JP2006138229A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly activate a catalyst device by increasing exhaust gas temperature at cold engine and secure an acceleration responsiveness from an idling condition. <P>SOLUTION: Variable valve trains capable of variably controlling lift/operating angle and center angle are provided on both of an intake valve and an exhaust valve of an internal combustion engine. The lift/operating angle of the exhaust valve gets small and exhaust valve open timing is retarded after bottom dead center as characteristics 104, 105 at the time of cold engine as compared with characteristics 101 after warming up in idling. Consequently, exhaust gas is compressed in a cylinder to raise temperature and increase pumping loss. The intake valve gets characteristics to increase engine load at cold engine. Lift characteristics of the exhaust valve is preferentially variably controlled like the characteristics 104→the characteristics 102 at a time of acceleration from the cold engine condition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine having a catalyst device in an exhaust system, and more particularly to a technique for realizing an early temperature increase of the catalyst device by variable control of an exhaust valve.

Patent Document 1 discloses a technique for variably controlling the valve lift characteristic of an exhaust valve and increasing the exhaust temperature in order to activate the exhaust purification catalyst device provided in the exhaust system early after the engine is started. And Patent Document 2. The technology of Patent Document 1 is a configuration in which the exhaust valve is driven to open and close by an electromagnetic drive mechanism. The exhaust gas temperature is raised to increase the catalyst temperature quickly. The technology of Patent Document 2 includes a mechanism that can variably control the operating angle of the valve lift characteristic and its central angle as a variable valve mechanism of the exhaust valve. When the engine is cold, the operating angle is reduced and the central angle is reduced. Is advanced to advance both the exhaust valve opening timing and the exhaust valve closing timing. Thus, the exhaust temperature is raised and the engine temperature is also raised.
JP 2001-289075 A JP 2001-355469 A

  However, in the technique of Patent Document 1, the exhaust temperature is raised by retarding the opening timing of the exhaust valve. However, since the solenoid valve is used as the exhaust valve, the valve lift amount is always large, Extrusion loss does not increase. Therefore, particularly in the idle state, the engine load cannot be increased without increasing the engine rotation speed, and therefore, the increase range of the exhaust temperature is not so large.

  In order to increase the engine load by variable control using an exhaust valve composed of a solenoid valve having a large lift, the exhaust valve opening period (operating angle) is shortened to increase the exhaust extrusion loss. It is necessary to let However, in order to set an appropriate exhaust valve opening timing, the exhaust valve closing timing will be set before the top dead center, so that the amount of unburned HC emissions increases due to combustion deterioration due to an increase in residual gas. Occurs. On the other hand, if the exhaust valve closing timing is set near top dead center in order to reduce residual gas, the exhaust valve opening timing is also set near top dead center, so the high pressure after recompressing the burned gas The exhaust valve is opened below, and a new problem arises that it is necessary to increase the actuator capacity for operating the solenoid valve.

  In the technique of Patent Document 2, since the exhaust valve closing timing is advanced before the top dead center when the engine is cold, the ignition timing cannot be largely retarded due to the deterioration of combustion stability due to the increase in the residual gas amount, and the exhaust temperature is reduced. It cannot be raised effectively. In addition, since the exhaust valve opening timing during cold operation is more advanced than the exhaust valve opening timing during warm-up, the exhaust compression work is not performed and the exhaust extrusion is not performed as compared with the case of retarding after bottom dead center. Since the loss is reduced, the engine load cannot be increased while maintaining the shaft torque constant, and the exhaust temperature cannot be increased effectively.

  According to the present invention, the exhaust purification catalyst device provided in the exhaust system, the exhaust valve lift characteristic changing means for changing the lift amount and opening / closing timing of the exhaust valve, and the lift of the intake valve are provided. An intake valve lift characteristic changing means for changing the amount and opening / closing timing, and a cooler detecting means for detecting the cold state of the engine, and the exhaust valve so that the engine load becomes larger than the shaft torque when the engine is cold. In the internal combustion engine that raises the exhaust temperature by controlling the lift characteristics of the intake valve so that the shaft torque satisfies the required shaft torque, the shaft torque when starting acceleration from the cold idling state Is characterized in that the lift characteristic of the exhaust valve is variably controlled with priority over the lift characteristic of the intake valve.

