JP2010249110A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize stable combustion by promoting the atomization of fuel injected in an intake stroke. <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. When a piston 3 is at a top dead center, a minor axis S1 of the crank shaft side elliptical gear 12 is arranged on a timing delay side at a phase angle θ2 of 60-85[deg] to an axial line between the axial centers of the crank shaft 4 and the output shaft 11 to set an injection starting timing for a fuel injection valve 15 at ATDC 64-84[deg]. The down-moving speed of the piston 3 is increased in the second half of the intake stroke, and so the flow rate of intake air to flow into a cylinder is increased to promote the atomization of fuel because of the injection starting timing set in synchronization with an increase of the flow rate of the intake air. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine that can promote atomization of fuel and stabilize combustion during intake stroke injection.

  In the intake stroke injection in which fuel is supplied into the cylinder during the intake stroke, the fuel is vaporized in the cylinder, and fresh air is cooled by the latent heat of vaporization at that time. High temperature can be suppressed. Furthermore, lean combustion is also possible by generating a strong gas flow such as a tumble flow or a swirl flow with respect to the intake air flowing into the cylinder.

  In general, intake stroke injection is often used in a direct injection internal combustion engine in which fuel is directly injected into the cylinder, but even in a port injection internal combustion engine in which a fuel injection valve is disposed in an intake port, Intake stroke injection can be realized by injecting fuel in synchronism with the opening of the valve.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2005-235580), when the intake air amount is small or the intake pipe negative pressure is low, the fuel injection valve disposed in the intake port is synchronized with the intake stroke. An intake stroke injection technique for supplying fuel into a cylinder is disclosed. According to the technique disclosed in this document, since the fuel injection timing is synchronized with the intake stroke, the fuel adhering to the wall surface is reduced and stable air-fuel ratio control can be performed.

  By the way, in a naturally aspirated internal combustion engine, fresh air is taken into the cylinder using negative pressure generated by the downward movement of the piston. Since the reciprocating linear motion of the piston is converted into rotational motion by the crankshaft, it is stopped at the top dead center and bottom dead center, accelerated after passing through this top dead center or bottom dead center, and further, bottom dead center Or it is decelerated when it comes close to top dead center.

  The flow rate of the intake air taken into the cylinder varies depending on the piston descending speed, and the flow rate becomes fastest at a position (crank angle) at which the piston descending speed becomes the fastest. The crank angle at which the piston descending speed is the fastest is about 80 [deg, ATDC], although there are some differences depending on the linkage ratio (ratio between the connecting rod length and the crank radius).

  On the other hand, since the intake stroke injection can be performed while the intake valve is open, the injection timing can be set in a relatively wide range from 0 to 150 [deg, ATDC}. it can.

  However, in order to generate an air-fuel mixture for combustion in the cylinder, the fuel needs to be vaporized before ignition, and the combustion becomes unstable if the fuel is not sufficiently vaporized. Therefore, it is necessary to end the fuel injection at a relatively early timing to ensure a period required for vaporization. However, if the fuel injection is ended early, a sufficient amount of fuel cannot be injected during the intake stroke. As disclosed in the above-mentioned documents, there is a disadvantage that an operation region in which intake stroke injection can be performed, such as a low load operation region, is limited.

  In view of the above circumstances, the present invention can perform the intake stroke injection without destabilizing the combustion, and suppresses fuel consumption improvement, charging efficiency improvement, and high temperature in the cylinder in a relatively wide operating range. An object of the present invention is to provide an internal combustion engine that can perform the above-described operation.

  In order to achieve the above object, the present invention provides a crankshaft side non-circular gear and an output shaft side noncircular gear that mesh with each other on a crankshaft that is rotated by a vertical movement of a piston and an output shaft that is parallel to the crankshaft. In addition, in an internal combustion engine in which a flywheel is provided on the output shaft and a fuel injection valve is provided in an intake port, when the piston is at top dead center, the short shaft side of the crankshaft-side non-circular gear is A phase angle of 60 to 85 degrees is arranged on the retard side with respect to an axis connecting the axis of the shaft and the axis of the output shaft, and the injection start timing of the fuel injection valve is after the intake top dead center It is set to 64 to 84 degrees.

