JPH06185313A - Camshaft drive device of v-type engine - Google Patents

Abstract

PURPOSE:To provide a camshaft drive device of a V-type engine capable of lessening a projection amount from an engine end part with a small number of parts, that is, at low cost in the V-type engine having a compact combustion chamber with a small valve nipping angle. CONSTITUTION:In a camshaft drive device of a V-type engine which is provided with intake and exhaust camshafts 3, 4 respectively on upper parts of left and right banks arranged in a V-type shape and which transmits rotation of a crankshaft 5 to these intake and exhaust camshafts 3, 4 through a chain and others, the left and right banks are alternately moved in the direction of the crankshaft 5. By moving back an end surface 2a of one of the banks more than an end surface 2b of the other of the banks, an offset part 30 is formed, and on the offset part 30, a first idler 32 of large diameter to which rotation of the crankshaft 5 is decelerated through the chain and others 31 and transmitted is provided. Additionally, on the first idler 32, a second idler 34 to transmit rotation to the intake and exhaust camshafts 3, 4 through the chain and others 33 is integrally provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft drive device for a V-type engine, which drives intake / exhaust camshafts provided on upper portions of left and right banks via a chain or the like.

[0002]

2. Description of the Related Art As a camshaft driving device for a V-type DOHC engine, one shown in FIG. 2 is known (Japanese Patent Laid-Open No. 30906/1990). In this engine 1, a single endless chain 6 is wound around intake / exhaust cam shafts 3 and 4 and crank shafts 5 provided above the left and right banks 2, and the rotation of the crank shaft 5 causes the chain 6 to rotate. It is adapted to be transmitted to the intake / exhaust cam shafts 3, 4. In the figure, 7 is a chain guide and 8 is a chain tensioner.

By the way, in a four-stroke engine, the rotation of the intake / exhaust cam shafts 3 and 4 must be reduced to 1/2 of that of the crankshaft 5, so that the sprocket diameters 3a of the intake / exhaust cam shafts 3 and 4,
4a must be double the crank gear diameter 5a. Therefore, in the engine 1 having the above configuration, the left and right banks 2
The large-diameter sprockets 3a and 4a are arranged in parallel on the upper part of the above, and the angle between the intake and exhaust valves becomes large. As a result, a compact combustion chamber and head cannot be formed, and the entire width of the engine is widened.

.. As a cam shaft drive device that solves this problem, the one shown in FIG. 3 is known (Japanese Patent Laid-Open No. 63-128).
No. 08 bulletin). In this engine 9, a large-diameter sprocket 10 is attached to the intake camshafts 3 inside the left and right banks 2, and the rotation of the crankshaft 5 is decelerated by the large-diameter sprocket 10. The rotation reduced by the large-diameter sprocket 10 is the same as that of the small-diameter sprocket 1.
It is also transmitted to the exhaust cam shaft 4 via the cam cam chain 12 and the cam cam chain 12. In the figure, 13 is a tensioner for a cam cam chain. According to this structure, the valve holding angle can be made smaller than that of FIG. 2, and a compact combustion chamber can be obtained.

However, a total of 3 cam cam chains 12 and one main chain 14 as a drive chain.
Since a chain of books is required, the tensioner 13,1
The number of parts including the five and the guide 16 increases, resulting in high cost. In addition, the large sprocket 10 and the small sprocket 1
Since 1s are mounted in a pile, the amount of protrusion 18 from the engine end 17 becomes large. Further, since the intake and exhaust cam shafts 3 and 4 are driven by the cam cam chain 12, the distance between the cam shafts 3 and 4 is limited (generally said to be around 95 mm), the valve holding angle is limited, and the combustion chamber is limited. Can not be sufficiently miniaturized.

[0006] As a camshaft drive device which further promotes the miniaturization of the combustion chamber by further reducing the valve holding angle, a device shown in FIG. 4 is known (JP-A-2-169809, etc.). The engine 19 uses a large-diameter idle gear 20 provided in each of the left and right banks 2 for crankshaft 5
Of the intake / exhaust cam shafts 3, which are decelerated by the small-diameter idle gear 21 coaxially fixed to the large-diameter idle gear 20.
4 is driven. According to this configuration, since the rotation of the crankshaft 5 is sufficiently reduced by the large-diameter idle gear 20, the diameters of the sprockets of the intake and exhaust camshafts 3 and 4 can be reduced. Therefore, the valve holding angle can be made smaller than that of FIG. 3, and the combustion chamber can be made compact.