  For example, when the engine is in a cold state and in an idling state, the exhaust valve lift characteristic is set so that the exhaust valve lift amount is smaller than that during warm-up and the exhaust valve opening timing is greatly delayed. As a result, the exhaust valve is opened after the already burned gas is compressed again after the expansion stroke, and the exhaust stroke starts. Therefore, the recompression work is performed, and the exhaust gas is discharged with a small exhaust valve lift amount. As a result, the extrusion loss increases, so that the actually output shaft torque decreases compared to the engine load (fuel amount, intake air amount). On the other hand, the lift characteristic of the intake valve is a characteristic in which the intake air amount increases more than the state after the warm-up so as to satisfy the required shaft torque necessary for maintaining the idle rotation speed. Therefore, the engine load is significantly increased as compared with the shaft torque, and the exhaust gas temperature is significantly increased as compared with the warm-up time.

  In the present invention, when starting acceleration from such a cold idling state, in the present invention, the lift characteristics of the intake valve are maintained so as to maintain a large engine load during cold, and the lift characteristics of the exhaust valve are preferentially variably controlled. Then, the actually output shaft torque is increased. This makes it possible to properly control the distribution of the energy discharged as high-temperature exhaust gas and the energy that becomes the engine shaft torque, while generating the required shaft torque and the maximum possible exhaust gas increase effect at that time Is obtained.

  FIG. 1 is an explanatory diagram of the invention according to claim 1. For example, after warm-up, the exhaust valve and the intake valve have lift characteristics indicated by reference numeral 101 in the idling state, and shaft torque With the increase, the lift characteristic changes like the characteristic 102 and the characteristic 103. Each lift characteristic is shown as a general valve timing chart with the top dead center above the circle and the bottom dead center below the circle. As is well known, the arc on the left side of the figure is the exhaust valve, The arc on the right side of the figure is the intake valve opening period. Further, in this example, as will be described later, a mechanism is used in which the lift amount and the operating angle increase and decrease at the same time. Therefore, the lift amount increases as the operating angle increases. In FIG. 1, the vertical axis represents the axial torque and the horizontal axis represents the engine load, and the position of each circle represents the axial torque and the engine load at that time.

  On the other hand, when the engine is in the cold state, the lift characteristics of the exhaust valve and the intake valve are controlled like the characteristics 104 and 105 when the engine is in the idling state. That is, the shaft torque is low and the engine load is large. And when starting acceleration from such an idling state, in this invention, the lift characteristic of an exhaust valve changes preferentially. For example, if the state is the state of the characteristic 104 in the idling state, the characteristic changes as follows: characteristic 104 → characteristic 102 (strictly different from the characteristic 102 after warm-up). If it is in the state of the characteristic 105 in the idling state, it changes as follows: characteristic 105 → characteristic 106 (also strictly different from the characteristic 106 after warming up).

  More specifically, the exhaust valve lift amount in the cold state is smaller than the exhaust valve lift amount after the warm-up, and the exhaust valve opening timing in the cold state is the exhaust valve open time after the warm-up. Slower than time. FIG. 2 is an explanatory diagram of the invention of claim 2. In the lift characteristic at the time of cooling exemplified as the characteristic 202 or the characteristic 203, the exhaust valve is compared with the lift characteristic after warm-up exemplified as the characteristic 201. The lift amount (in other words, the operating angle) is relatively small, and the exhaust valve opening timing is relatively retarded. Each of the characteristics 201 to 203 is an example of a lift characteristic when in an idling state.

