JPH06101588A - Method for controlling fuel circulation system of high-pressure injection engine - Google Patents

Abstract

PURPOSE:To keep fuel temperature at a proper value so as to improve spraying from an injector and to improve power consumption, emissions and running properties by switching a fuel line according to the operating state of an engine. CONSTITUTION:The temperature TF of fuel supplied to an injector is detected and is compared with a flow switching temperature TFS in step (S)102. When TF<TFS, S103 is initiated and return fuel is returned via a bypass line into a sub-fuel tank disposed in an engine room. Since the fuel is warmed by heat radiated from an engine main body, the fuel temperature is rapidly raised and good spraying is achieved in a short time. When TF >= TFS, S104 is initiated in which the return fuel is returned into a normal main fuel tank via a return passage. Since the return fuel is cooled while being returned into the main fuel tank, generation of vapor or percolation can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel circulation system control method for a high pressure injection type engine, in which the fuel flow path is switched according to the operating condition of the engine.

[0002]

2. Description of the Related Art Generally, in a high-pressure injection type engine in which fuel is directly injected into a combustion chamber, the spray property of the fuel significantly changes depending on the fuel temperature. In other words, when the fuel temperature is low such as during cold start, the spray property deteriorates due to the viscosity of the fuel, and because the fuel vaporization is insufficient, the improper combustion causes the exhaust emission to deteriorate. On the other hand, when the fuel temperature rises, vapor and percolation are likely to occur in the fuel passage, and good restart performance cannot be obtained. However, since the fuel passes through the return passage, is returned to the fuel tank, and is cooled while the fuel is fed again, there is a problem that the fuel temperature is low at the time of cold start rather than the occurrence of vapor and percolation.

As a countermeasure for this, there is a heater installed in the fuel passage to positively warm the fuel.
It is difficult to mount the heater mounting space in a narrow space in the middle of the fuel passage, which not only complicates maintenance but also increases manufacturing man-hours and raises cost.

On the other hand, in JP-A-1-121562, at the time of cold start, the fuel flowing in the fuel return passage is directly guided to the upstream side of the fuel pump and circulated in the fuel passage to accelerate the fuel temperature rise. The technology is disclosed.

[0005]

In the above-mentioned prior art, a part of the return fuel is recirculated to the fuel passage without passing through the fuel tank to improve the fuel temperature increasing efficiency. Since the cold fuel stored in the fuel tank is always mixed in the fuel passage on the side, it is difficult to raise the temperature of the fuel in the fuel passage to a temperature sufficient to obtain a predetermined spray property in a short time, and it is difficult to cool the fuel. There is a limit to improving fuel efficiency and exhaust emission when starting the engine.

The present invention has been made in view of the above circumstances, and has a simple structure to raise the temperature of cold fuel in a cold start or the like to a temperature sufficient to obtain a predetermined spray state in a relatively short time. To provide a fuel circulation system control method for a high-pressure injection engine, which is capable of improving fuel efficiency, reducing exhaust emissions, and having good running performance, and which is easy to handle, low in cost, and highly reliable. It is an object.

[0007]

A fuel circulation system control method for a high-pressure injection engine according to the present invention is a high-pressure injection engine in which fuel is directly injected into a combustion chamber, and a fuel temperature and a preset flow path switching temperature are set. If the fuel temperature is lower than the flow passage switching temperature, the procedure for comparing the return fuel to the sub fuel tank arranged in the engine room through the bypass passage, and the fuel temperature is equal to or higher than the flow passage switching temperature. In this case, the procedure for returning the return fuel to the main fuel tank via the return passage is provided.

[0008]

[Operation] In the present invention, when the fuel temperature is lower than the preset flow path switching temperature, the return fuel is returned to the sub fuel tank arranged in the engine room through the bypass passage, and temporarily returned to this sub fuel tank. By storing in the fuel cell, the temperature rise of the fuel is promoted by the radiant heat from the engine and the like. Further, since this sub fuel tank is arranged in the engine room, the heat retaining property is good.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a flow chart showing a fuel circulation system control routine, FIG. 2 is an overall schematic view of an engine control system, and FIG. 3 is a circuit diagram of a control device.

