Claims
- 1. An outer guide means for a valve tappet receiving an automatic, hydraulic clearance compensation element for use in internal combustion engines, the tappet being disposed directly between a cam of a camshaft and a valve stem, the guide means comprising a wear-resistant, metallic end member co-operating with the cam, a hollow cylindrical stem part made of an extrudable polymeric substance and closed at one end by the end member and sliding in a guide bore in a cylinder head, and means coaxially disposed in the stem part thereof and adapted to receive the clearance compensation element, characterized in that a thin-walled unitary reinforcing element is provided which is drawn from sheet metal and which, on the one hand, is secured to the end member and, on the other hand, is positively connected to the stempart by being embedded in the polymeric substance, and that the hydraulic clearance compensation element with its end remote from the valve stem directly bears against the end member.
- 2. The guide means of claim 1 wherein the positive connection of the reinforcing element to the stem part is provided by extrusion sheathing.
- 3. A guide means of claim 1 wherein the reinforcing element has a tubular portion connected by its outer generated surface to the stem part and by one of its ends to the end member.
- 4. A guide means of claim 1 wherein the reinforcing element has provision for centering the end member.
- 5. A guide means of claim 4 wherein the centering provision is in the form of a tubular terminal section of the reinforcing element and the end member is disposed in the bore of the terminal section.
- 6. A guide means of claim 1 wherein the reinforcing element has a bearing surface for the side of the end member which is remote from the cam.
- 7. A guide means of claim 6 wherein the bearing surface is a radially extending annular flange connecting the tubular portion to the terminal section, the outer diameter thereof being greater than that of the tubular portion by an amount to be equal to or less than the outer diameter of the stem part.
- 8. A guide means of claim 6 wherein the bearing surface is a circumferential inwardly directed fold at the transition between the tubular portion and the terminal section.
- 9. A guide means of claim 1 wherein the end member is connected to the reinforcing element by a homogenous joint.
- 10. A guide means of claim 1 wherein the end member is secured positively to the reinforcing element and sealing means are provided between the end member and the reinforcing element.
- 11. A guide means of claim 1 wherein the means receiving the clearance compensation element is integral with the reinforcing element.
- 12. A guide means of claim 3 wherein the means take the form of an inwardly directed flange formed on that end of the tubular portion distal from the end member, the flange merging in its bore into a hollow cylindrical element.
- 13. A guide means of claim 12 wherein the flange is conical, its taper and the hollow cylindrical element extending towards the end member.
- 14. A guide means of claim 1 wherein the portion of the reinforcing element connecting it to the stem part, is formed so that the reinforcing element is secured against rotation and axial displacement relative to the stem part.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 3409235 |
Mar 1984 |
DEX |
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PRIOR APPLICATION
This application is a continuation of copending U.S. patent application Ser. No. 703,881 filed Feb. 21, 1985, now abandoned.
Outer guide means for a valve tappet receiving an automatic, more particularly hydraulic, clearance compensation element of use in internal combustion engines, the tappet being disposed directly between a cam of a camshaft and a valve stem, the guide means comprising a wear-resistant end member cooperating with the cam, a hollow cylindrical stem part made of an extrudable polymeric substance and closed at one end by the end member and sliding in a guide bore in a cylinder head; and a means disposed coaxially in the stem part thereof and adapted to receive the clearance compensation element and made of light metal is disclosed in EP-OS No. 00 30 780. To ensure that the wearing and sliding properties of the guide means in the cylinder head guide bore meet practical requirements, the outer generated surface referred to is in the known guide means provided with a wear-resistant layer.
A layer of this kind, which requires extra labor and costs for its provision, can be obviated if the guide means is made of a polymeric substance since such substances nearly always have satisfactory wearing and sliding properties when used in co-operation with metal substance. However, it is not readily possible for the known guide means to be made of a polymeric substance instead of from a light metal. The first difficulty is that, unlike the known guide means, the end member cannot be secured to the stem part with adequate reliability by beading. The second difficulty is that in the known guide means all the force necessary to actuate the valve passes through a base-like part of the stem part, the base-like part being engaged by the clearance compensation element, but reasons of strength preclude the use of this system with a polymeric substance.
It is an object of the invention to provide a polymeric guide means of the kind referred to wherein the end member is secured reliably to the stem part and there is no overstressing of the polymeric substance.
This and other objects and advantages of the invention will become obvious from the following detailed description.
The outer guide means of the invention for a valve tappet receiving an automatic, hydraulic clearance compensation element of use in internal combustion engines, the tappet being disposed directly between a cam of a camshaft and a valve stem, the guide means comprising a wear-resistant end member co-operating with the cam, a hollow cylindrical stem part made of an extrudable polymeric substance and closed at one end by the end member and sliding in a guide bore in a cylinder head, and means coaxially disposed in the stem part thereof and adapted to receive the clearance compensation element is characterized in that a thin-walled unitary reinforcing element (10, 22, 41) is provided which is drawn from sheet metal and which, on one hand, is secured to the end member (8, 26, 42) and, on the other hand, is positively connected to the stem part (9, 32, 36). The thin-walled unitary reinforcing element is preferably positively connected by extrusion sheathing to the stem part.
This features provides the foundation for reliable securing of the end member to the stem part and, because of the construction of the invention of the outer guide means, the clearance compensation element can directly engage with that side of the end member which is distal from the cam. In a variation of the invention, the reinforcing element has a tubular portion connected by its outer generated surface to the stem part and by one of its ends to the end member.
As an aid in assembly of the guide means and to reduce the load on the connection between the end member and the reinforcing element caused by forces operative transversely of the tappet longitudinal axis between the end member and the cam as a result of friction, the reinforcing element has provision for centering the end member. In this event, according to another feature of the invention, the centering provision takes the form of a tubular terminal section of the reinforcing element and the end member is disposed in the bore of the terminal section.
According to the invention, the reinforcing element has a bearing surface for that side of the end member which is remote from the cam to reduce the action on the connection between the end member and the reinforcing element of forces which in operation act lengthwise of the tappet. In this event, this bearing surface can be a radially extending annular flange which connects the tubular portion to the terminal section, the outer diameter thereof being greater than that of the tubular portion by an amount to be equal to or less than the outer diameter of the stem part, or the bearing surface can be an inwardly directed fold at the transition between the tubular portion and the terminal section.
According to other features of the invention, the end member is connected to the reinforcing element by a homogenous joint, more particularly by soldering or welding, or the end member is secured positively to the reinforcing element and sealing means are provided between the end member and the reinforcing element.
In a variation of the invention, as a very simple yet strong way of securing the clearance compensation element in the guide means, the means receiving the clearance compensation element is formed on the reinforcing element.
According to other features of the invention, the means for receiving the clearance compensation element take the form of an inwardly directed flange formed on that end of the tubular portion which is distal from the end member, the flange merging in its bore into a hollow cylindrical element or the flange is conical, its taper and the hollow cylindrical extending towards the end member.
In a final feature of the invention, the portion of the reinforcing element by which it is connected to the stem part is formed so that the reinforcing element is secured against rotation and axial displacement relative to the stem part.
US Referenced Citations (3)
| Number |
Name |
Date |
Kind |
|
3658038 |
Bergmann |
Apr 1972 |
|
|
4367701 |
Buente |
Jan 1983 |
|
|
4430970 |
Holtzberg et al. |
Feb 1984 |
|
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 2070181 |
Sep 1981 |
GBX |
Continuations (1)
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Number |
Date |
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| Parent |
703881 |
Feb 1985 |
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Patent Grant
4924825
