JPS6246948Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a backlash adjustment mechanism in a camshaft drive system of a four-stroke engine.

As one of the camshaft drive mechanisms for a four-stroke engine, a method of transmitting the rotation of the crankshaft to the camshaft using only gears is well known. This camshaft drive mechanism is
Crankshaft and camshaft tooth ratio 1/
Two gears are provided, and idle gears of a predetermined number and diameter are interposed between the gears.

In an engine that utilizes a camshaft drive mechanism consisting only of such gears, particularly in an engine that has two camshafts, the idle gear meshes simultaneously with the camshaft gears provided on each of the pair of camshafts. Since both the camshaft gear and the idle gear rotate at high speed, extremely strict conditions are imposed on the size of the backlash between the camshaft gear and the idle gear. When meshing with a shaft gear simultaneously, it is extremely difficult to set the backlash between each gear to an optimum value. In order to solve this problem, a so-called eccentric shaft is used for the support shaft of the idle gear, in other words, the rotation center of the idle gear is eccentric to the center of the support shaft, and when the idle gear is installed, the idle gear and the two BACKGROUND OF THE INVENTION BACKGROUND OF THE INVENTION A backlash adjustment mechanism that attempts to adjust the backlash between camshaft gears has been proposed and used. However, in this type of buckrush adjustment mechanism, the locus of the rotation center of the idle gear during the bucklash adjustment draws a small arc with the radius of the eccentric distance described above, so a considerable amount of skill is required for the buckrush adjustment work, and there are three The degree of backlash adjustment between the gears could not be expected to be sufficient.

The present invention has been made in view of the above points, and its purpose is to provide a bump crush adjustment mechanism that can easily adjust the bump bump between an idle gear and a pair of camshaft gears.

The backlash adjustment mechanism according to the present invention swings an idle gear that is swingably supported in a direction substantially perpendicular to the rotation axis of two camshafts in an engine and that simultaneously meshes with camshaft gears provided on each of the camshafts. An arm member pivotally supported at a predetermined position between a center point and a swinging end, and adjustment and fixing means for adjusting a swinging angle of the arm member and fixing the arm member at a desired angular position. It is characterized by

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an engine equipped with a crush adjustment mechanism according to the present invention will be described with reference to the accompanying drawings.

The illustrated engine is a double overhead camshaft type V-type single cylinder engine used in a motorcycle.

As shown in the figure, a cylinder 2 and a cylinder head 3 are each fixed to the upper part of a crankcase 1 by stud bolts (not shown) or the like. Cylinder 2 has a single piston (not shown)
is inserted therein, and is connected to the crankshaft 5 via a connecting rod (not shown). The crankshaft 5 is connected to a transmission 6 provided at the rear of the crankcase 1 via a clutch device (not shown), and to a starter motor 7 provided at the side of the crankcase 1.
are respectively connected to the output shafts of the motors via a plurality of gears 8. An exhaust side camshaft 10 and an intake side camshaft 11 are pivotally supported between the cylinder 2 and the cylinder head 3, respectively, for driving an exhaust valve and an intake valve, respectively. Camshaft gears 12 and 13 are fixed to one end of each of the exhaust side camshaft 10 and the intake side camshaft 11, respectively.
Both of these camshaft gears are designed to interlock with a crankshaft gear 16 fixedly attached to the crankshaft 5 via two idle gears 14 and 15. Idle gear 14 located above
is formed to have a slightly larger outer diameter than the idle gear 15 disposed below, and meshes with both camshaft gears 12 and 13 at the same time.

Here, a method for supporting the idle gear 14 will be explained.

As is particularly clear in FIG. 3, a plate-shaped holder A17 with both ends cut into semicircular shapes is fixed to the inner surface of the side wall of the cylinder 2. An arm member 18 is attached to this holder A17 at one end thereof through a rivet 19a and a washer 19b, and two
The camshafts 10 and 11 are supported so as to be swingable in a direction substantially perpendicular to their rotation axes. The arm member 18 has a shaft portion 18a extending inward of the engine at a predetermined position between its swing center point and swing end.
is provided protrudingly, and the idle gear 14 is pivotally supported on this shaft portion 18a via a ball bearing 20. An arm member 18 is provided at the tip of the shaft portion 18a.
A substantially circular holder B18b forming a part of the idler gear 14 is fixed thereto, and movement of the idle gear 14 in the side direction is restricted by the holder B and via a spacer 18c. Further, another spacer 18d having the same function as the spacer 18c is arranged at the root portion of the shaft portion 18a.

