JP2006112258A - Variable cycle type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve fuel economy by reducing a pump loss by increasing an opening quantity of a throttle valve in a combustion cycle of many side. <P>SOLUTION: This variable cycle type internal combustion engine has the throttle valve 41 for throttling an intake quantity in an intake pipe 8, and cycle changing mechanisms 28 and 29 capable of changing a combustion cycle. When the combustion cycle is changed to 8 cycles from 4 cycles by the cycle changing mechanisms, opening of the throttle valve is controlled so as to open larger than a case of 4-cycle operation, to thereby reduce the pump loss in an engine. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a variable cycle internal combustion engine capable of changing a combustion cycle in accordance with, for example, an engine operating state.

  As this type of conventional internal combustion engine capable of changing the cycle, for example, one described in Patent Document 1 below is known.

  In brief, in this variable cycle internal combustion engine, the opening / closing timing of the intake valve and the exhaust valve is selectively set to the timing for two strokes (cycle) or the timing for four strokes (cycle) according to the engine operating state. A switchable variable timing mechanism is provided to switch to 2-stroke operation in a high load range of the engine and to 4-stroke operation in a low / medium load range, which is a practical operation range.

As a result, good engine operation can be ensured regardless of the engine operation state.
Japanese Utility Model Publication No. 64-51737

  By the way, in the conventional variable cycle type internal combustion engine, as described above, it is possible to selectively switch between two cycles and four cycles according to the engine operating state, but even if this switching is performed, the throttle valve is not opened. There is no change in measure.

  For this reason, even if the operation is switched to the 4-cycle operation in the practical operation region, the magnitude of the negative pressure in the intake pipe of the engine does not change, and the pumping loss (pump loss) may be changed to an internal combustion engine that cannot change the cycle. Absent. Therefore, it is not possible to reduce the fuel consumption in the low and medium load range of the engine.

  The present invention has been devised in view of the actual situation of each of the conventional techniques, and the invention according to claim 1 is particularly effective when the combustion cycle is changed when the combustion cycle is changed by the cycle changing mechanism. The throttle valve is controlled to be greatly opened as compared with the case where there is little.

  According to the present invention, for example, when the combustion cycle is changed to a larger one in accordance with a change in the engine operating state, the throttle valve is controlled to be opened largely, so that the combustion energy during the explosion stroke is increased. In addition, even if the combustion cycle increases, the pumping loss of the engine is reduced and the pump loss can be reduced. As a result, fuel consumption can be improved.

  The invention according to claim 2 is characterized in that the cycle changing mechanism is configured to change the combustion cycle by switching a plurality of cams having different cam lifts.

  According to the present invention, since a plurality of cams having different cam lifts are simply switched, it is possible to use the structure of a conventional existing variable cycle internal combustion engine, and therefore, it is possible to suppress an increase in cost. it can.

  According to a third aspect of the present invention, the opening degree of the throttle valve is configured to be controlled by electricity, and the control gain of the throttle valve is changed when the cycle changing mechanism is changed to one having a larger combustion cycle. It is characterized by doing.

  Embodiments of a variable cycle internal combustion engine according to the present invention will be described below with reference to the drawings.

  First, as shown in FIG. 1, the internal combustion engine is an in-line type multi-cylinder engine, in which 1 is a cylinder block, 2 is a cylinder head, 3 is a combustion chamber, and 4 is formed in the cylinder block 1. Cylinder bores 5 and 5 are pistons that slide in the cylinder bore 4 and rotationally drive the crankshaft 7 via the connecting rods 6, and 8 is an intake air that communicates with the intake port 10 in the cylinder head 2 via each branch of the intake manifold 9. A pipe, 11 is an exhaust pipe through which an exhaust port 12 in the cylinder head 2 communicates, 13 is a spark plug attached to the cylinder head 2, and 14 and 15 open and close the open ends of the intake port 10 and the exhaust port 12. There are two intake valves and two exhaust valves per cylinder.

  An intake side camshaft 16 and an exhaust side camshaft 17 are arranged at the upper end of the cylinder head 2 in parallel with the engine longitudinal direction. These camshafts 16, 17 are drive sprockets for the crankshaft 7. 7a and an idle sprocket 18 and a drive chain 19 wound between the idle sprocket 18 and driven sprockets 20 and 21 provided at the ends of the camshafts 16 and 17. The rotation speed of the crankshaft 7 is set to a quarter of a rotation by the double reduction chain of the driven chain 22.