  Thus, by making the exhaust valve lift amount during cold operation smaller than the exhaust valve lift amount after warming up, high-temperature and high-pressure exhaust gas is forcibly forced by the lift of the piston through the gap between the slightly open exhaust valves. Since the exhaust gas is discharged, the extrusion loss of the exhaust gas in the exhaust stroke is greatly increased. Therefore, in order to maintain the same shaft torque as after warm-up, it is necessary to increase the intake air amount and the fuel amount, and the engine load increases. Accordingly, a larger amount of high-temperature exhaust gas is discharged, and the catalyst can be activated early. Moreover, if the exhaust valve is opened later than the bottom dead center, the burnt gas burned in the expansion stroke is compressed again after the bottom dead center to become high temperature and high pressure, and the exhaust extrusion work is a small lift. It is further increased compared to the case of only conversion. Therefore, even higher temperature exhaust gas is discharged, and the temperature of the catalyst device in the exhaust system rises rapidly.

  The invention according to claim 3 is characterized in that the lift characteristic of the exhaust valve is preferentially variably controlled over the lift characteristic of the intake valve so that the shaft torque is reduced when the vehicle is decelerated from the non-idling state when cold. To do. FIG. 3 is an explanatory diagram of the invention of claim 3, wherein the characteristic 301 is an example of the lift characteristic in the idling state after warm-up, and the characteristics 302 and 303 are the lift in the idling state at the time of cooling. Examples of characteristics are shown respectively. Characteristic 304 and characteristic 305 are characteristic examples in a non-idling state when the engine is cold, and when the vehicle is decelerated from this state, the lift characteristic of the exhaust valve is preferentially changed so as to approach the characteristics 302 and 303. . For example, the lift amount of the exhaust valve is reduced and the opening timing is retarded.

  In this way, by variably controlling the lift characteristic of the exhaust valve during deceleration, the lift characteristic of the intake valve is basically maintained as it is so that the intake air amount does not decrease, and the engine load is not reduced. Torque is suppressed. Therefore, the effect of increasing the exhaust gas temperature is increased.

  In the invention according to claim 4, when the fuel cut is performed when the engine is cold and the vehicle is decelerated from the non-idling state, the exhaust valve opening timing at the time of sudden deceleration is relative to the exhaust valve opening timing at the time of slow deceleration. It is characterized in that it is controlled so as to be on the retard side.

  FIG. 4 is an explanatory diagram of the invention of claim 4 and is in the state of the characteristic 401 before the start of deceleration, and finally changes from this state to the characteristic 402. If there is, a characteristic 403 is obtained, and if it is a slow deceleration, a characteristic 404 is obtained. Thus, by retarding the opening timing of the exhaust valve more greatly at the time of sudden deceleration, the recompression work after the end of the expansion stroke becomes large, and the engine braking action can be increased.

  Further, in the invention according to claim 5, when the fuel cut is performed at the time of cooling and when decelerating from the non-idling state, the exhaust valve lift amount / operating angle at the time of sudden deceleration is greater than the exhaust valve lift amount at the time of slow deceleration. It is characterized by being controlled so as to be relatively smaller than the operating angle.

  FIG. 5 is an explanatory diagram of the invention of claim 5 and is in the state of the characteristic 501 before the start of deceleration, and finally changes from this state to the characteristic 502. If there is, it becomes like the characteristic 503, and if it is slow deceleration, it becomes like the characteristic 504. By reducing the lift amount during sudden deceleration in this way, the exhaust valve opening area is reduced when the burned gas is discharged after the end of the expansion stroke, so that the exhaust gas extrusion loss increases and the engine braking action can be increased. .

  Further, in the invention according to claim 6, when the fuel cut is performed at the time of cooling and when decelerating from the non-idling state, the intake valve lift amount at the time of sudden deceleration and the operating angle are the intake valve lift amount at the time of slow deceleration, It is characterized by being controlled to be relatively larger than the operating angle.

  FIG. 6 is an explanatory diagram of the invention of claim 6 and is in the state of the characteristic 601 before the start of deceleration, and finally changes from this state to the characteristic 602. If there is, a characteristic 603 is obtained, and if it is a slow deceleration, a characteristic 604 is obtained. By increasing the lift amount and operating angle of the intake valve during sudden deceleration in this way, the intake air amount is increased, and the engine braking action is further increased by reducing the exhaust valve lift amount and retarding the exhaust valve opening timing. To do.

