JP2005299408A - Device for raising temperature of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise temperature of an exhaust system having catalyst without causing degradation of exhaust emission. <P>SOLUTION: Temperature raising operation M1 to raise temperature of the exhaust system until temperature of exhaust gas reaches predetermined catalyst activation temperature T°C under a condition that fuel supply by a fuel injection valve is stopped at a time of engine start. A crankshaft is driven and rotated by a starter motor (crank drive device) and open and close timing of an exhaust valve is controlled to advance side by an exhaust valve timing variable mechanism in the temperature raising operation M1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for raising the temperature of an engine exhaust system, for example, for early activation of a catalyst.

  In engines mounted in recent automobiles, etc., in order to purify harmful gas components such as hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) in the exhaust gas discharged from the combustion chamber. An exhaust purification catalyst is provided in the exhaust passage. As the exhaust purification catalyst, for example, a three-way catalyst or a NOx trap catalyst is used alone or in combination in a gasoline engine, and a DPF (diesel particulate filter) or an oxidation catalyst is preferably used in a diesel engine. Such an exhaust purification catalyst is activated when the temperature is equal to or higher than a predetermined activation temperature, so that harmful gas components in the exhaust can be purified. Therefore, if the exhaust purification catalyst does not reach the activation temperature, the harmful gas components Can not be sufficiently purified. Therefore, various techniques for raising the temperature of the exhaust purification catalyst early and activating it have been proposed.

  For example, Patent Document 1 discloses a technique in which the opening timing of the exhaust valve is advanced to the middle of the expansion stroke, high temperature gas in the middle of combustion is discharged as exhaust, and the catalyst is activated early. In addition, the opening timing of the exhaust valve is retarded until the middle of the exhaust stroke, the burned gas is compressed from the bottom dead center to the exhaust valve opening timing, the temperature is raised, and the catalyst is activated early with this hot burned gas. Is disclosed.

  In Patent Document 2, the temperature of the exhaust gas is increased by retarding the opening / closing timing of the exhaust valve when the engine is cold, thereby promoting the temperature rise of the catalyst. In addition, by delaying the closing timing of the exhaust valve, the exhaust gas once discharged into the exhaust passage is re-inhaled into the combustion chamber, slowing the combustion and promoting the temperature rise of the exhaust gas, thereby increasing the temperature of the catalyst. Promoting. Furthermore, the temperature of the catalyst is increased by retarding the ignition timing and leaning the air-fuel ratio.

  In Patent Document 3, the exhaust gas temperature is raised by retarding or advancing the closing timing of the intake valve to reduce the intake air amount. Thus, it is described that the exhaust temperature is raised without deteriorating the fuel consumption, and the catalyst is activated.

In Patent Document 4, during warm-up operation, fuel injection to a specific cylinder is stopped or reduced, and the oxygen concentration in the catalyst is made excessive to promote the oxidation reaction, thereby promoting the activation of the catalyst.
Japanese Patent Laid-Open No. 2002-227672, FIGS. 5B and 5C, and the like. JP 2002-161722 A JP 2003-120267 A Japanese Patent Laid-Open No. 02-19627

  In Patent Document 1, since the combustion gas is compressed to increase the gas temperature, the unburned fuel component remains in the exhaust gas at the time of cold start, and the unburned fuel component is not activated. May not be sufficiently purified, and exhaust emissions may be deteriorated. In Patent Document 2, since exhaust gas in the middle of combustion is discharged into the exhaust passage, unburned fuel components remain in the exhaust gas at the time of cold start, and the unburned fuel components are still sufficient in a situation where the catalyst is not activated. May not be purified. In Patent Document 3, the fuel gas discharged into the exhaust passage is re-inhaled into the combustion chamber, the exhaust gas temperature is raised, and re-intake cannot be performed in a situation where the catalyst is not activated as in cold start. There is a possibility that unburned fuel components in the exhaust gas may not be purified by the catalyst. That is, in these Patent Documents 1 to 3, since the temperature of the catalyst is to be raised in a situation where fuel is being injected, there is a possibility that unburned fuel components may remain, particularly in a situation where the catalyst is not activated. The fuel component is not sufficiently purified, and exhaust emission may be deteriorated.

