JPH0749064A - Diesel engine - Google Patents

Abstract

PURPOSE:To reduce an amount of nitrogen oxides in exhaust gas without deteriorating fuel consumption performance of a diesel engine nor increasing an amount of black smoke in the exhaust gas. CONSTITUTION:A heat exchanger 21 through which cooling water of an engine 10 is circulated is provided, while fuel circulation to a coil-like pipe 24 of the heat exchanger 21 is changed over by means of a three-directional valve 23. A fuel temperature at an inlet side of a fuel injection pump 11 is detected by a temperature sensor 25, while the three-directional valve 23 is changed over by a controller 26. It is thus possible to keep the temperature of the fuel to be supplied to the fuel injection pump 11 within a proper range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine, and more particularly to a diesel engine in which fuel is pressurized by a fuel injection pump and injected into a cylinder.

[0002]

2. Description of the Related Art Generally, a diesel engine is equipped with a fuel injection pump. The fuel injection pump pressurizes fuel and supplies the pressurized fuel to a fuel injection nozzle through an injection pipe. I try to inject fuel. The spray of fuel injected from the injection port of the fuel injection nozzle is spontaneously ignited by the intake air that is pressurized and has a high temperature, and is combusted in the cylinder. The gas pressure associated with such combustion is taken out as rotational torque through the piston and the crankshaft.

[0003] Such a diesel engine causes a large amount of nitrogen oxides in its exhaust gas, which causes air pollution. Various measures have been tried to reduce nitrogen oxides. Conventional measures that have been taken conventionally include timing retard that delays the fuel injection timing, and EGR (Exhaust Gas Recircular) that returns a portion of the engine exhaust gas to the inside of the cylinder.
combustion, recirculation of exhaust gas) or cooling of intake air by an intercooler.

[0004]

According to the timing retard method, the combustion becomes slow and the combustion temperature lowers.
Although the amount of nitrogen oxides produced can be suppressed, the combustion state deteriorates, resulting in poor fuel economy and inclusion of black smoke in the exhaust gas. On the other hand, the EGR has the drawback that the exhaust gas is returned to the inside of the cylinder again, so that the wear of each part of the engine becomes remarkable and the lubricating oil deteriorates. Further, since intake air cooling uses an intercooler, it can be used only for an engine in which a turbocharger and an intercooler are combined, which is a drawback of lacking versatility.

An object of the present invention is to provide a diesel engine capable of effectively reducing nitrogen oxides in exhaust gas without deteriorating fuel economy and black smoke.

[0006]

In the course of research on diesel engines, the inventor of the present application reduced the ignition delay by supplying a fuel having an increased temperature to a fuel injection pump, which resulted in nitrogen oxidation in exhaust gas. We have found that it is possible to reduce the amount of objects (see FIG. 4). Generally, if the ignition delay is shortened, black smoke tends to increase, but when the temperature of the fuel is raised, the atomization of the spray becomes finer, mixing with air is promoted, and black smoke does not deteriorate. I found that.

The present invention has been made on the basis of such knowledge, and pressurizes fuel with a fuel injection pump,
In a diesel engine in which fuel is injected into a cylinder by a fuel injection nozzle and spontaneously ignited by heat of intake air, a heating means for heating the fuel pressurized by the fuel injection pump is provided. It concerns a diesel engine that does.

[0008]

The fuel heated by the heating means is supplied to the fuel injection pump, and the fuel is pressurized by the fuel injection pump. Then, the pressurized fuel is injected into the cylinder by the fuel injection nozzle, and is spontaneously ignited by the heat of intake air and burned. The increase in pressure at this time is taken out as an output through the piston.

[0009]

1 to 3 show a diesel engine according to a first embodiment of the present invention. A fuel injection pump 1 is provided on a side surface side of a cylinder block which constitutes the engine 10.
1 is attached. The discharge side portion of each pump unit of the fuel injection pump 11 is connected to the fuel injection nozzle 13 through an injection pipe 12. The fuel injection pump 11 is connected to the fuel tank 14.
Fuel is returned to the fuel tank 14 by a return pipe 15.

Further, the diesel engine 10 is equipped with a radiator 18 for cooling the diesel engine 10. The radiator 18 includes a cooling water pipe 19 for returning the cooling water from the engine 10 and a cooling water pipe 20 for sending the cooling water to the engine 10. And the radiator 18
The cooling water pipe 19 on the inlet side of the heat exchanger 21 and the three-way valve 22
It is designed to be connected via.

