JP2009216050A - Control device for internal combustion engine - Google Patents

Abstract

A control device for an internal combustion engine capable of improving the low temperature startability of an engine by using a valve stop mechanism.
An engine is provided with an exhaust-side valve stop mechanism that closes the exhaust valve by stopping the lift operation of the exhaust valve. When the engine is started, fuel injection and ignition are started after performing a predetermined period of pumping control for cranking in a state where the lift operation of the exhaust valve 10 is stopped.
[Selection] Figure 1

Description

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

  A multi-cylinder internal combustion engine having a valve stop mechanism that closes the engine valve (intake valve or exhaust valve) of some cylinders to stop the engine valve is known (for example, a patent) Literature 1 etc.).

  Various multi-cylinder internal combustion engines have been proposed in which fuel consumption and the like are improved by performing so-called reduced-cylinder operation in which operation of some cylinders is stopped during engine operation (for example, Patent Document 1).

Such an internal combustion engine is provided with a valve stop mechanism that stops the lift operation of engine valves (intake valves and exhaust valves) of some cylinders to close the engine valves. When the reduced-cylinder operation is performed, the operation of some cylinders is stopped by stopping the lift operation, fuel injection, and ignition of the engine valves of the cylinders provided with the valve stop mechanism. .
JP-A-5-163971

By the way, when the internal combustion engine is started in a low temperature environment, the engine fuel is hardly vaporized and fuel atomization is not easily promoted, so that the engine startability tends to deteriorate.
Here, the lift operation by the valve stop mechanism is generally stopped during engine operation. However, by appropriately using such a valve stop mechanism also at the time of engine start, the low-temperature start as described above. The inventor has found that the properties can be improved.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a control device for an internal combustion engine that can improve the low-temperature startability of the engine by using a valve stop mechanism.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, in the control device for an internal combustion engine having a valve stop mechanism that stops the lift operation of the exhaust valve and closes the exhaust valve, the lift operation of the exhaust valve is stopped when the engine is started. The gist of the present invention is to start fuel injection and ignition after performing a predetermined period of pumping control for cranking in a state in which the fuel is allowed to enter.

  According to this configuration, when starting the engine, first, the lift operation of the exhaust valve is stopped by the valve stop mechanism, and the pumping control is performed to perform cranking while the exhaust valve is in the closed state. . As a result, during pumping control, intake air travels between the cylinder and the intake passage. Here, during cranking, heat is generated due to friction between the cylinder inner wall and the piston ring, and the temperature of the intake air traveling between the cylinder and the intake passage gradually increases due to the frictional heat. After such pumping control is performed for a predetermined period to raise the temperature of the intake air, fuel injection and ignition are started, so that atomization of the injected fuel is promoted and the mixture is suitably ignited. become. Thus, according to the same structure, the low temperature startability of an engine can be improved using a valve stop mechanism.

  According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect, prior to the fuel injection performed after the execution of the pumping control, preliminary injection is performed during the execution of the pumping control. The gist.

  According to this configuration, the preliminary injection performed during execution of the pumping control raises the temperature of the air-fuel mixture during the execution of the pumping control, and promotes atomization of the fuel in the air-fuel mixture. Therefore, the air-fuel mixture can be ignited more reliably at the start of ignition after the completion of the pumping control.

  According to a third aspect of the present invention, in the control device for an internal combustion engine according to the first or second aspect, the internal combustion engine includes a variable lift mechanism that varies a maximum lift amount of the intake valve, and performs the pumping control. The main point is that the maximum lift amount is reduced as compared with the non-execution time.

  When the maximum lift amount of the intake valve is reduced, the flow velocity of the intake air passing between the valve seat of the intake port and the valve portion of the intake valve increases, and the intake air passing between the valve seat and the valve portion is increased. The frictional heat will be generated. Therefore, by reducing the maximum lift amount of the intake valve, the temperature of the intake air flowing into the cylinder rises. Therefore, in this configuration, the internal combustion engine is provided with a variable lift mechanism that makes the maximum lift amount of the intake valve variable. During the execution of the above-described pumping control, the intake valve 9 is compared with the non-execution time. The maximum lift is reduced. For this reason, the temperature of the intake air during the pumping control can be further increased.

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to any one of the first to third aspects, a low-temperature determination condition in which at least one of a cooling water temperature and an intake air temperature of the internal combustion engine is set in advance. The gist is to execute the pumping control when satisfying.

  According to this configuration, the pumping control can be executed only when the low-temperature startability deteriorates, and unnecessary pumping control can be suppressed.

  The gist of the invention described in claim 5 is that the internal combustion engine is an engine capable of using alcohol fuel in the control apparatus for an internal combustion engine according to any one of claims 1 to 4.

