JP2024002361A - cylinder head - Google Patents

Abstract

To provide a cylinder head which can ease heat stress acting on an inter-valve part between a pair of valve seats formed by padding parts.SOLUTION: A cylinder head 1 includes: a pair of ports 3, 3 located adjacent with each other in the same cylinder; and a pair of cylindrical recess parts 6, 6 provided at opening ends at the combustion chamber side of the pair of ports 3, 3. The cylinder head 1 includes a pair of valve seats 7, 7 each formed by an annular padding part 71 formed between a bottom surface 61 and an inner peripheral surface 62 of each of the pair of cylindrical recess parts 6, 6. The cylinder head 1 includes: an inter-valve recess part 9 provided at an inter-valve part 8 between the pair of cylindrical recess parts 6, 6; and stress easing walls 10, 10 formed between the inter-valve recess part 9 and the pair of cylindrical recess parts 6, 6. The stress easing wall 10 intersects with a straight line L connecting a lower end inner edge 72 with an outer edge upper end 73 of the padding part 71.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to cylinder heads.

2. Description of the Related Art Techniques for preventing cracks or unwelded portions from occurring in valve seats have been known in the art regarding cylinder heads. For example, the cylinder head described in Patent Document 1 below has intake and exhaust valve seats on which a cladding layer is formed (Patent Document 1, paragraph 0011 and claim 4). The cladding layer is created by irradiating the part where the valve seat will be formed with a laser to melt the base material and form a molten layer.Then, while supplying metal powder onto the molten layer, the base material and laser are rotated relative to each other. It is formed by laser irradiation and overlay.

This conventional cylinder head is characterized by the following configuration. A molten layer lap part in which a processing end part overlaps the processing start part of the molten layer and a clad layer wrap part in which a processing end part overlaps the processing start part of the clad layer are overlapped. Each intake/exhaust valve seat in the same cylinder is provided at a position other than the adjacent opposing portion. According to this conventional cylinder head, since cracks do not occur in the valve seat due to excessive thermal stress, reliability can be improved (Patent Document 1, paragraph 0013).

JP2009-047026A

In conventional cylinder heads as described above, the cladding layer of one of the two adjacent intake/exhaust valve seats in the same cylinder is usually formed first, and then the cladding layer of the other valve seat is formed first. will be formed later. In this case, the cladding layer formed first solidifies and contracts, resulting in a state in which thermal stress is applied to the intervalve region between adjacent valve seats. If the cladding layer of the other valve seat is formed in this state, the cladding layer of the valve seat formed later will crack due to the influence of thermal stress acting on the intervalve area due to the cladding layer formed earlier. may occur.

The present disclosure provides a cylinder head capable of relieving thermal stress acting on a valve gap between a pair of valve seats formed by a built-up portion.

One aspect of the present disclosure provides a pair of adjacent ports in the same cylinder, a pair of cylindrical recesses provided at the open ends of the pair of ports on the combustion chamber side, and a bottom surface and an inner periphery of the pair of cylindrical recesses. A cylinder head comprising a pair of valve seats constituted by an annular built-up part formed between the cylinder head and the valve seat, the cylinder head having an intervalve recess provided in an intervalve part between the pair of cylindrical recesses. and a stress relaxation wall formed between the intervalve recess and the pair of cylindrical recesses, the stress relaxation wall intersecting a straight line connecting the inner edge of the lower end and the upper end of the outer edge of the built-up part. This cylinder head is characterized by:

In the cylinder head according to the above-described aspect of the present disclosure, a built-up portion is first formed between the bottom surface and the inner peripheral surface of one of the pair of cylindrical recesses by a laser cladding method or the like, and the build-up portion is first formed on the other side. A pair of valve seats is formed by similarly forming a built-up portion later on in the cylindrical recess. At this time, the previously formed built-up part solidifies, and the lower inner edge of the built-up part joined to the bottom surface of the cylindrical recess and the upper edge of the outer edge of the built-up part joined to the inner peripheral surface of the cylindrical recess approach each other. It contracts like this. Then, in the valve space between the pair of cylindrical recesses, tensile stress is applied to the inner peripheral surface of one of the cylindrical recesses on which the built-up part was previously formed, from the upper end of the outer edge of the built-up part to the inner edge of the lower end. .

