JP2000213400A - Internal combustion engine having combustion type heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs by making a heat exchanger common in a case where a combustion type heater and an EGR device are provided, and improving space efficiency. SOLUTION: This internal combustion engine is provided with an exhaust gas recirculating passage 81 for returning exhaust gas discharged from an exhaust system 14 to an intake system 9 while detouring an internal combustion engine, and a combustion-type heater 22 so provided as to raise the temperature of an engine associated element by heat obtained by burning fuel. In this case, the exhaust gas recirculating passage is connected to the intake system through the combustion-type heater 22. The combustion-type heater 22 is provided with a combustion air introducing passage 31 for taking in fuel combustion air from the intake system, and a switching means 84 for selectively switching the exhaust gas recirculating passage 81 and the combustion air introducing passage 31. The combustion-type heater 22 is not operated but used as a cooling cooler when the exhaust gas recirculating passage 81 is selected by the switching means 84, while the combustion-type heater is used as an original heater when the combustion air introducing passage 31 is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine equipped with a combustion heater for raising the temperature of engine-related elements and a so-called EGR device for returning exhaust gas of the internal combustion engine to an intake system of the internal combustion engine to reduce NOx. .

[0002]

2. Description of the Related Art In recent years, internal combustion engines have high thermal efficiencies, such as direct injection engines and diesel engines, for example, and the amount of excess heat discharged is small. Therefore, a combustion type heater is provided separately from the internal combustion engine to heat engine-related elements such as a heater core when the engine is started.

On the other hand, it is known to provide an exhaust gas recirculation device (so-called EGR device) for returning exhaust gas from an exhaust system to an intake system for the purpose of reducing NOx in the exhaust gas.

[0004] As such an EGR device, for example, a device described in JP-A-7-317608 is known. This device has exhaust gas circulation passage cooling means for cooling the exhaust gas recirculation passage, and the exhaust gas is cooled by the cooling means before entering the intake system, so that the exhaust gas temperature at the time of entering the intake system is sufficient. Is low.

[0005]

When both the combustion type heater and the EGR device are provided, as a device for heat exchange, an exhaust gas circulation passage cooling means for cooling an exhaust gas recirculation passage, and a combustion type heater. Since the heater and the heater coexist, space efficiency and cost are disadvantageous.

The present invention has been made in view of the above points, and when a combustion type heater and an EGR device are provided, a heat exchanger necessary for both is shared, and space efficiency is improved.
It is an object to reduce costs.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention requires less control by an EGR device when it is necessary to operate a combustion type heater.
When it was necessary to return the exhaust gas to the intake system by the GR device, it was noted that there was little need to operate the combustion type heater.

In accordance with this aspect, the present invention has an intake system for introducing fresh air into the engine, and an exhaust system for discharging exhaust gas generated by combustion of fuel in the engine.
It has an exhaust recirculation passage that returns exhaust gas discharged from the exhaust system to the intake system bypassing the internal combustion engine, and is provided to raise the temperature of engine-related elements by heat obtained by burning fuel. The following means are employed in an internal combustion engine having a combustion type heater.

That is, the exhaust gas recirculation passage is connected to the intake system via a combustion type heater. On the other hand, the combustion type heater has a combustion air introduction passage for taking in fuel combustion air from an intake system. Further, a switching means for selectively switching between the exhaust gas recirculation passage and the combustion air introduction passage is provided.

When the combustion type heater is operated, the switching means selects the combustion air introduction path, and when returning the exhaust gas of the internal combustion engine to the intake system, the switching means selects the exhaust recirculation passage. Select When the exhaust gas recirculation passage is selected, the operation of the combustion heater stops. This allows
The combustion heater functions not as a heating device but as a cooling device. Therefore, the exhaust gas returned from the exhaust gas recirculation passage to the intake system is cooled by the combustion heater.

[0011] In order to use this heat exchange, it is preferable that the combustion type heater includes a heat exchanger for heating the cooling water of the internal combustion engine by heat generated by combustion. When the exhaust gas is introduced into the combustion heater without burning the combustion heater, the exhaust gas is cooled by the cooling water.

