JP2008069679A - Variable stroke characteristics engine - Google Patents

Abstract

A variable stroke characteristic engine improved to reduce an average value of sliding resistance loss during reciprocation of a piston is provided.
Stroke characteristics variable in which a piston stroke is changed by connecting a piston 3 and a crankshaft 6 with first and second links 4 and 5 and changing a second link motion restraint state. In the engine, a connection center between the first link and the second link at the top dead center in the minimum compression ratio state or the maximum displacement state, and the first link at the top dead center in the maximum compression ratio state or the minimum displacement state. The connection center with the second link is located on both sides of the movement center axis of the piston pin 10.
[Selection] Figure 5

Description

  The present invention relates to a variable stroke characteristic engine, and more particularly to a variable stroke characteristic engine capable of reducing a sliding resistance loss of a piston.

The piston (9) and the crankpin (5) are connected by an upper link (3) (first link) and a lower link (4) (second link), and are eccentrically supported by the lower link and the engine body. The cam (8) is connected with the control link (7), and the eccentric stroke is rotated to change the movement restraint state of the lower link, so that the piston stroke can be continuously changed. A variable stroke characteristic engine is known (see Patent Document 1).
JP 2002-215902 A

  However, according to the configuration described in Document 1, if the angle formed between the motion center axis of the piston pin (cylinder center axis) and the upper link is φ, φ is between the top dead center and the maximum piston speed. The link geometry (link geometrical relationship) is set so that the absolute value of φ is smaller than that at the top dead center at the point where zero (combustion load) x (piston speed) is reached. ing.

  Certainly, when considering the reduction of the sliding resistance loss between the piston and the cylinder, if the coefficient of friction between the piston and the cylinder, including lubrication, is constant over the entire rotation range of the crankshaft, It is desirable that the angle formed by the cylinder center axis and the upper link be minimized during the expansion stroke in which the piston load on the line is maximized.

  However, the coefficient of friction between the piston and cylinder changes with changes in the crank rotation angle depending on the temperature and lubrication conditions (up and down sliding of the oil ring), and the angle formed between the cylinder center axis and the upper link is large. As a result, the component force in the direction perpendicular to the cylinder center axis acting on the piston increases, so the friction coefficient and sliding resistance loss between the piston and cylinder do not increase in proportion to the piston load alone. .

  In addition, if φ is set to be small between the top dead center and the maximum piston speed, the maximum inclination angle φmax (absolute value, hereinafter the same) of the upper link will inevitably increase. Sliding resistance loss increases.

  The present invention has been devised to eliminate such disadvantages of the prior art, and its main purpose is to improve the stroke to reduce the average value of the sliding resistance loss during the reciprocating motion of the piston. It is to provide a variable characteristic engine.

In order to solve such a problem, claim 1 of the present invention changes the motion restraint state of the first and second links 4 and 5 connecting the piston 3 and the crankshaft 6 and the second link. In a variable stroke characteristic engine having variable means (control link 12, eccentric shaft 13) to be operated, the connection center between the first link and the second link at the top dead center in the lowest compression ratio state or the maximum displacement amount state, and the highest The connection center of the first link and the second link at the top dead center in the compression ratio state or the minimum displacement amount state is positioned on both sides of the movement center axis of the piston pin 10 on a plane orthogonal to the crankshaft. It was supposed to be.
In particular, in the engine configured as described above, the interval between the movement center axis of the piston pin and the connection center between the first link and the second link at the top dead center in the direction perpendicular to the movement center axis of the piston pin, It is preferable that the maximum compression ratio state or the minimum compression ratio state be smaller.
According to a third aspect of the present invention, there is provided a variable stroke characteristic engine having a first and a second link connecting the piston and the crankshaft, and a variable means for changing a motion restraint state of the second link. The connection center of the first link and the second link at the top dead center in the compression ratio state or the minimum displacement amount state is positioned on the motion center axis of the piston pin on a plane orthogonal to the crankshaft.

