JP2011074994A - Built-up crankshaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a built-up crankshaft with a crank pin press-fitted in a crank arm and held by a key not to relatively rotate, preventing a defect such as collapse of the key and expansion of a key groove. <P>SOLUTION: The crank pin 7 is press-fitted in a pin hole 15 of the side crank arm 8. The key groove 26 is formed across the pin hole 15 and the crank pin 7 and the key 16 is press-fitted in the key groove 26. The pin hole 15 and the key 16 are provided at a position shifted by about 40 to 50 degrees from the upper ends of the pin hole 15 and the crank pin 7 in a direction opposite to the revolution direction (a) with reference to the top dead center of a piston. As the key groove 26 and the key 16 are provided in a non-pressure receiving area S2 where pressing force is not applied in an explosion stroke, the phenomena of expansion of the key groove 26 and collapse of the key 16 do not occur and the function of the key 16 is maintained surely. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an assembled crankshaft used in a reciprocating internal combustion engine such as a gasoline engine or a diesel engine.

  In a reciprocating internal combustion engine in which a piston reciprocates in a cylinder bore, a crankshaft having a central shaft, a crankpin, and a crank arm (crank web) is used to convert the reciprocating motion of the piston into rotational power.

  This crankshaft is classified into an integral product by casting as a whole and an assembling type composed of a plurality of parts. An example of the latter is described in Patent Document 1, for example, and the assembly is performed by press-fitting a crank pin into the crank arm with the central shaft and the crank arm as an integral part. Employing such an assembly type has the advantage that parts can be shared even if the number of cylinders is different, and that the center shaft and crankpin are polished and the oil passage is easily processed.

  The crankshaft of Patent Document 1 is such that a connecting rod is directly connected to a crankpin, and the connecting rod reciprocates with the piston while rotating with respect to the axis of the cylinder bore. Converted to axis rotation. However, when the connecting rod is reciprocated while changing the angle, the piston rod and cylinder bore are subject to wear because the piston rod and the cylinder bore are subject to an external force that changes the angle of the connecting rod. There were problems such as large sliding resistance (energy loss). Therefore, an internal combustion engine in which the connecting rod does not rotate but only reciprocates has been proposed.

  An example of this is disclosed in Patent Document 2, which will be described below based on the schematic diagram of FIG. That is, first, a large-diameter rotation collar 32 is rotatably fitted to the large end portion 31 a of the connecting rod 31 connected to the piston 30, and the rotation collar 32 is connected in an eccentric state to the crankpin 34 of the crankshaft 33. By setting the eccentric dimension in which the axis O3 of the rotation collar 32 is eccentric from the crankpin 34 to the same dimension e as the eccentric dimension of the crankpin 34 with respect to the rotation center axis O1, the rotation collar 32 rotates the crankshaft 33. It is allowed to rotate around the axis O2 of the crank pin 34 while revolving around the central axis O1.

  Further, the rotating collar 32 is provided with a planetary gear 35 concentric with the crankpin 34, while the engine body is provided with an internal gear 36 having twice the number of teeth of the planetary gear 35, and the planetary gear 35 is connected to the internal gear. By engaging with 36, the rotation collar 32 is restricted so as to rotate in the direction opposite to the direction of rotation (rotation direction) of the crank pin 34, so that the connecting rod 31 does not rotate but only reciprocates. To do. The central shaft 37 of the crankshaft 33 and the crankpin 34 are connected via a crank arm 38, and the central shaft 37 is pivotally supported by the engine body via a bearing 39. The rotation collar 32 and the crank arm 38 are provided with balance weights 40 and 41 for canceling the centrifugal force caused by the eccentricity. Of course, the piston 30 is slidably fitted into the cylinder bore 42.

Japanese Utility Model 56-2415 microfilm Japanese Patent Publication No. 50-39203

  In Patent Document 1, the crank pin is press-fitted into a pin hole provided in the crank arm. However, in order to ensure high durability by simply press-fitting, there is a problem that the machining accuracy of the crank pin and the pin hole has to be extremely high. There is a problem that a large force is required for pressure. In this respect, it is preferable to hold the crankpin and the crank arm so as not to rotate relative to each other by key engagement as means for ensuring an integrated state while ensuring ease of processing and ease of assembly.

