JP2015094217A - Transmission structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission structure of an internal combustion engine capable of reducing resultant force of transmission belt tension generated by cam driving torque for all cylinders generated on a crankshaft.SOLUTION: A transmission structure of an internal combustion engine 1 includes a first transmission belt 71 laid between a crankshaft 3 and an intermediate shaft 4, a second transmission belt 72 laid between the intermediate shaft 4 and a camshaft 5 on one bank, and a third transmission belt 73 laid between the intermediate shaft 4 and a camshaft 6 on the other bank, and the camshafts 5 and 6 are rotated at a 1/2 rotation speed of the crankshaft 3. A gear ratio between the crankshaft 3 and the intermediate shaft 4 is larger than a gear ratio between the intermediate shaft 4 and the camshafts 5 and 6.

Description

  The present invention relates to a transmission structure of an internal combustion engine.

  2. Description of the Related Art Conventionally, in an internal combustion engine, there is a transmission structure for a V-type four-cylinder engine in which a first chain is hung between a crankshaft and an intermediate shaft, and a second chain and a third chain are hung between a camshaft of each bank It is known (see, for example, Patent Document 1).

  Patent Document 1 does not disclose the respective gear ratios between the shafts. Usually, in a V-type internal combustion engine, the transmission ratio of the first chain is set to be smaller than the transmission ratio of the second and third chains, and a large deceleration is performed between the crankshaft and the intermediate shaft. . For this reason, the conventional V-type internal combustion engine has a structure in which an excessive load is applied to the first chain between the crankshaft and the intermediate shaft.

JP-A-4-75364

  However, when the gear ratio is set as described above as in the conventional internal combustion engine described in Patent Document 1, the tension of the transmission band (chain) generated by the cam drive torque around the crankshaft. There was a problem that became excessive.

  Therefore, the present invention was devised to solve the above-described problems, and is an internal combustion engine that can reduce the resultant force of transmission band tension generated by cam drive torque for all cylinders generated on the crankshaft. It is an object to provide a transmission structure.

The transmission structure of the internal combustion engine according to the present invention includes a first transmission band hung between a crankshaft and an intermediate shaft of the internal combustion engine, and a first transmission band hung between the intermediate shaft and the camshaft of one bank. An internal combustion engine having two transmission bands and a third transmission band hung between the intermediate shaft and the cam shaft of the other bank, wherein the cam shaft rotates at half the rotational speed of the crankshaft In this transmission structure, the transmission gear ratio between the crankshaft and the intermediate shaft is larger than the transmission gear ratio between the intermediate shaft and the camshaft.
Here, the gear ratio (reduction ratio) is the ratio of the rotational speed of the driven shaft to the rotational speed of the driving shaft, and is the rotational speed of the intermediate shaft when the rotational speed of the crankshaft is 1. In other words, a large gear ratio means that the value of the gear shift is large and the change in the speed of the drive shaft and the driven shaft is small.

  According to this configuration, the transmission structure of the internal combustion engine includes the first transmission band that is hung on the crankshaft and the intermediate shaft, the second transmission band that is hung on the intermediate shaft and the camshaft of one bank, and the intermediate shaft. And the third transmission band hung on the camshaft of the other bank, so that the tension applied to the entire transmission band can be divided into three parts. Can also be reduced. Further, the transmission structure of the internal combustion engine prevents the rotational speed of the intermediate shaft from being greatly decelerated because the speed ratio between the crankshaft and the intermediate shaft is larger than the speed ratio between the intermediate shaft and the camshaft. be able to.

  The intermediate shaft preferably drives a water pump.

  According to this configuration, since the intermediate shaft has a large gear ratio with the crankshaft, the water pump can be driven at a high speed while suppressing a change in the speed of the intermediate shaft with respect to the crankshaft, so that the water pump can be reduced in size. .

  The present invention can provide a transmission structure of an internal combustion engine that can reduce the resultant force of transmission band tension generated by cam drive torque for all cylinders generated on a crankshaft.

It is a principal part schematic perspective view which shows the arrangement | positioning state of the transmission structure of the internal combustion engine which concerns on embodiment of this invention. It is a principal part schematic front view of the internal combustion engine which shows the attachment state of a transmission belt case. It is a principal part schematic front view of the internal combustion engine which removed the transmission belt case. It is explanatory drawing which shows the tension state of each transmission belt. FIG. 3 is an enlarged sectional view in the XX line direction of FIG. 2. (A) is a graph which shows the change of the drive torque of a 1st bank, (b) is a graph which shows the change of the drive torque of a 2nd bank. (A) is a graph which shows the change of the drive torque of each bank, (b) is a graph which shows the synthetic | combination torque which synthesize | combined the drive torque of each bank.

