JPH0137155Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a direct injection gasoline engine.

As a conventional direct injection gasoline engine,
For example, there is one described in SAEpaper No. 720052.
As shown in FIG. 1, this direct injection gasoline engine has a combustion chamber 1 consisting of a cylinder block 2, a piston 3 slidably housed in the cylinder block 2, and a cylinder head fixed to the upper end of the cylinder block 2. 4. Attached to the cylinder head 4 are a spark plug 5 whose tip protrudes into the combustion chamber 1, and a fuel injection nozzle 6 whose injection hole faces the combustion chamber 1. The fuel injection nozzle 6 includes a valve (not shown) and a spring (not shown) that biases the valve so that the valve closes the nozzle hole. An external plunger type fuel pump is connected. Therefore, when a pressure higher than the spring pressure (usually 50 kg/cm ² or higher) is applied to the fuel from the fuel pump, the valve opens and the fuel injection nozzle 6 injects the fuel into the combustion chamber 1.

In such a conventional direct injection gasoline engine, fuel supplied from the fuel pump during the compression stroke is injected into the combustion chamber 1 from the fuel injection nozzle 6, but the injection amount and injection timing of the fuel injected at this time are is controlled by this fuel pump. That is, as mentioned above, the fuel supplied from the fuel pump to the fuel injection nozzle 6 has a pressure higher than the spring pressure (solid line (X in FIG. 2)).
As shown in , it is usually set at 50Kg/cm ² or more. ) is added, and by adjusting this pressure, the fuel injection amount (pressurization time) and injection timing (when pressurization starts and when pressurization ends) are controlled. The fuel directly injected into the combustion chamber 1 in this manner is mixed with the air taken into the combustion chamber 1, stirred, and ignited by the spark plug 5, resulting in explosive combustion.

However, in such conventional direct injection gasoline engines, the timing and amount of fuel injection are controlled by applying pressure from the fuel pump to the fuel that resists the spring pressure of the fuel injection nozzle. Because this pressure was set at a high pressure of 50 kg/cm2 or ^more in relation to the combustion chamber pressure (see Figure 2), the control range for fuel injection timing was narrow and it was difficult to properly inject fuel according to the engine load. There was a problem that the timing could not be controlled and combustion efficiency deteriorated. In addition, the injection system, such as the fuel injection nozzle and fuel pump, has become larger and more complex, resulting in higher production costs.

Furthermore, conventional direct-injection gasoline engines have only used a method in which fuel is injected directly from the fuel injection nozzle into the combustion chamber, so when starting, especially when the engine is cold, there is a possibility that there will be no fuel remaining. Fogging occurs, which adheres to the spark plug as it burns, or a rich air-fuel mixture during startup adheres to the fuel injection nozzle and accumulates as carbon. the result,
There were problems such as deterioration of combustion efficiency and corrosion of the fuel injection nozzle.

This idea was created by focusing on these conventional problems, and includes an engine load detection means that detects the engine load and outputs a signal according to the load, and a water temperature sensor that detects the engine water temperature. ,
A first nozzle injects fuel into the combustion chamber of the engine, a second nozzle injects fuel into the intake passage of the engine, and switching between the first nozzle and the second nozzle is performed based on a signal from a water temperature sensor. a control unit that outputs a pulse signal that commands the injection timing and injection period of fuel from the first nozzle or the second nozzle based on the signal from the detection means, and when the water temperature of the engine is below a predetermined temperature, Fuel is injected from the nozzle, and when the water temperature of the engine exceeds a predetermined temperature, the fuel is injected from the first nozzle, and the injection pressure of the first nozzle is set to be below the maximum cylinder pressure during motoring operation of the engine. It is an object of the present invention to solve the above problems by providing a direct injection gasoline engine.

This invention will be explained below based on the drawings.

FIG. 3 is a diagram showing an embodiment of this invention.

