JP2015140676A - Bearing member for valve gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bearing member for a valve gear, for preventing contact between the inner peripheral face of a cam cap and a journal, at a portion of the cam cap where a contact pressure is most applied.SOLUTION: A bearing member 34 for a valve gear 1 includes a cam shaft 20 having a cam 30 for opening/closing at least one of an intake valve and an exhaust valve, and a plurality of journal parts 36. The bearing member 34 has a cam cap 38 downward supporting the journal parts 36 of the cam shaft 20 so as to encircle them, and a bearing base part 40 upward supporting them. The inner peripheral face of the cam cap 38 opposed to the journal parts 36 is coated with a resin coating film 46a in such a manner that peripheral ends 46b, 46b of the resin coating film 46a are each thinner than a peripheral center 46c.

Description

  The present invention relates to a technology for a bearing member of a valve gear.

  2. Description of the Related Art Conventionally, an internal combustion engine such as an engine is provided with a valve operating device that opens and closes engine valves such as an intake valve and an exhaust valve. Such a valve operating device for an internal combustion engine includes a camshaft having a cam that opens and closes at least one of an intake valve and an exhaust valve, a plurality of journal portions, and a cam cap that supports the journal portion of the camshaft. And a bearing member having a bearing base.

  Conventionally, by providing a predetermined gap between the journal portion of the camshaft and the cam cap, between the journal portion of the camshaft and the bearing base, and by supplying lubricating oil to the gap, The rotation of the camshaft was made smooth.

  In addition, for the occurrence of wear between the camshaft journal and the cam cap, the sliding portion between the camshaft and the cam cap covers the portion where they slide with a resin coating film. Is disclosed (for example, see Patent Document 1).

JP 2010-24980 A

  However, in Patent Document 1, since the resin coating film is evenly provided on the entire inner peripheral surface of the cam cap, in the central portion of the cam cap where the surface pressure is most applied, the inner peripheral surface of the cam cap and the journal are arranged. Contact occurred and the resin coating was worn. As the resin coating film wears, the clearance at the center of the cam cap increases, making it difficult for oil film pressure to occur. When the oil film pressure was less likely to be generated, the contact between the inner peripheral surface of the cam cap and the journal occurred, and the resin coating film was worn.

Therefore, in view of such problems, the present invention provides a bearing member for a valve operating device that prevents contact between an inner peripheral surface of a cam cap and a journal at a portion where the surface pressure is most applied to the cam cap.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, according to the first aspect of the present invention, in the bearing member of the valve gear including a camshaft having a cam that opens and closes at least one of the intake valve and the exhaust valve, and a plurality of journal portions, the bearing member is the camshaft of the camshaft. A cam cap supported from above so as to surround the journal portion; and a bearing base supported from below; and an inner peripheral surface facing the journal portion of the cam cap is covered with a resin coating film; The circumferential direction both ends are formed so as to be thinner than the circumferential central part.

  According to a second aspect of the present invention, the thickness of the resin coating film in the central portion in the circumferential direction is formed so as not to exceed one third of the clearance in the range of minus 50 degrees Celsius to 150 degrees Celsius.

  As effects of the present invention, the following effects can be obtained.

  That is, it is possible to prevent contact between the cam cap inner peripheral surface and the journal at the circumferential central portion where the surface pressure of the cam cap is the highest.

The front view which shows the structure of the valve operating apparatus of the internal combustion engine which concerns on embodiment of this invention. The top view which shows the structure of the support structure of the camshaft which concerns on embodiment of this invention. Sectional drawing which shows the structure of the support structure of the camshaft in the AA line which concerns on embodiment of this invention. Sectional drawing which shows the structure of the support structure of the camshaft in the AA line which concerns on other embodiment of this invention. (A) Sectional drawing which shows the structure of the cam cap seen from the axial direction of the cam shaft. (B) Sectional drawing which shows the structure of the cam cap seen from the direction of the mating surface with a bearing base. The cross-sectional enlarged view which shows the structure of the support structure of the camshaft which concerns on embodiment of this invention.

  Embodiments of the present invention will be described.

  First, a rocker arm type valve operating apparatus which is an example of a valve operating apparatus for an internal combustion engine will be described. FIG. 1 is a front view showing an example of the configuration of a valve operating apparatus for an internal combustion engine according to the present embodiment. In the valve operating apparatus 1 for an internal combustion engine, a retainer 12 is attached to a stem 10 of an intake valve (or exhaust valve), and an end cap 16 is attached to a stem end 14. The stem 10 passes through the central portion of the disc-shaped retainer 12, and the retainer 12 is attached to the stem 10 so as not to move in the axial direction. Further, an unillustrated intake valve (exhaust valve) is urged so as to be closed by a compressed coil spring 18 provided in the retainer 12.

