JP2001115866A - Starting control device for diesel engine for dimethyl ether - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of abnormal combustion during starting of an engine and prevent the generation of abnormal vibration occasioned thereby, in a diesel engine using dimethyl ether as fuel. SOLUTION: A starting device for a diesel engine for dimethyl ether according to this invention comprises a fuel injection device 10 to inject fuel consisting of dimethyl ether, in the combustion chamber 9 of an engine 1; a starting control valve 13 driven by an actuator 14 and openably closing an exhaust port 5 regardless of a regular exhaust timing; a sensor 16 to detect dimethyl ether concentration in a spot situated downstream from the starting control sensor 13; and a control means 12 to control the injection state of the fuel injection device 10 in a non-injection state until the detecting value of the sensor 16 after starting of a starter is adjusted to a prescribed value or less and an actuator 14 to maintain the starting control valve 13 in an opening state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a start control device for a diesel engine using dimethyl ether as a fuel.

[0002]

2. Description of the Related Art In recent years, in the field of diesel engines, dimethyl ether (hereinafter also referred to as DME) has been spotlighted as an alternative fuel to light oil (see Japanese Patent Application Laid-Open No. 11-107871). DME (C ₂ H ₆ O) has a melting point of -138.5 ° C and a boiling point
It is a gas at -23.7 ° C (1 atm), at normal temperature and pressure, has a cetane number equivalent to that of light oil, has a higher specific gravity than air, is generally decomposed in air, and is said to be non-toxic.

[0003]

Incidentally, since DME has a lower viscosity than light oil, there is a possibility that fuel remaining in the fuel injection nozzle leaks from the injection hole into the combustion chamber while the engine is stopped. Further, in a diesel engine equipped with a common rail fuel injection device, the residual pressure in the high-pressure pipe when the engine is stopped is much higher than the atmospheric pressure, so that the amount of fuel leaking from the injection holes also increases. If the engine is started as usual with such leaked fuel remaining in the combustion chamber, abnormal combustion occurs, abnormal vibration and noise are generated, and the engine may be damaged at worst. .

[0004]

SUMMARY OF THE INVENTION A starting control apparatus for a dimethyl ether diesel engine according to the present invention comprises: a fuel injection device for injecting dimethyl ether fuel into a combustion chamber of the engine; and a regular exhaust gas driven by an actuator. A start control valve capable of opening and closing the exhaust port irrespective of timing, a sensor for detecting the dimethyl ether concentration downstream of the start control valve, and the fuel supply until the detection value of the sensor becomes a predetermined value or less after the starter is started. And control means for controlling the actuator so as to keep the start control valve open while controlling the injection device to a non-injection state.

According to the present invention, even if the starter is started, the fuel injection is stopped and the start control valve is controlled to open until the detection value of the sensor becomes equal to or less than the predetermined value. Fuel can be exhausted through an exhaust port. Thereby, abnormal combustion at the time of starting the engine can be prevented, and the above-mentioned problem can be solved.

Here, it is preferable that the start control valve is also used as a dedicated valve or an exhaust valve of the compression brake device.

[0007]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, the DME engine 1 includes a cylinder 2, a piston 3, an intake port 4, an exhaust port 5, an intake valve 6, and an exhaust valve 7. A cavity 8 is formed at the top of the piston 3, and a combustion chamber 9 is defined by the top of the piston 3 and the cylinder 2. The intake valve 6 and the exhaust valve 7 are driven by a camshaft (not shown).
The engine 1 is provided with a common rail type fuel injection device, and only its injector is indicated by reference numeral 10. The common rail fuel injection device pressurizes liquefied DME as a fuel to several tens to several hundreds (MPa) with a high-pressure pump (not shown), accumulates the pressure in the common rail, and injectors 10 for each cylinder (only one cylinder is shown in the figure). To be distributed and supplied. The injector 10 is disposed with the injection hole 11 at the tip thereof facing the inside of the combustion chamber 9. The injector 10 is connected to an electronic control unit (hereinafter referred to as “ECU”) 12 and is controlled to open and close by receiving a drive signal from the ECU 12. The fuel is already pressurized and liquefied in the feed line before the high-pressure pump.