First, to explain the structure, numeral 11 is a cylinder block having a cylinder hole, and a piston 12 is slidably inserted into the cylinder hole.
A cylinder head 13 is fixed to the upper end of the cylinder block 11 via a gasket so as to close the cylinder hole.
defines a combustion chamber 14. Cylinder head 1
A spark plug 15 is attached to the cylinder head 13 so that its tip protrudes into the combustion chamber 14, and a first nozzle 16 is attached to the cylinder head 13 so that its injection hole faces the combustion chamber 14. There is.
This first nozzle 16 is a so-called outward opening type nozzle attached to each cylinder.
The valve 6 is always biased by a spring in the direction of closing the nozzle hole, and the nozzle hole is opened and closed by an electronic opening/closing means (for example, the main magnetic pole part is excited by a coil, and a The nozzle hole is opened by the main magnetic pole attracting the armature). The injection pressure of this first nozzle 16 is a relatively low pressure, for example, 15 kg/
^cm2 is set. The first nozzle 16 is connected to a control unit 17. Further, a water temperature sensor 19 is attached to the cylinder block 11 to detect the temperature of cooling water in the water jacket 18, and the water temperature sensor 19 is connected to the control unit 17. Furthermore, an exhaust manifold for discharging burned gas in the combustion chamber 14 via an exhaust passage, and an intake manifold 22 for feeding air into the combustion chamber 14 via an intake passage 21 are attached to the cylinder head 13. The exhaust manifold 20 and intake manifold 22 are communicated via an EGR valve 23. The EGR valve 23 is connected to a VCM valve 24 having a built-in solenoid valve section, and the VCM valve 24 is communicated with a vacuum pump 25 and also connected to the control unit 17. When the VCM valve 24 is energized from the control unit 17, the VCM
The solenoid valve part of the valve 24 opens, and the negative pressure of the vacuum pump 25 acts on the EGR valve 23.
The EGR passage of the EGR valve 23 opens. When the EGR passage is opened, burned gas in the exhaust manifold 20 is circulated to the intake manifold 22.
The intake manifold 22 is connected to an air cleaner 29 via an intake passage 28 in which a throttle valve 26 and an air flow meter 27 are provided.
A second nozzle 30 is attached to inject fuel into the intake passage 21 via the manifold 22.

The control unit 17 is constructed as shown in FIG. The output is converted into a digital signal by an analog-to-digital converter (hereinafter referred to as AD converter) 32 and sent to the I/D converter.
It is input to o33. In addition, digital signals from various sensors and detection means are input to the I/o 33, and the I/o 33 is connected to the CPU 34 and ROM 33.
It is connected to the RAM 36 via a data bus 37, a control bus 38, and an address bus 39, and outputs signals to the first nozzle 16, second nozzle 30, VCM valve 24, and spark plug 15. Based on the signal from the I/O 33 and the data in the ROM 35 and RAM 36, the CPU 34 calculates the fuel injection timing, fuel injection period, and ignition timing, and calculates the EGR amount, EGR timing, and the first nozzle 1.
6 and the second nozzle 30. FIG. 5 is a block diagram showing the operation of this control unit 17.