In FIG. 2, reference numeral 1 denotes an engine main body of a high-pressure injection type two-cycle engine. A combustion chamber 5 formed by a cylinder block 3, a cylinder head 2 and a piston 4 of the engine main body 1 has an ignition coil 6 and an ignition coil 6. An ignition plug 7 connected to the secondary side and an injector 8 for in-cylinder direct injection are exposed. In addition, a scavenging port 3a and an exhaust port 3b are formed in the cylinder block 3,
In the cooling water passage 3c formed in the cylinder block 3,
The water temperature sensor 9 is exposed.

An air supply pipe 10 is communicated with the scavenging port 3a, and an air cleaner 11 is provided upstream of the air supply pipe 10.
Is attached, and a scavenging pump 12 driven by rotation of the crankshaft 1a is provided on the downstream side, and fresh air is supplied by the scavenging pump 12.
The inside of the combustion chamber 5 is forcibly scavenged.

A bypass control valve 15 interlocking with an accelerator pedal 14 is provided in a bypass passage 13 that bypasses the scavenging pump 12, and an accelerator opening sensor 16 is connected to the accelerator pedal 14. .

The exhaust port 3b has an exhaust rotary valve 1 which opens and closes in conjunction with the crankshaft 1a.
7 is provided, and an exhaust pipe 18 is connected through the exhaust rotary valve 17. Further, a catalytic converter 19 is interposed in the exhaust pipe 18, and a muffler 20 is connected to the downstream end.

A crank rotor 21 is rotatably mounted on a crank shaft 1a supported by the cylinder block 3, and a crank angle sensor 22 including an electromagnetic pickup is provided on the outer periphery of the crank rotor 21.

Reference numeral 23 is a fuel circulation system, which is composed of a fuel feed 23a for supplying fuel to the injector 8 and a fuel return 23b for returning excess fuel. Feed 23a
A main fuel tank 24 disposed relatively far from the engine body 1 such as a rear portion of the vehicle body to a first feed pump 25 and a sub fuel tank 2 disposed in the engine room.
A fuel supply passage 31 that communicates with the injector 8 arranged in each cylinder is communicated via the second feed pump 27, the fuel filter 28, the high-pressure fuel pump 29, and the high-pressure filter 30. An accumulator 32 is connected to the fuel supply passage 31.

Further, the fuel return 23b of the fuel circulation system 23 is communicated with the electromagnetic switching valve 34 from the fuel supply passage 31 via a high pressure electromagnetic pressure regulator 33 such as a linear solenoid. A return passage 35 facing the main fuel tank 24 and a bypass passage 36 facing the sub fuel tank 26 are selectively open to the electromagnetic switching valve 34. In the figure, the electromagnetic switching valve 34 is OF
In the F (solenoid coil non-energized) state, the fuel return 23b communicates with the return passage 35, and when the electromagnetic switching valve 34 turns ON (energizes the solenoid coil), the fuel return 23b communicates with the bypass passage 36. To be done. Further, the high-pressure electromagnetic pressure regulator 33 is set so that the valve opening becomes smaller and the fuel pressure rises as the drive current increases.

Further, a fuel bypass is provided between the fuel filter 28 and the high pressure fuel pump 29 of the fuel feed 23a and between the high pressure electromagnetic pressure regulator 33 and the electromagnetic switching valve 34 of the fuel return 23b. A passage 37 is connected, and a low pressure pressure regulator 38 is interposed in the fuel bypass passage 37.

A liquid level sensor 39 faces the sub fuel tank 26, and a fuel pressure sensor 40 and a fuel temperature sensor 41 are connected to the fuel supply passage 31.

