JPS6358245B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tensioning device for a drive transmission band of a valve drive camshaft that opens and closes intake and exhaust valves in a DOHC internal combustion engine.

Generally, when the means for driving a valve camshaft is such that the valve camshaft is linked to a crankshaft via a transmission band such as an endless chain, tension is applied to apply a constant tension to the transmission band. Although a device is attached to efficiently transmit the rotation of the crankshaft to the valve drive camshaft, the present invention is applicable to a DOHC internal combustion engine in which a plurality of cylinders are arranged in series.
A part of the tensioning device can be provided by utilizing a dead space formed inside the transmission band, and an effective tension can always be applied to the transmission band.
The main purpose of this invention is to provide a tensioning device for a transmission band for driving a valve train camshaft in a DOHC type internal combustion engine, which has a simple structure.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In a DOHC type multi-cylinder internal combustion engine, two engine blocks B ₁ and B ₂ are arranged in a V-shape with each other, and each engine block B ₁ and B ₂ includes the following: Two cylinders C ₁ , C ₁ each in the direction perpendicular to the plane of Figure 1
and C ₂ and C ₂ are arranged in series. Each center line L ₁ −L ₁ and L ₂ −L ₂ of each engine block B ₁ , B ₂
A crankshaft 1 is disposed on the intersection of the two, and the crankshaft 1 is rotated counterclockwise in FIG. Each engine block B ₁ , B ₂ is normally
Cylinder heads 3, 3 are polymerized and fixed onto the cylinder blocks 2, 2, and furthermore, head covers 4, 4 are attached onto these cylinder heads 3, 3.

Each cylinder head 3, 3 has the center line L ₁
A pair of valve drive camshafts 5, 6 for intake and exhaust are rotatably supported symmetrically to the left and right of -L ₁ and L ₂ -L ₂ and parallel to the crankshaft 1. , these valve drive camshafts 5, 6; 5, 6,
Suction and exhaust valves 7, 8; cams 9, 1 for opening and closing of 7, 8
0; 9, 10 are provided integrally.

There are two drive sprockets 1 on the crankshaft 1.
1, 11 are fixed in parallel, and driven sprockets 13, 14; 13, 14 are fixed to each pair of camshafts 5, 6; 5, 6, respectively.
3, 14; An endless transmission chain 15, 15 is suspended between 13, 14, and the rotation of the crankshaft 1 is
The power is transmitted from each drive sprocket 11 to valve drive camshafts 5 and 6 via a transmission chain 15 and driven sprockets 13 and 14, so that intake and exhaust valves 7 and 8 can be opened and closed.

An arcuately curved tensioner body 16 is disposed on the outside of the slack side of each transmission chain 15, and a fixed end 17 of the tensioner body 16 is rotatably supported by the internal combustion engine body via a support shaft 19. The movable end 18 is rotatably connected to the tip of a swing arm 21, which will be described later, by a pivot pin 20. A guide member 22 having a U-shaped cross section is fixed to the back side of the middle part of the tensioner main body 16, and the guide member 22 surrounds both sides of the transmission chain 15 to guide it so that it does not swing from side to side.

Inside the endless transmission chain 15, between the crankshaft 1 and the pair of valve drive camshafts 5 and 6,
The tensioner main body 16 is elastically directed toward the transmission chain 15 to apply a constant tension to the chain 15, and even if the transmission chain 15 stretches, the tension is automatically kept constant. A mechanism for adjustment is provided. Next, to explain the structure of this mechanism, as clearly shown in FIG.
... are integrally erected at each vertex of the rectangle, and support frames F formed vertically long on these pillars 24, 24... hold fixing bolts 25, 25...
It is rigidly fixed by. The support frame F includes an upper support frame 26 that extends upward from the lower struts 24, 24... toward the gap S between the valve drive camshafts 5 and 6.
and a lower support frame 27 extending below the tops of the lower support columns 24, 24... are integrally connected, and at the upper end of the upper support frame 26, there is further an auxiliary frame 28 with a channel-shaped cross section. This auxiliary frame 28 is fitted from above, and is firmly fixed onto two upper supports 29, 29 integrally extending from the cylinder head 3 with fixing bolts 30, 30.
The upper struts 29, 29 are disposed outside the four lower struts 24, 24, . . . between the pair of driven sprockets 13, 14, as clearly shown in FIG.

As previously mentioned, the movable end 18 of the tensioner body 16
A swinging arm 21 whose tip is rotatably connected to is curved in a dogleg shape when viewed from the side, and extends across the transmission chain 15 into the gap formed between the intake and exhaust valve drive camshafts 5 and 6. It extends to a portion S, and its base end is rotatably supported on the upper end of the upper support frame 26 with a pivot 31. The swing arm 21 has a U-shaped cross section, and a portion of the outer periphery of one of the driven sprockets 13, 14 enters inside the swing arm 21. As clearly shown in FIG. 1A, a swinging locking piece 32 is swingably supported at the lower end of the lower support frame 27 with a pivot 33. 32a has a locking hole 34 drilled therein, and a rod 36 which is pivotally supported with a pivot 35 at the middle part of the swinging arm 21 is inserted into the locking hole 34.
The free end of is loosely threaded. Also, the swing arm 21
A tensioner spring 37 is stretched between the intermediate portion of the locking piece 32 and the swing locking piece 32.
In FIG. Tensioner body 16
is brought into pressure contact with the slack side of the transmission chain 15, and the clockwise rotation of the swinging locking piece 32 engages the diagonal edges e ₁ and e ₂ of the locking hole 34 with the free end of the rod 36. This acts to prevent the rod 36 from moving with respect to the swing locking piece 32 in the pulling direction, that is, the movement in the direction of arrow A in FIG. 1A.

