JPH0129963B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for setting the mounting angle position of a camshaft in an internal combustion engine.

OHC is an OHC in which a timing belt or chain is attached to the sprocket attached to the engine crankshaft and the sprocket attached to the camshaft, and the rotational force of the crankshaft is transmitted to the camshaft via the timing belt or chain to rotate the camshaft. When installing a timing belt or chain on a type internal combustion engine, first install the crankshaft.
The number cylinder is fixedly held at the top dead center position, and the camshaft is fixedly held at a position corresponding to the crankshaft position, and then the parts of the timing belt or chain separated by a predetermined number of teeth are fixed to the crankshaft. A timing belt or chain is attached to the sprocket so that it meshes with the sprocket fixed to the sprocket and the camshaft, and then a predetermined tension is applied to the timing belt or chain by an idler, and then the idler is fixed to the engine body. There is. However, when parts of the timing belt or chain that are separated by a predetermined number of teeth are meshed with the sprocket fixed to the crankshaft and the sprocket fixed to the camshaft, variations in dimensions between the crankshaft and camshaft, as well as the timing belt itself or A problem arises in that the angular mounting position of the camshaft relative to the crankshaft deviates from the normal mounting angular position due to variations in the dimensions of the chain itself. For this reason, in the conventional system, there is a problem in that the angular position of the camshaft must be adjusted by measuring the valve timing for each engine after installing a timing belt or chain. Furthermore, conventionally, for example, after the timing belt is installed, the crankshaft is rotated in the normal rotation direction, and then, for example, an idler is pressed onto the portion of the timing belt extending from the sprocket of the crankshaft to the sprocket of the camshaft to apply tension to the timing belt. ing. However, since a large torque is required to rotate the camshaft, when the crankshaft rotates in the forward direction, the tension in the timing belt part on the pulling side from the camshaft sprocket to the crankshaft sprocket is transferred from the crankshaft sprocket to the camshaft. On the other hand, if the crankshaft is reversed even slightly at this time, the direction of rotation of the timing belt will be reversed, so the tension of the timing belt section on the sending side will be Conversely, the tension is greater than the tension in the timing belt portion on the tension side. In this way, the tension on each timing belt section varies greatly depending on how the crankshaft rotates, so even if you press the idler against one timing belt section with a constant force and then fix the idler in position, the idler will not be pressed. Since the tension in the timing belt part that is not the timing belt part varies, the initial tension applied to the entire timing belt varies, resulting in abnormal wear and noise on the timing belt, and furthermore, in the timing belt part. This results in so-called tooth skipping, where the teeth that should mesh with the belt and sprocket become misaligned.

The present invention provides a camshaft that can accurately set the mounting angle position of the camshaft relative to the crankshaft to the normal mounting angle position when installing a timing belt or chain, and that can also apply uniform initial tension to the entire timing belt or chain. The object of the present invention is to provide a mounting angle position setting method.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to Fig. 1, 1 is the engine body, 2 is the crankshaft, 3 is a sprocket fixed to the crankshaft 2, 4 is a sprocket for rotating auxiliary equipment such as an oil pump, and 5 is for example for driving an intake valve. A sprocket attached to the camshaft, 6 a sprocket attached to the exhaust valve driving camshaft, 8 an arm rotatably attached to the engine body 1 via a pivot 9, and 10 rotatably attached to the arm 8. idler, 1
1 indicates a timing belt. Note that a chain may be used instead of the timing belt 11. Referring to FIG. 2, a camshaft 12 with a sprocket 5 mounted thereon is shown.
Note that the sprocket 6 and the camshaft (not shown) to which the sprocket 6 is attached have the same structure as shown in FIG.
A description of the camshaft to which the sprocket 6 is attached will be omitted. Referring to Figure 2,
The camshaft 12 is integrally formed with a cam nose 13 and large-diameter bearings 14 and 15, and the large-diameter bearings 14 and 15 are fixed to the engine body 1 with bearings 16 and 15, respectively.
17 respectively. Further, an oil seal 18 is provided within the bearing 16. A camshaft end surface 19 projecting outward from the bearing 16 is formed into a flat surface, and a hollow cylindrical projection 20 is integrally formed coaxially with the camshaft 12 on this flat end surface 19 . Inside this hollow cylindrical projection 20, there is a screw hole 21 extending in the axial direction of the camshaft 12.
A sprocket 5 is rotatably fitted onto the outer peripheral wall surface of the hollow cylindrical projection 20.
As shown in Figures 2 and 4, the camshaft 1
A plurality of circular holes 22a, 22b, 22 extending in the axial direction of the camshaft 12 are provided on the flat end surface 19 of the camshaft 12.
These circular holes 22a, 22b, 22c, 2 are bored as shown in FIG.
2d and 22e are arranged at equal angular intervals θ with respect to the rotational axis of the camshaft 12. On the other hand, as shown in FIGS. 2 and 5, there are also circular holes 22a, 22b, 22c, 22 on the sprocket 5.
A plurality of through holes 23 that can be aligned with d and 22e.
a, 23b, 23c, 23d, and 23e are drilled, and as shown in FIG.
a, 23b, 23c, 23d, and 23e are spaced at equal angular intervals θ+δ with respect to the rotational axis of the sprocket 5.
are placed apart from each other. Note that δ is an extremely small angle compared to θ. On the other hand, as shown in FIG. 2, a through hole 24 is bored on the bearing 17, and a circular hole 25 that can be aligned with the through hole 24 is also formed on the outer peripheral wall surface of the large diameter bearing portion 15 of the camshaft 12. drilled. This circular hole 25 is inserted into the penetrating circular hole 24 when the camshaft 12 is at a position corresponding to a specific position of the crankshaft 2 (for example, the compression top dead center of the No. 1 cylinder).
It is arranged so that it is aligned with. In addition, in Fig. 1, there is a top dead center mark (not shown) on the crankshaft 2 that indicates that the No. 1 cylinder is at the top dead center position.
is depicted.