[0007]

However, since the number of drive chains 22, 23, 24, 25 becomes four, the number of parts including accessories such as the tensioner 26 and the guide 27 increases, resulting in high cost. Becomes Also, the crankshaft 5
Since it is necessary to distribute the rotation of the large-diameter idle gears 20 to the left and right, it is necessary to stack the crank gears 5 on top of each other, and it is necessary to stack the small-diameter idle gears 21 on the large-diameter idle gears 20 so that the engine end The protrusion amount 28 from the portion 17 becomes larger than that of FIG. That is, the total length of the engine becomes long and the mountability on the vehicle deteriorates.

An object of the present invention, which was devised in view of the above circumstances, is to provide a camshaft drive device for a V-type engine which can reduce the amount of protrusion from the engine end portion with a small number of parts, that is, at low cost. is there.

[0009]

In order to achieve the above object, the present invention provides intake and exhaust cam shafts on the upper portions of the left and right banks arranged in a V shape, and the crank shaft rotates on these intake and exhaust cam shafts. In a camshaft drive device for a V-type engine that transmits power through a chain or the like, the left and right banks are offset from each other in the crankshaft direction, and the end face of one bank is pulled in from the end face of the other bank to form an offset portion. The offset portion is provided with a large-diameter first idler through which rotation of the crankshaft is decelerated and transmitted through a chain or the like, and the first idler is configured to rotate the intake and exhaust camshaft through the chain or the like. The feature is that a second idler for transmission is integrally provided.

[0010]

According to the above construction, the rotation of the crankshaft is decelerated through the chain or the like and transmitted to the large-diameter first idler, and the chain or the like is removed from the second idler integrally provided on the first idler. It is transmitted to the intake and exhaust cam shafts on the left and right banks via the.

Here, since the first idler and the second idler are provided in the offset portion formed by pulling one bank end surface from the other bank end surface, the space of the offset portion which has conventionally been a dead space. Will be effectively used. Therefore, the amount of protrusion from the engine end in the crankshaft direction is reduced, and the total length of the engine can be suppressed.

Further, to the intake and exhaust cam shafts of the left and right banks,
Since the rotation decelerated by the first idler is transmitted, the drive wheel diameter (sprocket diameter, pulley diameter) of the intake / exhaust cam shaft can be reduced. Therefore, the valve holding angle can be reduced, a compact combustion chamber can be achieved, and the entire engine width can be reduced.

[0013]

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

As shown in FIG. 1, the engine 29 is
This is a so-called V-type DOHC engine in which intake and exhaust cam shafts 3 and 4 are provided above the left and right banks 2 arranged in a V-shape. The left and right banks 2 are displaced in the crankshaft direction by at least the thickness of the big end of the connecting rod, and as a result, one bank end face 2a is formed with an offset portion 30 drawn in from the other bank end face 2b. .

The offset portion 30 includes the crankshaft 5
A first idler 32 is provided to which the rotation of is reduced and transmitted via the chain 31. The first idler 32
It consists of a sprocket with twice the number of teeth that has twice the number of teeth of the crank gear 5a, and reduces the rotation of the crankshaft 5 by half through the first chain 31 wound between it and the crank gear 5a. To do. The first idler 32 is attached to the offset portion 30 of the one bank end surface 2a.
It is provided at a position retracted from the other bank end surface 2a.

The first idler 32 is coaxially and integrally provided with a second idler 34 which transmits the decelerated rotation to the four intake and exhaust cam shafts 3 and 4 through the second chain 33. There is. The second idler 34 is the first idler 32.
Is attached to the intake / exhaust cam shaft 3, by a predetermined amount from the offset portion 30.
4 are located so as to be flush with the drive sprockets 3a, 4a. The second idler 34 is composed of sprockets having the same number of teeth as the sprockets 3a, 4a of the intake / exhaust cam shafts 3, 4, and the rotation of the crankshaft 5 decelerated by 1/2 is directly transferred to the intake / exhaust cam shafts 3, 4. It is something to convey.

