JP2000310103A - Rocker arm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rocker arm manufactured by a metallic injection molding sintering method and provided with high dimensional accuracy. SOLUTION: A rocker arm 1 provided on an internal combustion engine is constituted of an arm part 10 and a roller part 13. A base end of the arm part 10 is rotatably supported by making a rocker shaft 6 as a rotary shaft and a free end is abutted on a valve stem end 3c integrated with an intake valve 3. Between the base end and the free end, the roller part 13 which is abutted on cam parts 5a, 5b rotating by making a cam shaft 5 as a shaft is provided. Because the roller part 13 is pressed by the cam parts 5a, 5b and the arm part 10 is reciprocated, the intake valve 3 is opened and closed. The rocker arm 1 is manufactured by a metallic injection molding sintering method by using spherical water atomized raw material powder having chrome molybdenum steel composition as raw material powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocker arm,
In particular, the present invention relates to a roller-type rocker arm having a roller portion that is in rotational contact with a cam portion of a camshaft, and a slipper-type rocker arm in which a slipper surface that contacts the cam portion of the camshaft is provided in a part of the rocker arm. .

[0002]

2. Description of the Related Art In recent years, high-performance automobile engines have been required to have high rotation speed and high output. Accordingly, a rocker arm that reciprocates a valve stem by pressing a valve stem end of an intake valve or an exhaust valve of an internal combustion engine is required to have high strength and sliding resistance.

As a rocker arm having the above-mentioned characteristics, there has been proposed a so-called slipper type rocker arm in which a slipper surface in contact with a cam portion of a cam shaft is provided in a part of the rocker arm. As a rocker arm that further enhances the above characteristics, a roller portion that rotates and abuts on the cam portion of the cam shaft is provided in a part of the rocker arm, and the strength and sliding resistance characteristics of the rocker arm that contacts the cam portion are improved. A so-called roller type rocker arm with an increased height has been proposed.

On the other hand, in recent years, in order to reduce the price of products in the market, rocker arms are required not only to have the above-mentioned characteristics but also to have high productivity.
In order to satisfy this requirement, it is conceivable to manufacture the rocker arm by metal injection molding sintering (MIM). This is because a product manufactured by the metal injection molding sintering method requires little post-processing, and can achieve high productivity. Further, products manufactured by the metal injection molding sintering method have the characteristics of being resistant to tensile and elongation and having excellent impact resistance.

[0005]

However, in the conventional metal injection molding sintering method, when manufacturing a relatively small product, for example, a rocker arm for an engine of a model airplane, a certain degree of dimensional accuracy is required. However, in the case of a relatively large product, such as a rocker arm of an automobile engine, the dimension due to shrinkage due to high-temperature sintering for removing the binder during the manufacturing process is possible. Because of a large change, it was difficult to provide high dimensional accuracy. In particular, in high-performance car engines that require high rotation and high output, high dimensional accuracy is also required for the rocker arm. Therefore, use a rocker arm manufactured by metal injection molding sintering for a high-performance car engine. Had many problems.

Accordingly, an object of the present invention is to provide a rocker arm manufactured by a metal injection molding sintering method and having high dimensional accuracy.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises an arm portion and a roller portion rotatably supported by the arm portion, wherein a base end of the arm portion is an internal combustion engine. A free end of the arm portion abuts on a valve stem end portion of an intake valve or an exhaust valve of the internal combustion engine, and the roller portion is connected to the base end by the free end. In a rocker arm provided at a position between the ends and rotatably abutting on the cam portion of the camshaft of the internal combustion engine, at least the arm portion main body is formed by metal injection molding sintering using a spherical water atomized raw material powder. Provides rocker arms to manufacture.

Here, it is preferable that the spherical water atomizing raw material powder has a chromium molybdenum steel composition.

