JP2008008223A - Exhaust gas temperature suppressing device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a turbo lag in a device for suppressing the temperature of exhaust gas of an internal combustion engine equipped with a turbo charger. <P>SOLUTION: A water injector 20 is installed for supplying water in an exhaust passage, to a further upstream side than the turbo charger 16, and water is injected under a predetermined condition. Rotation of the turbo charger 16 is promoted by expansion of the supplied water accompanying evaporation, and thereby, turbo lag can be suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for suppressing the exhaust temperature of an internal combustion engine equipped with a turbocharger, and more particularly to an apparatus that considers so-called turbo lag suppression.

  For the purpose of suppressing the exhaust temperature of an internal combustion engine, devices for injecting a liquid such as water into an exhaust system have been proposed (for example, Patent Document 1 and Patent Document 2). According to such an apparatus, the exhaust temperature can be suppressed by the latent heat of vaporization of the liquid. An apparatus in which a similar technique is applied to an internal combustion engine equipped with a turbocharger has also been proposed (Patent Document 3). In this apparatus, liquid is injected into the exhaust path downstream of the turbocharger.

JP 2003-83027 A JP 2004-300920 A JP-A-49-4015

  However, the apparatus of Patent Document 3 does not consider the problem of so-called turbo lag, which is a response delay of the turbocharger to the acceleration operation.

  Therefore, an object of the present invention is to suppress turbo lag in an apparatus for suppressing exhaust temperature of an internal combustion engine equipped with a turbocharger.

  The present invention relates to an exhaust temperature suppression device in an internal combustion engine having a turbocharger in an exhaust passage from a combustion chamber, and supplies liquid to the upstream side of the turbocharger in the combustion chamber or the exhaust passage. The liquid supply means is further provided.

  In the present invention, since the liquid supply means is disposed in the combustion chamber or the exhaust passage so as to supply the liquid upstream of the turbocharger, the rotation of the turbocharger is caused by the expansion accompanying the evaporation of the supplied liquid. Is promoted, thereby suppressing turbo lag.

  The liquid supply point by the liquid supply means can be selected at any position as long as it is in the combustion chamber or in the exhaust path and upstream of the turbocharger. However, the exhaust point of the internal combustion engine is particularly suitable. is there. When supplying liquid to the exhaust port of the internal combustion engine, the degree of freedom of supply is higher than when supplying liquid into the combustion chamber, and the exhaust temperature is higher than when supplying it into the exhaust pipe outside the exhaust port. Available.

  If the liquid is supplied toward the exhaust valve, the temperature of the exhaust valve can be suppressed, which is preferable.

  Moreover, you may further provide the control means which controls a liquid supply means. It is preferable that the control means controls the liquid supply means based on the acceleration request amount and / or the turbine rotation speed of the turbocharger. In this case, it is possible to perform flexible operation according to the acceleration request amount and the turbine rotational speed.

  Preferably, the control means causes the liquid supply means to supply the liquid when the acceleration request amount is larger than a predetermined reference acceleration request amount and the turbine rotational speed is smaller than the predetermined reference turbine rotational speed. . In this case, the desired effect of the present invention can be obtained with a simple configuration.

  The control means may gradually decrease the supply amount of the liquid as the turbine rotational speed increases. Further, the control means may gradually increase the supply amount of the liquid as the acceleration request amount is larger. In these cases, more flexible operation can be performed.

  An exhaust temperature raising means for raising the exhaust temperature during the liquid supply by the liquid supply means may be further provided. In this case, the vaporization of the liquid can be promoted by increasing the exhaust temperature, and the rotation of the turbine can be further promoted. Preferably, the exhaust gas temperature raising means is a retarding means for retarding the ignition timing from the normal ignition timing.

  A preferred embodiment of the present invention will be described below. In FIG. 1, an engine 1 according to an embodiment of the present invention is a port injection type four-cylinder gasoline internal combustion engine that injects fuel into an intake port, and only one cylinder is shown. A cylinder is formed inside the cylinder block 2, and a piston 3 is slidably inserted therein.