  In Patent Document 4, although fuel injection to a specific cylinder is stopped in order to promote an oxidation reaction by increasing the oxygen concentration, fuel is supplied to some cylinders and the fuel is burned. Since the self-sustained operation of rotating the crankshaft is performed by this, unburned fuel components still remain, which may cause deterioration of exhaust emission.

  An object of the present invention is to provide a novel engine temperature raising device that can effectively raise the temperature of an exhaust system of an engine in which a catalyst or the like is disposed without causing deterioration of exhaust emission.

  A crank driving device that rotationally drives the crankshaft, an exhaust valve timing changing mechanism that changes the opening / closing timing of the exhaust valve, and a fuel injection device that injects and supplies fuel to the combustion chamber or the intake passage. While the fuel supply by the fuel injection device is stopped, the crankshaft is rotationally driven by the crank drive device so as to raise the temperature of the exhaust system including the exhaust passage, and the exhaust valve is opened and closed by the exhaust valve timing changing mechanism. Perform temperature rising operation to control the timing.

  According to the present invention, the driving energy of the crankshaft is controlled by controlling the opening / closing timing of the exhaust valve by the exhaust valve timing changing mechanism while rotating the crankshaft by the crank driving device in a situation where the fuel supply is stopped. Can be used to raise the temperature of the exhaust system. Since the fuel supply is stopped, there is no possibility that unburned fuel components are generated, and there is no possibility that exhaust emission will be reduced.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram of an engine to which a temperature raising apparatus according to the present invention is applied. The engine 10 is, for example, an in-line 4-cylinder spark ignition gasoline engine. The four cylinders 11 of the engine 10 are supplied with intake air through an intake passage 13 in the intake manifold 12, and exhaust gas after combustion is discharged outside the vehicle through an exhaust passage 15 in the exhaust manifold 14. A compressor of the supercharger 16 is provided at the upstream portion of the intake manifold 12. Typical turbochargers include a turbocharger using exhaust and a mechanical supercharger. An exhaust purification catalyst 17 for purifying exhaust gas is provided at the downstream side of the exhaust manifold 14. For example, a three-way catalyst is used alone, or the exhaust purification catalyst 17 is configured by combining a three-way catalyst and a NOx trap catalyst. An exhaust shutter valve 18 that opens and closes the exhaust passage 15 is provided on the downstream side of the catalyst 17.

  A fuel injection valve 21 as a fuel injection device is attached to, for example, a cylinder head so as to inject and supply fuel to a combustion chamber or an intake passage of each cylinder 11. The spark plug 22 is attached to the cylinder head in a posture facing each combustion chamber. The starter motor 23 as a crank driving device / starting device forcibly drives the crankshaft to rotate using the battery 27 as a power source / power source. The throttle valve 24 is an electrically controlled throttle valve that opens and closes a collecting portion on the upstream side of the intake passage 13.

  Further, an intake valve timing changing mechanism 25 that continuously changes the opening / closing timing of the intake valve and an exhaust valve timing changing mechanism 26 that continuously changes the opening / closing timing of the exhaust valve are provided. These valve timing mechanisms, for example, as disclosed in Japanese Patent Application Laid-Open No. 2002-235567, continuously change the timing of the intake and exhaust valves by continuously changing the phase of the camshaft with respect to the crankshaft. VTC (Valve Timing Control) mechanism that can be changed to

  The engine control unit 30 includes a catalyst temperature sensor 31 that detects the catalyst temperature of the catalyst 17, a throttle opening sensor 32 that detects the opening of the throttle valve 24 that opens and closes the intake passage, and various sensors such as a crank angle sensor. Based on the signals, command signals are output to various actuators such as a supercharger, an exhaust shutter valve 18, a fuel injection valve 21, a spark plug 22, a starter motor 23, a throttle valve 24, and valve timing changing mechanisms 25 and 26. Control the behavior. For example, a sensor for detecting or estimating the actual position of the intake / exhaust camshaft is provided, and the opening / closing timing of the intake / exhaust valve is feedback-controlled / closed-loop controlled based on the actual position.

  With reference to FIG.2 and FIG.3, the flow of the temperature rising control at the time of engine starting which concerns on one Example of this invention is demonstrated. For example, when the driver rotates the ignition key to the engine start position and an engine start request is detected, the engine control unit 30 starts the routine of FIG. 2 (step 1). The start request detection time T1 in FIG. 3 corresponds to the start time of the routine in FIG.

