JP2015163805A - Assembled camshaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an assembled camshaft 10 which can rigidly join a cam piece 14 to a shaft 12.SOLUTION: A cam piece 14 partitions an insertion hole of a shaft 12 by internal peripheral faces 14b, 14c. The internal peripheral face 14b is formed so that a diameter of the insertion hole becomes large as progressing toward the outside of the insertion hole. A ring-shaped member 16 is inserted between the shaft 12 and the internal peripheral face 14b. A male screw part 14d is formed at a side of an external peripheral face corresponding to the internal peripheral face 14b. Then, a bearing nut 18 is fastened to the male screw part 14d. The bearing nut 18 contacts with an end part of the ring-shaped member 16, and the ring-shaped member 16 is pushed to the internal peripheral face 14c side by the fastening of the bearing nut 18 to the cam piece 14. As the bearing nut 18 is fastened to the cam piece 14, a joining force between the shaft 12 and the cam piece 14 is increased.

Description

  The present invention relates to an assembled camshaft in which a cam piece is assembled to a shaft.

  In recent years, cam pieces and shafts for driving valves of in-vehicle internal combustion engines have been replaced by assembled cam shafts that are separate from the cam piece and shaft that are integrally formed for the purpose of reducing weight and increasing cam strength. . As a method for assembling the cam piece to the shaft, a method for press-fitting the cam piece into the shaft, a shrink fitting for fitting a high-temperature cam piece into the shaft, and the like have been put into practical use.

  However, in any of the above methods, the clearance between the inner peripheral surface of the cam piece that defines the insertion hole of the shaft and the outer periphery of the cam piece is a parameter that determines the bonding force between the cam piece and the shaft. Is required.

  Therefore, conventionally, as seen in Patent Document 1, for example, it has been proposed to provide a screw hole in the shaft and the cam piece and fix the shaft and the cam piece with screws (FIG. 4 and the like).

Japanese Utility Model Publication No. 6-82455

  However, as described above, when screwing the shaft and the cam piece, the inner peripheral surface of the cam piece on the side farthest away from the screw insertion side of the insertion hole is not likely to contact the shaft. There is a possibility that the joining force of the cam piece to the shaft is insufficient.

  This invention is made | formed in view of such a situation, The objective is to provide the assembly cam shaft which can join a cam piece firmly to a shaft.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
Technical idea 1: In an assembled cam shaft in which a cam piece is assembled to a shaft, an insertion hole into which the shaft is inserted is formed in the cam piece, and an inner peripheral surface defining the insertion hole is inserted into the cam piece. A portion extending in the axial direction of the hole, including a male screw portion having a thread groove formed on an outer peripheral surface thereof, and the insertion hole is formed such that the diameter increases toward the outer side in the axial direction of the insertion hole. A ring-shaped member that is inserted into the inner peripheral surface of the insertion hole and becomes thicker toward the outer side in the axial direction of the insertion hole, and a female screw corresponding to the male screw portion, The screw contacts an end portion on the thick side of the ring-shaped member, and the end portion on the thick side is displaced inward in the axial direction of the insertion hole as it is tightened to the male screw portion. Assembled camshaft.

  By tightening the female screw to the male screw portion, the end on the thick side of the ring-shaped member is displaced inward in the axial direction of the insertion hole. As a result, a force is applied from the ring-shaped member to the inner peripheral surface of the cam piece in which the insertion hole is formed, perpendicularly to the inner peripheral surface, and the distance between the inner peripheral surface and the outer peripheral surface of the shaft is increased. . Therefore, the cam piece exerts a force on the shaft perpendicular to the outer peripheral surface via the ring-shaped member. For this reason, since a large force is applied to the shaft and the cam piece in the radial direction, the shaft and the cam piece can be firmly joined.

