JPH025041Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a gear-driven camshaft drive device for an engine of a vehicle such as a motorcycle.

Conventionally, this type of camshaft drive device, as seen in Japanese Utility Model Application Publication No. 56-59346, has been used to connect a gear on a camshaft and a gear on a crankshaft to separate parts connected to the engine body. At least two intermediate gears connected by a shaft, or at least two intermediate gears connecting a gear on a camshaft and a gear on a crankshaft are pre-mounted on a holding member. There is a system that simplifies the assembly of the intermediate gear by configuring the entire assembly into one assembly and fixing it to the engine body by connecting it to the holding member.

However, these gear-driven camshaft drive devices do not take into account the thermal expansion of each member,
Generally speaking, when the engine temperature rises due to the difference in thermal expansion between the engine block and intermediate gear holding members, which are made of light alloy, and the gears, which are made of iron-based materials, the backlash of the gears increases as the axial center spacing of the gears increases. However, there is a problem that the amount of noise increases. As a means for absorbing backlash in gears, a helical gear (for example, Japanese Utility Model Publication No. 46-23873
Split gears disclosed in Japanese Patent Publication No. 12588), and GM gears that combine two gears with different numbers of teeth and utilize the difference in pitch between the two gears to absorb crushing (for example, disclosed in Japanese Patent Publication No. 12588/1988). A gear consisting of a gear integral with a shaft and an auxiliary gear that idles on the shaft, has a slightly larger number of teeth than the gear, and is crimped to the gear by a spring or elastic body), etc. is publicly known. However, since the thickness of these gears increases, if an attempt is made to absorb the backlash by using helix gears or GM gears for all gears, the width of the engine will become wider.

This invention was made to solve the above problems,
A camshaft drive device for an engine in which a cam gear on a camshaft of an engine body and a timing gear on a crankshaft are gear-coupled via a gear train consisting of at least two intermediate gears meshing with each other. A plurality of intermediate gears are preliminarily connected to a unit frame having a coefficient of thermal expansion approximately equal to that of the intermediate gears to form an integrated intermediate gear unit by being properly engaged with each other, and the intermediate gear unit is attached to the engine body by means of the unit frame. In addition, by meshing the timing gear and the intermediate gear that meshes with the timing gear, and the cam gear and the intermediate gear that meshes with this with a crush absorption means, the engine temperature can be reduced without increasing the width of the engine. An object of the present invention is to provide a camshaft drive device for an engine that absorbs the bumpiness of a drive gear during upward movement, prevents meshing noise of the gears, and facilitates assembly of an intermediate gear.

An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 to 3, an engine body 1 includes a cylinder block 3 consisting of a pair of left and right cylinders 2, 2 arranged in a V-shape in the front and rear, a crankcase 4 in the lower part of the cylinder block 3, and a crankcase 4 in the upper part of the cylinder block 3. A V-type four-cylinder engine is constituted as a whole by a pair of front and rear cylinder heads 5, 5 and a pair of front and rear cylinder head covers 6, 6 on the upper surface thereof. The cylinder head 5 is fastened to the upper surface of the cylinder block 3 with a cylinder stud bolt 8 via a gasket 7. The upper part of the cylinder 2 is equipped with a spark plug 9, an intake valve 10, and an exhaust valve 11, and a piston 12 fitted into the cylinder 2 is connected to a crankshaft 13 in the crankcase 4.
The output of the piston 12 is converted into rotation of a crankshaft 13, and the rotation of the crankshaft 13 drives the vehicle via a clutch 14 and a transmission gear 15.

A pair of front and rear camshafts 16, 16 are provided in the front and rear head covers 6 at the top of the engine body 1, respectively, and a cam gear 17 on the camshaft 16 and a timing gear 18 on the crankshaft 13 are connected to first and second camshafts, which will be described later. They are connected by an integrated intermediate gear unit 20 having intermediate gears 21 and 22 pivoted thereon. The cam gear 17, timing gear 18, and gear train unit 20 are connected to a pair of left and right cylinders 2 of the engine body 1,
The cylinder 2 is disposed within a gap 19 that defines the left and right cylinders 2, and is shared by both the left and right cylinders 2, 2.

Details of the intermediate gear unit 20 are shown in FIGS. 4 and 5.
As shown in the figure, the unit frame 23 is constructed by assembling a pair of front and rear retaining plates 23a, 23b into a frame shape with a pair of left and right bolts 24, 24.
The first intermediate gear 21 that meshes with the timing gear 18 on the crankshaft 13 and the second intermediate gear 22 that meshes with the cam gear 17 on the camshaft 16 are properly meshed with each other between a and 23b, so that each gear shaft 25 , 26 via bearings 27 and 28, respectively. In addition, the gear shafts 25 and 26 have oil holes 25a and 26a.
is provided to lubricate the bearings 27 and 28, and the supporting surface of the bearing 28 of the gear shaft 26 of the second intermediate gear 22 is eccentric, and by rotating the gear shaft 26, the bearing 28 is connected to the first intermediate gear 21. The shaft spacing between the second intermediate gear 22 and the second intermediate gear 22 is increased or decreased, and by inserting the dowel pin 29 at an appropriate position, both the intermediate gears 21, 2
2 proper meshing positions are set. In the present invention, especially, the unit frame 23 and the first
and the second intermediate gears 21 and 22 are made of a material having substantially the same coefficient of thermal expansion, for example, when a ferrous material is used for the intermediate gears 21 and 22, the unit frame 23 is also made of an ferrous material, and thus the intermediate gear unit Even if the temperature of unit frame 23 rises,
Since the first and second intermediate gears 21 and 22 expand at the same rate, the mutual meshing relationship between the intermediate gears 21 and 22 does not change, and it is possible to prevent the occurrence of gear meshing noise due to an increase in backlash. can.
On the other hand, on the engine body 1 side, the timing gear 18 and the cam gear 17 thermally expand separately with respect to the intermediate gear unit 20, so the timing gear 18 and the first intermediate gear 21, and the cam gear 17 and the second intermediate gear 2
Each meshing with 2 causes an increase in crushing due to an increase in temperature. In order to absorb this backlash, a backlash absorbing means is employed in the meshing between the timing gear 18 and the first intermediate gear 21 and between the cam gear 17 and the second intermediate gear 22.