Here, in the cylinder head according to the above aspect, a stress relaxation wall is provided between the intervalve recess provided in the intervalve part between the pair of cylindrical recesses and one of the cylindrical recesses provided with the built-up part. is formed. This stress relaxation wall intersects a straight line connecting the inner edge of the lower end of the built-up portion and the upper end of the outer edge. Therefore, when a tensile stress is applied to the inner circumferential surface of one of the cylindrical recesses on which the built-up part was previously formed, from the upper end of the outer edge of the built-up part toward the inner edge of the lower end, the stress relaxation wall The valve is elastically deformed toward the inner edge of the lower end, and the thermal stress acting on the valve gap is alleviated.

Thereafter, a build-up part is formed by a laser cladding method or the like between the bottom surface and the inner peripheral surface of the other of the pair of cylindrical recesses on which the build-up part has not yet been formed. At this time, in the area between the valves between the pair of cylindrical recesses, the thermal stress acting on the area between the valves from the previously formed built-up part is alleviated by elastic deformation of the stress relaxation wall adjacent to the built-up part. has been done. Furthermore, as the built-up portion contracts on the inner circumferential surface of the cylindrical recess in which the built-up portion is formed later, tensile stress acts from the upper end of the outer edge of the built-up portion toward the inner edge of the lower end. Then, the stress relaxation wall adjacent to the built-up portion is elastically deformed toward the inner edge of the lower end of the built-up portion.

This further relieves the thermal stress acting on the valve gap between the pair of valve seats. As a result, the thermal stress that acts between the pair of built-up portions that constitute the pair of valve seats and the valve gap is reduced compared to the case where there is no intervalve recess and stress relaxation wall. Therefore, according to the cylinder head according to the above aspect of the present disclosure, the upper outer edge of the built-up part constituting the valve seat may peel off from the inner peripheral surface of the cylindrical recess, or the part between the valves near the upper end of the outer edge of the built-up part may peel off from the inner peripheral surface of the cylindrical recess. This prevents cracks from forming.

According to the above-mentioned aspect of the present disclosure, it is possible to provide a cylinder head capable of relieving thermal stress acting on a valve gap between a pair of valve seats formed by a built-up portion.

FIG. 1 is an enlarged view of a cylinder head showing an embodiment of the cylinder head according to the present disclosure. FIG. 2 is a sectional view taken along line II-II of the cylinder head shown in FIG. 1; 2 is an enlarged view of a cylinder head showing a modification of the cylinder head of FIG. 1. FIG. FIG. 3 is a sectional view corresponding to FIG. 2 of a conventional cylinder head.

Hereinafter, embodiments of a cylinder head according to the present disclosure will be described with reference to the drawings.

FIG. 1 is an enlarged view of a cylinder head 1 showing an embodiment of the cylinder head according to the present disclosure. FIG. 2 is a cross-sectional view of the cylinder head 1 shown in FIG. 1 taken along line II-II. The cylinder head 1 of this embodiment is, for example, a component that, together with a cylinder block (not shown), constitutes an internal combustion engine including a plurality of cylinders, such as a reciprocating engine installed in an automobile.

The cylinder head 1 has a plurality of combustion chamber upper portions 2 on an end face 1a facing a cylinder block. In addition, in FIG. 1, one combustion chamber upper part 2 of the cylinder head 1 is shown in an enlarged manner. Each combustion chamber upper part 2 is, for example, a concave portion that defines a part of the combustion chamber in each cylinder of the internal combustion engine together with each of the plurality of cylinders provided in the cylinder block.

The cylinder head 1 has two pairs of adjacent ports 3, 3 and ports 4, 4 in the same cylinder, that is, in the upper part 2 of each combustion chamber. Among these two pairs of ports 3, 3 and ports 4, 4, one pair of ports 3, 3 is an intake port, and the other pair of ports 4, 4 is an exhaust port. A plug hole 5 into which a spark plug is installed is provided in the center of the upper part 2 of the combustion chamber.