Further, the present invention provides a rocker arm having a rocker arm body having an arm portion and a slipper surface provided on the arm portion and in contact with a cam portion of a camshaft, using a spherical water atomized raw material powder. Thus, a rocker arm for manufacturing the rocker arm body by a metal injection molding sintering method is provided.

Here, the spherical water atomized raw material powder preferably has a chromium molybdenum steel composition.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rocker arm according to a first embodiment of the present invention will be described with reference to FIGS. The first embodiment of the present invention relates to a variable valve lift
The rocker arm has a timing mechanism (hereinafter, referred to as a "variable valve mechanism").

First, a configuration around a head portion of an internal combustion engine provided with a rocker arm and a configuration of the rocker arm will be described with reference to FIGS. As shown in FIG. 1, an intake valve port 2A is formed in the head portion 2 of the internal combustion engine, and an intake valve 3 for opening and closing the intake valve port 2A is provided. The intake valve 3 is provided with a substantially rod-shaped valve stem 3a having a shape extending upward. The valve stem 3a is fixed to the head section 2 and penetrates a guide cylinder 2a that surrounds the valve stem 3a.
The valve stem 3a is slidable with respect to the guide cylinder 2a. A first flange 2b projecting substantially in a flange shape from the guide cylinder 2a is provided in an upper portion of the guide cylinder 2a and exposed to the outside of the internal combustion engine head 2. Further, a second flange 3b fixed to the valve stem 3a and protruding from the valve stem 3a in a substantially flange shape is provided near the uppermost portion of the valve stem 3a.
The radius of the first flange 2b and the radius of the second flange 3b are the same. A valve spring 4 is provided between the first flange 2b and the second flange 3b.
Is urged upward. Since the second flange 3b, the valve stem 3a and the intake valve 3 are integrated, the second flange 3b
Is urged upward by the valve spring 4, so that the intake valve 3 is also urged upward, and the intake valve port 2A is closed by the intake valve 3 when the intake valve 3 is urged most upward.

As shown in FIG. 2, the rocker arm 1
Are first rocker arm portions 1 provided in parallel with each other.
0, an intermediate rocker arm 30 and a second rocker arm 20. The first rocker arm section 10 and the second rocker arm section 20 have a substantially vertically symmetrical shape, and the middle rocker arm section 30 has a right end part partially different from the other rocker arm sections. . Rocker arm 1
, The first, second and intermediate rocker arm portions 1
Through holes 1A are formed coaxially at the left ends 10a, 20a, 30a of 0, 20, 30, and a rod-shaped rocker shaft 6 fixed to the head 2 passes through the through holes 1A. The rocker arm 1 is rotatable around the rocker shaft 6 as a rotation axis. As shown in FIG. 1, the side surfaces of the first and second rocker arms 10 and 20 are substantially in the shape of "", and a screw hole (not shown) is formed in the right end by screwing. I have. A tappet screw 12 is screwed into the screw hole (not shown) in a direction from above to below. As shown in FIG. 2, rollers 13 and 23 are provided substantially coaxially at an intermediate portion between the first and second rocker arms 10 and 20, and their axes are provided in parallel with the rocker shaft 6.

The intermediate rocker arm 30 has no portion corresponding to the right ends of the first and second rocker arms 10 and 20. That is, the tappet screw 12 and the portion where the tappet screw 12 is screwed are the intermediate rocker arm 3.
The intermediate rocker arm 30 is formed only by the left end, through which the rocker shaft 6 penetrates, and the right end, on which the roller 33 is rotatably supported. The roller 33 is substantially coaxial with the rollers 13 and 23.

As shown in FIG. 1, the valve stem 3a
Is in contact with the lower end of the tappet screw 12 of the rocker arm 1. The rollers 13, 23 and 33 are in contact with the low-speed cam portions 5a, 5a and 5b of the rotatably provided camshaft 5. By changing the position of the cam surface of the low-speed cam portion 5a that contacts the rollers 13 and 23,
The first and second rocker arms 10 and 20 and the tappet screws 12 and 12 rotate integrally about the rocker shaft 6 and the tappet screw 12 presses the valve stem end 3c, whereby the valve stem 3a is reciprocated. .