According to such a configuration of claim 1 of the present invention, the angle φ formed by the movement center axis (y-axis) of the piston pin and the first link can be reduced over the entire range of reciprocation of the piston. The average value of the sliding resistance loss during the reciprocating motion can be reduced. According to claim 2, the angle φ formed between the motion center axis of the piston pin and the first link is minimized at a position close to the maximum compression ratio state in the fuel saving mode, which can contribute to an improvement in fuel consumption. Furthermore, according to the third aspect, the angle φ formed by the movement center axis of the piston pin and the first link is substantially zero, which can greatly contribute to the improvement of fuel consumption.
In particular, in the case of a variable displacement engine, the angle φ formed between the movement center axis of the piston pin and the first link tends to be large. Therefore, if the present invention is applied, the maximum inclination angle φmax can be kept relatively small. This can contribute to a significant reduction in sliding resistance loss during the reciprocating motion of the piston.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  1 to 4 are schematic configuration diagrams in which the upper part is omitted from the cylinder head of a variable compression ratio / displacement engine as an example of a stroke characteristic variable engine to which the present invention is applied. The piston 3 slidably engaged with the cylinder 2 of the engine 1 is connected to the crankshaft 6 through two links, a first link 4 and a second link 5. Note that the valve operating mechanism, intake system, and exhaust system provided in the cylinder head are not different from the conventional 4-cycle engine.

  The crankshaft 6 basically has the same configuration as that of a normal fixed compression ratio engine, and includes a crankpin 9 that is eccentric from a crank journal 8 (a center of rotation of the crankshaft) supported in the crankcase 7. An intermediate portion of the second link 5 that swings in a seesaw manner is supported by the crankpin 9. The large end portion 4b of the first link 4 having the small end portion 4a connected to the piston pin 10 is connected to one end 5a of the second link 5. The crankshaft 6 is provided with a counterweight mainly for reducing the rotational primary vibration component of the piston motion, which is also the same as that of a conventional reciprocating engine and is omitted.

  The other end 5b of the second link 5 is pin-coupled with a small end portion 12a of the control link 12 having the same configuration as a connecting rod for connecting a piston and a crankshaft in a normal engine. The large end portion 12 b of the control link 12 is connected to the eccentric portion 13 a of the eccentric shaft 13 that is rotatably supported by the crankcase 7 and extends parallel to the crankshaft 6, with a two-part bearing hole 14. Has been.

  The eccentric shaft 13 supports the large end portion 12b of the control link 12 so as to be movable within a predetermined range (about 90 degrees in this embodiment) within the crankcase 7, and protrudes outward of the crankcase 7, for example. The rotation angle is continuously changed according to the operating state of the engine 1 by an appropriate rotation actuator (not shown) provided at the shaft end, and is held at an arbitrary angle. Yes.

  According to the engine 1, by rotating the eccentric shaft 13, the position of the large end portion 12b of the control link 12 is changed to the position shown in FIGS. 1 and 2 (horizontal inward / low compression ratio state or large exhaust gas). 3) and the position shown in FIGS. 3 and 4 (vertically downward / high compression ratio state or small displacement state), and the movement restraint state of the second link 5 as the crankshaft 6 rotates, That is, the swing angle changes. As a result, the apparent length of the connecting rod connecting the piston 3 and the crankshaft 6 exhibits an effect as if it changes continuously according to the movement of the piston 3 and is given from the eccentric shaft 13. By changing the position of the support end of the control link 12 with respect to the crankcase 7 by the rotational driving force applied, the compression ratio or the displacement can be arbitrarily changed.

  That is, the first and second links 4 and 5, the control link 12, and the eccentric shaft 13 constitute a piston stroke characteristic variable mechanism, which provides a stroke characteristic variable function for continuously changing the compression ratio or the displacement. It is.

  In this way, the stroke range of the piston 3 in the cylinder 2, that is, the top dead center position and the bottom dead center position of the piston 3 are represented by the range indicated by the symbol A in FIG. 2 and the range indicated by the symbol B in FIG. It will change continuously between.