With reference to FIGS. 1-7, the transmission structure of the internal combustion engine which concerns on embodiment of this invention is demonstrated. The transmission structure of the internal combustion engine 1 according to the present invention can be applied to whether the internal combustion engine 1 is placed horizontally or vertically. Hereinafter, a case where the engine 1 is placed vertically will be described as an example.
In the embodiment of the present invention, the direction in which the crankshaft 3, the intermediate shaft 4 and the camshafts 5 and 6 shown in FIG. 1 extend is the front-rear direction, the direction orthogonal thereto is the left-right direction, the vertical upper side and the vertical lower side. It demonstrates as a vertical direction.

≪Internal combustion engine≫
As shown in FIG. 1, the internal combustion engine 1 is a V-type multi-cylinder (6-cylinder) four-cycle engine, and is arranged vertically, for example, at the rear of a vehicle body. The internal combustion engine 1 has an internal combustion engine body 2 having a pair of left and right first banks 2a and 2b that are formed in a V shape with respect to each other at an angle of approximately 90 ° when viewed from the direction of the crankshaft 3. ing. The first bank 2a and the second bank 2b are each provided with a valve operating mechanism (not shown). In the internal combustion engine 1, the second bank 2 b on the left side is slightly shifted from the first bank 2 a on the right side and is offset in the front-rear direction.

<Internal combustion engine body>
As shown in FIGS. 2 and 3, the internal combustion engine body 2 includes a cylinder block 21, left and right cylinder heads 22, 22, left and right head covers 23, 23, a crankcase 24, a transmission band case 8, and a bearing. The holder 84, the crankshaft 3, the intermediate shaft 4, the camshafts 5 and 6, the oil pump shaft OPa, and the transmission band 7 are provided.
As shown in FIG. 1, the internal combustion engine body 2 is provided with a crankshaft 3, an intermediate shaft 4, camshafts 5 and 6, and an oil pump shaft OPa in parallel along the front-rear direction.
As shown in FIG. 3, a flange portion 2 c is formed on the front side wall of the internal combustion engine main body 2 so as to surround a transmission band mechanism including four transmission bands 7. A transmission band case 8 is bolted to the flange portion 2c.

<Cylinder block>
As shown in FIG. 2, the cylinder block 21 is mounted on the upper joint surfaces of the upper left and right first banks 2a and 2b (see FIG. 1) so that the cylinder heads 22 and 22 form a V-shape. It has been. As shown in FIG. 3, between the joint surfaces of the cylinder block 21 and the crankcase 24, a crankshaft 3 having a crankshaft drive wheel 31 is rotatably supported via a bearing. An intermediate shaft 4 is pivotally supported at the upper central portion of the cylinder block 21 between the left and right first banks 2a and second banks 2b (see FIG. 1). The cylinder block 21 forms a lower side in the cylinder axial direction of a combustion chamber (not shown), and three cylinders 21b are respectively provided at predetermined intervals in the cam shafts 5 and 6 on the lower side in the cylinder axial direction (see FIG. 1). Is formed.

<Cylinder head>
As shown in FIG. 2, head covers 23 and 23 are attached on the pair of left and right cylinder heads 22 and 22. Each cylinder head 22 forms an upper side in the cylinder axial direction of a combustion chamber (not shown), and three cylinders (not shown) are formed at predetermined intervals in the cam shaft direction on the upper side in the cylinder axial direction. Yes.
An intake / exhaust system (not shown) of the internal combustion engine 1 is attached to the cylinder heads 22 and 22. That is, as shown in FIG. 1, intake camshafts 51 and 61 and exhaust camshafts 52 and 62 are disposed on the left and right sides of the cylinder head 22, respectively.

<Head cover>
As shown in FIG. 2, the head covers 23 and 23 are respectively attached to the upper sides of the left and right cylinder heads 22 and 22. As shown in FIG. 3, intake camshafts 51 and 61 and exhaust camshafts 52 and 62 are disposed via bearings at the connecting portions between the cylinder heads 22 and 22 and the head covers 23 and 23. The intake camshaft driven wheels 53 and 63 and the exhaust camshaft driven wheels 54 and 64 are attached to the front end portions of the intake camshafts 51 and 61 and the exhaust camshafts 52 and 62. A second transmission band 72 and a third transmission band 73 are wound around the intake camshaft driven wheels 53 and 63 and the exhaust camshaft driven wheels 54 and 64. On the front side surfaces of the head covers 23, 23 and the cylinder heads 22, 22 are a second transmission band case 82 and a third transmission band case 83 that cover the intake camshaft driven wheels 53, 63 and the exhaust camshaft driven wheels 54, 64. Is attached.