  When the engine start request is detected in this manner, the temperature raising operation M1 (see FIG. 3) for a predetermined period until the catalyst temperature (exhaust temperature) detected by the catalyst temperature sensor 31 reaches the predetermined catalyst activation temperature T ° C. Is done. During the temperature raising operation M1, the working gas and the exhaust passage discharged from the exhaust system, that is, the combustion chamber in the cylinder 11 to the exhaust passage 15 are maintained while the fuel supply by the fuel injection valve 21 is stopped and prohibited. The processing of the following steps 2 to 6 is executed so that the temperature of the catalyst 17 disposed in 15 is quickly raised.

  In step 2, fuel injection (start) by the combustion injection valve 21 is prohibited. In step 3, the crankshaft is forcibly rotated by the starter motor 23. Preferably, the temperature rising operation M1 is continued even if the driver does not keep the ignition key at the engine start position, and the driver turns the ignition key to the engine stop position such as the accessory position. In this case, the routine is forcibly interrupted.

  In step 4, the exhaust valve timing changing mechanism 26 controls the opening / closing timing of the exhaust valve to the advance side. Specifically, as shown in FIGS. 3 and 4, the opening / closing timing of the exhaust valve is predetermined with respect to the normal setting position of the exhaust valve opening / closing timing at the start of the engine (setting position in the idle state immediately after the complete explosion). The angle is advanced by Δθ1 (approximately 180 CA). That is, in a four-cycle engine composed of expansion / exhaust / intake and compression strokes, the opening / closing timing of the exhaust valve is advanced so that the exhaust valve opens in the expansion stroke, which is the piston lowering stroke. In order to obtain the desired temperature rise effect, the exhaust valve closing timing (EVC) should be advanced at least with respect to the exhaust top dead center (TDC), and preferably advanced to the vicinity of the expansion bottom dead center (BDC). good. Further, the exhaust valve opening timing (EVO) may be advanced at least with respect to the expansion BDC, and preferably advanced to near the compression top dead center (TDC). The exhaust valve operating angle center θ2 is advanced at least from the expansion bottom dead center BDC, more preferably to the vicinity of the center of the expansion stroke. Most preferably, the opening / closing timing of the exhaust valve is advanced so that the exhaust valve opens only within the expansion stroke.

  In step 5, the intake valve timing mechanism 25 controls the opening / closing timing of the intake valve to the retard side with respect to the normal setting position (see FIGS. 3 and 4). Specifically, the intake valve opening timing is retarded from the exhaust top dead center TDC. That is, the intake valve is retarded so as to open within the intake stroke that is the piston lowering stroke. Thereby, the temperature rising effect of the exhaust system can be relatively enhanced as compared with the temperature rising effect of the intake system.

  By setting the valve timings of the intake / exhaust valves in steps 4 and 5 as described above, as shown in FIG. 4, the exhaust valve opens in the expansion stroke which is one piston lowering stroke in the four-cycle engine, and the other piston The intake valve opens in the intake stroke, which is the downward stroke, and both the intake and exhaust valves close in the exhaust stroke, which is the piston upward stroke, and the compression stroke. Therefore, in the exhaust stroke, the working gas in the combustion chamber is compressed and heated, and the intake valve is opened near the exhaust top dead center, whereby hot working gas in the combustion chamber is supplied to the intake passage 13 and the intake system is heated. Is done. In the subsequent intake stroke, the working gas in the intake passage is supplied again into the combustion chamber as the piston descends. In the subsequent compression stroke, the working gas in the combustion chamber is compressed and heated. When the exhaust valve is opened near the compression top dead center, hot working gas in the combustion chamber is supplied to the exhaust passage 15 and the temperature of the exhaust system is increased. In the subsequent expansion stroke, the working gas in the exhaust passage is supplied into the combustion chamber as the piston descends, and in the subsequent exhaust stroke, the working gas in the combustion chamber is compressed and heated as described above.

  As described above, the working gas in the combustion chamber is compressed in both of the two piston rising strokes in one cycle, and the hot working gas compressed in the exhaust stroke which is one piston rising stroke is supplied to the intake passage. The hot working gas compressed in the compression stroke, which is the other piston ascending stroke, is supplied to the exhaust passage. Therefore, since the working gas in the intake passage 13 and the exhaust passage 15 near the combustion chamber alternately enters and exits the combustion chamber, the working gas stays without substantially flowing from the intake passage 13 to the exhaust passage 15 and burns. Both the intake system and the exhaust system are quickly heated by the compression action in the room.