In the example shown in FIG. 1, cylindrical recesses 6 are provided at the open ends of a pair of adjacent ports 3, 3 within the same cylinder. These pair of cylindrical recesses 6, 6 are each cylindrical recesses in which the port 3 is opened at the center of the bottom surface 61 and the combustion chamber side is open. As shown in FIGS. 1 and 2, an annular built-up portion 71 constituting the valve seat 7 is provided between the bottom surface 61 and the inner peripheral surface 62 of each cylindrical recess 6. As shown in FIGS.

The built-up portion 71 can be formed by, for example, a laser cladding method. In the laser cladding method, alloy powder, which is the material for the built-up part 71, is automatically supplied by a feeder, and a laser beam is irradiated while moving relatively in a circular manner to the cylinder head 1. The built-up portion 71 is formed by melting and solidifying a portion of the base material and the alloy powder. Note that the method for forming the built-up portion 71 is not limited to the laser cladding method, and may include other fusion-type formation methods such as arc welding, TIG welding, or thermal spraying, or non-fusion-type formation methods such as cold spray or vibration welding. The formation method can be adopted.

The cylinder head 1 of this embodiment further includes an inter-valve recess 9 provided in an inter-valve portion 8 between the pair of cylindrical recesses 6 . In the example shown in FIG. 1, the intervalve recess 9 is located between the outer edge of the combustion chamber upper part 2 and a pair of adjacent cylindrical recesses 6, 6 formed adjacent to the outer edge. It is provided at a position closer to the outer edge of the combustion chamber upper part 2 than the part where the interval between the recesses 6, 6 is the narrowest. Further, the inter-valve recess 9 has an open end located at the center of the combustion chamber upper part 2, and an opening that opens toward the part where the distance between the pair of cylindrical recesses 6, 6 is narrowest. .

Further, the cylinder head 1 of this embodiment further includes stress relaxation walls 10, 10 formed between the intervalve recess 9 and the pair of cylindrical recesses 6, 6. In the example shown in FIG. 1, the pair of stress relaxation walls 10, 10 extend in a circle from the outer edge of the combustion chamber upper part 2 adjacent to the pair of adjacent cylindrical recesses 6, 6 along the outer edges of the pair of cylindrical recesses 6, 6. It extends in an arc. Moreover, the pair of stress relaxation walls 10, 10 have an open end in front of the part where the pair of cylindrical recesses 6, 6 are closest to each other, and have an open end between the valve and the outer edge of the upper part 2 of the combustion chamber. A recess 9 is defined.

As shown in FIG. 2, the stress relaxation wall 10 is formed by, for example, a virtual straight line L connecting the lower inner edge 72 of the built-up part 71 and the outer edge upper edge 73 in a cross section along the depth direction and the radial direction of the cylindrical recess 6. intersects with. In other words, the thickness T of the stress relaxation wall 10 is, for example, from the inner circumferential surface 62 of the cylindrical recess 6 that forms the stress relaxation wall 10 with the intervalve recess 9 to the end surface 1a of the cylinder head 1 facing the cylinder block. is smaller than the distance D to the intersection point P between and the straight line L.

Furthermore, the bottom surface 91 of the inter-valve recess 9 that forms the stress relaxation wall 10 with the cylindrical recess 6 is located at the center of the cylindrical recess 6 than the intersection P between the end surface 1a of the cylinder head 1 facing the cylinder block and the straight line L. It has an outer edge 91a on the side. Further, the outer edge 91a of the bottom surface 91 of the intervalve recess 9 is provided at a position lower than the straight line L, that is, at a deeper position farther from the end surface 1a of the cylinder head 1 than the straight line L in the depth direction of the cylindrical recess 6. ing.

Hereinafter, the operation of the cylinder head 1 of this embodiment will be explained based on comparison with the conventional cylinder head 1C. FIG. 4 is a sectional view of a conventional cylinder head 1C corresponding to FIG. A conventional cylinder head 1C shown in FIG. 4 differs from the cylinder head 1 of this embodiment in that it does not have an intervalve recess 9 and a stress relaxation wall 10. The other configuration of the conventional cylinder head 1C shown in FIG. 4 is the same as that of the cylinder head 1 of this embodiment, so similar parts are given the same reference numerals and explanations will be omitted.