  The invention according to claim 7 is characterized in that the exhaust valve lift amount / operating angle is controlled to the exhaust valve lift amount / operating angle at the time of cold idling when fuel cut is performed at the time of rapid deceleration during cold engine. .

  FIG. 7 is an explanatory diagram of the invention of claim 7 and is in the state of the characteristic 701 before the start of deceleration, and finally changes from this state to the characteristic 702. In the process, the characteristic 703 It becomes like this. By controlling in this way, after the fuel cut, the engine speed is rapidly reduced and fuel injection is resumed. When trying to return to the engine speed / shaft torque state during idling, misfire or engine speed It is possible to return to the idle state immediately without changing the speed.

  The invention according to claim 8 is characterized in that the intake valve lift amount / operating angle is larger and the exhaust valve lift amount / operating angle is smaller when idling when the engine is cold than when idling after warming up. FIG. 8 is an explanatory diagram of the invention of claim 8, showing a characteristic example when the characteristic 801 is in the idling state after warm-up, and a characteristic example when the characteristic 802 is in the idling state during cold. In this way, by making the intake valve lift amount and operating angle larger during idling during cold engine operation than during idling during warm engine operation, engine load during idling during cold engine operation is greater than during idling during warm engine operation. Will increase. Furthermore, by making the exhaust valve lift and operating angle smaller when idling during cold engine operation than when idling during warm engine operation, the shaft torque is warmed up even though the engine load during idling during cold engine operation is greater. The exhaust gas temperature can be made higher than that during idling due to the large engine load due to the fact that it can be made equivalent to that during idling.

  The invention according to claim 9 is characterized in that both the lift characteristics of the intake valve and the lift characteristics of the exhaust valve are variably controlled at the same time if a rapid acceleration is requested when acceleration is started from the idling state during cold. FIG. 9 is an explanatory diagram of the invention of claim 9. In the idling state at the time of cold, the setting is the characteristic 901 or the characteristic 902. For example, when accelerating from the state of the characteristic 901, the deceleration is slow. By changing the lift characteristic of the exhaust valve preferentially and variably, the characteristic changes from 901 → characteristic 903 → characteristic 904. On the other hand, in the case of rapid acceleration, both the lift characteristic of the exhaust valve and the lift characteristic of the intake valve are variably controlled at the same time, so that the characteristic changes as 901 → characteristic 905 → characteristic 904. By controlling in this way, the shaft torque increases rapidly, so that it is possible to respond to a rapid acceleration request.

  The invention according to claim 10 detects at least one of the engine temperature and the catalyst temperature, and the larger the deviation between the predetermined set value corresponding to the warm-up state and the detected temperature, the larger the engine load with respect to the shaft torque. The lift characteristic of the exhaust valve is controlled so as to increase the ratio.

  FIG. 10 is an explanatory diagram of the invention of claim 10, and the upper part of the figure shows the amount of divergence of the catalyst temperature and the engine temperature (for example, lubricating oil temperature and cooling water temperature) with respect to the warm-up temperature. Depending on the amount of deviation, as shown in the lower part of the figure, the engine load during cold cooling varies. The shaft torque is basically constant. Therefore, the larger the deviation amount, the larger the ratio of the engine load to the shaft torque. By controlling in this way, the engine load increases as the engine temperature or the catalyst temperature decreases, and the catalyst can be activated rapidly.

  According to the present invention, when the internal combustion engine is operated with a high engine load when cold, a large amount of high-temperature exhaust gas is obtained, and the catalyst device is activated early. And, when starting acceleration from the idling state during cold engine, the lift characteristics of the exhaust valve are preferentially variably controlled to increase the ratio of shaft torque to engine load, so that good acceleration response can be ensured and the catalyst Early activation can be continued as much as possible.

