JP4003561B2 - Cam follower - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cam follower.
[0002]
[Prior art]
In general, the cam follower is used in an engine valve mechanism such as an automobile and other various cam mechanisms.
[0003]
As shown in FIG. 14, the cam follower has a structure in which a support shaft 82 is bridged between a pair of side walls 81 a and 81 b of a body 80, and a roller 84 is interposed on the outer periphery of the support shaft 82 via a plurality of needle rollers 83. Is supported rotatably. In operation, the rotating cam 85 is brought into contact with the flat outer peripheral surface of the roller 84, whereby the body 80 is reciprocated in a predetermined direction.
[0004]
[Problems to be solved by the invention]
When there is very little lubricating oil in the cam follower installation environment, it is difficult for the lubricating oil film to remain at the contact portion between the cam 85 and the roller 84, so that it is likely to be in direct contact between metals, that is, in a solid contact state. It becomes easy to occur.
[0005]
On the other hand, as shown in Japanese Patent Laid-Open No. 3-78507, a lubricating oil film is provided by providing minute irregularities, oblique lattice-shaped polishing marks, herringbone-shaped concave grooves in a plan view, and the like on the outer peripheral surface of the roller. There is a proposal that makes it easier to hold.
[0006]
Note that the minute irregularities and polishing marks are merely provisions of a simple oil reservoir on the roller surface, but the herringbone-shaped concave grooves generate dynamic pressure with the cam. It is intended to enhance the lubricating action. However, it can be said that the herringbone-shaped concave groove requires complicated processing and increases costs. Moreover, since the opening edge (shoulder portion) of the concave groove has a substantially right-angled cross-sectional shape, it can be said that the oil film breakage is likely to occur at the opening edge particularly in a situation where there is little lubricating oil.
[0007]
[Means for Solving the Problems]
The cam follower according to the present invention includes a pair of opposing side walls, a support shaft attached in a state of being spanned between the pair of side walls, and a cam that is rotatably mounted in a region between the pair of side walls on the support shaft. A groove for generating a dynamic pressure between the circumferential surface of the cam and several half of the circumferential surface of the outer circumferential surface of the roller. It is provided so as to be parallel to the rotation axis and shifted in a bowl shape in the circumferential direction with respect to the region.
[0008]
In this case, for example, the groove provided in the roller retains the lubricating oil and generates dynamic pressure when the roller is rotated by the cam. Easy to keep.
[0009]
The groove can be set to have a cross-sectional shape that gradually becomes shallower toward the downstream side in the rotational direction of the cam. In this case, a wedge-shaped oil film is formed between the groove and the cam in the circumferential direction, and a dynamic pressure is generated between the groove and the groove as the cam rotates.
[0010]
The groove can be set to have a substantially V-shaped cross section that is deepest in the middle in the circumferential direction and gradually shallows toward both ends in the circumferential direction. In this case, since the groove direction exerts a wedge action in both the forward and reverse rotation directions of the cam, it becomes unnecessary to consider the relative position with the cam in the process of assembling the roller, and the assembly is simplified. You can do it.
[0011]
Furthermore, the said groove | channel can set the width | variety of the circumferential direction more than the depth of the deepest part. In this case, the wedge action due to the groove can be reliably exhibited.
[0012]
By the way, a plurality of rollers can be interposed between the roller and the support shaft. In this case, the roller is rolled and guided by a plurality of rollers, which is advantageous in reducing the torque of the roller.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
1 to 4 show an embodiment of a reference example . In the figure, 1 is a cam and 2 is a cam follower. Embodiments according to the present invention are shown in FIGS. 6 and 7 and will be described later.
[0014]
The cam follower 2 includes a body 3 having a pair of opposing side walls 3a and 3b, a support shaft 4 attached in a state of being spanned between the pair of side walls 3a and 3b, and a pair of side walls 3a and 3b in the support shaft 4. And a roller 5 that is rotatably mounted in the region. In operation, the rotating cam 1 is brought into contact with the outer peripheral surface of the roller 5 so that the body 3 is reciprocated in a predetermined direction.
