Valve guide and assembly method of the same

Abstract

To provide a valve guide which can prevent cracks of a cylinder head when the valve guide is press-fitted and prevent removal of the valve guide from the cylinder head.SOLUTION: A valve guide 33 includes: a large diameter part 331 provided at a substantially center and having an outer diameter larger than an inner diameter of a valve guide press-fitting hole 21; small diameter parts 332 provided at both ends and each having an outer diameter which is smaller than or equal to the inner diameter of the valve guide press-fitting hole 21; a plurality of edges 333 which are provided protruding on an outer peripheral surface of the large diameter part 331; and a plurality of recesses 334 which are formed near the edges 333 on the outer peripheral surface of the large diameter part 331, each making a pair with the edge 333. When the valve guide 33 is press-fitted in the valve guide press-fitting hole 21 and then rotated, chips generated by the edges 333 scraping an inner peripheral surface of the valve guide press-fitting hole 21 enter the recesses 334 and adhere thereto.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a valve guide and a method for assembling the valve guide.

Background Art

[0002] Conventionally, a valve guide made of, for example, an iron-based sintered alloy, which has wear resistance and lubricity and guides the reciprocating motion of a valve (valve stem), has been mainly used in an aluminum alloy cylinder head. The valve guide is formed in a thin cylindrical shape so that the valve stem can slide on the inner surface (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The valve guide is formed in a substantially cylindrical shape and is press-fitted into the cylinder head with a specified press-fitting allowance by a method such as at normal temperature or cold shrink fitting. However, due to the residual stress during the manufacture of the cylinder head and the stress generated when the valve guide is press-fitted into the cylinder head, there is a risk that the cylinder head may crack when the valve guide is press-fitted.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a valve guide that can prevent cracking of the cylinder head when the valve guide is press-fitted and can prevent the valve guide from coming out of the cylinder head, and a method for assembling the valve guide.

Means for Solving the Problems

[0006] The valve guide according to one aspect of the present invention is a valve guide that is press-fitted into a valve guide press-fitting hole formed in a cylinder head and guides the reciprocating motion of a valve. The valve guide is provided substantially at the center, has a large-diameter portion whose outer diameter is larger than the inner diameter of the valve guide press-fitting hole, small-diameter portions provided at both ends whose outer diameter is smaller than or equal to the inner diameter of the valve guide press-fitting hole, a plurality of edges protruding from the outer peripheral surface of the large-diameter portion, and a plurality of depressions formed in the outer peripheral surface of the large-diameter portion. When the valve guide is rotated after being press-fitted into the valve guide press-fitting hole, the edges scrape the inner peripheral surface of the valve guide press-fitting hole, and the chips generated by scraping with the edges enter the depressions and adhere thereto.

[0007] According to the valve guide according to one aspect of the present invention, since the substantially central portion is a large-diameter portion whose outer diameter is larger than the inner diameter of the valve guide press-fitting hole, and both end portions are small-diameter portions whose outer diameter is smaller than or equal to the inner diameter of the valve guide press-fitting hole, when the valve guide is press-fitted into the cylinder head (valve guide press-fitting hole), the contact area between the valve guide and the cylinder head (valve guide press-fitting hole) can be reduced. Therefore, the stress generated by press-fitting can be suppressed (reduced), and cracking of the cylinder head can be prevented.

[0008] Further, when the valve guide is rotated after being press-fitted into the valve guide press-fitting hole, the inner peripheral surface of the valve guide press-fitting hole is scraped by the edges, and the chips generated thereby enter the depressions and adhere thereto. Therefore, the valve guide (the depressions formed on the outer periphery of the large-diameter portion) and the cylinder head (the inner peripheral surface of the valve guide press-fitting hole) are meshed in an uneven shape, and the valve guide can be prevented from coming off.

Effects of the Invention

[0009] According to the present invention, it is possible to prevent cracking of the cylinder head when press-fitting the valve guide, and it is also possible to prevent the valve guide from coming off from the cylinder head.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be denoted by the same reference numerals. Also, in each figure, the same elements will be denoted by the same reference numerals and redundant explanations will be omitted.

[0012] First, with reference to FIGS. 1 and 2 together, the configuration of the valve guide 33 according to the embodiment will be described. FIG. 1 is a cross-sectional view showing the valve guide 33 and a valve mechanism (direct-acting valve system) 30 to which the valve guide 33 is applied. FIG. 2 is a view showing the valve guide 33. In the present embodiment, the case where the valve guide 33 is applied to the valve mechanism 30 on the exhaust side will be described as an example.

[0013] In the cylinder head 20 of the engine, an intake port and an exhaust port 22 are formed for each cylinder (only the exhaust port 22 is shown in FIG. 1). An exhaust valve (hereinafter, sometimes simply referred to as "valve") 32 for opening and closing the exhaust port 22 is provided in the exhaust port 22.