As shown in FIG. 2, the first rocker arm 10, the second rocker arm 20, and the intermediate rocker arm 30 have roller fitting holes 10A and 20A, respectively.
A, 30A are formed, and these roller fitting holes 10
The rollers 13, 23, and 33 are arranged at A, 20A, and 30A. A cylindrical bottomed hollow portion is formed in the roller fitting hole 10A in the vertical direction in FIG. 2, and the lower portion has a bottom. A cylindrical bottomed hollow portion is formed in the roller fitting hole 20A in the vertical direction in FIG. 2, and the upper portion has a bottom. Also,
The roller fitting hole 30A is a substantially cylindrical through hole that goes in the vertical direction in FIG.

A cylindrical support shaft 10b for rotatably supporting the roller 13 coaxially is fitted and fixed in the roller fitting hole 10A. Similarly to the roller fitting hole 10A, cylindrical support shafts 20b and 30b for coaxially and rotatably supporting the rollers 23 and 33 are fitted and fixed to the roller fitting hole 20A and the roller fitting hole 30A. Have been. The inner diameters of the hollow portions of these support shafts 10b, 20b, 30b are the same. Between the support shafts 10b, 20b, 30b and the rollers 13, 23, 33 which coaxially surround these support shafts,
A needle bearing (not shown) is provided. By this needle bearing, the rollers 13, 23, 33
It is rotatable with respect to the support shafts 10b, 20b, 30b.

In the hollow portions of the support shafts 10b and 30b, a cylindrical switching piston 14, which has a radius substantially the same as the hollow portion and an axial length which is the same as the axial length of the support shafts 10b and 30b, respectively. 34 are provided respectively. The configuration inside the support shaft 20b will be described later. These switching pistons 1
Reference numerals 4 and 34 denote support shafts 10b and 30b and support shaft 30, respectively.
The switching piston 14 is provided so as to be slidable with respect to the support shaft 30b, and specifically, the switching piston 34 is provided so as to be able to extend and retract with respect to the support shaft 20b.

An oil supply passage (not shown) is provided at the bottom of the roller fitting hole 10A of the first rocker arm portion 10.

In the hollow portion of the support shaft 20b of the second rocker arm portion 20, there is provided a substantially cylindrical hollow switching piston 26 whose axial length is shorter than the axial length of the support shaft 20b. Intermediate rocker arm 3 of hollow piston 26
The return spring locking portion 2 for locking the return spring 25
6a is provided. A return spring 25 is provided between the return spring engagement portion 26a and the bottom of the roller fitting hole 20A, and urges the hollow switching piston 26 downward in FIG. The end surface of the return spring locking portion 26a is in contact with one end surface of the switching piston 34 and is flush with the lower surface of the second rocker arm portion 20.

As shown in FIG. 1, the camshaft 5 has a shape projecting outward in the radial direction of the camshaft 5.
There are two low-speed cam parts 5a, 5a and five high-speed cam parts 5b. The positional relationship between these cam parts is as follows.
b is sandwiched between the two low-speed cams 5a, 5a. That is, the low-speed cam portion 5a, the high-speed cam portion 5b, and the low-speed cam portion 5a are coaxially provided in order from the upper side to the lower side of the sheet of FIG. 1, and the rollers 13, 33, and 23 shown in FIG. The low-speed cam portion 5a, the high-speed cam portion 5b, and the low-speed cam portion 5a come into contact with each other from above the paper surface. The length of the low-speed cam portions 5a and 5a from the shaft to the most protruding portion is shorter than the length of the high-speed cam portion 5b from the shaft to the most protruding portion.