Sectional drawing which shows the structure of the assembly camshaft concerning 1st Embodiment. Sectional drawing which shows the relationship between the aperture diameter of the cam piece insertion hole in the same embodiment, and the diameter of the outer periphery of a shaft. The perspective view which shows the bearing nut concerning the embodiment. (A)-(g) is a figure which shows the assembly | attachment process of the cam piece concerning the embodiment. The figure which shows the material concerning the embodiment. (A)-(g) is a figure which shows the assembly | attachment process of the cam piece concerning 2nd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment of an assembly camshaft will be described with reference to the drawings.
FIG. 1 shows a partial cross-sectional view of the assembled camshaft 10. In the illustrated assembly camshaft 10, a cam piece 14 for driving an intake valve and an exhaust valve (engine valve) of an in-vehicle internal combustion engine (not shown) is assembled to a hollow cylindrical shaft 12. Here, the inside of the shaft 12 serves as a flow path for the lubricating oil. On the other hand, when the cam piece 14a or its peripheral part comes into contact with a member that opens and closes the engine valve, the cam piece 14 opens the engine valve, and the cam nose 14a or its peripheral part does not come into contact with a member that opens and closes the engine valve. Then, close the engine valve.

  Inner peripheral surfaces 14 b and 14 c that define an insertion hole of the shaft 12 are formed in the cam piece 14. The diameter of the insertion hole defined by the inner peripheral surfaces 14 b and 14 c is larger than the diameter of the outer peripheral surface of the shaft 12.

FIG. 2 shows that the diameter of the insertion hole defined by the inner peripheral surface 14 c is larger than the diameter of the outer peripheral surface of the shaft 12.
The inner peripheral surface 14c is a surface located at the center of the insertion hole, and the diameter of the insertion hole defined by the inner peripheral surface 14c is constant. On the other hand, the inner peripheral surface 14b is located on both sides of the inner peripheral surface 14c, and the diameter of the insertion hole defined by the inner peripheral surface 14b increases toward the outside of the insertion hole.

  A ring-shaped member 16 is inserted between the cam piece 14 and the shaft 12. Specifically, a pair of ring-shaped members 16 are provided for one cam piece 14, and one of the pair of ring-shaped members 16 is inserted from one of the cam pieces 14 on both sides of the insertion hole. The other is inserted from the other side of the insertion hole.

  The ring-shaped member 16 is a hollow member having a cylindrical inner peripheral surface. Moreover, the ring-shaped member 16 is provided with the taper part 16a in the outer peripheral surface by becoming thick so that it may displace from one to the other of an axial direction. Specifically, for example, in the drawing, the thickness of the taper portion 16a of the right ring-shaped member 16 increases as it goes to the right in the axial direction of the insertion hole (outside the insertion hole).

  The rate of change of the thickness of the tapered portion 16a of the ring-shaped member 16 with respect to the displacement of the insertion hole in the axial direction (the direction parallel to the straight line L1 in the figure) It is set equal to the changing speed of the aperture with respect to the axial displacement of the insertion hole. In FIG. 1, the pair of change speeds are quantitatively expressed as an angle θ formed by the straight line L2 with respect to the straight line L1. This is a setting for bringing the tapered portion 16a and the inner peripheral surface 14b into surface contact.

  The portion of the cam piece 14 where the inner peripheral surface 14b is formed is a portion extending on both sides of the insertion hole with respect to the portion where the cam nose 14a is formed. And the external thread part 14d is formed in the outer peripheral surface of this part. The female screw portion 18a of the bearing nut 18 is fastened to the male screw portion 14d.

  As shown in FIG. 3, the bearing nut 18 is a hollow ring-shaped member. Moreover, the bearing nut 18 is provided with the internal thread part 18a and the thick part 18b, as shown in FIG. The thick part 18 b of the bearing nut 18 contacts the end of the ring-shaped member 16. For this reason, as the bearing nut 18 is tightened to the male screw portion 14d, the ring-shaped member 16 is more strongly pressed toward the inner peripheral surface 14c. And the space | interval between the internal peripheral surfaces 14b and 14c of the cam piece 14 and the outer peripheral surface of the shaft 12 becomes large, so that the ring-shaped member 16 is displaced to the internal peripheral surface 14c side. As a result, the cam piece 14 and the shaft 12 exert a force in the radial direction of the insertion hole via the ring-shaped member 16, and a joining force between the cam piece 14 and the shaft 12 is generated. Further, since the male screw portion 14d is pressed against the female screw portion 18a, the male screw portion 14d bites into the female screw portion 18a, and the joining force increases.