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

  FIG. 11 is a configuration explanatory view showing a system configuration of the internal combustion engine 1 according to the present invention. The internal combustion engine 1 has an intake valve 3 and an exhaust valve 4, and both the intake valve 3 and the exhaust valve 4. In addition, variable valve mechanisms 5 and 6 are provided. These variable valve mechanisms 5 and 6 have basically the same configuration, and can be a first variable valve that can continuously expand and contract the lift and operating angle of the intake valve 3 or the exhaust valve 4. Mechanisms (VEL) 5a and 6a and second variable valve mechanisms (VTC) 5b and 6b capable of continuously delaying the central angle of the operating angle are provided. The intake passage 7 is provided with an electronically controlled throttle valve 2 whose opening degree is controlled by an actuator such as a motor, and an air flow meter 8 for detecting an intake air flow rate is provided upstream thereof, and An intake pressure sensor 9 is provided in the downstream intake collector 7a. A fuel injection valve 10 is provided for each cylinder so as to inject fuel toward the intake port of each cylinder. A spark plug 15 is arranged in the center of the combustion chamber.

  Here, the throttle valve 2 is used only for generating a slight negative pressure (for example, −50 mmHg) necessary for processing blow-by gas in the intake passage 7 and adjusting the intake air amount. Is performed by changing the lift characteristic of the intake valve 3 by the variable valve mechanism 5. That is, a substantial throttle-less operation that does not depend on the throttle valve opening for adjusting the intake air amount is realized. An amount of fuel corresponding to the intake air amount adjusted by the intake valve 3 as described above is injected from the fuel injection valve 10.

  In addition, a catalyst device 12 using, for example, a three-way catalyst is interposed in the exhaust passage 11, and an air-fuel ratio sensor 13 is disposed on the upstream side thereof. The catalyst device 12 includes a catalyst temperature sensor 14 that detects the temperature. Further, the internal combustion engine 1 is provided with a water temperature sensor 16 for detecting the cooling water temperature. Further, an accelerator opening sensor 17 for detecting the opening degree of an accelerator pedal operated by a driver and a vehicle speed sensor 18 for detecting a vehicle speed are provided, and the detection signals of these sensors are respectively supplied to a control unit 19. Has been entered.

  Based on the signals input from these sensors, the control unit 19 controls the fuel injection amount, the ignition timing, the throttle opening of the throttle valve 2, the lift / operating angle and the central angle of the intake valve 3, the exhaust valve 4 The lift, operating angle, center angle, etc. are controlled respectively.

  The variable valve mechanisms 5 and 6 combining the first variable valve mechanisms 5a and 6a and the second variable valve mechanisms 5b and 6b are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2002-256905 and 2002-89341. It is the same structure as the well-known thing disclosed by the gazette. In this case, the lift amount and the operating angle are increased and decreased simultaneously and continuously by the first variable valve mechanisms 5a and 6a, and the phase of the central angle of the operating angle is continuously changed by the second variable valve mechanisms 5b and 6b. Slow. Therefore, the valve opening / closing timing and the lift amount can be variably controlled according to the operating conditions by the combination of both. Thereby, the various lift characteristics of the exhaust valve 4 and the intake valve 3 of FIGS.

  For example, as is clear from the comparison between the characteristic 101 after warm-up in FIG. 1 and the characteristic 104 during cold, the exhaust valve opening timing is retarded from the bottom dead center and the exhaust valve lift amount is small during cold. It becomes. As the exhaust valve opening timing is retarded in this way, the temperature at which the exhaust gas is compressed in the cylinder and discharged into the exhaust passage 11 increases. Further, by reducing the lift amount of the exhaust valve 4, the extrusion loss increases. If the engine load, that is, the fuel amount and the intake air amount are the same, the shaft torque output to the outside decreases. On the other hand, the intake valve 3 basically has a small operating angle when idling, but by closing the intake valve closing timing closer to the bottom dead center side when cold, compared to the idling state after warming up, The engine load is increased (intake air amount and fuel amount associated therewith). This increase in engine load is offset by a decrease in shaft torque due to an increase in extrusion loss or the like, and the shaft torque output to the outside is kept constant. In addition to the increase in the operating angle of the intake valve 3, the engine load during cold operation may be increased by increasing the opening of the throttle valve 2.

