JP2010196578A - Start control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve startability of an internal combustion engine including a variable compression ratio mechanism. <P>SOLUTION: This start control device for the internal combustion engine 100 includes the variable compression ratio mechanism 6 capable of varying compression ratio and a fuel supply device 5 capable of optionally selecting and supplying a plurality of kinds of fuel having different evaporation characteristics. The device includes start fuel selecting means (S5, S6, S8) selecting start fuel supplied in start out of the plurality of kinds of fuel, and a compression ratio change means (S7, S9) setting compression ratio lower as evaporation characteristics of the start fuel are better. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a start control device for an internal combustion engine.

  As a conventional internal combustion engine, a first link that is connected to a piston that reciprocates in a cylinder via a piston pin, and is pivotally connected to the first link and rotatably mounted on a crankpin of a crankshaft. The second link, a third link with one end pivotably connected to the second link, and a cylinder block rotatably provided and pivotally supporting the other end of the third link There is a control shaft having an eccentric cam portion and an actuator for controlling the rotational position of the control shaft, and having a compression ratio variable mechanism that changes the compression ratio according to the rotational position of the control shaft ( For example, see Patent Document 1).

JP 2004-239174 A

  In the case of an internal combustion engine equipped with a variable compression ratio mechanism, it is desirable to improve the startability by reducing the starting torque by relatively reducing the compression ratio at the time of starting. However, the above-described conventional internal combustion engine supplies liquid fuel. For this reason, if the compression ratio is too low, the amount of heat necessary for vaporizing the fuel is insufficient, and the startability is adversely affected. For this reason, the compression ratio can be lowered only within a range in which the amount of heat necessary for vaporizing the fuel can be obtained.

  The present invention has been made paying attention to such a conventional problem, and an object thereof is to improve the startability of an internal combustion engine having a compression ratio variable mechanism by reducing the amount of heat for vaporizing the fuel. And

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention includes an internal combustion engine (100) including a compression ratio variable mechanism (6) capable of changing a compression ratio and a fuel supply device (5) capable of arbitrarily selecting and supplying a plurality of fuels having different vaporization characteristics. The starter control device of the starter fuel selection means (S5, S6, S8) for selecting the starter fuel to be supplied from the plurality of fuels at the time of start-up, and the better the vaporization characteristics of the starter fuel, the more the compression Compression ratio changing means (S7, S9) for lowering the ratio.

  An internal combustion engine start control device comprising: a compression ratio variable mechanism (6) capable of changing a compression ratio; and a fuel supply device (5) that arbitrarily supplies and supplies either gas fuel or liquid fuel. The starting fuel selection means (S5, S6, S8) for selecting whether the starting fuel to be supplied at the time of starting is the gas fuel or the liquid fuel, and compression when the gas fuel is supplied Compression ratio changing means (S7, S9) for making the ratio lower than the compression ratio when the liquid fuel is supplied.

  According to the present invention, a plurality of fuels having different vaporization characteristics can be supplied, and the compression ratio is changed according to the vaporization characteristics of the selected starting fuel. As a result, while ensuring the amount of heat for vaporizing the fuel, the compression ratio can be relatively lowered when starting with fuel having good vaporization characteristics, so that the startability can be improved.

  Further, when supplying gas fuel, the amount of heat for vaporizing the fuel is unnecessary, so that the compression ratio at the time of starting can be further reduced, and the startability can be further improved.

It is the schematic which shows the system configuration | structure of an engine. It is a figure explaining the compression ratio change method by a compression ratio variable mechanism. It is a flowchart explaining start control. It is a time chart explaining operation | movement of start control.

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

  FIG. 1 is a schematic diagram showing a system configuration of an engine 100 according to an embodiment of the present invention.

  The engine 100 includes a cylinder block 1, a cylinder head 2, an intake passage 3, an exhaust passage 4, a fuel supply device 5, a compression ratio variable mechanism 6, and a controller 7.

