JP2004092624A - Gear mounting structure of engine crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lighten a crankshaft, to form the axial size thereof in a compact size, and to improve the mountability of an outputting gear on the crankshaft, in a four cycle engine. <P>SOLUTION: A balancer drive gear 30 is fixed as the outputting gear, between one main bearing 37 of the both ends-supported crankshaft 1 and a chain sprocket 25 formed on a crankshaft section projected from the main bearing 37 to the outside of a crank chamber. The balancer drive gear 30 has an inner circumferential spline 71 spline-fitted to the outer circumferential spline 70 of the crankshaft 1, and the inner circumferential spline 71 is formed to have the same number of teeth as the chain sprocket 25, and also formed into such a shape that the teeth of the inner circumferential spline 71 can be passed between the teeth of the chain sprocket 25 on a direction of a crank axial center. The balancer drive gear 30 makes the chain sprocket 25 pass, and is spline-fitted and fixed between the chain sprocket 25 and the main bearing 37. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gear mounting structure for a crankshaft of an engine, and more particularly to a gear mounting structure for a crankshaft suitable for a four-cycle engine in which a cam drive chain sprocket or an oil pump drive chain sprocket is formed on the crankshaft.
[0002]
[Prior art]
In addition to a primary gear (crank gear) for transmitting power to a transmission, an output gear for driving various devices mounted on the engine or a chain sprocket for output is provided on the crankshaft of the four-cycle engine. Provided as needed. For example, a balancer drive gear, a chain sprocket for driving a cam, or an oil pump / drive gear (or a chain sprocket) are provided as necessary.
[0003]
As an example of the arrangement of each output gear and chain sprocket on the crankshaft, there is an arrangement as shown in FIG. 7 (see Patent Document 1). That is, in FIG. 7, in an engine in which the crankshaft 101 is supported at both ends by a pair of main bearings 102 and 103, a primary gear 111 meshing with the clutch gear 115 is provided on a crankshaft portion protruding into the clutch chamber from one main bearing 103. Is fixed, and a chain sprocket 110 for driving a cam is fixed between the primary gear 111 and the main bearing 103 on the clutch side. In addition, the cam drive chain sprocket 110 and the primary gear 111 are integrally formed on a common boss 113, and the boss 113 is fixed to the crankshaft 101. A generator 120 is provided at a portion protruding from the other main bearing 102 into the generator chamber. However, the balancer drive gear 112 is provided between the main bearing 102 on the generator chamber side and the crank web 122, and is located in the crank chamber.
[0004]
[Patent Document 1] JP-A-2000-87714 (FIG. 2)
[0005]
[Problems to be solved by the invention]
In the case where an output chain sprocket and an output gear are juxtaposed on one protruding portion of the crankshaft, the chain sprocket 110 for cam drive and the primary gear 111 are connected to the crankshaft by a common boss 113 as shown in FIG. When the boss is fixed to the boss 101, the boss must have a large thickness for the outer diameter of the boss smaller than the tooth bottom diameter of the chain sprocket 110. Therefore, the spline diameter on the inner periphery of the boss must be reduced. The outer peripheral spline of 101 also has a small diameter, and it is difficult to secure sufficient strength and rigidity. Conversely, in order to ensure sufficient strength and rigidity, the root diameter of the chain sprocket 110 must be increased, so that a sprocket having a large number of teeth must be used. The engine becomes larger at the cam sprocket of the head.
[0006]
In addition, it takes time and labor to integrally form the teeth of the chain sprocket 110 and the primary gear 111 into the small boss 113.
[0007]
On the other hand, by integrally molding the chain sprocket with the crankshaft, it is possible to reduce the size of the engine, reduce the weight of the crankshaft, and facilitate the gear cutting process. In consideration of the above, the chain sprocket is formed on the main bearing side similarly to FIG. 7, and the output gear is fixed to the tip end side of the crankshaft.
[0008]
However, when a chain sprocket, for example, a cam drive chain sprocket is integrally formed with the crankshaft, its position is determined by overlapping the thickness of the bore, the width of the water passage, the thickness of the cam chain chamber inner side, and the gap. There is a useless space between the cam drive chain sprocket and the main bearing, the dimension of the crankshaft in the axial direction increases, and the engine becomes larger. Moreover, in recent engines, the bore tends to increase in diameter, so the useless space also increases, which contributes to increasing the size of the crankshaft in the axial direction.
[0009]
[Object of the invention]
An object of the present invention is to reduce the weight of the crankshaft and downsize the crankshaft in the center direction by devising the arrangement and shape of various output chain sprockets and output gears provided on the crankshaft. And to improve the assemblability of the output gear.
