JP2010249109A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine having improved fuel cost and reduced vibration by setting a speed increasing timing for a piston to accurately correspond to the rising characteristics of combustion pressure. <P>SOLUTION: To a crank shaft 4 and an output shaft 11, a pair of elliptical gears 12, 13 are journaled, respectively, which engage each other. A crank angle θr is set between a minor axis S1 of the crank shaft side elliptical gear 12 and a major axis L2 of the output side elliptical gear 13 engaging each other so that the piston 3 is moved down at the maximum speed between a crank angle θp showing a combustion pressure peak and a combustion ending crank angle θe. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine in which an output shaft is rotated at a substantially constant speed by providing an inconstant speed power transmission mechanism between a crankshaft connected to the crankshaft and an output shaft.

  Conventionally, it is known to increase the compression ratio (≈expansion ratio) as a means for increasing the thermal efficiency and improving the output in an OT cycle engine, but simply increasing the compression ratio causes knocking. It will be. In particular, knocking is likely to occur because the combustion pressure increases in a high-load operation state.

  Therefore, generally, when the ignition timing is controlled and knocking is detected, the ignition timing is immediately retarded to prevent knocking. However, when the ignition timing is retarded, the maximum combustion pressure in the combustion chamber is lowered, and the thermal efficiency is lowered, and there is a disadvantage that the output is reduced correspondingly.

  As a countermeasure, the applicant of the present application in Japanese Patent Application Laid-Open No. 2005-291103 discloses a pair of elliptical gears meshing with the shaft end of the crankshaft and the shaft end of the output shaft parallel to the crankshaft ( An internal combustion engine that effectively avoids the occurrence of knocking by arranging the two-wheel gear) and making the rotation of the crankshaft faster before and after the top dead center by the mutual rotation of both the elliptical gears. Proposed.

  In the internal combustion engine disclosed in the above-mentioned document, the long shaft side of the elliptical gear mounted on the crankshaft is arranged on the extension of the connecting rod, and the piston is compressed and expanded around the top dead center (TDC). The speed is increased. However, since the combustion pressure peak occurs after the compression top dead center has elapsed, the piston acceleration timing by the elliptical gear attached to the crankshaft and the actual combustion pressure rise characteristic are strictly the same. There is room for improvement in fuel economy.

  Further, since the piston acceleration timing by the elliptical gear attached to the crankshaft does not exactly match the actual combustion pressure rise characteristic, as shown by a thin line in FIG. There is a problem that an acceleration peak of the piston speed appears twice per stroke, causing vibration and noise.

  In view of the above circumstances, the present invention provides an internal combustion engine capable of improving fuel efficiency and reducing vibration by more precisely matching the piston acceleration timing and the actual combustion pressure increase characteristic. With the goal.

  In order to achieve the above object, the present invention provides an internal combustion engine comprising a crankshaft rotating by a vertical movement of a piston and an output shaft rotating by a rotational movement from the crankshaft, the crankshaft and the driven output shaft output shaft. When the output shaft rotates at a substantially constant speed, the crankshaft is provided with an inconstant speed power transmission mechanism in which the rotation speed changes periodically in synchronization with the rotation period, and the inequalities The fast power transmission mechanism is characterized in that the rotational speed of the crankshaft is set to be the fastest between the combustion pressure peak time and the combustion end time.

  According to the present invention, when the output shaft rotates at a substantially constant speed between the crankshaft and the output shaft, the constant speed power transmission in which the rotation speed of the crankshaft periodically changes in synchronization with the rotation cycle thereof. Since this mechanism is installed so that the inconstant speed power transmission mechanism is set so that the rotation speed of the crankshaft becomes the fastest between the combustion pressure peak time and the combustion end time, the piston acceleration speed and the actual speed The rising characteristic of the combustion pressure can be matched more precisely, and fuel consumption can be improved and vibration can be reduced.