The first and second chains 31 and 33 are provided with a chain guide 36 and a chain tensioner 37, respectively. In addition, the second chain 33,
V by the idler 38 provided in the valley of the V-shaped bank
It is deflected in a letter shape. In this embodiment, in order to transmit the rotation of the crankshaft 5 to the intake / exhaust camshafts 3, 4, the chains 31, 33 & the sprockets 5a, 32, 34,
Although 3a and 4a are used, it goes without saying that a belt & pulley or a stepped belt & stepped pulley or the like may be used instead.

The operation of this embodiment having the above configuration will be described.

The rotation of the crankshaft 5 is caused by the rotation of the first chain 31.
Is transmitted to the large-diameter first idler 32 via the second chain 33 from the small-diameter second idler 34 integrally provided on the first idler 32, and the intake / exhaust of the left and right banks 2 is performed. It is transmitted to the cam shafts 3 and 4.

Since the first idler 32 and the second idler 34 are provided in the offset portion 30 formed by pulling one bank end face 2a from the other bank end face 2b, a conventional dead space is provided. The space of the offset unit 30 is effectively used. That is, the position of the first chain 31 can be determined based on the No. 2 bore position of the bank 2 on the offset portion 30 side. Therefore, the amount of protrusion 39 from the engine end portion 17 in the crankshaft direction becomes small, and the total length of the engine can be suppressed.

Further, the intake and exhaust cam shafts 3 of the left and right banks 2,
Since the rotation that has already been decelerated by the large-diameter first idler 32 is transmitted to 4, the drive wheel diameters 3, a, 4a (sprocket diameter and pulley diameter) of the intake and exhaust cam shafts 3, 4 can be reduced. Therefore, the sprockets 3a, 4a of the intake / exhaust cam shafts 3, 4 respectively provided on the upper portions of the left and right banks 2 can be brought close to each other, and the valve holding angle can be reduced to achieve a compact combustion chamber. Also, the overall width of the engine can be reduced.

Further, since only two chains, the first and second chains 31 and 33, are required to drive the camshaft, three or four chains are used. The number of parts including accessory parts such as 37 and guide 36 can be reduced, resulting in low cost.

[0023]

As described above, the "V-type engine camshaft drive device" according to the present invention can exhibit the following excellent effects.

(1) The overall length and width of the engine can be reduced.

(2) A compact combustion chamber with a small valve holding angle can be achieved.

(3) Since the number of parts is small, the cost is low.

[Brief description of drawings]

FIG. 1 is a schematic view of a camshaft drive device for a V-type engine showing an embodiment of the present invention, (a) is a plan view and (b) is a front view.

FIG. 2 is a schematic view of a camshaft drive device for a V-type engine showing a conventional example, (a) is a plan view and (b) is a front view.

3A and 3B are schematic diagrams of a camshaft driving device for a V-type engine showing another conventional example, FIG. 3A being a plan view and FIG. 3B being a front view.

4A and 4B are schematic diagrams of a camshaft drive device for a V-type engine showing still another conventional example, in which FIG. 4A is a plan view and FIG. 4B is a front view.

[Explanation of symbols]

 2 bank 2a end face of one bank 2b end face of the other bank 3 intake camshaft 4 exhaust camshaft 5 crankshaft 30 offset part 31 first chain 32 first idler 33 second chain 34 second idler

Claims (1)

[Claims] 1. A camshaft drive for a V-type engine, wherein intake and exhaust camshafts are provided respectively above the left and right banks arranged in a V-shape, and the rotation of the crankshaft is transmitted to these intake and exhaust camshafts via a chain or the like. In the device, the left and right banks are offset from each other in the crankshaft direction, and an end face of one bank is pulled in from an end face of the other bank to form an offset portion, and the crankshaft is rotated by a chain or the like through the offset portion. Is provided with a large-diameter first idler that is decelerated and transmitted, and a second idler that transmits rotation to the intake / exhaust cam shaft via a chain or the like is integrally provided on the first idler. A camshaft drive for V-type engine.