 11 2a can be utilized for mounting the permanent magnet(s) of a flywheel mageto.

Turning to Figure 3, the flywheel 200 here shown has a web portion 201 and a rim portion 210 shaped in one piece from a single steel plate blank. The web portion 201 is provided with a hole 205 in the centre, a flat central part 202, and a frusto-conical peripheral side part 203. Undulations 211 forming the rim portion 210 are formed undulating in the axial direction and of a desired axial length. The radial end surfaces of the undulations 211 are in close contact with each other and each undulation has a thickness in the radial direction. A part 215 of the innermost undulation, at the end of this undulation remote from the web, is bent over first to extend in the axial direction and then radially back to become the next undulation. Thus, the flywheel 200 is formed of a single shaped steel plate blank having the rim portion 210 merging into the web portion 201.

As the undulations 211 extend radially they define inside and outside perpherial surfaces 212 and 213 that are parallel with the peripheral surface of the shaft on which the flywheel 200 is to be fitted utilising the hole 205. The inside surface 212 can be directly used as a base for fitting the magnet(s) of a flywheel magneto.

The flywheel in each of the form described may have fitted to it the permanent magnets of a flywheel magneto as already mentioned; cooling fins, which are fitted to the outside surface of the web portion; a balancing mass fitted to the inside surface of the web portion; and a boss member for receiving a crankshaft or the like in the central hole of the web portion.

If it is desired to increase or decrease the flywheel mass this can be done when forming the flywheel by varying the number of undulations formed, and/or by varying the axial extent of the undulations and/or the diameter of the rim portion. The desired flywheel mass is selected to suit the output or other characteristics of the internal combustion engine with which the flywheel is to be used.

Referring to Figures 4A to 4E which show the method of manufacturing the flywheel of Figure 1, Figure 4A shows a cylindrical blank 120. This cylindrical blank 102 is formed from cold-rolled steel plate and has a fixed length in the axial direction.

The cylindrical blank 120 is preparatively worked by being compressed in the axial direction to the configuration shown in Figure 4B so as to form an intermediate blank 120a with small undulations 121 easy subsequently to compress and work Next the intermediate blank 120a is fitted in a annular forming clearance 132 between inner and outer circular dies 130 and 131 (Figure 4C). The blank 120a is supported at one end by an annular die 133, movable in the axial direction in the clearance 132 to a desired fixed position for the blank 120a at which position the die 133 is held stationary.

At the other end the blank is contacted by an annular movable die 134.

The movable die 134 is advanced in the axial direction from the position in Figure 4C so as to compress and buckle the blank 120a in the axial direction, thereby reducing the axial length of the blank 120a, as shown in Figure 4D to obtain the rim portion 110 of the formation already described. The rim portion produced is shown in Figure 4E.

When the blank 120a is thus formed into the rim portion 110 in the shaping machine of Figure 4C, its formation is regulated by the opposed wall surfaces 130a and 131a of the clearance 132 between the dies 130 and 131, the blank sliding while being squeezed. The effect of the wall surfaces 130a and 131a is that the inner and outer axial surfaces 112 and 113 are flat with substantially no discontinuity between undulations as shown in Figure 4E, the finished rim portion having uniform inside and outside diameters D1 and D 2. over the entire inner and outer peripheries, of fixed dimensions to very high precision. No further mechanical working of the inside and outside surfaces is required.

The so-formed rim portion 110 is integrally joined to the web portion 101 by means, such as welding, to obtain a flywheel such as shown in Figure 1.

Turning to Figures 5A to 5E which show the order of steps of a method of manufacturing the flywheel shown in Figure 2 which is formed in one piece first a steel plate, such as a cold-rolled steel plate, is drawn to obtain a cylindrical vessel-shaped blank 140 (Figure 4A). This blank 140 is provided with a deep-drawn cylindrical part 141 and a dishshaped web portion 142 at one end of the cylindrical part 141. A hole 144 is formed in the centre of the base plate 142.