A start control valve 13 is provided adjacent to the exhaust valve 7. The start control valve 13 is driven up and down by an actuator 14 to open and close the inlet of the exhaust port 5. The actuator 14 is also connected to the ECU 12 and receives a drive signal from the ECU 12 to open and close the start control valve 13. Thus, the start control valve 13 can open and close the exhaust port 5 irrespective of the normal exhaust timing, that is, the opening and closing timing of the exhaust valve 7 based on the cam lift.

The exhaust port 5 forms a part of the exhaust passage 15 on the combustion chamber 9 side.
A DME concentration sensor 16 (constituting the sensor of the present invention) for detecting the concentration is provided. The DME concentration sensor 16 is provided downstream of the start control valve 13 and is connected to the ECU 12.

In the exhaust passage 15, a catalyst 17 is provided downstream of the DME concentration sensor 16, and an exhaust shutter 18 is provided upstream of the DME concentration sensor 16. The exhaust shutter 18 is also connected to the ECU 12 so as to be opened and closed.

The intake port 4 also forms a part of the intake passage 19 on the combustion chamber 9 side. An intake shutter 20 is provided in the middle of the intake passage 19, and the intake shutter 20 is connected to the ECU 12 to be opened and closed. .

An engine rotation sensor 21 is also connected to the ECU 12 so that the engine rotation speed can be detected.

Next, the operation of the present embodiment will be described.

As described above, in this engine, the DME
The fuel may leak from the injection hole 11 of the injector 10 and stop in the combustion chamber 9 when the engine is stopped due to its low viscosity. And while the engine is stopped,
The line pressure is maintained at a high pressure to prevent fuel vaporization, and a relatively large amount of fuel may leak. If the engine is started in this state, problems such as abnormal combustion will occur.

Therefore, the present apparatus performs the following starting control. FIG. 2 shows the details of the start control, which is performed by the ECU 12. As shown, this control is started at the same time as the engine key is turned on.

First, at step 101, the start control valve 13 is opened, and the exhaust shutter 18 and the intake shutter 20 are fully opened as shown by the solid line in FIG. While the engine is stopped, the start control valve 13 is closed, and the exhaust shutter 18 and the intake shutter 20 are fully closed as shown by the phantom line in FIG. While the engine is stopped, it is conceivable that the fuel accumulated in the combustion chamber 9 evaporates and leaks to the outside through the exhaust passage 15 and the intake passage 19, but the exhaust shutter 18 and the intake shutter 20 are fully closed as described above. Thus, external leakage of DME can be prevented as much as possible.

Next, at step 102, the fuel injection device is controlled to a non-injection state. Specifically, the injector 10 is OF
Maintain F state. Thereby, the fuel injection is stopped for a while.

Thereafter, the routine proceeds to step 103, where it is determined based on the output of the engine rotation sensor 21 whether or not the current engine rotation speed is greater than 0, that is, whether or not the engine is rotating. At this time, since the fuel injection is not performed, if the engine is rotating, the engine is only being rotated by the starter. If it is rotating, the process proceeds to step 104, and after waiting for a preset time ΔT, the process proceeds to step 105. If not rotating, step 104
repeat.

In step 105, it is determined whether the engine is running again. If it is not rotating, the process returns to step 103, and if it is, the process proceeds to step 106.
In step 106, the detection value of the DME concentration sensor 16,
That is, it is determined whether or not the current concentration of DME in the exhaust gas is equal to or less than a predetermined value N. If it exceeds the predetermined value N, the process returns to step 105. If not more than the predetermined value N, step 1
In step 07, the start control valve 13 is closed, and in step 108, the non-injection state (fuel injection stop state) of the fuel injection device is released. As a result, the fuel injection device can perform injection as usual, and the engine is started by continuing the starter ON and performing fuel injection.

As described above, according to this control, even if the starter is started, the detection value of the DME density sensor 16 is kept at the predetermined value N.
Until the fuel injection becomes below, the fuel injection is stopped and the start control valve 1
Since the fuel cell 3 is opened, the fuel remaining in the combustion chamber 9 during that time can be discharged through the exhaust port 5, thereby preventing abnormal combustion at the time of starting the engine, and preventing abnormal vibration and the like accompanying the combustion. As the predetermined value N, of course, a safe value that does not hinder the engine start is selected. Therefore, after the detected value of the DME concentration sensor 16 becomes equal to or less than the predetermined value N, the fuel injection is performed as described above. By releasing the suspension and closing the start control valve 13, the start can be performed as usual. Since the residual fuel discharged during the non-injection period is adsorbed by the catalyst 17, there is no danger of DME leaking to the outside.