  According to the present invention, when the piston is at the top dead center, the short shaft side of the crankshaft side non-circular gear is 60 to 85 degrees with respect to the axis line connecting the axis of the crankshaft and the axis of the output shaft. Since the fuel injection valve injection start timing is set to 64 to 84 degrees after the intake top dead center, the piston lowering speed is increased in the latter half of the intake stroke, The flow velocity of the intake air that flows in increases rapidly, and a strong shear flow is generated. As a result, the fuel injected into the cylinder is atomized by this air flow, vaporization is promoted, and stable combustion can be obtained. Furthermore, the phase angle of the short axis side of the crankshaft-side non-circular gear with respect to the axis connecting the axis of the crankshaft and the axis of the output shaft can be set in a relatively wide range of 60 to 85 degrees. By setting the phase angle in accordance with the normal operation region, it is possible to suppress fuel consumption improvement, charging efficiency, and high temperature in the cylinder in the operation region.

Schematic configuration diagram of gear insertion type internal combustion engine when piston is at intake top dead center Schematic configuration diagram of gear insertion type internal combustion engine when piston is at injection start timing Schematic configuration diagram of gear insertion type internal combustion engine when piston is in the fastest position Characteristic diagram showing the relationship between the crankshaft angle and piston speed when the output shaft is at a constant speed Characteristic diagram showing the relationship between the gear phase angle based on the intake top dead center, the maximum speed timing of the piston, and the increase rate of the peak flow velocity of the intake air (A) is a timing chart showing the fuel injection timing, (b) is a timing chart showing the operation of the intake valve, and (c) is a timing chart showing a change in rotational speed of the crankshaft side elliptical gear.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 3 is 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 drawings. 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 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 journal (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, the cylinder 2 and the cylinder head 6. The cylinder head 6 is provided with an intake port 6a and an exhaust port 6b, and an intake valve 8 and an exhaust valve 9 are provided at each of the ports 6a and 6b. Further, a fuel injection valve 15 is disposed in the intake port 6a, and the injection direction of the fuel injection valve 15 is set to the combustion chamber 7 side. Further, an ignition plug (not shown) is fixed to the top of the cylinder head 6 so that the ignition part faces the combustion chamber 7.

  As shown in FIG. 6B, the valve opening period of the intake valve 8 is set from just before the end of the exhaust stroke to immediately after the start of the compression stroke, and although not shown, the valve opening period of the exhaust valve is the combustion stroke. It is set from just before the end to immediately after the start of the intake stroke. The valves 8 and 9 are opened / closed by, for example, the operation of an intake cam and an exhaust cam provided on a camshaft that rotates at a half rotation speed in synchronization with the rotation speed of the crankshaft 4. However, the valves 8 and 9 may be electromagnetic valves whose opening and closing are electronically controlled.

  Further, the output shaft 11 is disposed in parallel with the crankshaft 4 along the extending direction of the crankshaft 4. Further, the line connecting the axis of the crank journal 4b and the axis of the output shaft 11 is the 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 (see FIG. 1). 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.

  Further, between the crank journal 4b and the output shaft 11, a pair of crankshaft-side non-circular gears and output shaft-side non-circular gears that are meshed with each other are mounted on the shaft. The two non-circular gears are elliptical gears 12 and 13 in this embodiment, and the shaft core portion of the crankshaft side elliptical gear 12 and the output shaft side elliptical gear 13 is connected to the shaft end portion of the crank journal 4b and the output shaft 11. Are respectively attached to the shaft. When the output shaft 11 rotates at a constant speed due to the meshing of the elliptical gears 12 and 13, the crankshaft 4 periodically rotates at a constant speed in synchronism with the rotation.

  The elliptical gears 12 and 13 have the same shape, and the elliptical gears 12 and 13 are meshed with the major axes L1 and L2 and the minor axes S1 and S2 shifted in phase in a direction perpendicular to each other. ing. 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 crank journal 4b rotates at an infinite speed with a period of 180 [deg] due to the rotation of the pair of oval gears 12 and 13 meshing with each other. In other words, when the raising / lowering speed of the piston 3 is periodically increased or decreased, the output shaft 11 rotates at a constant speed.