In order to perform the control according to the present invention, the present invention provides an operating state determining means for determining an operating state of an internal combustion engine, a switching control means for switching the switching means based on a determination result of the operating state determining means, It is preferable that the fuel cell system further includes a combustion heater control unit that controls operation / stop of the combustion heater in accordance with the determination result in the operation state. These are realized on a computer for controlling the internal combustion engine.

For example, the operating state determining means determines an operating state according to a cooling water temperature of the internal combustion engine. When the cooling water temperature is lower than a predetermined temperature, the switching control means controls the switching valve to connect the combustion air introduction passage to the switching valve. Command to select and
The combustion heater control means issues an operation command to the combustion heater, and when the coolant temperature is higher than a predetermined temperature, the switching control means instructs a switching valve to select the exhaust recirculation passage, and The combustion heater control unit issues a stop command to the combustion heater.

Here, the switching control can be performed according to the engine speed or the load, instead of the cooling water temperature. In the present invention, the term “internal combustion engine” refers to not only a normal port injection gasoline engine but also a gasoline direct injection lean burn engine, a diesel engine or CNG (compressed natural gas engine).
Also includes an internal combustion engine such as an engine in which the atmosphere in the exhaust system is excessive in oxygen and low in hydrocarbons and carbon monoxide, such as a compressed natural gas (AS) engine.

[0015] The combustion type heater is a heater attached to the internal combustion engine separately from the internal combustion engine main body, and performs its own combustion without being affected by the combustion in the cylinder of the internal combustion engine main body. It emits gas. Since it is necessary to raise the temperature of the engine-related elements before the engine is started, it is provided separately from the internal combustion engine body.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an internal combustion engine according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas purification device according to the present embodiment is applied. The internal combustion engine shown in FIG. 1 is a multi-cylinder water-cooled diesel engine.

The diesel engine has an engine body 1 having a water jacket containing engine cooling water, an intake device 2 for feeding air necessary for combustion into a plurality of cylinders of the engine body 1, and an exhaust gas after the air-fuel mixture has burned. It has an exhaust device 3 for releasing gas into the atmosphere, and a heater core 4 of a heating device for warming the interior of a vehicle equipped with an engine.

The intake device 2 includes an air cleaner 5 for filtering the intake air, an aero flow meter 5a for measuring a flow rate of the intake air passing through the air cleaner 5, a compressor 6a of a turbocharger 6 for feeding the intake air, and a compressor 6a. An intercooler 7 that cools intake air heated by heat generated when the air is compressed at 6a, and an intake manifold 8 that sends intake air that has passed through the intercooler 7 to each cylinder of the engine body 1. These are connected to each other by an intake pipe 9. Further, an intake throttle valve 11 is arranged between the intercooler 7 and the engine body 1.

The exhaust device 3 includes an exhaust manifold 12 connected to an exhaust port of the engine body 1,
The exhaust pipe 14 includes a turbine 6b of the turbocharger 6, an exhaust purification catalyst 13 for purifying exhaust gas, and a muffler (not shown) connected to the catalyst 13. In this example, the exhaust purification catalyst 13 includes a NOx catalyst 13a on the upstream side and an oxidation catalyst 13b on the downstream side. As the NOx catalyst, a selective reduction type lean NOx catalyst and a storage reduction type lean NOx catalyst can be exemplified.

The selective reduction type lean NOx catalyst refers to an oxygen-excess atmosphere (lean atmosphere) and a hydrocarbon (H
A catalyst that reduces or decomposes NOx in the presence of C), and examples thereof include a catalyst in which a transition metal such as Cu is ion-exchanged on zeolite and a catalyst in which a noble metal is supported on zeolite or alumina. Selective reduction type N
The Ox catalyst has a catalyst bed temperature within the catalyst purification window,
If the air-fuel ratio of the inflowing exhaust gas is lean, and HC, preferably HC whose molecular size has been reduced by thermal decomposition, is present in the exhaust gas, a part of the HC is partially oxidized to form active species. The generated active species react with NOx in the exhaust gas to reduce NOx to N ₂ , H ₂ O, CO _{2 and the} like.