  As shown in FIGS. 1 to 3, the intake side camshaft 16 and the exhaust side camshaft 17 open the intake valve 14 and the exhaust valve 15 against the spring force of the valve springs 23 and 24, respectively. Two 4-cycle first drive cams 25, 26 and one 8-cycle second drive cam 27 arranged on the side of the first drive cams 25, 26 are provided, respectively. Intake-side and exhaust-side cycle changing mechanisms 28 and 29 for switching between the first drive cams 25 and 26 and the second drive cam 27 according to the operating state are provided, respectively.

  Hereinafter, for the sake of convenience, only the intake side will be described. The first drive cams 25 and 26 have cam crests (cam profiles) set to substantially the same size, and each of the first drive cams 25 and 26 has the same configuration as the second drive cam 27. Therefore, the valve lifts of the intake valves 14 and 14 and the exhaust valves 15 and 15 by the drive cams 25, 26 and 27 are for four cycles as shown in FIG. The first drive cams 25 and 26 have a large characteristic as shown by a solid line, whereas the second drive cam 7 for eight cycles has a characteristic smaller than that for four cycles as shown by a broken line.

  The cycle changing mechanism 28 includes a main rocker arm 30 that directly operates the intake valves 14 and 14, and is disposed on both sides of the main rocker arm 30, and is in slidable contact with the drive cams 25, 26, and 27. The second sub rocker arms 31 and 32 and a connection switching portion 33 for selectively connecting or disconnecting the first and second sub rocker arms 31 and 32 to the main rocker arm 30 are configured.

  The main rocker arm 30 has a base end portion 30a swingably supported by a rocker shaft 34, and the bottom surfaces of the bifurcated tip portions 30b and 30b abut against the stem ends of the valve stems of the two intake valves 14 and 14. ing. The rocker ratio of the main rocker arm 30 is set to be larger than that used in a normal internal combustion engine.

  On the other hand, the first and second sub-rocker arms 31 and 32 have base end portions 31a and 32a supported independently by the same rocker shaft 34 so as to be freely swingable, and rollers 31b provided at the respective tip portions. The first and second drive cams 25, 26, and 27 are arranged to roll on 32b.

  As shown in FIGS. 4 and 5, the connection switching portion 33 is formed in a boss portion 30 c to 32 c formed at a lower portion of each rocker arm 30 to 32 and extends in the axial direction of the rocker shaft 34. The first to third connection holes 35a to 35c, the first to third connection pins 36a to 36c slidably accommodated in the respective connection holes 35a to 35c, and the first connection holes 35a. A hydraulic circuit 37 that connects the main rocker arm 30 and the first sub-rocker arm 31 by supplying hydraulic pressure into the rear end (pressure receiving chamber) and moving the connecting pins 36a to 36c in one direction, and the third connection A coil spring 38 that is elastically mounted in the hole 35c and moves the connecting pins 36a to 36c in the other direction to connect the main rocker arm 30 and the second sub rocker arm 32. To have.

  The hydraulic circuit 37 is formed in the direction of the inner axis of the rocker shaft 34, and includes an oil passage 39 into which lubricating oil is introduced from an unillustrated oil pump through a main oil gallery, and the radial direction of the rocker shaft 34 An oil hole 40 is formed in the boss portion 31c of the one sub rocker arm 31 so as to communicate with each other, and communicates between the oil passage 39 and the pressure receiving chamber of the first connecting hole 35a. And an electromagnetic switching valve (not shown) for switching between the drain passages.

  The electromagnetic switching valve is configured such that an internal spool valve switches the flow path by turning on and off a current output from an electronic controller (not shown).

  As shown in FIG. 1, a throttle valve 41 for restricting intake air flowing through the intake pipe 8 is provided inside the intake pipe 8. The throttle valve 41 has its opening amount adjusted according to the engine operating state via an electric control mechanism such as an electric motor (not shown), and the opening amount is more than that in the four-cycle operation region. The control region is controlled to be larger, and the control mechanism changes the control gain of the throttle valve 41 based on the control current output from the electronic controller. Yes.

  The electronic controller detects a current engine operating state based on various sensors such as a crank angle sensor, an air flow meter, a water temperature sensor, a fuel injection amount sensor, and the electromagnetic switching valve and the throttle valve according to the operating state. A control current is output to 41 control mechanisms.