  FIG. 1 shows a state in which the piston 3 is at the intake top dead center (TDC). The symbol LTDC is an axis (top dead center axis) 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 TDC. Further, as indicated by an arrow in the figure, the crank journal 4b is set to rotate in the clockwise direction, and therefore the output shaft 11 rotates in the counterclockwise direction.

  With the output shaft 11 rotated at a constant speed, the crank angle at which the rotational speed of the crankshaft 4 is the fastest is as shown in FIG. 3 with respect to the line connecting the axes of the crank journal 4b and the output shaft 11. In this state, the short shaft S1 side of the crankshaft side elliptical gear 12 and the long shaft L2 side of the output shaft side elliptical gear 13 are meshed with each other. . Therefore, by synchronizing the position where the short shaft S1 side of the crankshaft side elliptical gear 12 and the long axis L2 side of the output shaft side elliptical gear 13 are meshed with the crank angle representing the position of the piston 3, the piston 3 can be the fastest at any position (crank angle) between the intake top dead center and the intake bottom dead center.

  For example, at the position where the rotational speed of the crankshaft 4 is the fastest as shown in FIG. 3, the short shaft S1 of the crankshaft side elliptical gear 12 is on the axis connecting the axis of the crank journal 4b and the axis of the output shaft 11. If the axis connecting the axis of the crank journal 4b and the axis of the crank pin 4a is deviated from the short axis S1 by the phase angle θ1 [deg] in the retarded direction, as shown in FIG. Is at the top dead center TDC, the short axis S1 is shifted to the advance side by the phase angle θ1 with respect to the top dead center axis LTDC. In other words, as shown in FIG. 1, the line connecting the axis of the crank journal 4b and the axis of the output shaft 11 is arranged in a direction orthogonal to the top dead center axis LTDC. When the axis connecting the axis of the crank journal 4b and the axis of the output shaft 11 is used as a reference, when (90−θ1) is θ2, the phase angle θ2 is shifted to the retard side. become.

  Similarly, the line connecting the axis of the crank journal 4b and the axis of the crank pin 4a has a shift of the phase angle θ1 with respect to the short axis S1, so that the rotational speed of the crankshaft 4 is as shown in FIG. When the crankshaft side elliptical gear 12 is at the fastest position, the axis connecting the axis of the crank journal 4b and the axis of the crankpin 4a is at the position 90 + θ1 [deg] after intake top dead center (ATDC). It will be. In the following, this crank angle ATDC90 + θ1 is defined as the fastest crank angle θ3. For example, when the fastest crank angle θ3 is set to ATDC 40 [deg], the phase angle θ1 is 90 + (− θ3) = 50 [deg], and the phase angle θ2 is 90 − (− 50) = 140 [ deg]. The signs of the fastest crank angles θ1 to θ3 are plus (+) when the crank angles θ1 to θ3 are on the advance side with respect to the reference axis, and are minus (−) when the crank angle is on the retard side. It is represented by

  FIG. 4 shows the speed change of the piston 3 when the relative position between the crankshaft side elliptical gear 12 and the crank journal 4b on which the crankshaft side elliptical gear 12 is mounted is changed and the output shaft 11 is rotated at a constant speed in this state. It is shown. In the drawing, with respect to the intake top dead center (TDC), the advance direction is represented by plus (+) and the retard direction is represented by minus (−).