Schematic configuration diagram of a gear insertion internal combustion engine when the piston according to the first embodiment is at the compression top dead center Schematic configuration diagram of a gear insertion type internal combustion engine when the piston is at a position showing the fastest descending speed in the combustion stroke (A) is a characteristic diagram showing changes in combustion pressure, (b) is a characteristic diagram showing changes in piston speed, and (c) is a characteristic diagram showing changes in rotational speed of the crankshaft. The characteristic chart showing the relationship between the optimal acceleration timing of the piston and the engine speed Schematic configuration diagram of a gear insertion internal combustion engine equivalent to FIG. 1 according to a second embodiment FIG. 2 is a schematic configuration diagram of a gear insertion type internal combustion engine equivalent to FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
Reference numeral 1 in FIG. 1 denotes a gear insertion type internal combustion engine (hereinafter abbreviated as “internal combustion engine”), and a spark ignition type gasoline combustion engine is shown in the figure. The internal combustion engine 1 shown in the present embodiment is a four-cycle single-cylinder internal combustion engine, but can be applied to a four-cycle or two-cycle two-cylinder or four-cylinder internal combustion engine.

  A piston 3 is inserted into a cylinder 2 of the internal combustion engine 1 so as to be able to advance and retreat, and a piston pin 3 a of the piston 3 and a crank pin 4 a of the crankshaft 4 are connected via a connecting rod (hereinafter abbreviated as “connecting rod”) 5. Are connected.

  The crankshaft 4 is rotatably supported by a crankcase (not shown) whose crank journal 4 b is connected to the cylinder 2. A combustion chamber 7 is formed in a region defined by the top surface of the piston 3 and the cylinder 2 and the cylinder head 6, and an ignition plug (not shown) that faces the ignition portion of the cylinder head 6 to the combustion chamber 7. ) Is fixed.

  Further, the output shaft 11 is disposed in parallel with the crankshaft 4 along the extending direction of the crankshaft 4. Further, a line connecting the axis of the crank journal 4b and the axis of the output shaft 11 is a line connecting the axis of the crank journal 4b and the axis of the crank pin 4a when the piston 3 is at the top dead center. Are arranged in an orthogonal direction. Load elements such as a generator and a traveling load are applied to the output shaft 11 via a transmission (not shown) or directly. A flywheel (not shown) is attached to the output shaft 11 so as to rotate the output shaft 11 at a substantially constant speed by inertia force.

  Further, a pair of crankshaft side non-circular gears and output shaft side noncircular gears that mesh with each other are interposed between the crankshaft 4 and the output shaft 11. These non-circular gears are elliptical gears 12 and 13, and the axial center portion of the crankshaft side elliptical gear 12 is attached to the crankshaft 4 and the axial center portion of the output shaft side elliptical gear 13 is attached to the output shaft 11. ing. The elliptical gears 12 and 13 constitute an inconstant speed power transmission mechanism. In this inconstant speed power transmission mechanism, when the output shaft 11 rotates at substantially constant speed, the rotation speed of the crankshaft 4 periodically changes in synchronization with the rotation period.

  Both the elliptical gears 12 and 13 have the same shape. The elliptical gears 12 and 13 are meshed with the major axes L1 and L2 and the minor axes S1 and S2 being shifted in phase in directions orthogonal to each other. In this embodiment, as the elliptical gears 12 and 13, a double-leaf gear having a point-symmetrical gear profile with respect to the shaft center is adopted, and the maximum angular velocity ratio of the elliptical gears 12 and 13 is set to 2.0. ing. However, this maximum angular velocity ratio is appropriately set according to the piston velocity change characteristic of the internal combustion engine 1 to be employed.

  When the piston 3 is guided by the cylinder 2 and moves up and down, the crankshaft 4 is rotated, and the rotation of the crankshaft 4 causes the output shaft through the crankshaft side elliptical gear 12 and the output shaft side elliptical gear 13 to mesh with each other. 11 rotates. At this time, when the output shaft 11 is rotated at a constant speed, the crankshaft 4 rotates at an inconstant speed by the rotation of the pair of elliptical gears 12 and 13 meshing with each other.

  FIG. 1 shows a state in which the piston 3 is at the compression top dead center (TDC). Further, as indicated by an arrow in the figure, the crankshaft 4 is set to rotate in the clockwise direction, and thus the output shaft 11 rotates in the counterclockwise direction. In this case, the crankpin 4a has a crank angle (phase) that is delayed by a set angle (set delay angle) θr with respect to the crank angle at which the crankshaft 4 is fastest with the output shaft 11 rotated at a constant speed. It is set (see FIG. 2). Here, the retard angle refers to a crank angle after the piston 3 passes the top dead center when the top dead center of the piston 3 is used as a reference.

