Inlet Valve Arrangement and Method for External-Heat Engine

Abstract

An inlet-valve arrangement is for an external-heat engine, which includes at least one working chamber, each one having a cooperating piston. The working chamber is supplied with a working fluid via at least one controlled poppet valve. The poppet valve is arranged to open in the opposite direction to the flow direction of the working fluid. The center axis of the poppet valve is arranged perpendicularly within a deviation of 45 degrees relative to the center axis of the piston.

Claims

1. An inlet-valve arrangement (1) for an external-heat engine (5), which includes at least one working chamber (33), each one having a cooperating piston (4) and the working chamber (33) being supplied with a working fluid via at least one controlled poppet valve (6, 40), the poppet valve (6, 40) being arranged to open in the opposite direction to the flow direction of the working fluid, characterized in that the centre axis (20) of the poppet valve (6, 40) is arranged perpendicularly within a deviation of 45 degrees relative to the centre axis (34) of the piston (4).

2. The inlet-valve arrangement (1) according to claim 1, characterized in that the centre axis (20) of the poppet valve (6, 40) is arranged perpendicularly within a deviation of 20 degrees relative to the centre axis (34) of the piston (34).

3. The inlet-valve arrangement (1) according to claim 1, characterized in that the centre axis (20) of the poppet valve (6, 40) is arranged perpendicularly within a deviation of 10 degrees relative to the centre axis (34) of the piston (34).

4. The inlet-valve arrangement (1) according to claim 1, characterized in that each working chamber (33) is supplied with pressurized fluid via at least two poppet valves (6, 40).

5. The inlet-valve arrangement (1) according to claim 4, characterized in that at least two of the poppet valves (6, 40) are of different sizes.

6. The inlet-valve arrangement (1) according to claim 5, characterized in that a smaller second poppet valve (40) is arranged to open before a larger first poppet valve (6).

7. The inlet-valve arrangement (1) according to claim 1, characterized in that the piston (4) is formed with a piston head (38) which projects at least partly into a dead volume (32) between the poppet valve (6, 40) and the piston (4) when the piston (4) is in its position nearest to the cylinder head (2).

8. The inlet valve arrangement (1) according to claim 1, characterized in that the valve guide (14) of the poppet valve (6, 40) is designed to reduce the volume of the inlet channel (30).

9. A method for an inlet-valve arrangement (1) for an external-heat engine (5) including at least one working chamber (33), each one having a cooperating piston (4) and the working chamber (33) being supplied with a working fluid via at least one controlled poppet valve (6, 40), the poppet valve (6, 40) being arranged to open in the opposite direction to the flow direction of the working fluid, characterized in that the method includes arranging the centre axis of the poppet valve (6, 40) perpendicularly within a deviation of 45 degrees relative to the centre axis (34) of the piston (4).

10. The method according to claim 9, characterized in that the method includes arranging the centre axis (20) of the poppet valve (6, 40) perpendicularly within a deviation of 20 degrees relative to the centre axis (34) of the piston (4).

11. The method according to claim 9, characterized in that the method includes arranging the centre axis (20) of the poppet valve (6, 40) perpendicularly within a deviation of 10 degrees relative to the centre axis (34) of the piston (4).

12. The method according to claim 9, characterized in that the method includes opening a second poppet valve (40) before a first poppet valve (6) when the external-heat engine (5) is operating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In what follows, an example of a preferred embodiment and method is described, which is visualized in the accompanying drawings, in which:

[0027] FIG. 1 shows a section of a piston and part of a cylinder head with an inlet-valve arrangement according to the invention;

[0028] FIG. 2 shows the piston and part of the cylinder head in section in another embodiment;

[0029] FIG. 3 shows a section II-II of FIG. 2; and

[0030] FIG. 4 shows a section IV-IV of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

[0031] In the drawings, the reference numeral 1 indicates an inlet-valve arrangement located in a cylinder head 2. A piston 4 is shown, but not the rest of the necessary engine components forming part of an external-heat engine 5. These are known to a person skilled in the art.

[0032] The inlet-valve arrangement 1 comprises a first poppet valve 6 of a design known per se with a valve head 8 and a valve stem 10, a valve seat 12, a valve guide 14 and a valve spring 16, which is connected to the valve stem 10 by means of a collar 18. The poppet valve 6 has a center axis 20.

[0033] A rocker arm 22 is pivotably supported in a supporting piston 24 and arranged to open the poppet valve 6, as a roller 26 in the rocker arm 22 is resting against a camshaft 28. The components 22 to 28 constitute a valve actuator 29.

[0034] The supporting piston 24, which is hydraulically operated, is arranged to maintain a desired clearance between the valve stem 10 and the rocker arm 22 when the poppet valve 6 is resting against the valve seat 12.

[0035] An inlet channel 30 extends through the cylinder head 2 and join a cylinder not shown above the piston 4. The valve seat 12 is in the inlet channel 30 and, together with the poppet valve 6, defines a dead volume 32 of a working chamber 33.

[0036] The dead volume 32 consists of the volume of the working chamber 33 located between the closed poppet valve 6 and the piston 4 when the piston 4 is in its position nearest to the cylinder head 2. The dead volume 32 contributes to a reduction in the compression/expansion ratio, and a larger dead volume 32 thereby reduces the efficiency. The piston 4 has a center axis 34.

[0037] As shown in FIG. 1, the center axis 20 of the poppet valve 6 is practically perpendicular to the center axis 34 of the piston, as indicated by the angle 36. As discussed in the general part of the document, the angle 36 is chosen on the basis of practical conditions with chief emphasis on reducing the dead volume 32.

[0038] It is sought to reduce the dead volume 32 by other measures as well, such as letting the valve guide 14 project the furthest possible into the dead volume 32, giving the part of the valve guide 14 that is in the dead volume 32 a suitable shape, disposing material 37 in places in the dead volume 32 where it does not obstruct the flow of working fluid to any degree worth mentioning and providing the piston 4 with a piston head 38, which is designed to reduce the dead volume 32 when the piston 4 is in its position nearest to the cylinder head 2, see FIG. 4 as well.

[0039] In an alternative embodiment, see FIG. 2, the cylinder head 2 is formed with a second poppet valve 6a, which has a smaller head diameter than the first poppet valve 6. The second poppet valve 6a closes against a second valve seat 12a of a correspondingly smaller diameter, and is controlled in the same way as the first poppet valve 6 by a rocker arm 22a, the equivalent components being identified by the same reference numerals with addition of the letter a.

[0040] A section II-II in FIG. 3 shows the arrangement of the second poppet valve 6a in the cylinder head 2.

[0041] As the pressure difference across the first poppet valve 6 in its closed position may be considerable, the force that has to be applied to the valve stem 10 to open the first poppet valve 6 is relatively large. Such a relatively large force may reduce the life of the rocker arm 22 and adjacent components.

[0042] It may therefore be appropriate to let the second poppet valve 6a open somewhat before the first poppet valve 6 to equalize the pressure across the first poppet valve 6 before it is opened, which reduces the required opening force.

[0043] A poppet valve in the form of an outlet valve 44 from the working chamber 33 is indicated in FIG. 1. The positioning of the outlet valve 44 relative to the piston 4 may be a conventional one or be formed in some other practical way.

[0044] It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art will be able to form many alternative embodiments without departing from the scope of the dependent claims.

[0045] In the claims, reference numbers in parentheses are not to be regarded as restrictive.

[0046] The use of the verb to comprise and its different forms does not exclude the presence of elements or steps, which are not mentioned in the claims. The indefinite article a or an before an element does not exclude the presence of a plurality of such elements.