  Therefore, the inventors of the present application have studied the position of the key 47 and the key groove 44 in the crank pin 34 and the pin hole 45 on the crankshaft 33 of the internal combustion engine similar to FIG. Found the fact.

  First, as shown in FIG. 5B, the end of the crank arm 38 opposite to the protruding direction of the balance weight 41 (that is, the upper end of the piston 30 when viewed from the position when the piston 30 is at the top dead center). However, since the thickness of the crank arm 38 (thickness measured in the radial direction from the axis of the crank pin 34) is small in this portion, the crank arm 38 becomes thinner when the key groove 44 is formed. There is a possibility of causing a decrease in strength, and therefore, it is not preferable to provide in this portion.

  On the other hand, the portion of the crank arm 38 facing the balance weight 41 has the highest strength. Therefore, in terms of strength, the key groove 44 and the key 47 are directed toward the protruding direction of the balance weight 41 of the crank arm 38. It can be said that it is reasonable to provide it at the end (that is, the position of the lower end when viewed from the posture when the piston 30 is at the top dead center).

  However, when the key groove 44 and the key 47 are provided at the position (C), a strong external force acts on the key 47 and the key groove 44 during the explosion stroke of the engine, and the key 47 is partially crushed or the key groove 44 is opened. For this reason, there is a concern that the crank pin 34 and the crank arm 38 may be displaced when used for a long time. In the internal combustion engine having the rotation collar 32 as shown in FIG. 5 (see Patent Document 2), since the weight of the rotation collar 32 is large, a large inertial force acts on the crankpin 34. It can be said that the problem of the opening of the groove 44 is noticeable.

  The present invention has been made on the basis of such knowledge, and its main object is to provide an assembled crankshaft having excellent strength and durability.

  A crankshaft according to the present invention includes a plurality of central shafts arranged on the same axial center, a crankpin disposed between adjacent central shafts in an eccentric state from the central shaft, the central shaft and the crankpin, The crank pin and one or both of the crank arms are connected together by press-fitting the end of the crank pin into the pin hole of the crank arm, and the piston The basic configuration is that when the reciprocating motion is performed once, the crank pin revolves once around the center axis of the central shaft.

  In addition to the above basic structure, a key groove is formed on the outer peripheral surface of the end portion of the crank pin and the inner peripheral surface of the pin hole so as to face each other. The direction of rotation of the crank pin from the upper end of the outer periphery of the crank pin and the inner periphery of the pin hole, with reference to the position when the piston is at top dead center It is set within a range of approximately half a circumference in the opposite direction.

  In an internal combustion engine, a large pressing force is applied to the crank pin during the process of the piston moving from top dead center to bottom dead center during the explosion stroke, and during the process of moving the piston from bottom dead center to top dead center, A large pressing force is not acting. In addition, the pressing force acting on the crank pin during the explosion stroke is greatest near the start of descent, and gradually decreases as it approaches the bottom dead center.

  As a result of research conducted by the inventors of the present application, as shown by an exaggerated dotted line in FIG. 5 (D), a large bending force acts on the crank pin 34 during the explosion stroke, but the key groove 44 When the key 47 is positioned at the lower end of the crank pin 34 and the pin hole 45 with respect to the top dead center, the largest bending force acting on the crank pin 34 acts on the key 47 as it is, and as a result The pin hole 45 tends to be crushed and deformed due to an excessive compressive force acting on the end 47a of the key 47 opposite to the crank arm 38, while the pin hole 45 is located at the back and upper end of the pin hole 45. The portion 45a is pushed up by the crank pin 34, and tends to open in the vertical direction. Thus, a large external force due to the bending of the crank pin 34 is applied to the key 47 and the key groove 44 in one piece. To act in the Ri state, it was found to cause the opening of the collapse and the pin hole 45 of the key 47.

  On the other hand, according to the configuration of the present invention, it is possible to prevent the pressing force of the piston from directly acting on the key and the key groove via the crank pin in the explosion stroke, so that the key is deformed and the key groove is deformed. Can be prevented or significantly suppressed.

  In other words, the crank pin is pressed through the connecting rod in the explosion stroke, and the connecting rod is pushed in the return stroke. Therefore, the outer peripheral surface of the crank pin and the inner peripheral surface of the pin hole are separated from the pressure receiving portion that receives the explosive force and the explosion. There is a non-pressure-receiving part where no force is applied, and each half-round, and when the piston is at top dead center, the crankpin rotation from the upper end of the outer periphery of the crankpin and the inner periphery of the pinhole The range of the half circumference toward the moving direction is the pressure receiving part, and the remaining half circumference is the non-pressure receiving part.However, in the present invention, the key groove and the key are provided in the non-pressure receiving part. Can be prevented from acting on the key and the key groove, and as a result, crushing deformation of the key and opening deformation of the key groove can be prevented or significantly suppressed.

It is a vertical front view of an embodiment. It is a vertical front view of the principal part. (A) is a sectional view taken along line IIIA-IIIA in FIG. 2, (B) is a sectional view taken along line IIIB-IIIB in FIG. 2, and (C) is a sectional view taken along line IIIC-IIIC in FIG. (A) is a partially broken separated front view of the crankshaft, (B) is an explanatory diagram showing an enlarged view of the main part of FIG. 3 (A), (C) is another example and is a view similar to (B). (D) is a DD sectional view of (C). (B) Hatching is omitted in (C). (A) is a schematic diagram of the prior art, (B) is a first assumption diagram of the arrangement positions of keys and key grooves, (C) is a second assumption figure of the arrangement positions of keys and key grooves, and (D) is (C FIG. In (B), (C), and (D), hatching is omitted.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description, the terms “left and right” and “front and back” are used to specify the direction, which is a state seen from a direction orthogonal to the rotation axis of the crankshaft and the axis of the cylinder bore (ie, FIG. 1). It is based on the condition of looking straight ahead. “Up and down” is based on the reciprocating direction of the piston.

(1). Outline of Structure This embodiment is applied to an internal combustion engine of a type in which the connecting rod does not rotate but only reciprocates as in Patent Document 2. First, an outline will be described with reference to FIGS. This internal combustion engine is a two-cylinder four-cycle system. Accordingly, two cylinder bores 2 are formed in parallel in the engine body (cylinder block) 1, and a piston 3 is slidably fitted in each cylinder bore 2 with the same phase.

  A crankshaft 4 extending in the direction in which the pistons 3 are arranged is disposed below the piston 3. The crankshaft 4 has three rotation center axes, that is, a side rotation center shaft 5 located near one end and the other end of the crankshaft 4 and a center rotation center shaft 6 located substantially in the middle of the left and right sides. A crankpin 7 is arranged at a position between the rotation center shafts 5 and 6 while being eccentric from the rotation axis O1 of the rotation center shafts 5 and 6 by a dimension E. The crankpin 7 is connected via a side crank arm 8 and a center crank arm 9.

  The rotation center shafts 5 and 6 are rotatably held by a first journal 10 fixed to the engine body 1. A main boss portion 11 to which a pulley or a gear is fixed is provided on one of the left and right side rotation center shafts 5, and a sub boss portion 12 to which a flywheel is fixed to the other side rotation center shaft 6. Is provided. The crank arms 8 and 9 are integrally provided with a first balance weight 13 and a second balance weight 14 that protrude in a direction opposite to the eccentric direction.

  The left and right crank pins 7, the center crank arm 8, and the center rotation center shaft 6 are integrally structured, and the left and right side rotation center shaft 5 and the side crank arm 8 are also integrally structured. Therefore, the crankshaft 4 of the present embodiment is composed of three members, and the front ends of the left and right crankpins 7 are press-fitted into the pin holes 15 provided in the side crank arm 8. The crankpin 7 and the side crank arm 8 are held by a key 16 so as not to be relatively rotatable (details will be described later). The outer diameter D2 of the crankpin 7 is set to about half of the outer diameter D1 of the rotation center shafts 5 and 6.

  An idle rotor 18 is fitted to the crank pin 7 from the outside via a second journal 17. The idler rotor 18 has a groove-shaped perfect circular drum portion 19 having a diameter larger than that of the rotation center shafts 5 and 6, and this perfect circular drum portion 19 is connected to the large end portion (bearing portion) 20a of the connecting rod 20. It is held from the outside so as to be relatively rotatable. The lower half of the large end 20 a of the connecting rod 20 is composed of a lower member 20 b of another part, and is fastened to the upper half with a bolt 21. The upper end of the connecting rod 20 is connected to the piston 3 by a piston pin or the like, but the connecting structure is omitted in the drawing.

  In the idle rotor 18, a portion eccentric from the rotation center O <b> 3 of the perfect circular drum portion 19 is fitted to the crank pin 7. The eccentric dimension of the idler rotor 18 with respect to the crankpin 7 and the eccentric dimension of the crankpin 7 with respect to the rotation center shafts 5 and 6 are set to the same dimension E. The idler rotor 18 is integrally provided with a third balance weight 22 in a state of being close to the center crank arm 9. The third balance weight 22 protrudes toward the side opposite to the axis O3 of the idle rotor 18 with the crank pin 7 interposed therebetween.

  The left and right idler rotors 18 are integrally provided with a small-diameter cylindrical portion 23 projecting to the opposite side (ie, the outside) of the center crank arm 9, and a planetary gear 24 is fixed to the cylindrical portion 23 (planetary planet). The gear 24 may be integrally formed with the idler rotor 18). On the other hand, an internal gear 25 with which the planetary gear 24 meshes is fixed to the engine body 1. The number of teeth of the internal gear 25 is set to twice the number of teeth of the planetary gear 25.

(2). Key Details and Summary of Embodiments Next, the key 16 will be described mainly with reference to FIGS. 4 (A) and 4 (B). The key 16 has a quadrangular prism shape, and is fitted in a key groove 26 provided opposite to the crank pin 7 and the pin hole 15. The key 16 hardly protrudes (or at all) from the side crank arm 8 so as not to interfere with the second journal 17. The width of the key 16 measured in the radial direction of the crankpin 7 is set to be approximately the same as the radius of the crankpin 7. Of course, the size (length, width dimension, thickness) of the key 16 can be arbitrarily set as required.

  FIG. 4 (A) depicts a state in which the piston 3 is located at the top dead center. Therefore, the first balance weight 13 of the side crank arm 8 faces downward. 4B, the positions of the key groove 26 and the key 16 as viewed from the axial direction of the crankpin 7 (more precisely, the position of the center line O4 extending in the radial direction of the crankpin 7). In the circumferential direction from the upper end of the outer periphery of the crankpin 7 and the inner periphery of the pin hole 15 toward the direction opposite to the revolution direction a of the crankpin 7 with reference to the posture when the piston 3 is at the top dead center. It is provided at the place where the shift is about 45 degrees.

  In other words, the keyway 26 and the key 16 move in the direction opposite to the revolution direction a of the crankpin 7 from the upper end of the pinhole 15 and the crankpin 7 with reference to the time when the piston 3 is at the top dead center. The angle θ is set to about 45 degrees. θ is preferably about 40 to 50 degrees.

  Now, when the piston 3 descends in the explosion stroke, the pressing force associated with the lowering of the piston 3 acts on the crank pin 7 via the idle rotor 18, and the crank arms 8 and 9 revolve due to this pressing force, thereby rotating. The center shafts 5 and 6 rotate (spin). Accordingly, the pressing force of the crank pin 7 acts on the pin hole 15. Further, the pressing force acting on the crankpin 7 gradually decreases as the piston 3 approaches the bottom dead center.

  The pressure receiving center position O5 at which the pin hole 15 receives the pressing force of the crank pin 7 is located at the lower end when the piston 3 is at the top dead center, and in the revolving direction of the crank pin 7 as the piston 3 moves downward. When the piston 3 moves and is located at the bottom dead center, the second balance weight 13 is located on the opposite side. Therefore, in the state of FIG. 4A, the left half of the inner peripheral surface of the pin hole 15 and the outer peripheral surface of the crank pin 7 is the pressure receiving area S1 with the longitudinal center line O6 of the second balance weight 13 as a boundary. The right half is a non-pressure receiving area S2 (actually, the crank pin 7 and the pin hole 15 are in surface contact, so the range of the non-pressure receiving portion S2 is narrower than the half circumference).

  Since the key groove 26 and the key 16 are provided in the non-pressure receiving portion S2, a strong pressing force is not applied to the key 16 through the crank pin 7. As a result, the key 16 is crushed or the key groove 26 is not pressed. There is no such phenomenon as opening.