Next, the process of assembling the cam piece 14 to the shaft 12 will be described with reference to FIG.
In this series of steps, first, as shown in FIG. 4A, the shaft 12 to be inserted into the cam piece 14 is processed. Specifically, after turning the outer shape of the shaft 12, it is ready to be inserted into the cam piece 14 by grinding. Next, as shown in FIG. 4B, one of the bearing nuts 18 fitted on both sides of the cam piece 14 is inserted into the shaft 12. 4 shows a side view of the shaft 12, but the bearing nut 18 is a cross-sectional view similar to FIG. Next, as shown in FIG. 4C, the shaft 12 is inserted into one of the ring-shaped members 16 inserted on both sides of the cam piece 14. In addition, the ring-shaped member 16 has shown the side view. Then, as shown in FIG. 4 (d), the shaft 12 is inserted into the cam piece 14, the ring-shaped member 16 into which the shaft 12 has already been inserted is inserted into the cam piece 14, and a bearing nut 18 is fastened to the cam piece 14. In FIG. 4, the cam piece 14 shows a cross-sectional view similar to FIG. Incidentally, in FIGS. 4C and 4D, the position of the bearing nut 18 is schematically fixed and described, but the process of fastening the bearing nut 18 to the cam piece 14 is performed by You may implement | achieve by displacing to the cam piece 14 side, rotating.

  When one bearing nut 18 is fastened to the cam piece 14, the ring-shaped member 16 is still inserted in the cam piece 14 by inserting the shaft 12 into the other ring-shaped member 16 as shown in FIG. The other ring-shaped member 16 is inserted into the non-side. Subsequently, as shown in FIG. 4 (f), the shaft 12 is inserted into the other bearing nut 18, and on the side of the cam piece 14 where the ring-shaped member 16 is inserted in the step shown in FIG. 4 (e). The other bearing nut 18 is fastened. Then, as shown in FIG. 4G, the force described as the force F is applied to the bearing nuts 18 on both sides of the cam piece 14 and tightened. Here, the rotation direction for tightening is reversed between the bearing nut 18 on one side of the both sides of the cam piece 14 and the bearing nut 18 on the other side. This is realized by having the bearing nut 18 on one side and the bearing nut 18 on the other side have the same structure, and the structure of the pair of male screw portions 14d of the cam piece 14 is both a right screw or a left screw. Can do.

  As shown in FIG. 5, the series of steps shown in FIG. 4 is performed at normal temperature (10 to 30 ° C. is exemplified). As shown in FIG. 5, as the bearing nut 18, an invar that is a member having a low coefficient of thermal expansion, an alumina ceramic material, or the like is used. On the other hand, as the cam piece 14, a steel material or the like having a larger coefficient of thermal expansion than the bearing nut 18 is used. The ring-shaped member 16 is made of iron, steel, brass, aluminum, or the like that has a higher coefficient of thermal expansion than the bearing nut 18.

  This is a setting for avoiding a situation where the joining force of the cam piece 14 to the shaft 12 is insufficient due to a temperature change. That is, the lubricating oil circulating inside the shaft 12 and the lubricating oil sprayed on the cam piece 14 circulate in the cylinder head of the internal combustion engine, and thus become high temperature. For this reason, it is desirable that the joining force between the cam piece 14 and the shaft 12 is set so as not to be insufficient at a high temperature close to 100 ° C. Here, if the bearing nut 18 or the like expands due to a temperature higher than that in the assembly process, the joining force may be reduced.

  Therefore, in this embodiment, a material having a smaller thermal expansion coefficient than the raw material of the cam piece 14 having the male screw portion 14d is selected as the raw material of the bearing nut 18 having the female screw portion 18a. Accordingly, when the temperature is higher than that in the assembly process, the extension amount of the diameter of the male screw portion 14d is larger than the extension amount of the diameter of the female screw portion 18a. The degree of biting increases and the bonding force increases.