[0010]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 of the present application is directed to an output for output formed on one of a pair of main bearings that support a crankshaft at both ends and a crankshaft portion protruding out of the crank chamber from the main bearing. An output gear is fixed between a chain sprocket and an engine crankshaft.
[0011]
According to the above structure, the space between the output chain sprocket integrally formed with the crankshaft and the main bearing can be effectively used as a mounting space for the output gear, thereby reducing the weight of the crankshaft and the crankshaft of the engine. A compact size in the core direction can be achieved. Further, since the output gear can be arranged adjacent to the main bearing, the support rigidity of the output gear can be increased.
[0012]
According to a second aspect of the present invention, in the gear mounting structure for a crankshaft of the engine according to the first aspect, the output gear is spline-fitted to an outer spline formed at a gear mounting position of the crankshaft. The inner peripheral spline is formed with the same number of teeth as the chain sprocket, and is formed in a shape that allows each tooth of the inner peripheral spline to pass between the teeth of the chain sprocket in the axial direction. It is characterized by:
[0013]
According to the above structure, the diameter of the crankshaft portion between the main bearing and the output chain sprocket does not need to be larger than the outer diameter of the chain sprocket, and the output gear is moved in the axial direction to the gear mounting position. Can be inserted. Thereby, the assemblability of the output gear can be maintained while reducing the weight of the crankshaft. Further, it is not necessary to increase the size of the main bearing.
[0014]
According to a third aspect of the present invention, in the gear mounting structure for an engine crankshaft according to the first or second aspect, the output chain sprocket is a chain sprocket for driving an intake / exhaust valve cam, and the output gear is a balancer driven. It is characterized by being a gear.
[0015]
According to the above structure, even if the position of the cam drive chain sprocket is far from the main bearing in response to the increase in bore diameter, the gear assembly is maintained and the crankshaft is made compact in the direction of the crankshaft center. be able to.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
FIGS. 1 to 5 show a single-cylinder four-cycle engine to which the present invention is applied, which is mounted on, for example, a motocross motorcycle. One embodiment of the present invention will be described with reference to these drawings. For convenience of description, the description will be made assuming that the crankshaft center direction is the left-right direction.
[0017]
FIG. 1 is a schematic left side view showing an arrangement of main rotating shafts and gears in the engine. In FIG. 1, a front half of a crankcase 2 is a crank chamber 4 for accommodating a crankshaft 1, and a rear half thereof. The section is a transmission chamber 5 for accommodating a gear-type transmission, and a cylinder 6, a cylinder head 7 and a head cover 8 are sequentially fastened to the upper surface of the crank chamber 4.
[0018]
In the transmission chamber 5, a transmission input shaft 10 and a transmission output shaft 11 parallel to the crankshaft 1 are arranged at an interval in the front-rear direction, and mounted on the respective shafts 10, 11 similarly to a well-known gear type transmission. The input side transmission gear group 13 and the output side transmission gear group 14 are engaged. Although not shown, the transmission output shaft 11 is operatively connected to a propeller shaft for driving wheels or a chain transmission mechanism.
[0019]
A pair of left and right oil pump shafts 17 and 18 parallel to the crankshaft 1 are arranged below the speed change input shaft 10, and a balancer shaft 19 parallel to the crankshaft 1 is arranged at the front of the crank chamber 4. At the upper end of the head 7, a pair of camshafts 21 and 22 for driving intake and exhaust valves are arranged in parallel with the crankshaft 1.
[0020]
Chain sprockets 23 and 24 are fixed to the camshafts 21 and 22, respectively. A cam chain 26 is wound around a chain sprocket 25 for cam driving which is integrally formed with the chain sprockets 23 and 24 and the crankshaft 1. The cam drive power is output from the crankshaft 1 to the camshafts 21 and 22 via the cam chain 26. O1 is a crank shaft center, O2 is a shift input shaft center, O3 is a pump shaft center, O4 is a shift output shaft center, O5 is a balancer shaft center, and C is a cylinder center line.
[0021]
FIG. 3 is an exploded view taken along the line III-III of FIG. 1. The crankcase 2 has a left / right split structure. The crankcase members 2a and 2b are connected. Crankshaft support holes 41 and 42 are respectively formed in left and right side walls 34 and 35 of the crankcase 2, and main bearings 37 and 38 are fitted in the crankshaft support holes 41 and 42, respectively. 38 supports the crankshaft 1 at both ends.