  The piston 3 is connected to a crankshaft (not shown) by a connecting rod (not shown). The cylinder head 4 is common to all cylinders, and an intake port 5 and an exhaust port 6 are formed in each cylinder, and an intake valve 7 and an exhaust valve 8 are connected via a valve spring (not shown). It is set. A spark plug 9 is provided on the top surface of the combustion chamber of the cylinder head 4.

  The camshaft that drives the intake and exhaust valves 7 and 8 is provided with a variable valve timing system (hereinafter referred to as VVT) 10. The VVT 10 is a mechanism for continuously changing the opening and closing timings of the intake and exhaust valves 7 and 8 by changing the rotation phase of the camshaft relative to the rotation of the crankshaft, and is driven by hydraulic pressure. The intake port 5 is provided with a fuel injection valve 12 for supplying fuel to the combustion chamber 11.

  An exhaust manifold 14 is connected to the exhaust port 6, and a turbocharger 16, a catalyst device 17, and a silencer 18 are provided in series in this order in the exhaust pipe downstream of the collection portion of the exhaust manifold 14. . The turbocharger 16 is well-known and performs supercharging by driving a compressor rotor (not shown) installed in the intake path by a turbine rotor (not shown) installed in the exhaust path. The catalyst device 17 includes, for example, a NOx storage reduction catalyst.

  The exhaust port 6 is provided with a water injector 20 for supplying water into the exhaust passage. The water injector 20 is a valve for atomizing the water supplied from the water tank 21 and pressurized by the water pump 22, and opens and closes by the action of a solenoid or a piezoelectric element. The water injector 20 is disposed toward the upstream side so as to inject water into the exhaust port 6 and toward the exhaust valve 8.

  Although not shown in detail, an electronic control unit (hereinafter referred to as an ECU) 30 stores a CPU that performs various arithmetic processes, a control program, a function, a ROM that stores reference values and initial values of each control variable, a control program and data. It is configured to include a temporary holding RAM, an input / output port, an A / D and D / A converter, a storage device, and the like.

  The ECU 30 receives output signals from various sensors. Such various sensors include a crank angle sensor 31 provided to face a part of a crankshaft (not shown), an accelerator pedal sensor 32 for detecting a depression amount of an accelerator pedal (not shown), and a turbine rotor of the turbocharger 16. The turbine rotation sensor 33 for detecting the rotation speed of the engine, the air flow meter 34 provided in the intake passage upstream of the intake port 5, the water temperature sensor 35 provided in the water jacket of the cylinder block 2, and the collective part of the exhaust manifold 14 An exhaust temperature sensor 36 is provided.

  The above-described VVT 10, fuel injection valve 12, water injector 20, water pump 22, throttle valve, and the like are controlled by a control signal from the ECU 30, and the discharge timing of the spark plug 9 is also determined. ing. The ECU 30 calculates the basic fuel injection amount based on detection signals from the air flow meter 34 and the crank angle sensor 31, and further corrects the basic injection amount based on detection signals from the water temperature sensor 35, the throttle opening sensor, and the like. Thus, the fuel injection amount per stroke is calculated.

  The operation of the present embodiment configured as described above will be described below. The processing routine of FIG. 2 is repeatedly executed by the ECU 30 at a predetermined timing according to the crank angle.

  In FIG. 2, first, the ECU 30 reads the detection values of the various sensors described above (S10). Next, the ECU 30 determines whether or not the current exhaust temperature detected by the exhaust temperature sensor 36 is greater than a predetermined high temperature reference value Ta (S20).

  If the exhaust temperature is higher than the high temperature reference value Ta, the water injection execution flag is set to 1 (S30), and the process is returned. The water injection execution flag is referred to in a water injection routine executed separately by the ECU 30. When the flag is set, the water injector 20 is driven by the ECU 30 and water is injected into the exhaust port 6. . The water injection execution flag is reset to 0 on condition that the water injection is completed.

  If negative in step S20, that is, if the exhaust gas temperature is equal to or lower than the high temperature reference value Ta, then the ECU 30 determines whether the requested acceleration amount is larger than a predetermined value and whether the turbine speed is smaller than the predetermined value. Determine (S40). A detected value of the accelerator pedal sensor 32 is used for the requested acceleration amount, and a detected value of the turbine rotation sensor 33 is used for the turbine rotation speed. If the requested acceleration amount is not large and / or the turbine speed is not small, the process proceeds to step S50, and the water injection execution flag described above is reset to zero. Therefore, in this case, water injection by the water injector 20 is not performed.