The storage-reduction type lean NOx catalyst uses, for example, alumina as a carrier, and on the carrier, for example, an alkali metal such as potassium K, sodium Na, lithium Li or cesium Cs, or an alkaline earth such as barium Ba or calcium Ca. , Lanthanum La, and at least one selected from rare earths such as yttrium Y, and a noble metal such as platinum Pt. When the ratio of air and fuel (hydrocarbon) supplied to the engine intake passage and the exhaust passage upstream of the NOx catalyst is referred to as the air-fuel ratio of the exhaust gas flowing into the NOx catalyst, the NOx catalyst generates When the fuel ratio is lean, NOx is absorbed, and when the oxygen concentration in the inflowing exhaust gas decreases, the absorbed NOx is released.

The oxidizing catalyst oxidizes components of the reducing agent (fuel in the case of diesel) that are not consumed, that is, components such as HC and CO, which are added to the NOx catalyst, and discharges them as CO ₂ and water.

The selective reduction type lean NOx catalyst exhibits a purification ability when the catalyst bed temperature is within a predetermined temperature range (catalyst purification window). This point is due to the occlusion reduction type lean NOx catalyst and the oxidation catalyst. The same is true for

Further, the exhaust pipe 14 upstream of the catalyst 13
Above, the turbine 6b of the turbocharger 6 is provided. The turbine 6b is provided with a variable nozzle vane that controls the turbine speed by adjusting the flow of exhaust gas introduced into the turbine 6b. This variable nozzle vane converts the negative pressure from the vacuum pump 41 into an electric vacuum regulating valve (EVR).
V) It is variably controlled by adjusting at 42 and driving the actuator 44.

Next, the combustion type heater 22 will be described. As shown in FIG. 1, a branch pipe 31 for heater is provided, which branches off from an intake pipe 9 connecting the air cleaner 5 and the compressor 6a of the turbocharger 6, and is a combustion air introduction path. The combustion type heater 22 is connected to 31.

The combustion type heater 22 heats a heat medium (cooling water) with heat generated by burning fuel separately from the engine, and uses the heat medium as an engine-related element to form the heater core 4 or the engine body 1. And heat generated thereby heats these engine-related elements. Therefore, a heat medium circulation path is provided for circulating a heat medium (cooling water) from the combustion heater 22 via the heater core 4 and the water jacket of the engine body 1.

As such a heat medium circulation path, the combustion type heater 22 is provided with cooling water for the engine.
2 is connected to a cooling water discharge passage 33 that guides the cooling water heated in the combustion type heater 22 to the engine body 1 via the heater core 4.

Here, a specific configuration of the combustion type heater 22 will be described with reference to FIG. Inside the combustion type heater 22, a heater internal cooling water passage 22a communicating with a cooling water introduction passage 32 and a cooling water discharge passage 33 is formed for flowing cooling water from the water jacket.

The heater internal cooling water passage 22a is arranged so as to circulate around a combustion chamber 22d formed inside the combustion type heater 22, and cooling water flowing in the heater internal cooling water passage 22a is supplied from the combustion chamber 22d. The temperature rises due to the heat. That is, this part functions as a heat exchanger.

The combustion chamber 22d includes a combustion cylinder 22b as a combustion source for generating a flame, and a cylindrical partition wall 22c that covers the combustion cylinder 22b to prevent the flame from leaking to the outside. In this way, the combustion cylinder 22b is
By covering with c, the combustion chamber 22d is defined in the partition wall 22c. The partition wall 22c is covered by the outer wall 24 of the combustion type heater 22. The partition 22
An annular gap is provided between c and the outer wall 24, and this gap functions as the above-described heater internal cooling water passage 22a.

The combustion type heater 22 has an air supply port 22e.
And an exhaust outlet 22f, and the air supply port 22e and the exhaust outlet 22f communicate with the combustion chamber 22d. The heater branch pipe 31 is connected to the air supply port 22e for introducing the intake air.
2 f is connected to the intake pipe 9 via the combustion gas discharge pipe 51. Therefore, the combustion gas discharged from the exhaust outlet 22f is introduced into the intake pipe 9 and flows into the engine body 1.