<Crankcase>
As shown in FIG. 3, the crankcase 24 is attached to the lower surface of the cylinder block 21. The crankcase 24 is supported by a crankshaft 3 provided with a crankshaft drive wheel 31 and an oil pump shaft OPa provided with an oil pump shaft driven wheel OPb for driving an oil pump (not shown). . On the front side wall of the internal combustion engine body 2, a rib 24 a extending from the lower end of the flange portion 2 c toward the upper side in the lower portion of the flange portion 2 c of the crankcase 24, and the rib 24 a and the flange An oil suction port 24b formed between the portion 2c and the portion 2c is formed. The internal combustion engine 1 is composed of a dry sump lubrication system having no oil pan at the lower end.

<Power transmission case>
As shown in FIG. 2, the transmission band case 8 includes a first transmission band 71, a second transmission band 72, a third transmission band 73, and a fourth transmission band shown in FIG. 1 disposed on the front side wall of the internal combustion engine body 2. 74 is a cover member covering 74 and the like. The transmission band case 8 is divided into three members, a first transmission band case 81, a second transmission band case 82, and a third transmission band case 83, and an internal combustion engine with a liquid sealant (not shown) interposed therebetween. It is bolted to the flange portion 2 c of the engine body 2. The transmission band case 8 is made of, for example, aluminum.

A first transmission band case 81 shown in FIG. 2 is a cover member that covers the periphery of the first transmission band 71 and the fourth transmission band 74 mainly on the front side surfaces of the cylinder block 21 and the crankcase 24. The first transmission band case 81 has a holder installation hole 81a and a viewing window 81b. The first transmission band case 81 is disposed across the cylinder block 21 and the crankcase 24 and is bolted thereto.
A bearing holder 84 that closes the holder installation hole 81a and a maintenance cover member 85 that closes the viewing window 81b are bolted to the front surface of the first transmission band case 81.

<Bearing holder>
As shown in FIG. 5, the bearing holder 84 is a lid-like retainer that closes the holder installation hole 81 a of the first transmission band case 81. The bearing holder 84 is integrally formed with a bearing mounting portion 84a that holds the outer ring of the bearing BR1 in which the inner ring is press-fitted into the front end portion of the intermediate shaft 4. The bearing holder 84 is bolted to the holder installation hole 81 a of the first transmission band case 81 via an O-ring O. At that time, the bearing BR1 is attached to the bearing holder 84 in a state where the outer ring is attached to the bearing attachment portion 84a and the inner ring is press-fitted into the front end portion of the intermediate shaft 4. The bearings BR1 and BR2 are press-fitted into the intermediate shaft 4, respectively. The bearing holder 84 is attached so as to cover the outer peripheral portion on the front end side of the bearing BR1 and holds the bearing BR1. In this case, since the bearing holder 84 is formed of cast iron having excellent vibration absorption, it has a vibration damping effect. Therefore, the vibration and sound propagation to the outside of the first transmission band case 81 and the internal combustion engine 1 are achieved. Is suppressed.

  As shown in FIG. 2, the maintenance cover member 85 is formed around the bearing holder 84 arranged on the front end side of the intermediate shaft 4 and the reduction wheel 41 (see FIG. 5) in the first transmission band case 81. This is a lid member for closing the observation window 81b. The observation window 81b is used to visually check the state of the adjuster mechanism T2a (see FIG. 3) that adjusts the extension allowance of the second tensioner T2. In addition, the viewing window 81b includes a first transmission band 71 wound around the crank reduction wheel 41a shown in FIG. 5, a second transmission band 72 wound around the cam shaft driving wheel 41b, and a cam shaft driving wheel 41c. It is also possible to visually check the installation state of the third transmission band 73 wound around the chain support arm 9 and the chain support arm 9 that holds the reduction wheel 41.

  The left and right second transmission band case 82 and the third transmission band case 83 shown in FIG. 2 mainly surround the periphery of the VTC mechanism attached to the front side of the intake camshafts 51 and 61 and the exhaust camshafts 52 and 62. It is the cover member which covers (refer FIG. 3). The second transmission band case 82 and the third transmission band case 83 are disposed on the front side wall of the internal combustion engine body 2 so as to straddle the left and right cylinder heads 22 and the head cover 23 and are bolted to each other.