  According to experiments, it has been found that the crank angle θ3 (see FIG. 3) at which the piston 3 exhibits the fastest descending speed in the intake stroke is approximately in the range of 40 ≦ θ3 ≦ 130 [deg. ATDC]. Therefore, if the crank angle θ3 that is the fastest is set within this range, the speed of the piston 3 can be made the fastest at any crank angle within the range. In the figure, the characteristic indicated by the bold line is set to θ3 = ATDC 40 [deg], the characteristic indicated by the thin line is set to θ3 = ATDC 130 [deg], and the characteristic indicated by the alternate long and short dash line is set to θ3 = ATDC 90 [deg]. In this case, when the fastest crank angle θ3 is set to 0 ≦ θ3 <40 [deg. ATDC], or 130 <θ3 ≦ 180 [deg. ATDC], these crank angles are such that the piston 3 is above the top dead center or Since the piston 3 is decelerated at the position at or near the bottom dead center, the highest speed cannot be achieved. As can be seen from the figure, the fastest peak speed of the piston 3 can be obtained by setting the fastest crank angle θ3 in the vicinity of ATDC 90 [deg]. Therefore, if the intake stroke injection is performed at this timing, vaporization can be promoted by atomization of the fuel injected from the fuel injection valve. However, in order to ensure a free fuel injection period, it is preferable to set the fastest crank angle θ3 in the latter half of the intake stroke. A technique for setting the crank angle when the piston 3 is at the top dead center to the fastest crank angle θ3 is disclosed in Japanese Patent Laid-Open No. 2005-291103 filed earlier by the present applicant.

  Also, FIG. 5 shows that the intake air flow rate increase rate when the output shaft 11 is rotated at a constant speed in the same manner as in FIG. 4 in which the phase angle θ2 is changed to the advance side and the retard side, respectively. The peak value of (intake air flow rate change rate per unit time) and the optimal injection timing are shown. In addition, the vertical axis of the optimal injection timing indicates the crank angle of the crankshaft 4 when the intake flow rate increase rate has a peak value.

  First, the peak flow velocity increase rate is the highest flow velocity increase in the intake stroke when the phase angle θ2 of the crankshaft side elliptical gear 12 is shifted from 60 to 85 [deg] to the retard side (clockwise direction in FIG. 1). The rate (1.4 times the conventional) is detected. When this is converted based on the intake top dead center (TDC), ATDC is 95 to 120 [deg] (see FIG. 4). Therefore, by setting the fastest crank angle θ3 in the range of ATDC 95 to 120 [deg], atomization of fuel in the intake stroke injection can be promoted. Further, it is understood that the optimum injection start timing θINJ indicating the valve opening timing of the fuel injection valve 15 in the intake stroke injection at that time is ATDC 64 to 84 [deg] based on the intake top dead center (TDC). The fuel injection control such as the injection timing of the fuel injected from the fuel injection valve 15 and the fuel injection amount (injection period) is performed by an electronic control device (not shown). In this electronic control unit, the injection timing is measured based on the crank angle detected by the crank angle sensor, and when the predetermined timing is reached, an injection start signal is output to the fuel injection valve 15 to start fuel injection. Then, the fuel injection period corresponding to the fuel injection amount set based on the engine operating state is counted, and the fuel injection is stopped when the fuel injection period ends.

  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 with the vertical movement of the piston 3, and the rotational force is transmitted via the crankshaft side elliptical gear 12 that is attached to the crank journal 4 b of the crankshaft 4. The output shaft 11 is rotated by being transmitted to the output shaft side elliptical gear 13 attached to the output shaft 11. 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.

  When the piston 3 reaches the end of the exhaust stroke, the intake valve 8 opens, and when the piston 3 moves down to the intake stroke and the piston 3 descends, the intake air flows into the cylinder from the intake port 6a. As shown in FIG. 6C, in the present embodiment, the fastest crank angle θ3 is set between the ATDCs 95 to 120 in the latter half of the intake stroke, and therefore the crankshaft side ellipse that is pivotally attached to the crank journal 4b. The meshing position of the gear 12 with respect to the output shaft side elliptical gear 13 is in the process of shifting from the minor axis S1 side to the major axis L1 side. Therefore, the rotational speed of the crankshaft side elliptical gear 12 (crankshaft 4) gradually decreases, and after the major axis L1 of the crankshaft side elliptical gear 12 meshes with the minor axis S2 of the output side elliptical gear 13, the crankshaft 4 Is gradually increased (the descending speed of the piston 3). As shown in FIG. 3, when the crankpin 4a reaches a preset crank angle θ3 (ATDC 95 to 120 [deg]), the short shaft S1 side of the crankshaft side elliptical gear 12 is connected to the output shaft side elliptical. The gear 13 meshes with the long axis L2 side, and the rotational speed of the crankshaft 4 (the descending speed of the piston 3) becomes the fastest.

