JPH0574705B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection amount control device for a diesel engine.

[Prior art]

Generally, in the fuel system of a diesel engine, the fuel from the fuel tank is metered by a fuel injection pump according to the operating conditions of the engine, such as engine speed and load, and is distributed to each cylinder. It is injected into the compressed high-temperature air of the combustion chamber to ignite and burn. However, in this case, if the amount of fuel is simply injected according to the operating condition, when the engine starts,
A problem arises in that the inner surface of the cylinder and the piston ring are not sufficiently sealed, and the compression pressure within the combustion chamber is not very high, resulting in poor ignition performance.

Conventionally, in order to eliminate the above-mentioned problems, when starting the engine, fuel is injected in an amount larger than the maximum injection amount F/Q during normal operation, so-called starting supercharging amount, which causes the combustion chamber to Control has been carried out to improve the sealing performance of the fuel for good ignition, and then to reduce the injection amount.One example of this is conventionally shown in Japanese Utility Model Application No. 136138/1983.

However, with such a conventional starting injection amount control method, it is still not possible to obtain sufficient startability in a diesel engine with a low compression ratio, and this has been an obstacle to the practical use of a diesel engine with a low compression ratio.

Recently, various types of electronically controlled fuel injection pumps have been developed as fuel injection pumps for diesel engines, and these pumps use control signals from microcomputers to variably control the accelerator opening to increase the amount of fuel injected. This is what we are trying to correct. This electronically controlled fuel injection pump has the advantage that it is possible to create an arbitrary control signal using a microcomputer, and thereby the amount of fuel to be injected can be adjusted to an arbitrary amount.

Furthermore, if we consider the method of controlling the fuel injection amount when starting a diesel engine, we will find the following. That is, when starting a diesel engine, the engine enters an idle state after starting cranking, undergoing initial combustion, complete combustion, and a rising range up to a predetermined rotational speed. Since the sealing performance of the combustion chamber is insufficient between the start of cranking and the first explosion, as mentioned above, a large amount of fuel (starting supercharging amount) is supplied to improve the sealing performance and improve ignition. There was a need to improve the fuel injection rate.Also, after the initial explosion, the rotational speed naturally increases and the sealing performance improves accordingly, so a large amount of fuel injection is not required. This meant that the amount of fuel injected was gradually reduced after the first explosion.

Looking at the ignitability after the first explosion, the temperature inside the combustion chamber is still low even after the first explosion, and when fuel is injected into such a combustion chamber,
Since the fuel dissipates heat within the combustion chamber when vaporized, the temperature within the combustion chamber further decreases, and it is thought that ignitability deteriorates. Therefore, from the viewpoint of improving ignition performance after the first explosion, it is preferable to reduce the amount of fuel injected as much as possible after the first explosion.

Furthermore, when the engine completely explodes, the engine speed increases further and reaches a predetermined speed that is higher than the idle speed, but in this startup region, the temperature inside the combustion chamber has already risen sufficiently.
Even if a large amount of fuel is injected, it is unlikely that the temperature within the combustion chamber will decrease due to the heat of vaporization of the fuel, thereby inhibiting ignitability and combustibility. In this region where the rotational speed rises, from the viewpoint of improving startability, it is desirable to inject as much fuel as possible to shorten the time it takes for the engine to rise to a predetermined rotational speed.

[Purpose of the invention]

The present invention is characterized in that, in the above-mentioned electronically controlled fuel injection pump, the amount of fuel injection can be arbitrarily adjusted by devising the creation of a control signal;
As mentioned above, we focused on the fact that starting performance can be greatly improved by finely controlling the amount of fuel injection depending on the engine starting condition, and it is effective not only for high compression ratio engines but also for low compression ratio engines. It is an object of the present invention to provide a fuel injection amount control device for a diesel engine that can ensure good startability.

[Structure of the invention]

Therefore, this invention provides a fuel injection amount control device for a diesel engine with an electronically controlled fuel injection pump, and sets the fuel injection amount from the start of engine cranking to the first explosion as the starting supercharging amount, and from the first explosion to the complete explosion. The engine is designed to keep the injection amount below the maximum injection amount during normal operation and above the idle increase amount, and to control the rise area from complete explosion to a predetermined rotation speed above the idle rotation speed to the above maximum injection amount. This improves the ignitability after the initial explosion and shortens the time for the rotational speed to rise after the complete explosion, thereby greatly improving the startability.