Here, the process waits for a predetermined time ΔT in step 104, taking into account the time required for the residual fuel in the combustion chamber 9 to reach the DME concentration sensor 16. This ΔT is determined in consideration of the distance from the inlet of the exhaust port 5 to the DME concentration sensor 16, the response delay of the DME concentration sensor 16, and the like.

The reason for determining whether or not the engine is rotating in step 105 is to confirm that the engine is still cranking even after the lapse of ΔT and that the starting operation is continued.

As can be seen from the above description, in this embodiment, the ECU 12 serves as the control means of the present invention.

Incidentally, the engine 1 here is applied to a vehicle, and the start control valve 13 here is also used as a dedicated valve of the compression brake device. In general, a compression brake device increases the engine braking force by releasing the compression pressure while stopping fuel injection when the engine brake is used. The Jacob type and the like are known. During the compression process, during the compression stroke and the expansion stroke, or during the entire stroke, a dedicated valve (so-called third valve) provided separately from the exhaust valve is opened by an actuator to release the compression pressure from the exhaust port. Here, since the dedicated valve of such a compression brake device and the start control valve 13 are also used, the number of parts can be reduced as much as possible, which can contribute to simplification and cost reduction. Some compression brake devices lift not the dedicated valve but the exhaust valve of the engine itself. Therefore, such an exhaust valve may be used also as the start control valve 13.

In the start control described above, the start control valve 13 is opened during the entire stroke. However, similarly to the compression brake device, the opening may be performed only during the compression process or during the compression stroke and the expansion stroke. The point is that the compression is not performed in the combustion chamber 9 and the ignition by the residual fuel is not performed. In this sense, the “start control valve is kept open” according to the present invention.
This includes such an intermittent open state.

The exhaust shutter 18 of the present embodiment is also used as the exhaust shutter of the exhaust brake device. Thereby, further simplification and cost reduction can be achieved.

The exhaust shutter 18 is connected to the DME density sensor 16
, And may be closed during the above-described start control. In this way, the residual fuel discharged from the combustion chamber 9 can be stopped immediately before the exhaust shutter 18, and external leakage of the DME can be prevented without the catalyst 17. In this case, the exhaust shutter 18 is preferably provided as far as possible from the DME concentration sensor 16 so as not to affect the detection density of the DME concentration sensor 16.

As described above, the embodiments of the present invention are not limited to those described above. For example, the present invention can be applied to a row pump type fuel injection device having an electronic governor.

[0030]

The present invention exhibits the following excellent effects.

(1) It is possible to prevent abnormal combustion at the time of starting the engine, and to prevent abnormal vibration and the like accompanying the combustion.

(2) The apparatus can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the contents of start control according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine 5 Exhaust port 9 Combustion chamber 10 Injector 12 Electronic control unit 13 Start control valve 14 Actuator 16 DME concentration sensor N Predetermined value

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F02N 17/08 F02N 17/08 Z F term (Reference) 3G092 AA02 AB05 AB18 BB06 BB10 CB01 CB02 CB05 DA02 DA07 DA14 DA15 DC03 DC12 DC13 DD02 DF01 DF02 DF08 DF10 DG07 EA09 EA11 EA14 EA15 EA28 EA29 EC03 FA14 FA15 FA31 FA39 GA01 GA10 HD04X HE01X HF19X 3G301 HA02 HA21 JA21 JA37 KA01 KA28 LA03 LB04 MA15 MA24 MA25 NB11 PD01A PE01PF

Claims (2)

[Claims] 1. A fuel injection device for injecting fuel composed of dimethyl ether into a combustion chamber of an engine, a start control valve driven by an actuator to open and close an exhaust port regardless of a regular exhaust timing, and the start control A sensor for detecting the dimethyl ether concentration downstream of the valve, and after the starter is started, the fuel injection device is controlled to a non-injection state until the detection value of the sensor becomes a predetermined value or less, and the start control valve is kept open. A starting control device for a dimethyl ether diesel engine, characterized by comprising control means for controlling the above actuator. 2. The start control device for a dimethyl ether diesel engine according to claim 1, wherein the start control valve is also used as a dedicated valve or an exhaust valve of a compression brake device.