  As shown in FIG. 2, the crank angle at which the rotational speed of the crankshaft 4 is the highest when the output shaft 11 is rotated at a constant speed connects the shaft center of the crank journal 4 b and the output shaft 11. This is a position where the short axis S1 of the crankshaft side elliptical gear 12 and the long axis L2 of the output shaft side elliptical gear 13 are superimposed on the line.

  As shown in FIG. 3 (a), for example, in the case of optimal ignition timing (MBT) control, when the ignition mixture is ignited at a predetermined timing with respect to the compressed air-fuel mixture in the combustion chamber 7 by spark ignition of the spark plug. The air-fuel mixture starts to combust with a certain delay, and the combustion pressure (cylinder pressure) rises rapidly. In general, in the MBT control, the ignition timing is controlled so that the combustion pressure peak crank angle θp, which is the combustion pressure peak timing, is about 10-15 [deg] at ATDC (after compression top dead center). This is a period in which the generation of thermal energy due to combustion continues, and refers to the period from the combustion start θs to the combustion end crank angle θe (in this embodiment, the combustion period is represented by the crank angle width). θs is about BTDC (before compression top dead center) about 18 to 12 [deg], and the combustion end crank angle θe, which is the combustion end timing, is about ATDC about 30 to 35 [deg]. When the combustion pressure peak crank angle θp is approximately in the middle of the combustion period, the combustion pressure peak crank angle θp is about 9-10 ATDC.

  Further, as shown in FIG. 3B, the rate of increase (acceleration) of the piston speed (crankshaft speed) from the combustion start crank angle θs to the combustion end crank angle θe is maximized. A set delay angle that is a phase of the crankshaft side elliptical gear 12 (crank angle width between the long axis L1 passing through the axis of the crank journal 4b and the axis of the crankpin 4a) in accordance with the rate of increase of the piston speed. By setting θr, higher thermal efficiency can be obtained.

  In the present embodiment, as shown in FIG. 3, the crankshaft is set so that the rate of increase (acceleration) of the crankshaft speed (piston speed) is maximized between the combustion pressure peak crank angle θp and the combustion end crank angle θe. The phase of the side elliptical gear 12 is set. That is, as shown in FIG. 2, in the region where the rate of increase in the piston speed (crankshaft speed) is maximum, the short axis S1 of the crankshaft side elliptical gear 12 and the long axis L2 of the output shaft side elliptical gear 13 are It is set so as to be positioned on a line connecting the axis of the crank journal 4b and the axis of the output shaft 11. In other words, the set retard angle θr is disposed at a position where the rotational speed of the crankshaft 4 is the fastest between the combustion pressure peak crank angle θp and the combustion end crank angle θe, and the descending speed of the piston 3 (crankshaft 4) is increased at an optimal timing.

  By the way, the combustion time is substantially constant regardless of the engine speed [rpm], and when the engine speed increases, the crank angle width required for the combustion period becomes relatively long. Therefore, as shown in FIG. 4, when the set delay angle θr of the crankshaft side elliptical gear 12 is adapted to the optimum acceleration timing of the piston 3, it is assumed that the combustion pressure peak crank angle θp is always constant. However, the optimal acceleration timing is gradually moved in the retarding direction as the engine speed increases.

  Therefore, when the normal operation region of the internal combustion engine 1 is approximately 2000 to 6000 [rpm], the optimum acceleration timing, that is, the set delay angle θr of the crankshaft-side elliptical gear 12 is the descending speed of the piston 3 during the combustion period. Is set to 20 to 35 [deg], more preferably, ATDC is set to 25 to 30 [deg].

  As a result, as shown in FIG. 3 (c), when the output shaft 11 is rotated at a constant speed, the rotational speed of the crankshaft 4 is caused by the gear profile of the elliptical gears 12 and 13 meshing with each other, and the piston speed during the combustion period. The change characteristic is almost in line with the increase in (crankshaft speed), and the highest thermal efficiency can be obtained.