〔Example〕

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

FIG. 1 shows a fuel injection control device for a diesel engine according to an embodiment of the present invention. In the figure,
1 is an electronically controlled fuel injection pump that adjusts the amount of fuel to be injected, 2 is a rotation sensor that detects the engine rotation speed from the rotational state of the fuel injection pump 1, 3 is a water temperature sensor that detects the engine cooling water temperature, and 4 is a Key switches 5 and 6 are intake shutters and exhaust shutters provided in the intake and exhaust passages of the engine, 7 and 8 are actuators that open and close the intake and exhaust shutters 5 and 6, and 9 is an actuator provided in the intake passage of the engine that opens and closes the intake shutters. 10 is a relay that controls the energization of the air heater 9; 11 is an indicator lamp that indicates the operation of the air heater 9; 12 is a signal that indicates the rotation sensor 2, the water temperature sensor 3, the key switch 4, and the N terminal voltage of the alternator 13; This control device controls the fuel injection pump 1, the actuators 7 and 8 of the intake and exhaust shutters 5 and 6, the air heater relay 10, and the indicator lamp 11 as shown in the timing chart of FIG.

In the above configuration, the rotation sensor 2, the key switch 4, and the alternator 13 serve as a starting state detecting means for detecting the starting state of the engine, and the control device 12 receives the output of the detecting means and controls the fuel injection. The pump is controlled to set the fuel injection amount to a starting supercharging amount that is greater than the maximum injection amount during normal operation from the time the engine starts cranking to the time of the first explosion, and less than the maximum injection amount above from the time of the first explosion to the time of complete explosion. The starting injection amount control means adjusts the amount of injection to the maximum injection amount from the time of complete explosion until the engine reaches a predetermined rotation speed that is higher than the idle rotation speed.

Next, the operation will be explained using FIG. 2. Here, FIGS. 2a to 2g show the operations of the indicator lamp 11, air heater 9, and key switch 4, changes in engine speed, and operations of the intake and exhaust shutters 5 and 6.
and a timing chart of changes in fuel injection amount.

In this device, key switch 4 is activated at time T1.
When turned on (see Fig. 2c), the control device 12 detects this, energizes the relay 10 to make the air heater 9 generate heat (see Fig. 2b), and lights up the indicator lamp 11 (see Fig. 2b). (see figure a),
Also, a control signal is applied to the actuator 7 of the intake shutter 5 to close the intake shutter 5 (see FIG. 2e). When starting the engine in this way,
First, the intake air on the downstream side of the intake shutter 5 is transferred to the air heater 9.
heat it by the indicator lamp 11
Display in .

After a certain period of time has elapsed, at time T2, the intake air reaches a predetermined temperature, and the control device 12 turns off the indicator lamp 11 (see FIG. 2b). After a certain delay in operation, when the key switch 4 is turned to the starter position ST at time T3 (see Figure 2c), engine cranking is started.
The engine is rotated at approximately 200 rpm (see Figure 2d). The control device 12 detects the start of engine cranking from the signal of the key switch 4 and the N terminal voltage of the alternator 13, and applies a first accelerator opening signal to the fuel injection pump 1 to control the fuel injection amount beyond the starting point. Measure the amount to Q1 (see part A in Figure 2g). When cranking starts in this way, fuel injection starts even with the starting supercharging amount Q1, and this large amount of fuel adheres to the inside of the combustion chamber, improving the sealing performance, increasing the compression ratio, and increasing the amount of fuel inside the combustion chamber. temperature increases. At this time, the air heater 9 is activated and the intake shutter 5 is closed to intermittently heat the intake air, and the temperature inside the combustion chamber quickly increases due to the above-mentioned increase in the compression ratio and heating of the intake air.
The engine will explode for the first time.

When the engine explodes for the first time at time T4, the engine speed increases from the above-mentioned 200 rpm to 300-500 rpm (see Figure 2 d), so the control device 12 detects that the engine has exploded for the first time from the signal from the rotation sensor 2. is detected and applies a second accelerator opening signal to the fuel injection pump 1 to reduce the fuel injection amount to a predetermined amount Q2 that is less than the maximum injection F/Q during normal operation and more than the idle increase I/Q (second (see B in Figure g),
When the fuel injection amount reaches the predetermined amount at time T5, the control device 12 stops generating the drive signal to the actuator 7 and opens the intake shutter 5. When the engine explodes for the first time in this way, the fuel injection amount is immediately reduced to the predetermined amount Q2, which suppresses the temperature drop in the combustion chamber caused by the heat of vaporization of the fuel, ignites the fuel well, and reduces the engine speed. about
The speed quickly increases to 800 rpm (see Figure 2 d),
The engine will completely explode.