  A valve operating apparatus 1 for an internal combustion engine that opens and closes an unillustrated intake valve (exhaust valve) is driven by a camshaft 20 to which rotation of a crankshaft that is an output shaft of the engine is transmitted, and rotation of the camshaft 20. And a rocker arm 22. The rocker arm 22 is manufactured by pressing a forming material obtained by punching a steel plate.

  One end of the rocker arm 22 is supported by a pivot 26 provided on the cylinder head 24. A contact portion 28 that contacts the end cap 16 is provided at the other end of the rocker arm 22. Further, a roller 32 that contacts the cam 30 of the camshaft 20 is rotatably supported between the one end and the other end of the rocker arm 22.

  Therefore, when the camshaft 20 rotates and the cam 30 pushes the roller 32, the rocker arm 22 swings around the pivot 26, and the stem end 14 of the intake valve (or exhaust valve) is contacted by the contact portion 28 of the rocker arm 22. (Stem 10) is pushed. Then, based on the pressing force by the contact portion 28 and the urging force by the coil spring 18, the intake valve (or exhaust valve) reciprocates in the axial direction of the stem 10 to open and close.

  FIG. 2 is a plan view showing a support structure of the camshaft 20 according to the embodiment. FIG. 3 is a cross-sectional view showing a support structure of the camshaft 20 along the line AA in FIG. The valve operating apparatus 1 for the internal combustion engine includes a bearing member 34 that supports the camshaft 20 on the cylinder head 24 so as to be rotatable about the axis. The camshaft 20 includes a cam 30 and a journal portion 36. As shown in FIG. 3, the bearing member 34 includes a cam cap 38 and a bearing base portion 40, and the journal portion 36 is surrounded by the cam cap 38 and the bearing base portion 40. Therefore, the journal portion 36 is supported in a state surrounded by the recess of the cam cap 38 and the recess of the bearing base 40, that is, in a circular space surrounded by the recess. The cam cap 38 is fastened to the bearing base 40 and the cylinder head 24 by a fastener 42 such as a bolt. A predetermined clearance is provided between the cam cap 38 and the journal portion 36 and between the bearing base portion 40 and the journal portion 36. This is because the camshaft 20 rotates smoothly.

  FIG. 4 is a cross-sectional view showing another embodiment of the support structure of the camshaft 20 along the line AA in FIG. As shown in FIG. 4, a part of the cylinder head 24 is supported as a bearing base 40 of the bearing member 34, and the journal part 36 is supported in a state surrounded by a cam cap 38 and a part of the cylinder head 24 (bearing base 40). May be. Hereinafter, an example in which a part of the cylinder head 24 as shown in FIG. 4 is used as the bearing base 40 will be described.

  The cam cap 38 is fastened to the bearing base 40 (cylinder head 24) with a fastener 42 such as a bolt. The cam cap 38 normally receives clockwise torque due to friction generated during fastening. As described above, since a predetermined gap is provided between the cam cap 38 and the journal portion 36, the friction generated at the time of fastening causes friction with the center of the journal portion 36 (camshaft 20). As a result, the center of the cam cap 38 is displaced. Then, the cam cap 38 and the journal portion 36 are fastened in contact with each other.

  FIG. 5A is a cross-sectional view showing an example of the configuration of the cam cap 38 as viewed from the axial direction of the camshaft 20, and FIG. 5B shows the cam as viewed from the direction of the mating surface with the bearing base 40. It is sectional drawing which shows an example of a structure of a cap. As shown in FIG. 5, in this embodiment, a resin coating film 46 a is provided on the concave portion of the cam cap 38, that is, on the inner peripheral surface of the cam cap 38 facing the journal portion 36. In addition, the cavity part shown in FIG. 5 is the fastening hole 48 in which the fastener 42 is inserted.

  As shown in FIG. 5, the resin coating film 46 a is provided on the entire circumference of the inner circumferential surface of the cam cap 38 that faces the journal portion 36. In the present embodiment, the resin coating film 46a is provided on the entire circumference of the inner peripheral surface of the cam cap 38. However, the present invention is not limited to this. It can also be set as the structure provided in a part.

  Next, the resin coating film 46a is demonstrated using FIG.5 and FIG.6.

  The resin coating film 46a is a film provided for the purpose of reducing friction and improving wear resistance, and is formed of, for example, a resin such as epoxy, acrylic, or phenol. Resin Coating Film The resin coating film 46a is formed to have a thickness of several μm.