A bow-shaped slider 38 is provided on the tension side of each transmission chain 15, 15, and a boss 39 is fixed to the base of the slider 38 near the crankshaft as shown in FIG. The boss 39 is rotatably supported by a support pin 42 supported in a cantilever manner on the engine body. Further, a restraining piece 40 made of an elastic material is fixed to the rear surface of the intermediate portion of the driven sprocket of the slider 38, and the slider 38 is attached to this restraining piece 4.
0 to the engine block. The slider 38 swings about the support pin 42 and guides the tension side of the transmission chain 15 to move along a predetermined trajectory. A guide piece 41 having a U-shaped cross section is provided in the middle of the engine block, and this guide piece 41 surrounds the transmission chain 15 and guides it to prevent it from wobbling laterally.

Next, to explain the operation of the embodiment of the present invention, when the internal combustion engine is operated, the crankshaft 1
is rotated counterclockwise in FIG.
and driven sprockets 13, 14; 13, 14
It is transmitted to the intake and exhaust camshafts 5, 6; 5, 6 via the valve mechanism. At this time, the tensile force of the tensioner spring 37 elastically presses the tensioner main body 16 into contact with the slack side of the transmission chain 15 via the swing arm 21, thereby imparting a predetermined tension to the transmission chain 15. By the way, when the transmission chain 15 stretches to some extent, the tensile force of the tensioner spring 37 swings the swinging arm 21 clockwise in FIG. A thrust is generated in the direction of the arrow RO in the figure, causing the swinging locking piece 32 to swing slightly counterclockwise, and the rod 36 moves in the direction of the arrow RO, and the tensioner body 16 is connected to the transmission chain via the swinging arm 21. It is moved to the transmission chain 15 side so as to follow the elongation of chain 15, and its tension is automatically adjusted to be constant.

As described above, according to the present invention, in a DOHC internal combustion engine, a swing arm is attached to the movable end of the tensioner body that comes into contact with the outer surface of the slack side of the transmission band that interlocks the crankshaft and the intake and exhaust camshafts. The tips are rotatably connected, and this swing arm crosses the transmission band and faces the space between the intake and exhaust camshafts, where its base end is swingably supported on the engine block. The swinging arm can be set to be sufficiently long without protruding outside the transmission band, so that when the tensioner body shifts due to slack in the transmission band, the tensioner spring moves into the tensioner via the swinging arm. The tension that the tensioner body transmits to the transmission band can be kept almost constant without changing the direction of the force applied to the body, and the rotation of the crankshaft can always be efficiently transmitted to the valve drive camshaft. .

Furthermore, although the swing arm is formed sufficiently long as described above, a part of the swing arm faces the space between the valve drive camshafts, and the base end of the swing arm is pivotally supported on the engine block in the space. Most of the moving arm is located inside the transmission band, so there is no restriction on the layout or installation of other equipment.

[Brief explanation of the drawing]

FIG. 1 is a front view of the device of the present invention, and FIG. 1A is a front view of the device of the present invention.
2 is a partially enlarged view of the figure, FIG. 2 is a sectional view taken along the line in FIG. 1, FIG.
The figure is a sectional view taken along the line of FIG. 1. _B1 , _B2 ...Engine block, _C1 , _C2 ...Cylinder, L1 _{-L1 , L2} - _L2 ...Center line, S...Gap portion,
1...Crankshaft, 5, 6...Valve train camshaft, 7...
...Intake valve, 8...Exhaust valve, 15...Transmission chain as a transmission band, 16...Tensioner body, 17...
... fixed end, 18 ... movable end, 21 ... swinging arm, 37 ... tensioner spring.

Claims (1)

[Claims] 1. An engine block having a plurality of cylinders arranged in series, intake and exhaust valves that open and close the intake and exhaust ports opening into the combustion chamber of each cylinder, and an engine block that passes through the center line of each of the plurality of cylinders. Suction and exhaust valve drive camshafts that are arranged on the left and right sides with respect to the center plane and open and close the intake and exhaust valves, respectively, and a transmission band that rotationally drives these valve drive camshafts in conjunction with a crankshaft. In a DOHC internal combustion engine with
A tensioner body is brought into contact with the outer surface of the slack side of the transmission band, and the fixed end of the tensioner body is pivotally supported at a proper position on the engine block, and the tip of a swing arm is rotatably connected to the movable end of the tensioner main body, and the swing arm is rotatably connected to the movable end of the tensioner body. The arm crosses the transmission band and faces a gap formed between the intake and exhaust camshafts, and the base end of the swing arm is swingable to the engine block in the gap. A tensioning device for a transmission band for a valve drive camshaft in a DOHC type internal combustion engine, which is pivotally supported and further has a tensioner spring connected to the swing arm to spring the tensioner body toward the transmission band.