  A plurality of cylinders 11 are formed in the cylinder block 1. A piston 12 that receives combustion pressure and reciprocates inside the cylinder 11 is housed inside the cylinder 11. The cylinder block 1, the cylinder head 2, and the piston 12 define a pent roof type combustion chamber 13.

  The cylinder head 2 is formed with an intake port 21 connected to the intake passage 3 and opening in the top wall of the combustion chamber 13, and an exhaust port 22 connected to the exhaust passage 4 and opening in the top wall of the combustion chamber 13. The cylinder head 2 is provided with an intake valve 23 that opens and closes an opening between the combustion chamber 13 and the intake port 21 and an exhaust valve 24 that opens and closes an opening between the combustion chamber 13 and the exhaust port 22. Further, the cylinder head 2 is provided with a spark plug 25 so as to face the center of the top wall of the combustion chamber 13.

  The intake passage 3 is a passage through which air sucked into the cylinder flows, and is connected to the intake port 21.

  The exhaust passage 4 is a passage through which the exhaust discharged from the cylinder flows, and is connected to the exhaust port 22.

  The fuel supply device 5 includes a liquid fuel tank 51, a liquid fuel injection valve 52, a reformer 53, a gas fuel pump 54, a gas fuel tank 55, and a gas fuel injection valve 56.

  The liquid fuel tank 51 stores liquid fuel supplied from the outside. In this embodiment, gasoline is used as the liquid fuel.

  The liquid fuel injection valve 52 is provided in the cylinder head 2 and injects the liquid fuel sent from the liquid fuel tank 51 into the intake port 21.

  The reformer 53 includes a monolith carrier 531 and a reforming liquid fuel injection valve 532.

  The monolithic carrier 531 is an integrated structure in which a honeycomb cordurolite having a reforming catalyst such as platinum supported on the surface is housed in an annular case formed so as to surround the outer periphery of the exhaust passage 4. It is.

  The reforming liquid fuel injection valve 532 is provided at the inlet of the monolith carrier 531 located on the downstream side of the exhaust passage 4. The reforming liquid fuel injection valve 532 injects the liquid fuel sent from the liquid fuel tank 51 toward the reforming catalyst.

  The reformer 53 is configured as described above, and reforms the liquid fuel injected from the reforming liquid fuel injection valve 532 into gas fuel using the heat of the exhaust gas flowing through the exhaust passage 4. In this embodiment, gasoline is reformed to hydrogen, which is a gas fuel.

  The gas fuel pump 54 is provided in a gas fuel pipe 57 a that connects the outlet of the monolith carrier 531 located upstream of the exhaust passage 4 and the gas fuel tank 55. The gas fuel pump 54 pressurizes the gas fuel generated by the reformer 53 and sends it to the gas fuel tank 55.

  The gas fuel tank 55 stores gas fuel. The gas fuel tank 55 is provided with a pressure sensor 551 and a temperature sensor 552.

  The pressure sensor 551 detects the internal pressure of the gas fuel tank 55.

  The temperature sensor 552 detects the internal temperature of the gas fuel tank 55.

  The gas fuel injection valve 56 is provided in the cylinder head 2 so as to face the combustion chamber 13. The gas fuel injection valve 56 directly injects the gas fuel sent from the gas fuel tank 55 through the gas fuel pipe 57 b into the combustion chamber 13.

  The compression ratio variable mechanism 6 connects the piston 12 and the crankshaft 14 with two links (upper link 61 and lower link 62), and controls the lower link 62 with a control link 63 to thereby control the mechanical compression ratio of the engine 100. To change.

  The upper link 61 has an upper end connected to the piston 12 via the piston pin 15 and a lower end connected to one end of the lower link 62 via the upper pin 64.

  The lower link 62 has one end connected to the upper link 61 via the upper pin 64 and the other end connected to the control link 63 via the control pin 65. Further, the lower link 62 swings around the crank pin 14b as a central axis by inserting the crank pin 14b of the crankshaft 14 into a substantially central connecting hole. The lower link 62 can be divided into left and right members.

