JPH11200851A - Diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diesel engine formed in a manner that it can sufficiently heat exhaust gas when the engine is decelerated. SOLUTION: An electric heating catalyst(EHC) 5 is connected to one output terminal of an EHC control SW9, and the other output terminal of the EHC control SW9 is connected to a battery 10. The input terminal of the EHC 5 is connected to an alternator 11. The alternator 11 is driven by an engine, and adjusted, for example, to 12 V when the output thereof is supplied to the battery 10, and adjusted, for example, to 30 V when the output thereof is supplied to the EHC5. When the deceleration of the engine is detected, an electronic control device (ECU) 12 outputs a changeover control signal to the EHC control SW9 so as to change over the output of the alternator 11 from the battery 10 side to the EHC5 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine configured to maintain good exhaust gas purifying action of a catalyst.

[0002]

2. Description of the Related Art As is well known, a catalyst provided in an exhaust passage of an engine plays a role of purifying exhaust gas. Efficiency decreases. Low-temperature exhaust gas appears remarkably especially when the engine load is reduced. Therefore, conventionally, a device has been devised to raise the temperature of the low-temperature exhaust gas before the exhaust gas flows into the catalyst according to the load state of the engine.

[0003] For example, Japanese Utility Model Publication No. 5-1615 discloses a technique in which an electric heater is arranged at an inlet of a catalyst and on / off control of the electric heater is performed according to a load state of an engine. This technology raises the temperature of exhaust gas by heating an electric heater so that a catalytic action can be sufficiently performed.

[0004]

As a problem inherent in a diesel engine, when the engine decelerates, the exhaust temperature decreases.
As a result, there is a problem that the purification efficiency of the catalyst decreases. This is because the diesel engine has no throttle,
Or, even if it has, since the intake is not throttled as much as a gasoline engine, a large amount of air flows as exhaust gas through the catalyst. Such a large amount of low-temperature exhaust gas at the time of deceleration cannot be sufficiently coped with a conventional heating method of an electric heater.

Accordingly, it is an object of the present invention to provide a diesel engine configured to be able to satisfactorily heat exhaust gas when the engine is decelerated.

[0006]

The above object is achieved by providing an electrically heated catalyst in an exhaust passage on the exhaust input side of the catalyst so as to apply the output of the alternator to the electrically heated catalyst when the diesel engine is decelerated. .

The alternator normally supplies, for example, 12 V to the battery, but can supply, for example, 30 V to the electric heating catalyst by controlling the field of the field coil. According to the present invention, at the time of deceleration, the electric power of the electric heating catalyst is not supplied from the battery but from the alternator, so that the exhaust gas flowing into the catalyst is heated well.

Further, at the time of deceleration, it is also possible to adjust the intake air regulator provided in the intake passage to reduce intake air and reduce fuel injection.
Effective for heating exhaust gas. This is because the exhaust gas from the engine is reduced, so that the exhaust gas is efficiently heated by the electric heating catalyst.

[0009]

FIG. 1 is a schematic view of a diesel engine having an electrically heated catalyst in an exhaust passage. As shown in the figure, an engine body 1 is connected to an air cleaner (A / C) 3 via an intake passage 2 and an exhaust passage 4.
Through an electric heating catalyst (EHC) 5 and a catalyst 6. A turbocharger 7 is provided between the intake passage 2 and the exhaust passage 4. The intake passage 2 is provided with a throttle 8 as an intake regulator.

At the time of engine acceleration, high-temperature exhaust gas discharged from the engine body 1 passes through the exhaust passage 4 to the EHC.
5 and the catalyst 6. At this time, since the exhaust gas has a sufficiently high temperature, it is not necessary to supply electricity to the EHC 5. The high-temperature exhaust gas is efficiently purified by the catalyst 6 and discharged to the outside. On the other hand, at the time of deceleration, the temperature of the exhaust gas from the engine body 1 decreases, so that the EHC 5 is energized. At this time, the intake is reduced by adjusting the throttle 8 as necessary, and the fuel injection is stopped. This is effective not only in reducing the exhaust gas but also in heating the exhaust gas by the EHC 5. Less than,
The method of energizing the EHC 5 will be described in detail.

FIG. 2 shows an embodiment of an electric system provided in the diesel engine according to the present invention. As shown, the EHC 5 is connected to one output terminal of the EHC control SW 9, and the battery 10 is connected to the other output terminal of the SW 9. The output terminal B of the alternator 11 is connected to the input terminal of the EHC 5. The alternator 11 is driven by an engine, and its output is adjusted to, for example, 12 V when supplied to the battery 10, and the EH
When supplied to C5, for example, it is adjusted to 30V. The method of adjusting the supply voltage will be described later.