  If the determination in step S40 is affirmative, that is, if the requested acceleration amount is large and the turbine speed is small, the above-described water injection execution flag is set to 1 (S60), and the significant retard execution flag is set to 1. It is set (S70). This large retard execution flag is referred to in an ignition routine that is separately executed by the ECU 30, and when the flag is set, the ignition timing is delayed by the ECU 30 from the normal ignition timing (for example, cold Ignition is performed at a value set to 5 to 10 ° ATDC, which is the same value as the ignition timing used for warming up the catalyst at the start. The large retard flag is reset to 0 on the condition that the ignition ends. Therefore, in this case, water injection by the water injector 20 is executed, and ignition is executed at a timing that is greatly retarded, that is, delayed from the normal ignition timing.

  As a result of the above processing, in the present embodiment, when the exhaust temperature is higher than the high temperature reference value Ta (S20), water injection from the water injector 20 is executed (S30), so that the exhaust system is cooled. Is done. In the present embodiment, when the exhaust temperature is equal to or lower than the high temperature reference value Ta (S20), when the requested acceleration amount is larger than a predetermined value and the turbine rotational speed is smaller than the predetermined value (S40), Both water injection and large retardation are executed (S60, S70). When the retarding is performed significantly, so-called afterburning of unburned fuel in the exhaust passage is promoted, and the exhaust temperature can be raised. Therefore, the amount of heat required for water evaporation is ensured, and the rotation accompanying the evaporation of water promotes the rotation of the turbine rotor and suppresses the turbo lag. If the acceleration request amount is not large or the turbine rotational speed is not small in step S40, there is little need for turbo lag suppression, and the inconvenience is insignificant even without performing water injection (S50).

  As described above, in the present embodiment, since the water injector 20 is installed so as to supply water to the upstream side of the turbocharger 16 in the exhaust passage, the turbocharger is expanded by expansion accompanying evaporation of the supplied water. 16 rotation is promoted, and turbo lag is suppressed by this.

  The water supply point in the present invention can be selected at any position as long as it is in the combustion chamber 11 or in the exhaust path and upstream of the turbocharger 16. However, when supplying the fuel into the combustion chamber 11, the timing of water injection is limited to the exhaust stroke in consideration of the influence on the combustion temperature. On the other hand, when supplying into the exhaust port 6 / exhaust manifold 14 or the exhaust pipe, the timing of water injection may be any timing between the closing of the exhaust valve 8 and the opening of the next cycle. it can. That is, in the present embodiment, since water is supplied to the exhaust port 6, it can be said that the degree of freedom in supply timing is higher than that in the case where the water is supplied into the combustion chamber 11. Further, when water is supplied to the exhaust port 6 as in the present embodiment, there is an advantage that a higher exhaust temperature can be used than when the water is supplied to the exhaust manifold 14 and the exhaust pipe outside the exhaust port.

  Moreover, in this embodiment, since water was supplied toward the exhaust valve 8, the temperature of the exhaust valve 8 can be suppressed. Furthermore, in this embodiment, since it decided to inject water toward an upstream, vaporization of water can be accelerated | stimulated.

  In this embodiment, the ECU 30 for controlling the water injector 20 is further provided, and the water injector 20 is controlled based on the requested acceleration amount and the turbine rotational speed (S40 to S60). It is possible to perform flexible operation according to the situation.

  Further, in the present embodiment, when the requested acceleration amount is larger than the predetermined reference acceleration requested amount and the turbine rotational speed is smaller than the predetermined reference turbine rotational speed (S40), water is supplied to the water injector; Therefore (S60), the desired effect of the present invention can be obtained with a simple configuration.

  Further, in the present embodiment, since the exhaust temperature is further increased during the supply of the liquid by the liquid supply means, the rotation of the turbine is further promoted by the increase in the exhaust temperature even when the exhaust temperature is low. (S70).

  Next, a second embodiment of the present invention will be described. In the second embodiment, even if the temperature of the exhaust passage is lower than the high temperature reference value Ta, if the temperature is higher than a predetermined low temperature reference value Tb, the exhaust temperature is not increased. Note that the second embodiment differs only in the control processing as follows, and the mechanical configuration is the same as that of the first embodiment, and the description thereof will be omitted.

