JP2002161811A - Fuel system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably provide an atomizing function of a liquid fuel. SOLUTION: A throttle part 12 is provided in a fuel feeding pipe 7 ranging from a fuel tank 8 to a booster pump 6, and a feeding pipe 13 for a fluid to be mixed extended from a tank 9 for the fluid to be mixed is opened inside the throttle part 12. When the liquid fuel passes through the throttle part 12, the fluid to be mixed is lead into the fuel feeding pipe 7 by a decompressing effect generated around the throttle part and a mixture is formed. The mixture is pressurized by the booster pump 6 and it is heated by a heater 43. As a result, the fluid to be mixed contained in the mixture becomes a supercritical state. Then the mixture of the liquid fuel and the fluid to be mixed in the supercritical state is injected from an injection valve 2. The fluid to be mixed is maintained in a liquid state from the tank 9 for the fluid to be mixed to the booster pump 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art A liquid fuel is supplied from a fuel tank into a mixing chamber using a fuel pump, and a mixed fluid different from the liquid fuel is supplied from the mixed fluid tank into the mixing chamber using a mixed fluid pump. A mixture of the liquid fuel and the fluid to be mixed is formed, the pressure and temperature in the mixing chamber are made higher than the critical pressure and the critical temperature of the fluid to be mixed, and the fluid to be mixed in the mixture is brought into a supercritical state. 2. Description of the Related Art An internal combustion engine in which a body is injected from an injection valve is known.
No. 651974).

[0003] As will be described in detail later, this makes it possible to promote the atomization of the liquid fuel, and thus to ensure good combustion.

[0004]

By the way, considering the volume of the fluid tank to be mixed, it is preferable that the fluid to be mixed is stored in the fluid tank to be mixed in a liquid form rather than a gas. However, if the liquid to be mixed is vaporized before being mixed with the liquid fuel or before being brought into a supercritical state even after being mixed, the gas to be mixed is separated from the liquid fuel, As a result, there is a problem that the liquid fuel and the fluid to be mixed cannot be uniformly mixed. If they cannot be mixed uniformly, there is a possibility that the liquid fuel cannot be finely atomized.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel supply device for an internal combustion engine which can stably obtain an atomizing action of liquid fuel.

[0006]

According to a first aspect of the present invention, there is provided a fuel passage for supplying liquid fuel from a fuel tank to an injection valve. A fluid passage to be supplied from the fluid mixture tank is connected at the connection portion, thereby forming a mixture in which the fluid to be mixed is mixed with the liquid fuel, and a supercritical fluid disposed in the fuel passage downstream of the connection portion. A fuel injection device for an internal combustion engine in which a fluid to be mixed in the mixture is brought into a supercritical state by a state generating means, and the mixture is injected from an injection valve. The stored fluid to be mixed is supplied to the supercritical state generating means while maintaining the liquid. That is, according to the first aspect, since the fluid to be mixed is maintained in a liquid state, a stable atomization action of the liquid fuel is ensured.

According to a second aspect, in the first aspect, the pressure in the mixed fluid passage and the fuel passage from the mixed fluid tank to the supercritical state generating means so that the mixed fluid is maintained in a liquid state. Alternatively, the temperature is controlled. According to the third invention, in the second invention, a pump for fuel pressure delivery is arranged in the fuel passage upstream of the connection portion, and the discharge pressure of the pump is set higher than the vaporization pressure of the fluid to be mixed. That is, in the third aspect, the discharge pressure of the pump is set so that the fluid to be mixed is maintained as a liquid.

According to a fourth aspect, in the first aspect, a control valve capable of controlling a valve opening ratio is disposed in the mixed fluid passage, and the valve opening ratio of the control valve is determined based on an engine operating state. I try to control. That is, in the fourth invention,
The mixing ratio is changed based on the engine operating state.
It is common for a substance to be in a supercritical state when the pressure of the substance is higher than its critical pressure and the temperature of the substance is higher than its critical temperature. However, the supercritical state referred to herein includes the case where the pressure and temperature of a substance are slightly lower than its critical pressure and critical temperature.