Next, the operation of the rocker arm 1 will be described. At the time of low-speed rotation, the switching pistons 34 and 14 respectively cause the switching shafts 34 and 14 to rotate by the urging force of the spring 25.
0b, the intermediate rocker arm 30
Are not connected to the first and second rocker arms 10 and 20. Since the rollers 13 and 23 are in contact with the low-speed cam portion 5a, the first and second rocker arms 10 and 20 are reciprocated by the low-speed cam portion 5a and the valve spring 4, respectively. Further, since the roller 33 of the intermediate rocker arm 30 is in contact with the high-speed cam 5b, the intermediate rocker arm 30 is separated from the first and second rocker arms 10 and 20 by the high-speed cam 5b. It is reciprocated. At this time, as described above, the intermediate rocker arm 30 is provided with the first and second rocker arms 1.
0 and 20 are not connected to each other, the reciprocating rotation of the intermediate rocker arm 30 is performed by the first and second rocker arms 10,
No effect on the 20 exercises. That is, the intake valve 3
(FIG. 1) is reciprocated only by the low-speed cam 5a irrespective of the rotation of the high-speed cam 5b.

At the time of high-speed rotation, the first rocker arm 1
The oil is supplied to an oil supply passage (not shown) provided at 0, and the hydraulic pressure acts on one end surface of the switching piston 14 in the support shaft 10b. Therefore, the switching piston 14 is pressed upward in FIG. 2 against the urging force of the spring 25, and the switching piston 1
The other end surface of the slider 4 slides into the support shaft 30b, and is inserted into both the hollow portion of the support shaft 10b and the hollow portion of the support shaft 30b. The movement of the switching piston 14 causes the first rocker arm 10 and the intermediate rocker arm 30 to reciprocate and rotate integrally. By the movement of the switching piston 14, the switching piston 34 in the support shaft 30b also moves at the same time, and the switching piston 34 is moved to the second rocker arm 20.
Is inserted into the hollow portion of the inner support shaft 20b. Accordingly, the switching piston 34 is inserted into both the hollow portion of the support shaft 30b and the hollow portion of the support shaft 20b. Thus, the intermediate rocker arm 30 and the second rocker arm 20 are reciprocally rotated together with the second rocker arm 20. That is, in this state, the first, second, and intermediate rocker arms 10, 20, and 30 reciprocate and rotate in an integrated state.
Here, since the high-speed cam portion 5b of the camshaft 5 is longer in the radial direction than the low-speed cam portion 5a, only the high-speed cam portion comes into contact with the roller 33 of the intermediate rocker arm portion 30, and the low-speed cam portion 5a is separated from the first and second rocker arms 10 and 20 and does not come into contact therewith. Therefore, the reciprocating rotation of the intermediate rocker arm 30 is transmitted to the first and second rocker arms 10 and 20, and the intake valve 3 (FIG. 1) is reciprocated only by the high-speed cam 5b. Become.

Thereafter, when the rotation returns from the high-speed rotation to the low-speed rotation, the oil supply to the oil supply path (not shown) in the first rocker arm 10 is not performed. The switching pistons 14, 34 in 10b, 20b, 30b are returned to the same position as in the initial low speed. That is, the first, second and intermediate rocker arms 10, 2
0 and 30 are separately rotated again, and the intake valve 3 is reciprocated only by the low speed cam portion 5a.

Next, the manufacture of the rocker arm 1 by the metal injection molding sintering method (MIM) will be described. The metal injection molding sintering method is a process of kneading and granulating raw material powder and binder,
The injection molding step, the degreasing step, and the sintering step are performed in this order.

First, the kneading and granulating step and the production of the raw material powder used in this step will be described. The characteristics required for the raw material powder to be kneaded include good fluidity during injection molding, good degreasing and preservation during degreasing, and isotropic shrinkage and high density during sintering. Is mentioned. When these requirements are satisfied and the cost is taken into consideration, it is considered that the raw material powder used is preferably produced by a water atomizing method. In general, the water atomization method can produce a wide variety of metal powders at low cost, but on the other hand, the powder shape is irregular, the tap density (powderability) is low, and the oxygen content by water and water vapor is high. There is also a disadvantage. Therefore, the method for producing the raw material powder used for producing the rocker arm 1 of the present embodiment includes:
A new water atomizing method is used in which the powder shape becomes spherical and the oxygen content is kept low.