Next, a method for setting the mounting angle position of the camshaft according to the present invention will be described with reference to FIGS. 1 to 5. First, the crankshaft 2 is fixedly held at the top dead center position of the No. 1 cylinder by the top dead center mark drawn on the crankshaft 2. At this time, the idler 10 is rotated in the direction indicated by arrow A in FIG. Next, the circular hole 25 formed in the large-diameter bearing portion 15 of the intake valve driving camshaft 12 and the through-hole 24 of the bearing 17 are aligned, and a lock pin 26 (see FIG. 2) is inserted into the aligned circular holes 24 and 25. Insert. Therefore, at this time, the camshaft 12 is held non-rotatably by the lock pin 26. The same thing is done for the camshaft for driving the exhaust valve. Next, the sprocket 5 is fitted onto the hollow cylindrical projection 20 of the camshaft 12, and the central through hole 23c of the sprocket 5 is aligned with the central circular hole 22c formed on the camshaft end surface 19. On the other hand, the same thing is done for the sprocket 6 as well. Next, the timing belt 11 is attached to each sprocket 3, 4, 5,
Attach it around 6. Next, as shown in FIG. 1, one end of the tension spring 28 is latched to the protruding latching portion 27 of the arm 8, and the other end 29 of the tension spring 28 is latched to the engine body 1. In addition, the tension spring 28
may be attached in advance, and the idler 10 may be moved in the direction A and temporarily fixed before the timing belt 11 is attached. When the other end 29 of the tension spring 28 is latched to the engine body 1 as described above, the idler 10 rotates around the pivot 9 in the direction opposite to the arrow A direction due to the spring force of the tension spring 28, thereby tightening the timing belt 11. Pressure is applied to the timing belt 11 to apply tension. Furthermore, at this time, sprocket 3 does not rotate because it is fixed to crankshaft 2, but sprockets 5 and 6 rotate freely because they are rotatably mounted on the corresponding camshaft 12, and sprocket 4 is also light. Since it is connected to the load auxiliary equipment, it rotates relatively freely. As a result, a uniform tension determined by the spring force of the tension spring 28 is applied to the timing belt 11 over its entire length. Then arm 8
is unrotatably fixed to the engine body 1, and the tension spring 28 is removed. Note that this tension spring 28
You can leave it attached. As mentioned above, the sprockets 5 and 6 have through-holes 2 in their centers.
3c is installed on the camshaft 12 so that it is aligned with the central circular hole 22c of the camshaft 12.
When tension is applied to the timing belt 11, the timing belt 11 is pulled, causing the sprockets 5 and 6 to rotate slightly as described above. Therefore, at this time, for example, if the sprocket 5 is rotated counterclockwise by 2.delta., the through hole 23a of the sprocket 5 and the circular hole 22a of the camshaft 12 will be aligned. Next, a dowel pin 30 (FIG. 2) is fitted into the circular holes 23a and 22a that are aligned with each other, and then the sprocket 5 is tightened with a bolt 32 through a washer 31.
is fixed to the camshaft 12. Next, the lock pin 26 inserted into the circular hole 25 of the large diameter bearing portion 15 of the camshaft 12 is pulled out. Next, do the same thing for sprocket 6. Incidentally, if the mounting resistance of the camshaft 12 is large and therefore the camshaft 12 does not easily become misaligned, the lock pin 26 may be pulled out before the dowel pin 30 is fitted. As mentioned above, the crankshaft 2 is held fixed at the top dead center position of the No. 1 cylinder, for example, and the camshaft 12 is also held fixed at the corresponding compression top dead center position of the No. 1 cylinder. is accurately set at the normal mounting angle position with respect to the crankshaft 2.

As described above, according to the present invention, even if the dimensions between the crankshaft and the camshaft vary, or even if the dimensions of the timing belt itself vary, the camshaft's mounting angle position can be adjusted to the normal mounting angle with respect to the crankshaft. Can be set precisely in position. In addition, when tension is applied to the timing belt by the idler, it is possible to apply uniform tension over the entire length of the timing belt, so it is possible to apply a predetermined initial tension to the timing belt, thereby preventing abnormalities. Not only can it prevent the occurrence of excessive wear and noise, but also the occurrence of tooth skipping.

[Brief explanation of drawings]

Figure 1 is a front view of the engine body, Figure 2 is a side sectional view taken along the - line in Figure 1, and Figure 3 is a front view of the engine body.
FIG. 4 is a front view of the end face of the camshaft, and FIG. 5 is a front view of the sprocket. 2...Crankshaft, 3, 4, 5, 6...
Sprocket, 10... Idler, 11... Timing belt, 12... Camshaft, 22a,
22b, 22c, 22d, 22e, 25... circular hole, 23a, 23b, 23c, 23d, 23e,
24...Through circular hole, 26...Lock pin, 30...
...Notsukupin.

Claims (1)

[Claims] 1. The crankshaft of the engine is fixed and held at a predetermined crank angle position, the camshaft is fixed and held at a regular angular position corresponding to the crank angle position, and then the sprocket fixed to the crankshaft and the camshaft are rotated. A timing belt or chain is attached to the attached sprocket, and then a predetermined tension is applied to the timing belt or chain by an idler, and then the idler is rotatably fixed to the engine body, and then attached to the camshaft. A method for setting a camshaft mounting angle position for an internal combustion engine, in which the sprocket is fixed to the camshaft.