WO2007049780A1

WO2007049780A1 - Diesel engine employing dimethyl ether as fuel

Info

Publication number: WO2007049780A1
Application number: PCT/JP2006/321591
Authority: WO
Inventors: Takeshi Tokumaru
Original assignee: Isuzu Motors Limited
Priority date: 2005-10-28
Filing date: 2006-10-24
Publication date: 2007-05-03
Also published as: JP2007120422A; JP4670588B2

Abstract

A diesel engine employing dimethyl ether (DME) as fuel and equipped with a common rail fuel supply unit in which the engine is protected against damage due to leakage of DME. An engine controller (8) is provided with a pressure detection means (81) and a storage means (82), wherein the pressure in the fuel supply unit, e.g. the pressure of a common rail (3), is detected and that pressure is stored when the engine is stopping. When the engine is restarted, pressure at that position is detected and if the detected pressure is lower than the stored pressure by a predetermined value or more, starting of the engine is forbidden. Since the engine cannot be started when the pressure in the common rail (3) is lowered due to trouble at the sealing portion of a fuel injection valve (2), damage to the engine due to combustion of leaked DME can be avoided even if the leaked DME is accumulated in the cylinder.

Description

Description Dielzhenjin fueled with dimethyl ether

The present invention relates to a diesel engine that uses dimethyl ether (DME) as a fuel, and more particularly to a diesel engine that is equipped with a so-called common rail material supply device and injects liquid-floated DME into a cylinder. . Background art

In recent years, dimethyl ether (DME) has been attracting attention as a fuel for combustion engines from the viewpoint of the stable supply of energy or the diversification of fuel that is a source of energy. DME is produced from natural gas, coal, biomass, etc., is harmless to the human body, does not emit soot and SOx by combustion, and is an environmentally friendly fuel.

DME is an ether having the structure of CH ₃ OCH ₃ and has a boiling point of about _25 ° C, and can be easily liquidified by applying pressure or low temperature. For this reason, transportation and storage are simple, and there are few harmful components in the exhaust gas, and the cetane number, which is an indicator of fuel compatibility of a single cell engine, is high. R & D for fuel is being promoted for practical use. By the way, recently, the number of diesel engines that employ a common rail fuel supply system is increasing. As shown in FIG. 1, this fuel supply apparatus includes a high-pressure fuel accumulator tube 3 called a common rail between a fuel injection pump 1 and a fuel injection valve 2 attached to each cylinder of the engine. The high-pressure fuel sent from the fuel injection pump 1 is once accumulated in the common rail 3 and then the accumulated fuel is injected into each cylinder by the fuel injection valve 2. The fuel injection valve 2 in the common rail fuel supply system is as shown in Fig. 3. A solenoid valve 21 for controlling fuel injection is provided. The high-pressure fuel pumped from the fuel injection pump 1 is sent to the fuel reservoir formed in the hole of the holder 2 3 where the needle valve 2 2 slides, and to the control chamber 2 5 at the top of the control piston 24. Sent. The needle valve 22 is pushed downward by the spring 26 and its tip is seated on the seal portion 27.

When the fuel injection timing comes, the solenoid valve 21 opens the orifice 28 and opens the high-pressure fuel from the control port chamber 25 to the low-pressure fuel return pipe. As a result, the pressure at the top of the chondro piston 24 drops, the needle valve 22 is pushed up by the fuel pool high J3E fuel and leaves the seal part 27, and high-pressure fuel is injected into the cylinder from the nozzle 29. Is done. At the end of fuel injection, the orifice 2 8 is closed by the solenoid valve 21, the pressure in the control inlet / outlet chamber 25 is increased, and the needle valve 2 2 is seated on the seal portion '2 7. The fuel injection valve that opens and closes the nozzle hole with the needle # is not limited to the common rail type fuel supply device, but is generally used in diesel engines.

The common rail fuel supply system makes it easy to increase the pressure of the injected fuel, and it is easy to precisely control the fuel injection amount and injection timing, such as particulate matter (PM) or nitrogen oxide (NO x). This fuel supply device is effective in suppressing the generation of harmful exhaust gas components from the diesel engine. Such a common rail fuel supply device is known to be applied to a diesel engine that uses DME as a fuel, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 2 0 03-5 6 4 10.