  Alcohol fuel is harder to vaporize than gasoline fuel, so when alcohol fuel is actually used in an internal combustion engine that can use alcohol fuel, the temperature is lower than when only gasoline fuel is used. The startability is further deteriorated. In this regard, according to the same configuration, by performing the pumping control, it is possible to improve the low temperature startability when using alcohol fuel. In this configuration, the engine fuel used may be a mixed fuel of alcohol fuel and gasoline fuel.

(First embodiment)
A first embodiment of a control device for an internal combustion engine according to the present invention will be described below with reference to FIGS.

  An engine 1 shown in FIG. 1 is a multi-cylinder internal combustion engine having a plurality of cylinders, and is an engine that can use not only gasoline fuel but also alcohol fuel or a mixed fuel of gasoline fuel and alcohol fuel as engine fuel. It has become.

  A throttle valve 29 is provided in the intake passage 3 of the engine 1, and the opening of the throttle valve 29 is adjusted by adjusting the opening degree of the throttle valve 29 based on the depression amount of the accelerator pedal 17 (accelerator depression amount). An amount of air corresponding to the degree is supplied to the combustion chamber 2 of each cylinder through the intake passage 3. A fuel injection valve 4 is provided in the cylinder head of the engine 1, and an amount of fuel corresponding to the intake air amount of the engine 1 is directly injected from the fuel injection valve 4 into the cylinder. As a result, an air-fuel mixture consisting of air and fuel is formed in the combustion chamber 2 of each cylinder in the engine 1. When the air-fuel mixture is ignited by the spark plug 5, the air-fuel mixture burns and the piston 6 Reciprocates, and the crankshaft 7 that is the output shaft of the engine 1 rotates. Then, the air-fuel mixture after combustion is sent out from each combustion chamber 2 to the exhaust passage 8 as exhaust gas. The crankshaft 7 is cranked by being rotated by the starter motor 200 when the engine is started.

  In each cylinder of the engine 1, the combustion chamber 2 and the intake passage 3 are communicated / blocked by the opening / closing operation of the intake valve 9, and the combustion chamber 2 and the exhaust passage 8 are communicated / opened by the opening / closing operation of the exhaust valve 10. Blocked. The intake valve 9 and the exhaust valve 10 are opened and closed with the rotation of the intake camshaft 11 and the exhaust camshaft 12 to which the rotation of the crankshaft 7 is transmitted. More specifically, the intake valve 9 is urged in the valve closing direction by an intake side valve spring 40, and a roller 18 is interposed between the intake cam 11 a fixed to the intake camshaft 11 and the intake valve 9. The provided rocker arm 19 is provided. When the rotating intake cam 11 a presses the roller 18, the rocker arm 19 swings around a contact point with the lash adjuster 20 that supports one end of the rocker arm 19, and the intake air is resisted against the reaction force of the intake side valve spring 40. Press the valve 9. The intake valve 9 is opened and closed by the pressure of the intake valve 9 by the rocker arm 19 and the reaction force of the intake side valve spring 40. The exhaust valve 10 is biased in the valve closing direction by an exhaust side valve spring 41, and a rocker arm provided with a roller 21 between the exhaust cam 12a fixed to the exhaust cam shaft 12 and the exhaust valve 10. 22 is provided. When the rotating exhaust cam 12a presses the rocker arm 22, the rocker arm 22 swings around a contact point with the lash adjuster 23 that supports one end of the rocker arm 22 against the reaction force of the exhaust side valve spring 41. The exhaust valve 10 is pressed. The exhaust valve 10 is opened and closed by the pressure of the exhaust valve 10 by the rocker arm 22 and the reaction force of the exhaust side valve spring 41.

  In the engine 1, in addition to the all-cylinder operation in which all cylinders are operated, a so-called reduced-cylinder operation is performed in which operation of some cylinders is stopped and fuel consumption is improved by operating only the remaining cylinders. The In such a reduced cylinder operation, in some cylinders of the engine 1, the fuel injection from the fuel injection valve 4 is stopped and the energization to the spark plug 5 for igniting the air-fuel mixture is stopped, and the intake valve 9 and This is realized by stopping the lift operation of the exhaust valve 10. The lift stop of the intake valve 9 is performed by an intake side valve stop mechanism 24 provided in the rocker arm 19, and the lift stop of the exhaust valve 10 is performed by an exhaust side valve stop mechanism 25 provided in the rocker arm 22.

  The intake side valve stop mechanism 24 provided on the rocker arm 19 between the intake cam 11a and the intake valve 9 lifts (opens and closes) the intake valve 9 based on the pressure of the intake cam 11a on the rocker arm 19 (roller 18). It is possible to stop.

