GB1567538A - Cylinder head for reciprocating piston internal combustion engine - Google Patents

Description

(54) CYLINDER HEAD FOR RECIPROCATING PISTON INTERNAL COMBUSTION ENGINE (71) We, KLÖCKNER-HUMBOLDT- DEUTZ AKTIENGESELLSCHAFT, a German Body Corporate, of Kdln-Deutz, German Federal Republic, 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: This invention relates to a cylinder head for a reciprocating-piston internal combustion engine in which a valve body (of, for example, an inlet or exhaust valve) comprises a unit, generally known as a valve cage and referred to as such below, inserted in a bore in the cylinder head. The valve cage is held in place by securing means which prevent it from moving axially of its bore out of the cylinder head.The cage is generally cylindrical, and is formed with an axial bore and a passage transverse to the axial bore. The axial bore receives and guides the stem of a valve member which seats on the valve cage, and the transverse passage opens onto the outer wall of the generaly cylindrical cage where in communicates with a gas flow duct in the cylinder head.

Experience has shown that a disadvantage of known cylinder heads of the kind described in the preceding paragraph is that (particularly in the case of exhaust valves of a large engine which is supercharged and uses heavy fuel) the cage is liable to deform in such a way that the axial bore which receives and guides the stem of the valve member is no longer true. This may result in the stem of the valve member bending, and/or the valve member may no longer seat properly, and thus wears rapidly. The deformation of the cage may also prevent it from forming a gas-tight seal with the bore in the cylinder head in which it is disposed.

An aim of the invention is to provide a cylinder head in which the problems discussed above which result from valve cage deformation are less likely to arise.

Our research has shown that one cause of the deformation of the valve cage is that it is weakened in the region where the transverse passage opens onto the outer wall of the valve cage so that bending occurs in use of an engine having the cylinder head due to the axial forces which are exerted by the securing means which hold the cages in place. Bending occurs particularly when the cages are highly stressed or very hot. In the known arrangements, the resultant of these axial forces is a force acting co-axially with the central axis of the valve cage.

With a view of overcoming the disadvantages described above, this invention is directed to a cylinder head for a reciprocating-piston internal combustion engine in which a valve cage is inserted in a bore in the cylinder head, the valve cage having an axial bore and a passage transverse to the axial bore, the axial bore serving to receive and guide a stem of a valve member, and the transverse passage opening onto the outer wall of the generally cylindrical cage to communicate with a gas flow duct in the cylinder head, the valve cage being held in place by securing means so disposed and tightened that the resultant force of the forces which the securing means exert on the cage acts along an axis (referred to herein as a line of maximum endurable compressive stress) substantially co-incident with an axis parallel to a central axis of the cage and passing through the centre of gravity of a cross-section of the cage which is perpendicular to the axial bore and passes through the transverse passage, said cross section being in the region of minimum cross-sectional area of the cage.

The said line of maximum endurable compressive stress is of course spaced away from the region where the transverse passage opens onto the curved wall of the cage, so that the cage is better able to withstand a force acting along the latter line than it is able to withstand a force acting along its central axis. Thus, the cage of a cylinder head according to the invention is less likely to deform in use giving rise to the problems described above than is a cage of a cylinder head in which the cage is held in place by conventional securing means.

The securing means may comprise bolts the central longitudinal axes of which are spaced equidistantly from the said line of maximum endurable compressive stress of the cage.

In this case, the bolts would be equally tightened. If, on the other hand, the bolts, axes are not disposed equidistantly from the said line, (for example the bolt axes may be equidistant from the central axis of the cage), then the bolts would not be equally tightened, but bolts nearer to the said line would be tightened more to achieve the desired resultant force.

In an alternative arrangement in which a pair of cages are mounted in respective cylinder head bores, the securing means can include a bridge member which spans the cages and clamps both of them in place, the forces which the bridge member exerts on each cage being located at two regions located one at each side of the respective cage, which regions lie on respective straight lines intersecting the respective lines of maximum endurable compressive stress of the cages, the bridge itself being secured to the cylinder head by a bolt disposed on a straight line which is perpendicular to and connects the respective lines of maximum endurable compressive stress of the cages.

