GB2116286A

GB2116286A - Toothed transmission pulley

Info

Publication number: GB2116286A
Application number: GB08301632A
Authority: GB
Inventors: Yasuo Ohhashi
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1982-01-23
Filing date: 1983-01-21
Publication date: 1983-09-21
Also published as: GB8301632D0; JPS58128561A

Abstract

A toothed transmission pulley comprising a surface ring R formed of metal strip shaped to define the requisite teeth 1 and recesses 3 therebetween, and a rigid inner body P moulded from plastics material whose outer surface conforms to the inner surface of said metal ring. <IMAGE>

Description

SPECIFICATION Toothed transmission pulley This invention relates to a toothed transmission pulley, for use for example in timing power transmission mechanisms for driving the cam shaft of a four-cycle internal combustion engine.

In the past, such transmission pulleys were made by casting or sinter molding. In more recent years a variety of techniques have been proposed to form them by plastic working of metal plate, such as steel plate, in order to reduce weight and manufacturing costs. However, the latter proposals have scarcely been put to practical use, because of the restrictions which they place on the pulley shape, insufficient dimensional accuracy particularly of the toothed surface, and manufacturing problems.

According to the present invention there is provided a toothed transmission pulley comprising a surface ring formed of metal strip shaped to define the requisite teeth and recesses therebetween, and a rigid inner body moulded from plastics material whose outer surface conforms to the inner surface of said metal ring.

In a preferred form of the invention the said body is made of fiber reinforced plastics and the said ring of steel plate.

In one form of the invention the said body is moulded in the said ring so as to conform exactly to the inside configuration of the latter.

Alternatively the two parts may be formed separately and then secured together, preferably by adhesive.

An embodiment of the invention, together with a modification thereof, will now be described by way of example and with reference to the accompanying drawings, in which: Figure lisa perspective view of a toothed transmission pulley according to the invention; Figure 2 shows the pulley in front elevation; Figure 3 is a cross-section on the line Ill-Ill of Figure 2; Figure 4 is a cross-sectional view of part of the pulley; and Figure 5 is a view similar to Figure 4 but showing a modification.

Referring to the drawings a toothed transmission pulley according to the invention comprises a toothed ring R and a pulley body P whose outer surface conforms to the inside surface of the toothed ring R. The ring R is formed from a strip of wear-resisting tough metal plate, such as steel plate, to have a series of projecting teeth on its outside surface, equally spaced in the longitudinal direction, and formed at their tips with radii 2. Recesses 3 between adjacent teeth 1 are of U-shaped cross section, and in use the teeth of a transmission belt engage in said spaces 3. The metal strip having been so formed it is rounded to an annular configuration and its free ends are butt welded to form the toothed ring R.

The pulley body P is a one-piece moulding of rigid, fiber reinforced plastics material, reinforced with glass fibers for example, and comprises a boss portion 4, a web portion 5, and a surface portion provided by a flange 6. A shaft bore 7 is formed on said boss portion, and the outside peripheral surface 6a of said flange 6 is shaped to conform to the inside surface of the toothed ring R.

To secure the pulley body P inside the toothed ring R any convenient joining methods may be employed. For example the ring R may be inserted in the mould in which the pulley body P is cast. In other words a toothed ring formed in the manner described above is secured in the inside wall of a mould, such as a metal mould, and the pulley body is cast in the mould so that the toothed ring R is joined integrally to the pulley body P.

Alternatively, such parts may be secured together by inserting the previously formed pulley body P into the toothed ring R and bonding them with an adhesive.

In use of a transmission pulley thus constructed, a shaft may be inserted into the shaft bore 7 of the boss portion 4, and a timing belt wrapped around the toothed transmission pulley by engaging the belt teeth on its inside surface in the recesses of the ring R, so that rotation of the shaft is transmitted to the timing belt, or movement of the timing belt is transmitted to the shaft.

In the modification shown in Figure 5, at the bottoms of the recesses 3 of the toothed ring R are provided small holes 8 which receive pips on the pulley body P for secure interconnection. The ring R and the pulley body P may be joined together by insert casting during the casting of the pulley body P as described above, or by other joining methods as in the case of the first embodiment.

it will thus be seen that in preferred embodiments of the invention the major portion of the toothed transmission pulley is made of lightweight rigid synthetic plastics so that the pulley weight may be greatly reduced as compared with an ail-metal pulley, and the teeth, which are subjected to high transmission torque in use, are formed from a wear-resisting tough metal plate so that wear and deformation may be reduced and high dimensional accuracy obtained.

Further, as the outside peripheral surface of the pulley body conforms to the inside surface of the toothed ring, the joining strength between them is increased, and there is no danger of relative slipping in the direction of rotation between the pulley body P and the toothed ring R. In addition, since the pulley body P which constitutes the major portion of toothed transmission pulley is a plastics moulding, there is almost no restriction on its configuration, so that toothed transmission pulleys of almost any desired shape can be formed. Thus, lightweight toothed transmission pulleys of desired shape having high overall dimensional accuracy may be cheaply produced according to the invention.