DME is a fuel that becomes a gas at normal temperature and normal pressure, and is capable of being liquefied by pressurization. Its viscosity is lower than that of light oil or the like normally used as fuel for diesel engines. Diesel engine fuel supply systems have seals to prevent leakage of high-pressure fuel at various locations, and this point remains the same even with common rail fuel supply systems. For example, in the case of a common rail type, the fuel injection valve is controlled using a solenoid valve, and as described above, when fuel is not injected, a seal portion on which a dollar valve is seated, or an electromagnetic valve There is a seal section where the valve closes the orifice. Because liquefied DME has low viscosity, There is a tendency for leakage to occur in the seals of the fuel supply system compared to the fuel from Zellengjin.

In other words, there is a possibility that a large amount of leakage may occur when DME is used as a fuel, even if the seal part is not a problem when using light oil as a fuel. In particular, if there is a slight leak in the seal part where the needle valve sits in the fuel injection valve, the engine will not undergo any special modulation, but when the engine is stopped for a certain period of time, The leaked DME may accumulate in the cylinder in a gaseous state. If DME is accumulated in the cylinder and the engine is restarted, DME is an excellent flammable fuel with a high cetane number and low ignition temperature. May cause explosive combustion and cause engine damage. In order to avoid this, a so-called decompression device is installed in the valve mechanism of the engine, and it is possible to purge the accumulated DME by opening the intake valve etc. at the beginning of startup. Make it more complicated.

It is an object of the present invention to prevent, with a simple means, a situation in which a diesel engine equipped with a common rail fuel supply device and using DME as fuel prevents the engine from being damaged by a leaked DME when restarting after stopping the engine And Disclosure of the invention

In view of the above problems, the present invention detects a pressure inside a fuel supply device such as a common rail in a diesel engine equipped with a common rail fuel supply device using DME as fuel, and stores the pressure when the engine is stopped. If the pressure detected at the time of restarting is lower than the predetermined value, starting the engine is prohibited. That is, the present invention, as described in claim 1,

“Dieseljinjin fueled with dimethyl ether,

The diesel engine includes a fuel tank for storing dimethyl ether, a fuel injection pump for increasing the pressure of the fuel, a common rail for accumulating the increased pressure fuel, and a fuel injection valve for injecting the fuel of the common rail into the cylinder. A fuel supply device comprising: The diesel engine includes a control device having pressure detection means for detecting the pressure inside the fuel supply device, and storage means for storing the detected pressure,

The control device stores the pressure when the storage means stops when the engine is stopped, and the pressure detection means detects the pressure in the fuel supply device when the engine is restarted, and the pressure is stored. When the pressure is lower than the specified pressure by more than the specified value, prohibit engine restart. ''

It has become a feature of this.

As mentioned above, in a high-pressure fuel supply system using DME as a fuel, fuel leakage is likely to occur due to the low-viscosity characteristics of DME, especially when there is even a slight malfunction in the seal part. A large amount of leakage occurs when the engine is shut down. When the operation of Jin Jin is stopped, the fuel injection pump is stopped and the fuel injection valve is closed, and the high-pressure fuel supply system is in a closed space, so if the fuel leaks, the internal pressure will drop.

In the present invention, the engine control device is provided with detection means for detecting the pressure inside the fuel supply device such as a common rail, and a storage means for storing the pressure when the engine is stopped. When the engine is restarted, the pressure in the fuel supply device is first detected. When the pressure is lower than the pressure at the time of engine stop by a predetermined value or more, the engine start is prohibited. ing. Therefore, if the fuel injection valve seal is defective and the common rail pressure is low, the engine cannot be started, and even if a large amount of leaked DME accumulates in the cylinder, Damage to the engine is avoided.