<Crankshaft>
As shown in FIG. 3, the crankshaft 3 is rotatably supported via a bearing between the joint surfaces of the cylinder block 21 and the crankcase 24. Crankshaft drive wheels 31 and 31 are attached to the front end portion of the crankshaft 3. A first transmission band 71 and a fourth transmission band 74 are wound around the crankshaft drive wheels 31, 31, respectively. The crankshaft drive wheel 31 is composed of a sprocket with 24T teeth.

<Intermediate shaft>
As shown in FIG. 5, the intermediate shaft 4 is a shaft for driving the water pump WP, and is supported by the cylinder block 21 via bearings BR1, BR2, the water pump WP, and the like. A reduction wheel 41 is press-fitted and fixed to the intermediate shaft 4. The speed reduction wheel 41 is integrally formed with three sprockets of a crank speed reduction wheel 41a, a cam shaft driving wheel 41b, and a cam shaft driving wheel 41c.

  As shown in FIG. 4, the crank reduction wheel 41a includes a crankshaft drive wheel 31, a crank reduction wheel 41a, and a first transmission belt 71 wound around the crankshaft drive wheel 31 and the crank reduction wheel 41a. A first-stage reduction mechanism 7A is configured. The first-stage reduction mechanism 7A includes a crankshaft drive wheel 31 made of a sprocket with 24T teeth, a crank reduction wheel 41a made of a sprocket with 32T teeth, and a first transmission band 71. As a result, the gear ratio at which the crank reduction wheel 41a is decelerated with respect to the crankshaft drive wheel 31 is 0.75.

  According to this configuration, the crank reduction wheel 41a has a gear ratio of 0.75 for reducing the rotation of the crankshaft drive wheel 31, and when the crankshaft 3 makes one rotation, the intermediate shaft 4 is 0.75. Rotate. Thus, since the intermediate shaft 4 is not greatly decelerated with respect to the crankshaft 3, the water pump WP (see FIG. 5) can be rotated at a relatively high rotational speed.

  The camshaft drive wheel 41b and the camshaft drive wheel 41c are sprockets having 24T teeth. In other words, the crank speed reduction wheel 41a and the camshaft drive wheels 41b and 41c provided on the intermediate shaft 4 avoid the same number in order to suppress resonance, and the number of teeth of the crank speed reduction wheel 41a is 32T, and the left and right cams The number of teeth of the shaft drive wheels 41b and 41c is 24T.

  As shown in FIG. 5, the water pump WP is a pump for supplying cooling water to a water jacket 21a and the like formed in the cylinder block 21 and the like. The water pump WP is attached to the rear portion of the reduction wheel 41 on the intermediate shaft 4 via a bearing BR2, and is driven to rotate by the intermediate shaft 4. The outer periphery of the water pump WP is attached to the cylinder block 21 via a plurality of O-rings O. The water pump WP has a drain hole WPa.

<Camshaft>
As shown in FIGS. 3 and 4, the cam shafts 5 and 6 have left and right cam pieces (not shown) that open and close valves (intake valves and exhaust valves) (not shown) that perform intake and exhaust in the combustion chamber. A pair of axes. The left and right camshafts 5 and 6 include intake camshafts 51 and 61 having intake camshaft driven wheels 53 and 63, and exhaust camshafts 52 and 62 having exhaust camshaft driven wheels 54 and 64, respectively. The two shafts are respectively configured. The camshafts 5 and 6 (the intake camshafts 51 and 61 and the exhaust camshafts 52 and 62) include a plurality of cam holders (not shown) arranged at predetermined intervals along the camshafts 5 and 6. And is rotatably supported by the internal combustion engine main body 2.

  The cam holder (not shown) is a bearing member for pivotally supporting the intake camshafts 51 and 61 and the exhaust camshafts 52 and 62 with respect to the internal combustion engine main body 2. The cam holders are arranged in two rows at appropriate intervals along the left and right intake camshafts 51 and 61 and the exhaust camshafts 52 and 62 on the upper side of the cylinder head 22 in the cylinder axis direction.

  As shown in FIG. 4, the intake camshaft driven wheel 53 and the exhaust camshaft driven wheel 54 of the first bank 2a on the right side include the intake camshaft driven wheel 53, the exhaust camshaft driven wheel 54, The camshaft drive wheels 41b and the second transmission band 72 wound around them constitute a second-stage reduction mechanism 7B. The second-stage reduction mechanism 7B includes a camshaft drive wheel 41b of a sprocket having a number of teeth of 24T, an intake camshaft driven wheel 53 and an exhaust camshaft driven wheel of a sprocket having a number of teeth of 36T, And the transmission band 72, the gear ratio of the intake camshaft driven wheel 53 and the exhaust camshaft driven wheel 54, which decelerates against the rotation of the camshaft drive wheel 41b of the intermediate shaft 4, is 0. 666.

