JP2005240715A - Camshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the weight of a camshaft without declining durability of the camshaft. <P>SOLUTION: This camshaft comprises a plurality of cam pieces having outer peripheral faces abutted on other members and a cam shaft connecting the plurality of cam pieces, and the cam pieces have cylindrical base parts and nose parts projecting from the base parts. Areas of opening side cam piece outer peripheral faces in a valve opening side in the nose parts are made larger than those of closing side cam piece outer peripheral faces in a valve closing side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a camshaft used for an internal combustion engine such as an automobile.

  As shown in FIGS. 5 and 6, the camshaft for the internal combustion engine includes a plurality of cam pieces 102 having a circumferential base portion 107 and a nose portion 103 protruding from the base portion 107, and a plurality of cam pieces. In general, the cam shaft 108 is connected to the cam shaft 108. The cam piece 102 has a substantially uniform width in the radial direction over the entire circumference, and the outer peripheral surface divided from the apex of the nose part 106 toward the base part 107 on the left and right sides is formed substantially the same.

In recent years, parts such as automobiles are required to be lighter, and camshafts are also required to be lighter. Here, in the cam piece 102, the load received from other members is higher in the nose portion 103 that opens and closes the valve than in the base portion 107. Therefore, as shown in FIGS. 7 and 8, in the cam piece 202, there is one in which the width of the base portion 207 that receives a low load from other members is narrower than the width of the nose portion 203.
Japanese Utility Model Publication No. 4-71704

  However, parts such as automobiles tend to be further reduced in weight. For this reason, it is conceivable to reduce the width in the radial direction of the cam piece over the entire circumference, but if the width of the nose portion in the cam piece is reduced in the same manner as the width of the base portion, the surface of the nose portion to which a higher load than the base portion is applied. It is conceivable that the pressure is increased and the required strength cannot be obtained, and the durability of the camshaft is lowered.

  The problem to be solved is that if the cam frame is formed to have a narrower width than the conventional width over the entire circumference in order to reduce the weight of the camshaft, the strength of the nose portion is insufficient and the durability is lowered. is there.

  The present invention comprises a plurality of cam pieces having an outer peripheral surface that comes into contact with another member, and a cam shaft that connects the plurality of cam pieces. The cam piece includes a circumferential base portion and a nose portion protruding from the base portion. In the camshaft having the first feature, the area of the outer peripheral surface of the opening side cam piece on the valve opening side in the nose portion is larger than the area of the outer peripheral surface of the closing side cam piece on the valve closing side.

  In addition to the first feature described above, the present invention provides the cam piece having a width between the outer peripheral surface of the open side cam piece and the outer peripheral surface of the closed side cam piece that decreases from the apex of the nose portion toward the base portion. A second feature is that the cam piece outer peripheral surface is located on the base portion side where the width is narrower than that of the closed cam piece outer peripheral surface.

  According to the camshaft of the first feature of the present invention, since the area of the outer peripheral surface of the opening side cam piece on the valve opening side is larger than the area of the outer peripheral surface of the closing side cam piece on the valve closing side, a high load is applied to the cam piece. When the valve is open, the load is received on the outer peripheral surface of the open cam piece, which has a large area. When the valve is closed, the load is smaller than that of the open side cam piece. Since it is received by the outer peripheral surface of the closing cam piece, the surface pressure of the outer peripheral surface of the cam piece is substantially constant over the entire circumference, and sufficient strength can be obtained without lowering the durability, and weight reduction can be achieved.

  Furthermore, according to the camshaft of the second feature of the present invention, the cam piece has a width between the outer peripheral surface of the opening-side cam piece and the outer peripheral surface of the closing-side cam piece that is narrowed from the apex of the nose portion toward the base portion, and is opened. Since the side cam piece outer peripheral surface is located on the base portion side where the width is narrower than that of the closed cam piece outer peripheral surface, the above structure can be easily realized.

  The purpose of reducing the weight of the camshaft was achieved without reducing the durability of the camshaft.

  FIG. 3 shows a direct acting valve operating apparatus for an internal combustion engine using a camshaft 1 according to an embodiment of the present invention. The valve stem 52 of the valve 51 is inserted into the valve guide 56, and a retainer 54 is fixed between the valve lifter 53 disposed above the valve stem 52 and the upper end of the valve stem 52. A valve spring 55 is wound around the valve stem 52 and is urged toward the valve lifter 53. The camshaft 1 is disposed at a position where the valve lifter 53 is pressed, and the cam piece 2 rotates when the camshaft 8 is driven.

  In the direct acting valve gear having the above-described structure, the valve stem 52 is urged toward the valve lifter 53 by the valve spring 55 when the valve 51 is closed. When the camshaft 8 of the camshaft 1 rotates and the cam piece 2 rotates in the direction of the arrow, the nose portion 3 of the cam piece 2 presses the valve lifter 53 to push down the valve stem 52, and the valve 51 as shown in FIG. It has a structure that opens.

  The operating state of the valve gear will be described in more detail. The cam piece 2 rotates in the direction of the arrow, and the open side cam piece outer peripheral surface 4 of the nose portion 3 first comes into contact with the valve lifter 53 and starts to push down the valve stem 52. As the cam piece 2 rotates, the valve stem 52 is further pushed down, and when the apex 6 of the nose portion 3 comes into contact with the valve lifter 53, the valve lift is maximized. When the closing cam piece outer peripheral surface 5 comes into contact with the valve lifter 53 beyond the apex 6 of the nose portion 3, the valve stem 52 starts moving in the direction of the valve lifter 53 and the valve 51 is closed.