The circumferential ends 46b and 46b of the resin coating film 46a are formed to be thinner than the circumferential center 46c. That is, in this embodiment, as shown in FIG. 6, the thickness d1 of the resin coating film 46a at the circumferential ends 46b and 46b is formed to be approximately 0 mm.
Further, the thickness d2 of the resin coating film 46a in the circumferential central portion 46c is formed so as not to exceed one third of the clearance C in the range of minus 50 degrees Celsius to 150 degrees Celsius. Here, the clearance C is a difference between the inner diameter of the circular space surrounded by the recess of the cam cap 38 and the recess of the bearing base 40 and the shaft diameter of the journal portion 36 as shown in FIG. Further, the circumferential central portion 46 c is located on the uppermost side of the inner peripheral surface of the cam cap 38 when the cam cap 38 is attached to the bearing base 40. In other words, the thickness of the resin coating film 46 a is the thickest on the uppermost side of the inner peripheral surface of the cam cap 38. In this embodiment, as shown in FIG. The thickness d2 of the resin coating film 46a in the circumferential central portion 46c is 10 μm. Further, although the clearance C varies depending on the temperature, it is more than 30 μm even when it becomes the smallest in the range of minus 50 degrees Celsius to 150 degrees Celsius, which is a general usable temperature range of an internal combustion engine such as an engine. It is formed to be large.
The resin coating film 46a is formed in a smooth curved shape from the circumferential end 46b to the circumferential center 46c.

Next, the effect of increasing the oil film pressure by the resin coating film 46a will be described.
The thickness of the resin coating 46a is formed so as to increase from the circumferential end 46b on the upstream side in the rotation direction of the journal portion 36 toward the circumferential center 46c. In addition, a so-called wedge effect occurs due to the difference in film thickness between the circumferential end 46b and the circumferential center 46c, and the oil film pressure increases. The effect of increasing the oil film pressure is greatest at the circumferential center 46c where the difference between the clearance C and the thickness d2 of the resin coating 46a is the smallest.
Further, the surface pressure applied to the inner peripheral surface of the cam cap 38 and the inner peripheral surface of the bearing base 40 changes with the rotation of the camshaft 20, but the highest surface pressure is at the upper end.
Therefore, the journal portion 36 and the cam cap are formed even in the portion where the surface pressure is highest by configuring the circumferential portion 46c so that the difference between the clearance C and the thickness d2 of the resin coating 46a is the smallest. The contact with the inner peripheral surface of 38 can be prevented. For this reason, abrasion of the resin coating film 46a can be prevented, and a friction reduction effect can be obtained continuously.

  In the present embodiment, the thickness d1 at the circumferential ends 46b and 46b of the resin coating 46a is set to 0 mm. However, the thickness d1 at the circumferential ends 46b and 46b is not limited to this. What is necessary is just to be comprised so that it may become smaller than thickness d2 in the circumferential direction center part 46c.

As described above, in the bearing member 34 of the valve gear 1 including the camshaft 20 having the cam 30 that opens and closes at least one of the intake valve and the exhaust valve and the plurality of journal portions 36, the bearing member 34 is a camshaft. 20 has a cam cap 38 supported from above so as to surround the journal portion 36 and a bearing base 40 supported from below, and the inner peripheral surface of the cam cap 38 facing the journal portion 36 is covered with a resin coating 46a. The circumferential end portions 46b and 46b of the resin coating film 46a are formed so as to be thinner than the circumferential central portion 46c.
With this configuration, it is possible to prevent contact between the inner peripheral surface of the cam cap 38 and the journal portion 36 at the circumferential central portion 46c where the surface pressure of the cam cap 38 is most applied.

Further, the thickness d2 of the resin coating film 46a in the central portion 46c in the circumferential direction is formed so as not to exceed one third of the clearance C in the range of minus 50 degrees Celsius to 150 degrees Celsius.
By configuring in this way, even when the clearance C becomes the smallest in the range of minus 50 degrees Celsius to 150 degrees Celsius, which is a general usable temperature range of an internal combustion engine such as an engine, the journal portion 36. And contact with the inner peripheral surface of the cam cap 38 can be avoided.

DESCRIPTION OF SYMBOLS 1 Valve train device 20 Cam shaft 30 Cam 34 Bearing member 36 Journal part 38 Cam cap 40 Bearing base part 46a Resin coating film 46b Circumferential end part 46c Circumferential center part

Claims (2)

In a bearing member of a valve operating apparatus comprising a camshaft having a cam for opening and closing at least one of an intake valve and an exhaust valve, and a plurality of journal portions,
The bearing member includes a cam cap that is supported from above so as to surround a journal portion of the camshaft, and a bearing base that is supported from below.
A valve operating device characterized in that an inner peripheral surface facing the journal portion of the cam cap is covered with a resin coating film, and both end portions in the circumferential direction of the resin coating film are formed thinner than a central portion in the circumferential direction. Bearing member.   The thickness of the resin coating film in the circumferential central portion is formed so as not to exceed one third of the clearance in the range of minus 50 degrees Celsius to 150 degrees Celsius. Bearing member of valve gear.

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