  When the intake side valve stop mechanism 24 is operated, the roller 18 is allowed to move relative to the rocker arm 19 in the direction of pressing, and when the intake side valve stop mechanism 24 is not operated, such relative movement is restricted. When the intake side valve stop mechanism 24 is not in operation, the relative movement of the roller 18 with respect to the rocker arm 19 is restricted, so that when the roller 18 is pressed by the intake cam 11a, the rocker arm 19 is moved as described above. And the intake valve 9 is opened and closed. On the other hand, when the intake side valve stop mechanism 24 is operated, the roller 18 moves relative to the rocker arm 19, and therefore, when the roller 18 is pressed by the intake cam 11 a, the roller 18 is relative to the rocker arm 19. It moves, so to speak, it ’s like an empty swing. Therefore, the rocker arm 19 is stopped from swinging, whereby the lift operation of the intake valve 9 accompanying the rotation of the intake cam 11a is stopped, and the intake valve 9 is closed.

  The exhaust side valve stop mechanism 25 provided on the rocker arm 19 between the exhaust cam 12a and the exhaust valve 10 lifts (opens / closes) the exhaust valve 10 based on the pressure of the exhaust cam 12a against the rocker arm 22 (roller 21). It is possible to stop.

  The exhaust side valve stop mechanism 25 also has the same structure as the intake side valve stop mechanism 24 described above. When the exhaust side valve stop mechanism 25 is operated, the roller 21 moves in the direction of pressing against the rocker arm 22. Relative movement is enabled, and such relative movement is restricted when not in operation. When the exhaust-side valve stop mechanism 25 is not in operation, the relative movement of the roller 21 with respect to the rocker arm 22 is restricted, and when the roller 21 is pressed by the exhaust cam 12a, the rocker arm 22 is moved as described above. And the exhaust valve 10 is opened and closed. Therefore, as shown in FIG. 2, when the operation of the exhaust side valve stop mechanism 25 is stopped, the lift amount of the exhaust valve 10 continuously changes from “0” to the maximum lift amount VL.

  On the other hand, when the exhaust-side valve stop mechanism 25 is in operation, the roller 21 moves relative to the rocker arm 22, so that when the roller 21 is pressed by the exhaust cam 12 a, the roller 21 is relative to the rocker arm 22. It moves, so to speak, it ’s like an empty swing. As a result, the rocker arm 22 stops swinging, whereby the lift operation of the exhaust valve 10 accompanying the rotation of the exhaust cam 12a is stopped, and the exhaust valve 10 is also closed. That is, as shown in FIG. 2, when the exhaust-side valve stop mechanism 25 is operated, the lift amount of the exhaust valve 10 is maintained at “0”.

  As shown in FIG. 1, the engine 1 is provided with various sensors. For example, the accelerator position sensor 28 detects the depression amount (accelerator depression amount) of the accelerator pedal 17 that is depressed by the driver of the automobile. Further, the throttle position sensor 30 detects the opening degree (throttle opening degree) of the throttle valve 29 provided in the intake passage 3. Further, the amount of air (intake air amount GA) taken into the combustion chamber 2 through the intake passage 3 is detected by the air flow meter 32. The crank position sensor 34 detects the rotation angle of the crankshaft 7, that is, the crank angle, and calculates the engine rotation speed NE based on the detection signal. A rotation angle of the intake camshaft 11 is detected by a cam angle sensor 35 provided in the vicinity of the intake camshaft 11, and cylinder discrimination is made based on detection values of the cam angle sensor 35 and the crank position sensor 34. The The intake air temperature sensor 36 detects the intake air temperature (intake air temperature) THA, and the water temperature sensor 37 detects the engine coolant temperature (cooling water temperature) THW. An ignition switch (hereinafter referred to as an IG switch) 38 detects an engine start request and an engine stop request by the driver, and when the IG switch 38 is turned on, the starter motor 200 is driven, that is, cranked. Is started.

  Various controls of the engine 1 are performed by the electronic control unit 26. The electronic control unit 26 includes a CPU that executes arithmetic processing related to the above-described various controls, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores arithmetic results of the CPU, and an external interface. The input / output port for inputting / outputting the signal is provided. The input ports are connected to signal lines such as the various sensors and switches. Further, the fuel injection valve 4, the spark plug 5, the throttle valve 29, the intake side valve stop mechanism 24, the exhaust side valve stop mechanism 25, the drive circuit of the starter motor 200, and the like are connected to the output port. The device 26 outputs a command signal to various drive circuits connected to the output port according to the engine operation state detected by the various sensors. Thus, fuel injection control of the fuel injection valve 4, ignition timing control of the spark plug 5, opening control of the throttle valve 29, drive control of the intake side valve stop mechanism 24, exhaust side valve stop mechanism 25, drive control of the starter motor 200, etc. Is implemented by the electronic control unit 26.