The crushing absorption means is a spiral gear, GM
Gears and the like are known, and any of these may be used, but in the illustrated embodiment, the first intermediate gear 21 is a GM gear, and the cam gear 17 is a helical gear.
As clearly shown in FIG. 5, the first intermediate gear 21 to which the GM gear is applied has a secondary gear 21b on the side surface of the main gear 21a, which has the same diameter and a slightly different number of teeth.
Disk plate 2 is rotatable relative to 1a.
1c, disk spring 21d, washers 21
e, and the difference in pitch between both gears 21a and 21b is used to absorb the backlash that occurs between the timing gear 18 and the timing gear 18. In addition, in the meshing between the first intermediate gear 21 and the second intermediate gear 22,
The above GM without using the thermal expansion compensation means according to the present invention.
If a crush absorption means using gears is used, a secondary gear 21b for a timing gear and a secondary gear 21b' for a second intermediate gear 22 shown by a chain double-dashed line in FIG. 5 are installed in parallel to the first intermediate gear 21. Therefore, the thickness of the intermediate gear unit 20 increases from t to t' as shown in FIG. 5, and the width of the engine body 1 increases accordingly.

As shown in FIGS. 6 and 7, the helix gear applied to the cam gear 17 is made up of two congruent spur gears 17a, 17a'. A plurality of long holes 17b in the circumferential direction
are provided correspondingly, and a pin 16b standing upright on a flange 16a formed on the camshaft 16 is inserted through the corresponding long holes 17b, and both spur gears 17
a, 17a are supported so as to be movable by a predetermined amount in the circumferential direction. Also, spring holes 17c are provided in the circumferential direction of both spur gears 17a and 17a', and a serrated spring 17d is resiliently installed in one of the spring holes 17c of both spur gears 17a and 17a'. The pitches of the spur gears 17a and 17b are biased in a direction that is shifted from each other to absorb backlash that occurs when meshing with the second intermediate gear 22. Further, a damper spring 17e is elastically installed in the other spring hole 17c to provide a damping effect.

To attach the intermediate gear unit 20 to the engine body 1, for example, as shown in FIGS. 2 and 3, the intermediate gear unit 20 is inserted into the gap 19 of the engine body 1, and the first intermediate gear 21 is connected to the timing gear 1.
8, the second intermediate gear 22 is positioned so as to mesh with the cam gears 17, 17 at the same time, and mounting seats 23c, 23d formed on the upper parts of both retaining plates 23a, 23b of the unit frame 20 are preformed on the cylinder head 5. The holding member 23 matches the receiving seat 5a.
A mounting seat 23e formed on one side of the lower part matches a receiving seat 3a formed in advance on the cylinder block 3, and is secured by tightening with bolts 30, 30', and 31, respectively.

As explained above, according to the present invention, at least two intermediate gears that connect the cam gear on the camshaft of the engine body and the timing gear on the crankshaft are connected, and The intermediate gear unit is preliminarily formed into an integral intermediate gear unit by being shaft-mounted on a substantially equal unit frame with appropriate meshing, and the intermediate gear unit is attached to the engine body by the unit frame, and the intermediate gear unit meshing with the timing gear is attached to the engine body by the unit frame. By meshing the gear, the cam gear, and the intermediate gear that meshes with it using a backlash absorption means, when the engine temperature rises,
Since the intermediate gear expands with the same coefficient of thermal expansion as its holding member, the proper meshing relationship between the intermediate gears does not change, and the backlash that occurs between the timing gear and cam gear and the intermediate gear is caused by GM gears or serrations. Since the noise is absorbed by the backlash absorbing means such as gears, the generation of noise due to increased backlash can be prevented without increasing the width of the engine compared to the case where the backlash absorbing means is applied to all gears. The intermediate gear unit facilitates assembly of the intermediate gear within narrow engine body gaps.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a plan view of a V-type 4-cylinder engine to which the present invention is applied;
2 is a cross-sectional view taken along the - line in FIG. 1, FIG. 3 is a cross-sectional view taken along the - line in FIG. 2, FIG. 4 is a front view of the intermediate gear unit, and FIG. 5 is a - FIG. 6 is a front view of the cam gear, and FIG. 7 is a sectional view taken along the - line in FIG. 6. 1...Engine body, 13...Crankshaft, 1
6...Cam shaft, 17...Cam gear, 18...Timing gear, 20...Intermediate gear unit, 21...
...First intermediate gear, 22... Second intermediate gear, 23...
...Unit frame.

Claims (1)

[Scope of utility model registration request] In an engine camshaft drive device in which a cam gear on a camshaft of an engine body and a timing gear on a crankshaft are gear-coupled via a gear train consisting of at least two intermediate gears that mesh with each other,
The above-mentioned at least two intermediate gears are pivoted in a proper mesh on a unit frame having substantially the same coefficient of thermal expansion as the intermediate gears to form an integrated intermediate gear unit in advance, and the intermediate gear unit is assembled by the unit frame. The camshaft drive of an engine is characterized in that the timing gear and the intermediate gear that mesh with the timing gear and the intermediate gear that meshes with the timing gear and the cam gear and the intermediate gear that meshes with the timing gear and the intermediate gear that mesh with the timing gear are meshed by a backlash absorbing means. Device.