The EHC control SW 9 switches the output of the alternator 11 to the EHC 5 or the battery 10 according to a control signal from an electronic control unit (ECU) 12.
As shown in the figure, the ECU 12 determines the condition of the accelerator SW, the vehicle speed,
Signals such as the engine speed, cooling water temperature, and battery voltage VA are input, and various control signals are output based on these signals. One of them is a switching control signal to the EHC control SW 9, and the other is a throttle 8 and an injector 1.
The control signal for adjustment is output to 3.

Next, the operation of this embodiment will be described with reference to FIG. First, the ignition SW 14 is turned on to start the engine. At the same time, the opening / closing SW 15 is turned on, and a field current flows from the battery 10 to the field coil 16 using the IC regulator 17. As a result, the alternator 10 starts power generation with the rotation of the engine, and an output is obtained from the stator coil 18 via the rectifier circuit 19. At this time, the control SW 9 is turned on on the battery 10 side, and the electric energy generated by the alternator 11 is stored in the battery 10 as the engine is accelerated. When the engine enters a deceleration state in such a situation, the ECU 12 detects this and outputs a control signal to cope with the low temperature of the exhaust gas.

FIG. 3 is a diagram showing a control flow of the ECU 12. First, it is detected whether or not the accelerator SW is off. In the case of NO (ON), the process goes to the return in the figure. YE
In the case of S (off), it is detected whether the vehicle speed is 0 or more.
If NO (less than 0), go to return. If YES (0 or more), it is detected whether or not the engine speed is equal to or more than idle. If NO (less than idle), go to return. If YES (idle or higher), it is determined that the engine has been decelerated, and the ECU 12 outputs a control signal for switching the control SW 9 so that the EHC 5 is energized. Also, if necessary, prior to energizing the EHC 5, a command is issued to close the throttle 8 and stop fuel injection.

FIGS. 4A and 4B are time charts showing the energization timing of the EHC 5. FIG. 4A shows a control signal from the ECU 12, FIG. 4B shows a field current, and FIG. 4C shows a state of the EHC control SW9. It is. First, time t
Normal power generation control is performed up to 1 and, for example, 1
A voltage of 2 V is output. EC under these circumstances
When detecting the deceleration of the engine according to the above control flow, U12 outputs a switching control signal to the control SW9 at time t1. At the same time, the field current of the field coil 17 is reduced and adjusted by the IC regulator 18,
At time t2, the power generation of the alternator 11 stops. Thereafter, at time t3, the control SW 9
It is switched to the HC5 side. At time t4, the field current of the field coil 17 is increased and adjusted by the IC regulator 18 this time, and the alternator 11 starts generating power.
Then, from time t5, full excitation is performed, and a voltage of, for example, about 30 V is output from the alternator 11 to the EHC 5 via the control SW9. When the switching control signal is turned off at time t6, the field coil 17
The field current of the alternator 1 is adjusted to decrease at time t7.
The power generation of 1 stops. Then, at time t8, control S
W9 is switched from the EHC 5 side to the battery 10 side. At time t9, the field current of the field coil 17 is adjusted to increase again, and the alternator 11 starts to generate power.
The current field current is adjusted so that a normal 12 V is output at time t10. Here, the reason why the power generation of the alternator 11 is stopped during the switching operation of the control SW 9 is to protect the relay contact of the control SW 9.

As described above, according to the present invention, it is possible to suppress the temperature decrease of the exhaust gas generated at the time of deceleration with a simple configuration.
In addition, since the catalyst can be maintained in a sufficiently activated state even during deceleration due to heating by the EHC, deterioration of exhaust gas can be prevented even during acceleration after deceleration.

[0017]

According to the present invention, it is possible to obtain a diesel engine capable of satisfactorily heating exhaust gas when the engine is decelerated.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a diesel engine having an electric heating catalyst in an exhaust passage.

FIG. 2 is a diagram showing an embodiment of an electric system provided in the diesel engine of the present invention.

FIG. 3 is a diagram showing a control flow of an electronic control unit.

4A shows a control signal from an ECU, FIG. 4B shows a field current, and FIG. 4C shows a state of an EHC control switch.

[Explanation of symbols]

 Reference Signs List 5 electric heating catalyst (EHC) 9 EHC control SW 10 battery 11 alternator 12 electronic control unit (ECU) 17 field coil 18 IC regulator 19 stator coil 20 rectifier circuit

Claims (1)

[Claims] 1. A catalyst provided in an exhaust passage of an engine, an electric heating catalyst provided in an exhaust passage on an exhaust input side of the catalyst, an alternator driven by the engine, and an alternator driven by the engine during deceleration of the engine. A connection circuit for providing an output to the electrically heated catalyst.