[0022]
The crankshaft 1 also has a left-right split structure, and the left and right crankshaft members are connected by a crankpin 39. The right end of the crankshaft 1 penetrates the right main bearing 38 and protrudes into the right clutch chamber 44. The right protruding portion includes a primary gear for driving wheels made of a member separate from the crankshaft 1. 52 is fixed, and a chain sprocket 51 for driving the pump is formed integrally with the crankshaft 1 between the primary gear 52 and the right main bearing 38. The primary gear 52 is spline-fitted to the crankshaft 1 and is fixed by a circlip 53 so as not to move in the axial direction.
[0023]
The left end of the crankshaft 1 penetrates through the left main bearing 37 and protrudes into the left generator chamber 45, and the rotor 48 of the generator 47 is fixed to the left protruding end. A chain sprocket 25 for driving a cam is integrally formed with the crankshaft 1 at a portion of the crankshaft 1 between the rotor 48 and the left main bearing 37. A balancer drive gear 30 made of a member separate from the crankshaft 1 is spline-fitted. A boss 30a projecting rightward is integrally formed at the radially inner end of the balancer drive gear 30. The right end of the boss 30a abuts the left main bearing 37, and the left end of the balancer drive gear 30. Is secured by a circlip 65.
[0024]
The speed change input shaft 10 of the transmission chamber 5 is supported by the side walls 34 and 35 of the crankcase 2 via a pair of left and right bearings, and the right end protrudes into the clutch chamber 44, and the right protruding portion has a multi-plate friction. A clutch 50 is mounted.
[0025]
A clutch gear 54 is connected to a left end surface of the input side outer case 50 a of the multi-plate friction clutch 50, and the clutch gear 54 is engaged with the primary gear 52 of the crankshaft 1. A start gear 55 is formed integrally with the clutch gear 54 between the clutch gear 54 and the right side wall 35 of the crankcase.
[0026]
The balancer shaft 19 is supported by left and right side walls 34 and 35 of the crankcase 2 via a pair of left and right bearings 58 and 59. The right end of the balancer shaft 19 protrudes into the clutch chamber 44, and the right protruding portion is integrally formed with the right weight portion 19a, and the pump shaft 57 of the water pump 56 is connected via a joint mechanism. I have. A left end of the balancer shaft 19 protrudes into the generator chamber 45, and a balancer gear 29 is fixed to the left protruding portion, and the balancer gear 29 meshes with a balancer drive gear 30 of the crankshaft 1. Further, to the balancer gear 29, a left weight portion 19b formed of a member different from the balancer shaft 19 is fixed.
[0027]
FIG. 2 is an exploded cross-sectional view taken along the line II-II of FIG. 1. The engine is provided with a pair of oil pumps 15, 16. Are located. The left oil pump 15 is a scavenging pump that pumps return oil from each lubricating point in the engine to an oil tank chamber formed in a lower portion of the transmission chamber 5, and the right oil pump 16 is a scavenging pump that pumps each oil in the engine. This is a feed pump that pumps oil to the lubrication point.
[0028]
The pump shafts 17, 18 of the oil pumps 15, 16 are arranged on the same axis O3 parallel to the crank axis O1, and are connected via a joint. The right pump shaft 18 protrudes into the clutch chamber 44, and the chain sprocket 31 is fixed to the protruding portion. The chain 32 is wound over the chain sprocket 31 and the pump driving chain sprocket 51 formed on the crankshaft 1. The oil pump driving power is output from the crankshaft 1 to the oil pump shafts 17 and 18 via the chain 32.
[0029]
[Mounting structure of balancer drive gear]
FIG. 4 is a cross-sectional view showing the left end of the crankshaft 1 before the assembly with the balancer drive gear 30 removed. In the present embodiment, the balancer drive gear 30 and the cam drive at the left end of the crankshaft 1 are shown. The present invention is applied to the arrangement and mounting structure of the chain sprocket 30 for use, and will be described in detail below.
[0030]
4, the cam drive chain sprocket 25 is formed integrally with the crankshaft 1 as described above, and the position between the cam drive chain sprocket 25 and the left main bearing 37 is the mounting position of the balancer drive gear 30. ing. An outer peripheral spline 70 is formed at the position where the balancer drive gear is mounted. The outer diameter (tooth end diameter) D1 of the outer peripheral spline 70 is substantially the same as the large diameter (tooth end diameter) D3 of the cam driving chain sprocket 25. The small diameter (valley bottom diameter) d1 of the outer peripheral spline 70 is set to be substantially the same as or slightly larger than the small diameter (valley bottom diameter) d3 of the cam drive chain sprocket 25. An annular groove 66 for attaching a retaining clip is formed at the left end of the outer peripheral spline 70.