The water atomizing method according to the present embodiment is characterized in that the water nozzle is a full cone type and secondary splitting by atomization occurs. In this water atomization method, a gas atomization phenomenon is caused by using a gas flow generated by a water jet, the molten metal is pulverized (primary splitting), and the droplets are immediately and continuously dispersed and supplied to a side wall of the water jet. It is further atomized (secondary split) by rapid water jet and rapidly solidified. The use of the inert gas reduces the water vapor and oxygen partial pressure, so that a powder having a low oxygen content can be obtained.

The raw material used in the water atomizing method is used for the purpose of achieving both the strength of the rocker arm 1 and the workability.
Chromium molybdenum steel (SCM415 material) equivalent is required. In this embodiment, the composition is 0.1% to 0.18% by weight of carbon, 0.25% or less of nickel, 0.9 to 1.2% of chromium, and 0.15 to 0.1% of molybdenum by weight%.
3%, silicon 0.15 to 0.35%, manganese 0.6
0.85%, Phosphorus 0.03% or less, Sulfur 0.03%
Hereafter, by making copper 0.3% or less and the balance iron,
The above-mentioned object is achieved.

With respect to the composition (% by weight) of the rocker arm body, the reasons for limiting each component are as follows. If the carbon content is less than 0.4%, hardness cannot be obtained, and if it exceeds 2%, the effect becomes insignificant. Therefore, it is set to 0.4 to 2% by the ordinary water atomization method. In the embodiment, the content is 0.13 to 0.18%. If it is less than 0.13%, the required strength cannot be obtained, and if it exceeds 0.18%, the hardness increases but the toughness decreases, making it unsuitable as a rocker arm. Nickel has an effect on hardenability, but is made 0.25% or less in order to increase the cost of the powder. Chromium is 2.0 to 6.0% in the ordinary water atomization method, but is 0.9 to 1.2% in the present embodiment.
If the content is less than 0.9%, the effect at the time of quenching is small, and if it exceeds 1.2%, the effect at the time of quenching does not increase. In order to obtain high-temperature strength and hardness, molybdenum is 6 to 24% in total with tungsten in a normal water atomization method, but is 0.15 to 0.3% in the present embodiment.
If the content is less than 0.15%, the effect at the time of quenching is small, and if it exceeds 0.3%, the effect at the time of quenching does not increase. Since silicon acts as a deoxidizing agent and further has the effect of increasing the hardness of the matrix, the content is set to 1.5% or less in a normal water atomizing method, but is set to 0.15 to 0.35% in the present embodiment. did. If it is less than 0.15%, it is difficult to suppress the amount of oxygen at the time of powdering, and if it exceeds 0.35%, the effect does not increase. Manganese also has a deoxidizing effect,
Further, since it has the effect of enhancing the hardenability, the water content is set to 1% or less in the ordinary water atomizing method.
0.6-0.85%. If it is less than 0.6%, it is difficult to suppress oxygen at the time of powdering, and if it exceeds 0.85%, the effect does not increase. Since phosphorus, sulfur, and copper are impurities, the content of phosphorus and sulfur is set to 0.03% or less, and the content of copper is set to 0.3% or less.

Further, in order to obtain a product having high dimensional accuracy, a binder property having a stable filling density and a high fluidity is required. In order to obtain the binder property, the water atomizing method according to the present embodiment is required. The metal raw material powder has an average particle size of 10 μm, and is mainly composed of fine powder of 20 μm or less. This is because the fluidity of the binder can be controlled by the weight ratio with the binder. The target weight ratio was 1.3.