The cylindrical part 141 of the blank 140 is first compressed in the axial direction to obtain an intermediate blank 140a having corrugations 143.

The intermediate blank 140a is set in a pressing and shaping machine as shown in Figure 5C, and is then compressed.

The pressing and shaping machine is provided with one die 150 resiliently acted upon by a spring 155, and a further die 151 provided concentrically on the outer periphery of the die 150 with an annular clearance 152 between the outer peripheral surface 1 50a of the die 150 and the inner peripheral surface 15 lea of the die 151. A fixed die 153 provided within the die 151 receives the intermediate blank 140a so that the web portion 142 of the blank 140a is supported between the opposed surfaces of the dies 150 and 153.

The part 141 having the corrugations 143 is supported within the clearance 152 between the end surface of the peripheral side part of the die 153 and the movable die 154 which is advanced to compress the part 141 in the axial direction. Thus there is formed the rim portion 11 0a reduced in axial length and with undulations as shown in Figure 5D, the one piece flywheel produced being shown in Figure 5E. From this Figure it will be seen that the rim portion 110a of the one piece flywheel 100a has inside and outside diameters Dl and D2. As in the case of the method of Figures 4A to 4E, these diameters are formed with very high precision, and the inner and outer axial surfaces of the rim portion are formed as smooth surfaces without any further mechanical work being required.

The flywheel of Figure 3 is made by the method illustrated in Figures 6A to 6C.

A steel plate blank, such as a cold-rolled steel plate, is drawn and shaped to obtain a flanged hat-shaped blank 220 as shown in Figure 6A. This blank 220 consists of a dishshaped web portion 221 having a hole 225 formed in the centre, and a cylindrical part 222 extending axially from the outer periphery of the web portion 221. A flange part 223 that is to form the web portion 210 of the flywheel extends radially from the end of the part 222 remote from the portion 221.

In a preparatory working the flange plate 223 of this blank 220 is pressed, on its outer peripheral end, towards the centre to form undulations 224 rising and falling in the axial direction. Figure 6A shows the blank 220 as preparatively worked.

The preparatively worked blank 220 is fitted, as shown in Figure 6B, by its cylindrical part 222 on the outer periphery 230b of a part 23 0a of a die 230 that can be rotated by a drive shaft 233, the web portion 210 also being supported by the part 230a. A square shaft 234 projecting axially from the part 230a is fitted in the hole 225 and is engaged in a square hole 235 formed in a part 231a, of a die 231, that has a surface complementary to the corresponding surfaces of the part 230a. The blank is thus supported between the complementary surfaces of the parts 230a, 231a. Rotation of the die 230 is transmitted to the die 231 by the engagement of the hole 235 with the shaft 235 so that both dies rotate together. The die 231 is always resiliently pressed towards the die 230 by a spring 236.

The dies 230 and 231 have respective flange parts 230c and 231c in the radial direction. A clearance 232 in the axial direction is provided between the opposed end surfaces of the flange parts 230c and 231c, equal to the axial length of the cylindrical part 222 of the blank. The flange part 223 of the blank 220 is positioned in this clearance 232.

The blank 220 is supported by the dies 230 and 231, and then the die 230 is rotated by the shaft 233 so that the blank 220 supported between the dies 230 and 231 is also rotated.

A rotary pressing member 238, constituting a movable die and rotatably supported by a shaft 237, is moved into the clearance 232 between the respective flange parts 230c and 231c of the dies 230 and 231. This rotary pressing member 238 is gradually moved towards the centre of the dies 230, 231 to press the flange part 223 of the blank 220 towards the centre so that tile pitch of the undulations 224 is gradually made smaller, and finally the flange part 223 is fully compressed so that the undulations are in contact with one another and E ith the outer periphery 212 of the cylindrical part 22 which now becomes, in effec;, an innermost undulation.

By effecting this rotating ,)resting operation, the desired shaping can lze effected with a small pressing force and wfth little frictional resistance.

