GB2440153A

GB2440153A - I.c. engine valve guide

Info

Publication number: GB2440153A
Application number: GB0614367A
Authority: GB
Inventors: M Senior Andrew; Alan Frendt
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2006-07-20
Filing date: 2006-07-20
Publication date: 2008-01-23
Anticipated expiration: 2026-07-20
Also published as: GB0614367D0; GB2440153B

Abstract

A valve guide 10 for a valve of an internal combustion engine has an elongated body member 11 having a bore 14 extended longitudinally therethrough for receiving a valve stem. The bore 14 is provided with at least one, eg four, straight grooves 15 extending over a major portion of the length of the body member 15 leaving an end portion 17 with a continuous uninterrupted surface. The number and width of the grooves may be such that the surface area contact between the valve stem and the valve guide 10 is reduced by 25% to 75%. The grooves in the valve guide 10 enable viscous friction resistance of oil along the valve stem to be reduced when the oil is not at its working temperature.

Description

Valve ciuide The present invention relates to a guide for a valve in

internal combustion engines.

In a known-manner, the valve has a head and a stem extending from the head which is slidable within the valve guide under conditions of marginal lubrication. The lubrication of the valve stem is generally accomplished by supplying oil at the free end of the stem so that a thin layer of oil is provided between the stem and the guide. Oils normally used for these types of applications have a low viscosity at their working temperature so that the drive force to open or close the valve is relatively low. If, however, the temperature of the oil is very low, for instance considerably below 00 C, as may be the case, for example, after the motor vehicle has been shut down overnight in the winter, there is a drastic increase in the viscosity of the oil resulting in the need for a higher drive force, in particular where electromagnetic valve operation is used, to pull or push the valve. As a result, the closing or opening of the valve can be slowed down or the valve can be stuck in an intermediate position.

It is an object of the present invention, therefore, to provide an improved valve guide for reducing viscous friction resistance of oil along the valve stem, to reduce the force required to operate the valve at low temperatures thus preventing slow closing or opening of the valve.

According to the invention there is provided a valve guide for a valve of an internal combustion engine, the valve having a valve stem and valve head and the valve guide comprising an elongated body member having a bore extended longitudinally therethrough for receiving the valve stem, wherein the bore is provided with at least one straight groove extending over a major portion of the length of the body member leaving an end portion of the bore with a continuous uninterrupted surface.

Preferably, the number of grooves and the width of each groove are determined in such a way that the surface area contact between the valve stem and the valve guide is comprised at ratio between 25 and 75%.

Preferably, the length of the end portion is greater than the diameter of the bore of the body member. The length of the end portion is a ratio of the diameter of the bore, preferably a range between 1 and 3.

The invention will now be described by way of example with reference to the accompanying drawings of which: -Fig.1 is a perspective view of a valve guide in accordance with the invention, Fig.2 is a cross section along the line Il-Il of the Fig.1, and Fig.3 is a view in to the direction of arrow A in Fig.1.

With reference to Figs 1 to 3, there is shown a guide 10 for a stem of a valve (not shown). The valve guide 10 is, in use, frictionally received in a press fit engagement within a bore formed in a cylinder head of an internal combustion engine.

The valve guide 10 has an elongated cylindrical body member 11 which, when installed, has one 12 of its ends adjacent the valve head and the opposite end 13 adjacent the free end of the stem. Extended longitudinally of the body member 11 is a bore 14 of a diameter only slightly larger than the diameter of the valve stem. The bore 14 is provided with several straight grooves 15, in this example four axially extending grooves circumferentially distributed around a longitudinal axis XX of the body member. Each groove 15 extends over a major portion of the length L of the body member 11 from the end 13 of the bore 14 adjacent, in use, to the free end of the stem. The number of grooves and the width of each groove are determined in such a way that the surface area contact between the valve and the valve guide is reduced at a ratio between 25 and 75 %.

Each groove 15 terminates at an end wall 16 which is spaced apart from the end 12 of the bore 14 adjacent the valve head defining hence an end portion 17 of the bore 14 which is provided with a continuous uninterrupted surface.

The length I of the end portion 17 is preferably greater than the diameter of the bore 14 of the body member, so as to provide an oil control ring for the supply of oil to and from the guide 10. The length I of the end portion 17 is a ratio of the diameter of the bore, preferably a range between 1:1 and 3:1.

Such an arrangement of grooves 15 on a valve guide 10 enables a reduction in the viscous drag of the valve in the valve guide. Furthermore such a valve guide improves displacement of the valve stem at low temperature without the need to increase the valve actuation force. This is particularly important where electromagnetic or electro-hydraulic valve operation is used Although the invention has been described by way of example with reference to a specific embodiment of the invention various modifications may be made without departing from the invention. For example, the number size and length of grooves arranged on the bore could vary. Alternatively, the end portion 17 could be adjacent to the free end of the stem depending on the type of engine.

Claims

CLAIMS

1. A valve guide for a valve of an internal combustion engine, the valve having a valve stem and valve head and the valve guide comprising an elongated body member having a bore extended longitudinally therethrough for receiving the valve stem, wherein the bore is provided with at least one straight groove extending over a major portion of the length of the body member leaving an end portion of the bore with a continuous uninterrupted surface.

2. A valve guide as claimed in claim 1 wherein the number of grooves and the width of each groove are determined in such a way that the surface area contact between the valve stem and the valve guide is comprised at ratio between 25 and 75%.

3. A valve guide as claimed in claim 1 or claim 2 in which the end portion is, when the valve guide is installed, adjacent to the valve head.

4. A valve guide as claimed in claim 1 or claim 2 in which the end portion is, when the valve guide is installed, adjacent to the tree end of the valve stem.

5. A valve guide as claimed in any one of claims 1 to 4 in which the length of the end portion is greater than the diameter of the bore of the body member.

6. A valve guide as claimed in any one of claims 1 to 5 in which the length of the end portion is a ratio of the valve diameter, preferably a range between 1:1 and 3:1 - 7. A valve guide as claimed in any one of claims 1 to 6 in which the bore is provided with four grooves circumferentially distributed around a longitudinal axis of the body member.

8. A valve guide substantially as described herein with reference to Figs. 1 to 3 of the accompanying drawings.