Next, the exhaust pipe 14 branches off from the exhaust pipe 14 between the exhaust manifold 12 and the turbine 6 b of the turbocharger 6, is connected to the heater branch pipe 31, and the exhaust gas passes through the combustion type heater 22. An EGR pipe 81 is provided as an exhaust gas recirculation passage leading to the intake pipe.

At the connection point between the EGR pipe 81 and the branch pipe 31 for the heater, the intake air from the branch pipe 31 for the heater and the EGR pipe 8
An electromagnetic switching valve 84 is provided as switching means for selectively passing the exhaust gas from No. 1. This switching valve 84 is
Connected to the CU 18, and by a command from the ECU 18
The EGR pipe 81 and the heater branch pipe 31 are selectively switched.

The combustion gas discharge pipe 51 of the combustion type heater 22 is provided with an EGR control valve 83 for adjusting the flow rate of the exhaust gas sent from the EGR pipe 81. The EGR control valve 83 is driven by negative pressure from the vacuum pump 41 via an electric vacuum regulating valve (EVRV) 82. In addition, EGR
The location where the control valve 83 is provided may be a connection point between the combustion gas exhaust pipe 51 and the intake pipe 9.

The EVRV 82 is duty-controlled by the ECU 18 according to the operating condition of the engine, and varies the negative pressure from the vacuum pump 41 according to the duty ratio.
The negative pressure applied to the diaphragm chamber of the GR control valve 83 is controlled. The opening amount of the EGR control valve 83 changes depending on the magnitude of the negative pressure. The EGR control valve 83 is a flow control valve that controls the flow rate of the exhaust gas. The ECU 18 and the EVRV 82 constitute control valve adjusting means for adjusting the opening of the valve according to the operating state of the internal combustion engine.

When the EGR pipe 81 is selected by the switching valve 84, the combustion type heater is not operated. Thereby, the combustion chamber 22d formed inside the combustion type heater 22
Is cooled by cooling water flowing in the heater internal cooling water passage 22 a and sent to the intake pipe 9. That is, the combustion type heater 22 functions as a water-cooled cooler using the cooling water sent from the water jacket of the engine.

When the internal combustion engine is under a high load, it is preferable that the exhaust gas recirculated by the EGR control has a low temperature. This is because, when high-temperature exhaust gas is introduced into the intake system, the mass of the exhaust gas contained per unit volume is reduced and the volume efficiency is reduced. Therefore, to prevent this and improve the volumetric efficiency, the exhaust gas is cooled by a water-cooled cooler.

Further, the switching valve 84 is connected to the EGR pipe 81
And one at the connection point of the heater branch pipe 31 and the EG.
When the R pipe 81 and the heater branch pipe 31 are separately connected to the combustion type heater 22, respectively, the switching valve 8
4 and the EGR pipe 81 is selected when the EGR pipe 81 is selected.
Of the heater branch pipe 31 is opened.
Is closed. When the heater branch pipe 31 is selected, the reverse is performed.

Continuing the description of the combustion type heater 22, a fuel introduction passage 25 is connected to the combustion cylinder 22b, and a part of the fuel discharged from the fuel pump is supplied to the combustion cylinder 22b.
b. Further, the combustion cylinder 22
b, a vaporizing glow plug (not shown) for vaporizing the fuel supplied through the fuel introduction passage 25 and an ignition glow plug (not shown) for igniting the vaporized fuel
And are decorated. The vaporizing glow plug and the ignition glow plug may be shared by a single glow plug.

In the combustion type heater 22 configured as described above, the intake air flowing into the air supply port 22e from the heater branch pipe 31 is guided to the combustion chamber 22d and supplied to the combustion cylinder 22b by the fuel introduction passage 25. The fuel is vaporized by the vaporizing glow plug. Then, the intake air and the vaporized fuel are mixed to form an air-fuel mixture, and the air-fuel mixture is ignited by an ignition glow plug in the combustion chamber 22d and burns.