  By the way, when the crankpin 7 revolves during the explosion stroke, the bending force acting on the crankpin 7 becomes smaller from the top dead center toward the bottom dead center. On the other hand, since the crank arms 8 and 9 continue to be prevented from rotating due to the engine load, the crank pin 7 is connected to the crank arms 8 and 9 between the crank arms 8 and 9 and the crank pin 7. A torsional force that tries to rotate relative to the acting force is applied, and this torsional force depends on a moment that causes the crank arms 8 and 9 to rotate. This is the product of the dimension (span) eccentric from the axis of the cylinder bore 2 and the pressing force acting on the crankpin 7 via the connecting rod 20.

  The bending force acting on the crankpin 7 increases as the piston 3 approaches the bottom dead center. Therefore, if only the bending of the crankpin 7 is taken into consideration, the key groove 26 and the key 16 are the same when the piston 3 is at the top dead center. Although it can be said that it is preferable to position it at the upper ends of the crank pin 7 and the pin hole 15, this concentrates the stress and weakens the strength of the side crank arm 8. On the other hand, when θ is set to about 40 to 50 degrees as in the present embodiment, there is an advantage that the influence of the bending of the crankpin 7 can be effectively suppressed without causing the strength of the side crank arm 8 to decrease. θ is particularly preferably in the range of 40 to 50 degrees, but the effect can be obtained even if it is in the range of more than 0 and 90 degrees.

(3) Modification Now, the crankshaft 4 needs to be integrated as a whole after assembly, and for this purpose, the key 16 should fit into the key groove 26, and therefore the key 16 16 is also press-fitted into the key groove 26. However, since the side crank arm 8 is thin on the side opposite to the second balance weight 13, there is a concern that the opening end of the key groove 26 is expanded and deformed by the press-fitting of the key 16.

  This concern can be eliminated by providing a substantially annular reinforcing rib 27 on a portion of the side crank arm 8 opposite to the side central shaft 5 as shown as a modification in FIGS. More specifically, when the thickness of the second side crank arm 8 is increased as a whole, the first balance weight 13 must be increased in size, but a reinforcing rib 27 is provided only on a part of the side crank arm 8 as in the modification. As a result, it is possible to prevent the pin hole 15 from being opened as shown in an exaggerated manner by a one-dot chain line in FIG. 4D without causing an increase in the size of the first balance weight 13.

  The thickness t of the reinforcing rib 27 is preferably 1/3 to 1/2 of the press-fit depth H of the crankpin 7, and the height H1 of the rib 27 is 1/2 to the thickness H0 of the side crank arm 8. About 1.0 times was suitable (that is, if it is smaller than that, the effect is not exhibited, and if it is larger than that, the effect is not changed).

(4). Others The present invention can be embodied in various ways other than the above embodiment. For example, the number of cylinders is not limited to two, but can be applied to an internal combustion engine having a single cylinder or three or more cylinders. The present invention can also be applied to an internal combustion engine that reciprocates while the connecting rod rotates. In the case where the crankshaft is provided with a center crank arm in an internal combustion engine having two or more cylinders, the present invention can be applied with the crank pin and the center crank arm being press-fitted.

  The present invention can be applied to an internal combustion engine to exhibit its usefulness. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Cylinder bore 3 Piston 4 Crankshaft 5,6 Rotation center shaft 7 Crank pin 8 Side crank arm 9 Center crank arm 15 Pin hole 16 Key 18 Free-rotating rotor 20 Connecting rod 24 Planetary gear 25 Internal gear 26 Key groove 27 rib

Claims (1)

A plurality of central axes arranged on the same axis, a crank pin disposed between adjacent central axes in a state of being eccentric from the central axis, and a plurality of crank arms connecting the central axis and the crank pin Have
The crank pin and one or both of the crank arms on both sides thereof are integrally connected by press-fitting the end of the crank pin into a pin hole of the crank arm, and when the piston reciprocates once, the crank pin Revolves once around the central axis of the central axis,
The structure
Opposite key grooves are formed on the outer peripheral surface of the end portion of the crank pin and the inner peripheral surface of the pin hole, and the key is fitted to the key groove, and the key groove as viewed from the axial direction of the crank pin And the position of the key from the upper end of the outer periphery of the crank pin and the inner periphery of the pin hole from the top when the piston is at the top dead center, approximately half a circumference in the direction opposite to the revolution direction of the crank pin. Set within the range of
Assembled crankshaft for internal combustion engines.

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