[0015]
In the figure, a plurality of needle rollers 6 are interposed between the support shaft 4 and the roller 5, but the needle rollers 6 are eliminated so that the roller 5 is brought into sliding contact with the support shaft 4. Also good.
[0016]
Further, grooves 7 for holding a lubricating oil film and generating dynamic pressure between the roller 5 and the peripheral surface of the cam 1 are provided in a straight line in parallel with the rotation axis O at several places on the outer peripheral surface of the roller 5. Yes.
[0017]
The groove 7 has a substantially V-shaped cross section along the circumferential direction, that is, the center in the circumferential direction of the groove 7 is deepest and gradually becomes shallow toward both ends in the circumferential direction.
[0018]
In the groove 7, the relationship between the width A along the circumferential direction and the depth B of the deepest portion is A ≧ B. Specifically, for example, the circumferential width A can be set to 0.05 to 5 mm, and the depth B of the deepest portion can be set to 0.05 to 1 mm while maintaining the above relationship. Further, the number of the grooves 7 may be set such that the grooves 7 are arranged with respect to the convex portions of the cam 1 when the convex portions of the cam 1 come into contact with the roller 5. 10 or more, preferably about 30 are provided at intervals.
[0019]
The groove 7 can be formed by extrusion processing, cutting processing, press forming processing, photoetching processing, forging processing, drawing processing, or the like, and is formed by a die during forging in the state of a bar. You can also.
[0020]
Here, an example in which the groove 7 is formed by extrusion processing will be described. First, after shaping the outer shape of the roller 5, as shown in FIG. 4, by passing the roller 5 through the hole of the cylindrical mold 8, the circumference of the inner peripheral surface of the mold 8 is changed to several places. The outer peripheral surface of the roller 5 is plastically processed by the formed streak 8a. In the figure, the streak 8a is exaggerated. Thereafter, the roller 5 is subjected to heat curing treatment, polishing finishing treatment, and the like.
[0021]
When the groove 7 is formed in such a form, the mold 8 can be arranged on a series of manufacturing lines for manufacturing the roller 5, and therefore the step of forming the groove 7 is removed from the manufacturing line. It can carry out continuously with other processes, without. For this reason, the manufacturing efficiency of the roller 5 can be increased, and the productivity can be improved and the manufacturing cost can be reduced.
[0022]
In the embodiment described above, the lubricating oil existing in the periphery is easily held with respect to the groove 7 provided in the roller 5, and the circumferential direction of the groove 7 of the roller 5 when the roller 5 is rotated by the cam 1. Thus, a dynamic pressure is generated between the cam 1 and the roller 5 by the wedge action corresponding to the change in depth. For this reason, the cam 1 and the roller 5 are not easily brought into direct contact with each other, that is, solid contact, and are easily maintained in a mixed lubrication state. Therefore, even if the place where the cam follower 2 is installed is poorly lubricated, it is possible to improve the seizure resistance of the roller 5 and contribute to smooth rotation of the roller 5.
[0023]
Moreover, since the groove 7 of the roller 5 against which the cam 1 abuts has an obtuse angle at the shoulder of the opening edge, the oil film breaks at the shoulder even in a poorly lubricated state as compared with the concave groove as in the conventional example. Is less likely to occur. Therefore, the dynamic pressure can be stably generated, and good lubricity can be ensured at the contact portion between the cam 1 and the roller 5.
[0025]
(1) In the above embodiment, the opening edge of the groove 7 may be rounded. In this case, the oil film breakage due to the opening edge of the groove 7 is less likely to occur, and a good lubricating state with the cam 1 can be maintained.