As shown in FIG. 3, the ECU 18 stores a cooling water temperature TH flowing through the water jacket of the internal combustion engine as shown in FIG.
W, engine speed NE, accelerator position Acc
p, parking brake PB and other signals are input,
The operating state determining means 91 for determining the operating state from the values of these signals, the switching control means 92 for switching the switching valve 84 in accordance with the determination result of the operating state determining means 91, and the control valve adjusting means 93 are realized on the ECU 18. Have been. Also,
The ECU 18 also includes a combustion heater control unit 94 that issues an operation command and an operation stop command to the combustion heater 22 based on the determination result of the operation state determination unit 91.

Next, an example of control of the internal combustion engine according to this embodiment will be described. The control routine shown in FIG. 4 is repeatedly executed at predetermined time intervals. First, in step S10, the coolant temperature TW is taken into the ECU 18, and in step S20, the operation state determination means determines whether or not the engine has just started from the coolant temperature from the coolant temperature. It is determined whether or not the vehicle is cold. Here, it is determined whether or not the cooling water temperature TW is higher than, for example, 50 ° C. When the cooling water temperature is, for example, 50 ° C. or lower, it is determined that the engine is in a cold state, and the process proceeds to S30, where the heater branch pipe 31 (passage) is selected by the switching valve 84 and the EGR control valve 83 is selected.
Is fully opened. At this time, the EGR pipe 81 (passage) is shut off by the switching valve 84.

At this time, since it is in the cold state, an operation command is issued to the combustion type heater 22, and the fuel is burned in the combustion type heater to heat the cooling water. The gas flows from the combustion gas exhaust pipe 51 to the EGR
The fresh air is supplied into the cylinder of the engine body 1 through the control valve 83 and the intake pipe 9. Therefore, the intake air is warmed to reduce HC in the combustion chamber.

If it is determined at S20 that the coolant temperature TW is higher than, for example, 50.degree.
Proceeding to 40, the EGR pipe 81 (passage) is selected by the switching valve 84, and the heater branch pipe 31 (passage) is shut off. Then, stop control of the combustion type heater 22 is performed,
The opening of the EGR control valve 83 is controlled.

As shown in FIG. 5, the control amount of the exhaust gas flow rate by controlling the opening of the EGR control valve 83 is calculated from an EGR duty map determined from the fuel injection amount and the engine speed. This is the same as that used for known EGR control. As a result, as shown in FIG.
When GRduty increases, the EVRV 82 opens greatly, the negative pressure applied to the control valve 83 also increases, and the EGR control valve 83 opens greatly, and the flow rate of exhaust gas, that is, EGR%
Becomes larger.

The EGR control valve 83 is opened when the internal combustion engine is in a medium to low load region such as at a low speed or a middle speed and the engine temperature rises, and the exhaust gas from the exhaust system to the intake system through the EGR pipe 81 is opened. return. Note that the EGR device does not operate during a high-load operation range or during deceleration. When the EGR control valve 83 is opened during high load operation, the exhaust pressure in the exhaust pipe 14 decreases,
This may cause the rotation of the turbine 6b to decrease or cause black smoke to be generated.

The control of the EGR control valve 83 is realized by the ECU 18 executing a routine as shown in FIG. This control routine is a routine that is repeatedly executed at predetermined time intervals.

First, initialization is performed in S101, and in S102
The engine speed NE, the temperature of the cooling water flowing through the internal combustion engine, and the like are taken into the ECU 18. Next, in S103, the fuel injection amount is taken into the ECU 18. further,
In S104, the control duty ratio of the EVRV 82 is determined from the two-dimensional map determined by the engine speed × the fuel injection amount. When the control duty ratio of the EVRV 82 is determined, the opening degree of the EGR control valve 83 is determined by controlling the EVRV 82 on the basis of the value, and therefore, S10
5, the EGR%, that is, the combustion gas ratio is determined.

When the EGR control should not be performed, the EGR control valve 83 is closed, and the exhaust gas from the exhaust outlet 22f is not introduced into the intake pipe 9.