  The crankshaft 14 includes a plurality of journals 14a, a crankpin 14b, and a counterweight 14c. The journal 14 a is rotatably supported by the cylinder block 1 and the ladder frame 16. The crank pin 14b is eccentric by a predetermined amount from the journal 14a, and a lower link 62 is slidably connected thereto. The counterweight 14c is provided on the arm portion that connects the journal 14a and the crankpin 14b, and removes the weight imbalance of the rotating portion.

  One end of the control link 63 is connected to the lower link 62 via the control pin 65, and the other end is connected to the control shaft 67 via the connection pin 66. The control link 63 swings around the connecting pin 66. A gear is formed on the control shaft 67, and the gear meshes with a pinion 69 a provided on the rotation shaft 69 of the actuator 68. The control shaft 67 is rotated by the actuator 68, and the connecting pin 66 moves.

  The controller 7 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). In addition to signals from the pressure sensor 551 and the temperature sensor 552 that detect the state of the gas fuel tank 55, signals from various sensors that detect the operating state of the engine 100 are input to the controller 7. The controller 7 selects the starting fuel according to the state of the gas fuel tank 55, and changes the compression ratio according to the starting fuel. Hereinafter, after explaining the compression ratio changing method, this starting control will be explained.

  FIG. 2 is a view for explaining a compression ratio changing method by the compression ratio variable mechanism 6.

  The compression ratio variable mechanism 6 changes the compression ratio by rotating the control shaft 67 and changing the position of the connecting pin 66.

  For example, as shown in FIGS. 2 (A) and 2 (C), when the connecting pin 66 is set to the position P, the top dead center position (TDC) is increased and a high compression ratio is obtained.

  As shown in FIGS. 2B and 2C, when the connecting pin 66 is set to the position Q, the control link 63 is pushed upward, and the position of the control pin 65 is raised. As a result, the lower link 62 rotates counterclockwise about the crank pin 14b, the upper pin 64 is lowered, and the position of the piston 12 at the top dead center (TDC) of the piston 12 is lowered. Therefore, the compression ratio becomes a low compression ratio.

  FIG. 3 is a flowchart illustrating the start control according to the present embodiment. The controller 7 executes this routine at a predetermined calculation cycle (for example, 10 ms) while the engine 100 is operating.

  In step S1, the controller 7 determines whether or not the ignition switch is turned off. If the ignition switch is turned off, the controller 7 shifts the process to step S2, and if not, shifts the process to step S10.

  In step S <b> 2, the controller 7 stops the fuel injection if the fuel is injected from the liquid fuel injection valve 52, the reforming liquid fuel injection valve 532, and the gas fuel injection valve 56.

  In step S <b> 3, the controller 7 detects the internal pressure and internal temperature of the gas fuel tank 55.

  In step S4, the controller 7 calculates the internal pressure (hereinafter referred to as “predicted internal pressure”) of the gas fuel tank 55 at the next start based on the detected internal pressure and internal temperature of the gas fuel tank 55.

  In step S5, the controller 7 determines whether or not the predicted internal pressure is higher than a predetermined gas fuel supplyable pressure. If the predicted internal pressure is higher than the gas fuel supply possible pressure, the controller 7 shifts the process to step S6, and if not, shifts the process to step S8.

  In step S6, the controller 7 uses the fuel supplied at the next start (hereinafter referred to as “startup fuel”) as gas fuel.

  In step S7, the controller 7 changes the compression ratio to a predetermined starting compression ratio for gas fuel.

  In step S8, the controller 7 uses the starting fuel as liquid fuel.

  In step S9, the controller 7 changes the compression ratio to a predetermined liquid fuel start compression ratio. The starting compression ratio for liquid fuel is higher than the starting compression ratio for gas fuel. This is because in the case of liquid fuel, an amount of heat for vaporizing the fuel is required.

  In step S10, the controller 7 determines whether or not the engine is being started or warmed up. The controller 7 shifts the process to step S11 if the engine is starting or warming up, and otherwise shifts the process to step S12.