  When the vehicle is placed at an extremely low temperature (for example, about “−30 °”), the contraction amount of the diameter of the male screw portion 14d is larger than the contraction amount of the diameter of the female screw portion 18a. The joining force between the shaft 12 and the shaft 12 is lower than that during assembly. For this reason, it is desirable that the bearing nut 18 is fastened to the cam piece 14 so as to satisfy the joining force required at the assumed minimum temperature in anticipation of a reduction in joining force at low temperatures.

  As described above, in the present embodiment, by tightening the bearing nut 18 to the cam piece 14, the ring-shaped member 16 is displaced toward the inner peripheral surface 14 c, and the male screw portion 14 d of the cam piece 14 is the female screw of the bearing nut 18. Pressed against the portion 18a increases the bonding force.

According to the present embodiment described above, the following effects can be obtained.
(1) The cam piece 14 was assembled to the shaft 12 using the ring-shaped member 16 and the bearing nut 18. For this reason, the cam piece 14 and the shaft 12 can be firmly joined by fastening the bearing nut 18 to the cam piece 14.

  (2) The cam piece 14 was assembled to the shaft 12 using the ring-shaped member 16 and the bearing nut 18. For this reason, since the joining force between the cam piece 14 and the shaft 12 is determined by the tightening force between the cam piece 14 and the bearing nut 18, the cam piece 14 is attached to the shaft 12 with respect to the diameter of the insertion hole of the cam piece 14 and the diameter of the shaft 12. High accuracy is not required as compared with shrink fitting. For this reason, the cam piece 14 and the shaft 12 can be easily processed.

  (3) The speed of change of the diameter of the insertion hole defined by the inner peripheral surface 14b of the cam piece 14 with the displacement of the insertion hole in the axial direction, and the diameter of the tapered portion 16a of the ring-shaped member 16 is the axis of the insertion hole. The speed of change with displacement in the direction was made equal. Thereby, the inner peripheral surface 14b and the taper part 16a can fully surface-contact.

  (4) In the method of inserting the cam piece 14 into the shaft 12 in a state where the diameter of the insertion hole of the cam piece 14 is larger than the diameter of the outer periphery of the shaft 12, the ring-shaped member 16 is used so that the center of the insertion hole of the cam piece 14 A situation in which the shaft and the central axis of the shaft 12 are displaced can be suitably suppressed.

  (5) As the raw material for the bearing nut 18, a material having a smaller coefficient of thermal expansion than the raw material for the cam piece 14 was selected. Thereby, when the bearing nut 18 and the cam piece 14 become high temperature, the joining force between the cam piece 14 and the shaft 12 can be rather increased.

  (6) The tightening force of the cam piece 14 to the bearing nut 18 was set to a value at which the joining force between the cam piece 14 and the shaft 12 was not insufficient in an extremely low temperature state. As a result, it is possible to suppress a situation where the joining force between the cam piece 14 and the shaft 12 is insufficient in an extremely low temperature state while the cam piece 14 is assembled to the shaft 12 at room temperature.

<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  When the ring-shaped member 16 is inserted from both sides of the cam piece 14 and the bearing nut 18 is tightened as in the first embodiment, the interval between the bearing nuts 18 on both sides of the cam piece 14 tends to increase. On the other hand, a plurality of intake valves (exhaust valves) of an internal combustion engine may be provided in each cylinder. In this case, there is a concern that it may be difficult to satisfy the position of the pair of cam lobes determined in accordance with the interval between the intake valves (exhaust valves) provided adjacent to the same cylinder.

Therefore, in this embodiment, cam lobes for driving a pair of intake valves (exhaust valves) are formed in one cam piece 14, and both sides thereof are tightened with bearing nuts 18.
FIG. 6 shows a process of assembling the cam piece 14 to the shaft 12 according to the present embodiment. 6A to 6G correspond to FIGS. 4A to 4G, respectively.