  When the working gas compressed in the combustion chamber is discharged to the intake passage 13 and the exhaust passage 15, the temperature of the working gas is lowered to some extent due to the expansion action, but it is necessary for compressing the working gas in the piston ascending stroke. The energy, that is, the energy necessary for forcibly driving the crankshaft by the starter motor 23 is used to raise the working gas at a certain rate, and the intake system and exhaust system are actually heated up. It becomes. Further, as described above, since no fresh air flows, there is little loss, and the temperature rise effect is improved accordingly.

  In step 6, the throttle valve 24 is held in a predetermined open position. In other words, during the temperature raising operation M1, the throttle valve 24 is prohibited from being fully closed, and the throttle valve 24 is kept open so that the negative pressure downstream of the throttle develops and the intake air temperature is lowered. This can prevent and increase the temperature rise effect of the working gas by compression. Note that when the throttle valve 24 is opened at a general intake / exhaust valve opening / closing timing, fresh air flows and a desired temperature increase effect cannot be obtained. However, the above-described operation is performed during the temperature increase operation M1 in this embodiment. By setting the intake / exhaust valve opening / closing timing as described above, fresh air stays in the vicinity of the combustion chamber without flowing therethrough, so that even if the throttle valve 24 is maintained in the open position, the temperature rise effect is not lowered.

  In step 7, supercharging by the supercharger 16 is performed. As shown in FIG. 5, the intake air temperature is prevented from lowering due to negative intake pressure, compared to when supercharging is performed during the temperature raising operation (solid line characteristics) and when supercharging is not performed (dashed line characteristics). In addition, the temperature rise effect can be further enhanced.

  In step 8, the exhaust shutter valve 18 is closed. As a result, the heated working gas in the exhaust passage 15 can be prevented from being discharged out of the vehicle through the tail pipe on the downstream side of the catalyst 17, and the catalyst temperature raising effect can be further enhanced. Note that if the exhaust shutter valve 18 is closed in the normal intake / exhaust valve lift setting state, the pressure in the exhaust passage 15 may increase excessively, but during the temperature raising operation M1, as described above. Since the working gas alternately enters and exits from the intake / exhaust passage to the combustion chamber and the working gas substantially remains in the vicinity of the combustion chamber, the exhaust passage 15 is excessive even when the exhaust shutter valve 18 is closed. The pressure is never increased.

  In step 9, it is determined whether the exhaust purification catalyst 17 has reached a predetermined activation temperature T ° C. If it is determined that the catalyst temperature has reached the activation temperature T ° C., the process proceeds to step 11 where the temperature raising operation M1 described above is terminated and the fuel injection preparation operation M2 toward the start of fuel injection, that is, the following steps 11 to 11 are performed. 13 is executed. The temperature rise end time T2 in FIG. 3 corresponds to the time when the catalyst temperature in Step 9 reaches the activation temperature T ° C. In step 11, the throttle opening is closed (fully). As a result, it is possible to suppress or prevent a temperature drop due to fresh air intake during a transition period in which the opening / closing timing of the intake / exhaust valve is changed. In step 12, the opening / closing timing of the exhaust valve is retarded toward a normal set value. In step 13, the intake valve opening / closing timing is advanced to a normal set value.

  In step 14, it is determined whether fuel injection is possible. The fuel injection start timing T3 in FIG. 3 corresponds to the timing at which the determination in step 14 is switched from negative to positive. The change of the opening / closing timing by the intake / exhaust valve timing changing mechanisms 25, 26 inevitably involves a response delay, so if fuel supply is started immediately at the temperature rise end time T2, combustion stability may be hindered. In order to avoid this, in step 14, the fuel injection start timing T3 is determined. In other words, the fuel injection is not started before the intake / exhaust valve opening / closing timing sufficiently approaches the target normal set position value (for example, the most retarded position on the exhaust valve side), so that the startability is not deteriorated. Further, the fuel injection start timing T3 is delayed with respect to the catalyst activation timing T2. However, if the cranking speed is sufficiently high and there is no risk of reducing startability even if the fuel injection is started before the intake / exhaust valve opening / closing timing returns to the normal setting position, the fuel injection is made accordingly. The responsiveness may be improved by advancing the start time T3. For example, it is estimated whether the intake / exhaust valve opening / closing timing has reached the target set value by sensors, and fuel injection is possible when the intake / exhaust valve opening / closing timing is estimated to have reached the set value It may be determined that Alternatively, it may be determined more simply that fuel injection is possible when a predetermined period of time has passed.