Examples of a cylinder head according to the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a longitudinal section through a valve cage, Figure 2 is a cross-section through the valve cage along line II-II in Figure 1, this cross section being taken through a part of the cage of minimum cross-sectional area, Figure 3 shows a portion of a cylinder head comprising two valve cages secured by flanges, and Figure 4 shows an arrangement comprising two valve cages both secured via a bridge.

Figures 1 and 2 show a generally cylindrical valve cage 1 inserted from the exterior into a bore 2 in a cylinder head 3. The top edge of cage 1 has a flange 4 clamped to the cylinder head 3 by bolts 5 (three bolts 5 as shown by Figure 2). Valve cage 1 also has a cooling-agent chamber 6 and a gas flow chamber 7. The gas flow chamber 7 is connected to a transverse passage having an inlet or outlet aperture 8 (depending on whether the valve is an inlet or exhaust valve) which aperture 8 opens onto a curved face of the cage to communicate with a gas flow duct 9 in cylinder head 3. In this region, where the aperture 8 extends through the surface of cage 1, the cage has a crosssectional area which is reduced as compared with its area on the other side of the cage's central axis (see Figure 2).A line 11 is shown in Figure 1 passing through the centre of gravity 10 (Figure 2) of the cross-section, parallel to the central axis of valve cage 1. The line 11 of Figure 1 has been extended to cross Figure 2 to assist in locating point 10 in Figure 2. The cage can best resist forces acting along this line 11 (Figure 1) which is termed a line of maximum endurable compressive stress. Bolts are disposed with their central longitudinal axes equidistant from line 11, and points 5 on the bolt axes are shown in Figure 2. The bolts have the same tightening torque, so that the resultant of the individual clamping forces of the bolts extends coaxially to the line 11 (Figure 1) of maximum endurable compressive stress.

Figure 3 illustrates a similar method of securing the valve cage 1. In Figure 3, flanges 4 are secured by only two "neckeddown" bolts 5 disposed symmetrically with respect to the line of maximum endurable stress (not shown).

In Figures 4, two valve cages 1, la are secured via a bridge 12. Bridge 12 is clamped to the cylinder head 3 by a bolt 5, which is disposed on a line 13 perpendicular to and connecting the respective lines of maximum endurable stress of cages 1, la.

Bridge 12 holds each cage 1, la in bores 2 via two pressure points 14. In order to clamp the valve cages 1 in optimum manner according to the invention, pressure-point lines 15 drawn between the pressure points 14 of respective valve cages 1 and la must intersect the connecting line 13 at points 10, 10a which lie on the respective lines of maximum endurable stress (notzshown) of the valve cages 1, la.

WHAT WE CLAIM IS: 1. A cylinder head for a reciprocatingpiston internal combustion engine in which a valve cage is inserted in a bore in the cylinder head, the valve cage having an axial bore and a passage transverse to the axial bore and axial bore serving to receive and guide a stem of a valve member, and the transverse passage opening onto the outer wall of the generally cylindrical cage to communicate with a gas flow duct in the cylinder head, the valve cage being held in place by securing means so disposed and tightened that the resultant force of the forces which the securing means exert on the cage acts along an axis (referred to herein as a line of maximum endurable