[0014] The exhaust valve 32 has its valve stem 321 slidably inserted into a through-hole of a valve guide 33 fitted to the wall portion above the exhaust port 22 of the cylinder head 20. A valve seal (stem seal) 37 made of a rubber material or the like is attached to the upper end portion of the valve guide 33 that protrudes and is exposed from the fitting portion to the cylinder head 20 toward the valve spring 34 side. By this valve seal 37, the outer circumference of the valve stem 321 is elastically pressed and sealed.

[0015] Also, a retainer 36 is attached to the stem end of the exhaust valve 32 by a cotter pin (valve cotter) 35. A valve spring seat 38 is disposed on the wall surface of the cylinder head 20 facing the retainer 36, and a valve spring 34 is disposed between the valve spring seat 38 and the spring retainer 36.

[0016] Then, by the valve spring 34, the valve head of the exhaust valve 32 is pressed against the valve seat 39 to close the exhaust port 22, and the upper end surface of the stem end is in contact with the exhaust cam (hereinafter, sometimes simply referred to as "cam") 31.

[0017] Then, when the cam 31 rotates, the exhaust valve 32 opens and closes along the cam face (cam profile) against the biasing force of the valve spring 34.

[0018] Here, the valve guide 33 is made of, for example, an iron-based sintered alloy or the like, has wear resistance and lubricity, and is a member that guides the reciprocating motion of the exhaust valve 32 (valve stem 321). The valve guide 33 is press-fitted into the valve guide press-fitting hole (through-hole) 21 of the cylinder head 20 with a specified press-fitting allowance by a method such as at normal temperature or cold fitting.

[0019] In particular, the valve guide 33 has a function of preventing cracks in the cylinder head 20 when the valve guide 33 is press-fitted and preventing the valve guide 33 from coming out of the cylinder head 20.

[0020] Therefore, the valve guide 33 mainly includes a small-diameter portion (diameter-reduced portion) 332 provided at both ends and having an outer diameter smaller than or equal to the inner diameter of the valve guide press-fitting hole 21, and a large-diameter portion (diameter-expanded portion) 331 provided substantially at the center and having an outer diameter larger than the inner diameter of the valve guide press-fitting hole 21. Therefore, when the valve guide 33 is press-fitted, only the large-diameter portion 331 contacts the cylinder head 20 (the inner peripheral surface of the valve guide press-fitting hole 21), and the small-diameter portion 332 does not contact the cylinder head 20 (the inner peripheral surface of the valve guide press-fitting hole 21).

[0021] In addition, in order to more reliably prevent cracking (cracks) of the cylinder head 20 during press-fitting, the position and dimensions (axial length) etc. in the whole of the large-diameter portion 331 are set such that the large-diameter portion 331 contacts the thick portion of the cylinder head 20 in a state where the valve guide 33 is press-fitted into the valve guide press-fitting hole 21.

[0022] A plurality of edges (protrusions / cutting edges) 333 project from the outer peripheral surface of the large-diameter portion 331. In addition, a plurality of depressions (dimples) 334 are formed on the outer peripheral surface of the large-diameter portion 331. When the valve guide 33 is rotated after being press-fitted into the valve guide press-fitting hole 21, the edge 333 cuts the inner peripheral surface of the valve guide press-fitting hole 21. Then, the chips generated by being cut by the edge 333 enter (are accumulated) into the depression 334 and adhere (details will be described later).

[0023] The plurality of edges 333 are formed at equal intervals along the circumferential direction of the large-diameter portion 331. In addition, in the present embodiment, the plurality of edges 333 formed along the circumferential direction are formed in two rows along the axial direction. Note that the number of rows of the edges 333 is not limited to two rows, and may be one row, two rows, or three or more rows according to requirements etc.

[0024] Each of the plurality of edges 333 is formed to extend axially (parallel to the axis) when viewed radially. The size (height or length) of the edge 333 is set according to, for example, the amount of chips (adhered chips) generated by cutting the inner peripheral surface of the valve guide press-fitting hole 21. Each edge 333 may be inclined with respect to the axis so as to easily guide the chips described later into the recess 334. Further, in order to reduce the resistance during press-fitting, it is preferable that the tip of each edge 333 in the axial direction (press-fitting direction) is sharpened (formed sharp).

[0025] The plurality of recesses 334 are formed in pairs with the plurality of edges 333, in the vicinity of the plurality of edges 333, and at equal intervals along the circumferential direction of the large-diameter portion 331. Also, similar to the edge 333, in the present embodiment, the plurality of recesses 334 formed along the circumferential direction are formed in two rows along the axial direction. Note that the number of rows of the recesses 334 is not limited to two rows, and may be one row or three or more rows according to requirements and the like.

[0026] Each of the plurality of recesses 334 is preferably formed in a substantially hemispherical shape. However, the shape (outline) of the recess 334 may be, for example, a rectangle, a polygon, or the like. Note that the edge of the recess 334 is chamfered, and even when the valve guide 33 is rotated as described later, the cylinder head 20 (the inner peripheral surface of the valve guide press-fitting hole 21) is not cut.

[0027] With the configuration as described above, that is, the substantially central portion is the large-diameter portion 331 whose outer diameter is larger than the inner diameter of the valve guide press-fitting hole 21, and both end portions are the small-diameter portions 332 whose outer diameter is smaller than or equal to the inner diameter of the valve guide press-fitting hole 21. Therefore, when the valve guide 33 is press-fitted into the cylinder head 20 (valve guide press-fitting hole 21), the contact area between the valve guide 33 and the cylinder head 20 (valve guide press-fitting hole 21) is reduced. Therefore, the stress generated by the press-fitting is suppressed (reduced).

[0028] Then, after the valve guide 33 is press-fitted into the valve guide press-fitting hole 21 and rotated, chips generated by the inner peripheral surface of the valve guide press-fitting hole 21 being scraped by the edge 333 enter the recess 334 and adhere (see Fig. 3). As a result, the valve guide 33 (the recess 334 formed on the outer periphery of the large-diameter portion 331) and the cylinder head 20 (the inner peripheral surface of the valve guide press-fitting hole 21) will mesh with each other in a concave-convex shape. Here, since aluminum, which is the material of the cylinder head 20, has a low melting point and is a soft (high ductility) material, it easily adheres when scraped by the edge 333 made of, for example, an iron-based sintered alloy. Note that the chips may adhere to the edge 333.

[0029] Next, the method of assembling the above-described valve guide 33 will be described. First, in the press-fitting step, the above-described valve guide 33 is press-fitted into the valve guide press-fitting hole 21 formed in the cylinder head 20.

[0030] Subsequently, in the rotation step, the press-fitted valve guide 33 is rotated around the axis by a jig or the like while the torque is controlled. Then, chips generated by the inner peripheral surface of the valve guide press-fitting hole 21 being scraped by the edge 333 adhere to the cylinder head 20 (the inner peripheral surface of the valve guide press-fitting hole 21) in the recess 334 (see Fig. 3).

[0031] Here, the rotation angle of the valve guide 33 in the rotation step is preferably set according to the circumferential interval between the edges 333 so as not to exceed the rotation start position of adjacent edges 333. More specifically, for example, when the edges 333 are formed in two rows along the circumferential direction, the rotation angle is set to less than 180°. Similarly, for example, when the edges 333 are formed in four rows along the circumferential direction, the rotation angle is set to less than 90°.

[0032] As described in detail above, according to the present embodiment, since the substantially central portion is the large-diameter portion 331 having an outer diameter larger than the inner diameter of the valve guide press-fitting hole 21, and both end portions are the small-diameter portions 332 having an outer diameter smaller than or equal to the inner diameter of the valve guide press-fitting hole 21, when the valve guide 33 is press-fitted into the cylinder head 20 (valve guide press-fitting hole 21), the contact area between the valve guide 33 and the cylinder head 20 (valve guide press-fitting hole 21) can be reduced. Therefore, the stress generated by the press-fitting can be suppressed (reduced), and cracking of the cylinder head 20 can be prevented.

[0033] Further, when the valve guide 33 is rotated after being press-fitted into the valve guide press-fitting hole 21, chips generated by scraping the inner peripheral surface of the valve guide press-fitting hole 21 by the edge 333 enter the recess 334 and adhere. Therefore, the valve guide 33 (the recess 334 formed on the outer periphery of the large-diameter portion 331) and the cylinder head 20 (the inner peripheral surface of the valve guide press-fitting hole 21) are engaged with each other in a concave-convex shape, and the valve guide 33 can be prevented from coming off. That is, it is possible to compensate for (reinforce) the decrease in the pull-out resistance due to the reduction in the contact area between the valve guide 33 and the cylinder head 20 (valve guide press-fitting hole 21). Note that the chips may adhere to the edge 333.

[0034] As a result, cracking of the cylinder head 20 when the valve guide 33 is press-fitted can be prevented, and the valve guide 33 can be prevented from coming off from the cylinder head 20.

[0035] According to the present embodiment, the plurality of edges 333 are formed at equal intervals along the circumferential direction of the large-diameter portion 331, and each of the plurality of edges 333 is formed so as to extend in the axial direction when viewed from the radial direction. Therefore, when the valve guide 33 is rotated, the inner peripheral surface of the valve guide press-fitting hole 21 can be efficiently scraped by the edge 333. That is, chips can be efficiently generated and adhered. Further, since the tip of each of the plurality of edges 333 in the axial direction is sharp, the resistance when the valve guide 33 is press-fitted can be reduced.