  In step S11, the controller 7 carries out start-up control. Specifically, when the gas fuel is selected as the starting fuel, the gas fuel is supplied while maintaining the compression ratio at the starting compression ratio for the gas fuel. On the other hand, when the liquid fuel is selected as the starting fuel, the liquid fuel is supplied while maintaining the compression ratio at the starting compression ratio for the liquid fuel.

  In step S12, the controller 7 performs normal time control. Specifically, the compression ratio is controlled according to the operating state, and liquid fuel is injected.

  FIG. 4 is a time chart for explaining the operation of the start control according to the present embodiment. In order to clarify the correspondence with the flowchart, the step numbers of the flowchart will be described together.

  When the ignition switch is turned off at time t1 (FIG. 4A; Yes in S1), a predicted internal pressure is calculated based on the internal pressure and the internal temperature of the gas fuel tank 55 (S3, S4), and the prediction is performed. A starting fuel is selected based on the internal pressure (S5).

  When gas fuel is selected as the starting fuel, that is, when it is determined that the predicted internal pressure is higher than the gas fuel supplyable pressure and that it is possible to start with gas fuel (Yes in S5, S6), a one-dot chain line As shown, the compression ratio is changed to a starting compression ratio for gas fuel having a relatively low compression ratio (FIG. 4B; S7). On the other hand, when the liquid fuel is selected as the starting fuel, that is, when it is determined that the predicted internal pressure is lower than the gas fuel supplyable pressure and the starting with the gas fuel is impossible (No in S5, S8). As shown by the broken line, the compression ratio is changed to the starting compression ratio for liquid fuel having a relatively high compression ratio (FIG. 4B; S9). This starting compression ratio is maintained until the ignition switch is turned on at time t2 (FIG. 4B).

  When the ignition switch is turned on at time t2 (FIG. 4A; No in S1), engine 100 is started. The starting fuel selected when the ignition switch is turned off while maintaining the starting compression ratio changed when the ignition switch is turned off, until time t3 when warm-up is completed after the engine 100 is started. (FIG. 4 (B); Yes in S11, S12).

  When the warm-up is completed at time t3, the compression ratio is controlled according to the operating state, and the liquid fuel is injected (FIG. 4B; No in S11, S12).

  According to the present embodiment described above, gas fuel and liquid fuel can be arbitrarily selected and supplied to the engine 100, and gas fuel is supplied at the time of starting.

  When the engine 100 is started by supplying liquid fuel, if the liquid fuel is vaporized and not burned, a desired combustion pressure cannot be obtained and startability deteriorates, and unburned fuel (hydrocarbon; HC) Is exhausted and exhaust performance deteriorates. For this reason, it is necessary to increase the compression ratio compared to when gas engine is supplied and engine 100 is started by the amount of heat required to vaporize the fuel as compared with gas fuel. However, if a high compression ratio is required at the time of starting, the starting torque increases, so the burden on the starter motor increases and the starting performance deteriorates.

  On the other hand, when the engine 100 is started by supplying gas fuel, the amount of heat for vaporizing the fuel is not necessary, so that the fuel can be burned with a low compression ratio. Thereby, cranking can be performed in a low compression ratio state, so that the starting torque can be reduced, and the startability can be improved as compared with the case where the engine 100 is started by supplying liquid fuel. Further, the exhaust performance is not deteriorated.

  In addition, since the selection of the starting fuel and the change to the starting compression ratio are performed when the engine is stopped, it is not necessary to change the compression ratio at the time of starting. Therefore, cranking can be started quickly at the start, and startability can be further improved.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  For example, in the present embodiment, gas fuel and liquid fuel can be arbitrarily selected and supplied to the engine 100. However, two or more types of liquid fuel having different vaporization characteristics can be arbitrarily selected and supplied to the engine 100. It may be. In this case, the liquid fuel having the best vaporization characteristics among the liquid fuels that can be supplied, i.e., the liquid fuel that is most easily vaporized is supplied at start-up, and the compression ratio is increased as the liquid fuel with good vaporization characteristics is supplied. You can lower it. Thereby, the effect similar to the said embodiment can be acquired.

  In this embodiment, the gas fuel is generated by the reformer 53, but may be supplied from the outside in the same manner as the liquid fuel.

