JPH0533674A - Engine structure - Google Patents

Abstract

PURPOSE:To provide an engine structure capable of reducing any effect due to the weight of a piston or the like exerting on a cylinder wall and enabling said weight to act on controlling a piston slap, in the cylinder slant engine. CONSTITUTION:A crankshaft center O is so constituted as being offset to a lower side as far as a specified value: X, with an intersection of a vertical straight line A-A passing through a cylinder center line and this crankshaft center line. With this offset value: X set properly, thrust force: FN1 acting on a cylinder wall by dint of combustion pressure acting on the opposite cylinder wall and a component force: W1 of weight of a piston or the like acting on the cylinder wall both are balanced, thereby making them act so as to be offset with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine structure of a so-called slant engine in which a cylinder center line is arranged obliquely with respect to a vertical direction in a plane orthogonal to a crankshaft direction.

[0002]

2. Description of the Related Art In a reciprocating engine, when the compression stroke shifts to the explosion stroke, the piston fits in the cylinder in a direction orthogonal to the axial direction in association with the change in the angle of a connecting rod connecting the piston and the crankshaft. The sliding contact surface changes due to the movement of the joint gap, and at this time, the piston is struck on the cylinder wall surface, causing so-called piston slap. That is, FIG.
As shown in FIG. 5, the piston 2 abuts on the wall surface 1A on the downstream side in the crankshaft rotation direction of the cylinder 1 during the compression stroke as shown in FIG. 4 and slides, and during the explosion stroke, as shown in FIG. First, due to the pressure of the combustion gas (combustion pressure), the top portion is shaken by the gap around the piston pin P as shown by an imaginary line in the figure and collides with the wall surface 1B on the other side (piston slap), and then the colliding side ( (Thrust side)
It comes into contact with the wall surface 1B of the and slides. Such a piston slap is particularly noticeable at the time of idling in a cold state where the fitting gap between the cylinder and the piston is large, and in extreme cases, scuffing may occur. Therefore, the piston pin P
Is eccentric to the thrust side from the center of the piston 2 to suppress the movement of the piston. (Actual development 6
By the way, recently, there is a so-called cylinder slant in which the engine is mounted by inclining the engine obliquely with respect to the vertical direction in a plane where the cylinder center line is orthogonal to the crankshaft direction.
Further, in a V-type engine in which cylinders are arranged on the left and right sides of a vertical line passing through the center of the crankshaft, the V-type engine inevitably becomes a cylinder slant.

[0003]

2. Description of the Related Art In such a cylinder slant engine, the weight of the piston and the connecting rod connected to the piston acts on the lower cylinder wall surface, and the piston behavior varies depending on the inclination angle direction and angle. Occurs. That is, as shown in FIG. 6, when the cylinder 1 is slanted to the upstream side (the left side in the drawing) of the crankshaft 4 in the rotational direction, the weight W of the piston 2 and the connecting rod 3 is W, the component force W1 acting on the cylinder wall surface. Then, the combustion pressure FP presses the piston 2 against the cylinder wall surface, and the component force (thrust force) FN acts on the wall surface 1B on the same side of the cylinder 1. on the other hand,
As shown in FIG. 7, when the cylinder 1 is slanted to the downstream side (the right side in the drawing) of the crankshaft 4 in the rotational direction, the weight component of the piston 2 and the connecting rod 3 is W: , Thrust force: FN acts on the opposite wall surfaces 1A and 1B, respectively. Therefore, in the V-type engine,
Even if the left and right banks are arranged at the same angle with respect to the vertical line passing through the center of the crankshaft, the left and right banks will have different piston behaviors, and as a result, the piston pin and piston When adopting the configuration of eccentricity from the center of the left and right banks, in order to make the piston behavior of the left and right banks the same condition, it is necessary to set different eccentricity of the piston pins on the left and right banks, and it is not possible to standardize It becomes extremely irrational and complicated, such as the number of types of parts increasing.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention can reduce the influence of the weight of the piston or the like acting on the cylinder wall in a cylinder slant engine and suppress the piston slap. An object of the present invention is to provide an engine structure that can be operated. It is another object of the present invention to provide an engine structure capable of making the piston behavior of the left and right banks uniform in a V-type engine.