  The reduced-cylinder operation and all-cylinder operation of the engine 1 are switched according to the engine operation state. That is, as shown in FIG. 3, when the engine operation state grasped based on the engine speed and the engine load is a low rotation and low load state and is within a preset reduced cylinder operation region G, the engine operation state is reduced. Cylinder operation is performed. Note that if the reduced-cylinder operation is performed in a region where the engine rotation speed is excessively low, the torque output from the engine 1 will be significantly fluctuated. Therefore, in the present embodiment, extremely low rotation is performed from the reduced-cylinder operation region G. The area is excluded.

  During this reduced-cylinder operation, fuel injection by the fuel injection valve 4 and ignition by the spark plug 5 are stopped for some cylinders, and the intake valve 9 and exhaust valve 10 of the cylinder in which the fuel injection and ignition are stopped are performed. The opening / closing operation is stopped by the operation of the intake side valve stop mechanism 24 and the exhaust side valve stop mechanism 25. In this way, at the time of low rotation and low load, that is, when the amount of air (air mixture) sucked per cycle with respect to the operating cylinder is small, the operation of some cylinders is stopped by the reduced cylinder operation. Thus, the amount of air (air mixture) sucked per cycle with respect to the remaining operating cylinders is increased. As a result, the amount of intake air per cycle (amount of air-fuel mixture) in the operating cylinder during the reduced cylinder operation is the amount of intake air per cycle in the operating cylinder when the high cylinder load operation is performed in all cylinder operations ( The value is close to the amount of air-fuel mixture). Here, since the combustion efficiency tends to be higher at the time of high load operation of the engine than at the time of low load operation, the fuel efficiency of the engine 1 can be improved at the time of low load operation in which reduced cylinder operation is performed. Become. Further, since the pumping loss of the intake air does not occur for the cylinders whose operation has been stopped, the fuel efficiency of the engine 1 can be improved also by this.

  On the other hand, when the engine operating state is in a region outside the above-described reduced-cylinder operating region G, in other words, when it is in the all-cylinder operating region A, all-cylinder operation is executed. During this all-cylinder operation, fuel injection by the fuel injection valve 4 and ignition by the spark plug 5 are performed for all cylinders, and the intake side valve stop mechanism 24 and the exhaust side valve stop mechanism 25 are deactivated. All intake valves 9 and exhaust valves 10 are opened and closed.

  By the way, when the engine 1 is started under a low temperature environment, the engine fuel is hardly vaporized and fuel atomization is not easily promoted, so that the engine startability tends to deteriorate. In particular, when alcohol fuel or the above mixed fuel is used in the engine 1, since such fuel is less likely to vaporize than gasoline fuel, the cold startability is further deteriorated as compared with the case where only gasoline fuel is used. It becomes easy. Therefore, in the present embodiment, the low-temperature startability of the engine 1 is improved by appropriately using the above-described valve stop mechanism, particularly the exhaust side valve stop mechanism 25 at the time of engine start.

  FIG. 4 shows the procedure of the pumping process executed when the engine is started. This process is started by the electronic control unit 26 when the engine is started, in other words, when the IG switch 38 is operated from the off state to the on state.

When this process is started, first, driving of the starter motor 200 is started (S100).
Then, it is determined whether or not the current start is a low temperature start (S110). Here, affirmative determination is made when at least one of the low temperature determination conditions such as “intake air temperature THA ≦ determination temperature TA” or “cooling water temperature THW ≦ determination temperature TB” is satisfied. The determination temperature TA and the determination temperature TB are appropriately set to values that can determine that the engine is started in a low temperature environment in which alcohol fuel is less likely to vaporize and the low temperature startability of the engine 1 is reduced. Yes.

  If it is not a low temperature start (S110: NO), it is determined whether or not cylinder discrimination is completed (S160). If a negative determination is made (S160: NO), until cylinder discrimination is completed. The process of step S160 is repeated. On the other hand, when the cylinder discrimination is completed (S160: YES), fuel injection by synchronous injection is executed for all cylinders, and ignition by the spark plug 5 is executed (S180). Is terminated.

  If it is determined in step S110 that the engine is cold starting (S110: YES), only the exhaust side valve stop mechanism 25 is operated among the valve stop mechanisms described above (S120), and the counter K Measurement is started (S130). The counter K measures the operating time of the exhaust side valve stop mechanism 25, and is incremented by a constant value every predetermined time. When the operation of the exhaust side valve stop mechanism 25 is stopped, it is reset to “0”.

  Next, it is determined whether or not the current counter K is greater than or equal to the determination value C (S140). If a negative determination is made (S140: NO), step S140 is performed until the counter K becomes equal to or greater than the determination value C. This process is repeated. On the other hand, when the counter K is equal to or larger than the determination value C (S140: YES), it is determined whether or not the cylinder determination is completed (S150), and when the determination is negative (S150: NO), the cylinder determination is performed. Until the process is completed, the process of step S150 is repeated. On the other hand, when the cylinder discrimination is completed (S150: YES), the operation of the exhaust side valve stop mechanism 25 is stopped (S170).