In a conventional cylinder head 1C as shown in FIG. 4, normally, of the two adjacent cylindrical recesses 6, 6 in the same cylinder, the built-up portion 71 constituting the valve seat 7 is placed first in one of the cylindrical recesses 6. The built-up portion 71 of the other cylindrical recess 6 is formed later. In this case, the built-up portion 71 formed first solidifies and contracts, resulting in a state in which thermal stress is applied to the intervalve portion 8 between the adjacent cylindrical recesses 6 . In this state, when the build-up part 71 is formed in the other cylindrical recess 6, the build-up part 71 formed earlier will be affected by the thermal stress acting on the intervalve part 8, and the build-up part 71 will be formed later. There is a possibility that cracks may occur in the raised portion 71, the intervalve portion 8, or the boundary portion thereof.

In contrast, the cylinder head 1 of this embodiment has a pair of adjacent ports 3, 3 in the same cylinder, and a pair of cylindrical recesses provided at the open end of the pair of ports 3, 3 on the combustion chamber side. 6,6. Further, the cylinder head 1 has a pair of valve seats 7, 7 formed by an annular built-up portion 71 formed between the bottom surface 61 and the inner circumferential surface 62 of each of the pair of cylindrical recesses 6, 6. We are prepared. Further, the cylinder head 1 has an intervalve recess 9 provided in the intervalve part 8 between the pair of cylindrical recesses 6 and 6, and a valve recess 9 formed between the intervalve recess 9 and the pair of cylindrical recesses 6 and 6. and stress relaxation walls 10, 10. This stress relaxation wall 10 intersects with a straight line L connecting the inner edge 72 of the lower end of the built-up portion 71 and the upper end 73 of the outer edge.

In the cylinder head 1 of this embodiment, a built-up portion 71 is first formed between the bottom surface 61 and the inner peripheral surface 62 of one of the pair of cylindrical recesses 6 by a laser cladding method or the like. Then, a built-up portion 71 is formed in the other cylindrical recess 6 in the same manner later, thereby forming a pair of valve seats 7, 7. At this time, the previously formed built-up part 71 solidifies, and the lower inner edge 72 of the built-up part 71 joined to the bottom surface 61 of the cylindrical recess 6 and the built-up part joined to the inner peripheral surface 62 of the cylindrical recess 6 The outer edge upper end 73 of 71 contracts so that they approach each other. Then, the intervalve part 8 between the pair of cylindrical recesses 6 and 6 is formed on the inner circumferential surface 62 of one of the cylindrical recesses 6 on which the built-up part 71 was previously formed, from the upper end 73 of the outer edge of the built-up part 71 to the lower end. Tensile stress acts toward the inner edge 72.

Here, the cylinder head 1 of this embodiment has an inter-valve recess 9 provided in the inter-valve portion 8 between the pair of cylindrical recesses 6 and 6, and one cylindrical recess 6 provided with the built-up portion 71. A stress relief wall 10 is formed between them. This stress relaxation wall 10 intersects with a straight line L that connects the inner edge 72 of the lower end of the built-up portion 71 and the upper end 73 of the outer edge. Therefore, when tensile stress is applied to the inner circumferential surface 62 of one of the cylindrical recesses 6 on which the built-up part 71 was previously formed, from the outer edge upper end 73 of the built-up part 71 toward the lower inner edge 72, the stress relaxation wall 10 The previously formed built-up portion 71 is elastically deformed toward the inner edge 72 of the lower end, and the thermal stress acting on the intervalve portion 8 is alleviated.

