JP6945480B2 - How to set the mass of the crankshaft and the counterweight of the crankshaft - Google Patents

Description

The present invention relates to a crankshaft for a three-cylinder engine and a method for setting the mass of a crankshaft counterweight.

As shown in Patent Document 1, the crankshaft for a three-cylinder engine includes four main journals and three crankpins. Each of the four main journals is rotatably supported by bearings. Counterweights are arranged on the opposite sides of the three crank pins in the radial direction with the four main journals in between.

Japanese Unexamined Patent Publication No. 2010-43625

The crankshaft is required to be lighter in weight from the viewpoint of improving fuel efficiency. As one measure for reducing the weight of the crankshaft, it is conceivable to reduce the size (weight reduction) of the counterweight for the central crankpin among the three crankpins. However, the counterweight has a function of canceling an inertial force (centrifugal force) such as a crank pin. Therefore, if the counterweight for the central crank pin is miniaturized, the balance of inertial force is lost and the friction (energy loss due to friction with the bearing) of the two main journals on both sides of the central crank pin in the axial direction increases. .. Therefore, an object of the present invention is to provide a method for setting the mass of a crankshaft and a counterweight of a crankshaft capable of reducing friction.

In order to solve the above problems, the crankshaft of the present invention includes four main journals rotatably supported by a bearing, three crankpins eccentrically arranged with respect to the main journal, and the main journal and the crank. A crankshaft for a three-cylinder engine including six crankarms connecting pins, the four main journals being the first to fourth main journals in order from one end side in the axial direction, and the three cranks. The pins are the first to third crank pins, the six crank arms are the first to sixth crank arms, and further, the first counter weight connected to the first crank arm and the second crank arm are connected to each other. A case where the second counterweight, the fifth counterweight connected to the fifth crank arm, and the sixth counterweight connected to the sixth crank arm are provided, and the first and second counterweights have the same mass. In comparison, the second counterweight is lighter than the first counterweight and the fifth and sixth counterweights have the same mass so that the synthetic inertial force acting on the second main journal can be reduced. The fifth counterweight is lighter than the sixth counterweight so that the synthetic inertial force acting on the third main journal can be reduced as compared to some cases.

In order to solve the above problem, the method for setting the mass of the crankshaft counterweight of the present invention is when the first and second counterweights have the same mass and the fifth and sixth counterweights have the same mass. , The synthetic inertial force calculation step for calculating the synthetic inertial force acting on the second and third main journals, and the second counterweight being lighter than the first counterweight so that the synthetic inertial force becomes smaller. It is characterized by having a weight reduction step of reducing the weight of the fifth counterweight with respect to the sixth counterweight.

Inertial force is applied to the second main journal from the first crank pin, the second crank pin, the second counter weight, and the like. According to the crankshaft of the present invention, the second counterweight is lighter than the first counterweight. Therefore, the synthetic inertial force acting on the second main journal can be reduced as compared with the case where the first counterweight and the second counterweight have the same mass.

Inertial force is applied to the third main journal from the second crank pin, the third crank pin, the fifth counter weight, and the like. According to the crankshaft of the present invention, the fifth counterweight is lighter than the sixth counterweight. Therefore, the synthetic inertial force acting on the third main journal can be reduced as compared with the case where the fifth counterweight and the sixth counterweight have the same mass.

As described above, according to the crankshaft of the present invention, the synthetic inertial force acting on the second and third main journals can be reduced. Therefore, the friction of the second and third main journals can be reduced.

Further, according to the method for setting the mass of the counterweight of the crankshaft of the present invention (hereinafter, appropriately abbreviated as "mass setting method"), the second is achieved by setting the mass difference between the first and second counterweights. The synthetic inertial force acting on the main journal can be reduced. Similarly, by setting the mass difference between the 5th and 6th counterweights, the synthetic inertial force acting on the 3rd main journal can be reduced.

It is a perspective view of the crankshaft which is one Embodiment of the crankshaft of this invention. It is a right side view of the crankshaft. FIG. 2 is a cross-sectional view taken along the line III-III in FIG. FIG. 2 is a cross-sectional view taken along the IV-IV direction of FIG. It is a schematic vector figure of the inertial force acting on the 3rd main journal in the synthetic inertial force calculation step of the mass setting method of the counterweight of the crankshaft. It is a schematic vector diagram of the inertial force acting on the 3rd main journal in the weight reduction step of the same mass setting method.

