GB2515156A

GB2515156A - Engine having a counterweight device disposed on a crankshaft

Info

Publication number: GB2515156A
Application number: GB1405724.4A
Authority: GB
Inventors: Lan-Ting Fu; Wen-Tso Cheng; Chao-Chang Ho
Original assignee: Kwang Yang Motor Co Ltd
Current assignee: Kwang Yang Motor Co Ltd
Priority date: 2013-04-03
Filing date: 2014-03-31
Publication date: 2014-12-17
Anticipated expiration: 2034-03-31
Also published as: GB2515156B; TWI593877B; TW201439428A; DE102014205936B4; DE102014205936A1; GB201405724D0

Abstract

An engine having a counterweight device disposed on a crankshaft is provided. The engine includes: a crankcase 2; a crankshaft 4 disposed rotatably in the crankcase 2; a start gear 5 sleeved on the crankshaft 4 and disposed outwardly of the crankcase 2; and a counterweight device 7. The crankcase 2 includes a first case half 21 and a second case half 22 that are interconnected to define a crank chamber 23. The crankshaft 4 includes a shaft portion 41 extending through the first and second case halves 21, 22, and at least one eccentric counterweight portion 42 extending radially and outwardly from the shaft portion 41 and disposed in the crank chamber 23. The counterweight device 7 is sleeved on the shaft portion 41 of the crankshaft 4, and is disposed outwardly of the crankcase 2 between the crank chamber 23 and the start gear 5.

Description

ENGINE HAVING A COUNTERWEIGHT DEVICE

DISPOSED ON A CRANKSHAFT

This invention relates to a device for producing a power, and more particularly to an engine.

A piston of an engine is moved through compression, ignition, and explosion of a gas to drive rotation of a crankshaft to thereby produce a power. To increase the rotary inertia of the crankshaft to output smoothly a rotary power and reduce vibration, an eccentric counterweight block may be formed on the crankshaft. However, in an engine having a large discharge capacity, a comparatively heavy counterweight block is reguired for increasing the rotary inertia. As such, the volume of the crankshaft and the eccentric counterweight block and a space for receiving the crankshaft and the eccentric counterweight block are increased. Furthermore, the geometrical shape of the crankshaft becomes more complicated. Hence, the manufacturing precision and errors of both the angle of eguilibrium and the balance ratio need to be increased.

Another method for increasing the rotary inertia is to provide at least one of a generator, a unidirectional clutch, andabeltpulleyonthe crankshaft. Ifnecessary, at least one auxiliary counterweight block may be provided on the belt pulley or the unidirectional clutch, such as those disclosed in Taiwanese Patent Mo. 201242805 and Taiwanese Patent Publication NO. M430526. However, since the auxiliary counterweight block is far away from the eccentric counterweight block, when rotated, the crankshaft is subjected to a relatively large torgue applied by the eccentric counterweight block and the auxiliarycounterweightblock, andthus isdeformedeasily, thereby reducing the durability of the crankshaft.

Therefore, the object of this invention is to provide an engine that has an increased rotary inertia.

According to this invention, there is provided an engine including: a crankcase including a first case half and a second case half that are interconnected to define a crank chamber therebetween; a crankshaft disposed rotatably in the crankcase and including a shaft portion extending through the first and second case halves, and at least one eccentric counterweight portion extending radially and outwardly from the shaft portion and disposed in the crank chamber; a start gear sleeved on the crankshaft and disposed outwardly of the crankcase; and a counterweight device connected fixedly to the shaft portion of the crankshaft; wherein the counterweight device is sleeved on the shaft portion of the crankshaft, and is disposed outwardly of the crankcase between the crank chamber and the start gear.

As such, the counterweight device is disposed in a space that is not utilized, so as to promote the space efficiency.

Furthermore, since the counterweight device is disposed between the crank chamber and the start gear, the crankshaft serves as a shortened cantilever, thereby diminishing deformation of the crankshaft caused due to rotation of the crankshaft. As such, a torgue applied by the counterweight device to the crankshaft is reduced to have less adverse affection on the effect of increasing the rotary inertia, and the size of the crankshaft is also reduced.