Thereafter, between the bottom surface 61 and the inner circumferential surface 62 of the other cylindrical recess 6 on which the built-up part 71 has not yet been formed, of the pair of cylindrical recesses 6, 6, a built-up part 71 is formed using a laser cladding method or the like. form. At this time, in the intervalve part 8 between the pair of cylindrical recesses 6 and 6, the thermal stress acting on the valve part 8 from the previously formed built-up part 71 is transferred to the stress relaxation wall adjacent to the built-up part 71. 10 is relaxed by elastic deformation. Further, when the built-up part 71 contracts on the inner circumferential surface 62 of the cylindrical recess 6 in which the built-up part 71 is formed later, tensile stress is applied from the upper end 73 of the outer edge of the built-up part 71 toward the inner edge 72 of the lower end. acts. Then, the stress relaxation wall 10 is elastically deformed toward the inner edge 72 of the lower end of the built-up portion 71 .

Thereby, the thermal stress acting on the intervalve portion 8 of the cylinder head 1 is further alleviated. As a result, compared to the conventional cylinder head 1C which does not have the intervalve recess 9 and the stress relaxation wall 10, the gap between the pair of built-up parts 71 formed in the pair of cylindrical recesses 6 and 6 and the intervalve part 8 is Thermal stress acting on the material is reduced. Therefore, according to the cylinder head 1 of this embodiment, the upper outer edge of the built-up part 71 constituting the valve seat 7 may peel off from the inner peripheral surface 62 of the cylindrical recess 6, or This prevents cracks from forming in the intervalve portion 8.

As described above, according to the present embodiment, the cylinder head 1 is capable of relieving the thermal stress acting on the intervalve portion 8 between the pair of valve seats 7 and 7 formed by the built-up portion 71. can be provided. Note that the configuration of the cylinder head according to the present disclosure is not limited to the configuration of the cylinder head 1 of the above-described embodiment. Hereinafter, a modification of the cylinder head 1 shown in FIG. 1 will be described with reference to FIG. 3.

FIG. 3 is an enlarged view of a cylinder head 1A showing a modification of the cylinder head 1 shown in FIG. The cylinder head 1A shown in FIG. 3 is different from the cylinder head 1 of the above-described embodiment in the configuration of the intervalve recess 9 and the stress relaxation wall 10. The other structure of the cylinder head 1A of this modification is the same as that of the above-described cylinder head 1, so similar parts are given the same reference numerals and a description thereof will be omitted.

In the cylinder head 1A of this embodiment, the inter-valve recess 9 is surrounded by the outer edge of the combustion chamber upper part 2 and the stress relaxation wall 10, and the combustion chamber upper part 2 where the pair of cylindrical recesses 6, 6 are closest. The end on the center side is closed. Further, in the stress relaxation wall 10, the tips of a pair of arcuate portions along the pair of cylindrical recesses 6, 6 are connected by a straight portion.

Although this cylinder head 1A has higher rigidity of the stress relaxation wall 10 than the cylinder head 1 of the above-described embodiment, it is possible to achieve the same effects as the cylinder head 1 of the above-described embodiment. In addition, in the cylinder head 1 according to the above-described embodiment and the cylinder head 1A according to the modified example thereof, after forming the built-up portions 71 in the pair of cylindrical recesses 6, 6, the inter-valve recesses 9 are formed by overlaying or the like. You can fill it up.

Although the embodiment of the cylinder head according to the present disclosure has been described above in detail using the drawings, the specific configuration is not limited to this embodiment, and design changes may be made within the scope of the gist of the present disclosure. Even if there are, they are included in this disclosure.

1 Cylinder head 3 Port 6 Cylindrical recess 61 Bottom surface 62 Inner peripheral surface 7 Valve seat 71 Overlay portion 72 Lower inner edge 73 Upper outer edge 8 Valve space 9 Valve space 10 Stress relaxation wall L Straight line

Claims (1)

A cylinder is formed between a pair of adjacent ports in the same cylinder, a pair of cylindrical recesses provided at the open ends of the pair of ports on the combustion chamber side, and a bottom surface and an inner circumferential surface of the pair of cylindrical recesses. A cylinder head comprising a pair of valve seats constituted by an annular built-up part,
further comprising: an intervalve recess provided in an intervalve region between the pair of cylindrical recesses; and a stress relaxation wall formed between the intervalve recess and the pair of cylindrical recesses;
The cylinder head is characterized in that the stress relaxation wall intersects with a straight line connecting the inner edge of the lower end and the upper end of the outer edge of the built-up portion.

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