In FIG. 5, 41 is a valve opening detection means (engine load detection means) that detects the valve opening of the throttle valve 26 that is linked to the accelerator pedal and outputs a signal proportional to the valve opening of the throttle valve 26. , 42 is an engine rotation speed detection means (engine load detection means) connected to a crank angle sensor or distributor 43 (not shown), which detects a 2° signal of the crank angle and outputs a signal proportional to the engine rotation speed. 44 is a piston position detection means that similarly detects a 180° crank angle signal and outputs a signal indicating the position of the piston 12, and 45 similarly detects a 720° crank angle signal and detects which of the plurality of cylinders. It is a cylinder discriminating means that outputs a signal for discriminating which cylinder a signal belongs to. 46 is a cooling water temperature detection means connected to the water temperature sensor 19 and outputs a signal proportional to the cooling water temperature, and 47 is a battery voltage detection means that detects battery voltage and outputs a signal proportional to the battery voltage. 48 is a vehicle speed detection means for detecting the vehicle speed and outputting a signal proportional to the vehicle speed;
is a start switch that is connected to the ignition switch and outputs a signal indicating that the ignition key is in the start position. 50 is a gear position detection means that detects the gear position of the transmission and outputs a signal indicating the gear position (for example, a pulse signal at a predetermined interval when the transmission is in neutral); 51 indicates whether the engine is in an idle state; The idle switch detects whether the throttle valve 26 is fully closed or not, and outputs a signal indicating that the throttle valve 26 is in the idle state. 52 is a knock state detection means for detecting whether or not the engine is in a knock state and outputs a predetermined signal when the engine is in the knock state; 53 is connected to each of the above-mentioned detection means and switches and detects each information. It is a sensor. 54 is a nozzle switching circuit connected to the cooling water temperature detection means 46, and when the input signal from the cooling water temperature detection means 46 indicates that the temperature is below a predetermined temperature (for example, 80°C),
When the circuit of the second nozzle 30 is opened and it is shown that the predetermined temperature has been exceeded, the second nozzle 30 is connected to the first nozzle 1.
Switch to 6. 55 is the control unit 17
The basic injection amount calculation circuit 55 receives a signal from the valve opening detection means (engine load detection means) 41 and a signal from the engine rotation speed detection means (engine load detection means) 42. The basic injection amount calculation circuit 55 calculates and outputs the basic injection amount from these signals, that is, signals corresponding to the engine load and data stored in advance in the ROM 35 of the control unit 17. . The output signal of this basic injection amount calculation circuit 55 is transmitted to the ignition timing calculation circuit 56,
The signal is inputted to the injection end timing calculation circuit 57, the corrected injection amount calculation circuit 58, and the EGR amount calculation circuit 59, and the injection end timing calculation circuit 57 is further inputted with a signal from the engine rotation speed detection means 42. This injection end timing calculation circuit 57 calculates and outputs the injection end timing from data stored in advance in the ROM 35 of the control unit 17 using the engine rotation speed and basic injection amount as control factors, and calculates the injection end timing. The output signal of the circuit 57 is input to a corrected injection end timing calculation circuit 60. Signals from the cooling water temperature detection means 46, the start switch 49, the gear position detection means 50, and the idle switch 51 are input to the corrected injection end timing calculation circuit 60. It is determined whether to inject into the intake passage 21 or into the combustion chamber 14 based on the signal from the water temperature detection means 46, and then the injection end timing calculation circuit 57 calculates the injection using these signals as correction factors. At the end of the period, ROM35
The optimal injection end timing is calculated and output by modifying the data stored in the internal memory. The corrected injection amount calculation circuit 58 to which the signal from the basic injection amount calculation circuit 55 is inputted further includes a cooling water temperature detection means 46, a battery voltage detection means 47, a vehicle speed detection means 48, a start switch 49, and a gear position. Signals from the detection means 50 and the idle switch 51 are input, and the corrected injection amount calculation circuit 5
8 uses these signals as correction factors for the basic injection amount.
The basic injection amount is corrected from data stored in advance in the ROM 35, and the optimum injection amount is output as a digital signal. Corrected injection amount calculation circuit 58
The output signal of is input to the injection period calculation circuit 61, and the output signal of the corrected injection end timing calculation circuit 60 is further input to the injection period calculation circuit 61. The injection period calculation circuit 61 also receives the corrected injection end timing, corrected injection amount, and data stored in advance in the ROM 35 (for example, the fuel injection performance of the first nozzle 16 according to the pressure state in the combustion chamber 14). The injection period is calculated and output. The output signal of the injection period calculation circuit 61 is input to the fuel injection command circuit 62 and the injection start timing calculation circuit 63, and the injection start timing calculation circuit 63 further receives the signal from the corrected injection end timing calculation circuit 60 and the injection start timing calculation circuit 63. Signals from engine speed detection means 42, piston position detection means 44, and cylinder discrimination means 45 are input. This injection start timing calculation circuit 6
3 calculates the optimum injection start timing from data previously stored in the ROM 35 based on these signals and outputs it to the fuel injection command circuit 62.