When the engine completely explodes at time T6, key switch 4 changes from the starter position ST to the ON position.
(see Figure 2c), and the control device 12 detects that the engine has completely exploded from the signal from the key switch 4, and this time applies a third accelerator opening signal to the fuel injection pump 1 to inject fuel. Increase the injection amount to the maximum injection amount F/Q (see section C in Figure 2g).
When the engine completely explodes in this way, the fuel injection amount is increased to the maximum injection amount F/Q, and as a result, the engine speed quickly rises to a predetermined speed, for example, 2000 rpm (see Figure 2 d). .

When the engine speed reaches a predetermined speed at time T7, the control device 12 detects that the engine has started up from the output of the rotation sensor 2, and first stops energizing the relay 10 and opens the intake shutter 5. (see Figure 2 b), and at the same time the fourth
The accelerator opening signal is applied to reduce the fuel injection amount to the idle increase I/Q (see part D in Fig. 2 g), thereby reducing the engine speed to the idle speed (see Fig. 2 g) . When the engine reaches the idle speed at time T8, the control device 12 detects from the signal of the rotation sensor 2 that the engine has reached the idle speed, and applies a control signal to the actuator 8 of the exhaust shutter 6 to stop the exhaust shutter. 6 (see Figure 2 f). This increases the pressure in the exhaust passage, which acts as a load on the engine, increasing the amount of fuel injected.
Moreover, the temperature in the combustion chamber increases due to the high temperature exhaust gas, and a large amount of fuel is burnt well, so that the engine is quickly warmed up. When the warm-up is completed, the control device 12 detects this from the signal from the water temperature sensor 3, stops the control signal to the actuator 8, and opens the exhaust shutter 6.

The apparatus of this embodiment as described above can provide the following effects.

(i) After the first explosion of the engine, the fuel injection amount is immediately reduced to suppress the temperature drop in the combustion chamber caused by the heat of vaporization of the fuel (see B in Figure 2g). Compared to the case where the fuel injection amount is gradually reduced (see E in Fig. 2g), the ignition performance can be improved and the starting performance can be improved.

(ii) Furthermore, since the fuel injection amount is increased to the maximum injection amount after the engine has completely exploded, the engine can be quickly and reliably brought up to the specified rotation speed, compared to conventional control methods. This improves starting performance.

(iii) As a result of greatly improving engine startability, this device can guarantee startability even in diesel engines with low compression ratios.
This has the excellent effect of eliminating obstacles to the practical application of diesel engines with low compression ratios, ie, low fuel consumption.

(iv) Furthermore, since the engine can be brought up to a predetermined rotational speed in a short period of time after a complete explosion, fuel efficiency can be improved.

In the above embodiments, intake and exhaust shutters and air heaters are provided, but these are not necessarily required.

〔Effect of the invention〕

As described above, according to the fuel injection amount control device for a diesel engine according to the present invention, an electronically controlled fuel injection pump is provided, and the fuel injection amount is adjusted from the start of cranking of the engine to the first explosion to the starting supercharging amount. ,
The injection amount from the first explosion to the complete explosion is controlled to be less than the maximum injection amount during normal operation and more than the idle increase amount, and the rise area from the complete explosion to the predetermined rotation speed above the idle rotation speed is controlled to the above maximum injection amount. Therefore, startability can be greatly improved, which has the effect of improving the practicality of diesel engines with low compression ratios (low fuel consumption).

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a fuel injection amount control device for a diesel engine according to an embodiment of the present invention, and Fig. 2a
~g is the operation of the indicator lamp, air heater, and key switch, changes in engine speed,
FIG. 3 is a diagram showing a timing chart of the operation of the intake/exhaust shutters and changes in the amount of fuel injection. 1... Fuel injection pump, 2... Rotation sensor (starting state detection means), 4... Key switch (starting state detection means), 13... Alternator (starting state detection means), 12... Control device (starting injection amount control means).

Claims (1)

[Claims] 1. An electronically controlled fuel injection pump that adjusts the fuel injection amount, a starting state detection means that detects the starting state of the engine, and an output of the detection means that causes the fuel injection pump to adjust the fuel injection amount of the engine. From the start of cranking to the time of the first explosion, the starting supercharging amount is greater than the maximum injection amount during normal operation, and from the time of the first explosion to the time of complete explosion, the amount of injection is less than the maximum injection amount and more than the increase in idle amount, and the amount of fuel is increased to complete explosion. 1. A fuel injection amount control device for a diesel engine, comprising: starting injection amount control means for adjusting the injection amount to the maximum injection amount from the time when the engine reaches a predetermined rotational speed equal to or higher than the idle rotational speed.