[0009]

FIG. 1 shows a case where the present invention is applied to a vehicle diesel engine. However, the present invention can also be applied to a spark ignition gasoline engine or an internal combustion engine not for vehicles. Referring to FIG. 1, the engine body 1 includes a plurality of, for example, four cylinders 1 a, and each of the cylinders 1 a includes, for example, an electromagnetic injection valve 2. These injection valves 2 are connected via respective distribution pipes 3 to a common mixture volume or common rail 4 for these injection valves 2. The common rail 4 is connected via a high-pressure pipe 5 to a discharge side of, for example, an engine-driven type pressurizable pump 6 capable of controlling a discharge pressure, and a suction side of the pressure pump 6 is connected to a fuel tank 8 via a fuel supply pipe 7. Connected to. The fuel tank 8 contains liquid fuel, in this embodiment light oil.

On the other hand, a fluid to be mixed, which is different from fuel, is contained in a fluid to be mixed tank (cylinder) 9 in a liquid form. As the fluid to be mixed, for example, water, carbon dioxide, hydrogen,
At least one selected from alcohols and hydrocarbons such as methane and ethane can be used. A mixed fluid supply pipe 10 extends from the mixed fluid tank 9, and an outflow end thereof is connected to the fuel supply pipe 7. Next, the connection portion will be described.

Referring to FIG. 1 and FIG. 2, a fuel supply pipe 7 has an upstream pipe 7a extending from a fuel tank 8, a downstream pipe 7b extending from a pressurizing pump 6, and connecting the upstream pipe 7a and the downstream pipe 7b to each other. And a fluid supply pipe 10 to be mixed is connected to the connection pipe 7c. More specifically, the connection pipe 7c includes an upstream pipe 7a and a downstream pipe 7b.
A fuel passage 11 is formed to communicate with each other, and a throttle portion 12 is formed in the fuel passage 11. Further, in the connection pipe 7c, the fuel passage 1 in the throttle portion 12 is provided.
1, a fluid passage 13 to be mixed is formed, and this fluid passage 13 is communicated with the supply pipe 10 for fluid to be mixed. That is,
The outflow end of the mixed fluid passage 13 is opened in the fuel passage 11 at the throttle portion 12.

Referring to FIG. 3 showing a partially enlarged view of the outflow end of the fluid passage to be mixed, a porous body 14 is attached to the outflow end. The porous body 14 can be formed of, for example, ceramic. However, the porous body 14 can also be formed of a metal plate having a large number of pores, or a woven or non-woven cloth made of metal fibers or ceramic fibers. Referring again to FIG. 1, an electromagnetic control valve 15 capable of controlling a valve opening ratio by controlling, for example, a duty ratio is arranged in the mixed fluid supply pipe 10. In addition, a feed pump 16 of, for example, an electric type capable of controlling the discharge pressure is disposed in the fuel supply pipe 7 between the connection portion and the fuel tank 8, that is, in the upstream pipe 7a. The feed pump 16 supplies the fuel in the fuel tank 8 to the pressurizing pump 6.

An electronic control unit (ECU) 30 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 32, R
AM (random access memory) 33, CPU (microprocessor) 34, BR constantly connected to power supply
An AM (backup RAM) 35, an input port 36, and an output port 37 are provided. A pressure sensor 38 for generating an output voltage proportional to the pressure in the common rail 4 is attached to the common rail 4. Further, a load sensor 39 for generating an output voltage indicating an engine load such as an intake air amount and an accelerator pedal depression amount is provided. The output voltages of these sensors 38 and 39 correspond to the corresponding ADs, respectively.
The data is input to the input port 36 via the converter 40. Further, a rotation speed sensor 41 that generates an output pulse indicating the engine rotation speed is connected to the input port 36.

On the other hand, the output port 37 is connected to the injection valve 2, the pressurizing pump 6, the control valve 15, and the feed pump 16 via the corresponding drive circuits 42, respectively. Further, a temperature controller 43 for controlling the temperature of the mixture in the common rail 4 is attached to the common rail 4. The temperature control device 43 includes, for example, an electric heater as a heating device, and is connected to the output port 37 via a corresponding drive circuit 42.