On the other hand, the ignition timing calculation circuit 56, into which the signal from the basic injection amount calculation circuit 55 is inputted, further receives the signal from the engine rotation speed detection means 42, and the ignition timing calculation circuit 56
calculates the ignition timing from data previously stored in the ROM 35 based on these signals and outputs it to the corrected ignition timing calculation circuit 64. The correction ignition timing calculation circuit 64 also receives signals from the cooling water temperature detection means 46, the start switch 49, the gear position detection means 50, the idle switch 51, and the knock state detection means 52. Based on these signals, the ignition timing calculation circuit 64 calculates the optimum ignition timing from data previously stored in the ROM 35 and outputs it to the ignition timing command circuit 65.

Furthermore, the EGR amount calculation circuit 59 to which the signal from the basic injection amount calculation circuit 55 is input,
Furthermore, signals from the engine speed detection means 42 are inputted, and based on these signals, the EGR amount calculation circuit 59 calculates the basic EGR amount from data stored in advance in the ROM 35, that is, the schematic engine diagram shown in the figure. The amount of gas circulating from the exhaust manifold 20 to the intake manifold 22 shown in the figure is calculated and output to the corrected EGR amount calculation circuit 66. Modified EGR amount calculation circuit 66
Further, the cooling water temperature detection means 46, a battery voltage detection circuit 47, a start switch 49,
Signals from the gear position detection means 50, the idle switch 51, and the knock state detection means 52 are input, and the corrected EGR amount calculation circuit 66 calculates an appropriate amount from the data previously stored in the ROM 35 based on these signals. The EGR amount is calculated and output as a digital signal to the EGR amount command circuit 67.

Note that these nozzle switching circuit 54, basic injection amount calculation circuit 55, ignition timing calculation circuit 56, injection end timing calculation circuit 57, corrected injection amount calculation circuit 58,
EGR amount calculation circuit 59, corrected injection end timing calculation circuit 60, injection period calculation circuit 61, fuel injection command circuit 62, injection start timing calculation circuit 63, corrected ignition timing calculation circuit 64, ignition timing command circuit 65, modification
EGR amount calculation circuit 66 and EGR amount command circuit 67
constitutes a control unit 17 as a whole.

The fuel injection command circuit 62 of this control unit 17 controls the first nozzle 16 and the second nozzle 30.
The first injection is connected to the
A pulse signal is output to the nozzle 16 or the second nozzle 30. First nozzle 16 or second nozzle 30
The valve is opened only during the period when the pulse signal is input, and fuel is injected into the intake passage 21 or the combustion chamber 14. Further, the ignition timing command circuit 65 is connected to the power transistor 68, and the ignition timing command circuit 65 outputs a control signal to the power transistor 68 at the optimum ignition timing calculated as described above. The power transistor 68 is the ignition coil 69
The ignition plug 15 is connected to the ignition plug 15 via the distributor 43 and the ignition timing command circuit 65, and the ignition plug 15 blows an ignition spark only when the control signal is outputted from the ignition timing command circuit 65. Further, the EGR amount command circuit 67 sends a signal (optimal timing and optimum period signal) for controlling the optimum EGR amount calculated as described above to the VCM valve 24.
Output to. When this signal is input, the VCM valve 24 opens the built-in solenoid valve and guides the negative pressure of the vacuum pump 25 to the EGR valve 23.
The EGR passage of the EGR valve 23 is opened to circulate the gas in the exhaust manifold 20 to the intake manifold 22.

Next, the effect will be explained.

First, the basic fuel injection amount is calculated based on the magnitude of the engine load. That is, the basic injection amount calculation circuit 55 receives signals from the engine rotation speed detection means 42 and the valve opening detection means 41 and the ROM 35.
The basic injection amount is calculated from the data. Once the basic injection amount is determined, the basic injection end timing is calculated by the injection end timing calculation circuit 57 from the basic injection amount, engine speed, and data in the ROM 35.

The basic injection amount and basic injection end timing determined in this way are modified depending on the engine condition, vehicle driving condition, etc. in order to make combustion more efficient.