Then, fuel injection by synchronous injection is executed for all the cylinders, and ignition by the spark plug 5 is executed (S180), and this process ends.
Next, the operational effect of the pumping process will be described with reference to FIG.

  When the starter motor 200 is started to be driven (time t1), when it is determined that the start is low temperature, the exhaust valve stop mechanism 25 is activated to stop the lift operation of the exhaust valve 10. More specifically, pumping control is performed to perform cranking while the exhaust valve 10 is held in the closed state. Further, the measurement of the counter K is started by the start of the operation of the exhaust side valve stop mechanism 25.

  During the execution of the pumping control, the intake valve 9 performs a lift operation while the exhaust valve 10 is held in a closed state, so that intake air travels between the cylinder and the intake passage 3. Here, during the cranking, heat is generated due to friction between the cylinder inner wall of the cylinder and the piston ring. Therefore, the temperature of the intake air passing between the cylinder and the intake passage 3 by the pumping control is gradually increased by the friction heat. To rise.

  When the counter K becomes equal to or greater than the determination value C (time t2), it is determined that the temperature of the intake air has risen to a temperature suitable for the atomization of alcohol fuel by performing the pumping control for a predetermined period. If the cylinder discrimination is completed at this time, the pumping control is terminated and the operation of the exhaust side valve stop mechanism 25 is stopped, whereby the lift operation of the exhaust valve 10 is started and the engine is started. The fuel injection and ignition accompanying this are started. At the start of fuel injection and ignition, fuel atomization is promoted by performing fuel injection on the intake air whose temperature has been raised by the pumping control. And since the ignition plug 5 performs ignition with respect to the air-fuel mixture in which the temperature has risen to some extent and fuel atomization has been promoted, the air-fuel mixture is reliably ignited.

  By performing such a series of processes, even when starting the engine in a low-temperature environment, fuel atomization is promoted to ensure that the air-fuel mixture is ignited, thereby improving the low-temperature startability of the engine. become.

As described above, according to the present embodiment, the following effects can be obtained.
(1) When starting the engine, the temperature of the intake air is raised by executing a pumping control for performing cranking in a state where the exhaust valve 10 is held in the closed state through the operation of the exhaust side valve stop mechanism 25. ing. The fuel injection and ignition are started after the pumping control is executed for a predetermined period. Thus, by using the exhaust side valve stop mechanism 25 when starting the engine, the low temperature startability of the engine can be improved.

  (2) The pumping control is executed when at least one of the intake air temperature THA and the coolant temperature THW satisfies a preset low temperature determination condition. Therefore, the pumping control can be executed only when the low temperature startability of the engine 1 is deteriorated, and the unnecessary pumping control can be suppressed.

(3) In the engine 1 that can use alcohol fuel, the pumping process is performed when the engine is started. Therefore, even when an alcohol fuel that tends to deteriorate the cold startability is used as the engine fuel, the cold startability of the engine 1 can be improved.
(Second Embodiment)
Next, a second embodiment in which the control device for an internal combustion engine according to the present invention is embodied will be described with reference to FIGS.

  In the present embodiment, the engine 1 is provided with a variable lift mechanism that makes the maximum lift amount of the intake valve 9 variable. When performing the above-described pumping control, the variable lift mechanism is also used to perform the pumping control. The temperature of the intake air being executed can be further increased.

Hereinafter, the control device for the internal combustion engine in the present embodiment will be described focusing on the differences from the first embodiment.
FIG. 6 shows the configuration of the engine 1 in the present embodiment. In addition, about the same member as the member demonstrated in previous FIG. 1, about each member shown in FIG. 6, the same code | symbol is attached | subjected.

  As shown in FIG. 6, a variable lift mechanism 14 is provided between the intake camshaft 11 and the intake rocker arm 19 to vary the maximum lift amount VL of the intake valve 9. The operation amount of the variable lift mechanism 14 is controlled by the electric motor 15. The electric motor 15 is provided with a drive amount detection sensor 39 for detecting the drive amount.

  The variable lift mechanism 14 includes an input arm 14a that contacts the intake cam 11a, an output arm 14b that contacts the roller 18 of the rocker arm 19, and a mechanism that continuously changes the relative phase between the input arm 14a and the output arm 14b. Thus, a phase change mechanism and the like whose operation amount is controlled by the electric motor 15 are provided.