When the pressurizing pump 6 and the feed pump 16 are operated, the liquid fuel in the fuel tank 8 flows through the fuel supply pipe 7 toward the pressurizing pump 6. As a result, the fluid to be mixed in the fluid to be mixed tank 9 is reduced by the depressurizing action generated around the throttle portion 12 so that the fluid to be mixed 10
Through the fuel passage 11. Accordingly, a mixture in which the fluid to be mixed is mixed is formed in the liquid fuel, and the mixture then goes to the pressure pump 6.

Here, the flow rate of the fluid to be mixed flowing into the fuel passage 11 increases as the pressure reducing action or the pressure drop acting on the outflow end of the mixed fluid passage 13 increases. Increases as the flow rate of the liquid fuel flowing through the fuel cell increases. Therefore, in the present embodiment, if the valve opening ratio of the control valve 15 is constant, the mixing ratio, which is the amount of the fluid to be mixed with respect to the amount of the liquid fuel, can be maintained substantially constant.

At this time, the fluid to be mixed is a porous material 14.
After flowing through the fine pores, the fuel flows into the fuel passage 11. As a result, the fluid to be mixed flows into the liquid fuel stream in the form of droplets. As a result, the liquid fuel and the fluid to be mixed can be uniformly mixed. The mixture thus formed is then pressurized by a pressure pump 6 and flows into the common rail 4. The discharge pressure of the pressurizing pump 6 is controlled so that the pressure in the common rail 4 is maintained at a pressure P1 higher than the critical pressure PC of the fluid to be mixed, and the output of the heater 43 is the temperature of the mixture in the common rail 4 Is preset so as to be maintained at a temperature T1 higher than the critical temperature TC of the fluid to be mixed. That is, in the common rail 4, the mixture is exposed to a supercritical state generating environment that brings the fluid to be mixed into a supercritical state. As a result, the fluid to be mixed is brought into a supercritical state in the common rail 4, that is, the mixture is formed from the liquid fuel and the fluid to be mixed in the supercritical state.

Here, the above-described supercritical state generating environment is formed by the pressurizing pump 6 and the heater 43. Therefore, it can be seen that the pressure pump 6 and the heater 43 form a supercritical state generating device. This mixture is then supplied to the injector 2 via a distribution line 3 and then injected from the injector 2 into the engine combustion chamber. By doing so, atomization of the liquid fuel can be promoted, and therefore, good combustion can be ensured.

The mechanism of the atomization promoting action in this case is not necessarily clarified. However, it is believed that this mechanism can be explained as follows. That is, the molecules of the fluid to be mixed can move much more freely in the supercritical state than in the liquid state. Therefore, the mixed fluid molecules easily enter between the liquid fuel molecules, thereby reducing the surface tension of the liquid fuel. As a result, the liquid fuel cannot form large size droplets after being injected, ie, forms small size droplets. In this way, atomization is promoted.

According to this mechanism, the atomization promoting action depends on the mixing ratio of the fluid to be mixed to the liquid fuel. That is, as the mixing ratio increases, the effect of promoting atomization increases. Therefore, if the mixing ratio fluctuates, the atomization promoting action fluctuates, which is not preferable. On the other hand, in the present embodiment, the mixing ratio is maintained substantially constant as long as the opening ratio of the control valve 15 is constant as described above. Therefore, a stable atomization promoting action can be obtained.

On the other hand, as described at the beginning, if the fluid to be mixed is vaporized (evaporated) before being mixed with the liquid fuel or before being brought into a supercritical state even after being mixed, the liquid fuel And the fluid to be mixed cannot be uniformly mixed. Even if the mixed fluid molecules in the supercritical state can move freely, it is difficult to obtain a good atomization promoting action with such a heterogeneous mixture.