[0031]
On the other hand, the boss portion 30a of the balancer drive gear 30 is formed with an inner spline 71 that is spline-fitted to the outer spline 70 of the crankshaft 1. The small diameter (diameter of the tooth tip) d2 of the inner peripheral spline 71 is slightly larger than the small diameter d3 of the cam driving chain sprocket 25, and the large diameter (valley bottom diameter) D2 of the inner peripheral spline 71 is smaller than that of the cam driving chain sprocket 25. It is set slightly larger than the large diameter D3.
[0032]
FIG. 5 is an enlarged cross-sectional view taken along the line V-V in FIG. 4. The inner spline 71 of the balancer drive gear 30 and the outer spline 70 of the crankshaft 1 are naturally formed with the same number of teeth. 25 is also formed with the same number of teeth as the inner and outer splines 71 and 70, and between the teeth of the cam drive chain sprocket 25, each of the teeth of the inner spline 71 of the balancer drive gear 30 is connected to the crankshaft center. It is formed in a tooth shape that can pass in the O1 direction.
[0033]
[Action]
[Assembly of crankshaft]
(1) In FIG. 2, the crankshaft 1 is assembled by connecting the left and right crankshaft members with the crankpin 39. The main bearings 37 and 38 are fitted into the left and right crankcases 2a and 2b, respectively.
[0034]
(2) Insert the left and right ends of the crankshaft 1 into the main bearings 37, 38 fitted in the shaft support holes 41, 42 of the left and right crankcase members 2a, 2b before the coupling (split state). The crankcase members 2a and 2b are connected.
[0035]
(3) The primary gear 52 is spline-fitted to the right-side protruding portion of the crankshaft 1 and fixed in the direction of the crankshaft center O1 by the circlip 53.
[0036]
(4) In FIG. 4, the balancer driving gear 30 is fitted from the left end of the crankshaft 1, the teeth of the inner peripheral spline 71 are aligned between the teeth of the chain sprocket 25 for driving the cam as shown in FIG. To the right of the cam driven chain sprocket 25. Then, the outer peripheral spline 70 of the crankshaft 1 is spline-fitted, and the boss 30a is brought into contact with the left main bearing 37. Thereafter, the circlip 65 is fitted into the annular groove 66 and fixed in the direction of the crankshaft center O1.
[0037]
As in this embodiment, the number of teeth of the inner peripheral spline 71 of the balancer driving gear 30 and the number of teeth of the cam driving chain sprocket 25 are matched, and the distance between the teeth of the inner peripheral spline 71 is set between the teeth of the cam driving chain sprocket 25. If formed, the balancer drive gear 30 is assembled without increasing the crankshaft diameter of the crankshaft portion (balancer drive gear mounting position) between the cam drive chain sprocket 25 and the left main bearing 37. be able to. That is, the small diameter d2 of the inner circumferential spline 71 does not need to be larger than the outer diameter D3 of the chain sprocket 25 for driving the cam, and the weight of the crankshaft 1 can be reduced.
[0038]
In this embodiment, since the cam drive chain sprocket 25 and the balancer drive gear 30 are arranged on the protruding portion of the crankshaft 1 on the generator side, the primary gear is provided on the protruding portion of the crankshaft 1 on the clutch side. The chain sprocket 51 for driving the oil pump can be arranged between the right main bearing 38 and the primary gear 52 without further extending the position of 52 to the right, so that the size in the direction of the crankshaft center can be reduced. The degree of freedom of arrangement of the oil pumps 15, 16 and the like increases.
[0039]
Further, since the chain sprocket 51 for driving the oil pump is disposed on the clutch side, the space between the clutch 50 and the right side wall 38 of the crankcase is effectively used as a space for disposing the chain sprocket 31 such as the pump shaft 18. In this respect as well, the dimensions in the direction of the crankshaft center can be made compact.
[0040]
Other Embodiments of the Invention
(1) In the embodiment shown in FIG. 6, in the engine in which the cam chain 26 is disposed on the clutch side (right side) in the crankshaft center direction, the primary gear 52 and the cam drive disposed on the right protruding portion of the crankshaft 1 are provided. This is an example in which the present invention is applied to the structure of the chain sprocket 25 for use.
[0041]
In FIG. 6, a chain sprocket 25 for driving a cam is integrally formed on the right protruding portion of the crankshaft 1, and an outer peripheral spline 90 is formed on a crankshaft portion between the chain sprocket 25 and the right main bearing 38. An inner peripheral spline 91 of the primary gear 52 is spline-fitted to the outer peripheral spline 90 and fixed by a circlip 92. The relationship between the inner spline 91 of the primary gear 52 and the chain sprocket 25 for driving the cam is the same as the relationship between the inner spline 71 of the balancer drive gear 30 and the chain sprocket 25 described with reference to FIGS. With the number of teeth, the primary gear 52 can be inserted into the chain sprocket 25 in the direction of the crankshaft center.