Reference numeral 46 in FIG. 3 denotes an electronic control unit (E
CU), CPU 47, ROM 48, RAM 49, backup RAM 50, and I / O interface 51
Are composed of a microcomputer or the like connected to each other via a bus line 52.

The ECU 46 has a constant voltage circuit 53.
The constant voltage circuit 53 is connected to the battery 55 via the relay contact of the ECU relay 54, and the relay coil of the ECU relay 54 is connected to the battery 55 via the ignition switch 56. There is. When the ignition switch 56 is turned on, the contact of the ECU relay 54 is turned on, the voltage of the battery 55 is supplied to the constant voltage circuit 53, and the stabilized voltage is supplied from the constant voltage circuit 53 to each part of the ECU 46.
On the other hand, the backup voltage is constantly applied to the backup RAM 50 from the constant voltage circuit 53.

A starter switch 57 is connected to the battery 55, and a starter motor 59 is connected to the starter switch 57 via a relay contact of a starter motor relay 58. Further, the first feed pump 25 is connected to the battery 55 by the first feed pump relay 6
The second feed pump 27 is connected through the relay contact of 0, and the second feed pump 27 is connected through the relay contact of the second feed pump relay 61.

A battery 55 is connected to the input port of the I / O interface 51 to monitor the battery voltage and the starter switch 5
7, crank angle sensor 22, accelerator opening sensor 16,
Water temperature sensor 9 Fuel pressure sensor 40, Fuel temperature sensor 4
1. The liquid level sensor 39 is connected.

On the other hand, an igniter 41 for driving the ignition coil 6 is connected to the output port of the I / O interface 51, and a relay coil of the first feed pump relay 60, The relay coil of the two-feed pump relay 61, the injector 8, the high pressure electromagnetic pressure regulator 33, and the electromagnetic switching valve 34 are connected.

Next, the fuel circulation system control by the ECU 46 will be described with reference to the flowchart of FIG.

The flowchart of FIG. 1 is a routine that is executed every predetermined time when the power is turned on by turning on the ignition switch 56. First, in step (hereinafter abbreviated as "S") 101, the second feed pump relay 61 is operated. The I / O port output value G2 for the relay coil is set to 1, and the second feed pump relay 61 is turned on to operate the second feed pump 27. Therefore, while the ECU 46 is powered on by turning on the ignition switch 56, the second field pump relay 61
Keeps the ON state, and the second feed pump 27 is always in the operating state.

Next, in S102, the fuel temperature sensor 41
The fuel temperature TF in the fuel supply passage 31 detected in Step 2 is compared with a preset flow path switching temperature TFS. If TF <TFS,
The process proceeds to S103, and if TF ≧ TFS, the process proceeds to S104.

It is determined that TF <TFS in the above S102, and S1
When proceeding to 03, the liquid level H of the fuel stored in the sub-fuel tank 26 detected by the liquid level sensor 39 is compared with a preset liquid level lower limit value HL, and if H <HL, S10
5. If H 2 ≧ HL, go to S106.

When proceeding to S105, the output value G of the I / O port for the relay coil of the first feed pump relay 60
When 1 is set to 1 and the first feed pump relay 60 is turned on, the first feed pump 25 is driven. Further, when the process proceeds to S106, the first feed pump relay 60
The I / O port output value G1 for the relay coil is set to 0 and the first feed pump relay 60 is turned off to stop the operation of the first feed pump 25.

Then, when the operation proceeds from S105 or S106 to S107, the I / O port output value G3 for the electromagnetic switching valve 34 for switching the circulation path of the fuel circulation system 23 is set to 1 and the electromagnetic switching valve 34 is turned on. The return 23b is connected to the bypass passage 36 communicating with the sub fuel tank 26, and the routine is exited.