Explanatory drawing of invention of Claim 1. Explanatory drawing of invention of Claim 2. Explanatory drawing of invention of Claim 3. Explanatory drawing of invention of Claim 4. Explanatory drawing of invention of Claim 5. Explanatory drawing of invention of Claim 6. Explanatory drawing of invention of Claim 7. Explanatory drawing of invention of Claim 8. Explanatory drawing of invention of Claim 9. Explanatory drawing of invention of Claim 10. BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which shows the system structure of the internal combustion engine which concerns on this invention.

Explanation of symbols

2 ... Throttle valve 3 ... Intake valve 4 ... Exhaust valve 5,6 ... Variable valve mechanism 12 ... Catalyst device 14 ... Catalyst temperature sensor

Claims (10)

  Exhaust purification catalyst device provided in the exhaust system, exhaust valve lift characteristic changing means for changing the lift amount and opening / closing timing of the exhaust valve, and intake valve lift characteristic changing means for changing the lift amount and opening / closing timing of the intake valve And a cooler detecting means for detecting a cold state of the engine, and when the engine is cold, the lift characteristic of the exhaust valve is controlled so that the engine load is larger than the shaft torque, and the shaft torque is the required shaft. In an internal combustion engine that raises the exhaust temperature by controlling the lift characteristics of the intake valve so as to satisfy the torque, when starting acceleration from a cold idling state, the shaft torque increases more than the lift characteristics of the intake valve. An internal combustion engine characterized by preferentially variably controlling a lift characteristic of an exhaust valve.   The exhaust valve lift amount in the cold state is smaller than the exhaust valve lift amount after the warm-up, and the exhaust valve opening timing in the cold state is later than the exhaust valve opening timing after the warm-up. The internal combustion engine described in 1.   3. The exhaust valve lift characteristic is variably controlled preferentially over the intake valve lift characteristic so that the shaft torque is reduced when decelerating from a non-idling state when the engine is cold. Internal combustion engine.   Controls so that the exhaust valve opening timing during sudden deceleration is relatively retarded than the exhaust valve opening timing during slow deceleration when fuel cut is performed during deceleration from cold and non-idling conditions The internal combustion engine according to any one of claims 1 to 3, wherein:   When a fuel cut is performed when the engine is cold and decelerated from a non-idling state, the exhaust valve lift amount / operating angle during sudden deceleration is relatively smaller than the exhaust valve lift amount / operating angle during slow deceleration. The internal combustion engine according to any one of claims 1 to 4, wherein the internal combustion engine is controlled as follows.   When a fuel cut is performed when the engine is cold and decelerated from a non-idling state, the intake valve lift amount / operating angle during sudden deceleration is relatively larger than the intake valve lift amount / operating angle during slow deceleration. The internal combustion engine according to claim 1, wherein the internal combustion engine is controlled as follows.   7. The exhaust valve lift amount / operating angle is controlled to the exhaust valve lift amount / operating angle at the time of cold idling when fuel cut is performed at the time of rapid deceleration during cold engine. The internal combustion engine described in 1.   The intake valve lift amount / operating angle is larger and the exhaust valve lift amount / operating angle is smaller when idling when the engine is cold than when idling after warming up. Internal combustion engine.   9. When acceleration is started from a cold idling state, if sudden acceleration is requested, both the lift characteristic of the intake valve and the lift characteristic of the exhaust valve are variably controlled at the same time. The internal combustion engine described. The engine temperature or the catalyst temperature is detected, and the ratio of the engine load to the shaft torque increases as the deviation between the predetermined set value corresponding to the warm-up state and the detected temperature increases. The internal combustion engine according to any one of claims 1 to 9, wherein lift characteristics of the exhaust valve are controlled.

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