In the heat exchanger 21, the coiled pipe 2 is provided.
4 are arranged, and the fuel tank 14 is connected via the three-way valve 23.
It is designed to be connected with. Also coiled pipe 2
A temperature sensor 25 that detects the temperature on the outlet side of the No. 4 is provided, and the detection output of the temperature sensor 25 is input to the controller 26. The controller 26 controls opening / closing of the three-way valves 22 and 23.

In the structure described above, the fuel injection pump 11 sucks and pressurizes the fuel in the fuel tank 14, and pressurizes the fuel through the injection pipe 12 to the fuel injection nozzle 13.
Supply to. Therefore, the fuel injection nozzle 13 intermittently injects fuel at a predetermined timing. Fuel injection nozzle 1
The fuel spray injected from No. 3 is spontaneously ignited by the heat of the intake air compressed by the piston and burned in the cylinder at a predetermined timing. And the pressure due to combustion is taken out by the piston that slides in the cylinder,
It is converted into rotational motion by the crankshaft and extracted as rotational torque.

When the temperature of the fuel detected by the temperature sensor 25 is below a predetermined temperature, the three-way valves 22 and 23 are switched to the states shown in FIG. 1, and the cooling water for the engine 10 is three-way. The heat exchanger 21 enters through the valve 22 and returns to the radiator 18 via the heat exchanger 21. At this time, the three-way valve 23 is shown in FIG.
Since the fuel tank 14 is switched as shown in FIG.
The fuel inside is introduced into the coil-shaped pipe 24 of the heat exchanger 21 through the three-way valve 23, where it is heated by heat exchange and then supplied to the fuel injection pump 11.

When the fuel heated by the coiled pipe 24 of the heat exchanger 21 is supplied to the fuel injection pump 11,
The ignition delay is shortened, which makes it possible to reduce the amount of nitrogen oxides as shown in FIG. Further, generally, when the ignition delay is shortened, black smoke tends to increase, but in the case of this embodiment, the fuel spray is finely divided by heating, so that it is well mixed with air and the black smoke is deteriorated. Will not occur. Therefore, it is possible to reduce nitrogen oxides in the exhaust gas without deteriorating fuel efficiency and black smoke.

The temperature of the fuel supplied to the fuel injection pump 11 tends to decrease as the temperature increases, as is clear from the graph shown in FIG. 4, but generally 40 to 9
It is preferably within the range of 0 ° C. More preferably 5
It is in the range of 0 to 80 ° C.

The temperature supplied to the fuel injection pump 11 is detected by the temperature sensor 25 on the inlet side of the fuel injection pump 11. Therefore, when the temperature preset by the controller 26 is exceeded, the three-way valve 22 is switched as shown in FIG. Then, the cooling water of the engine 10 is returned to the radiator 18 without passing through the heat exchanger 21. Further, in order for the controller 26 to switch the three-way valve 23 as shown in FIG. 3, the fuel in the fuel tank 14 is supplied to the fuel injection nozzle 11 through the three-way valve 23.
The fuel stops flowing through the coiled pipe 24 of the heat exchanger 21. This prevents the temperature from rising more than necessary. As shown in FIGS. 2 and 3, the three-way valve 22,
When 23 is turned off and a while later, the temperature becomes equal to or lower than a predetermined temperature. Then, the controller 26 switches the three-way valves 22 and 23 again as shown in FIG. 1 to heat the fuel.

Next, a second embodiment will be described with reference to FIGS. In the second embodiment, not the cooling water of the engine 10 but the lubricating oil of the engine 10 accumulated in the oil pan 29 is used to heat the fuel. That is, the coiled pipe 24 is arranged in the oil pan 29, and the three-way valve 23 is connected between the fuel tank 14 and the coiled pipe 24.

The three-way valve 23 is turned on by the controller 26.
When switched to N, the fuel in the fuel tank 14 passes through the three-way valve 23 and is guided to the coiled pipe 24 in the oil pan 29, where it is heated and then guided to the fuel injection pump 11. .

When the temperature of the fuel at the inlet side portion of the fuel injection pump 11 is measured by the temperature sensor 25 and the temperature of the fuel rises above the control range,
The three-way valve 23 is turned off by the controller 26 as shown in FIG. Then, the fuel in the tank 14 is supplied to the fuel injection nozzle 13 through the three-way valve 23, and the heating of the fuel is stopped. In this way, the temperature of the fuel supplied to the fuel injection pump 11 is kept within the control range by switching the three-way valve 23 between ON and OFF by the controller 26 according to the temperature. Therefore, also in this embodiment, it is possible to achieve substantially the same operational effects as those of the first embodiment.

Next, a third embodiment will be described with reference to FIGS. 7 and 8. In this embodiment, the heat exchanger 21 is provided on the outer peripheral portion of the exhaust pipe 31 connected to the tip end portion of the exhaust manifold 30, and the heat exchanger 21 is provided.
The coiled pipe 24 is arranged so as to surround the outer peripheral portion of the exhaust pipe 31 inside. And the heat exchanger 21
A three-way valve 23 is connected between the fuel tank 14 and the fuel tank 14.