  The operation of the second embodiment will be described below. The processing routine of FIG. 3 is repeatedly executed by the ECU 30 at a predetermined timing according to the crank angle. The processes in steps S110 to S170 in the process routine of FIG. 3 are the same as those in steps S10 to S70 in the first embodiment (FIG. 2). In step S165, the exhaust temperature is compared with a predetermined low temperature reference value Tb. This low temperature reference value Tb is a value smaller than the above-described high temperature reference value Ta. If negative in step S165, that is, if the exhaust gas temperature is equal to or higher than the low temperature reference value Tb, the large retard execution flag is set to 1 as in the first embodiment (S170). On the other hand, if the determination in step S165 is affirmative, that is, if the exhaust gas temperature is lower than the low temperature reference value Tb, step S170 is skipped and the significant retard execution flag is not set.

  As a result of the above processing, in the second embodiment, when the exhaust temperature is not so high as to require cooling (when the exhaust temperature is lower than the high temperature reference value Ta), when the exhaust temperature is so low that the temperature needs to be raised (low temperature reference value Tb). Only in the following cases) the temperature is raised. Therefore, when the exhaust gas temperature is in the middle region between the reference values Ta and Tb, the temperature rise by the exhaust gas temperature raising means is suppressed, and the demerits associated with the temperature raising process, for example, the deterioration of fuel consumption in the case of a large delay angle, etc. are suppressed. Can do.

  In the above embodiments, the present invention has been described with a certain degree of concreteness, but various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that it is possible. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents. For example, in each of the above embodiments, the presence / absence of the water injection and the temperature increase process is determined in consideration of both the acceleration request amount and the turbine rotation speed, but either the acceleration request amount or the turbine rotation speed is considered. It is good as well.

  In each of the above embodiments, the water injection amount and the retardation amount are fixed values, but they may be set or corrected continuously or discretely. For example, a map (FIG. 4) that defines the relationship between the turbine rotational speed / required acceleration amount and the water injection amount and a map (FIG. 5) that defines the relationship between the water injection amount and the retardation amount are stored in advance in the ROM of the ECU. In addition, the water injection amount and the retard amount can be variably set by referring to both maps with the turbine rotation speed and the acceleration request amount. In this example, the liquid supply amount is gradually decreased as the turbine rotational speed is increased, and the liquid supply amount is gradually increased as the acceleration request amount is increased. The reason why the flat portions are provided in both maps is that there is an upper limit in the amount of retardation. In such a configuration, more flexible operation can be performed.

  In each of the above embodiments, the retard of the ignition timing is used as the exhaust temperature raising means, but other means can be adopted as the exhaust temperature raising means in the present invention. Examples of such other exhaust temperature raising means include [1] intake flow suppression control in an engine having a swirl control valve, and [2] in-cylinder injection ratio in an engine having a cylinder injection valve and a port injection valve. Increase control, [3] Unit time injection amount decrease control in an engine having an in-cylinder injection valve equipped with a variable valve lift amount mechanism and an injection hole diameter variable mechanism, and [4] Advance of injection timing in an engine having an in-cylinder injection valve There is angle control. These exhaust temperature raising means may be used alone or in combination of a plurality of types.

  [1] Intake air flow suppression control using a swirl control valve is achieved by reducing the speed of the intake air flow in the combustion chamber by fully opening the swirl control valve (or half-opening at a predetermined angle) to cause in-cylinder turbulence (swirl) The exhaust temperature is raised by weakening the flow) and promoting so-called afterburning of unburned fuel in the exhaust port.

  [2] In-cylinder injection ratio increase control increases the injection time of the in-cylinder injector by increasing the latter ratio of the injection amount in the operation using both the port injection valve and the in-cylinder injection valve. Then, the end of the injection time is delayed and the so-called afterburning of the unburned fuel in the exhaust port is promoted, thereby raising the exhaust temperature.

  [3] The unit time injection amount reduction control reduces the fuel injection amount per unit time of the in-cylinder injection valve and increases the injection time by reducing the valve lift amount of the in-cylinder injection valve and reducing the injection hole diameter. By delaying the end of the injection time and promoting the so-called afterburning of the unburned fuel in the exhaust port, the exhaust energy is increased by increasing the exhaust temperature.