  The intake camshaft driven wheel 63, the exhaust camshaft driven wheel 64 and the third transmission band 73 of the left second bank 2b are the intake camshaft driven wheel 53 and exhaust cam of the right first bank 2a. With respect to the shaft driven wheel 54 and the second transmission band 72, they are arranged symmetrically about the cam shaft driving wheels 41b and 41c, and are rotationally driven in the same clockwise direction when viewed from the front. Intake camshaft driven wheel 63, exhaust camshaft driven wheel 64, crank reduction wheel 41a, second transmission band 72 wound around them, and second-stage deceleration The mechanism 7C is configured. The second stage reduction mechanism 7C of the second bank 2b includes a camshaft drive wheel 41c of a sprocket having a number of teeth of 24T, an intake camshaft driven wheel 53 and an exhaust camshaft driven wheel of a sprocket having a number of teeth of 36T. 54 and the third transmission band 73, the intake camshaft driven wheel 63 and the exhaust camshaft driven wheel 64 are decelerated and rotated with respect to the rotation of the camshaft drive wheel 41c of the intermediate shaft 4. The gear ratio is 0.666.

  For this reason, the left and right camshafts 5 and 6 including the intake camshaft driven wheels 53 and 63 and the exhaust camshaft driven wheels 54 and 64 are connected to the first-stage reduction mechanism 7A and the second-stage reduction mechanism. 7B and 7C are configured to rotate at a reduced speed at half the rotational speed of the crankshaft 3. Further, the transmission ratio (0.75) between the crankshaft 3 and the intermediate shaft 4 is larger than the transmission ratio (0.66) between the intermediate shaft 4 and the camshafts 5 and 6. The valve gear provided in the internal combustion engine 1 is configured to decelerate the rotation of the crankshaft 3 by the first-stage decelerating mechanism 7A and the second-stage decelerating mechanisms 7B and 7C to thereby reduce the intake camshaft 51. 61 and the exhaust camshafts 52 and 62 are rotated at a low speed.

As shown in FIG. 1, intake camshaft driven wheels 53 and 63 and exhaust camshaft driven wheels 54 and 64 are provided on the outer periphery of a cylindrical VTC (variable valve timing mechanism) and a VCT housing. And a cam sprocket.
The right intake camshaft driven wheel 53 and the exhaust camshaft driven wheel 54 have cam sprockets provided on the rear end side of the outer peripheral surface of the VTC.
The left intake camshaft driven wheel 63 and the exhaust camshaft driven wheel 64 have cam sprockets provided on the front end side of the outer peripheral surface of the VTC.

<Oil pump shaft>
The oil pump shaft OPa shown in FIG. 3 is a shaft for driving an oil pump (not shown). The oil pump shaft OPa is provided with an oil pump shaft driven wheel OPb around which a fourth transmission band 74 is wound on the front end side, and an oil pump (not shown) for circulating lubricating oil is provided on the rear end side. Is provided.

<Driving belt>
The transmission band 7 is composed of an endless chain or an endless belt. On the front wall side of the internal combustion engine body 2, four transmission bands 7 including a first transmission band 71, a second transmission band 72, a third transmission band 73, and a fourth transmission band 74 are arranged. Hereinafter, the case where the transmission band 7 is a chain will be described as an example.

<First transmission belt>
As shown in FIG. 4, the first transmission band 71 is hung on the crankshaft drive wheel 31 of the crankshaft 3 and the crank reduction wheel 41 a of the intermediate shaft 4, so that the first stage of rotation of the crankshaft 3 is performed. It constitutes a part of a speed reduction mechanism 7A that performs deceleration and transmits. Between the crankshaft 3 and the intermediate shaft 4, on the left and right outer sides of the first transmission band 71, there are a first tensioner T1 for guiding the first transmission band 71 and an adjuster mechanism T2a for taking looseness of the first transmission band 71. And a second tensioner T2 having the second tensioner. The second tensioner T2 having the adjuster mechanism T2a has a function of guiding the first transmission band 71 and adjusting the slack of the first transmission band 71.