  Hereinafter, the operation of the present embodiment having the above-described configuration will be described. First, the operation of the cycle changing mechanism 28 will be described. When the current from the electronic controller is turned off to the electromagnetic switching valve, the first connecting hole 35a is connected via the oil passage 39 and the oil hole 40. Hydraulic pressure is supplied into the pressure receiving chamber.

  Accordingly, as shown in FIG. 4, each of the connecting pins 36 a to 36 c slides in the maximum left direction as shown in the figure against the spring force of the coil spring 38, so that the first connecting pin 36 a is the first, The main rocker arm 30 and the first sub rocker arm 31 are connected to each other over the second connection holes 35a and 35b. At the same time, the contact surface of the second connecting pin 36b and the third connecting pin 36c is located between the second connecting hole 35b and the third connecting hole 35c, and the main rocker arm 30 and the second sub rocker arm 32 are connected. Is released.

  Accordingly, the intake valves 14 and 14 are opened and closed according to the cam profiles of the first drive cams 25 and 26, and the combustion cycle is switched to the four-cycle operation as shown in FIG. That is, the stroke until one combustion is performed in four cycles of a normal exhaust stroke-intake stroke-compression stroke- (ignition) -expansion (explosion) stroke, and each intake valve 14, 14 (each exhaust valve 15, The valve lift of 15) has a large characteristic (see the solid line in FIG. 6).

  Further, since the rocker ratio of the main rocker arm 30 is set to be larger than that used in a normal internal combustion engine, even if the maximum lift amount of the cam is small, the maximum valve lift amount according to that is the normal one. Can be as large as the maximum valve lift. Here, the cam maximum lift amount is small because the two first drive cams 25 and 26 are formed on one base circle at intervals of 180 °, so that the valve lift period is within a half circumference of 180 °. A valve rest period is required (for example, 60 ° in the former and 120 ° in the latter is 180 ° of a half circumference), and the valve lift period is as narrow as 60 °, which means that a large cam lift cannot be formed.

  On the other hand, when a current is supplied (turned on) from the electronic controller to the electromagnetic switching valve, the flow path is switched, the oil passage 39 is communicated with the drain passage, and the hydraulic pressure in the pressure receiving chamber of the first connection hole 35a is changed. It is discharged outside.

  Thereby, as shown in FIG. 5, each of the connecting pins 36 a to 36 c slides to the maximum right as shown in the figure by the spring force of the coil spring 38, and the third connecting pin 36 c becomes the third and second connecting pins. The main rocker arm 30 and the second sub rocker arm 32 are connected across the service holes 35a and 35b. At the same time, the contact surfaces of the first connecting pin 36a and the second connecting pin 36b are located between the first connecting hole 35a and the second connecting hole 35b, and the main rocker arm 30 and the first sub rocker arm 31 are connected. Is released.

  Accordingly, the intake valves 14 and 14 are opened and closed according to the cam profile of the second drive cam 27, and the combustion cycle is switched to the 8-cycle operation as shown in FIG. 7B. That is, the stroke until one combustion is ignited again (circular broken line) through an exhaust stroke, an intake stroke, a compression stroke, an (ignition), an expansion (explosion) stroke, a compression stroke, an expansion stroke, and a compression stroke again. However, at this point, no inhalation takes place, so no explosion occurs. Further, the expansion stroke, the exhaust stroke, the suction stroke, and the compression stroke are repeatedly performed, so that an eight-cycle operation is performed. That is, the operation is stopped (intermittent combustion) in the stroke after one stroke (combustion). In addition, the valve lifts of the intake valves 14 and 14 (exhaust valves 15 and 15) in this operation state have small characteristics. This is because the 8-cycle operation is performed in a lower load range than in the middle load range, and the intake air amount is also reduced. Therefore, since intake can be sufficiently performed even with a small valve lift, an effect of reducing the valve drive friction by reducing the valve lift can be obtained.

  During the 8-cycle operation, the throttle valve 41 is controlled to have a larger opening amount than in the 4-cycle operation as described above. Because, when switching from 4 cycles to 8 cycles, in order to prevent engine torque shocks and maintain the prescribed torque, the number of explosions has been reduced by half and the amount of intake air per cycle is almost doubled. Need to be increased. For this purpose, it is necessary to reduce the throttle by the throttle valve and increase the intake air amount.