These and other features and advantages of this invention will become apparent in the following detailed description of a preferred embodiment of this invention, with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of the preferred embodiment of an engine according to this invention; Fig. 2 is an exploded perspective view of a counterweight device, a start gear, a generator, and a crankshaft of the preferred embodiment; Fig. 3 is a sectional view of the counterweight device of the preferred embodiment; Fig. 4 is a side view of the counterweight device of the preferred embodiment, illustrating a plurality of eguidistant notches; and Fig. 5 is a fragmentary schematic side view of the preferred embodiment, illustrating a first case half of a crankcase.

Referring to Figs. 1 and 2, the preferred embodiment of an engine according to this invention includes a crankcase 2, first and second caps 31, 32 that cover respectively two opposite sides of the crankcase 2, a crankshaft 4 disposed rotatably in the crankcase 2, a start gear 5 sleeved on the crankshaft 4 and disposed outwardly of the crankcase 2, a generator 61 sleeved on the crankshaft 4, a unidirectional clutch 62 sleeved on the crankshaft 4, a timing gear 63 sleeved on the crankshaft 4, and a counterweight device 7.

The crankcase 2 includes a first case half 21 and a second case half 22 that are interconnected to define a crank charter 23 therebetween. Each of the first and second case halves 21, 22 has an upright wall 211, 221 and a rib wall 212, 222 extending from the upright wall 211, 221. The crank chamber 23 is formed among the upright wall 211 and the rib wall 212 of the first case half 21 and the llpright wall 221 and the rib wall 222 of the second case half 22.

With particular reference to Figs. 1 and 5, the first case half 21 of the crankshaft 2 has a protrusion 213 extending toward the crankshaft 4. In this embodiment, the first cap 31 covers the first case half 21, and the second cap 32 covers the second case half 22.

With particular reference to Figs. 1 and 2, the crankshaft 4 includes a shaft portion 41 extending through the first and second case halves 21, 22, and two eccentric counterweight portions 42 extending radially and outwardly from the shaft portion 41, spaced apart from each other, and disposed in the crank chamber 23. The shaft portion 41 of the crankshaft 4 extends throngh two bearings 91 disposed respectively on the upright walls 211 of the fist case half 21 and the upright wall 221 of the second case half 221, and is driven by a piston 94 and a crank 92 to rotate relative to the crankcase 2 to thereby produce a power.

The start gear 5 is sleeved on the shaft portion 41 of the crankshaft 4. In this embodiment, the start gear 5 is disposed between the first case half 21 and the first cap 31, and is connected to a starting motor (not shown) . When the engine is in an idle state, the generator can be actuated to drive the starting motor to thereby rotate the start gear 5, so that the crankshaft 4 is rotated, thereby allowing the engine to be activated.

The generator 61 includes a stator 611 disposed fixedly in the first cap 31, and a rotor 612 surrounding the stator 622 and co-rotatable with the shaft portion 41 of the crankshaft 4. The generator 61 is disposed between the first case half 21 and the first cap 31, and is operable for driving rotation of the rotor 612 and the shaft portion 41 of the crankshaft 4 to increase the rotary inertia. When rotor 612 rotates relative to the stator 611, electricity is produced for use of the vehicle provided with the engine.

The unidirectional clutch 62 is disposed on the shaft portion 41 of the crankshaft 4, and is connected to the start gear 5 for limiting the crankshaft 4 to rotate in a single direction.

The timing gear 63 is sleeved on the shaft portion 41 of the crankshaft 4, and is adapted for driving a timing chain 93. The timingchain 93 is disposedarounda camshaft (not shown) of the engine. Throngh operation of the timing gear 63 and the timing chain 93, rotation of the crankshaft 4 can be transferred to the camshaft for control operation of a carburetor (not shown) With particular reference to Figs. 1, 3, and 4, the counterweight device 7 is sleeved fixedly on the shaft portion 41 of the crankshaft 4, and is disposed outwardly of the crankcase 2 between the crank chamber 23 of the crankcase 2 and the start gear 5. Preferably, the counterweight device 7 is disposed between the timing gear 63 and the start gear 5.