<Second transmission band>
The second transmission band 72 is hung on the camshaft drive wheel 41b of the intermediate shaft 4 and the intake camshaft driven wheel 53 and the exhaust camshaft driven wheel 54 of each camshaft 5 of the first bank 2a. A part of a speed reduction mechanism 7B that transmits by performing the second speed reduction of the rotation of the shaft 4 is constituted. On the outer periphery of the second transmission band 72, a third tensioner T3 having an adjuster mechanism T3a that takes looseness of the second transmission band 72, a fourth tensioner T4 and a fifth tensioner T5 that guide the second transmission band 72, Is arranged. The third tensioner T3 having the adjuster mechanism T3a has a function of guiding the second transmission band 72 and adjusting the slack of the second transmission band 72.
As shown in FIG. 1, in the second transmission band 72 on the first bank 2a side, the second bank 2b on the left side is slightly shifted to the front side with respect to the first bank 2a on the right side. The third transmission band 73 on the second bank 2b side is arranged offset to the rear side.

<Third transmission band>
As shown in FIG. 4, the third transmission band 73 includes a camshaft drive wheel 41c of the intermediate shaft 4, an intake camshaft driven wheel 63 and an exhaust camshaft driven wheel 64 of each camshaft 6 of the second bank 2b. The speed reduction mechanism 7C is configured to reduce the speed of the second stage of rotation of the intermediate shaft 4 and transmit it. The second transmission band 72 and the third transmission band 73 are composed of endless chains having the same length, are arranged symmetrically to each other, and are driven in the same clockwise direction when viewed from the front. On the outer peripheral portion of the third transmission band 73, an eighth tensioner T8 having a sixth tensioner T6 and a seventh tensioner T7 for guiding the third transmission band 73 and an adjuster mechanism T8a for removing the looseness of the third transmission band 73 is disposed. Has been. The eighth tensioner T8 having the adjuster mechanism T8a has a function of guiding the third transmission band 73 and adjusting the slack of the third transmission band 73.

<4th transmission band>
As shown in FIG. 4, the fourth transmission band 74 is hung on the crankshaft drive wheel 31 of the crankshaft 3 and the oil pump shaft driven wheel OPb of the oil pump shaft OPa to drive an oil pump (not shown). The power transmission mechanism is configured. On the outer periphery of the fourth transmission band 74, a ninth tensioner T9 having an adjuster mechanism T9a that takes looseness of the fourth transmission band 74 and a tenth tensioner T10 that guides the fourth transmission band 74 are arranged. . The ninth tensioner T9 having the adjuster mechanism T9a has a function of guiding the fourth transmission band 74 and adjusting the slack of the fourth transmission band 74.

≪Action≫
Next, the operation of the transmission structure of the internal combustion engine 1 according to the embodiment of the present invention will be described with reference to FIGS.

  When the internal combustion engine 1 is started and the crankshaft 3 shown in FIG. 4 rotates, this rotation is transmitted via the crankshaft drive wheel 31, the first transmission band 71, and the crank reduction wheel 41a of the first-stage reduction mechanism 7A. Is transmitted to the intermediate shaft 4. The rotation of the crankshaft 3 has a gear ratio of 0.75 with respect to the rotation of the crankshaft drive wheel 31 because the number of teeth of the crankshaft drive wheel 31 is 24T and the number of teeth of the crank reduction wheel 41a is 32T. The crank reduction wheel 41a is decelerated and transmitted.

In this case, the resistance torque of the crank reduction wheel 41a that is rotated by the crankshaft drive wheel 31 is 32T compared to the number of teeth 24T of the crankshaft drive wheel 31 and the number of teeth is relatively large. Since the ratio is also 0.75, the rate of deceleration is small. For this reason, the load concerning the 1st transmission belt 71 at this time can be made comparatively small. When the gear ratio (reduction ratio) is large, a large force is required for the crankshaft 3 (drive shaft) to move the intermediate shaft 4 (driven shaft). The large force is the tension (load) of the transmission band 7.
As the crank reduction wheel 41a rotates, the water pump WP (see FIG. 5) and the cam shaft drive wheels 41b and 41c provided on the same intermediate shaft 4 rotate at the same relatively high rotational speed as the intermediate shaft 4.

  In this way, the first-stage reduction mechanism 7A can drive the water pump WP (see FIG. 5) at high speed, so that the pump performance can be improved, so the water pump WP (see FIG. 5). Can be miniaturized.

  When the camshaft drive wheels 41b and 41c rotate, this rotation is caused through the intake camshaft driven wheels 53 and 63 and the exhaust camshaft driven wheels 54 and 64 of the left and right second stage reduction mechanisms 7B and 7C. This is transmitted to the intake camshafts 51 and 61 and the exhaust camshafts 52 and 62. The rotation of the intake camshafts 51 and 61 and the exhaust camshafts 52 and 62 is such that the camshaft drive wheels 41b and 41c have 24T teeth, the intake camshaft driven wheels 53 and 63, and the exhaust camshaft driven wheels 54. 64, the number of teeth is 36T, so that the intake camshaft driven wheels 53 and 63 and the exhaust camshaft driven wheels 54 and 64 have a gear ratio of 0.66 with respect to the rotation of the intermediate shaft 4. It is decelerated and rotated more greatly than the first stage reduction mechanism 7A. As a result, the camshafts 5 and 6 rotate at a low speed to drive the valves.

  FIG. 6 is a graph showing a change in cam torque of one cycle 720 degrees per cylinder generated by the valve lift of the cams of the camshafts 5 and 6, and (a) shows a change in the drive torque of the first bank 2a. (B) shows the change in the driving torque of the second bank 2b.

  When each of the cam shafts 5 and 6 rotates, cam torque is generated by the valve lift of each cam, as shown in FIGS. 6 (a) and 6 (b). Curves d and f including thick wavy lines, thin wavy lines, thick two-dot chain lines, and fine two-dot chain lines indicate cam lift curves for each cylinder. Curves e and g indicated by bold solid lines indicate the cam torque based on the cam waveform of each cam lift. Torque integrated values a and b0.8 are applied to the left and right first banks 2a and 2b, respectively, every 720 degrees in one cycle. The left and right second transmission bands 72 and the third transmission band 73 share the applied torque integral value a by 0.8, so that a large load is not applied even at a large reduction ratio.

  Load fluctuation on the cam shafts 5 and 6 side due to the cam torque is transmitted to the second transmission band 72 and the third transmission band 73 of the first bank 2a and the second bank 2b. In the second transmission band 72 and the third transmission band 73, as indicated by cam torque curves e and g, tension and loosening are applied to the tension side at three timings for one cycle of the internal combustion engine 1. The movement of the second transmission band 72 and the third transmission band 73 is guided by the third tensioner T3, the fourth tensioner T4, the fifth tensioner T5, the sixth tensioner T6, the seventh tensioner T7, and the eighth tensioner T8. The tension and the looseness are adjusted by the adjuster mechanism T3a and the adjuster mechanism T8a.

  FIG. 7A is a graph showing changes in the driving torque h of the first bank 2a and changes in the driving torque i of the second bank 2b. FIG. 7B shows the driving torque h of the first bank 2a. It is a graph which shows the synthetic | combination torque j which synthesize | combined the drive torque i of the 2nd bank 2b.

  As shown in FIG. 7A, relative torque is generated in a symmetrical cycle between the driving torque h of the first bank 2a and the driving torque i of the second bank 2b. Therefore, in the intermediate shaft 4 to which the combined torque j of the driving torque h of the first bank 2a and the driving torque i of the second bank 2b is applied, the torques cancel each other as shown in FIG. The intermediate shaft 4 is applied with a torque integral value c1.6 obtained by adding the torque integral value a for each cycle 720 degrees of the first bank 2a and the torque integral value b for each cycle 720 degrees of the second bank 2b. .

Therefore, between the crankshaft 3 and the intermediate shaft 4, the load on the crankshaft 3, that is, the load on the first transmission band 71 is reduced by a small reduction ratio, and a large load (driving force) is required.
In other words, the left and right second transmission bands 72 and the third transmission band 73 are intermediate at the timing when the torque peaks of the second and third transmission bands 72 and 73 due to cam torque fluctuations of the left and right camshafts 5 and 6 cancel each other. Although applied to the axis 4, the absolute value of the torque (the base of the torque waveform) is shifted to the positive side of the vertical axis, so that the integral value c is generated. In the present invention, the integral value c does not adversely affect the transmission band 7. For this reason, the fluctuation | variation by the tensile force loaded on the intermediate shaft 4 can be reduced.

  As a result, it is possible to reduce the transmission of the vibration due to the load fluctuation of the transmission band tension from the intermediate shaft 4 shown in FIG. 5 to the peripheral members such as the bearing holder 84 and the water pump WP disposed around the intermediate shaft 4. Can do. In particular, since the bearing holder 84 is made of cast iron, it has an excellent vibration damping effect. Thereby, the reliability of the internal combustion engine 1 can be improved.