  In the stroke characteristic variable engine having the above-described configuration, as shown in FIG. 5, the central point of the connecting portion between the first link 4 and the second link 5 is D, and the motion center axis (cylinder center axis) of the piston pin 10 is y. As the axis, the y-axis and the axis orthogonal to the center axis of the crank journal 8 are the x-axis, and the x coordinate at the top dead center of the D point is Dx_TDC, Since the trajectory changes, the link geometry is set such that the Dxh_TDC in the highest compression ratio state or the minimum displacement state and the Dxl_TDC in the lowest compression ratio state or the largest displacement state sandwich the y-axis between them. It was. As a result, the maximum inclination angle φmax of the first link 4 with respect to the y-axis can be reduced, and φ can always be minimized near the top dead center even when the compression ratio or the displacement is changed. That is, according to the present invention, the maximum inclination angle φmax with respect to the y axis of the first link 4 is reduced over the entire rotation range of the crankshaft 6 in the entire variable range of the compression ratio or the displacement, and the piston acting on the piston pin 10 is reduced. 3 is reduced, the friction coefficient between the cylinder 2 and the piston 3 and the average value of the sliding resistance loss can be reduced, and the engine efficiency can be increased.

  In particular, the distance in the x-axis direction between the connection center (Dx_TDC) of the first link 4 and the second link 5 at the top dead center and the movement center axis (y-axis) of the piston pin 10 is set to the maximum compression ratio state or The link geometry may be set so that the interval EDh in the minimum displacement state is smaller than the interval EDl in the minimum compression ratio state or the maximum displacement amount state. As a result, the angle φ formed by the movement center axis (y-axis) of the piston pin 10 and the first link 4 is minimized at a position close to the maximum compression ratio state that is the fuel saving mode, which can contribute to improvement in fuel consumption. .

  Further, the value of EDh is zero, that is, the first link 4 and the second link 5 at the top dead center at the maximum compression ratio state or the minimum displacement amount state on the movement center axis (y-axis) of the piston pin 10. The link geometry may be set so as to place the connection center (Dxh_TDC). As a result, the angle φ formed by the movement center axis (y-axis) of the piston pin 10 and the first link 4 becomes substantially zero, which can greatly contribute to improvement in fuel consumption.

  In the above embodiment, the driving force for moving the large end portion 12b, which is the engine side connecting portion of the control link 12, is provided by rotating the eccentric shaft 13 including the eccentric portion 13a. As long as the position of the engine side connection part of the control link 12 can be changed, this may be one that is moved linearly by other means such as a hydraulic cylinder.

It is a longitudinal cross-sectional view which shows the piston top dead center position in the minimum compression ratio state or the maximum displacement amount state of the engine to which the present invention is applied. It is a longitudinal cross-sectional view which shows the piston bottom dead center position in the minimum compression ratio state or the maximum displacement amount state of the engine to which the present invention is applied. It is a longitudinal cross-sectional view which shows the piston top dead center position in the maximum compression ratio state or the minimum displacement amount state of the engine to which the present invention is applied. It is a longitudinal cross-sectional view which shows the piston bottom dead center position in the maximum compression ratio state or the minimum displacement amount state of the engine to which the present invention is applied. It is explanatory drawing of the exercise | movement of each link.

Explanation of symbols

3 Piston 4 First link 5 Second link 6 Crankshaft 10 Piston pin 12 Control link 13 Eccentric shaft

Claims (3)

A variable stroke characteristic engine having first and second links connecting between a piston and a crankshaft, and variable means for changing a motion restraint state of the second link,
The connection center of the first link and the second link at the top dead center in the lowest compression ratio state or the maximum displacement amount state, and the first link at the top dead center in the highest compression ratio state or the smallest displacement amount state A variable stroke characteristic engine characterized in that a connection center with the second link is located on both sides of a motion axis of a piston pin on a plane orthogonal to the crankshaft.   The interval between the movement center axis of the piston pin and the connection center between the first link and the second link at the top dead center in the direction perpendicular to the movement center axis of the piston pin is the maximum compression ratio. 2. The variable stroke characteristic engine according to claim 1, wherein the engine is smaller in a state or a minimum displacement state. A variable stroke characteristic engine having first and second links connecting between a piston and a crankshaft, and variable means for changing a motion restraint state of the second link,
The connection center between the first link and the second link at the top dead center in the maximum compression ratio state or the minimum displacement state is located on the motion center axis of the piston pin on a plane orthogonal to the crankshaft. Stroke characteristic variable engine characterized by doing so.

Images