The use of the raw material powder whose spherical shape by the above-mentioned water atomization method is spherical makes it possible to keep the oxygen content low. Therefore, even when a relatively large product such as a rocker arm is manufactured by the metal injection molding sintering method, the shrinkage ratio can be reduced, and a product with high dimensional accuracy can be manufactured.

The binder to be kneaded is indispensable at the time of injection molding.
A mixture of E), wax and oil is used, and a stable compound (mixture of metal raw material powder and binder) having a small influence on temperature and having a high fluidity is obtained by combining with a wax that does not separate. The metal powder and the binder are kneaded with a pressure kneader for 60 minutes. When the kneaded material cools, it is crushed and formed into pellets.

Next, the injection molding process will be described. The injection molding machine used here is basically the same as a plastic molding machine. The concept of molding is the same as for plastic. However, since the time from filling to cooling and solidification is short, it is necessary to prevent defects such as welds, which are likely to occur due to entrainment of air. In the present embodiment, pressure (injection cylinder pressure) control is performed instead of time (screw position) control. The pressure control after filling was a pressure control for gradually reducing the pressure from a constant pressure. In addition, the position of the air vent for improving the air bleeding property in the mold was set. The compound is injected into a mold for injection molding maintained at a temperature of 15 to 20 ° C. with an injection pressure of 1000 to 1000 ° C.
Injection is performed at 2000 kg / cm ² to form a rocker arm.

Since the pressure is controlled, stable filling is possible. In addition, since the pressure is controlled, the quality can be greatly improved. Further, since the position of the air vent is set, the filling efficiency can be increased, and the quality can be improved.

In the degreasing step, it is required that the degreasing be performed in a short time so that a heat load is not applied. Therefore, in the present embodiment, degreasing is performed by the AMAX method in which solvent extraction is performed. In the AMAX method, degreasing is performed by an AMAX degreasing device. That is, a degreasing tank for processing the work,
This is a degreasing apparatus constituted by a distillation tank for purifying a liquid, two pipes provided so that the liquid in the tank can flow between the two tanks, and a pump provided in an intermediate portion of the pipes. Methylene chloride is used as the solvent, and the temperature is 3
Keep at 0 ± 2 ° C. The immersion time is 10 to 15 hours. A degreased compact is obtained by this AMAX method.

The sintering process is basically the same as the ordinary powder metallurgy method. In this embodiment mode, it is performed in a vacuum furnace. Deformation such as warpage that occurs when sintering a hollow shape is performed by using a spacer in the direction of deformation to improve accuracy. More specifically, about the sintering process, the compact obtained by the degreasing process is
Heating at a heating temperature of 100 ° C./Hr in a vacuum of
After holding at 50 ° C. for 2 hours, sintering is performed for 1 hour at 1100 to 1400 ° C. while changing the sintering temperature.

The rocker arm obtained by the above steps hardly needs to be subjected to post-processing, and
It can have the characteristics of being strong against tensile and elongation and having excellent impact resistance.

A rocker arm 40 according to a second embodiment of the present invention will be described with reference to FIGS. The rocker arm 40 according to the second embodiment of the present invention includes:
It differs from the rocker arm 1 according to the first embodiment in that a variable valve mechanism is not provided. Further, the rocker arm 1 is different from the rocker arm 1 according to the first embodiment in that a pivot portion of a lash adjuster rotatably supports one end of the rocker arm 40 instead of the rocker shaft 6. The same members as those in the first embodiment are denoted by the same reference numerals.