  If step 14 is affirmed, the throttle valve 24 is opened (step 15), the exhaust shutter valve 18 is opened (step 16), and fuel injection by the fuel injection valve 21 and spark ignition by the spark plug 22 are started. (Step 17), so-called normal engine self-sustained operation M3 is started in which the engine 10 rotates the crankshaft by burning the fuel.

  In order to continue the temperature raising operation M1 until the catalyst temperature reaches the activation temperature T ° C., it is necessary to be able to supply sufficient power from the battery 27 to the starter motor 23. Therefore, preferably, the power or power amount of the battery 27 is detected, and when the power of the battery 27 is weak or when the power amount is small, the advance angle width of the exhaust valve timing in the temperature raising operation M1 is reduced to the battery 27. To reduce the load.

  FIG. 6 shows an example of control when the advance angle width is changed according to the electric power or the electric energy of the battery 27 as described above. For example, when the driver turns the ignition key to the accessory position to turn on the accessory key switch, this routine is started (step 21). In step 22, the amount of power of the battery 27 is detected. In step 23, referring to a control map as shown in FIG. 7, the advance angle width, that is, the conversion angle of the exhaust valve opening / closing timing is determined according to the battery power amount. As shown in the figure, the advance angle width (conversion angle) of the exhaust valve opening / closing timing is increased as the battery power amount increases. In this way, the advance operation of the exhaust valve opening / closing timing corresponding to step 4 in FIG. 2 is performed before the time when the engine start request is detected, so that the temperature raising operation M1 is promptly performed at the next engine start request. And the responsiveness can be improved.

  More preferably, when the engine is stopped, the camshaft position of the exhaust valve is advanced in advance to an advance position suitable for the temperature raising operation M1, so that the engine temperature is quickly shifted to the temperature raising operation M1 at the next engine start. Thus, the response at the time of starting the engine is further improved.

  In step 24, for example, when the starter switch is turned on when the driver turns the ignition key to the engine start position, the temperature raising operation M1 is started. Specifically, processing corresponding to steps 1 to 8 in FIG. 2 is performed, and the amount of battery power is sequentially detected. In step 25, it is determined whether the amount of power of the battery 27 is sufficient. In step 26, as in step 9 of FIG. 2, it is determined whether the catalyst temperature has reached the activation temperature T ° C. If the amount of electric power of the battery 27 is insufficient, even if the catalyst temperature has not reached the activation temperature T ° C., the process proceeds from step 25 to step 27, immediately stops the temperature raising operation M1, and proceeds to the fuel injection preparation operation M2. Transition. That is, as in steps 11 to 13 in FIG. 2, the throttle valve 24 is fully closed, the exhaust valve opening / closing timing is retarded toward the normal setting position, and the intake valve opening / closing timing is advanced toward the normal setting position. Horn. After the fuel injection preparation operation M2, fuel injection is started (step 28), and a normal engine self-supporting operation M3 is performed.

In the above embodiment, the catalyst temperature is directly detected by the catalyst temperature sensor 31, but the catalyst temperature may be estimated without providing the catalyst temperature sensor 31. For example, as shown in FIG. 8, the temperature estimation table in FIG. 9 is searched based on the water temperature detected by the water temperature sensor 34 and the outside air temperature (intake air temperature) detected by the intake air temperature sensor 35, and the temperature parameter is searched. A (A, B, C,..., X) is obtained. Also, as shown in FIG. 11, the higher the cranking speed (engine speed), the higher the temperature rise effect. Therefore, based on the cranking speed calculated based on the crank angle sensor 36 and the like, FIG. The coefficient α (α1, α2,...) Is obtained. Then, as shown in the following equation, the catalyst temperature is estimated by multiplying these temperature parameter A and coefficient α.
(Equation 1) Catalyst temperature = A × α
As shown in FIG. 11, the temperature rise effect increases as the cranking rotation speed increases. Therefore, for example, in a hybrid vehicle (HEV) that uses both an engine and a motor as a vehicle propulsion source, the battery capacity is larger and the crankshaft rotates than a general engine vehicle that uses only the engine as a vehicle propulsion source. Since the motor to be driven is also larger than the starter motor 23 described above, the cranking rotational speed (engine rotational speed) by the motor is increased by performing feedback control of the cranking rotational speed and the battery power amount. Thus, the temperature raising effect can be further enhanced.