Hereinafter, embodiments of the crankshaft and the mass setting method of the present invention will be described.

(Crankshaft configuration)
First, the configuration of the crankshaft of this embodiment will be described. FIG. 1 shows a perspective view of the crankshaft of the present embodiment. FIG. 2 shows a right side view of the crankshaft. It should be noted that FIGS. 1 and 2 show a state in which the piston (not shown) connected to the second crankpin 2P is located at the top dead center.

As shown in FIGS. 1 and 2, the crankshaft 1 of the present embodiment is a crankshaft for an in-line 3-cylinder engine. The crankshaft 1 includes first to fourth main journals 1J to 4J, first to third crankpins 1P to 3P, first to sixth crankarms 1A to 6A, and first to sixth counterweights 1W to. It is equipped with 6W. A pulley (not shown) is arranged at the front end (one end in the axial direction) of the crankshaft 1. A flywheel 90 is arranged at the rear end (the other end in the axial direction) of the crankshaft 1. A combustion chamber (not shown) is arranged on the upper side of the crankshaft 1.

The first to fourth main journals 1J to 4J extend in the front-rear direction, respectively. The first to fourth main journals 1J to 4J are arranged in a line in the front-rear direction. The first to fourth main journals 1J to 4J, that is, the crankshaft 1, is rotatably supported around the axis O of the first to fourth main journals 1J to 4J by the first to fourth bearings 1B to 4B. ..

The first to third crank pins 1P to 3P extend in the front-rear direction, respectively. A connecting rod (not shown) is attached to each of the first to third crankpins 1P to 3P via a bearing (not shown). When viewed from the front side, the first to third crank pins 1P to 3P are arranged so as to be displaced from each other by 120 ° with respect to the axis O.

The first to sixth crank arms 1A to 6A are interposed between the first to fourth main journals 1J to 4J and the first to third crank pins 1P to 3P. The first to sixth counterweights 1W to 6W are arranged on opposite sides of the axial center O in the radial direction (diameter direction with respect to the extending direction of the axial center O) of the first to sixth crank arms 1A to 6A. There is.

(Shape of 1st to 6th counterweights 1W to 6W)
Next, the shapes of the first to sixth counterweights will be described. As shown in FIG. 2, the shapes of the third and fourth counterweights 3W and 4W are the same. Therefore, the masses of the third and fourth counterweights 3W and 4W are the same.

The first, second, fifth, and sixth counterweights 1W, 2W, 5W, and 6W project radially outward from the third and fourth counterweights 3W and 4W. Further, the first, second, fifth, and sixth counterweights 1W, 2W, 5W, and 6W extend longer in the circumferential direction (± θ direction described later) than the third and fourth counterweights 3W and 4W. doing. Therefore, the first, second, fifth, and sixth counterweights 1W, 2W, 5W, and 6W have a larger mass than the third and fourth counterweights 3W and 4W.

FIG. 3 shows a cross-sectional view taken along the direction III-III of FIG. The second crankpin 2P, the first and third counterweights 1W and 3W, the second main journal 2J, and the second bearing 2B are shown by dotted lines. Further, the forward rotation direction (clockwise direction when viewed from the front side) of the crankshaft 1 around the axis O is the + θ direction, and the reverse rotation direction (counterclockwise direction when viewed from the front side) is the −θ direction. As shown in FIG. 3, the only difference between the second counterweight 2W and the first counterweight 1W is the circumferential position of the −θ direction end 1Wa and 2Wa. The −θ direction end 2Wa of the second counterweight 2W is arranged so as to be offset in the + θ direction from the −θ direction end 1W of the first counterweight 1W. As shown by hatching in FIG. 1, the second counterweight 2W is lighter than the first counterweight 1W by this amount.