  In the variable lift mechanism 14, the relative phase is changed so that the input arm 14a and the output arm 14b approach each other, whereby the rocking amount of the rocker arm 19 is reduced and the maximum lift amount VL of the intake valve 9 is reduced. To come. On the contrary, when the relative phase is changed so that the input arm 14a and the output arm 14b are separated from each other, the rocking amount of the rocker arm 19 is increased and the maximum lift amount VL of the intake valve 9 is increased. . That is, by continuously changing the relative phase between the input arm 14a and the output arm 14b by the electric motor 15, the maximum lift amount VL of the intake valve 9 is changed from the minimum value VLmin to the maximum value VLmax as shown in FIG. Continuously changed between. Incidentally, the target lift amount VLp, which is the target value of the maximum lift amount VL, is calculated based on, for example, the operation amount of the accelerator pedal. Further, the actual maximum lift amount VL of the intake valve 9 is grasped based on the detection signal of the drive amount detection sensor 39. Then, the drive amount of the electric motor 15 is controlled by the electronic control unit 26 so that the target lift amount VLp and the actual maximum lift amount VL coincide with each other.

  By the way, as shown in FIG. 8, when the maximum lift amount VL of the intake valve 9 is decreased, the intake air passing through the opening of the intake port, more specifically, between the valve seat 50a and the valve portion 9a of the intake valve 9, is reduced. The flow velocity is increased, and frictional heat is generated in the intake air passing between the valve seat 50a and the valve portion 9a. Accordingly, by reducing the maximum lift amount VL of the intake valve 9, the temperature of the intake air flowing into the cylinder rises.

  Therefore, in the present embodiment, during the execution of the pumping control described above, the maximum lift amount VL of the intake valve 9 is decreased as compared with the non-execution time, thereby further increasing the temperature of the intake air during the execution of the pumping control. The low temperature startability is improved.

Hereinafter, the pumping process in this embodiment will be described.
FIG. 9 shows the procedure of the pumping process that is executed when the engine is started in this embodiment. This process is also started by the electronic control unit 26 when the engine is started, in other words, when the IG switch 38 is operated from the off state to the on state.

When this process is started, first, driving of the starter motor 200 is started (S200).
Then, it is determined whether or not the current start is a low temperature start (S210). In this case as well, an affirmative determination is made when at least one of the low temperature determination conditions such as “intake air temperature THA ≦ determination temperature TA” or “cooling water temperature THW ≦ determination temperature TB” is satisfied. The determination temperature TA and the determination temperature TB are the same as those in the first embodiment.

  If it is not a low temperature start (S210: NO), it is determined whether or not cylinder discrimination is completed (S270). If a negative determination is made (S270: NO), until cylinder discrimination is completed. The process of step S270 is repeatedly performed. On the other hand, when the cylinder discrimination is completed (S270: YES), fuel injection by synchronous injection is executed for all the cylinders, and ignition by the spark plug 5 is executed (S310). Is terminated.

  If it is determined in step S210 that the engine is cold starting (S210: YES), only the exhaust side valve stop mechanism 25 is activated among the valve stop mechanisms described above (S220). Measurement is started (S230). This counter K also measures the operating time of the exhaust side valve stop mechanism 25, and is incremented by a constant value every predetermined time. When the operation of the exhaust side valve stop mechanism 25 is stopped, it is reset to “0”.

  Next, the pumping lift amount VLpum is set as the target lift amount VLp, whereby the maximum lift amount VL of the intake valve 9 is changed to the pumping lift amount VLpum (S240).

  Next, it is determined whether or not the current counter K is equal to or greater than the above-described determination value C (S250). If a negative determination is made (S250: NO), until the counter K becomes equal to or greater than the determination value C, The process of step S250 is repeatedly performed. On the other hand, when the counter K is equal to or greater than the determination value C (S250: YES), it is determined whether or not the cylinder determination is completed (S260), and when the determination is negative (S260: NO), the cylinder determination is performed. Until the process is completed, the process of step S260 is repeated. On the other hand, when the cylinder discrimination is completed (S260: YES), the operation of the exhaust side valve stop mechanism 25 is stopped (S280).

  Then, fuel injection by synchronous injection is executed for all the cylinders, ignition by the spark plug 5 is executed (S290), and the starting lift amount VLsta is set as the target lift amount VLp, whereby the intake air The maximum lift amount VL of the valve 9 is changed to the starting lift amount VLsta (S300). This process is terminated.

Next, the effect of the pumping process will be described with reference to FIG.
When the starter motor 200 is started to be driven (time t1), when it is determined that the start is low temperature, the exhaust valve stop mechanism 25 is activated to stop the lift operation of the exhaust valve 10. More specifically, pumping control is performed to perform cranking while the exhaust valve 10 is held in the closed state. Further, the measurement of the counter K is started by the start of the operation of the exhaust side valve stop mechanism 25. Further, the maximum lift amount VL of the intake valve 9 is changed to the pumping lift amount VLpum in accordance with the start of execution of the pumping control, so that the maximum lift amount VL is reduced compared to when the pumping control is not executed.

  During the execution of the pumping control, as described in the first embodiment, the intake valve 9 is lifted while the exhaust valve 10 is held in the closed state. As the air travels inside and outside, the temperature of the intake air during the travel increases due to the heat generated by the friction between the cylinder inner wall of the cylinder and the piston ring. Furthermore, in the present embodiment, during the execution of such pumping control, the maximum lift amount VL of the intake valve 9 is reduced as compared with the non-execution time, so that the intake air temperature is compared with the case where only the pumping control is performed. Will rise further.