When the three-way valve 23 is turned on as shown in FIG. 7, the fuel sucked from the fuel tank 14 receives the three-way valve 23.
Then, it is guided to the coiled pipe 24 of the heat exchanger 21, heated by this heat exchanger 21, and then supplied to the fuel injection pump 11.

When the temperature of the fuel near the inlet of the fuel injection pump 11 is detected by the temperature sensor 25 and the detected temperature is higher than the control range, the three-way valve 23 is turned off. . Then the fuel tank 14
The fuel inside is supplied to the fuel injection pump 11 through the three-way valve 23, and the heating of the fuel is stopped. Therefore, the temperature sensor 25 and the controller 26 make it possible to keep the temperature supplied to the fuel injection pump 11 within an appropriate temperature range at all times, and thereby it is possible to achieve substantially the same effects as the above-described embodiment. .

Next, a fourth embodiment will be described with reference to FIGS. 9 and 10. In this embodiment, the fuel injection system itself is also used as the heating means, and three parts are provided in the middle of the return pipe 15 connected to the fuel injection pump 11 and the fuel injection nozzle 13, respectively. The valve 23 is connected, and fuel is supplied to the fuel tank 14 by the three-way valve 23.
The mode is switched between the mode for returning to the fuel injection mode and the mode for circulating the fuel injection pump 11.

When the temperature of the fuel detected by the temperature sensor 25 is lower than a predetermined value, the three-way valve 23 is turned on as shown in FIG.
The fuel is returned to the fuel injection pump 11 immediately by switching the fuel in the return pipe 15 as shown in FIG.
By such switching, the fuel temperature gradually rises. When the temperature detected by the temperature sensor 25 exceeds a predetermined value, the controller 26
The one-way valve 23 is switched as shown in FIG. 10 so that the fuel in the return pipe 15 is returned to the fuel tank 14 to prevent an excessive temperature rise. When the temperature drops, the 3-way valve 23 is switched again as shown in FIG. By such an operation, it becomes possible to keep the temperature of the fuel supplied to the fuel injection pump 11 within a predetermined temperature range at all times.
It is possible to obtain the same effect as that of the embodiment.

Although the present invention has been described with reference to the first to fourth embodiments, the present invention is not limited to these embodiments and various modifications can be made. For example, the structure may be obtained by appropriately combining the above four embodiments.

[0026]

As described above, the present invention is provided with the heating means for heating the fuel pressurized by the fuel injection pump. Therefore, it becomes possible to supply the fuel whose temperature has been raised to the fuel injection pump, which shortens the ignition delay and reduces the nitrogen oxides. Generally, when the ignition delay is shortened, black smoke tends to increase, but in the case of the present invention, the atomization of atomization is caused by the heating of the fuel, so that the mixing with air is promoted and black The smoke does not worsen. Further, this makes it possible to reduce the nitrogen oxides in the exhaust gas without deteriorating the fuel consumption and the black smoke.

[Brief description of drawings]

FIG. 1 is a piping diagram showing a diesel engine of a first embodiment.

FIG. 2 is a piping diagram showing switching of a three-way valve.

FIG. 3 is a piping diagram showing switching of a three-way valve.

FIG. 4 is a graph showing the amount of nitrogen oxide in exhaust gas with respect to fuel temperature.

FIG. 5 is a piping diagram of a diesel engine of a second embodiment.

FIG. 6 is a piping diagram showing switching of a three-way valve.

FIG. 7 is a piping diagram of a diesel engine of a third embodiment.

FIG. 8 is a piping diagram showing switching of a three-way valve.

FIG. 9 is a piping diagram of a diesel engine of a fourth embodiment.

FIG. 10 is a piping diagram showing switching of a three-way valve.

[Explanation of symbols]

 10 Diesel engine 11 Fuel injection pump 12 Injection pipe 13 Fuel injection nozzle 14 Fuel tank 15 Return pipe 18 Radiator 19, 20 Cooling water piping 21 Heat exchanger 22, 23 3-way valve 24 Coiled pipe 25 Temperature sensor 26 Controller 29 Oil pan 30 Exhaust manifold 31 Exhaust pipe

Claims (1)

[Claims] 1. A diesel engine in which fuel is pressurized by a fuel injection pump, fuel is injected into a cylinder by a fuel injection nozzle and spontaneously ignited by heat of intake air, and the fuel is pressurized by the fuel injection pump. A diesel engine having a heating means for heating a diesel engine.