  When an electromagnetic valve that can freely set its opening / closing timing and the number of opening / closing operations in one cycle is used as the intake / exhaust valve timing changing mechanism, it is preferable that the intake / exhaust as shown in FIG. It is time to open and close the valve. That is, the intake valve and the exhaust valve of the 4-cycle engine are each configured to open twice within one cycle, the first exhaust valve opening period 41 is set to the same period as the expansion stroke, and the second exhaust valve opening period 42 is set to the exhaust top dead center. Is set to a predetermined period immediately before. Further, the first intake valve opening period 43 is set to the same period as the intake stroke, and the second intake valve opening period 44 is set to a predetermined period immediately before the compression top dead center. As a result, the working gas supplied from the exhaust passage to the combustion chamber in the second half of the expansion stroke is compressed and heated in the combustion chamber in the exhaust stroke, and the exhaust valve opens in the second exhaust valve opening period 42 in the second half of the exhaust stroke. Thus, the air is returned to the exhaust passage again. Similarly, the working gas supplied from the intake passage to the combustion chamber in the second half of the intake stroke is compressed and heated in the combustion chamber in the compression stroke, and the intake valve is opened in the second intake valve opening period 44 in the second half of the compression stroke. As a result, it is returned to the intake passage again. That is, the working gas introduced from the exhaust passage into the combustion chamber is returned to the same exhaust passage after compression and temperature rise, and similarly the working gas introduced from the intake passage into the combustion chamber is returned to the intake passage after compression and temperature rise. Therefore, the flow of fresh air is more reliably blocked, and the temperature rise effect can be further enhanced.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, although the above embodiment is applied to a gasoline engine, it can be applied to a diesel engine as well.

  In the above embodiment, the opening timing of the intake valve is retarded from the exhaust top dead center during the temperature raising operation M1, but this retard control may be omitted or advanced. Also good. For example, the intake valve opening period in the temperature raising operation M1 may be set to be equal to the intake stroke (setting indicated by a one-dot chain line in FIG. 4).

  The characteristic technical ideas that can be understood from the above description are listed together with their effects.

  (1) A crank driving device (starter motor) 23 that rotates the crankshaft, an exhaust valve timing changing mechanism 26 that changes the opening / closing timing of the exhaust valve, and a fuel injection device that injects fuel into the combustion chamber or intake passage ( Fuel injection valve) 21. While the fuel supply by the fuel injection device 21 is stopped, the crankshaft is driven to rotate by the crank driving device 23 so that the temperature of the exhaust system including the exhaust passage 15 is increased, and the exhaust valve timing changing mechanism 26 is used to rotate the crankshaft. A heating operation M1 for controlling the opening / closing timing of the exhaust valve is performed.

  As a result, the temperature of the exhaust system can be raised without injecting and supplying fuel during the temperature raising operation M1, so there is no possibility of causing deterioration of exhaust emission due to unburned fuel. Moreover, as a crank drive device, the starter motor 23 used for general engine starting can be used, and by using a well-known valve timing mechanism, the above-mentioned components can be used without adding new parts such as a heater. A temperature raising effect can be obtained.

  (2) A crank driving device (starter motor) 23 that rotates the crankshaft, an exhaust valve timing changing mechanism 26 that changes the opening / closing timing of the exhaust valve, and a fuel injection device that injects fuel into the combustion chamber or intake passage ( A fuel injection valve) 21 and an exhaust purification catalyst 17 disposed in the exhaust passage 15 so that the temperature of the exhaust purification catalyst 17 is raised in a state where the fuel supply by the fuel injection device 21 is stopped. Then, the crankshaft is driven to rotate by the crank driving device 23, and the temperature raising operation M1 is performed in which the exhaust valve timing changing mechanism 26 controls the opening / closing timing of the exhaust valve. Similar to (1) above, the catalyst 17 can be warmed up and activated early during the heating operation M1, without deteriorating exhaust emissions due to unburned fuel.

  (3) A catalyst temperature detecting means (catalyst temperature sensor 31) for detecting the catalyst temperature of the exhaust purification catalyst 17 is provided, and the temperature raising operation M1 is performed until the catalyst temperature reaches a predetermined temperature. As a result, the catalyst 17 can be reliably activated while the fuel supply is stopped, and the exhaust purification performance is further improved.

  (4) Preferably, an exhaust shutter valve 18 for closing the exhaust passage on the downstream side of the exhaust purification catalyst 17 is provided during the temperature raising operation M1. By closing the downstream side of the exhaust purification catalyst 17 by the exhaust shutter valve 18 in this way, it is possible to prevent high-temperature working gas from flowing out downstream of the catalyst, and to further enhance the temperature rising effect of the catalyst. In addition, as described above, the opening and closing timing of the exhaust valve is controlled so that the working gas stays in the vicinity of the combustion chamber, so that the working gas in the exhaust passage becomes excessively high even when the exhaust shutter valve 18 is closed. Can be prevented.

  (5) Specifically, during the temperature raising operation M1, the exhaust valve timing changing mechanism 26 advances the closing timing of the exhaust valve from the exhaust top dead center of the 4-cycle engine. By closing the exhaust valve before exhaust top dead center in this way, the working gas in the combustion chamber is compressed and heated in the exhaust stroke after the exhaust valve is closed, so that the above temperature rising effect can be obtained. .

  (6) More specifically, during the temperature raising operation M1, the exhaust valve timing changing mechanism 26 advances the opening timing of the exhaust valve from the expansion bottom dead center of the 4-cycle engine. By opening the exhaust valve before the expansion bottom dead center in this way, the working gas in the combustion chamber that has been compressed and heated in the immediately preceding compression stroke is supplied to the exhaust passage, so that the above temperature rising effect is obtained. If the exhaust valve is opened after the expansion bottom dead center, the combustion gas compressed and heated in the compression stroke is adiabatically expanded in the expansion stroke, and its temperature is greatly reduced, so that a desired temperature rising effect can be obtained. Can not.

  (7) Preferably, in the temperature raising operation M1, the exhaust valve timing changing mechanism 26 advances the operating angle center of the exhaust valve from the expansion bottom dead center of the 4-cycle engine. Thereby, at least the first half of the operating angle (valve opening period) of the exhaust valve is positioned in the expansion stroke, and the temperature raising effect described in the above (5) and (6) can be obtained more effectively.

  (8) More preferably, the exhaust valve is advanced so that the exhaust valve opens only within the expansion stroke of the 4-cycle engine by the exhaust valve timing changing mechanism. As a result, the working gas in the combustion chamber that has been compressed and heated in the immediately preceding compression stroke is supplied to the exhaust passage without being substantially adiabatically expanded in the expansion stroke. Is obtained. Further, since the working gas compressed and heated in the subsequent compression stroke is supplied to the intake passage side in the subsequent intake stroke, the working gas does not substantially flow from the intake passage side to the exhaust passage side. Therefore, the temperature rise effect is further improved.

  (9) It has a battery 27 for supplying power to the crank drive device, and means (catalyst temperature sensor 31) for detecting the power or power amount of the battery 27, and according to the power or power amount of the battery 27 Thus, the advance angle width of the opening / closing timing of the exhaust valve in the temperature raising operation M1 is changed. Thus, by changing the advance angle width according to the power or the amount of power of the battery, the above-described temperature rise effect can be obtained without causing a shortage of power of the battery 27.

  (10) More preferably, supercharging by the supercharger 16 is performed during the temperature raising operation M1. By performing supercharging in this way, the development of negative pressure is suppressed, and the temperature drop of the working gas due to the negative pressure is suppressed, so that the above-described temperature rise effect can be further improved.

  (11) An intake valve timing changing mechanism 25 for changing the opening / closing timing of the intake valve is provided, and during the temperature raising operation M1, the intake valve opening timing is set by the intake valve timing changing mechanism 25 to the exhaust top dead center of the 4-cycle engine. More retard than. Thereby, the temperature rising effect of the intake system can be suppressed, and the temperature rising effect of the exhaust system can be relatively enhanced.