  Next, the operation of the present embodiment having such a configuration will be described. In the internal combustion engine 1 in operation, the crankshaft 4 rotates as the piston 3 moves up and down, and the rotational force of the internal combustion engine 1 is output to the output shaft 11 via the crankshaft side elliptical gear 12 that is attached to the crankshaft 4. The output shaft 11 is rotated by being transmitted to the output shaft side elliptical gear 13 that is attached to the shaft. A load from a load element such as a traveling load or a generator is applied to the output shaft 11 via a transmission or the like.

  An air-fuel mixture is supplied to the combustion chamber 7 every intake stroke, and when an ignition timing in the latter half of the compression stroke is reached, a spark plug (not shown) is ignited, and the air-fuel mixture in the combustion chamber 7 is ignited. Then, as shown in FIG. 3A, the combustion pressure in the combustion chamber 7 rises rapidly in the combustion stroke, and the descending speed of the piston 3 is increased by the combustion pressure, and this piston 3 is connected to the piston 3 via the connecting rod 5. As a result, the rotational speed of the crankshaft 4 continuously provided is increased (see FIG. 3B).

  As shown in FIGS. 1 and 2, the crankshaft side elliptical gear 12 mounted on the crankshaft 4 has a long axis L <b> 1 of the crankshaft side elliptical gear 12 when the piston 3 is at the top dead center (TDC). Is set at a position delayed by a set delay angle θr with respect to an axis line (LTDC) connecting the axis of the crank journal 4b of the crankshaft 4 and the axis of the crankpin 4a. As shown in FIG. 3C, when the set delay angle θr is between the combustion pressure peak crank angle θp and the combustion end crank angle θe, the descending speed of the piston 3 (rotational speed of the crankshaft 4) is Since the speed is set to be the fastest, the rotational speed of the crankshaft 4 can be increased corresponding to the descending speed of the piston 3 during the combustion period.

  As a result, the high temperature time of the combustion gas is shortened, the cooling loss is reduced, the occurrence of knocking is suppressed, and further, the occurrence of knocking is suppressed, thereby realizing a relatively high compression ratio. Can do. Further, by reducing the cooling loss and suppressing the occurrence of knocking, it is possible to improve the thermal efficiency and the output, and to improve the fuel consumption.

  Further, when the output shaft 11 is rotated at a constant speed, the increase in the rotational speed of the crankshaft 4 has a change characteristic substantially along with the increase in the lowering speed of the piston 3 (rotational speed of the crankshaft 4) during the combustion period. Therefore, the acceleration of the piston 3 is 1 degree per stroke, and vibration and noise can be reduced.

[Second Embodiment]
5 and 6 show a second embodiment of the present invention. In the first embodiment described above, the line connecting the shaft centers of the output shafts 4b and 11 connects the shaft center of the crank journal 4b and the shaft pin 4a of the crank pin when the piston 3 is at the top dead center. In this embodiment, when the piston 3 is at the top dead center, the line connecting the axis of the crank journal 4b and the axis of the output shaft 11 and the crank journal 4b are arranged. The crankshaft 4 and the output shaft 11 are arranged so that the line connecting the shaft center and the shaft center of the crankpin 4a is in a straight line.

  The elliptical gears 12 and 13 and the meshing relationship between the elliptical gears 12 and 13 are the same as in the first embodiment, and therefore the rotational speed of the crankshaft 4 when the output shaft 11 is rotated at a constant speed. The change characteristics are the same as in FIG.

  As shown in FIG. 6, in this embodiment, the crank angle at which the crankshaft 4 becomes the fastest when the output shaft 11 is rotated at a constant speed is the axis between the axis of the crank journal 4 b and the output shaft 11. A short axis S1 of the crankshaft side elliptical gear 12 and a long axis of the output shaft side elliptical gear 13 on a line connecting the cores, that is, on an axis LTDC connecting the axis of the output shaft 11 and the axis of the piston pin 3a. This is the position where L2 is superimposed.

  At the fastest crank angle, the sandwich angle between the axis LTDC and the line connecting the axis of the crank journal 4b and the axis of the crank pin 4a is the set delay angle θr. In other words, as shown in FIG. 5, the short axis S1 of the crankshaft side elliptical gear 12 when the piston 3 is at the compression top dead center is set to a position advanced by the set crank angle θr. Thus, when the short axis S1 is used as a reference, the axis of the crank pin 4a is disposed at a position delayed by the crank angle θr.