On the other hand, the other end of the arm member 18 is fixed to the plate-like member 17 and therefore to the cylinder 2 by an eccentric shaft 22 and a nut 23 that is screwed into the threaded portion of the eccentric shaft. There is. These eccentric shaft 22 and nut 23 constitute adjustment and fixing means for adjusting the swing angle of the arm member 18 and fixing the arm member at a desired angular position. The eccentric shaft 22 has a small diameter part 22a with the threaded part, a large diameter part 22b formed so that its center axis coincides with the center axis of the small diameter part 22a, and a space between the small diameter part 22a and the large diameter part 22b. It is composed of an eccentric part 22c located at , and whose central axis is offset by e from the central axes of the small diameter part and the large diameter part. The other end of the arm member 18 is fixedly supported by the eccentric portion 22c of the eccentric shaft 22 engaging with a long hole 18e formed in the other end. Note that a groove is formed at the tip of the small diameter portion 22a, into which a driver of a predetermined size can be engaged (see FIG. 3).

Next, a case will be described in which the backlash between the camshaft gears 12 and 13 and the idle gear 14 is adjusted in the engine configured as described above.

First, when the nut 23 is loosened from the outside of the engine using a specified tool, the arm member 18 is attached to the rivet 1.
It can swing freely around 9a. Next, a driver is applied to a driver engagement groove provided at the tip of the small diameter portion 22a of the eccentric shaft 22, and the eccentric shaft is rotated, for example, clockwise in FIG. 4 by a predetermined angle. Then, the shaft portion 18a of the arm member 18, and hence the idle gear 14, swings very slightly in a large arc centered on the rivet 19a. In this way, the eccentric shaft 22
By rotating the camshaft gears 12 and 13, the idle gear 14 moves away from or approaches the camshaft gears 12 and 13 almost linearly along a large radius of curvature. This makes it easier to adjust the backlash. Further, the shaft portion 18a of the arm member 18
It goes without saying that by increasing or decreasing the distance between the shafts and the rivet 19a, it is possible to appropriately determine the ratio of the moving distance of the idle gear 14 to the rotation angle of the eccentric shaft 22.

After confirming by a predetermined measuring means that the backlash between both camshaft gears 12 and 13 and the idle gear 14 is set to the optimum value, the nut 23 is tightened to fix the arm member 18. In this way, the batch adjustment is completed.

In the above embodiment, the arm member 18 is the holder A.
Although a case is shown in which the arm member 18 is fixed to the cylinder 2 via the holder A, it is not necessarily necessary to use the holder A, and the arm member 18 can also be attached directly to the cylinder 2. However, by attaching the arm member 18 to the cylinder 2 via a member such as the holder A17, the number of man-hours such as drilling a hole in the cylinder 2 is reduced.

In addition, although this embodiment shows the case where the present invention is applied to a double overhead camshaft type V-type single cylinder engine, the present invention is not limited to this type of engine, but can also be applied to other types of engines. Applicable.

As described in detail above, in the buckle bump adjustment mechanism for the camshaft drive system according to the present invention, buckle bump adjustment between the idle gear that meshes with a pair of camshaft gears at the same time and both of the camshaft gears allows the idle gear to This is achieved by a minute angular displacement of the arm member pivotally supported between the pivot center point and the pivot end. Therefore, fine adjustment of the backlash is possible, and since the locus of the center of rotation of the idle gear during the backlash adjustment is approximately a straight line, no great skill is required for the backlash adjustment.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an engine equipped with a backlash adjustment mechanism according to the present invention, Fig. 2 is a partial side view of the internal structure of the engine, Fig. 3 is a sectional view of essential parts of the internal structure, and Fig. 4. is a - sectional view in FIG. 3. Explanation of symbols of main parts, 10... Exhaust side camshaft, 11... Intake side camshaft, 12, 1
3...Camshaft gear, 14, 15...Idle gear, 16...Crankshaft gear, 18...
...Arm member, 22...Eccentric shaft, 23...Nut.

Claims (1)

[Scope of utility model registration request] An idle gear that is swingably supported in a direction substantially perpendicular to the rotation axis of two camshafts in the engine and simultaneously meshes with the camshaft gears provided on each of the camshafts is located between its swing center point and swing end. A camshaft characterized by comprising: an arm member pivotally supported at a predetermined position between the two, and adjustment and fixing means for adjusting the swing angle of the arm member and fixing the arm member at a desired angular position. Brush stroke adjustment mechanism in the drive system.