The system figure which shows the temperature rising apparatus of the engine which concerns on one Example of this invention. The flowchart which shows the flow of the temperature rising control of a present Example. The time chart which shows the flow of the said temperature rising control. The characteristic view which shows an example of the valve timing of the intake / exhaust valve which concerns on this invention. Explanatory drawing which shows the effect at the time of using a supercharger at the time of temperature rising operation. The flowchart in the case of changing the advance angle width of the exhaust valve opening / closing timing according to the amount of battery power. The characteristic view which shows the relationship between the battery electric energy and the conversion angle to the advance side of the exhaust valve opening / closing timing. Explanatory drawing in the case of estimating a catalyst temperature. A search table of estimated temperatures using the water temperature and outside air temperature as parameters. Coefficient search table with cranking speed as parameter. The characteristic view which shows the relationship between cranking rotation speed and a temperature rising effect. The characteristic view which shows the other example of the valve timing of the intake / exhaust valve which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Engine 13 ... Intake passage 15 ... Exhaust passage 16 ... Supercharger 17 ... Exhaust purification catalyst 18 ... Exhaust shutter valve 21 ... Fuel injection valve (fuel injection device)
23 ... Starter motor (crank drive)
24 ... Throttle valve 25 ... Intake valve timing change mechanism 26 ... Exhaust valve timing change mechanism 27 ... Battery 30 ... Engine control unit

Claims (11)

A crank driving device for rotationally driving the crankshaft;
An exhaust valve timing changing mechanism for changing the opening and closing timing of the exhaust valve;
A fuel injection device for injecting and supplying fuel to the combustion chamber or the intake passage,
While the fuel supply by the fuel injection device is stopped, the crankshaft is rotationally driven by the crank drive device so as to raise the temperature of the exhaust system including the exhaust passage, and the exhaust valve is opened and closed by the exhaust valve timing changing mechanism. A temperature raising device for an engine that performs a temperature raising operation for controlling the timing. A crank driving device for rotationally driving the crankshaft;
An exhaust valve timing changing mechanism for changing the opening and closing timing of the exhaust valve;
A fuel injection device that injects fuel into the combustion chamber or intake passage;
An exhaust purification catalyst disposed in the exhaust passage,
With the fuel supply by the fuel injection device stopped, the crankshaft is driven to rotate by the crank driving device so as to raise the temperature of the exhaust purification catalyst, and the opening / closing timing of the exhaust valve is adjusted by the exhaust valve timing changing mechanism. A temperature raising device for an engine that performs a temperature raising operation to be controlled.   The engine temperature increasing device according to claim 2, further comprising catalyst temperature detecting means for detecting a catalyst temperature of the exhaust purification catalyst, wherein the temperature increasing operation is performed until the catalyst temperature reaches a predetermined temperature.   The engine temperature increasing device according to claim 2 or 3, further comprising an exhaust shutter valve that closes an exhaust passage on a downstream side of the exhaust purification catalyst during the temperature increasing operation.   The engine temperature raising device according to any one of claims 1 to 4, wherein in the temperature raising operation, the exhaust valve timing changing mechanism advances the closing timing of the exhaust valve from the exhaust top dead center of the four-cycle engine.   6. The engine temperature increasing device according to claim 5, wherein, in the temperature increasing operation, the exhaust valve timing changing mechanism advances the opening timing of the exhaust valve from the expansion bottom dead center of the four-cycle engine.   The engine temperature increasing device according to any one of claims 1 to 6, wherein in the temperature increasing operation, the exhaust valve timing changing mechanism advances the operating angle center of the exhaust valve from the expansion bottom dead center of the 4-cycle engine.   The engine temperature raising device according to any one of claims 1 to 5, wherein, during the temperature raising operation, the exhaust valve timing change mechanism advances the exhaust valve so that it opens only within an expansion stroke of the four-cycle engine.   A battery for supplying electric power to the crank driving device; and means for detecting electric power or electric energy of the battery, and opening and closing of the exhaust valve in the heating operation according to the electric power or electric energy of the battery. The engine temperature raising device according to any one of claims 1 to 8, wherein the advance angle width of the time is changed.   The engine temperature raising apparatus according to any one of claims 1 to 9, wherein supercharging by a supercharger is performed during the temperature raising operation. It has an intake valve timing change mechanism that changes the opening and closing timing of the intake valve,
The engine temperature raising device according to any one of claims 1 to 10, wherein during the temperature raising operation, the intake valve timing changing mechanism retards the opening timing of the intake valve from the exhaust top dead center of the four-cycle engine.

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