  A camshaft 1 according to an embodiment of the present invention used in the valve operating apparatus as described above will be described with reference to FIGS. A camshaft 1 shown in FIG. 1 is formed concentrically with a plurality of cam pieces 2 including a circumferential base portion 7, a plurality of nose portions 3 protruding from the base portion 7, and the base portion 7 of the cam piece 2. The cam shaft 8 connects the plurality of cam pieces 2. The outer peripheral surface of the nose portion 3 of the cam piece 2 includes an open side cam piece outer peripheral surface 4 that contacts the valve lifter 53 when the valve 51 is opened, and a closed cam piece outer peripheral surface 5 that contacts the valve lifter 53 when the valve 51 is closed. It consists of. As shown in FIG. 2A, the opening-side cam piece outer peripheral surface 4 is formed with a uniform width from the apex 6, and the width is formed thicker than the base portion 7, and the closing-side cam piece outer peripheral surface 5 is As shown in FIG. 2A, the width is gradually reduced from the apex 6 toward the base portion 7. Further, the area of the outer peripheral face 4 of the open side cam piece is formed larger than that of the outer peripheral face 5 of the closed side cam piece.

  In the valve operating apparatus using the cam piece 2 as described above, the cam shaft 8 is driven to rotate the cam piece 2, and the open side cam piece outer peripheral surface 4 of the rotating cam piece 2 presses the valve lifter 53. The pressed valve lifter 53 further presses the retainer 54, the valve stem 52 and the valve spring 55 to open the valve 51. When the apex 6 of the nose portion 3 in the cam piece 2 presses the valve lifter 53, the valve lift amount is maximized, and at the same time, the reaction force generated by the valve spring 55 contracting is also maximized. A large load is applied. When the closed outer peripheral surface 5 of the cam piece 2 presses the valve lifter 53 beyond the apex 6 of the nose part 3 of the cam piece 2, the valve stem 52 starts moving toward the valve lifter 53, and the nose part of the cam piece 2 The load on 3 is gradually reduced.

  Therefore, according to the said Example, it consists of the cam piece 2 which has the outer peripheral surface contact | abutted with the valve lifter 53 which is another member, and the cam shaft 8 which connects the cam piece 2, and the cam piece 2 has the circumferential base part 7 and A camshaft having a nose portion 3 projecting from a base portion 7, wherein the opening side cam piece outer peripheral surface 4 on the valve opening side has a larger area than the closing side cam piece outer peripheral surface 5 on the valve closing side. When the valve 51 is subjected to a high load when the piece 2 is opened, the load is received by the outer cam surface 4 having a large area, and when the valve 51 is closed when the cam piece 2 is subjected to a lower load than when the valve 51 is opened, Since the load is received by the closed cam piece outer peripheral surface 5 having a smaller area than the open side cam piece outer peripheral surface 4, the surface pressure of the outer peripheral surface of the cam piece 2 is substantially constant over the entire circumference.

  In the above embodiment, the cam piece 2 has a width between the outer peripheral face 4 of the open side cam piece and the outer peripheral face 5 of the closed side cam piece that becomes narrower from the apex 6 of the nose part 3 toward the base part 7. Since the part outer peripheral surface 4 is located on the base 7 side where the width becomes narrower than the outer cam surface 5 on the closing side, the area of the outer cam surface 4 on the valve opening side is closed on the valve closing side. It can be formed larger than the area of the outer peripheral surface 5 of the side cam piece.

  In the above embodiment, the camshaft of the present invention is used in a direct acting valve gear, but the type of valve mechanism to be used is not limited.

It is a fragmentary sectional top view showing the camshaft by the Example of this invention. The side view of the camshaft of FIG. 1 is represented, (A) is A view, (A) is B view. It is a fragmentary sectional top view showing the state where the valve of the direct acting type valve gear using the camshaft by the example of the present invention was closed. It is a partial section top view showing the state where the valve of the direct acting type valve gear using the camshaft by the example of the present invention opened. It is a fragmentary sectional top view showing the conventional camshaft. It is a side view showing the camshaft of FIG. It is a fragmentary sectional top view showing the other conventional camshaft. It is a side view showing the camshaft of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cam shaft 2 Cam piece 3 Nose part 4 One outer peripheral surface 5 The other outer peripheral surface 6 Vertex 7 Base part 8 Cam shaft 53 Other members

Claims (2)

  It comprises a plurality of cam pieces (2) having an outer peripheral surface in contact with the other member (53), and a cam shaft (8) connecting the plurality of cam pieces (2). The cam piece (2) has a circumferential shape. In the camshaft having the base portion (7) and the nose portion (3) protruding from the base portion (7), the area of the outer peripheral surface (4) of the open-side cam piece on the valve opening side in the nose portion (3) Is larger than the area of the outer peripheral surface (5) of the closing cam piece on the valve closing side.   The cam piece (2) has a width between the opening side cam piece outer peripheral surface (4) and the closing side cam piece outer peripheral surface (5) from the apex (6) of the nose portion (3) to the base portion (7). The opening side cam piece outer peripheral surface (4) is narrower than the closing side cam piece outer peripheral surface (5), and the base part (7) side is located. 2. A camshaft according to claim 1 characterized in that:

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