[0026]
(2) Another reference example of the cam follower is shown in FIG. The crowning portions 9 can be provided at both axial ends of the outer periphery of the roller 5, and the grooves 7 can be provided in the axial intermediate region excluding the crowning portion 9 on the outer peripheral surface of the roller. In the figure, the crowning portion 9 is formed in a spherical shape with a single curvature radius, but may be any other known logarithmic curve shape or tapered shape. In such a roller 5, it is arbitrary which of the step of forming the crowning portion 9 and the step of forming the groove 7 is performed first. Also in this case, the same operation and effect as in the above embodiment can be obtained. Furthermore, when the axial width of the roller 5 is smaller than the axial width of the cam 1, the contact pressure distribution of the roller 5 with respect to the cam 1 can be made uniform, and edge loading can be suppressed. It is advantageous in preventing the above.
[0027]
(3) An embodiment of a cam follower according to the present invention is shown in FIGS. 6 and 7 show the roller among the elements constituting the cam follower. As shown in FIG. 6, the groove 7 provided in the roller 5 is provided so as to be parallel to the rotation axis O and shifted in a bowl shape in the circumferential direction with respect to the half area in the axial direction and the remaining half area of the roller 5. Can do. Also in this case, the same operation and effect as in the above embodiment can be obtained. In addition, since it becomes difficult for the lubricating oil in the groove 7 to come out from the end in the axial direction center of the roller 5 in each groove 7, the effect of easily retaining the lubricating oil in the groove 7 is also obtained. In addition to this configuration, as shown in FIG. 7, a crowning portion 9 similar to the above (2) may be further provided at both axial ends of the roller 5. Also in this case, the same operation and effect as in the above embodiment can be obtained.
[0028]
(4) Another reference example of the cam follower is shown in FIGS. The groove 7 provided in the roller 5 can be formed with a predetermined inclination with respect to the rotation axis O as shown in FIGS. In this case, it can be formed by various methods described in the above embodiment, but when formed by extrusion, the roller 5 may be passed through the hole of the mold 8 while rotating. In this case, since the area of the groove 7 in contact with the cam 1 is increased, the effect can be obtained more remarkably than the above embodiment.
[0029]
(5) The cross-sectional shape in the circumferential direction of the groove 7 provided in the roller 5 can be a cross-sectional shape that gradually becomes shallower toward the downstream side in the rotational direction of the cam 1 as shown in FIG. Also in this case, the same operation and effect as in the above embodiment can be obtained, and at the same time, the area of the outer diameter flat portion of the roller 5 is increased as compared with the above embodiment, so that the contact surface pressure with the cam 1 is reduced. A better lubrication state can be maintained, which can contribute to the improvement of the service life.
[0030]
(6) About the cross-sectional shape in the circumferential direction of the groove | channel 7 provided in the said roller 5, as shown in FIG. 11, it can be made into polygonal shape. That is, the groove 7 is deepest at the center in the circumferential direction, and the first slopes 7a and 7a are provided at both ends in the circumferential direction, and the second slope is formed from the first slopes 7a and 7a to the opening. Slopes 7b and 7b are provided, respectively. Also in this case, the same operation and effect as in the above embodiment can be obtained.
[0031]
By the way, the cam follower 2 described above can be used for rocker arms 10 and 20 of an engine valve mechanism such as an automobile as shown in FIGS. Of course, the cam follower 2 can be used for rocker arms other than these rocker arms 10 and 20 and various other cam mechanisms.
[0032]
The rocker arm 10 shown in FIG. 12 is called a center pivot type, and the cam follower 2 is provided at one end in the longitudinal direction of the body 3, the rocker shaft 30 is penetrated in the middle in the longitudinal direction, and the adjustment is performed at the other end in the longitudinal direction. The screw 11 is screwed. A stem end of a valve 31 of a valve mechanism installed in the cylinder head is brought into contact with the adjustment screw 11. As the cam 1 rotates, the body 3 is tilted with the rocker shaft 30 as a fulcrum, and the adjusting screw 11 is repeatedly displaced in the vertical direction to open and close the valve 31.