As shown in FIG. 3, the rocker arm 4
0 is a pair of roller supporting wall portions 4 that face each other substantially in parallel.
0a, 40b, a valve engaging portion 40c (FIG. 4) connecting one side of each of the longitudinal ends thereof, and both wall portions 40a,
40b, a rocker arm portion including a pivot engaging portion 41 for connecting one stitch at the other end side in the longitudinal direction, and a roller 43 rotatably supported by roller supporting walls 40a, 40b.
And The pivot engaging portion 41 is provided with a hemispherical portion 41a protruding upward in FIG. 3, and the pivot portion 42 of the lash adjuster is engaged with the hemispherical portion 41a as shown in FIG. The rocker arm 40 is rotatably supported by the pivot 42 as a rotation axis. A valve stem end 3c integrated with an intake valve or an exhaust valve (not shown) is in contact with the valve engagement portion 40c. The valve stem end 3c is urged upward by a valve spring (not shown) integrally with an intake valve or an exhaust valve (not shown).

The roller 43 is rotatably supported between a pair of walls 40a, 40b of the rocker arm 40 via a shaft 42, and pivotally engages the walls 40a, 40b with the valve engaging portion 40c. It is arranged in a square through-hole 40 </ b> A formed by being surrounded by the portion 41. Roller 43
The cam portion 45a of the cam shaft 45 is in contact with the upper portion of the cam shaft 45. As in the case of the cam portion 5a of the first embodiment, the cam portion 45a partially protrudes from the axial center in a radial direction by a portion longer than other portions. The intake valve or the exhaust valve (not shown) is opened and closed by the contact pressing.

The method for manufacturing the rocker arm 40 is the same as the method for manufacturing the rocker arm 1 according to the first embodiment, and a description thereof will be omitted.

A rocker arm according to a third embodiment of the present invention will be described with reference to FIGS. The rocker arm 60 according to the third embodiment of the present invention is different from that of the second embodiment in that two valve engaging portions that come into contact with the valve stem end are provided. The first,
The same reference numerals are used for the same members as in the second embodiment.

The valve stem 3a is constantly urged upward by the valve spring 4, that is, in a direction in which an intake valve or an exhaust valve (not shown) is closed. As in the first embodiment, the rocker arm 60 includes a rocker arm 60 a and a roller 63.
It is composed of The rocker arm 60 is shown in FIG.
As shown in FIG. 5, the valve stem 3a has a substantially “Y” shape that is bifurcated on the left side, and the valve stem end 3c of the valve stem 3a is in contact with the tip of the bifurcated portion 60c of the rocker arm 60a. At the tip of the fork, a hemispherical recess (not shown) that is recessed toward the upper side of the paper surface of FIG. 6 is formed so that the valve stem end 3c can stably abut.

A roller 63 is provided at an intermediate portion of the rocker arm 60.
The cam surface 45 a provided on the cam shaft 45 is in contact with the roller 63. The other end of the rocker arm 60 is supported by a hydraulic lifter 65, and the rocker arm 60 is rotatable around the hydraulic lifter 65. The hydraulic lifter 65 includes a rocker arm 60.
Has a spherical sheet portion 65a connected to one end of the sheet member.
A concave spherical seat is formed below the rocking fulcrum 60b at one end of the rocker arm 60 facing the seat 65a, and the rocker arm 60 is mounted on the spherical seat of the hydraulic lifter 65 at the concave spherical seat. 65a. The oil between the cam surface 45a and the roller 63 is automatically corrected by supplying oil of a predetermined pressure to the hydraulic lifter 65 from an oil passage (not shown) formed in the head portion wall 2.

The roller 63 is provided at an intermediate portion of the rocker arm 60 as described above. The roller 63 is cylindrical and hollow inside, and a roller shaft 63a is provided at an axial center of the hollow portion. A needle bearing 63b is provided as a roller member between the roller 63 and the roller shaft 63a.

The operation of the rocker arm 60 due to the rotational contact between the cam portion 45a (FIG. 5) and the roller 63 is the same as the operation of the rocker arm 40 according to the second embodiment, and will not be described. In addition, rocker arm 6
0 is the same as the method of manufacturing the rocker arm 1 according to the first embodiment, and a description thereof will be omitted.