'' Further, the present invention detects a pressure drop in the fuel supply device when the engine is stopped. Therefore, not only a failure of the seal portion of the fuel injection valve but also a seal failure of a pipe joint portion, an electromagnetic valve, etc. It is also possible to detect a pressure drop caused by. While the diesel engine is in operation, the fuel injection pump, etc. is driven, and the pressure in the common rail and the pressure in the piping on the fuel injection pump inlet side are maintained above the set value. The pressure does not drop even if there is There is a difficult aspect. On the other hand, according to the present invention, it is possible to detect a sealing failure at various locations of the fuel supply device by attaching the pressure sensor at a desired location, and to take measures against the malfunction. As described in claim 2, it is preferable that the pressure detecting means detects a pressure in the common rail. In common rail fuel supply systems, the common rail internal pressure gauge is generally controlled for precise control of the injection amount, etc., and a pressure sensor for detecting pressure is installed on the common rail. . Therefore, if the configuration described in claim 2 is adopted, it is possible to use an existing pressure sensor as a pressure detection means, as described in claim 3. The predetermined value of the pressure drop at which starting is prohibited can be configured to vary depending on the time during which the engine is stopped. When configured in this way, it becomes possible to more accurately cope with the situation of the seal failure of the fuel supply device. In other words, if the engine stops operating, even if there is no special failure in the sealing device, even if there is a very small amount of unavoidable fuel leakage, it will remain constant if the operation stops for a long time. The pressure drop will occur. In such a case, the DME leaking into the cylinder is discharged naturally during the operation stop and does not remain in the cylinder. Therefore, if the predetermined value is made variable according to the engine stop time, unnecessary prohibition of restart can be prevented. Brief Description of Drawings

FIG. 1 is a diagram showing an outline of a fuel supply device for a diesel engine according to the present invention. FIG. 2 is a flowchart showing the operation procedure of the present invention.

FIG. 3 is a view showing a fuel injection valve of the common rail fuel supply apparatus. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the fuel supply apparatus of the present invention using DME as fuel will be described with reference to the drawings. Fig. 1 shows the outline of a common rail fuel supply apparatus to which the present invention is applied. The basic equipment configuration and operation are shown in the background art section. It is no different from the device. In other words, a common rail 3 that is a fuel accumulator pipe is provided between the fuel injection pump 1 and the fuel injection valve 2 for increasing the pressure of the fuel. The fuel injection valve 2 injects the accumulated fuel into each cylinder. To do. The configuration of the fuel injection valve 2 is basically the same as the fuel injection valve used in the general common-rail fuel supply device shown in FIG. 3, and has an electromagnetic valve for controlling the fuel injection. A needle valve for opening and closing the injection nozzle is provided. The DME fuel is pressurized and stored in a fuel tank 4 in a liquid form in a liquid state. The fuel tank 4 has a built-in pump, and DME is sent to the fuel feed pump 5 by this pump. The fuel feed pump 5 boosts the DME to a constant pressure and supplies it to the fuel inlet of the fuel injection pump 1, and a fuel cooler 6 is installed in the middle of the pipeline. The fuel cooler 6 cools DME, which has a low boiling point and is easy to evaporate and vaporize, using a cooling fan or the like. Bubbles are generated in the pipeline leading to the fuel injection pump 1 and the fuel injection pump 1 is damaged. To prevent it.

The DME supplied to the fuel injection pump 1 becomes high pressure by this pump, and is sent from the pump outlet to the common rail 3 where it is accumulated. The common rail 3 is connected to high-pressure pipes that distribute fuel to each cylinder, and each high-pressure pipe is connected to the fuel injection valve 2 of each cylinder. In addition, a fuel return pipe 7 is connected to the fuel injection pump 1 and the common rail 3 for collecting surplus fuel generated for adjusting the fuel pressure and returning it to the fuel tank 4. The injection amount and timing of DME injected into each cylinder of the diesel engine are controlled according to the engine load and engine speed by opening and closing the solenoid valve 21 (Fig. 3) of the fuel injection valve 2. Is done. For this reason, the engine is provided with a control device 8, and the valve opening timing and valve opening time of the solenoid valve 21 are determined according to the output of the control device 8. It is. The DME injection pressure is also controlled in accordance with the engine load and the rotational speed. Therefore, the pressure sensor 9 is attached to the common rail 3, and the output signal of the pressure sensor 9 is input to the control device 8. ing. The control device 8 of the present invention has pressure detection means 81 for determining the pressure in the common rail 3 based on an input signal from the pressure sensor 9, and a storage means 82 for storing the detected pressure. The storage means 82 stores the pressure in the common rail 3 when the engine stops operating. Specifically, if this is a diesel engine mounted on a vehicle, after monitoring the state of the engine key operated by the driver and stopping the engine operation when the engine key is operated from ON to OFF The pressure value at that time is stored.