  [4] The advance control of the injection timing of the in-cylinder injection valve is performed by adhering liquid-phase fuel to the top surface of the piston by making the injection timing of the in-cylinder injection valve close to the intake top dead center, and evaporating the fuel. Therefore, the so-called afterburning of the unburned fuel in the exhaust port is promoted to increase the exhaust energy.

  In each of the above embodiments, water is used as the liquid used for promoting the rotation of the turbine rotor. However, in the present invention, other liquids such as engine cooling water (LLC) or traveling fuel are used. Also good. In these cases, there is an advantage that the liquid mounted on the vehicle for other purposes can be used in the control according to the present invention. In addition, when using the fuel for driving | running | working as a medium of this invention, the combustion can be avoided by supplying in the state which oxygen amount was insufficient.

  Moreover, although each said embodiment demonstrated the example which applied this invention to the in-cylinder direct injection type 4 cycle gasoline engine, this invention is an engine etc. which use other liquid fuels, such as diesel fuel, and gaseous fuel as an energy source. The present invention can be applied to other types of internal combustion engines, and all belong to the category of the present invention.

It is a schematic structure figure showing a 1st embodiment of the present invention. It is a flowchart which shows the process example in 1st Embodiment. It is a flowchart which shows the process example in 2nd Embodiment. It is a graph which shows the setting of the water injection amount map in the modification of 1st, 2nd embodiment. It is a graph which shows the setting of the retardation amount map in the modification of 1st, 2nd embodiment.

Explanation of symbols

7 Intake valve 8 Exhaust valve 11 Combustion chamber 12 Fuel injection valve 14 Exhaust manifold 15 Exhaust pipe 16 Turbocharger 20 Water injector 21 Water tank 22 Water pump 30 ECU

Claims (11)

An exhaust temperature suppression device for an internal combustion engine having a turbocharger in an exhaust passage from a combustion chamber,
An exhaust temperature suppression device, further comprising liquid supply means for supplying liquid to the upstream side of the turbocharger in the combustion chamber or the exhaust passage. The exhaust temperature suppression device according to claim 1,
The exhaust temperature suppression device according to claim 1, wherein the liquid supply means supplies liquid to an exhaust port of the internal combustion engine. The exhaust temperature suppression device according to claim 2,
The exhaust temperature suppression device according to claim 1, wherein the liquid supply means supplies liquid toward an exhaust valve of the internal combustion engine. An exhaust temperature suppression device according to any one of claims 1 to 3,
An exhaust temperature suppression device further comprising control means for controlling the liquid supply means. An exhaust temperature suppression device according to claim 4,
The exhaust temperature suppression device according to claim 1, wherein the control means controls the liquid supply means based on an acceleration request amount. An exhaust temperature suppression device according to claim 4 or 5,
The exhaust temperature suppression device according to claim 1, wherein the control means controls the liquid supply means based on a turbine rotational speed of the turbocharger. An exhaust temperature suppression device according to claim 4,
The control means causes the liquid supply means to supply a liquid when the acceleration request amount is larger than a predetermined reference acceleration request amount and the turbine rotational speed is smaller than a predetermined reference turbine rotational speed. Exhaust temperature suppression device. An exhaust temperature suppression device according to any one of claims 4 to 7,
The exhaust temperature suppression device according to claim 1, wherein the control means gradually decreases the supply amount of the liquid as the turbine rotational speed increases. An exhaust temperature suppression device according to any one of claims 4 to 8,
The exhaust temperature suppression device according to claim 1, wherein the control means gradually increases the supply amount of the liquid as the acceleration request amount increases. An exhaust temperature suppression device according to any one of claims 1 to 9,
The exhaust temperature raising means for raising the exhaust temperature is further provided,
The exhaust temperature suppressing device is characterized in that the exhaust temperature raising means raises the exhaust temperature during the supply of the liquid by the liquid supply means. The exhaust gas temperature suppression device according to claim 10,
The exhaust temperature suppression device according to claim 1, wherein the exhaust temperature raising means is a retarding means for retarding the ignition timing with respect to the normal ignition timing.

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