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

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. so that the cage is better able to withstand a force acting along the latter line than it is able to withstand a force acting along its central axis. Thus, the cage of a cylinder head according to the invention is less likely to deform in use giving rise to the problems described above than is a cage of a cylinder head in which the cage is held in place by conventional securing means. The securing means may comprise bolts the central longitudinal axes of which are spaced equidistantly from the said line of maximum endurable compressive stress of the cage. In this case, the bolts would be equally tightened. If, on the other hand, the bolts, axes are not disposed equidistantly from the said line, (for example the bolt axes may be equidistant from the central axis of the cage), then the bolts would not be equally tightened, but bolts nearer to the said line would be tightened more to achieve the desired resultant force. In an alternative arrangement in which a pair of cages are mounted in respective cylinder head bores, the securing means can include a bridge member which spans the cages and clamps both of them in place, the forces which the bridge member exerts on each cage being located at two regions located one at each side of the respective cage, which regions lie on respective straight lines intersecting the respective lines of maximum endurable compressive stress of the cages, the bridge itself being secured to the cylinder head by a bolt disposed on a straight line which is perpendicular to and connects the respective lines of maximum endurable compressive stress of the cages. Examples of a cylinder head according to the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a longitudinal section through a valve cage, Figure 2 is a cross-section through the valve cage along line II-II in Figure 1, this cross section being taken through a part of the cage of minimum cross-sectional area, Figure 3 shows a portion of a cylinder head comprising two valve cages secured by flanges, and Figure 4 shows an arrangement comprising two valve cages both secured via a bridge. Figures 1 and 2 show a generally cylindrical valve cage 1 inserted from the exterior into a bore 2 in a cylinder head 3. The top edge of cage 1 has a flange 4 clamped to the cylinder head 3 by bolts 5 (three bolts 5 as shown by Figure 2). Valve cage 1 also has a cooling-agent chamber 6 and a gas flow chamber 7. The gas flow chamber 7 is connected to a transverse passage having an inlet or outlet aperture 8 (depending on whether the valve is an inlet or exhaust valve) which aperture 8 opens onto a curved face of the cage to communicate with a gas flow duct 9 in cylinder head 3. In this region, where the aperture 8 extends through the surface of cage 1, the cage has a crosssectional area which is reduced as compared with its area on the other side of the cage's central axis (see Figure 2).A line 11 is shown in Figure 1 passing through the centre of gravity 10 (Figure 2) of the cross-section, parallel to the central axis of valve cage 1. The line 11 of Figure 1 has been extended to cross Figure 2 to assist in locating point 10 in Figure 2. The cage can best resist forces acting along this line 11 (Figure 1) which is termed a line of maximum endurable compressive stress. Bolts are disposed with their central longitudinal axes equidistant from line 11, and points 5 on the bolt axes are shown in Figure 2. The bolts have the same tightening torque, so that the resultant of the individual clamping forces of the bolts extends coaxially to the line 11 (Figure 1) of maximum endurable compressive stress. Figure 3 illustrates a similar method of securing the valve cage 1. In Figure 3, flanges 4 are secured by only two "neckeddown" bolts 5 disposed symmetrically with respect to the line of maximum endurable stress (not shown). In Figures 4, two valve cages 1, la are secured via a bridge 12. Bridge 12 is clamped to the cylinder head 3 by a bolt 5, which is disposed on a line 13 perpendicular to and connecting the respective lines of maximum endurable stress of cages 1, la. Bridge 12 holds each cage 1, la in bores 2 via two pressure points 14. In order to clamp the valve cages 1 in optimum manner according to the invention, pressure-point lines 15 drawn between the pressure points 14 of respective valve cages 1 and la must intersect the connecting line 13 at points 10, 10a which lie on the respective lines of maximum endurable stress (notzshown) of the valve cages 1, la. WHAT WE CLAIM IS:

1. A cylinder head for a reciprocatingpiston internal combustion engine in which a valve cage is inserted in a bore in the cylinder head, the valve cage having an axial bore and a passage transverse to the axial bore and axial bore serving to receive and guide a stem of a valve member, and the transverse passage opening onto the outer wall of the generally cylindrical cage to communicate with a gas flow duct in the cylinder head, the valve cage being held in place by securing means so disposed and tightened that the resultant force of the forces which the securing means exert on the cage acts along an axis (referred to herein as a line of maximum endurable

compressive stress) substantially co-incident with an axis parallel to a central axis of the cage and passing through the centre of gravity of a cross-section of the cage which is perpendicular to the axial bore and passes through the transverse passage, said crosssection being in the region of minimum cross-sectional area of the cage.

2. A cylinder head according to claim 1, in which the securing means comprise bolts the central longitudinal axes of which are spaced equidistantly from the said line of maximum endurable compressive stress.

3. A cylinder head according to claim 1, and including a pair of cages mounted in respective bores in the cylinder head, the securing means including a bridge member which spans the cages and clamps both of them in place, the forces which the bridge member exerts on each cage being located at two regions located one at each side of the respective cage, which regions lie on respective straight lines intersecting the respective lines of maximum endurable compressive stress of the cages, the bridge itself being secured to the cylinder head by a bolt disposed on a straight line which is perpendicular to and connects the respective lines of maximum endurable compressive stress of the cages.

4. A cylinder head substantially as described herein with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.

5. A reciprocating piston internal combustion engine having a cylinder head according to any preceding claim.