Further, when the fluid to be mixed is vaporized, its volume becomes large, so that it becomes difficult to supply a sufficient amount of the fluid to be mixed. Therefore, in the present embodiment, the mixed fluid tank 9
The fluid to be mixed is maintained in a liquid state from the pressure to the pressure pump 6. Specifically, first, the mixed fluid supply pipe 1 extending from the mixed fluid tank 9 to the pressurizing pump 6
0 and the temperature inside the fuel supply pipe 7 is the critical temperature T of the fluid to be mixed.
It is kept lower than C. This is because if the temperature is higher than the critical temperature TC, the fluid to be mixed cannot become liquid, no matter how high the pressure. In the embodiment of FIG. 1, since the temperature of the fluid to be mixed never exceeds the critical temperature TC, no temperature control device or cooling device for the fluid to be mixed is provided. However, this temperature control device or cooling device can be provided as needed.

Further, at least the pressure of the fluid to be mixed from the fluid tank 9 to the pressurizing pump 6 is maintained higher than the vaporization pressure (liquefaction pressure) determined by the temperature of the fluid to be mixed. That is, in this embodiment, the discharge pressure of the feed pump 16 is set higher than the vaporization pressure of the fluid to be mixed. With this configuration, the pressure in the fuel supply pipe 7 from the feed pump 16 to the pressurizing pump 6 and the pressure in the mixed fluid supply pipe 10 can be maintained higher than the vaporization pressure of the mixed fluid.
Therefore, it is possible to prevent the fluid to be mixed from being vaporized.

However, strictly speaking, in the present embodiment, the fluid to be mixed is supplied by using the pressure reducing action acting on the outflow end of the to-be-mixed fluid passage 13, so that the pressure at this outflow end also increases The discharge pressure of the feed pump 16 is set so as to be higher than the vaporization pressure. Not only the fluid to be mixed but also the liquid fuel may be in a supercritical state. However, considering the above mechanism, the atomization promoting action can be ensured if only the fluid to be mixed is brought into the supercritical state. In addition, it is not preferable that both are in a supercritical state from the viewpoint of energy consumption.

Therefore, in this embodiment, a mixture of the fuel not in the supercritical state and the fluid to be mixed in the supercritical state is formed, and this mixture is injected. In other words, the pressure and the temperature in the common rail 4 are set so that the fluid to be mixed is in a supercritical state but the liquid fuel is not in a supercritical state. To enable this, the fluid to be mixed must satisfy the following conditions. That is, at least one of the critical pressure and the critical temperature of the fluid to be mixed must be smaller than the corresponding value of the liquid fuel.

Next, a method of controlling the duty ratio D of the control valve 15 will be described with reference to FIG. As can be seen from FIG. 4, the engine load L is equal to the predetermined first set load L.
During normal operation that is higher than 1 and lower than the second set load L2 set higher than the first set load L1, the duty ratio D is set to, for example, the maximum (100%) D0. From another point of view, for example, the cross-sectional area of the throttle unit 12 and the mixed fluid passage 13 is set so that the mixing ratio of the mixed fluid amount to the liquid fuel amount is optimal when D = D0. become.

On the other hand, at the time of engine low load operation where L ≦ L1, the duty ratio D is set to D1 smaller than D0. As a result, the mixing ratio is reduced. During low engine load operation, combustion is likely to be unstable because the amount of liquid fuel injected from the injection valve 2 is small. Therefore, the mixing ratio is reduced to reduce the absolute amount of the fluid to be mixed, thereby stabilizing the combustion.

On the other hand, at the time of engine high load operation where L ≧ L2, the duty ratio D is set to D2 smaller than D0.
As a result, also in this case, the mixing ratio is reduced.
During high engine load operation, the amount of liquid fuel to be injected from the injection valve 2 is large. Therefore, if an attempt is made to inject a mixture of this large amount of liquid fuel and a corresponding amount of fluid to be mixed, the injection of the injection valve 2 The period becomes extremely long. Therefore, the injection time is shortened by reducing the mixing ratio.

Note that D1 and D2 may be zero.
That is, the mixing of the liquid fuel and the fluid to be mixed may be stopped during the low-load or high-load operation of the engine. Further, when the engine is stopped, the control valve 15 can be kept closed.
In this way, it is possible to prevent the mixed fluid from flowing out of the mixed fluid tank 9 particularly when the mixed fluid is a substance that can be vaporized at room temperature.