[0042]
A pump gear 95 is fixed to the pump shaft 18, and the pump gear 95 meshes with a starting gear 55 formed integrally with the clutch gear 54.
[0043]
(2) In each of the above embodiments, a balancer driving gear or a primary gear is applied as an output gear fixed to a crankshaft, and a chain sprocket for cam driving is used as a chain sprocket integrally formed with the crankshaft. Although applied, the present application can be applied in the relationship between a pump drive gear for an oil pump and a chain sprocket for driving a cam, or in the relationship between a chain sprocket for driving a pump and another output gear. is there.
[0044]
【The invention's effect】
As described above, according to the present invention, (1) one of a pair of main bearings that support the crankshaft at both ends (for example, the left main bearing 37) and the crankshaft portion protruding out of the crank chamber from the main bearing. An output gear (eg, balancer driving gear 30) is fixed between the output chain sprocket (eg, cam driving chain sprocket 25) and the output chain sprocket (eg, cam driving chain sprocket 25). The space can be effectively used as a mounting space for the output gear, and the size of the engine in the direction of the crankshaft center can be kept compact. Further, since the output gear can be disposed adjacent to the main bearing, the support rigidity of the output gear can be increased. In addition, the size of the main bearing can be prevented from increasing.
[0045]
(2) The output gear has an inner spline that is spline-fitted to an outer spline formed at the gear mounting position of the crankshaft, and the inner spline has the same number of teeth as the chain sprocket. At the same time, if each tooth of the inner peripheral spline is formed in a shape that can pass between the teeth of the chain sprocket in the axial direction, the diameter of the crankshaft portion between the main bearing and the output chain sprocket is adjusted by the chain. The output gear need not be larger than the outer diameter of the sprocket, and the output gear can be inserted and fixed in the axial direction up to the mounting position. That is, it is possible to improve the assemblability of the output gears and reduce the weight of the crankshaft while reducing the size of the engine in the direction of the crankshaft center.
[0046]
(3) If a cam drive chain sprocket is arranged as the output chain sprocket, and a balancer drive gear is arranged as the output gear, the cam drive chain sprocket can be adapted to increase the bore diameter. Even if the formation position is far from the main bearing, the gear assemblability and the weight reduction of the crankshaft can be maintained.
[Brief description of the drawings]
FIG. 1 is a simplified left side view showing a main shaft arrangement of a four-cycle engine to which the present invention is applied.
FIG. 2 is an expanded sectional view taken along line II-II of FIG.
FIG. 3 is a sectional development view taken along the line III-III of FIG. 1;
FIG. 4 is an enlarged cross-sectional view of a left portion of the crankshaft with a balancer drive gear removed.
FIG. 5 is a sectional view taken along line VV of FIG. 4;
FIG. 6 shows another embodiment of the present invention, and is a cross-sectional developed view on the same cut surface as that of FIG. 2;
FIG. 7 is a sectional view of a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crankshaft 2 Crankcase 2a Left crankcase member 2b Right crankcase member 4 Crankcase 5 Transmission chamber 19 Balancer shaft 21, 22 Camshaft 25 Cam drive chain sprocket (an example of an output chain sprocket)
26 Cam chain 30 Balancer drive gear (an example of output gear)
34 Crankcase left wall 35 Crankcase right wall 37 Left main bearing 38 Right main bearing 44 Clutch chamber 45 Generator chamber 52 Primary gear (another example of output gear)
70 outer peripheral spline 71 inner peripheral spline 90 outer peripheral spline 91 inner peripheral spline

Claims (3)

An output gear is fixed between one of a pair of main bearings that support the crankshaft at both ends and an output chain sprocket formed on a crankshaft portion protruding out of the crank chamber from the main bearing. A gear mounting structure for a crankshaft of an engine, characterized in that: The output gear has an inner spline that is spline-fitted to an outer spline formed at a gear mounting position of the crankshaft, and the inner spline is formed with the same number of teeth as the chain sprocket. The gear mounting structure for a crankshaft of an engine according to claim 1, wherein each tooth of the inner peripheral spline is formed in a shape capable of passing between the teeth of the chain sprocket in the axial direction. 3. The gear mounting structure for an engine crankshaft according to claim 1, wherein the output chain sprocket is a cam drive chain sprocket of an intake / exhaust valve, and the output gear is a balancer driving gear.

Images