  Next, control by the electronic controller will be described based on the flowchart of FIG.

  First, in step 1, the current engine speed signal N output from the crank angle sensor, the engine load signal Q output from the air flow meter, and the current engine water temperature signal T output from the water temperature sensor are read.

  Next, in Step 2, it is determined whether or not the current engine speed is about 800 rpm or more. If it is above, the process proceeds to Step 3, but if it is below, the process proceeds to Step 6.

  In step 6, as described above, the current to the electromagnetic switching valve is turned off and the process is switched to the 4-cycle operation.

  In step 3, it is determined whether the engine water temperature is, for example, 60 ° C. or higher. If the engine water temperature is below, the process proceeds to step 6;

  In this step 4, it is determined whether or not the engine load is equal to or less than a predetermined value. If it is determined that the vehicle is in the low-medium load region, which is a practical operation region, the process proceeds to step 5.

  In step 5, as described above, a process for switching to 8-cycle operation by energizing the electromagnetic switching valve is performed.

  As described above, according to this embodiment, for example, when the engine is switched to the 8-cycle operation in the low and medium load range, the opening degree of the throttle valve 41 is controlled to be large. It is possible to increase the combustion energy during the explosion stroke, and even if the combustion cycle increases, the pumping loss of the engine is reduced and the pump loss can be reduced. As a result, fuel consumption can be improved.

  In addition, since the valve lift is small in this operating range, the friction of the valve operating system can also be reduced.

  In addition, in this embodiment, the cycle changing mechanism 28 simply switches the first drive cams 25 and 26 and the second drive cams 27 having different cam lifts by the connection switching unit 33 according to the engine operating state. It becomes possible to use the structure of an existing internal combustion engine, and therefore it is possible to suppress an increase in cost.

  Further, as described above, in the 8-cycle operation region, the combustion is performed once every 8 cycles and the intermittent combustion is performed, so that the average effective pressure at the time of combustion is increased, so that the throttle of the throttle valve 41 is reduced. Pump loss is reduced.

  Further, in this 8-cycle operation, the same effect as that obtained when some cylinders are deactivated can be obtained. However, since the operation is intermittent in each cylinder, the balance of engine vibration is improved. For this reason, compared with the cylinder deactivation method, the 8-cycle operation region can be expanded to a low rotation region, and fuel efficiency is also improved. Further, in the 8-cycle operation region, the combustion gas is retained in the cylinder between the two compressions and the two expansions after the explosion and expansion, so that the combustion reaction proceeds sufficiently and the unburned gas of CO or HC The effect of reducing the components can be obtained.

  In addition, since the engine is operated in four cycles in the high load region, gas exchange efficiency is improved, and fuel consumption and exhaust gas can be improved even in a high output traveling region.

  Furthermore, since each camshaft 16 and 17 becomes a quarter rotation per one rotation of the crankshaft 7, sliding friction of each said drive cam 25-27, a cam journal part, etc. can be reduced. As a result, engine output and durability can be improved.

  As described above, since the combustion cycle can be changed according to the engine operating state, it can be used in an operating region where fuel efficiency is emphasized or output is emphasized, thereby obtaining the optimum operating state according to the engine demand. It is done.

  When the valve closing timing of the intake valves 14 and 14 is controlled to be earlier than the valve closing timing of the intake valves 14 and 14 during the four-cycle operation, as shown in FIG. ) Or slow (b), the pump loss can be reduced and the increase of the in-cylinder pressure during the 8-cycle operation can be suppressed, so that the friction loss of each part can be reduced.

  That is, in FIG. 10 showing the relationship between the cylinder pressure and the stroke volume, when the closing timing of the intake valves 14 and 14 is advanced during the 8-cycle operation, as shown in FIG. It is clear that the internal pressure is sufficiently smaller than that in the case of four-cycle operation. In addition, when the valve closing timing is delayed, it is clear that the in-cylinder pressure is reduced in this case as shown in FIG.

  Therefore, the friction loss of each part can be greatly reduced, and the fuel consumption can be improved.

  FIG. 11 shows a second embodiment of the present invention. The cam profile of the first drive cams 25 and 26 on the 4-cycle side in the exhaust-side cycle changing mechanism 29 is the same as that of the first embodiment, but 8 cycles. The second driving cam 27 on the side is further increased by one to two, and the increased cam crest of the increased second driving cam 27a is set to be smaller.

