JP4412104B2 - Diesel engine system and cooling method for diesel engine system - Google Patents

Description

  The present invention relates to a diesel engine system provided with a supercharger, and more particularly to a diesel engine system employing a so-called eco-run system that performs automatic stop and automatic start.

  Generally, a diesel engine (hereinafter simply referred to as an engine) includes a supercharger. A supercharger is a device that supplies a large amount of intake air to an engine by rotating a turbine with exhaust gas and driving a compressor. Since this supercharger is exposed to high-temperature exhaust, the supercharger itself and surrounding exhaust system parts become hot. Therefore, if the engine is stopped in a high temperature state, the lubricating oil pump (not shown) driven by the engine is also stopped. For this reason, the lubricating oil supplied to the supercharger is heated and carbonized (also referred to as coking), causing serious damage to the system including the engine. Therefore, when the vehicle is traveling at a high load and the temperature of the turbocharger is equal to or higher than the predetermined temperature, the temperature of the turbocharger is lowered by performing sufficient idling without immediately stopping the engine. Is prevented from occurring.

  By the way, from the viewpoint of improving fuel efficiency and reducing exhaust gas in recent years, the engine is automatically stopped when the vehicle is idle for more than a predetermined time due to waiting for traffic lights or loading and unloading of luggage, and further, the driver can operate the clutch. Attention has been focused on a system for automatically starting the engine (hereinafter simply referred to as “eco-run”). However, if the eco-run is simply applied to an engine equipped with a supercharger, the above-mentioned problem occurs because the engine is automatically stopped when the supercharger needs to be cooled. Therefore, Patent Document 1 proposes a technique for dealing with this.

  Patent Document 1 proposes an automatic engine stop device that can protect a turbocharger even when an eco-run is employed. This automatic stop device detects the temperature of the supercharger and prohibits the automatic stop of the engine when the detected temperature exceeds a predetermined value. That is, this automatic stop device protects the supercharger by prohibiting the automatic stop of the engine by eco-run when the temperature of the supercharger exceeds a predetermined value.

  Furthermore, Patent Document 2 proposes a technique that has improved the problems of the automatic stop device of Patent Document 1 described above. The automatic stop device of Patent Document 1 temporarily prohibits the start of eco-run when the supercharger is hot, but the engine automatically stops because the eco-run starts when the temperature of the supercharger decreases. Therefore, the engine is automatically stopped at a timing later than usual. If the engine stop timing deviates in this way, the passenger will feel uncomfortable. Therefore, the control device of Patent Document 2 is configured so that the engine does not stop unexpectedly even when the temperature of the supercharger decreases, so that the passenger does not feel uncomfortable.

Japanese Patent Laid-Open No. 9-42003 JP 2002-276411 A

  In the devices proposed in Patent Document 1 and Patent Document 2, the engine is stopped after sufficient idle operation is performed to cool the turbocharger. In particular, in the case of the device of Patent Document 2, the stop timing is adjusted so that the passenger does not feel uncomfortable, so that it takes more time to stop the engine.

  However, in the first place, one of the purposes of adopting eco-run is to improve fuel efficiency as described above. Delaying the engine stop timing for cooling the turbocharger causes a deterioration in fuel consumption, so that the merit of adopting the eco-run is diminished.

  Therefore, the objective of this invention is providing the diesel engine system corresponding to an eco-run which can suppress the situation where a fuel consumption deteriorates in order to cool a supercharger.

In order to achieve the above object, the present invention provides a diesel engine equipped with a supercharger, further comprising a fuel injection valve upstream of a turbine of the supercharger disposed in an exhaust passage , wherein the temperature of the supercharger is predetermined. When the automatic stop condition of the diesel engine is satisfied from the operating state of the diesel engine at a temperature or higher, the fuel injection valve is driven to supply fuel upstream of the turbine when the diesel engine is automatically stopped. A diesel engine system for cooling the supercharger. With this configuration, it is not necessary to maintain the diesel engine in an idle state for cooling the supercharger, so that the engine can be quickly stopped when the automatic stop condition by the eco-run is satisfied. Therefore, this diesel engine system can reliably suppress a situation in which the fuel consumption deteriorates due to cooling of the supercharger.

