JP2534472B2 - Camshaft drive structure for V-type DOHC engine - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a camshaft drive structure for a V-type DOHC engine.

[Prior art]

The DOHC (double overhead camshaft) type engine has two camshafts driving the intake valve and the exhaust valve arranged in parallel to the upper part of the cylinder head, and the V-type engine has one crankshaft. The left and right cylinders are offset in the crankshaft direction with respect to the shaft, and are arranged in a V shape.

The V-type DOHC engine is equipped with both of the above types at the same time. However, in the conventional V-type DOHC engine, due to the structural peculiarities as described above, the structure for driving the camshaft by the power of the crankshaft becomes large. Since the camshaft drive structure and the left and right cylinders are offset in the crankshaft direction, the left and right cylinder heads have to be shaped differently from each other. For this reason, two types of molds for molding the cylinder head are required, resulting in high cost.

[Object of the Invention]

It is an object of the present invention to provide a camshaft drive structure for a V-type DOHC engine, which is made compact by devising the layout of the camshaft drive structure and which can share the left and right cylinder heads.

[Structure of Invention]

According to the present invention for achieving the above object, cylinders in the left and right rows are offset from each other in the crankshaft direction with respect to one crankshaft, and are arranged in a V shape. In a V-type DOHC engine in which two camshafts for driving the shafts are arranged in parallel, one shaft end of the camshafts arranged in twos is interlocked with the shaft end of the crankshaft via a transmission means. And two cam shafts are linked and interlocked by a transmission means at a shaft end portion on the blank side offset from the cylinder row on the other side, and the transmission means for connecting the cam shafts is driven by a chain drive or a gear. It is characterized in that it is configured to be driven and accommodated in the cylinder head, and the shaft end side of the one cam shaft is supported via a bearing portion provided on a side wall portion of the cylinder head.

〔Example〕

 Hereinafter, the present invention will be described with reference to an embodiment shown in the drawings.

The figure shows a V-type DOHC engine with the front in the direction of arrow F. 1a and 1b are vertically divided crankcases.
Is a cylinder block, and 3,3 are cylinder heads. A crankshaft 4 is supported by bearings on the mating surfaces of the crankcases 1a and 1b. Cylinder block 2 has cylinders 2a, 2a, 2a arranged in a line with three cylinders on each side.
2b, 2b, 2b are arranged in a V shape. The left and right row cylinders 2a, 2a, 2a and 2b, 2b, 2b are offset in the crankshaft direction, and in this embodiment, the right cylinder row is displaced rearward with respect to the left cylinder row.

The left and right cylinders 2a, 2a, 2a; 2b, 2b, 2b are respectively provided with cylinder heads 3, 3 on the upper part thereof, and a cam shaft 5a for driving an intake valve and a cam shaft 5b for driving an exhaust valve are provided on the upper part thereof. It is provided in parallel. Of the two cam shafts 5a, 5b; 5a, 5b provided on the left and right cylinder heads 3, 3, one of the cam shafts 5a, 5a arranged on the inner side has its shaft end at the cylinder head 3, 3
Of the gears 6, 6 are fixed, and the shaft ends of the gears 6, 6 are supported via bearings S, S provided on the side walls of the cylinder heads 3, 3. An endless toothed belt 8 is wound around the gears 6 and 6 and a gear 7 fixed to the shaft end of a crank shaft 4 protruding forward of the crankcases 1a and 1b. The power of 4 is transmitted. The number of teeth of the gear 6 is twice that of the gear 7, so that the power of one half rotation of the crankshaft 4 is transmitted to the camshaft 5a.

Further, the two cam shafts 5a, 5b are configured such that power is transmitted from the cam shafts 5a to 5b via the chain 10 having the sprockets 9, 9 fixed to the shaft ends thereof and wound therebetween. There is. Since the sprocket 9 only needs to rotate both cam shafts 5a and 5b at the same time, the size (outer diameter) of the sprocket 9 is not restricted in relation to the rotation speed of the gear 7, unlike the gear 6. Therefore, the outer diameter can be made as small as possible than the gear 6, so that the end portions of the cam shafts 5a, 5b on the input side from the crank shaft 4 can be made as compact as possible. You can

The transmission means of the sprockets 9 and 9 and the chain 10 for driving the cam shafts 5a and 5b are housed in both cylinder heads 3 and 3 and arranged on opposite sides, and offset with respect to the other cylinder row. It is arranged at the end of the blank portion side. That is, in this embodiment, the transmission means for the cam shafts 5a, 5b of the right cylinder head 3 are arranged in the offset blank portion formed on the front side, and the transmission means for the cam shafts 5a, 5b of the left cylinder head 3 are arranged. Are arranged in the offset blank portion formed on the rear side. In this way, the transmission means is arranged by utilizing the offset blank portions located on the opposite sides to each other, so that the axial length of the cylinder head 3 and the like for accommodating the transmission means is shortened and the whole is made compact.