FIG. 4 shows a cross-sectional view taken along the IV-IV direction of FIG. The third crankpin 3P, the sixth counterweight 6W, the third main journal 3J, and the third bearing 3B are shown by dotted lines. Further, the forward rotation direction of the crankshaft 1 around the axis O is the + θ direction, and the reverse rotation direction is the −θ direction. As shown in FIG. 4, the difference between the fifth counterweight 5W and the sixth counterweight 6W is only the circumferential positions of the + θ direction ends 5Wb and 6Wb. The + θ direction end 5Wb of the fifth counterweight 5W is arranged so as to be offset in the −θ direction from the + θ direction end 6Wb of the sixth counterweight 6W. As shown by hatching in FIG. 1, the fifth counterweight 5W is lighter than the sixth counterweight 6W by this amount.

(Mass setting method of 1st, 2nd, 5th, 6th counterweights 1W, 2W, 5W, 6W of crankshaft 1)
Next, a method of setting the mass of the first, second, fifth, and sixth counterweights 1W, 2W, 5W, and 6W of the crankshaft 1 will be described. The mass setting method includes a synthetic inertial force calculation step and a weight reduction step.

In the synthetic inertial force calculation step, it is assumed that the first and second counterweights 1W and 2W have the same mass. Further, it is assumed that the 5th and 6th counterweights 5W and 6W have the same mass. Then, the synthetic inertial force acting on the second and third main journals 2J and 3J in this case is calculated.

FIG. 5 shows a schematic vector diagram of the inertial force acting on the third main journal in the synthetic inertial force calculation step of the method for setting the mass of the counterweight of the crankshaft of the present embodiment. The direction and length of the arrow indicating the inertial force are schematic. Further, FIG. 5 corresponds to FIG. Further, the fifth counterweight 5W shown in FIG. 5 has the same shape as the sixth counterweight 6W shown in FIG.

As shown in FIG. 5, the third main journal 3J has an inertial force f2P from the second crank pin 2P, an inertial force f3P from the third crank pin 3P, and an inertial force f4W from the fourth counterweight 4W. Inertial force f5W acts from the counterweight 5W, respectively. That is, a synthetic inertial force f3J (a resultant force of inertial forces f2P, f3P, f4W, and f5W) acts on the third main journal 3J.

Similarly to the third main journal 3J, the second main journal 2J also has a synthetic inertial force (inertia force from the first crank pin 1P shown in FIG. 3, inertial force from the second crank pin 2P, and from the second counterweight 2W. The inertial force of the above, the resultant force of the inertial force from the third counterweight 3W) is acting.

In the weight reduction step, the weight of the second counterweight 2W is reduced with respect to the weight of the first counterweight 1W so that the calculated synthetic inertial force becomes smaller. In addition, the weight of the 5th counterweight 5W is reduced with respect to that of the 6th counterweight 6W. However, the weight reduction target portion R is a portion extending from 90 ° in the −θ direction to 90 ° in the + θ direction with the direction of the combined inertial force f3J shown in FIG. 5 interposed therebetween. That is, in the weight reduction step, of the second and fifth counterweights 2W and 5W, the portion included in the weight reduction target portion R is reduced in weight to act on the second and third main journals 2J and 3J. Reduce the synthetic inertial force.

FIG. 6 shows a schematic vector diagram of the inertial force acting on the third main journal in the weight reduction step of the method for setting the mass of the counterweight of the crankshaft of the present embodiment. The direction and length of the arrow indicating the inertial force are schematic. Further, FIG. 6 corresponds to FIG.

As shown in FIG. 6, when the weight of the fifth counterweight 5W is reduced, the direction and size (length) of the inertial force F5W (corresponding to f5W in FIG. 5) change. Therefore, a synthetic inertial force F3J (corresponding to f3J in FIG. 5; a resultant force of inertial forces f2P, f3P, f4W, and F5W) acts on the third main journal 3J. As shown in FIGS. 5 and 6, the combined inertial force F3J after the weight reduction step is smaller than the combined inertial force f3J after the combined inertial force calculation step (before the weight reduction step). Therefore, the friction of the third main journal 3J can be reduced. Further, the + θ direction end 5Wb after the weight reduction step is arranged so as to be displaced in the −θ direction from the + θ direction end 5Wb after the combined inertial force calculation step. By this amount, the weight of the fifth counterweight 5W can be reduced. The mass of the sixth counterweight 6W may be increased in order to adjust the mass balance of the entire crankshaft 1.

The weight reduction step can be executed for the second main journal 2J as well as for the third main journal 3J. That is, the synthetic inertial force acting on the second main journal 2J can be reduced. Further, the friction of the second main journal 2J can be reduced. Further, as shown with reference to FIG. 3, the −θ direction end 2Wa after the weight reduction step is + θ more than the −θ direction end 2Wa (−θ direction end 1Wa in FIG. 3) after the combined inertial force calculation step. They are arranged so that they are offset in the direction. The weight of the second counterweight 2W can be reduced by this amount. The mass of the first counterweight 1W may be increased in order to adjust the mass balance of the entire crankshaft 1.

As a result of CAE (Computer Aided Engineering) analysis, the friction of the 3rd main journal 3J can be reduced by 4.9% by using the mass setting method described above, assuming that the friction after the synthetic inertial force calculation step is 100%. rice field. Similarly, the friction of the second main journal 2J could be reduced. Further, although the masses of the first and sixth counterweights 1W and 6W were increased in order to adjust the mass balance of the entire crankshaft 1, the mass of the crankshaft 1 after the synthetic inertial force calculation step was set to 100%, and the crankshaft 1 was used. We were able to reduce the weight of the product by 0.17%.

(Action effect)
Next, the effects of the crankshaft and the mass setting method of the present embodiment will be described. As shown in FIGS. 5 and 6, the third main journal 3J has inertial forces f2P, f3P, from the second crank pin 2P, the third crank pin 3P, the fourth counter weight 4W, the fifth counter weight 5W, and the like. f4W, f5W and F5W are added. According to the crankshaft 1 of the present embodiment, the fifth counterweight 5W is lighter than the sixth counterweight 6W. Therefore, the synthetic inertial forces f3J and F3J acting on the third main journal 3J can be reduced as compared with the case where the fifth counterweight 5W and the sixth counterweight 6W have the same mass.

Similarly, inertial force is applied to the second main journal from the first crank pin 1P, the second crank pin 2P, the second counter weight 2W, the third counter weight 3W, and the like. According to the crankshaft 1 of the present embodiment, the second counterweight 2W is lighter than the first counterweight 1W. Therefore, the synthetic inertial force acting on the second main journal 2J can be reduced as compared with the case where the first counterweight 1W and the second counterweight 2W have the same mass.

As described above, according to the crankshaft 1 of the present embodiment, the synthetic inertial force acting on the second and third main journals 2J and 3J can be reduced. Therefore, the friction of the second and third main journals 2J and 3J can be reduced. Further, when the mass balance adjustment is not required in the crankshaft 1 after the friction is reduced, the weight of the crankshaft 1 can be reduced. Further, even when the mass balance of the crankshaft 1 after the friction is reduced needs to be adjusted, the weight increase of the crankshaft 1 can be suppressed.

As shown in FIG. 3, when viewed from the front side, the −θ direction end 2Wa of the second counterweight 2W is arranged so as to be offset in the + θ direction from the −θ direction end 1W of the first counterweight 1W. Therefore, the synthetic inertial force acting on the second main journal 2J can be reduced as compared with the case where the ends 1Wa and 2Wa in the −θ direction are arranged at the same position. In addition, the weight of the second counterweight 2W can be reduced.

As shown in FIG. 4, when viewed from the front side, the + θ direction end 5Wb of the fifth counterweight 5W is arranged so as to be offset in the −θ direction from the + θ direction end 6Wb of the sixth counterweight 6W. Therefore, the synthetic inertial force acting on the third main journal 3J can be reduced as compared with the case where the + θ direction ends 5Wb and 6Wb are arranged at the same position. Further, the weight of the fifth counterweight 5W can be reduced.

According to the mass setting method of the first, second, fifth, and sixth counterweights 1W, 2W, 5W, and 6W of the crankshaft 1 of the present embodiment, the mass difference between the first and second counterweights 1W and 2W. By setting the shape difference, the synthetic inertial force acting on the second main journal 2J can be reduced. Similarly, by setting the mass difference and the shape difference between the fifth and sixth counterweights 5W and 6W, the synthetic inertial force f3J acting on the third main journal 3J can be reduced.

As shown in FIG. 5, when the synthetic inertial force f3J acting on the third main journal 3J is reduced, the weight reduction target portion R of the fifth counterweight 5W is 90 in the −θ direction with the direction of the synthetic inertial force f3J in between. It is set in the portion extending from ° to 90 ° in the + θ direction (the portion of ± 90 ° or less). The reason why the weight reduction target portion R is set to this portion is that if it exceeds ± 90 °, the synthetic inertial force f3J may increase. The same applies to the weight reduction target portion R of the second counterweight 2W.

As shown in FIG. 3, the portion of the second counterweight 2W from the −7 ° position to the + 83 ° position, where the position of the center of gravity G of the second crank pin 2P with respect to the axis O is 0 ° when viewed from the front side. The mass of (lightweight portion R2W) is lighter than the rest. Therefore, the synthetic inertial force acting on the second main journal 2J can be reduced. As shown in FIG. 4, when viewed from the front side, the position of the center of gravity G of the second crank pin 2P with respect to the axis O is set to the 0 ° position, and the portion of the fifth counterweight 5W from the −84 ° position to the + 6 ° position. The mass of (lightweight portion R5W) is lighter than the rest. Therefore, the synthetic inertial force acting on the third main journal 3J can be reduced.

<Others>
The embodiment of the crankshaft and the mass setting method of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. It is also possible to carry out in various modified forms and improved forms that can be performed by those skilled in the art.

The crankshaft of the present invention is suitable for use in a crankshaft in which the friction of the second and third main journals 2J and 3J tends to be large. For example, a crankshaft 1 that does not have the 3rd and 4th counterweights 3W and 4W, and 3rd and 4th counterweights 3W rather than the 1st, 2nd, 5th and 6th counterweights 1W, 2W, 5W and 6W. 4W is suitable for embodying as a lightweight crankshaft 1.

As shown in FIG. 5, in the mass setting method, the types, directions, sizes, etc. of the inertial forces f2P, f3P, f4W, and f5W acting on the second and third main journals 2J and 3J are not particularly limited. For example, in the case of the crankshaft 1 having no third and fourth counterweights 3W and 4W, the inertial forces of the third and fourth counterweights 3W and 4W do not act on the second and third main journals 2J and 3J.

Further, the method for reducing the weight of the second and fifth counterweights 2W and 5W is not particularly limited. For example, the second and fifth counterweights 2W and 5W may be thinner than the first and sixth counterweights 1W and 6W. Further, holes may be formed in the second and fifth counterweights 2W and 5W.

The types of the first to fourth bearings 1B to 4B are not particularly limited. It may be a slide bearing or a roller bearing. Compared with roller bearings, slide bearings tend to have a larger friction between the first to fourth main journals 1J to 4J. Therefore, when the crankshaft of the present invention is used for the slide bearing, friction can be effectively reduced. The type of engine using the crankshaft of the present invention is not particularly limited. It may be a 2-stroke engine, a 4-stroke engine, or the like. Further, the stroke direction of the piston is not particularly limited. It may be vertical, horizontal, or intersecting the vertical and horizontal directions. Further, the engine and the battery (secondary battery, fuel cell, etc.) may be used together. The driving object of the engine may be an automobile, a motorcycle, or the like.

1: Crankshaft, 1A to 6A: 1st to 6th crank arms, 1B to 4B: 1st to 4th bearings, 1J to 4J: 1st to 4th main journals, 1P to 3P: 1st to 3rd cranks Pins, 1W to 6W: 1st to 6th counterweights, 1Wa: −θ direction end, 2Wa: −θ direction end, 5Wb: + θ direction end, 6Wb: + θ direction end, 90: flywheel, G: center of gravity, O : Axis, R: Lightweight part, R2W: Lightweight part, R5W: Lightweight part

Claims (5)

Four main journals rotatably supported by bearings and
Three crank pins arranged eccentrically with respect to the main journal,
Six crank arms connecting the main journal and the crank pin,
A crankshaft for a 3-cylinder engine equipped with
From one end side in the axial direction, the four main journals are the first to fourth main journals, the three crank pins are the first to third crank pins, and the six crank arms are the first to sixth crank arms. It ’s a crank arm,
Further, a first counterweight connected to the first crank arm, a second counterweight connected to the second crank arm, a fifth counterweight connected to the fifth crank arm, and a sixth counterweight connected to the sixth crank arm. With a counterweight,
The second counterweight is lighter than the first counterweight so that the synthetic inertial force acting on the second main journal can be reduced as compared with the case where the first and second counterweights have the same mass. And
The fifth counterweight is lighter than the sixth counterweight so that the synthetic inertial force acting on the third main journal can be reduced as compared with the case where the fifth and sixth counterweights have the same mass. der is,
Further, a third counterweight connected to the third crank arm and a fourth counterweight connected to the fourth crank arm are provided.
It said first, second, fifth, than said sixth counterweight third crankshaft fourth counterweights characterized lightweight der Rukoto. Four main journals rotatably supported by bearings and
Three crank pins arranged eccentrically with respect to the main journal,
Six crank arms connecting the main journal and the crank pin,
A crankshaft for a 3-cylinder engine equipped with
From one end side in the axial direction, the four main journals are the first to fourth main journals, the three crank pins are the first to third crank pins, and the six crank arms are the first to sixth crank arms. It ’s a crank arm,
Further, a first counterweight connected to the first crank arm, a second counterweight connected to the second crank arm, a fifth counterweight connected to the fifth crank arm, and a sixth counterweight connected to the sixth crank arm. With a counterweight,
The second counterweight is lighter than the first counterweight so that the synthetic inertial force acting on the second main journal can be reduced as compared with the case where the first and second counterweights have the same mass. And
The fifth counterweight is lighter than the sixth counterweight so that the synthetic inertial force acting on the third main journal can be reduced as compared with the case where the fifth and sixth counterweights have the same mass. And
A crankshaft that does not include a third counterweight connected to the third crank arm and a fourth counter weight connected to the fourth crank arm . When viewed from one end side in the axial direction, the forward rotation direction of the first to fourth main journals is the + θ direction, and the reverse rotation direction is the −θ direction.
The −θ direction end of the second counterweight is arranged so as to be offset in the + θ direction from the −θ direction end of the first counterweight.
The crankshaft according to claim 1 or 2 , wherein the + θ direction end of the fifth counterweight is arranged so as to be displaced in the −θ direction from the + θ direction end of the sixth counterweight. Four main journals rotatably supported by bearings and
Three crank pins arranged eccentrically with respect to the main journal,
Six crank arms connecting the main journal and the crank pin,
A crankshaft for a 3-cylinder engine equipped with
From one end side in the axial direction, the four main journals are the first to fourth main journals, the three crank pins are the first to third crank pins, and the six crank arms are the first to sixth crank arms. It ’s a crank arm,
Further, a first counterweight connected to the first crank arm, a second counterweight connected to the second crank arm, a fifth counterweight connected to the fifth crank arm, and a sixth counterweight connected to the sixth crank arm. With a counterweight,
The second counterweight is lighter than the first counterweight so that the synthetic inertial force acting on the second main journal can be reduced as compared with the case where the first and second counterweights have the same mass. And
The fifth counterweight is lighter than the sixth counterweight so that the synthetic inertial force acting on the third main journal can be reduced as compared with the case where the fifth and sixth counterweights have the same mass. And
When viewed from one end side in the axial direction, the forward rotation direction of the first to fourth main journals is the + θ direction, and the reverse rotation direction is the −θ direction.
The −θ direction end of the second counterweight is arranged so as to be offset in the + θ direction from the −θ direction end of the first counterweight.
A crankshaft characterized in that the + θ direction end of the fifth counter weight is arranged so as to be displaced in the −θ direction from the + θ direction end of the sixth counter weight. A synthetic inertial force for calculating the synthetic inertial force acting on the second and third main journals when the first and second counterweights have the same mass and the fifth and sixth counterweights have the same mass. Calculation steps and
A weight reduction step of reducing the weight of the second counterweight with respect to the first counterweight and reducing the weight of the fifth counterweight with respect to the sixth counterweight so that the synthetic inertial force becomes smaller.
The method for setting the mass of a crankshaft counterweight according to any one of claims 1 to 4.

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