  On the other hand, the injection start timing θINJ of the fuel injected from the fuel injection valve 15 is set in accordance with the timing at which the rotational speed of the crankshaft 4 (the descending speed of the piston 3) becomes the fastest, and FIGS. As shown in (a), fuel injection is started when a preset injection start timing θINJ is reached.

  As described above, the descending speed of the piston 3 is set so as to be the fastest at the predetermined crank angle θ3 in the latter half of the intake stroke. Therefore, the descending speed of the piston 3 is reached from the middle of the intake stroke until the fastest crank angle θ3 is reached. Is increased, and the rate of increase in the flow rate of the intake air is 1.4 times higher than that in the prior art near the maximum crank angle θ3. As a result, the flow velocity of the intake air flowing into the cylinder (combustion chamber 7) together with the fuel injected from the fuel injection valve 15 is rapidly increased, and a strong shear flow is generated in the cylinder (combustion chamber 7) and turbulent flow is generated. Will occur. Then, the fuel that has flowed into the cylinder is atomized by the shearing flow to promote vaporization, and is further homogeneously mixed by the intake turbulent flow.

  As a result, even in the intake stroke injection for which it is difficult to ensure a sufficient fuel vaporization period, vaporization is promoted by fuel atomization at an intake flow velocity that is 1.4 times the conventional speed, and efficient in a short time. By homogeneous mixing, stable combustion can be obtained.

  As described above, in the present embodiment, the moving speed of the piston 3 is varied. In particular, in the intake stroke, the descending speed of the piston 3 is gradually increased from the first half of the intake stroke to the second half of the intake stroke. Since the flow velocity of the intake air flowing into 7) is rapidly increased, vaporization due to atomization of fuel in the intake stroke injection is promoted, and stable combustion can be obtained by homogeneous mixing.

  In the present embodiment, since the descending speed of the piston 3 is realized by using a pair of oval gears meshing with each other, the crank angle θ3 at which the rotational speed of the crankshaft 4 (the descending speed of the piston 3) is the fastest is set. , 60 to 85 [deg] and a relatively wide crank angle range. As a result, the optimum crank angle θ3 can be set according to the normal operation region of the internal combustion engine 1 to be adopted or the load applied to the internal combustion engine 1, etc., and the degree of freedom of design is increased, and the fuel consumption is improved in a wide operation region. Improvement of filling efficiency and high temperature inside the cylinder can be suppressed. Conversely, the fastest crank angle θ3 can be easily set in accordance with the optimal injection start timing.

  The present invention is not limited to the above-described embodiment. For example, the fuel injection valve is not limited to the port injection type fuel injection valve 15 but may be a direct injection type fuel injection valve.

1 ... an internal combustion engine,
3 ... Piston,
3a ... Piston pin,
4 ... crankshaft,
4a ... crankpin,
4b ... Crank journal,
6a ... intake port,
8 ... Intake valve,
11 ... Output shaft,
12 ... Crankshaft side elliptical gear,
13 ... Output shaft side elliptical gear,
15 ... Fuel injection valve,
θINJ: Injection start timing,
θ1, θ2 ... phase angle,
θ3: fastest crank angle,
LTDC ... Top dead center axis,
L1, L2 ... long axis,
S1, S2 ... Short axis,
TDC ... Top dead center

JP 2005-235580 A

Claims (1)

A crankshaft rotating on the vertical movement of the piston and an output shaft parallel to the crankshaft are provided with a non-circular gear on the crankshaft side and a noncircular gear on the output shaft side, and a flywheel is mounted on the output shaft. In an internal combustion engine provided with a fuel injection valve in the intake port,
When the piston is at top dead center, the short shaft side of the crankshaft-side non-circular gear has a phase angle of 60 to 85 degrees with respect to an axis line connecting the axis of the crankshaft and the axis of the output shaft. Are arranged on the retard side,
An internal combustion engine, wherein an injection start timing of the fuel injection valve is set to 64 to 84 degrees after intake top dead center.

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