Further, since the transmission means for the two camshafts 5a, 5b are arranged at the shaft ends on the opposite sides of the left and right cylinder heads 3,3, the left and right cylinder heads 3,3 are located at the center between them. It has a line-symmetrical relationship in which it is rotated 180 ° with respect to the vertical axis. Therefore, the cylinder heads 3 having the same shape for accommodating the power transmission means can be shared left and right. Of course, the shaft hole portion of the cam shaft 5a protruding for input from the crankshaft 4 remains as an asymmetric portion, but this portion does not pose any problem by being filled with a blind plug such as rubber.

Further, in the present invention, the transmission means for connecting the cam shafts 5a, 5b; 5a, 5b are housed in the cylinder heads 3, 3 and the transmission formed by the gears 6, 6, 7 and the toothed belt 8 is mounted on the crankshaft 4. Since the transmission means side of one of the cam shafts 5a, 5a connected via the means is supported via bearing portions S, S provided on the side wall portions of the cylinder heads 3, 3, the cam shafts are connected to each other. The protruding length of the cam shaft 5a having the transmission means on the gear 6 side protruding from the cylinder head 3 can be shortened in the same manner as the other cam shaft 5a, and bending applied to the cam shaft 5a at the portion protruding from the cylinder head 3 The moment can be reduced.

Although the toothed belt 8 is used as the endless transmission means from the crankshaft 4 to the camshaft 5a in the above embodiment, a chain or the like may be used instead. Also, the camshaft 5
Although a chain drive using a chain as the transmission means between a and 5b is used, a gear drive using a toothed belt or a gear may be used instead.

〔The invention's effect〕

As described above, the present invention relates to one crankshaft,
V-shaped DOHC engine in which left and right columnar cylinders are arranged in a V shape with offset in the crankshaft direction, and two camshafts driving the intake and exhaust valves are arranged in parallel above the cylinder heads provided in each cylinder row. In this case, one shaft end of the two cam shafts arranged above is interlockingly connected to the shaft end of the crank shaft via a transmission means, and two cam shafts are connected to each other on the cylinder line on the other side. With respect to the shaft end on the blank side which is offset with respect to the above, the transmission means for connecting and interlocking with the transmission means for connecting the cam shafts is constituted by chain drive or gear drive, and is housed in the cylinder head, The cam shaft is supported at the shaft end side through a bearing portion provided on a side wall portion of the cylinder head.

As described above, the transmission means housed in the cylinder heads for driving the two cam shafts on the left and right cylinder heads is constituted by chain drive or gear drive and is offset with respect to the cylinder row on the other side. Also, since the layout is on the blank side, the axial length of the cylinder head or the like accommodating the power transmission means can be shortened to make the whole compact.

Further, since the transmission means housed in the cylinder head is arranged symmetrically with respect to the left and right cylinder heads with respect to the center of the both, the left and right cylinder heads accommodating the transmission means can have the same shape in common. Become.

Moreover, since the transmission means for connecting the camshafts to each other is housed in the cylinder head and the bearing portion provided on the side wall portion of the cylinder head supports the transmission means side of the camshaft connected to the transmission means of the crankshaft, The camshaft, which has a transmission means that connects the camshafts to each other on the transmission means side, has a protruding length from the cylinder head that is the same as that of the other camshaft, so that the bending moment applied to the protruding camshaft is reduced. Can be made smaller.

[Brief description of drawings]

FIG. 1 is a plan view showing only an essential part of an upper portion of a cylinder head of a V-shaped DOHC engine having a camshaft drive structure according to an embodiment of the present invention, and FIG. 2 is a schematic front view of the engine. 2a, 2b …… Cylinder, 3 …… Cylinder head, 4 …… Crank shaft, 5a, 5b …… Cam shaft, 6,7 …… Gear, 8 …… Toothed belt, 9 …… Sprocket, 10 …… Chain , S ... Bearing part.

Claims (1)

(57) [Claims] 1. A cam for driving intake and exhaust valves above a cylinder head provided in each cylinder row, wherein left and right row-shaped cylinders are offset from each other in the crank axis direction with respect to one crankshaft. V type DO with two axes arranged in parallel
In the HC engine, one shaft end of the two cam shafts that are arranged is interlockingly connected to the shaft end of the crank shaft via a transmission means, and two cam shafts are connected to each other on the other side. The shaft end portion on the blank side offset with respect to the cylinder row is interlockingly connected by a transmission means, and the transmission means for connecting the cam shafts is configured to be chain drive or gear drive, and is housed in the cylinder head. A camshaft drive structure for a V-DOHC engine, characterized in that the shaft end side of one of the camshafts is supported via a bearing portion provided on a side wall portion of the cylinder head.