  Further, the reforming reaction is not limited to the partial oxidation reaction as in the present embodiment. For example, the reformed gas obtained by the reforming together with the gas component (hydrogen) is condensed and separated as in the dehydrogenation reaction. The reaction may also be a liquid component. In this case, if the vaporization characteristics of the liquid fuel after reforming and the liquid fuel before reforming are different, the liquid fuel after reforming is stored in a separate tank, and the liquid fuel before reforming, If the liquid fuel and the gas fuel are properly used, precise start control can be performed. Further, the liquid fuel may be separated by distillation.

  Further, in the present embodiment, hydrogen is used as the gas fuel, but vaporized gasoline or other gas fuel may be used.

5 Fuel Supply Device 6 Compression Ratio Variable Mechanism 12 Piston 14 Crankshaft 55 Gas Fuel Tank 61 Upper Link (Multiple Links)
62 Lower link (multiple links)
63 Control links (multiple links)
67 Controller shaft 68 Actuator (drive device)
100 engine (internal combustion engine)
551 Pressure sensor (fuel condition detection sensor)
552 Temperature sensor (fuel condition detection sensor)
S4 Predicted internal pressure calculating means S5 Starting fuel selecting means S6 Starting fuel selecting means, gas fuel selecting means S7 Compression ratio changing means S8 Starting fuel selecting means S9 Compression ratio changing means

Claims (7)

A variable compression ratio mechanism capable of changing the compression ratio;
A fuel supply device capable of arbitrarily selecting and supplying a plurality of fuels having different vaporization characteristics;
An internal combustion engine start control device comprising:
Starting fuel selection means for selecting a starting fuel to be supplied from the plurality of fuels at the time of starting;
Compression ratio changing means for lowering the compression ratio the better the gasification characteristics of the starting fuel,
A start control device for an internal combustion engine, comprising: 2. The start control device for an internal combustion engine according to claim 1, wherein the start fuel selection unit selects a fuel having the best vaporization characteristic among the fuels that can be supplied as the start fuel. The starting fuel selection means selects the starting fuel to be supplied at the next start when the engine is stopped,
3. The start control device for an internal combustion engine according to claim 1, wherein the compression ratio changing means changes the compression ratio when the engine is stopped based on a vaporization characteristic of the start fuel selected when the engine is stopped. A variable compression ratio mechanism capable of changing the compression ratio;
A fuel supply device that arbitrarily supplies and supplies either gas fuel or liquid fuel;
An internal combustion engine start control device comprising:
Starting fuel selection means for selecting whether the starting fuel supplied at the time of starting is the gas fuel or the liquid fuel;
Compression ratio changing means for reducing a compression ratio when the gas fuel is supplied to be lower than a compression ratio when the liquid fuel is supplied;
A start control device for an internal combustion engine, comprising: The fuel supply device includes:
A gas fuel tank for storing gas fuel;
A fuel state detection sensor for detecting the state of gas fuel in the gas fuel tank;
With
The starting fuel selection means includes
Predicted internal pressure calculating means for calculating a predicted internal pressure of the gas fuel tank at the next start based on the state of the gas fuel detected by the fuel state detection sensor;
Gas fuel selection means for selecting gas fuel as a starting fuel when the predicted internal pressure is higher than a predetermined pressure;
The start control device for an internal combustion engine according to claim 4, comprising: The starting fuel selection means selects the starting fuel to be supplied at the next start when the engine is stopped,
The start control device for an internal combustion engine according to claim 4 or 5, wherein the compression ratio changing means includes changing the compression ratio when the engine is stopped based on the starting fuel selected when the engine is stopped. The compression ratio variable mechanism is
A control shaft extending substantially parallel to the crankshaft;
A plurality of links connecting the piston, the crankshaft and the control shaft;
A driving device for rotating the control shaft;
With
The compression ratio is changed by rotating the control shaft and changing the support position of one of the plurality of links, one end of which is swingably supported by the control shaft. A start control device for an internal combustion engine according to any one of claims 1 to 6.

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