  The combustion pressure peak crank angle θp is approximately in the middle of this combustion period, and is ATDC 10 to 15 [deg]. The set retard angle θr is set at a position along the increase in the descending speed of the piston 3 (rotational speed of the crankshaft 4) from the combustion pressure peak crank angle θp to the combustion end crank angle θe.

  As shown in FIG. 6, the set delay angle θr is approximately equal to the combustion end crank angle θe from approximately the middle of the combustion periods θs to θe (see FIG. 3) when the short axis S1 of the crankshaft side elliptical gear 12 is used as a reference. Specifically, it is set to ATDC 20 to 35 [deg], and more preferably, ATDC 25 to 30 [deg].

  In addition, this invention is not restricted to embodiment mentioned above, For example, the internal combustion engine to apply may be a diesel combustion engine.

1 ... an internal combustion engine,
3 ... Piston,
4 ... crankshaft,
4a ... crankpin,
4b ... Crank journal,
7 ... Combustion chamber,
11 ... Output shaft,
12 ... Crankshaft side elliptical gear,
13 ... Output shaft side elliptical gear,
θe: crank angle at which combustion ends,
θp: combustion pressure peak crank angle,
θr: set angle,
θs: Combustion start crank angle,
L1, L2 ... long axis,
S1, S2 ... Short axis

JP 2005-291103 A

Claims (7)

In an internal combustion engine comprising a crankshaft rotating by a vertical movement of a piston and an output shaft rotating by a rotational movement from the crankshaft,
When the output shaft rotates at a substantially constant speed between the crankshaft and the driven-side output shaft output shaft, the crankshaft rotates at a nonuniform speed whose rotation speed periodically changes in synchronization with the rotation cycle. With a power transmission mechanism,
The internal combustion engine characterized in that the inconstant speed power transmission mechanism is set so that the rotational speed of the crankshaft becomes the fastest between the combustion pressure peak time and the combustion end time. The inconstant speed power transmission mechanism comprises a crankshaft side non-circular gear and an output shaft side noncircular gear that mesh with each other,
2. The internal combustion engine according to claim 1, wherein each of the non-circular gears is provided on the crankshaft and the output shaft that are arranged in parallel to each other. The internal combustion engine according to claim 2, wherein each non-circular gear has a point-symmetrical gear profile with respect to the center of each non-circular gear. The output shaft is provided with a flywheel,
Between the combustion pressure peak time and the combustion end time in the combustion stroke, the short shaft side of the non-circular gear on the crankshaft side meshes with the long shaft side of the noncircular gear on the output shaft side, and the rotational speed of the crankshaft The internal combustion engine according to claim 2, wherein the engine is disposed so as to be fastest. The internal combustion engine is a spark ignition type gasoline combustion engine, and the crankshaft side non-circular gear has a shortest rotation speed in the range from the combustion pressure peak time to the combustion end time in the combustion stroke. And the long axis side of the non-circular gear on the output shaft side is 20 to 35 ° in the retarding direction with reference to the crank angle when the piston is at the compression top dead center. The internal combustion engine according to claim 4, characterized in that: The crankshaft and the output shaft include an axis of the crankshaft, an axis of the output shaft, and an axis of a crankpin provided on the crankshaft when the piston is at a compression top dead center. It is arranged on the axis line connected with a straight line,
When the short shaft side of the non-circular gear on the crankshaft side is engaged with the long shaft side of the noncircular gear on the output shaft side, the crankpin is compressed against the short shaft of the noncircular gear on the crankshaft side. 3. The internal combustion engine according to claim 2, wherein the crankshaft is disposed at a position where the rotational speed of the crankshaft becomes the fastest between approximately the middle of the combustion period from the stroke to the combustion stroke and the combustion end timing. The internal combustion engine is a spark ignition gasoline combustion engine, and the short shaft side of the crankshaft side non-circular gear and the long shaft side of the output shaft side noncircular gear meshing with each other, where the rotation speed of the crankshaft is the fastest. The internal combustion engine according to claim 6, wherein the crank angle to be set is set to a position of 20 to 35 ° in the retard angle direction with reference to a crank angle when the piston is at the compression top dead center. .

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