  When the counter K becomes equal to or greater than the determination value C (time t2), it is determined that the temperature of the intake air has increased to a temperature suitable for the atomization of alcohol fuel. If the cylinder discrimination is completed at this time, the pumping control is terminated and the operation of the exhaust side valve stop mechanism 25 is stopped, whereby the lift operation of the exhaust valve 10 is started and the engine is started. The fuel injection and ignition accompanying this are started. At the start of fuel injection and ignition, fuel atomization is further promoted by performing fuel injection on the intake air whose temperature has been raised by the pumping control and the reduction in the maximum lift amount VL of the intake valve 9. And since the ignition plug 5 performs ignition with respect to the air-fuel mixture in which the temperature has risen to some extent and fuel atomization has been promoted, the air-fuel mixture is reliably ignited. The maximum lift amount VL of the intake valve 9 is increased from the pumping lift amount VLpum to the starting lift amount VLsta suitable for engine starting.

  By performing such a series of processes, even when starting the engine in a low temperature environment, fuel atomization is further promoted to ensure that the air-fuel mixture is ignited, thereby improving the low temperature startability of the engine. It becomes like this.

As described above, according to the present embodiment, the following effects can be obtained in addition to the effects of the first embodiment.
(4) The variable lift mechanism 14 that makes the maximum lift amount VL of the intake valve 9 variable is provided in the engine 1, and the maximum lift amount VL is reduced during execution of the pumping control as compared to when it is not executed. I try to let them. For this reason, the temperature of the intake air during the pumping control can be further increased.

In addition, each said embodiment can also be changed and implemented as follows.
-Fuel injection and ignition are started after confirming completion of cylinder discrimination, but the execution time of the pumping control is set long enough to complete cylinder discrimination during execution of pumping control. The processing for determining completion of cylinder discrimination may be omitted.

  -The operation time of the exhaust side valve stop mechanism 25 by the pumping control is measured by the counter K. In addition, the operation time may be grasped by measuring the rotation amount (crank angle) of the crankshaft 7 after the operation of the exhaust side valve stop mechanism 25 is started.

  In the first embodiment, the temperature of the intake air is raised by the pumping control, more strictly, the temperature of the air taken into the cylinder. In addition, as shown in FIG. 11, prior to the fuel injection (time t2) performed after the pumping control is performed, the preliminary injection is performed while the pumping control is being performed (while the exhaust side valve stop mechanism 25 is operating). (Time t1 + α). For example, fuel injection by synchronous injection may be executed once for all cylinders after the start of pumping control and when cylinder discrimination is completed. In this case, the preliminary injection performed during the execution of the pumping control raises the temperature of the air-fuel mixture during the execution of the pumping control, and the atomization of the fuel in the air-fuel mixture is promoted. Therefore, the air-fuel mixture can be ignited more reliably at the start of ignition after the completion of the pumping control. This modification can also be implemented in the second embodiment.

  Incidentally, when performing the preliminary injection, it is desirable to reduce the injection amount in the first fuel injection started after the completion of the pumping control in accordance with the injection amount at the time of preliminary injection.

  In the second embodiment, the determination value C is set to the same value as in the first embodiment. However, if the temperature rise of the intake air by the pumping control is set to the same level as in the first embodiment, the determination value C is set to A smaller value is also possible. In this case, the start time of fuel injection and ignition can be advanced by shortening the execution time of the pumping control.

  ・ The above pumping control is executed when it is determined that the engine is cold starting. However, it is not always necessary to determine that the engine is cold starting, and the pumping control is executed regardless of the environmental temperature when starting the engine. It may be. Also in this case, it is possible to improve the cold startability when starting the engine in a low temperature environment.

  When the exhaust side valve stop mechanism 25 is hydraulically driven and the hydraulic pump is driven by the rotation of the crankshaft 7, it is possible to sufficiently secure the hydraulic pressure at the time of low rotation such as when the engine is started. The exhaust side valve stop mechanism 25 may not be operated. Therefore, an electric hydraulic pump is provided, and when starting the engine, first, the electric hydraulic pump is driven to ensure the hydraulic pressure. If the operation of the exhaust side valve stop mechanism 25 is started after the hydraulic pressure is secured, even if the exhaust side valve stop mechanism 25 is hydraulically driven, it can be operated when the engine is started.