First, when starting the engine, the rate of increase in the basic injection amount changes with respect to changes in the cooling water temperature, as shown in FIG. 6, for example. In the case of FIG. 6, when the cooling water temperature exceeds 10°C, the basic injection amount is not corrected, but when the temperature is below 10°C, for example, at -20°C, the amount is increased by 4 to 10 times. When starting such an engine,
The output of the nozzle switching circuit 54, into which the signal from the cooling water temperature detection means 46 is input, instructs the second nozzle 30 to eject, and similarly, the signal from the cooling water temperature detection means 946 is input. The corrected injection end timing calculation circuit 60 corrects the injection end timing to an injection timing suitable for injection within the intake passage 21. An injection period is calculated from the corrected injection amount and corrected injection end time, and an injection start time is calculated from this injection period and the corrected injection end time. These injection period and start timing are outputted from the fuel injection command circuit 62 to the second nozzle 30 as pulses.

On the other hand, the ignition timing is first determined based on the engine speed and the base injection amount, and then, as described above, it is modified according to the conditions of the vehicle and the engine to determine the appropriate ignition timing. This determination is made by the ignition timing calculation circuit 56 and the corrected ignition timing calculation circuit 64 from the data in the ROM 35, as described above, and the results of this determination are sent from the ignition timing command circuit 65 to the power transistor 68, the ignition coil 69, and the distributor. The signal is transmitted to the spark plug 15 via the user 43. In this way, by providing the ignition timing according to the state of the engine, etc., the combustion efficiency of the engine can be improved.

Furthermore, since EGR is unnecessary when starting the engine, the amount of EGR is zero.

Second, after starting the engine, for example,
As shown in FIG. 7, the rate of increase in the basic injection amount changes as the cooling water temperature changes. In the case of Figure 7, when the cooling water temperature exceeds 80°C, the basic injection amount is not corrected by the cooling water temperature, but when the cooling water temperature is below 80°C, for example, at -20°C, the basic injection amount is adjusted by 4 to 10 times. At 40°C, the amount increases by about 2 to 6 times. Further, when the cooling water temperature is 80° C. or lower, the fuel is injected from the second nozzle 30 into the intake passage 21, so the injection end timing is corrected in the same manner as described above.

Furthermore, when the cooling water temperature exceeds 80° C., the nozzle switching circuit 54 switches from the second nozzle 30 to the first nozzle 16, and accordingly, the injection end timing is significantly modified. That is, the first nozzle 16
As mentioned above, the injection pressure is lower than the maximum pressure during motoring of the combustion chamber 14, and therefore, the injection end timing is such that the fuel injection is completed when the pressure inside the combustion chamber 14 is relatively low. It will be amended to do so. An injection period is calculated from the corrected injection end time and the corrected injection amount calculated in this way, and an injection start time is calculated from this injection period and the corrected injection end time. These injection period and injection start timing are output as pulse signals from the fuel injection command circuit 62 to the first nozzle 16, and the first nozzle 16 injects fuel into the combustion chamber 14 only while this pulse signal is input. In this situation, for example, as shown in FIG. 8, the injection start time becomes earlier and the injection time becomes longer depending on the engine load. This state is expressed in relation to the pressure inside the combustion chamber 14 as shown in FIG. 2, where line Y shows the injection pressure of the first nozzle 16, and line Z shows the pressure in the combustion chamber 1 during motoring.
It shows the pressure change within 4. In this way, the combustion efficiency of the engine can be improved by making the fuel injection timing and injection period (injection amount) appropriate according to the engine load, cooling water temperature, vehicle driving condition, etc. Also, a second nozzle 30 injects fuel into the intake passage 21 depending on the cooling water temperature.
In addition to switching between the nozzle 16 that injects fuel into the combustion chamber 14, it is also possible to control the fuel injection amount and injection timing to appropriate values at the same time. It is possible to prevent the concentrated air-fuel mixture from adhering to the first nozzle 16 and depositing it as carbon.

On the other hand, as described above, the ignition timing is given according to the state of the engine and the like.

Furthermore, the EGR amount is first determined based on the engine rotation speed and the basic injection amount, and then modified according to the state of the vehicle and engine to determine an appropriate EGR amount. This determination is made by the EGR amount calculation circuit 5.
9 and the corrected EGR amount calculation circuit 66 perform this determination based on the data in the ROM 35, and the result of this determination is transmitted from the EGR amount command circuit 67 to the VCM valve 24.
As mentioned above, the VCM valve 24 controls the amount of recirculation of exhaust gas according to the above determination, thereby lowering the combustion temperature depending on the engine condition and operating condition, and reducing the amount of NOx emissions. can be reduced.