[0050]

According to the present invention, the combustion type heater is provided with the EGR.
Since it can also be used as a cooler for cooling the exhaust gas in the control, the space efficiency of the device configuration can be increased, and the cost can be reduced because a dedicated cooling cooler is not required.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an internal combustion engine having a combustion heater according to the present invention.

FIG. 2 is a schematic sectional view of a combustion type heater.

FIG. 3 is a block diagram showing function realizing means realized on an ECU;

FIG. 4 is a diagram showing a control routine according to the embodiment;

FIG. 5 is an EGR duty map determined from a fuel injection amount and an engine speed.

FIG. 6 is a graph showing the relationship between EGR duty and EGR%.

FIG. 7 is a diagram showing an EGR control routine;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine body 2 ... Intake device 3 ... Exhaust device 4 ... Heater core 5 ... Air cleaner 6 ... Turbocharger 6a ... Compressor 6b ... Turbocharger turbine 7 ... Intercooler 8 ... Intake manifold 9 ... Intake pipe 11 ... Intake throttle valve 12 ... Exhaust manifold 13 Exhaust purification catalyst 13a NOx catalyst 13b Oxidation catalyst 14 Exhaust pipe 18 ECU 22a Heater internal cooling water passage 22b Combustion cylinder 22c Partition wall 22d Combustion chamber 22e Air supply port 22f Exhaust exhaust port 24 ... Outer wall 25 ... Fuel introduction passage 31 ... Branch for heater (combustion air introduction passage) 32 ... Cooling water introduction passage 33 ... Cooling water discharge passage 41 ... Vacuum pump 42 ... Electric vacuum regulating valve (EVRV) 44 ... Actuator 51: Combustion Gas exhaust pipe 81 EGR pipe (exhaust gas recirculation passage) 82 Electric vacuum regulating valve (EVRV) 83 EGR control valve 84 Switching valve (switching means) 91 Operating state determination means 92 Switching control means 93 Control valve adjusting means 94 ... combustion heater control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 31/06 F02N 17/06 A F02N 17/06 F02M 31/06 B

Claims (5)

[Claims] An internal combustion engine having an intake system for introducing fresh air into an engine and an exhaust system for discharging exhaust gas generated by combustion of fuel in the engine, and for discharging exhaust gas discharged from the exhaust system. An internal combustion engine having an exhaust recirculation passage returning to the intake system by bypassing, and further having a combustion type heater provided to raise the temperature of the engine-related elements by heat obtained by burning fuel. The exhaust recirculation passage is connected to the intake system via a combustion heater, and the combustion heater has a combustion air introduction passage for taking in fuel combustion air from the intake system. An internal combustion engine having a combustion heater, comprising switching means for selectively switching between a recirculation passage and a combustion air introduction passage. 2. When operating the combustion type heater, the switching means selects the combustion air introduction path, and when returning exhaust gas from the internal combustion engine to the intake system, the switching means selects an exhaust recirculation path. 2. The internal combustion engine having a combustion heater according to claim 1, wherein the operation is stopped and the operation of the combustion heater is stopped. 3. The internal combustion engine having a combustion heater according to claim 1, wherein the combustion heater includes a heat exchanger that heats the cooling water of the internal combustion engine with heat generated by combustion. 4. An operating state determining means for determining an operating state of the internal combustion engine, a switching control means for switching the switching means based on a result of the determination by the operating state determining means; An internal combustion engine having a combustion type heater according to any one of claims 1 to 3, further comprising a combustion type heater control means for controlling operation / stop of the type heater. 5. The operating state determining means determines an operating state according to a cooling water temperature of the internal combustion engine. When the cooling water temperature is lower than a predetermined temperature, the switching control means controls the switching valve to connect the combustion air introduction passage to the switching valve. And the combustion-type heater control means issues an operation command to the combustion-type heater, and when the cooling water temperature is higher than a predetermined temperature, the switching control means supplies a switching valve with the exhaust recirculation passage. The internal combustion engine having a combustion type heater according to claim 4, wherein the combustion type heater control means issues a stop command to the combustion type heater.