• When the engine is restarted after the operation is stopped, the control device 8 compares the pressure value stored when the operation is stopped with the pressure value detected by the pressure sensor 9 when the operation is restarted. When the pressure value at the time of restart is lower than the stored pressure value by a predetermined value or more, the control device executes a measure for prohibiting the restart of the engine. Specifically, when the engine key is operated from OFF to ON during restart, the pressure in the common rail 3 is detected prior to driving the starter motor that starts the engine, and the detected value decreases by a predetermined value or more. If this is the case, stop energizing the starter motor and notify the driver of the abnormality by means of a warning light or alarm sound. When the restart of the engine is prohibited in this way, the vehicle is brought into a repair factory and repaired.

The predetermined value for determining prohibition of restart is the common rail 3 in the common rail 3 that is generated when a failure occurs in the seat portion 2 7 (Fig. 3) where the needle valve 2 2 of the fuel injection valve 2 is seated and the DME leaks. It is determined by confirming the pressure drop through experiments. If the engine has been stopped for a long time, an inevitable pressure drop occurs even if there is no seal failure. Therefore, the predetermined value may be changed according to the stop time while taking this point into consideration. By using a predetermined value that assumes a poor seal at the seat of the $ 21 fuel injection valve, engine damage due to explosive combustion of the leaked DME can be prevented. A flowchart of the operation procedure in the control device 8 of the present invention is shown in FIG. During engine operation, as shown in Fig. 2 (A), the common Lenore pressure is always detected (SA l), and the engine key ON-OF F state is detected. In step SA2, it is determined whether or not the engine key is OF F. If the engine key is ON, the process returns to SA 1 to detect the common rail pressure again. If the engine key is turned OFF, the process proceeds to step SA3, where the engine is stopped, and the common rail pressure (CRP e) immediately after the engine is stopped is stored (SA4). In this way, the operation procedure when the engine is stopped is completed.

When the engine key is turned ON when the engine is restarted, the common rail pressure (CRP s) at that time is first detected (SB'1) as shown in Fig. 2 (B). Next, the process proceeds to step SB2, and the difference from the common rail pressure (CRP e) stored when the engine is stopped is calculated, and it is determined whether or not it is smaller than a predetermined value (P d) set in advance. . If it is smaller than the predetermined value (P d), it is determined that there is no DME leakage, and the engine is restarted (SB 3). However, if the value is larger than the predetermined value, there is a possibility that DME leaked in the cylinder due to the defective seal part has accumulated, so proceed to step (SB 4) and activate the alarm. And the engine cannot be started. By the way, when changing the above-mentioned predetermined value (P'd) depending on the stop time, the steps of (A) and (B) are continued, the stop time is entered in the middle, and the predetermined value is changed. And add. Industrial application fields

'As described in detail above, the present invention detects the internal pressure of the fuel supply device in order to prevent engine damage due to DME leakage in a DME fueled diesel engine. The pressure is memorized at the time of stop, and when the pressure at the time of restart is lower than a predetermined value, engine start 'is prohibited. Therefore, the present invention can be used for a general diesel engine using DME as a fuel, and a diesel engine for a vehicle such as a stationary diesel engine. Obviously, it can be applied to other things. In the above embodiment, the pressure in the common rail is detected. However, the pressure to be detected is not limited to this portion. For example, if the pressure of the pipe on the fuel injection pump inlet side is detected, the fuel pressure is reduced. It is possible to prevent problems due to poor seal seals.

Claims

A diesel engine fueled with dimethyl ether, comprising:

The diesel engine includes a fuel tank for storing dimethyl ether, a fuel injection pump for increasing the pressure of the fuel, a common rail for accumulating the increased pressure fuel, and a fuel injection valve for injecting the fuel of the common rail into the cylinder. A fuel supply device comprising:

The diesel engine includes a control device having a pressure detection means for detecting the pressure inside the fuel supply device and a storage means for storing the detected pressure.

The control device stores the pressure at the time when the engine is stopped when the engine is stopped, and the pressure detecting means detects the pressure inside the fuel supply device when the engine is restarted, and the pressure is stored. A diesel engine that prohibits restarting the engine when the pressure drops below a predetermined value.

The diesel engine according to claim 1, wherein the pressure detection means detects a pressure − in the common rail.

The diesel engine according to claim 1 or 2, wherein the predetermined ^: under a pressure drop at which the restart of the engine is prohibited is variable according to a time during which the operation of the engine is stopped. .