JPH11107717A - Adjust screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve strength of a recessed part of an adjusting screw main body and a part in the vicinity of the adjusting screw main body without increasing surface pressure of a ceramic member and a recessed spherical surface, in the adjust screw formed in such a constitution that the recessed part is arranged coaxially with one end surface of the main body and the ceramic member formed in a circular shape viewed from the one end surface side of the recessed part is pressed in the recessed part. SOLUTION: The outer diameter Dt of a one end part in a recessed part 7 of a main body 2 is formed as a diameter larger than that of a screw 3 coaxially with the screw 3 in the range from one end 6 side to a position exceeding a bottom surface 7b of the recessed part 7 along an axis J direction of the screw 3. The thickness of a cylindrical part for composing the inner circumferential surface 7a of the recessed part 7 and an outer peripheral surface 16a corresponding to the inner circumferential surface 7a is thickened comparing with a part not having a large diameter, and thereby, its strength is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adjusting screw which is screwed to a rocker arm for driving an intake / exhaust valve of an engine (internal combustion engine) and used for adjusting a valve clearance and the like.

[0002]

2. Description of the Related Art A valve operating mechanism of an engine includes a method of transmitting the movement of a cam to a rocker arm via a push rod (OHV method) and a method of transmitting the movement of a cam to a rocker arm without a push rod (SOHC method). There is. In such a valve operating mechanism, an adjusting screw is screwed onto the rocker arm, and the tip of the adjusting screw is made to abut or press against an end of a mating member such as a push rod or a valve stem (hereinafter also referred to as pressing). It is configured. In such a mechanism, the valve clearance (tappet clearance) increases with the progress of wear of the movement transmitting portion of each member of the mechanism. Therefore, by adjusting the amount of protrusion of an adjusting screw (hereinafter, also simply referred to as a screw), the clearance is adjusted. Is adjusted (corrected) to an appropriate value.

[0003] Such an adjusting screw and a push rod or a valve stem as a mating member (hereinafter referred to as "the adjusting screw").
For example, the push rod has a convex spherical surface at the tip end of the screw and a concave spherical surface at the tip end of the push rod, and is configured to make spherical sliding contact under pressure contact. Conventionally, such adjustment screws are generally made of metal (such as hardened steel). However, in this case, there is a problem in adhesion due to collision or contact between metals with a push rod. In addition, the friction coefficient was large and the abrasion resistance was disadvantageous.

As a technique for solving such a problem, there is a technique described in Japanese Utility Model Laid-Open No. 62-203913. In this device, a concave portion is provided at the tip of a metal adjusting screw main body (hereinafter, also referred to as a screw main body or simply a main body), and a columnar ceramic member is press-fitted and fixed therein, forming a press contact surface with a push rod. The tip surface is ceramicized. By using such ceramics, collision or contact between the metal of the adjusting screw and the push rod is avoided, the adhesion and the friction coefficient are reduced, and the wear resistance is improved.

[0005]

At the tip of such an adjusting screw, the push rod not only reciprocates and collides in the axial direction of the screw, but also
When the rocker arm rotates (spherical sliding contact), it operates as follows. That is, at this time, as shown in FIG. 4, since the axis J direction of the adjusting screw (screw) 100 and the axis Jp direction of the push rod 61 intersect at an angle θ, the ceramic member 120 at the tip of the adjusting screw 100 External force F is applied obliquely from the lateral direction (axis Jp direction). The external force F exerts a bending action on the cylindrical portion 108 forming the concave portion 107 of the screw body 101 into which the ceramic member 120 is press-fitted. At this time, since the vicinity of the distal end surface of the main body 101 also has a screw structure, stress tends to concentrate on the thread valley at the root (bottom of the recess 107) of the cylindrical portion 108, and the root (point P) is used as a starting point. Sometimes it broke. As described above, when the ceramic member 120 is press-fitted into the concave portion 107 at the tip of the adjusting screw, there is a problem that the strength is reduced due to the complicated shape of the tip.

In recent years, the valve lift has been increased in view of the improvement of combustion efficiency and the like. Therefore, the impact of the push rod on the ceramic member 120 at the tip of the adjusting screw has been increasing. The risk of breakage is further increased. On the other hand, in order to increase the strength of this structure,
The thickness of the cylindrical portion 108 may be increased by reducing the inner diameter of the concave portion 107 of the screw body (tip) 101. However, in such a case, the diameter of the tip (convex spherical surface) of the ceramic member 120 is reduced. The surface pressure on the concave spherical surface of the push rod 61 or the like increases. Such an increase in the surface pressure hastens the abrasion of the concave spherical surface of the push rod made of metal and causes an increase in the valve clearance.

The present invention has been made in view of such problems, and an object of the present invention is to provide an adjusting screw in which a ceramic member is fixed to one end of an adjusting screw main body. An object of the present invention is to increase the strength of the concave portion of the adjusting screw main body and its vicinity without increasing the surface pressure with the concave spherical surface, and to prevent the same portion from being broken.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a metal adjusting screw body having a concave portion at one end surface coaxially with the screw, the concave portion being viewed from one end side thereof. In an adjusting screw in which a ceramic member having a circular shape is press-fitted, the adjusting screw body has an outer diameter of one end having the concave portion, which is coaxial with the screw and has a larger diameter than the outer diameter of the screw. It is characterized by the following.

In the present invention, as in the above means, the outer diameter of one end of the adjusting screw in the present invention is coaxial with the screw and larger than the outer diameter of the screw. The inner peripheral surface of the recess and the corresponding outer peripheral surface (outside) compared to the conventional main body that is not made larger in diameter
The thickness of the cylindrical portion formed by this is ensured to be large. Therefore, even if an external force acts on the ceramic member from a direction that intersects with the axis direction of the adjusting screw (the axis of the screw), it is possible to reduce the risk of breaking the concave portion of the screw body and its vicinity. .

[0010] Further, with the above configuration, the strength of the main body of the ceramic member can be increased without reducing the diameter of the ceramic member as viewed from the one end surface side. That is, when the push rod collides or is pressed, the spherical sliding contact area with the mating member is not reduced, and therefore, the strength is increased without increasing the surface pressure (pressure per unit area) at the time of the contact. Can be

The outer diameter of one end of the adjusting screw body is appropriately larger than the outer diameter of the screw so as to obtain a desired strength in accordance with the specific use of the adjusting screw and the material of the adjusting screw. Should be designed. However, it is preferable that the region having a large diameter be as large as possible from one end thereof along the axial direction of the screw, and more preferably as follows. That is, the adjusting screw main body is coaxial with the screw from the one end side to the position beyond the bottom surface of the concave portion along the axial direction of the screw from one end side of the adjusting screw body, and the outer diameter of the adjusting screw body is smaller than the outer diameter of the screw. Those having a large diameter are more preferable. In any of the above, the large-diameter one end side has an outer peripheral surface that is circular in cross section perpendicular to the axis of the screw, that is, it is most appropriate in terms of strength that its cross section is circular. is there.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to FIGS. In the figure, reference numeral 1 denotes an adjusting screw according to the present invention, and its screw body 2 is made of, for example, SNCM630 or SCM440, and has a predetermined length and a predetermined screw (M12 in this example) 3 cut on the outer periphery. ing. A slot 5 is cut into an end face 4 at one end (the upper side in FIG. 1) of the screw body 2. On the other hand, the other end side (the lower side in FIG. 1) of the screw body 2 has an end surface 6 having a tapered or spherical shape, and is coaxial with the axis J of the screw 3 and has an outer diameter Dt larger than the outer diameter of the screw 3.
And a large-diameter portion 16 having a circular shape. In the center of the large-diameter portion 16, a circular (columnar) concave portion (hole) 7 having a predetermined diameter d and a predetermined depth A is formed. The large-diameter portion 16 extends from the end face 6 along the direction of the axis J of the screw to a range of a dimension B. As shown in FIG. 1, the terminal end is located beyond the bottom surface 7 b of the concave portion 7. .

On the other hand, the following ceramic member 20 is fixed to the recess 7 by press fitting. That is, a cylindrical ceramic member 20 having a diameter d substantially equal to the diameter of the concave portion 7 and having a front end surface 21 formed in a convex spherical shape is press-fitted into the concave portion 7 with the flat end surface 22 as a back side. ing. The convex spherical surface of the tip end surface 21 of the ceramic member 20 is formed to have a predetermined radius (sphere R).

A tip surface (hereinafter also referred to as a convex spherical surface) 21 of the ceramic member 20 is projected from the end surface 6 of the screw body 2 by a predetermined amount. The screw body 2 does not interfere (contact) with the rods when sliding. In addition, a predetermined chamfer 24 is provided around an angle between the end surface 22 on the back side and the outer peripheral surface 23 to facilitate press-fitting. Furthermore, the length of the screw 3 of the screw body 2 is
The ceramic member 20 has such a length that it can pass through a screw hole for attachment in the rocker arm and can be locked at the other end with a lock nut via a washer. The tip surface (convex spherical surface) 21 of the ceramic member 20 has a surface roughness Ra:
It is preferable that the thickness be 0.5 μm or less. This is because while such a surface roughness can reduce the friction coefficient, such a surface roughness can be obtained easily and at low cost by barrel polishing or the like.

Such an adjusting screw 1 is screwed into a screw hole 52 of a rocker arm 51 as shown in FIGS. 2 and 3, for example, in an OHV valve mechanism, and a convex spherical surface 21 of a ceramic member 20 at a tip end thereof is pushed. Rod 61
Is pressed against the concave spherical surface 63 of the end portion 62 in a state where a predetermined valve clearance is secured.
The lock nut 56 is attached by tightening the lock nut 56 through the joint 5. As shown in FIG. 2, the rocker arm 51 for driving the valve 71 is driven via the rotation of the cam 81, via the tappet 82 and the push rod 61, and via the mounted adjusting screw 1.

However, when such a valve operating mechanism is driven, the concave spherical surface 63 of the push rod 61 collides with the convex spherical surface 21 of the ceramic member 20 at the tip of the adjusting screw 1, and the concave spherical surface 63 The convex spherical surface 21 repeats spherical sliding contact under pressure. At this time, the rocker arm 5
1 causes the concave spherical surface 63 of the push rod 61 to be attached to the ceramic member 2 at the tip of the adjusting screw 1.
The 0 convex spherical surface 21 comes into pressure contact with the screw 1 so that the axis J of the screw 1 intersects the axis Jp of the push rod 61 at the maximum angle θ (see FIG. 3).

In this embodiment, the ceramic member 20
Even if external force is applied from the diagonal side to the ceramic member 2
Since the thickness of the cylindrical portion formed by the inner peripheral surface 7a of the concave portion 7 into which the 0 is press-fitted and the corresponding outer peripheral surface 16a is formed as large as the large diameter portion 16 larger than the screw diameter, the main body 2 is formed. Is difficult to break. That is, since the outer peripheral surface 16a of the main body 1 near the end surface 6 where the concave portion 7 is formed has no screw and is larger in diameter than the outer diameter of the screw 3, the strength is high and the breaking is difficult. is there.

That is, like a conventional screw main body, in a main body which is threaded to an end surface or an outer periphery in the vicinity thereof, the thickness of the cylindrical portion formed by the inner peripheral surface of the concave portion and the corresponding outer peripheral surface is set to the above-mentioned value. In order to secure the same size as that of the form, the inner diameter of the concave portion must be reduced. And
The outer diameter of the ceramic member must be as small as the inner diameter of the recess. On the other hand, in the present embodiment, the outer diameter Dt of one end having the recess 7 is larger than the outer diameter of the screw 3.
The thickness of the cylindrical portion can be increased without reducing the outer diameter d of the ceramic member 20. Therefore, the area of the convex sphere brought into sliding contact with the concave spherical surface 63 such as the push rod 61 is not reduced, so that there is no increase in surface pressure.

The metal constituting the adjusting screw body may be appropriately selected from high strength metals such as SNCM, SCM and SUS. Incidentally, the ceramic member is formed by pressing and firing the raw material powder, and has a high hardness, high abrasion resistance, excellent mechanical strength, and mainly silicon nitride, silicon carbide, or zirconia. Those that do are appropriate.

Next, ten samples of the adjusting screw 1 having the above-described configuration formed by press-fitting the ceramic member 20 are manufactured for each large-diameter portion (Dt, B), and assembled into an engine having an OHV type valve operating mechanism. A test was performed under the following conditions, and the time required for the concave portion at one end of the main body and the vicinity thereof to break was confirmed. However, the main unit is SCM440
The inner diameter d of the concave portion on the end face is 8 mm and the depth A is 7
mm and the outer diameter Dt of the large-diameter portion is 11.2 to 14.
4 mm (D / d: 1.4 to 1.8), and the thickness B was 7 to 9.8 mm (B / A: 1.0 to 1.4).