The counterweight device 7 includes a first counterweight 71 sleeved on the crankshaft 4 in a close fitting manner, a second counterweight 72 sleeved on the first counterweight 71, and a plurality of fasteners 73 connecting the second counterweight 72 removably to the first counterweight 71.

With particular reference to Figs. 2, 3, and 4, the first counterweight 71 has a large end portion 711 surrounding the shaft portion 41 of the crankshaft 4, and a small end portion 712 surrounding the shaft portion 41 of the crankshaft 4, extending from the large end portion 711 in a direction away from the eccentric counterweight portions 42 of the crankshaft 4, and having an outer diameter smaller than that of the large end portion 711. The large end portion 711 of the first counterweight 7 has a plurality of angularly equidistant notches 713 disposed around the shaft portion 41 of the crankshaft 4. The notches 713 are positioned such that, during assembly and disassembly of the engine, the protraction 213 of the first case half 21 can pass through one of the notches 713. It should be noted that, if the first counterweight 71 cannot move to contact an outer periphery of the large end portion 711 of the first counterweight 71 during assembly, the notches 713 can be omitted from the large end portion 711 of the first counterweight 71 to facilitate increase of the rotary inertia.

The second counterweight 72 has a small-diameter section 721 sleeved on the small end portion 712 of the first counterweight 71 in a close fitting manner, and a large-diameter section 722 sleeved on the large end portion 711 in a close fitting manner. The fasteners 73 extend through the small-diameter section 721 and into the large end portion 711 of the first counterweight 71 so as to connect the second counterweight 72 removably to the first counterweight 71. Tn this embodiment, each fastener 73 is configured as a bolt, is disposed between the start gear and the eccentric counterweight portions 42, and has a first end 731 distal from the start gear 5 and engaging a threaded hole in the large end portion 711 of the first counterweight 71, and a second end (i.e., head) 732

S

proximate to the start gear 5 and disposed within a counterbore in the small-diameter section 721 in the second counterweight 72. The first ends 731 of the fasteners 73 do not project from an end surface of the large end portion 711 of the first counterweight 71. The second ends 732 of the fasteners 73 do not project from an end surface of the small-diameter section 721 of the second counterweight 72.

Each fastener 73 cooperates with the corresponding threaded hole and the corresponding counterbore to constitute a fastener assembly, which may be replaced with a key and keyway arrangement or a spline arrangement. If a space for receiving the first and second counterweights 71, 72 is enough, one of the first and second ends 731, 732 of each fastener 73 can be configured to project from a corresponding one of the large end portion 711 of the first counterweight 71 and the small-diameter section 721 in the second counterweight 72.

With particular reference to Figs. 1, 2, and 3, during assembly, the timing gear 63 and the first counterweight 71 are first sleeved on the shaft portion 41 of the crankshaft 4. Next, the first and second case halves 21, 22 of the crankcase 2 are assembled to the crankshaft 4.

Subseguently, the second counterweight 72, the start gear 5, the unidirectional clutch 62, and the generator 61 are assembled to a portion of the crankshaft 4 adjacent to and disposed outwardly of The first case half 21 of the crankcase 2, and a driving gear 95 is assembled to a portion of the crankshaft 4 adjacent to and disposed outwardly of the second case half 22, and is connected with a shift-control type transnission or a continuously variable transmission (CVT) . Finally, the first and second caps 31, 32 are assembled respectively to the first and second case halves 21, 22.