  Further, in the transmission structure of the internal combustion engine 1, the transmission ratio (0.75) between the crankshaft 3 and the intermediate shaft 4 is greater than the transmission ratio (0.66) between the intermediate shaft 4 and the camshafts 5 and 6. By being large, the ratio of the load applied to the first transmission band 71 by the crankshaft 3 can be made smaller than the ratio of the load applied to the second transmission band 72 and the third transmission band 74.

Further, as shown in FIG. 5, the intermediate shaft 4 is arranged from the rear side in the order of the crank reduction wheel 41a, the camshaft drive wheel 41b, and the camshaft drive wheel 41c. A band 72 and a third transmission band 73 (chain) are wound around. As shown in FIG. 1, the right intake camshaft driven wheel 53 and the exhaust camshaft driven wheel 54 around which the second transmission band 72 is wound are arranged with the cam sprocket on the rear side and the VTC on the front side. . The left intake camshaft driven wheel 63 and the exhaust camshaft driven wheel 64 around which the third transmission band 73 is wound are disposed with the cam sprocket on the front side and the VTC on the rear side.
In this way, according to the present invention, the intake camshaft driven wheel of the right second bank 2b is arranged in accordance with the VTC arrangement direction of the intake camshaft driven wheel 53 and the exhaust camshaft driven wheel 54 of the right first bank 2a. 63 and the exhaust camshaft driven wheel 64 are arranged in the direction opposite to the VTC arrangement direction. Therefore, in the internal combustion engine 1, as viewed from the side, the VTC on the right camshaft 5 and the VTC on the left camshaft can be arranged so as to overlap each other in the axial direction. The internal space engine 1 can be downsized in the axial direction by reducing the occupied space by the amount.
In this case, the intermediate shaft 4 has a force that tilts the front side of the intermediate shaft 4 upward by the second transmission band 72 and the third transmission band 73, but both ends of the intermediate shaft 4 are supported by the bearings BR1 and BR2. Therefore, it is kept in a stable state.

Further, according to the deceleration setting of the present embodiment, when the first transmission band 71 is extended and a shift of 1 degree occurs, the camshafts 5 and 6 can be suppressed to a shift of 0.66 degrees. .
Further, since the gear ratio between the crankshaft 3 and the intermediate shaft 4 is larger than the gear ratio between the intermediate shaft 4 and the camshafts 5 and 6, compared with the case where the magnitudes of both gear ratios are reversed, The load (elongation) of the first transmission band 71 can be reduced. Thereby, the shift | offset | difference of the cam shafts 5 and 6 can be suppressed further.

  The present invention is not limited to the above-described embodiment, and various modifications and changes can be made within the scope of the technical idea. The present invention extends to these modifications and changes. Of course.

In the embodiment, as an example of the transmission structure of the internal combustion engine 1, each transmission band 7 made of a chain, the crankshaft drive wheel 31 made of a sprocket, the reduction wheel 41, the intake camshaft driven wheels 53 and 63, and the exhaust The camshaft driven wheels 54 and 64 have been described by taking the chain transmission mechanism as an example. However, the camshaft driven wheels 54 and 64 are constituted by belts such as a V belt and a toothed belt, and pulleys and gears around which these are wound. It may be a belt transmission mechanism.
In this case, the number of teeth of the gear may be formed in accordance with the number of teeth of the sprocket described in the above embodiment, or the diameter of the pulley may be formed in accordance with the number of teeth.

  Further, as an example of the internal combustion engine 1, the case where it is arranged vertically at the rear of the vehicle body has been described as an example, but the arrangement position and orientation of the vehicle body of the internal combustion engine 1 may be changed as appropriate. For example, the internal combustion engine 1 may be placed horizontally on the front side of the vehicle body.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Crankshaft 4 Intermediate shaft 5 Cam shaft of one bank 6 Cam shaft of the other bank 71 1st transmission belt 72 2nd transmission belt 73 3rd transmission belt WP Water pump

Claims (2)

A first transmission band hung between a crankshaft and an intermediate shaft of an internal combustion engine; a second transmission band hung between the intermediate shaft and a camshaft of one bank; the intermediate shaft and the other A transmission structure of an internal combustion engine having a third transmission band hung between the camshaft of the bank and the camshaft rotating at half the rotational speed of the crankshaft;
The transmission structure of an internal combustion engine, wherein a transmission gear ratio between the crankshaft and the intermediate shaft is larger than a transmission gear ratio between the intermediate shaft and the cam shaft.   The transmission structure for an internal combustion engine according to claim 1, wherein the intermediate shaft drives a water pump.

Images