The press-fitted ceramic member 20 is a silicon nitride sintered body (90 wt% Si 3 N 4, the remaining sintering aid), and has a diameter of 8 mm (the press-fitting allowance (set value) is 25 mm in diameter.
μm), height is 10 mm, and the tip surface has a radius of curvature R7.5 m
m (tolerance +0, -0.25 mm). However, the surface roughness of the convex spherical surface 21 was Ra: 0.2 to 0.5. And the push rod 61 which is the mating member is S5
0C, the concave spherical surface 63 has a radius of curvature of sphere R7.9 mm.
The surface hardness is set to Hv600 by quenching. In the comparative example, the outer diameter of the one end portion (region B) having the concave portion was the same as the outer diameter of the screw, and no screw processing was performed.

For such a sample, tappet clearance; twice the standard (0.6 mm), engine speed; maximum engine speed (3000 rpm) × 15
An endurance test (engine test) was performed under the condition of 0%, and the average value of the time until the tip of the main body (the concave portion and the vicinity thereof) was broken was measured. The results are as shown in Table 1.

[0023]

[Table 1]

As is evident from Table 1, the time to rupture of the samples (sample numbers 1 to 9) of the present invention is longer than the time to rupture of the comparative example (sample number 10).
In addition, it can be seen from the results that those having both large Dt / d and B / A have high strength.

Next, for the same sample, the screw main body is fixed in the same state as the screwed state to the rocker arm, and the angle θ between the axis J of the main body screw and the axis Jp of the mating member with respect to the ceramic member is determined. A static load was applied from a direction of 30 degrees through a pressing body having the same shape as the push rod (see FIG. 3), and the load (average value) until the fracture in the concave portion of the screw body and its vicinity was measured. The results are as shown in Table 2.

[0026]

[Table 2]

As is clear from Table 2, the breaking loads of the samples of the present invention (sample numbers 1 to 9) are all larger than the breaking load of the comparative example (sample number 10). Also from this result, it can be seen that those having large Dt / d and B / A have high strength. In particular, it can be seen that the B / A is effective even when the ratio is approximately 1. However, it is necessary to increase the B / A as much as possible. It can be said that it is preferable that the outer diameter of the screw is larger than the outer diameter of the screw coaxially with the screw up to a position exceeding the bottom surface of the concave portion.

The present invention is not limited to what has been described above, and can be embodied with appropriate design changes without departing from the scope of the invention. In the above description, the case where the adjusting screw is used for the OHV type valve mechanism has been described. However, the adjusting screw according to the present invention is pressed against the valve stem end as in the case of the SOHC type valve mechanism. The same effect is obtained even when used for a drive mechanism of an injector (fuel injection device).

[0029]

As is apparent from the above description, according to the adjusting screw of the present invention, the ceramic member is press-fitted without increasing the surface pressure when the ceramic member is pressed against the concave spherical surface of the mating member. The strength of the concave portion and the vicinity thereof is increased.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view and a partially enlarged view of an embodiment of an adjusting screw according to the present invention.

FIG. 2 is an explanatory view in which the adjustment screw of FIG. 1 is mounted on a rocker arm.

FIG. 3 is an explanatory view of a state in which the axis of the screw and the axis of the push rod are pressed against the convex spherical surface of the ceramic member via an angle θ in FIG. 2;

FIG. 4 is a view for explaining a problem of a conventional adjusting screw.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adjusting screw 2 Adjusting screw main body 3 Screw 6 One end face of main body 7 Concave part of one end face 7b Bottom of concave part 16 Large diameter part 20 Ceramic member Dt Outer diameter of one end part with concavity of main body

Claims (3)

[Claims] 1. An adjusting screw comprising a metal adjusting screw body having a concave portion at one end surface coaxially with the screw, and a ceramic member having a circular shape as viewed from one end surface side is press-fitted into the concave portion. The adjusting screw of the adjusting screw body, wherein an outer diameter of one end of the adjusting screw is coaxial with the screw and larger than an outer diameter of the screw. 2. An adjusting screw comprising a metal adjusting screw body having a concave portion at one end surface coaxially with the screw, and a ceramic member having a circular shape as viewed from one end surface side is press-fitted into the concave portion. The adjust screw body is coaxial with the screw and larger than the outer diameter of the screw from the one end side to the position beyond the bottom surface of the recess along the axial direction of the screw from one end side thereof. An adjusting screw characterized by having a diameter. 3. The adjusting screw according to claim 1, wherein the one end side having a large diameter has a circular outer peripheral surface in a cross section perpendicular to the axis of the screw.