  Accordingly, as shown in FIG. 12B, the cycle characteristics during the 8-cycle operation are such that the valve lift in the intermittent combustion (pause) region X is sufficiently small and the intermittent combustion is shifted from the expansion stroke to the compression stroke. In-cylinder gas during the operation (arrow a) is partially released to the exhaust pipe 11 and decompressed. For this reason, the compression pressure in the next compression stroke decreases, and the friction of the sliding portion such as the piston 5 can be sufficiently reduced. As a result, the fuel consumption can be further improved.

  The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below.

  The variable cycle internal combustion engine according to claim 1, wherein the cycle changing mechanism switches the combustion cycle between 4 cycles and 8 cycles.

  The variable cycle internal combustion engine according to claim 1, wherein the cycle changing mechanism is configured to switch the plurality of cams according to an engine operating state.

  Since the combustion cycle can be changed according to the engine operating state, it can be used in an operating region where fuel efficiency is important or output is important, thereby obtaining an optimal operating state according to the demands of the engine.

  [Claim 3] The variable cycle internal combustion engine according to claim 2, wherein the cam having a different cam lift is different in the number of cam ridges for one rotation of the camshaft.

  (4) The camshaft provided with the plurality of cams is set to be ¼ rotation per crankshaft rotation, and the number of cam ridges for one rotation of the camshaft is set by a cycle changing mechanism. The variable cycle internal combustion engine according to claim 1, wherein the combustion cycle is changed by switching between one and two.

  (5) The cycle changing mechanism includes a plurality of rocker arms with which a plurality of cams having different cam lifts come into contact, and is configured to connect or release the rocker arms according to an engine operating state. The variable cycle internal combustion engine according to claim 2.

1 is a schematic view showing a variable cycle internal combustion engine according to a first embodiment of the present invention in a longitudinal section. It is sectional drawing of the cycle change mechanism with which this embodiment is provided. It is a top view which isolate | separates and shows the intake side camshaft and each rocker arm of the cycle change mechanism. It is sectional drawing which shows the effect | action of the connection switching part provided for this embodiment. It is sectional drawing which shows the effect | action of the connection switching part. It is a valve lift characteristic figure of the 4 cycle operation area in this embodiment, and an 8 cycle operation area. A is a characteristic diagram showing in-cylinder pressure characteristics in a 4-cycle operation region, and B is a characteristic diagram showing in-cylinder pressure characteristics in an 8-cycle operation region. It is a control flowchart figure of the electronic controller provided to this embodiment. It is a valve lift characteristic figure at the time of changing the closing timing of an intake valve at the time of 8 cycle operation. A shows the in-cylinder pressure characteristic when the closing timing of the intake valve during 8-cycle operation is advanced, and B is the in-cylinder pressure characteristic diagram when the closing timing of the intake valve is delayed. It is sectional drawing which shows the drive cam provided to 2nd Embodiment. A is a characteristic diagram showing the in-cylinder pressure in the 4-cycle operation region of the present embodiment, and B is a characteristic diagram showing the in-cylinder pressure in the 8-cycle operation region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylinder block 2 ... Cylinder head 3 ... Combustion chamber 7 ... Crankshaft 14 ... Intake valve 15 ... Exhaust valve 16,17 ... Intake side, exhaust side camshaft 25, 26 ... 1st drive cam 27 ... 2nd drive cam 28・ 29 ... Cycle change mechanism 41 ... Throttle valve

Claims (3)

A throttle valve that adjusts the amount of intake air supplied into the combustion chamber by a throttle;
A cycle change mechanism capable of changing the combustion cycle;
In a variable cycle internal combustion engine equipped with
A variable cycle internal combustion engine, wherein when the cycle change mechanism is changed to one having a larger number of combustion cycles, the throttle valve is controlled to be opened more widely than one having a smaller number of combustion cycles. The variable cycle internal combustion engine according to claim 1, wherein the cycle changing mechanism is configured to change the combustion cycle by switching a plurality of cams having different cam lifts. 3. The throttle valve opening amount is configured to be controlled by electricity, and the control gain of the throttle valve is changed when the cycle changing mechanism is changed to one having a larger combustion cycle. The variable cycle internal combustion engine described in 1.

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