[0005]

Therefore, in the engine structure according to the present invention, in the cylinder slant engine in which the cylinder centerline is obliquely arranged with respect to the vertical direction in the plane orthogonal to the crankshaft direction, the crankshaft The center is the cylinder center line,
It is configured to be offset downward by a predetermined amount with respect to an intersection of a vertical line passing through the center of the crankshaft. As a result, when the cylinder is slanted to the upstream side in the rotation direction of the crankshaft, the component force (thrust force) of the combustion pressure pressing the piston against the cylinder wall surface can be suppressed. On the other hand, when the cylinder is slanted on the downstream side in the direction of rotation of the crankshaft, the component force of the weight of the piston acting on the opposite cylinder wall surfaces and the combustion pressure press the piston against the cylinder wall surface. It is possible to balance the component force (thrust force) that occurs and to act so as to cancel each other out. Further, in an engine in which the cylinder center line is arranged obliquely to the vertical direction in a plane orthogonal to the crankshaft direction, the combustion force acting on the piston acts on the cylinder wall surface on which the weight of the piston acts. It is configured to include a suppressing unit that suppresses the occurrence of The suppressing means is configured, for example, by arranging the piston pin in an offset manner on the side opposite to the inclination direction of the cylinder center line with respect to the vertical line passing through the crankshaft center,
The spark plug is offset from the center of the cylinder in the direction opposite to the direction of inclination of the cylinder center line. Further, in a V-type engine in which cylinders are arranged on the left and right sides of a vertical line passing through the center of the crankshaft, the center of the crankshaft is located at an intersection of the cylinder centerline and the vertical line passing through the center of the crankshaft. It is configured by being offset to the lower side of the fixed amount. Thus, by appropriately setting the offset amount with respect to the intersection of the center of the crankshaft and the vertical line passing through the center of the crankshaft and the center of the crankshaft, the component force and combustion pressure of the weight of the piston acting on the cylinder wall face the piston. The combined force with the thrust force pressing against the cylinder wall surface can be set to be the same in the left and right banks, and the behavior of the pistons in the left and right banks can be made uniform.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of an embodiment of an engine structure according to the present invention. The illustrated engine structure is the crankshaft 4.
The cylinder is arranged at a predetermined angle α with respect to the vertical line AA passing through the center of the crankshaft 4 on the downstream side in the rotation direction of the crankshaft 4. The crankshaft center O is offset by a predetermined amount X below an intersection O'of a vertical line AA passing through the crankshaft center O and a cylinder centerline indicated by a two-dot chain line in the figure. Here, α: slant angle of the cylinder center line with respect to a vertical line AA passing through the center of the crankshaft 4: length r of the connecting rod 3: crank pin offset amount (rotation radius) λ: L / of the crankshaft 4 r θ: Crank angle X: Offset amount of crankshaft center O Pmax: Combustion pressure (combustion gas pressure in cylinder) FP: Force of combustion pressure acting on piston FN: Crankshaft center O not offset (X =
0) Thrust force caused by combustion pressure FN1: Thrust force φ when crankshaft center O is offset by a predetermined amount: X: Crankshaft center O is not offset at crank angle = θ (X = 0) Angle of the connecting rod 4 with respect to the cylinder centerline at 1: The angle W of the connecting rod 4 with respect to the cylinder centerline when the center O of the crankshaft is offset by a predetermined amount at the crank angle = θ: X: Weight W1 of the piston, etc. : Component force of weight of piston acting on cylinder wall surface D: When piston diameter is used, thrust pressure: FN generated by combustion pressure: Pmax without offset of crankshaft center O (X = 0) is FN = FP × tan φ The angle φ1 of the connecting rod 4 with respect to the cylinder center line at the crank angle = θ is:

[Equation 2] Therefore, the thrust force FN1 when the crankshaft center O is the offset amount X is

[Equation 3] Here, the component force of the weight of the piston, etc .: W acting on the cylinder wall surface: W1, is W1 = W × sin α, and the offset amount X of the crankshaft center O is set so that W1 = FN1. The thrust force acting on the wall surface of the cylinder due to the combustion pressure and the component force of the weight of the piston or the like can be balanced so as to cancel each other. That is,

[Equation 4]

[Equation 5] From

[Equation 6] By offsetting the offset amount X obtained by this and the crankshaft center O, the behavior of the piston is stabilized and the piston slap is suppressed. In this embodiment, the center O of the crankshaft is offset downward with respect to the intersection of the vertical line AA passing through the center O of the crankshaft and the centerline of the cylinder. Even if it is offset to the upstream side (thrust side) in the rotation direction of 4, the same effect can be obtained. In this case, the offset amount Y of the piston pin P may be set to Y = X × sin α using the offset amount X of the crankshaft center O described above. It is also possible to use the offset of the crankshaft center O and the offset of the piston pin P together, and in that case, it is sufficient to set W1 = FN1 by combining the offsets of both. Is. Thus, as described above, the crankshaft center O
Offsetting thrust force caused by combustion pressure: FN
It is possible to cancel with, the piston slap is suppressed, and the behavior of the piston is stabilized. Next, another embodiment of the present invention whose conceptual diagram is shown in FIG. 2 will be described. In the figure, the same parts as those in the above-described embodiment are designated by the same reference numerals, and the description thereof is omitted. This is a V-type engine in which cylinders are arranged on the left and right with a vertical line AA passing through the center O of the crankshaft sandwiched between the vertical line AA passing through the center O of the crankshaft 4. The cylinders of the bank are arranged at a predetermined angle: α. The crankshaft center O is offset downward by a predetermined amount X with respect to an intersection O'of a vertical line AA passing through the crankshaft center O and the cylinder centerlines of the left and right banks shown by the two-dot chain line in the figure. As a result, the force acting on the cylinder wall surface of the pistons of the left and right banks can be made uniform, and the piston behavior can be set evenly. That is, the weight of the piston of the left bank, etc .: component force acting on the cylinder wall surface of W:
WL is WL = W × sin α When the crankshaft center O is the offset amount: X, the thrust force: FNL is

[Equation 7] The component force acting on the cylinder wall surface of the weight of the piston etc. of the right bank is WR = W × sin α When the crankshaft center O is the offset amount: X, the thrust force: FNR is

[Equation 8] Here, by setting the offset amount of the crankshaft where X satisfies FNL + WL = FNR + WR: X, the forces acting on the cylinder wall surfaces of the pistons of the left and right banks become equal. That is,

[Equation 9] From

[Equation 10] Therefore,

The offset amount of the crankshaft: X is obtained as follows. Then, the offset amount obtained as described above: X
By offsetting the crankshaft to the lower side, the forces acting on the cylinder wall surfaces of the pistons in the left and right banks are made uniform, and as a result, the piston behavior becomes even in the left and right banks, improving balance and making the left and right banks even. Can be used as pistons having the same specifications, and parts can be shared. As an example, the specification of each part is V type engine with α: 30 ° L ： 14.60 cm r ： 3.87 cm λ ： L / r = 3.78 cm W ： 0.776 kg D ： 9 cm, especially piston slap is a problem. Assuming that the engine is idling, the calculation is performed under the condition of θ: 5 to 15 ° Pmax: 2 to 6 kg / cm 2, and a result of X = 0.04 to 0.11 cm is obtained. That is, under the above conditions, the crankshaft center O is offset downward by that amount with respect to the intersection O'of the vertical line AA passing through the crankshaft center O and the cylinder centerline, and the pistons of the left and right banks are thus offset. The forces acting on the cylinder wall surface are uniform. FIG. 3 shows another embodiment of the present invention, in which the cylinder 1 slants a predetermined angle upstream of the crankshaft 4 in the rotational direction of the crankshaft 4 with respect to a vertical line AA passing through the center O of the crankshaft 4. In the engine arranged in parallel, the spark plug 5 is arranged on the side opposite to the slant by a predetermined amount: B offset. As a result, the combustion gas pressure first acts on the portion of the piston 2 closer to the ignition plug 5, so that the movement of the piston 2 to the thrust side is suppressed and slap is prevented.