  As shown in FIG. 6 (d), in this embodiment, the shaft 12 is inserted into the cam piece 14 in which two cam lobes (in the figure, the cam nose 14a of the cam lobes is indicated with a reference numeral). Then, as shown in FIG. 6 (g), the bearing nut 18 is tightened from both sides of the cam piece 14.

According to this embodiment described above, in addition to the effects (1) to (6) of the first embodiment, the following effects are further obtained.
(7) A pair of cam lobes were formed on the single cam piece 14. Thereby, even when the cam piece 14 is joined to the shaft 12 by the ring-shaped member 16 and the bearing nut 18, it is easy to reduce the interval between the pair of cam lobes.

<Other embodiments>
Each of the above embodiments may be modified as follows.
In the above embodiment, the rate of change with respect to the change in the axial direction of the diameter of the insertion hole defined by the inner peripheral surface 14b is equal to the rate of change with respect to the change in the axial direction of the diameter of the tapered portion 16a. Absent. For example, the changing speed with respect to the change in the axial direction of the diameter of the insertion hole defined by the inner peripheral surface 14b may be slightly larger than the changing speed with respect to the change in the axial direction of the diameter of the tapered portion 16a. Even in this case, it is considered that the inner peripheral surface 14b of the male screw portion 14d and the tapered portion 16a of the ring-shaped member 16 come into surface contact with each other by increasing the force for tightening the bearing nut 18. However, the setting in which the inner peripheral surface 14b of the male screw portion 14d and the tapered portion 16a of the ring-shaped member 16 are in surface contact is not essential.

  In the above embodiment, the assembly temperature is set to room temperature, but is not limited thereto. For example, when the temperature is lower than room temperature, the bearing nut 18 is tightened so that the joining force between the cam piece 14 and the shaft 12 is equal to or higher than the required lower limit during assembly. It is also possible to always satisfy. Further, for example, a material having a smaller coefficient of thermal expansion than the material of the ring-shaped member 16 or the cam piece 14 may be used as the material of the shaft 12. In this case, when the temperature is lower than normal temperature, the amount of contraction of the cam piece 14 is larger than the amount of contraction of the shaft 12, so that the force exerted on the shaft 12 and the cam piece 14 in the radial direction can be increased. As a result, it is possible to compensate for a decrease in the fastening force between the male screw portion 14d and the bearing nut 18 due to temperature.

  -It is not restricted to what the bearing nut 18 is provided in the both sides of the cam piece 14. FIG. For example, in a configuration in which a stopper is provided at the end of the shaft 12, when the cam piece 14 is assembled so that one side is fixed by the stopper, the bearing nut 18 may be provided only on the side opposite to the stopper.

The internal thread is not limited to the bearing nut 18, but may be any structure as long as the force that pushes the ring-shaped member 16 is increased as the external thread is tightened to the external thread 14 d.
-The shaft 12 is not limited to a hollow one. Further, the material of the cam piece 14, the bearing nut 18, and the ring-shaped member 16 is not limited to those illustrated in FIG.

  DESCRIPTION OF SYMBOLS 10 ... Cam shaft, 12 ... Shaft, 14 ... Cam piece, 14a ... Cam nose, 14b ... Inner peripheral surface, 14c ... Inner peripheral surface, 14d ... Male screw part, 16 ... Ring-shaped member, 16a ... Taper part, 18 ... Bearing nut , 18a ... female screw part, 18b ... thick part.

Claims (1)

In the assembled camshaft where the cam piece is assembled to the shaft,
The cam piece has an insertion hole into which the shaft is inserted,
The cam piece includes a male screw portion having an inner peripheral surface defining the insertion hole extending in the axial direction of the insertion hole and having a thread groove formed on the outer peripheral surface thereof.
The insertion hole is formed such that the diameter increases toward the outside in the axial direction of the insertion hole,
A ring-shaped member that is inserted into the inner peripheral surface of the insertion hole and becomes thicker toward the outside in the axial direction of the insertion hole;
A female screw corresponding to the male screw part,
The female screw comes into contact with the end portion on the thick side of the ring-shaped member, and the end portion on the thick side is displaced inward in the axial direction of the insertion hole as it is tightened to the male screw portion. Features an assembled camshaft.