In the method just described, the undulations formed, that is the deformations in the axial direction of the flange part, are regulated by the flange parts 230c and 231c of the dies 230 and 231, and therefore the axial length of the part shaped by compressing is determined by the dimension of the clearance 232. The rim portion 210, including the cylindrical part 222 that was the- outer periphery of the web portion 201, has its undulations, which include the part 222, parallel with one another and this rim portion is in one piece with the web portion. In the shaping operation, the part of the blank having the surface 212 is compressed and shaped on the outer periphery of the receiving part 230a of the die 230. The part of the blank having the surface 213 in the finished flywheel (Figure 3) is compressed and shaped while rotating the blank. Therefore, the inside and outside surfaces 212 and 213 are very smooth in the axial direction and the inside and outside diameters D1 and D2 are formed high in precision, as shown in Figure 6C. No additional mechanical operations are required for forming the inside and outside surfaces 212,213, and the axial length of the rim portion 210 is maintained accurately in a determined dimensional precision. A onepiece flywheel as shown in Figure 3 is thereby obtained.

In all the methods described a flywheel is obtained by pressing and shaping, not by casting. Particularly, because the flywheel rim portion is formed by compressing and shaping a steel plate blank, a flywheel having a sufficient mass around the periphery of the web portion can be simply and easily obtained with small overall dimensions and a large mass.

WHAT WE CLAIM IS: 1. A flywheel comprising a dish-shaped web portion and a rim portion provided around the periphery of the web portion; the rim portion being formed from a steel plate blank and having continuous undulations with adjacent undulations in close contact with each other, and having an inner surface portion which is substantially smooth and continuous in the axial direction of the flywheel.

2. A flywheel as claimed in claim 1, wherein said undulations rise and fall in the radial direction of the flywheel and said inner surface portion is defined by the innermost boundaries of said undulations.

3. A flywheel as claimed in claim 1, wherein said undulations rise and fall in the axial direction of the flywheel and said inner surface portion is defined by the innermost undulation.

4. A flywheel as claimed in claim 1, 2 or 3, wherein the web portion is formed separately from the rim portion and thereafter is integrally joined to the rim portion.

5. A flywheel as claimed in claim 1, 2 or 3, wherein the rim portion and the web portion are in one piece.

6. A flywheel substantially hereinbefore described with reference to any one Figures 1 to 3 of the accompanying drawings.

7. A method of manufacturing a flywheel including the steps of compressing in its axial direction a cylindrical blank formed from steel plate, thereby to form a rim portion of the flywheel having continuous undulations that rise and fall in the radial direction of the blank with adjacent undulations in close contact with each other and defining an inner surface portion of said rim portion which is substantially smooth and continuous in the axial direction, and integrally joining the rim portion so formed to the periphery of a dish-shaped web portion.

8. A method of manufacturing a flywheel including the steps of drawing a steel plate blank integrally to shape in one piece a cylindrical rim portion and a dish-shaped web portion at one end of the cylindrical rim portion, and compressing the cylindrical portion in its axial direction to form undulations that rise and fall in the radial direction with adjacent undulations in close contact with each other and defining an inner surface portion which is substantially smooth and continuous in the axial direction.

9. A method of manufacturing a flywheel including the steps of drawing a steel plate blank to form a flanged hat-shaped blank having a cylindrical rim portion, a web portion at one end of this rim portion, and a flange part at the other end of the rim portion and extending in the radial direction of the blank; supporting the web portion and the cylindrical rim portion; and compressing the flange part towards the centre of the blank to shape the outer periphery of the cylindrical rim portion of the blank into a rim portion of the flywheel having undulations that rise and fall in the axial direction with adjacent undulations in close contact and with the radially innermost undulation defining an inner surface portion of the rim portion which is substantially smooth and continuous in the axial direction of the flywheel.

10. A method of manufacturing a flywheel substantially hereinbefore described with reference to Figures 4A to 4E, to Figures 5A to 5E, or to Figures 6A to 6C of the accompanying drawings.

11. A flywheel manufactured in accordance with a method as defined by any one of

Claims

claims 7 to 10.