Temperature estimation means for estimating the temperature of the supercharger, addition amount calculation means for calculating the required addition amount of the fuel based on the temperature estimated by the temperature estimation means, and the addition amount calculation means Corresponding to the required addition amount, the fuel injection valve can be configured to control the fuel injection valve so that the required addition amount is injected once or a plurality of times. In this case, the means may be configured to drive the fuel injection valve so that the initial injection amount becomes larger than the subsequent injection amount when the required addition amount is injected in a plurality of times. The diesel engine system drives the fuel injection valve when a rotational speed detection means for detecting the rotational speed of the diesel engine and the rotational speed detected by the rotational speed detection means are within a predetermined range. And a means for controlling to inject the fuel and supply the fuel to the supercharger. In the diesel engine system configured as described above, the fuel injection valve may be a fuel addition valve used for maintaining the function of a filter for purifying exhaust gas in an exhaust passage of the diesel engine.

Furthermore, the object is a cooling method of a system including a supercharger and a diesel engine having an automatic stop and automatic start mechanism, and the operation of the diesel engine in which the temperature of the supercharger is equal to or higher than a predetermined temperature. When the automatic stop condition of the diesel engine is satisfied from the state, the fuel injection valve provided upstream of the turbine of the supercharger disposed in the exhaust passage is driven when the diesel engine is automatically stopped. It can also be achieved by a cooling method of a diesel engine system that cools the supercharger by supplying it upstream of the turbine. In this configuration, when the fuel injection amount is larger than a predetermined amount, the fuel is injected in a plurality of times, and the initial injection amount is made larger than the subsequent injection amount.

  According to the present invention, since the supercharger can be cooled by the cooling means, it is possible to suppress a situation in which the timing of the engine automatic stop by the eco-run is delayed. Therefore, it can suppress that a fuel consumption deteriorates with the diesel engine for eco-runs provided with a supercharger.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a system of a diesel engine 11 (hereinafter simply referred to as an engine 11) mounted on a vehicle. The engine 11 is a four-cylinder engine having four cylinders 12-1 to 12-4. From the left in FIG. 1, there are a first cylinder 12-1, a second cylinder 12-2, a second cylinder 12-2, and a fourth cylinder 12-4. Each cylinder 12 is provided with injectors 13-1 to 13-4 for fuel injection. Fuel is supplied to each injector 13-1 to 13-4 via a common rail 14 from a fuel injection pump 9 connected to a fuel tank (not shown).

  The engine 11 is provided with an intake manifold (intake manifold) 20. The intake manifold 20 is connected downstream of the intake passage 21. The intake air TA introduced into the intake passage 21 is first supplied to the intake manifold 20 via the air filter 22, the compressor 23 a of the supercharger 23, and the intercooler 24. A throttle valve 8 is disposed in the intake passage 2 downstream from the intercooler 24.

  Further, an exhaust manifold (exhaust manifold) 30 that collects the exhaust gas EG after combustion is disposed on the opposite side of the intake manifold 20 of the engine 11. The exhaust manifold 30 is connected to an exhaust passage 31 for releasing exhaust gas outside the apparatus. The exhaust passage 31 is connected to an exhaust purification filter 33 for exhaust gas purification via the turbine 23b side of the supercharger 23. A catalyst 34 is supported on the exhaust purification filter 33. An exhaust pipe 35 for discharging the purified exhaust gas EG is connected to the downstream side of the exhaust purification filter 33.

  Further, in the exhaust manifold 30, an exhaust gas circulation passage 41 of an exhaust gas recirculation device 40 (hereinafter simply referred to as an EGR device 40) that recirculates part of the exhaust gas to the intake side to reduce nitrogen oxides (NOx). (Hereinafter referred to as EGR passage 41) is connected. The EGR passage 41 connects the exhaust manifold 30 and the intake passage 21 downstream from the throttle valve 8. In the EGR passage 41, an EGR cooler 42 for cooling the EGR gas (exhaust gas) exiting the exhaust manifold 30 and an EGR valve 43 for adjusting the amount of EGR gas recirculated to the intake passage 21 are arranged. An EGR device 40 is formed including the EGR passage 41, the EGR cooler 42, and the EGR valve 43.

  FIG. 2 is an enlarged view of a part of FIG. 1 for explaining a more detailed configuration around the exhaust manifold 30 and the supercharger 23. FIG. 2 shows a liquid ejecting nozzle 4 serving as a liquid ejecting unit (not shown in FIG. 1). The liquid ejecting nozzle 4 is disposed so that the ejection port (ejection port) from which the liquid is ejected faces the inside of the exhaust manifold 30. The liquid injection nozzle 4 injects a liquid for cooling the supercharger 23 into the exhaust manifold 30. When the liquid ejected from the liquid ejecting nozzle 4 reaches the high-temperature supercharger 23 through the exhaust passage 31, it is vaporized. The supercharger 23 is cooled by the latent heat of vaporization during the vaporization.

  The liquid injection nozzle 4 can be disposed in an internal space when the exhaust manifold 30 and the supercharger 23 are connected, but the injected liquid is directed toward the supercharger 23 as shown in FIG. It is desirable to install around the connection part 30a of the exhaust manifold 30 to which the exhaust passage 31 is connected so that it can flow easily. As described above, the EGR passage 41 is also connected to the exhaust manifold 30. It is desirable that the liquid from the injection nozzle 4 is not mixed into the EGR gas recirculated to the intake TA side. Therefore, as shown in the figure, the connection portion 30a for the exhaust passage 31 and the connection portion 30b for the EGR passage 41 provided in the exhaust manifold 30 ensure a distance that the liquid from the liquid injection nozzle 4 does not enter the EGR passage 41. It is good to arrange.

  By the way, an occlusion reduction type NOx catalyst or a catalyst having an oxidation function can be adopted as the catalyst 34 carried by the exhaust gas purification filter 33 disposed in the exhaust passage 31 downstream of the turbine 23b of the supercharger 23. When such a catalyst is used, the stored NOx is released and reduced, the SOx poisoning is recovered, the particulates collected in the filter are oxidized and removed (collectively, maintaining the filter function) It is necessary to maintain the catalytic action. A reducing agent is supplied to the catalyst for maintaining the function of the filter. As a technique for supplying the reducing agent to the catalyst, there is a technique for injecting fuel from the upstream side of the catalyst. When this technology is employed, fuel can be supplied as a reducing agent from the same position as the position where the liquid injection nozzle 4 shown in FIG. 2 is disposed.

  Therefore, when the fuel injection nozzle (fuel addition valve) is provided in the engine system of the present embodiment for the filter function maintenance process, this fuel injection nozzle can be used (also used as the liquid injection nozzle 4). Further, if fuel is used as the liquid used for cooling the supercharger 23, the configuration can be used as it is for cooling the supercharger in order to maintain the filter function. A fuel control valve 51 is connected to the fuel injection pump 9, and the liquid injection nozzle 4 is connected to the fuel control valve 51. The fuel control valve 51 is controlled by the ECU 1 similarly to the fuel injection pump 9. The ECU 1 controls the amount of fuel to be injected from the liquid injection nozzle 4 and the number of injections.

  In addition, about the liquid injected from the liquid injection nozzle 4, things other than fuel, for example, water, are employable. A liquid that is vaporized by the heat of the supercharger 23 and that does not adversely affect the system and exhaust gas can be selected and used as appropriate.

  Further, the liquid injection nozzle 4 may be provided separately from the fuel injection nozzle. For example, the liquid injection nozzle 4a shown as a modified example by a dotted line is arranged such that the injection port faces the exhaust passage 31, and the liquid is directly sprayed to the turbine 23b of the supercharger 23.

  Further, the liquid ejecting nozzle 4 may eject liquid from the outside of the supercharger 23. In this regard, the liquid jet nozzle 4b is indicated by a dotted line as another modification of the liquid jet nozzle 4. The liquid ejecting nozzle 4 b is configured to spray liquid to the outside of the supercharger 23. As the liquid ejected from the liquid ejecting nozzle 4b, window washer liquid or water can be used. FIG. 2 illustrates the case where the window washer fluid 52 is used. In this case, the pump 53 that discharges the window washer fluid 52 may be driven and controlled by the ECU 1.

  With reference to FIG. 1 again, the electrical configuration of the system formed around the engine 11 will be described. Since the eco-run is applied to this system, a configuration for executing the eco-run is included. In the present specification, a configuration for performing an eco-run will be referred to as an idle stop mechanism. This system is entirely controlled by the ECU 1 (electronic control unit). In order to detect the state of the engine 11 at the periphery of the engine 11, a water temperature sensor 2 for detecting the temperature of the engine cooling water, a crank angle sensor 3 for detecting the rotation angle of the crankshaft, and an exhaust temperature for detecting the temperature of the exhaust gas. A sensor 37 and a filter temperature sensor 36 for detecting the outlet temperature of the exhaust purification filter 33 are installed. In addition, a brake switch 5b interlocked with the brake pedal 5a, a vehicle speed sensor 6, and an idle switch 7b interlocked with the accelerator pedal 7a are arranged to confirm the operation state of the vehicle. Detection signals from the plurality of sensors and switches are supplied to the ECU 1. The system also includes a throttle valve 8 whose drive is controlled by the ECU 1, a fuel injection pump 9, an engine starter 15, and a battery 16 that drives the engine starter 15.

  The ECU 1 confirms the driving state of the engine from a plurality of sensors and switches, and starts eco-run control of the engine 11 when predetermined conditions are met. A state when the idle stop mechanism is driven by the ECU 1 will be described later.

  The ECU 1 is mainly configured by a microcomputer, and an internal ROM 1a stores an engine automatic stop program and an engine automatic start program that constitute an engine idle stop mechanism. Furthermore, when the engine automatic stop condition is satisfied from the engine operating state where the temperature of the supercharger is equal to or higher than the predetermined temperature, such as when the vehicle stops after traveling at a high load, the liquid injection nozzle 4 is driven. A supercharger cooling program for injecting liquid is stored. This supercharger cooling program is started in association with the idling stop mechanism being driven.

  Here, conditions for driving the idle stop mechanism (hereinafter referred to as eco-run start conditions) will be described. The engine automatic stop program that constitutes the idle stop mechanism is as follows: (1) The engine is warmed up and not overheated (the engine coolant water temperature Tw is lower than the water temperature upper limit value Twmax and the water temperature lower limit value) Higher than the value Twmin), (2) the accelerator pedal 7a is not depressed (idle switch 7b, on), (3) the charge amount of the battery 16 is equal to or higher than the reference voltage, and (4) the brake pedal 3a is depressed. It is set to automatically stop the engine on condition that the state (brake switch 5b, on) and (5) the vehicle is stopped.

The ECU 1 executes control based on the automatic stop program from when the engine 11 is started. Further, after the engine 11 is stopped, the ECU 1 starts control by the automatic start program for the engine 11. If any one of the automatic stop conditions (1) to (5) is not satisfied, the ECU 1 starts engine start control. When engine start control is started, the ECU 1 starts control based on the fuel injection amount change program. The ECU 1 issues a command to the engine starter 15 to drive the engine starter 15, and issues a command to the throttle valve 8 to open the throttle valve 8. Further, the ECU 1 instructs the fuel injection pump 9 to inject fuel. The injection amount at this time is an initial fuel injection amount Q ₀ , and this initial fuel injection amount Q ₀ is read from a rewritable memory in the ECU 1.

  FIG. 3 is a flowchart showing a supercharger cooling routine executed by the ECU 1. The ECU 1 checks whether or not the eco-run automatic stop condition is satisfied (S101). The automatic stop condition is as described above. When the ECU 1 confirms that the eco-run condition is satisfied, the ECU 1 estimates the temperature Ttb of the supercharger 23. The ECU 1 estimates the temperature Ttb of the supercharger 23 based on the signal from the filter temperature sensor 36 disposed downstream of the purification filter, the exhaust temperature sensor 37 disposed in the exhaust passage 31, the operating condition history, and the like (S102). The operating condition history is data that can confirm the load state of the engine 11 and includes various information that can estimate the temperature state of the supercharger 23. Of course, such information on the operating condition history may be stored in a rewritable memory in the ECU 1.

  In the next step 103, the ECU 1 compares the temperature Ttb of the supercharger 23 estimated in step 102 with a predetermined value (predetermined temperature) (S103). In step 103, it is confirmed whether the temperature of the supercharger 23 has decreased to a temperature at which the engine 11 may be automatically stopped. Therefore, the predetermined value here is set based on a temperature that may damage the system if the engine 11 is stopped immediately. If the ECU 1 determines that the temperature Ttb of the supercharger 23 is lower than the predetermined value, there is no possibility that the system will fail. Therefore, the ECU 1 stops the processing by this routine, and drives the idle stop mechanism as usual to automatically stop the engine 11.

  On the other hand, when the ECU 1 determines in step 103 that the temperature Ttb of the supercharger 23 is higher than a predetermined value, it is assumed that the system will fail if the engine 11 is immediately stopped. Therefore, the ECU 1 starts preparations for cooling the supercharger 23. Here, a case where fuel is used as the liquid to be injected for cooling the supercharger 23 is illustrated.

  The ECU 1 calculates the required fuel addition amount Qtb from the temperature Ttb of the supercharger 23 (S104). As for the required addition amount Qtb calculated here, for example, the ECU 1 measures the correlation between the supercharger temperature Ttb and the required addition amount Qtb in advance and stores the calculation table prepared based on this measurement in the ROM 1a. Read and use.

  Next, the ECU 1 checks whether or not the rotational speed of the engine 11 is within a predetermined range based on the signal from the crank angle sensor 3 (S105). That is, the ECU 1 performs fuel injection after confirming that the engine speed is within a range in which the injected fuel is reliably supplied to the supercharger 23. By attaching such a condition, the fuel injected for cooling surely reaches the supercharger 23.

  Further, the ECU 1 checks whether or not the required fuel addition amount Qtb calculated in step 104 is larger than a predetermined amount (S106). When the required addition amount Qtb is equal to or greater than a predetermined amount, efficient cooling can be performed by injecting the fuel in a plurality of times rather than injecting a large amount of fuel at a time. Therefore, when the required addition amount Qtb is less than the predetermined amount, the ECU 1 performs fuel injection by driving the liquid injection nozzle 4 once (S107), and the processing by this routine is ended. On the other hand, when the required addition amount Qtb is equal to or greater than the predetermined amount, the ECU 1 drives the liquid injection nozzle 4 a plurality of times to inject fuel a plurality of times (S108), and the processing by this routine is terminated.

  Note that the predetermined amount used as a reference in step 106 for single injection or multiple injections is based on data obtained by performing a test of injecting fuel and cooling the supercharger. You just have to decide. Also, it is possible to measure how many times it is effective to perform the injection when the predetermined amount is exceeded, and create a table of the required addition amount Qtb and the number of times and store it in the ROM 1a in advance. Good.

  In addition, when fuel is injected in a plurality of times, the turbocharger is the one that maximizes the initial injection amount, rather than simply dividing the required addition amount Qtb by the number of times and injecting equally. 23 can be efficiently cooled. For the second and subsequent injections, the injection amount may be reduced in order or may be equal. Such a data table may also be stored in the ROM 1a. In step 106, the required addition amount Qtb is compared with a predetermined value to determine the number of injections. However, the number of injections may be set in advance according to the required addition amount Qtb. For example, the number of injections may be set in advance, such as one injection when the required addition amount Qtb is within a predetermined range, and two injections when the required addition amount Qtb is outside the predetermined range. Further, the first and second and subsequent injection amounts when the number of injections is plural may be set in advance. Thus, if the number of injections and the injection amount are set in advance according to the necessary addition amount Qtb, it is not necessary to perform the comparison process in step 106. A table may be created for such data and stored in the ROM 1a in advance.

  Since the system of the engine 11 described above can forcibly cool the supercharger 23 by injecting liquid when the condition of the engine automatic stop condition is satisfied from a state where the supercharger 23 is at a high temperature, It is not necessary to maintain the idle state until the supercharger 23 cools as in the conventional device. Therefore, this system can suppress deterioration in fuel consumption due to cooling of the supercharger 23. Moreover, since the cooling by the liquid injection of the supercharger 23 is completed in a short time, the engine 11 can be stopped immediately after satisfying the automatic stop condition by the eco-run.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

It is the block diagram which showed the system of the diesel engine 11 in the state mounted in the vehicle. FIG. 2 is an enlarged view of a part of FIG. 1 for explaining a more detailed configuration around an exhaust manifold and a supercharger. It is the flowchart which showed the routine of the supercharger cooling performed on the assumption that the idle stop mechanism is driven.

Explanation of symbols

1 ECU (control means)
1a ROM
3 Crank angle sensor (rotation speed detection means)
4 Liquid injection nozzle (liquid injection means)
DESCRIPTION OF SYMBOLS 11 Diesel engine 23 Supercharger 34 Exhaust purification filter 36 Filter temperature sensor 37 Exhaust temperature sensor

Claims (7)

In a diesel engine with a supercharger,
A fuel injection valve is provided upstream of the turbine of the supercharger disposed in the exhaust passage, and the automatic stop condition of the diesel engine is established from the operating state of the diesel engine where the temperature of the supercharger is equal to or higher than a predetermined temperature. Sometimes, the diesel engine system cools the supercharger by driving the fuel injection valve and supplying fuel upstream of the turbine when the diesel engine is automatically stopped. Temperature estimating means for estimating the temperature of the supercharger;
An addition amount calculation means for calculating a required addition amount of the fuel based on the temperature estimated by the temperature estimation means;
The fuel injection valve is controlled so as to inject the required addition amount once or a plurality of times corresponding to the required addition amount calculated by the addition amount calculating means. The diesel engine system according to claim 1. 3. The fuel injection valve according to claim 2, wherein the means drives the fuel injection valve so that an initial injection amount is larger than a subsequent injection amount when the required addition amount is injected in a plurality of times. Diesel engine system. A rotational speed detection means for detecting the rotational speed of the diesel engine;
Means for driving the fuel injection valve to inject the fuel and supplying the fuel to the supercharger when the rotation speed detected by the rotation speed detection means is within a predetermined range; The diesel engine system according to any one of claims 1 to 3, wherein 5. The diesel engine according to claim 1, wherein the fuel injection valve is a fuel addition valve used for maintaining a function of an exhaust purification filter in an exhaust passage of the diesel engine. system. A cooling method for a system including a supercharger and a diesel engine equipped with a mechanism for automatic stop and automatic start,
The turbocharger disposed in the exhaust passage when the diesel engine is automatically stopped when an automatic stop condition of the diesel engine is satisfied from an operating state of the diesel engine where the temperature of the turbocharger is equal to or higher than a predetermined temperature. A method for cooling a diesel engine system, wherein the turbocharger is cooled by driving a fuel injection valve provided upstream of the turbine and supplying fuel upstream of the turbine. The method for cooling a diesel engine system according to claim 6, wherein when the fuel injection amount exceeds a predetermined amount, the fuel is injected in a plurality of times, and the initial injection amount is made larger than the subsequent injection amount. .

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