As explained above, according to this idea,
A direct injection gasoline engine consists of an engine load detection means that detects the engine load and outputs a signal according to the load, a water temperature sensor that detects the engine water temperature, and an injector that injects fuel into the combustion chamber of the engine. A first nozzle that injects fuel into the intake passage of the engine, a second nozzle that injects fuel into the intake passage of the engine, and switching between the first nozzle and the second nozzle is performed by a signal from a water temperature sensor, and a signal from an engine load detection means is used to switch between the first nozzle and the second nozzle. a control unit that outputs a pulse signal that commands the injection timing and injection period of fuel from the nozzle or the second nozzle, and when the water temperature of the engine is below a predetermined temperature, the fuel is injected from the second nozzle, and the engine When the water temperature of the engine exceeds a predetermined temperature, fuel is injected from the first nozzle, and the injection pressure of this first nozzle is set below the maximum cylinder pressure during motoring operation of the engine. During warm-up operation, fuel can be injected into the intake passage, and after warm-up, fuel can be injected directly into the combustion chamber, and the fuel injection timing and injection period can be controlled according to the engine load condition. I can do it. Furthermore, the injection pressure of the fuel injection nozzle can be lowered. Therefore, it is possible to prevent unburned fuel from adhering to the ignition plug during engine startup or warm-up, causing so-called fog, and to prevent a rich mixture from adhering to the fuel injection nozzle and depositing it as carbon. It is possible to obtain the effect that the combustion efficiency of the engine can be improved. Furthermore, the fuel injection nozzle can be made smaller and lighter, and the production cost of the fuel injection nozzle can be reduced.

In addition to the above-mentioned common effects, the embodiments described above have the following advantages:
Furthermore, the following effects can be obtained. In other words, it is possible to control the appropriate fuel injection timing and fuel injection amount according to the engine condition, especially the cooling water temperature and the vehicle driving condition, and also to control the appropriate ignition timing and EGR.
The amount of NOx can be controlled, further improving engine combustion efficiency and reducing NOx emissions.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view showing a conventional direct injection gasoline engine, and Figure 2 shows the fuel injection pressure and injection timing of the conventional direct injection gasoline engine and the direct injection gasoline engine of this invention. Figures 3 to 8 are diagrams showing an embodiment of the direct injection gasoline engine of this invention, and Figure 3 is a schematic configuration diagram thereof;
Fig. 4 is a schematic configuration diagram of the control unit, Fig. 5 is a functional explanatory diagram focusing on the control unit, and Fig. 6 is an explanatory diagram showing the relationship between engine cooling water temperature and fuel increase rate at the time of engine startup. FIG. 7 is an explanatory diagram showing the relationship between the engine cooling water temperature and the fuel increase rate after the engine is started, and FIG. 8 is an explanatory diagram showing the relationship between the engine load and fuel injection. 14... Combustion chamber, 16... First nozzle, 17...
...Control unit, 19...Water temperature sensor,
21...Intake path, 30...Second nozzle, 41...
Valve opening detection means (engine load detection means),
42...Engine rotation speed detection means (engine load detection means), 54...Nozzle switching circuit.

Claims (1)

[Scope of utility model registration request] An engine load detection means that detects the load on the engine and outputs a signal according to the load, a water temperature sensor that detects the water temperature of the engine, a first nozzle that injects fuel into the combustion chamber of the engine, and an intake path of the engine. A second nozzle injects fuel at the same time, and a signal from the water temperature sensor switches between the first and second nozzles, and a signal from the engine load detection means determines when to inject fuel from the first or second nozzle. and a control unit that outputs a pulse signal instructing the injection period and the injection period,
When the engine water temperature is below a predetermined temperature, fuel is injected from the second nozzle, and when the engine water temperature exceeds the predetermined temperature, fuel is injected from the first nozzle, and the injection pressure of this first nozzle is applied to the motor of the engine. A direct injection gasoline engine characterized by setting the cylinder pressure below the maximum cylinder pressure during ring operation.