FIG. 5 shows a routine for calculating the duty ratio D of the control valve 15. This routine is executed by interruption every predetermined set time. Referring to FIG. 5, first, at step 100, it is determined whether or not the engine load L is equal to or less than a first set load L1. When L ≦ L1, the routine proceeds to step 101, where the duty ratio D is D1
It is said. On the other hand, when L> L1, the routine next proceeds to step 102, where it is determined whether or not L is equal to or greater than the second set load L2. If L ≧ L2, step 10
Proceeding to 3, D is set to D2.

On the other hand, if L <L2 in step 102, that is, if L1 <L <L2, then step 1
Proceeding to 04, D is set to D0. The control valve 15 is controlled so that its duty ratio becomes D. By the way, in the present embodiment, after all, both the liquid fuel and the fluid to be mixed are pressure-fed by the pressurizing pump 6. Alternatively, it can be considered that the fluid to be mixed is pumped by the pump for pumping the fuel. In any case, there is no need to provide a pump for the fluid to be mixed. as a result,
Requires less space.

In the embodiments described above, the outflow end of the fluid passage 13 to be mixed is opened in the throttle portion 12 (see FIG. 2). However, the outflow end can be opened downstream of the throttle section 12 as long as the pressure reducing action is applied. Further, as described above, in the present embodiment, the porous body 14 is provided at the outflow end of the mixed fluid passage 13 so that the liquid fuel and the mixed fluid are uniformly mixed. To further promote such uniform mixing,
A stirring device for stirring the mixture can also be provided downstream of the throttle section 12, for example, in the fuel supply pipe 7.
This stirring device is formed, for example, of a rib extending spirally along the longitudinal axis on the inner wall surface of the fuel supply pipe 7.

[0033]

As described above, the atomization of the liquid fuel can be stably obtained.

[Brief description of the drawings]

FIG. 1 is an overall view of a diesel engine.

FIG. 2 is an enlarged sectional view of a portion II in FIG.

FIG. 3 is an enlarged sectional view of a part III in FIG. 2;

FIG. 4 is a diagram showing a duty ratio D of a control valve.

FIG. 5 is a flowchart illustrating a routine for calculating a duty ratio D;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine body 2 ... Injection valve 6 ... Pressurizing pump 8 ... Fuel tank 9 ... Fluid tank to be mixed 12 ... Throttle part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 37/04 F02M 43/00 43/00 25/02 T (72) Inventor Kazuhiro Omae Toyota City, Aichi Prefecture 1 Toyota Town F-term in Toyota Motor Corporation (reference) 3G066 AA07 AB02 AB04 AB05 AB06 AC09 AD04 BA03 CE22 DC15 DC18

Claims (4)

[Claims] A fuel passage for supplying a liquid fuel from a fuel tank to an injection valve, a fluid passage for supplying a fluid to be mixed different from the liquid fuel from the fluid tank at a connection portion; Thereby, a mixture in which the fluid to be mixed is mixed with the liquid fuel is formed, and the fluid to be mixed in the mixture is brought into a supercritical state by supercritical state generating means arranged in the fuel passage downstream of the connection portion. A fuel injection device for an internal combustion engine configured to inject a mixture from an injection valve, wherein a supercritical state generating means maintains a mixed fluid contained in a liquid form in a mixed fluid tank in a liquid state while maintaining the liquid. A fuel supply device for an internal combustion engine adapted to be supplied. 2. The pressure or temperature in the mixed fluid passage and the fuel passage from the mixed fluid tank to the supercritical state generating means so that the mixed fluid is maintained in a liquid state. 3. A fuel supply device for an internal combustion engine according to claim 1. 3. A fuel supply system for an internal combustion engine according to claim 2, wherein a pump for feeding fuel is disposed in the fuel passage upstream of the connecting portion, and a discharge pressure of the pump is set higher than a vaporization pressure of the fluid to be mixed. apparatus. 4. The internal combustion engine according to claim 1, wherein a control valve capable of controlling a valve opening ratio is disposed in the fluid passage to be mixed, and the valve opening ratio of the control valve is controlled based on an engine operating state. Engine fuel supply.