Upon actuation of the engine, the crankshaft 4 is rotated to drive rotation of the unidirectional clutch 62 and the rotor 612 of the generator 61. At the same time, the counterweight device 7 also co-rotates with the crankshaft 4. If it is necessary to focus on a reduction in the vibration and noise of the engine, both of the first and second counterweights 71, 72 of the counterweight device 7 need to be assembled to the crankshaft 4 for increasing the rotary inertia. If it is necessary to focus on high acceleration performance, preferably, only the first counterweight 71 of the counterweight device 7 is assembled to the crankshaft 4.

Since the counterweight device 7 is disposed between the crank chamber 23 and the start gear 5, the effective moment arm and the torque acting on the crankshaft 4 are reduced. Consequently, the deformation of the shaft portion 41 of the crankshaft 4 is reduced to improve the durability of the crankshaft 4.

In view of the above, the counterweight device 7 is disposed between the crank chamber 23 and the start gear 5. That is, the counterweight device 7 is disposed in a space that is not utilized, so as to promote the space efficiency. Furthermore, the counterweight device 7 is disposed in proximity to the crank chamber 23 so that adverse affection of the torque applied by the counterweight device 7 on the crankshaft 4 is reduced effectively. Further, the second counterweight 72 can be assembled to or removed from the first counterweight 71 according to the needs of the users, so as to increase the rotary inertia appropriately. Thus, the object of this invention is achieved.

Claims

CLAIMS: 1. An engine including: a crankcase including a first case half and a second case half that are interconnected to define a crank chamber therebetween; a crankshaft disposed rotatably in the crankcase and including a shaft portion extending through the first and second case halves, and at least one eccentric counterweight portion extending radially and outwardly from the shaft portion and disposed in the crank chamber; a start gear sleeved on the crankshaft and disposed outwardly of the crankcase; and a counterweight device connected fixedly to the shaft portion of the crankshaft; wherein the counterweight device is sleeved on the shaft portion of the crankshaft, and is disposed outwardly of the crankcase between the crank chamber and the start gear.
2. The engine as claimed in Claim 1, wherein the counterweight device includes a first counterweight sleeved on the crankshaft in a close fitting manner.
3. The engine as claimed in Claim 2, wherein the first counterweight has a large end portion surrounding the shaft portion of the crankshaft, and a small end portion surrounding the shaft porticn of the crankshaft, extending from the large end portion in a direction away from the eccentric counterweight portion of the crankshaft, and having an outer diameter smaller than that of the large end portion.
4. The engine as claimed in Claim 3, wherein the counterweight device further includes a second counterweight sleeved removably on the first counterweight.
5. The engine as claimed in Claim 4, wherein the second counterweight has a small-diameter section sleeved on the small end portion of the first counterweight in a close fitting manner, and a large-diameter section sleeved on the large end portion in a close fitting manner, the counterweight device further including at least one fastener extending through the small-diameter section and into the large end portion of the first counterweight so as to connect the second counterweight removably to the first counterweight.
6. The engine as claimed in Claim 1, wherein the engine further includes a first cap covering the first case half of the crankcase, and a second cap covering the second case half of the crankcase, the start gear being disposed between the first case half and the first cap.
7. The engine as claimed in Claim 1, wherein the engine further includes a generator sleeved on the shaft portion of the crankshaft between the first case half of the crankcase and the first cap, the generator including an stator secured on the first cap, and a rotor disposed around the the stator and co-rotatable with the shaft portion of the crankshaft.
8. The engine as claimed in claim 1, wherein the engine further includes a timing gear sleeved on the shaft portion of the crankshaft and adapted for driving a timing chain, the counterweight device being disposed between the timing gear and the start gear.
9. The engine as claimed in claim 3, wherein the large end portion of the first counterweight has a plurality of angularly eguidistant notches disposed around the shaft portion of the crankshaft.
10. The engine as claimed in claim 4, wherein the counterweight device further includes a plurality of fasteners connecting said second counterweight removably to said first counterweight, each of the fasteners being disposed between the start gear and the eccentric counterweight portion and having at least one end that does not project from a correspond end surface of a corresponding one of the first and second counterweights.
11. An engine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.