The rocker arm according to the present invention is not limited to the embodiment described above, and various modifications and improvements can be made within the scope described in the claims. For example, in the above-described embodiment, the rocker arm is so-called pivot type, that is, the base end of the rocker arm is rotatably supported by a support member fixed to the internal combustion engine, and the free end is the intake valve or the internal combustion engine. A rocker arm of the type in contact with the valve stem end of the exhaust valve, a so-called seesaw type, that is, a rocker arm in which an intermediate portion of the rocker arm is rotatably supported by a support member fixed to the internal combustion engine, One end may be in contact with a valve stem end portion of an intake valve or an exhaust valve of an internal combustion engine, and the other end may have a roller which is in rotational contact with a cam portion.

The first type of rocker arm is a so-called slipper type, that is, a rocker arm having a rocker arm main body having an arm portion and a slipper surface provided on the arm portion and in contact with a cam portion of a camshaft. Similar to the method of manufacturing the rocker arm according to the embodiment, the rocker arm may be manufactured by a metal injection molding sintering method using a spherical water atomized raw material powder.

A needle bearing may be provided between the roller 43 and the shaft 42 of the rocker arm 40 according to the second embodiment.

[0050]

According to the rocker arm according to the first and third aspects, since the rocker arm is manufactured by performing the metal injection molding sintering method using the raw material powder whose powder shape is made spherical by the water atomizing method, The oxygen content in the rocker arm can be kept low. For this reason, the shrinkage which has conventionally been a problem in the metal injection molding sintering method can be extremely reduced. Further, it is possible to provide a rocker arm for a high-performance car engine having high dimensional accuracy, which requires little post-treatment, is excellent in impact resistance and the like, due to the characteristics of the metal injection molding sintering method.

[Brief description of the drawings]

FIG. 1 is a partial side sectional view showing a rocker arm according to a first embodiment of the present invention.

FIG. 2 is a front partial sectional view showing the rocker arm according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing a rocker arm according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a rocker arm according to a second embodiment of the present invention.

FIG. 5 is a side view showing a rocker arm according to a third embodiment of the present invention.

FIG. 6 is a front view showing a rocker arm according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rocker arm 5 Camshaft 5a Low-speed cam part 5b High-speed cam part 6 Rocker shaft 10 First rocker arm 10a Left end 12 Tappet screw 20 Second rocker arm 20a Left end 30 Intermediate rocker arm 30a Left end 13,23,33,43, 63 Roller 40a Wall 40b Wall 40c Valve engaging part 41 Pivot engaging part 41a Hemisphere part 42 Pivot part 45 Cam shaft 45a Cam part 60a Rocker arm part 60c Left end part 65a Seat part

Continued on the front page F term (reference) 3G016 AA06 AA19 BB10 BB17 BB19 BB22 CA13 EA00 EA02 EA14 EA24 FA00 FA11 GA00 4K017 AA04 BA06 BB04 CA01 DA09 EB07 EB10 EK01 FA03 4K018 AA34 BB04 BC13 CA02 DA30 DA04

Claims (4)

[Claims] An arm, and a roller rotatably supported by the arm; a base end of the arm rotatably supported by a support member fixed to an internal combustion engine; The free end of the portion abuts against a valve stem end of an intake or exhaust valve of the internal combustion engine, and the roller portion is provided between the base end and the free end to provide a camshaft of the internal combustion engine. A rocker arm rotatably abutting on a cam portion, wherein at least the arm portion main body is manufactured by a metal injection molding sintering method using spherical water atomizing raw material powder. 2. The rocker arm according to claim 1, wherein said spherical water atomized raw material powder has a chromium molybdenum steel composition. 3. A rocker arm having a rocker arm body having an arm portion and a slipper surface provided on the arm portion and in contact with a cam portion of a camshaft, wherein the rocker arm is formed by using a spherical water atomized raw material powder. A rocker arm wherein the arm body is manufactured by a metal injection molding sintering method. 4. The rocker arm according to claim 3, wherein said spherical water atomized raw material powder has a chromium molybdenum steel composition.