1. A toothed transmission pulley comprising a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Toothed transmission pulley This invention relates to a toothed transmission pulley, for use for example in timing power transmission mechanisms for driving the cam shaft of a four-cycle internal combustion engine. In the past, such transmission pulleys were made by casting or sinter molding. In more recent years a variety of techniques have been proposed to form them by plastic working of metal plate, such as steel plate, in order to reduce weight and manufacturing costs. However, the latter proposals have scarcely been put to practical use, because of the restrictions which they place on the pulley shape, insufficient dimensional accuracy particularly of the toothed surface, and manufacturing problems. According to the present invention there is provided a toothed transmission pulley comprising a surface ring formed of metal strip shaped to define the requisite teeth and recesses therebetween, and a rigid inner body moulded from plastics material whose outer surface conforms to the inner surface of said metal ring. In a preferred form of the invention the said body is made of fiber reinforced plastics and the said ring of steel plate. In one form of the invention the said body is moulded in the said ring so as to conform exactly to the inside configuration of the latter. Alternatively the two parts may be formed separately and then secured together, preferably by adhesive. An embodiment of the invention, together with a modification thereof, will now be described by way of example and with reference to the accompanying drawings, in which: Figure lisa perspective view of a toothed transmission pulley according to the invention; Figure 2 shows the pulley in front elevation; Figure 3 is a cross-section on the line Ill-Ill of Figure 2; Figure 4 is a cross-sectional view of part of the pulley; and Figure 5 is a view similar to Figure 4 but showing a modification. Referring to the drawings a toothed transmission pulley according to the invention comprises a toothed ring R and a pulley body P whose outer surface conforms to the inside surface of the toothed ring R. The ring R is formed from a strip of wear-resisting tough metal plate, such as steel plate, to have a series of projecting teeth on its outside surface, equally spaced in the longitudinal direction, and formed at their tips with radii 2. Recesses 3 between adjacent teeth 1 are of U-shaped cross section, and in use the teeth of a transmission belt engage in said spaces 3. The metal strip having been so formed it is rounded to an annular configuration and its free ends are butt welded to form the toothed ring R. The pulley body P is a one-piece moulding of rigid, fiber reinforced plastics material, reinforced with glass fibers for example, and comprises a boss portion 4, a web portion 5, and a surface portion provided by a flange 6. A shaft bore 7 is formed on said boss portion, and the outside peripheral surface 6a of said flange 6 is shaped to conform to the inside surface of the toothed ring R. To secure the pulley body P inside the toothed ring R any convenient joining methods may be employed. For example the ring R may be inserted in the mould in which the pulley body P is cast. In other words a toothed ring formed in the manner described above is secured in the inside wall of a mould, such as a metal mould, and the pulley body is cast in the mould so that the toothed ring R is joined integrally to the pulley body P. Alternatively, such parts may be secured together by inserting the previously formed pulley body P into the toothed ring R and bonding them with an adhesive. In use of a transmission pulley thus constructed, a shaft may be inserted into the shaft bore 7 of the boss portion 4, and a timing belt wrapped around the toothed transmission pulley by engaging the belt teeth on its inside surface in the recesses of the ring R, so that rotation of the shaft is transmitted to the timing belt, or movement of the timing belt is transmitted to the shaft. In the modification shown in Figure 5, at the bottoms of the recesses 3 of the toothed ring R are provided small holes 8 which receive pips on the pulley body P for secure interconnection. The ring R and the pulley body P may be joined together by insert casting during the casting of the pulley body P as described above, or by other joining methods as in the case of the first embodiment. it will thus be seen that in preferred embodiments of the invention the major portion of the toothed transmission pulley is made of lightweight rigid synthetic plastics so that the pulley weight may be greatly reduced as compared with an ail-metal pulley, and the teeth, which are subjected to high transmission torque in use, are formed from a wear-resisting tough metal plate so that wear and deformation may be reduced and high dimensional accuracy obtained. Further, as the outside peripheral surface of the pulley body conforms to the inside surface of the toothed ring, the joining strength between them is increased, and there is no danger of relative slipping in the direction of rotation between the pulley body P and the toothed ring R. In addition, since the pulley body P which constitutes the major portion of toothed transmission pulley is a plastics moulding, there is almost no restriction on its configuration, so that toothed transmission pulleys of almost any desired shape can be formed. Thus, lightweight toothed transmission pulleys of desired shape having high overall dimensional accuracy may be cheaply produced according to the invention. CLAIMS

1. A toothed transmission pulley comprising a surface ring formed of metal strip shaped to define the requisite teeth and recesses therebetween, and a rigid inner body moulded from plastics material whose outer surface conforms to the inner surface of said metal ring.

2. A pulley as claimed in claim 1, wherein said plastics material is fiber reinforced.

3. A pulley as claimed in claim 1 or 2, wherein said metal ring is made of steel plate.

4. A pulley as claimed in any of the preceding claims, wherein said body is moulded in said ring.

5. A pulley as claimed in any of claims 1 to 3, wherein said body and said ring are secured together by adhesive.

6. A pulley as claimed in claim 4, wherein integral pips on the body extend into holes in said ring formed in at least some of the recesses between the teeth.

7. Toothed transmission pulleys substantia!ly as hereinbefore described with reference to the accompanying drawings.