On the other hand, if TF ≧ TFS is determined in S102 and the process proceeds to S104, I for the electromagnetic switching valve 34 is changed.
/ O port output value G3 is set to 0 and the electromagnetic switching valve 34 is turned off.
After the fuel return 23b is communicated with the return passage 35 communicating with the main fuel tank 24, the I / O port output value G1 for the relay coil of the first feed pump relay 60 is set to 1 in S108, and the first feed pump After driving 25, the routine exits.

As described above, according to this embodiment, when the fuel temperature TF is lower than the flow path switching temperature TFS, the electromagnetic switching valve 34 is turned on and the sub-fuel tank 2 arranged in the engine room.
Since the return fuel is returned to 6, the return fuel is warmed by the radiant heat from the engine body 1 and the like, and the temperature rise of the fuel is accelerated. As a result, the property of fuel spray from the injector 8 becomes good in a short time, a good combustion state is obtained, and fuel consumption and exhaust emission are improved. Moreover, since no special heating means is required, the structure is simple and the handleability is good.

When the amount of fuel stored in the sub fuel tank 26 decreases and the liquid level H falls below the lower limit value HL, the first feed pump 25 operates to replenish the fuel, so the sub fuel tank 26 There is no depletion of the fuel inside or a sudden drop in fuel temperature.

On the other hand, when the fuel temperature TF is equal to or higher than the flow path switching temperature TFS, the electromagnetic switching valve 34 is turned off and the return fuel is returned to the main fuel tank 24 arranged at a position relatively distant from the engine body 1 such as the rear part of the vehicle body. Since the return fuel is cooled while flowing through the return passage 35, the generation of vapor and percolation is prevented, and the fuel injection from the injector 8 due to vapor generation or the injector 8 due to percolation occurs. The abnormal injection is eliminated, and the malfunction such as poor running property and seizure of the high-pressure fuel pump 29 due to the occurrence of vapor is prevented.

As a result, as a whole, the fuel temperature can always be appropriately maintained regardless of the engine condition, the outside air temperature, and the like.

[0036]

As described above, according to the present invention,
When the fuel temperature is lower than the preset flow path switching temperature, the return fuel is returned to the sub-fuel tank arranged in the engine room through the bypass passage. Since the fuel is temporarily stored in the sub fuel tank, it is possible to accelerate the temperature rise of the fuel by receiving radiant heat from the engine or the like, and to raise the temperature to a temperature sufficient to obtain a predetermined spray property in a short time. .

Further, since this sub fuel tank is arranged in the engine room, the heat retaining property is good and the rise of the fuel temperature is further promoted.

In addition, since the radiant heat from the engine or the like is used to warm the fuel, no heating means is required, and
It has a simple structure, easy handling, low cost and high reliability.

When the fuel temperature is equal to or higher than the flow path switching temperature, the return fuel is returned to the normal main fuel tank through the return passage, so that the fuel is cooled while returning to the fuel tank. Therefore, it is possible to effectively prevent the occurrence of vapor or percolation.

[Brief description of drawings]

FIG. 1 is a flowchart showing a fuel circulation system control routine.

FIG. 2 is an overall schematic diagram of an engine control system.

FIG. 3 is a circuit diagram of a control device.

[Explanation of symbols]

 5 ... Combustion chamber 24 ... Main fuel tank 26 ... Sub fuel tank 35 ... Return passage 36 ... Bypass passage TF ... Fuel temperature TFS ... Flow passage switching temperature

Claims (1)

[Claims] 1. In a high-pressure injection engine for directly injecting fuel into a combustion chamber, a procedure for comparing a fuel temperature with a preset flow passage switching temperature, and a return fuel when the fuel temperature is lower than the flow passage switching temperature. To return to the sub-fuel tank in the engine room via the bypass passage, and to return the return fuel to the main fuel tank via the return passage when the fuel temperature is equal to or higher than the flow passage switching temperature. A method for controlling a fuel circulation system of a high-pressure injection engine, comprising: