JPS62107211A - Camshaft driving device for four cycle engine - Google Patents

Abstract

PURPOSE:To reduce the noise of gears, by making the intermediate gear engaging with the driving teeth portion of a crankshaft eccentric against the reference line passing through the center of the crankshaft, and enabling the distance between the intermediate gear and the crankshaft te be adjusted freely with oscillating a gear holder by an adjusting mechanism. CONSTITUTION:In the passage in a cylinder block, three intermediate gears 16-18 are engaged with each other, disposed on a same line O1, and received therein. And the respective rotation axes 19-21 of the respective intermediate gears 16-18 are rotatably supported via a bearing member 22, and the rotation axis 21 of the intermediate gear 18 is rotatably supported concavo-convexly via a bracket 26, so that the whole of a gear unit 23 can be supported oscillatably. And the rotation center of the intermediate gear 16 is provided eccentrically against the reference line X1 connecting a crankshaft 3 to the rotation axis 21 for the side of an inlet camshaft 10. On the other hand, an adjusting mechanism 27 in which a pressing rod 17a is forced into the direction always pressing the bearing member 22 with a spring 28 is provided, so that the backlash between the intermediate gear 16 and the driving teeth portion 24 of the crankshaft 3 can be adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overhead cam type four-cycle engine, and particularly to a drive device for a camshaft thereof.

[Prior art]

In engines with a camshaft installed in the cylinder head, a timing chain or belt has traditionally been used to drive the camshaft, but recently, in order to ensure power transmission and eliminate timing discrepancies, a timing chain or belt has been used to drive the camshaft. One that uses multiple gears that fit together is known.

[Problem that the invention seeks to solve]

However, in this configuration, carbon steel or alloy steel is used for the gears for strength reasons, so if the distance between the camshaft and the crankshaft changes due to thermal expansion of the engine, the distance between the gears and the engine side will change. Due to the difference in materials, the backlash of the meshing portion with the camshaft or crankshaft may vary undesirably.

For this reason, there is a problem that the intermediate gear generates a tapping sound and the gear noise increases.

Means for Solving Problem c] Therefore, in the present invention, a plurality of intermediate gears interposed between a camshaft and a crankshaft are integrally connected to each other via a bearing member, and the bearing member is pivotably supported around the rotation axis of an intermediate gear that meshes with the camshaft or crankshaft, and the rotation center of the intermediate gear located on the opposite side of the rotation center of the bearing member is connected to the crankshaft. An intermediate gear is provided eccentrically with respect to a line connecting the shaft or camshaft and the rotation center of the bearing member, and on the engine side, the bearing member is oscillated and meshes with the camshaft or crankshaft. The present invention is characterized by the provision of an adjuster IIM that presses toward the camshaft or crankshaft and adjusts the distance between the intermediate gears and the camshaft or crankshaft that mesh with each other.

[Operation] According to this configuration, by swinging the bearing member between the camshaft and the crankshaft via the adjustment mechanism, the interaxial distance between the intermediate gears meshing with each other and the camshaft or crankshaft can be adjusted. can be adjusted freely.

Therefore, even if the distance between the camshaft and intermediate gear, or the crankshaft and intermediate gear, which mesh with each other changes due to thermal expansion of the engine, the backlash of the meshing part can be maintained at an optimal value, and the gear Noise can be kept low.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described as a double overhead cam type (
The explanation will be based on drawings applied to a 4-stroke engine (DOHC).

Reference numeral 1 in the figure indicates a crankcase, and a crankshaft 3 is pivotally supported in a trunk compartment 2 within this crankcase 1. A cylinder block 4 and a cylinder head 5 are fitted onto the crankcase l, and a piston 6 housed within the cylinder block 4 is connected to the crankshaft 3 via a connecting rod 7.

In the case of this embodiment, the crankcase 1, cylinder block 4, and cylinder head 5 are made of aluminum alloy.

Further, the cylinder head 5 supports an intake valve 8 and an exhaust valve 9, and these intake valves 8 and exhaust valves 9 are individually opened and closed by an intake camshaft 0 and an exhaust camshaft 11.

Both camshafts 10. Reference numeral 11 is disposed within a valve chamber 13 formed between the cylinder radiator 5 and the radiator cover 12, and this valve chamber 13 has a passage provided continuously within the cylinder radiator 5 and the cylinder block 4. It communicates with the inside of the crank chamber 2 via 14.

A gear mechanism 15 is interposed in this passage 14 for transmitting the power of the crankshaft 3 to the intake camshaft IO and the exhaust camshaft 1. The details of this gear mechanism 15 are shown in FIG. I will also explain.

That is, in the passage 14, there are a first intermediate gear 16 and a second intermediate gear 1 made of carbon steel or alloy steel, for example.
7 and a third intermediate gear 18, these three intermediate gears 1B and 17.18 mesh with each other and are arranged in a line along the same straight line 01-01 in the passage I4. There is.

Rotating shaft 19.20.21 of intermediate gear 1B, 17.18
is rotatably supported via a gear holder 22 as a bearing member, and the three intermediate gears 16, 17, and 18 are integrally connected by this gear holder 22 to form a unit. In this gear unit 23, the first intermediate gear 1B located on the crankcase 1 side is connected to a drive tooth portion 24 for driving a camshaft provided on the crankshaft 3.
The third intermediate gear 18 on the cylinder head 5 side also meshes with drive gears 25 and 25 fixed on both camshafts 10 and 11, respectively. Further, in the case of this embodiment, the rotation shaft 21 of the third intermediate gear 18 is connected to the passage 1.
Bracket 26.26 at the opening end into the valve train chamber 13 of 4.
This allows the entire gear unit 23 to be mounted on the third intermediate gear 18 within the passage 14.
It is supported so as to be able to swing around a rotating shaft 21 .

Further, this 11-wheel unit 23 connects the rotation center of the first intermediate gear 1G located on the opposite side to the swing center with a reference line Xl - connecting the axial center of the crankshaft 3 and the axial center of the rotation shaft 21. xl, these three intermediate gears 1B,
A certain butt crush is formed between the meshing parts of the first intermediate gear 16 and the driving gear 24 and the meshing south faces of the third intermediate gear 18 and the driving gear 25 and 25, including the meshing parts of the gears 17 and 18. There is.

On the other hand, the engine cylinder block 4 is provided with an adjustment mechanism 27 for swinging the gear unit 23 to adjust the backlash between the first intermediate gear 16 and the drive tooth section 24. . To explain this adjustment mechanism 27, a press rod 27a that protrudes into the passage 14 is slidably supported on the wall of the cylinder block 4, and the tip of the press rod 27a is connected to the gear holder. 22 is in contact with the side surface on the swinging end side. This pressing rod 27a is always biased by a spring 28 in the direction of pressing the gear holder 22, that is, the direction of pressing the first intermediate gear 16 against the drive tooth portion 24, and the passage of this pressing rod 27a is The amount of protrusion into the inside of the bolt 14 can be increased or decreased by changing the screwing amount of the bolt 29.

The adjustment mechanism 27 includes a ratchet mechanism 30 in the wall of the cylinder block 4 that prevents the pressing rod 27a from being pulled out of the passage 14 and returned to its exit direction.

According to this depiction, the gear unit 23 is connected to the passage 14.
The crankshaft 3 is pivotably supported within the
Since the first intermediate gear 1B that meshes with the drive tooth portion 24 of the gear holder is provided eccentrically with respect to the reference line Xl-Xl passing through the axis center of the crankshaft 3, the gear holder is 22, the first intermediate gear 1
The distance between the crankshaft 6 and the crankshaft 3 can be freely adjusted.

Therefore, even if the interaxial distance between the camshaft 10.11 and the crankshaft 3 changes due to a difference in the materials between the intermediate gears 16 to 18 and engine-side components such as the cylinder head 5, the first intermediate gear The backlash between the drive tooth section 16 and the drive tooth section 24 can be maintained at an optimum value, and therefore, the mutual tapping noise between the tooth surfaces is less likely to occur, and noise can be suppressed to a low level.

The 4-cycle engine according to the present invention is not limited to a DOHC engine with two camshafts, but may also be a so-called 5OHC engine with an intake cam and an exhaust cam on a single camshaft. In this case, the center of swing of the gear unit may be set at the intermediate gear on the crankshaft side, and the backlash may be adjusted between the drive gear of the camshaft and the intermediate gear.

〔Effect of the invention〕

According to the present invention described in detail below, the backlash of the meshing portion between the intermediate gear and the camshaft or crankshaft can be adjusted to an optimum value, and gear noise can be suppressed to a low level.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a sectional view of the engine, FIG. 2 is a partially sectional side view showing the power transmission path from the crankshaft to the camshaft, and FIG. 3 is a diagram showing the ratchet mechanism. This is a cross-sectional view. 3... Crankshaft, 5... Cylinder head, 10.
It...camshaft (intake camshaft, exhaust camshaft>
,te. 17, 18... Intermediate gear, 19.20.21... Rotating shaft, 22... Bearing member (gear holder), 27...
Adjustment mechanism.

Claims (1)

[Claims] In a four-cycle engine in which the power of the crankshaft is transmitted to the camshaft of the cylinder head via a plurality of metal intermediate gears that mesh with each other, the plurality of intermediate gears are integrally connected to each other via a bearing member. an intermediate gear that is connected to the bearing member and pivotally supports the bearing member so as to be able to swing around a rotating shaft of an intermediate gear that meshes with the camshaft or crankshaft, and that is located on the opposite side of the pivoting center of the bearing member; The center of rotation of the bearing member is provided eccentrically with respect to the line connecting the crankshaft or camshaft and the center of rotation of the bearing member, and the bearing member is oscillated on the engine side, and 4. It is characterized by being provided with an adjustment mechanism that presses the meshing intermediate gears toward the camshaft or crankshaft side and adjusts the distance between the shafts between these mutually meshing intermediate gears and the camshaft or crankshaft. Cycle engine camshaft drive device.