  -The exhaust valve 10 is kept closed by the operation of the exhaust side valve stop mechanism 25. In addition, the exhaust-side valve stop mechanism 25 is stopped so that the exhaust valve 10 is held in the closed state, and the exhaust-side valve stop mechanism 25 is operated so that the exhaust valve 10 is lifted. The mechanism 25 may be configured so that the exhaust-side valve stop mechanism 25 is inactivated when the engine is started. Even in this case, the pumping control as described above can be executed. In this modification, the exhaust valve stop mechanism 25 is hydraulically driven, and even when the hydraulic pump is driven by the rotation of the crankshaft 7, the exhaust valve can be held closed when the engine is started. It becomes possible.

  The engine 1 is an engine that includes the intake side valve stop mechanism 24 and the exhaust side valve stop mechanism 25, but the present invention can be implemented even in an engine that does not include the intake side valve stop mechanism 24. .

  The engine 1 is a cylinder injection type internal combustion engine that directly injects fuel into the cylinder. In addition, the present invention can be similarly applied to a port injection type internal combustion engine that injects fuel into the intake passage. In this case, fuel injection can be started by asynchronous injection without waiting for completion of cylinder discrimination. The preliminary injection can also be executed by asynchronous injection without waiting for completion of cylinder discrimination. Incidentally, the present invention is applied not only to an internal combustion engine having only a fuel injection valve for in-cylinder injection or a fuel injection valve for port injection, but also to an internal combustion engine having both fuel injection valves for in-cylinder injection and port injection. Is applicable.

-Not only the variable lift mechanism 14 demonstrated in 2nd Embodiment but the variable lift mechanism which makes variable the maximum lift amount VL of the intake valve 9 with another structure may be sufficient.
The engine 1 is an engine that can use alcohol fuel, but the present invention can be similarly applied to an engine that can use only gasoline fuel. Can be made.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the internal combustion engine to which this is applied, and its periphery structure about 1st Embodiment of the control apparatus of the internal combustion engine concerning this invention. The conceptual diagram which shows the lift amount of the exhaust valve at the time of the action | operation of the exhaust side valve stop mechanism of the embodiment, and a stop. The conceptual diagram which shows an all-cylinder operation area | region and a reduced cylinder operation area | region. The flowchart which shows the procedure about the pumping process in the embodiment. The timing chart which shows the control aspect by the pumping process of the embodiment. Schematic which shows the internal combustion engine in 2nd Embodiment, and its periphery structure. The valve | bulb characteristic view which shows the change aspect of the maximum lift amount of the intake valve in the embodiment. The enlarged view near the opening part of an intake port. The flowchart which shows the procedure about the pumping process in the embodiment. The timing chart which shows the control aspect by the pumping process of the embodiment. The timing chart which shows the control aspect by the pumping process in the modification of 1st Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Combustion chamber, 3 ... Intake passage, 4 ... Fuel injection valve, 5 ... Spark plug, 6 ... Piston, 7 ... Crankshaft, 8 ... Exhaust passage, 9 ... Intake valve, 9a ... Valve part, 10 DESCRIPTION OF SYMBOLS ... Exhaust valve, 11 ... Intake cam shaft, 11a ... Intake cam, 12 ... Exhaust cam shaft, 12a ... Exhaust cam, 14 ... Variable lift mechanism, 14a ... Input arm, 14b ... Output arm, 15 ... Electric motor, 17 ... Accelerator Pedal, 18 ... Roller, 19 ... Rocker arm, 20 ... Rush adjuster, 21 ... Roller, 22 ... Rocker arm, 23 ... Rush adjuster, 24 ... Intake side valve stop mechanism, 25 ... Exhaust side valve stop mechanism, 26 ... Electronic control unit, 28 ... Accelerator position sensor, 29 ... Throttle valve, 30 ... Throttle position sensor, 50a ... Valve seat, 32 ... Airflow Meter, 34 ... Crank position sensor, 35 ... Cam angle sensor, 36 ... Intake temperature sensor, 37 ... Water temperature sensor, 38 ... Ignition switch (IG switch), 39 ... Drive amount detection sensor, 40 ... Intake valve spring, 41 ... Exhaust side valve spring, 200 ... starter motor.

Claims (5)

In a control device for an internal combustion engine comprising a valve stop mechanism for stopping a lift operation of an exhaust valve and closing the exhaust valve,
A control apparatus for an internal combustion engine, characterized in that, at the time of engine start, fuel injection and ignition are started after performing a predetermined period of pumping control in which cranking is performed with the lift operation of the exhaust valve stopped. The control device for an internal combustion engine according to claim 1, wherein preliminary injection is performed during execution of the pumping control prior to the fuel injection performed after execution of the pumping control. The internal combustion engine includes a variable lift mechanism that makes a maximum lift amount of an intake valve variable, and the maximum lift amount is reduced during execution of the pumping control compared to when it is not executed. The internal combustion engine control device described. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the pumping control is executed when at least one of a cooling water temperature and an intake air temperature of the internal combustion engine satisfies a preset low temperature determination condition. The control apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the internal combustion engine is an engine capable of using alcohol fuel.

Images