[0036] According to this embodiment, a plurality of depressions 334 are formed in pairs with a plurality of edges 333, in the vicinity of the plurality of edges 333, and at equal intervals along the circumferential direction of the large-diameter portion 331, and each of the plurality of depressions 334 is formed in a substantially hemispherical shape. Therefore, the chips generated by being shaved off by the edge 333 can be efficiently and surely put into (accumulated in) the depression 334 and adhered.

[0037] According to this embodiment, in a state where the valve guide 33 is press-fitted into the valve guide press-fitting hole 21, the large-diameter portion 331 is set to contact the thick portion of the cylinder head 20. Therefore, it is possible to more surely prevent cracking of the cylinder head 20 during press-fitting.

[0038] According to this embodiment, the rotation angle of the valve guide 33 in the rotation process is set according to the circumferential interval between the edges 333 so as not to exceed the rotation start position of the adjacent edges 333. Therefore, it is possible to prevent the inner peripheral surface of the valve guide press-fitting hole 21 from becoming a state of being thread-stripped.

[0039] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiment, the case where the valve guide 33 is applied to the exhaust valve mechanism 30 has been described as an example, but the valve guide 33 may be applied to the intake valve mechanism.

[0040] Further, for example, the shape, size (height, length, etc.), number, arrangement, etc. of the edge (protrusion) 333 are not limited to the above embodiment. Similarly, the shape, size (depth, diameter, etc.), number, arrangement, etc. of the depression (dimple) 334 are not limited to the above embodiment. For example, the axial lengths of the large-diameter portion 331 and the small-diameter portion 332 can be arbitrarily set according to requirements and the like.

[0041] Further, for example, as shown in FIG. 4(a), the edge 333 may be inclined with respect to the axis to guide the chips into the recess 334. Also, as shown in FIG. 4(b), the recess 334 may be arranged on the front side (front) in the rotation direction of the edge 333. Further, as shown in FIG. 4(c), the edge 333 may be formed in the shape of the hiragana character "く", and the recess 334 may be arranged at the bent portion of the edge 333.

[0042] Also, the edge 333 in the first row and the edge 333 in the second row described above may be arranged with a circumferential shift (offset). Similarly, the recess 334 in the first row and the recess 334 in the second row may be arranged with a circumferential shift (offset).

Explanation of Reference Numerals

[0043] 20 Cylinder head 21 Valve guide press-fitting hole 22 Exhaust port 30 Valve mechanism (valve operating mechanism) 31 Exhaust cam 32 Exhaust valve 321 Valve stem 33 Valve guide 331 Large-diameter portion 332 Small-diameter portion 333 Edge 334 Recess 34 Valve spring 35 Cotter pin 36 Retainer 37 Valve seal 38 Valve spring seat 39 Valve seat

Claims

1. A valve guide that is press-fitted into a valve guide press-fitting hole formed in a cylinder head and guides the reciprocating motion of a valve, A large-diameter portion provided substantially at the center and having an outer diameter larger than the inner diameter of the valve guide press-fitting hole, Small-diameter portions provided at both ends and having an outer diameter smaller than or equal to the inner diameter of the valve guide press-fitting hole, A plurality of edges protruding from the outer peripheral surface of the large-diameter portion, A plurality of depressions formed in the outer peripheral surface of the large-diameter portion, and comprising: When the valve guide is rotated after being press-fitted into the valve guide press-fitting hole, the edge scrapes the inner peripheral surface of the valve guide press-fitting hole, A valve guide, characterized in that chips generated by scraping with the edge enter and adhere to the depression.

2. The plurality of edges are formed at equal intervals along the circumferential direction of the large-diameter portion, Each of the plurality of edges is formed to extend in the axial direction when viewed from the radial direction, and the tip in the axial direction is sharp. The valve guide according to claim 1.

3. The plurality of depressions are formed in pairs with the plurality of edges, in the vicinity of the plurality of edges, and at equal intervals along the circumferential direction of the large-diameter portion, Each of the plurality of depressions is formed in a substantially hemispherical shape. The valve guide according to claim 2.

4. A press-fitting step of press-fitting the valve guide described in claim 1 into a valve guide press-fitting hole formed in the cylinder head, A rotation step of rotating the valve guide press-fitted in the press-fitting step, scraping the inner peripheral surface of the valve guide press-fitting hole with the edge, and putting and adhering the generated chips into the depression. A method for assembling a valve guide, characterized by comprising:

5. The rotation angle of the valve guide in the rotation step is set according to the circumferential interval between the edges so as not to exceed the rotation start position of the adjacent edges. The method for assembling a valve guide according to claim 4.

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