[0015]

As described above, according to the engine structure of the present invention, in the engine of the cylinder slant, the component force of the weight of the piston or the like acting on the cylinder wall acts so as to suppress the piston slap. Thus, the influence of the weight of the piston or the like on the cylinder wall on the cylinder behavior can be reduced, and the piston slap can be suppressed. Further, in the V-type engine, the piston behaviors of the left and right banks can be made uniform, the engine balance can be improved, and the same pistons can be used in the left and right banks, resulting in cost reduction due to commonization. It will be possible.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an embodiment of an engine structure according to the present invention.

FIG. 2 is a conceptual diagram of another embodiment of the present invention.

FIG. 3 is a conceptual diagram of another embodiment of the present invention.

FIG. 4 is a diagram illustrating a piston slap.

FIG. 5 is a diagram illustrating a piston slap.

FIG. 6 is an explanatory diagram of a force acting on a cylinder wall surface when the cylinder is slanted on the upstream side in the rotation direction of the crankshaft.

FIG. 7 is an explanatory view of a force acting on a cylinder wall surface when the cylinder is slanted on the downstream side in the rotation direction of the crankshaft.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder 2 ... Piston 3 ... Connecting rod 4 ... Crankshaft 5 ... Spark plug AA ... Vertical line 0 passing through the center of the crankshaft 0 ... Crankshaft center 0 '... Intersection point between the centerline of the cylinder and the vertical line passing through the center of the crankshaft P ... Piston pins FN, FN1, FNL, FNR ... Thrust force FP ... Force acting on the piston at combustion pressure

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuhide Tahara             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation (72) Inventor Mitsuyuki Muroya             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation (72) Inventor Shinji Asami             3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda             Within the corporation

Claims (7)

[Claims] 1. An engine in which a cylinder center line is arranged obliquely with respect to a vertical direction in a plane orthogonal to the crank shaft direction, wherein the crank shaft center is the cylinder center line and the crank shaft center. An engine structure characterized by being configured by being offset downward by a predetermined amount with respect to an intersection of a vertical line passing through. 2. A cylinder in which a combustion force acting on a piston acts on a piston, in which the cylinder centerline is arranged obliquely with respect to the vertical direction in a plane orthogonal to the crankshaft direction. An engine structure characterized in that the engine structure is provided with a suppressing means that suppresses acting on a wall surface. 3. The piston pin is offsetly arranged on the side opposite to the direction of inclination of the cylinder center line with respect to a vertical line passing through the center of the crankshaft, according to claim 2. Engine structure. 4. A V-type engine having left and right cylinders sandwiching a vertical line passing through a center of a crankshaft, wherein a piston pin of a cylinder on an upstream side in a rotation direction of the crankshaft is opposite to an inclination direction of a cylinder centerline. The engine structure according to claim 3, wherein the engine structure is offset on the side. 5. The engine structure according to claim 2, wherein the suppressing means is formed by offsetting the spark plug from the center of the cylinder in a direction opposite to the direction of inclination of the cylinder center line. 6. A V-type engine in which cylinders are arranged on the left and right sides of a vertical line passing through the center of a crankshaft, wherein the center of the crankshaft is a cylinder centerline and a vertical line passing through the center of the crankshaft. An engine structure characterized by being configured by being offset downward by a predetermined amount with respect to the intersection. 7. An offset amount of the center of the crankshaft with respect to an intersection of a vertical line passing through the centerline of the cylinder and the center of the crankshaft is expressed by the following formula: The engine structure according to claim 6, wherein the engine structure is configured as follows.