[0033]
The rocker arm 20 shown in FIG. 13 is called an end pivot type. The cam follower 2 is provided in the middle of the body 3 in the longitudinal direction, the valve insertion portion 12 is at one end in the longitudinal direction, and the other end in the longitudinal direction is upward. A hemispherical pivot 13 is provided. The pivot portion 13 is engaged with the upper end of a lash adjuster 32 installed on a cylinder head (not shown). As the cam 1 rotates, the body 3 is tilted with the pivot portion 13 as a fulcrum, and the valve insertion portion 12 is repeatedly displaced in the vertical direction to open and close the valve 31.
[0034]
In these rocker arms 10 and 20, the rotational speed of the cam 1 is slow when the engine speed is low, and the rotational speed of the cam 1 is fast when the engine speed is high. The groove 7 of the roller 5 against which the cam 1 abuts generates a dynamic pressure with the cam 1 by a wedge action due to a change in depth in the circumferential direction. Since the shoulder portion of the groove 7 has an obtuse angle or rounded shape, it is difficult for oil film breakage due to the shoulder portion of the opening edge of the groove 7 even in a poorly lubricated state, and the dynamic pressure can be stably generated. For example, good lubricity can be stably secured at the contact portion between the cam 1 and the roller 5.
[0035]
【The invention's effect】
In the present invention, the lubricating oil existing around the groove provided in the roller is easily retained, and when the roller is rotated by the cam, the dynamic pressure is applied between the cam and the roller by the roller groove. Therefore, the cam and the roller are unlikely to be in direct contact with each other, that is, solid contact, and the mixed lubrication state is easily maintained. Therefore, even when the cam follower is installed in poorly lubricated conditions, it is possible to provide a highly reliable cam follower, such as improving the seizure resistance of the roller and contributing to smooth rotation of the roller. .
[Brief description of the drawings]
1 is a sectional view showing a cam follower according to a reference example . FIG. 2 is a perspective view showing a cam and a roller in FIG. 1. FIG. 3 is a sectional view taken along line (3)-(3) in FIG. FIG. 5 is a side view of the roller in another embodiment of the reference example . FIG. 6 is a side view of the roller in the embodiment of the present invention. FIG. 8 is a side view of the roller in another embodiment of the present invention. FIG. 9 is a side view of the roller in another embodiment of the reference example . FIG. 9 is a developed view of the outer peripheral surface of the roller in FIG. FIG. 11 is a sectional view showing a modified example of a roller groove in another embodiment. FIG. 12 is a sectional view showing a modified example of a roller groove in another embodiment of the present invention. FIG. 13 is a side view showing an example of usage of the cam follower according to the present invention. FIG. 14 is a side view showing an example of usage. Side view of a Orowa EXPLANATION OF REFERENCE NUMERALS
DESCRIPTION OF SYMBOLS 1 Cam 2 Cam follower 3 Body 3a First side wall 3b of the body Second side wall of the body 4 Support shaft 5 Roller 7 Groove of roller

Claims (4)

A pair of opposing side walls; a support shaft attached in a state of being spanned between the pair of side walls; and a roller that is rotatably mounted on a region of the support shaft in a region between the pair of side walls and a cam is in contact with. Including
Grooves that generate dynamic pressure between the circumferential surface of the roller and the circumferential surface of the cam at several places on the circumferential surface of the roller are parallel to the rotation axis with respect to the half area in the axial direction of the roller and the remaining half area. A cam follower that is provided in a circumferentially shifted manner .   The cam follower according to claim 1, wherein the groove is set to have a cross-sectional shape that gradually becomes shallower toward a downstream side in the rotation direction of the cam.   2. The cam follower according to claim 1, wherein the groove is set to have a substantially V-shaped cross section that is deepest in the middle in the circumferential direction and gradually becomes shallow toward both ends in the circumferential direction.   The cam follower according to claim 2 or 3, wherein a circumferential width of the groove is set to be equal to or greater than a depth of the deepest portion.

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