JPS59153932A - Electronic control fuel injector - Google Patents

Abstract

PURPOSE:To enable accurate air-fuel ratio control by controlling the open/close time of fuel injection valve on the basis of pressure difference across valve seat of fuel injection valve, fuel weight flow operated on the basis of specific gravity of fuel to be fed and weight flow of suction air. CONSTITUTION:An air flow sensor 2 for detecting weight flow of suction air is provided at the upperstream of throttle valve 4 in a suction pipe 10 of internal- combustion engine while first and second pressure sensors 44, 48 for detecting the differential pressure across the valve seat of fuel injection valve are provided respectively in a fuel distribution chamber 28 at the upperstream of fuel injection valve 14 and assist air distribution chamber 20 at the tip of fuel injection valve 14. A microcomputor 56 will operate weight fuel flow on the basis of differential pressure across the valve seat of fuel injection valve 14, specific gravity sensor 40 in fuel tank 34, first temperature sensor 42 and detected level of fuel temperature sensor 46 fed to fuel injection valve 14 thus to control open/close time of fuel injection valve 14 from weight flow of suction air provided from the air flow sensor 2 to produce accurate air-fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection device, and more particularly to an electronically controlled fuel injection device having a function of atomizing fuel using assist air.

In conventional electronically controlled fuel injection systems, the basic fuel injection amount is completely determined based on the intake air amount detected by the air 70 sensor, and fuel is injected from the fuel injection valve at a constant low fuel pressure to adjust the air-fuel ratio of the mixture. is controlled so that the air-fuel ratio is the required air-fuel ratio. However, even though the fuel pressure is constant, the fuel pressure fluctuates considerably over a short period of time, causing the fuel injection amount to fluctuate between cycles, making it difficult to control the air-fuel ratio to a required level. For this reason, an 02 sensor is installed on the exhaust manifold to detect the residual oxygen concentration in the exhaust gas. Feedback control is performed based on the sensor output to achieve the required air-fuel ratio. Feedback control using this 02 sensor can control the air-fuel ratio of the air-fuel mixture to be close to the total stoichiometric air-fuel ratio, but it is not possible to control the air-fuel ratio to a required air-fuel ratio other than the stoichiometric air-fuel ratio, so there was a need for a new gas sensor. . In addition, since all fuel is injected at a constant low fuel pressure using a fuel injection valve with a constant static injection amount, a dynamic range of the injection amount of the fuel injection valve is required for high-output engines with large fluctuations in intake air amount. There was a problem in that the injection valve became thicker and the control method of the injection valve and the structure of the injection valve had to be changed.

one! In addition, in the conventional electronically controlled fuel injection device, the fuel 1
'A! , Assist air flows from the upstream side of the throttle valve into the slanted space at the tip of the I valve tip groove, and the difference in pressure between the pressure on the upstream side of the throttle valve and the pressure on the downstream side of the throttle valve causes fuel and assist air to flow from the orifice. and 'fc injection to completely atomize the fuel and improve combustion efficiency. However, in areas where the differential pressure is large at light loads or partial loads, assist air can fully increase the atomization efficiency, but at sieve loads or full loads, it is difficult to achieve atomization because the differential pressure is small. There was a problem.

Furthermore, during a transient period in which the engine load changes rapidly, a spike occurs only with the fuel injection amount calculated based on the air flow sensor output, which deteriorates the torque increase rate and deteriorates the engine response. The cause of this is the intake delay and fuel delay that occur during transient periods, and conventional electronically controlled fuel injection systems use asynchronous injection, which injects without synchronizing with the crank angle.However, asynchronous injection The problem was that matching the timing and injection amount was complicated.

The present invention was made to solve all of the above-mentioned problems, and an object of the present invention is to provide an electronically controlled fuel injection device that precisely controls fuel injection amount and fuel pressure.

In order to achieve all of the above objects, the present invention provides an air 70-sensor that detects the amount of intake air sucked into the engine by the total weight flow rate, and a space equipped with an orifice at the tip of the fuel injection valve from the upstream side of the throttle valve. Bypass passage that supplies air and fuel f that is supplied from the fuel tank to the fuel injection valve
At, a fuel flow control valve that adjusts the amount, a specific gravity sensor that detects the specific gravity of the fuel stored in the fuel tank, and a first sensor that detects the temperature of the fuel stored in the fuel tank.
a second temperature sensor that detects the temperature of the fuel supplied to the fuel injection valve, a first pressure sensor that detects the pressure of the fuel supplied to the fuel injection valve, and a tip of the fuel injection valve. a second pressure sensor that detects the pressure of the engine, a load detection means that detects the total load of the engine, and a pressure difference across the valve seat of the fuel injection valve that is calculated from the first pressure sensor output and the second pressure sensor output. a pressure difference calculation means for controlling the fuel flow control valve so that the pressure difference becomes a predetermined pressure difference, and a fuel pressure control means for fully controlling the fuel flow control valve so that the fuel pressure becomes high during high load, and a specific gravity sensor. , specific gravity calculation means for calculating the specific gravity of the fuel supplied to the fuel injection valve based on each output of the first temperature sensor and the second temperature sensor, and the pressure difference, the injection hole area of the fuel injection valve, and the fuel injection Fuel amount calculation means for calculating the weight flow rate of fuel based on the specific gravity of the fuel supplied to the valve; and fuel injection controlling the opening/closing time of the fuel injection valve based on the weight flow rate of the intake air amount and the weight flow rate of the fuel. This configuration includes a control means.

According to the above configuration of the present invention, since the fuel pressure is increased on the high load side, fuel atomization on the high load side is improved, fuel lag during transition on the high load side is eliminated, and fuel pressure on the high load side is increased. Since the fuel is injected at the same injection rate, knocking is prevented, and deposits on the injector can be removed since the high fuel pressure is used, and the fuel injector is controlled by the weight flow rate of intake air and fuel, so the gas sensor This is no longer necessary, and the effect is that the air-fuel ratio of the air-fuel mixture can be precisely controlled to a predetermined air-fuel ratio without correction even if the atmospheric pressure and temperature change.

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

FIG. 1 shows a simple embodiment of the present invention. On the downstream side of an air cleaner (not shown), there are several air flow sensors 2 for detecting intake air supplied to the engine in terms of quality flow rate. It is being This knee flow sensor 2 is equipped with a thin platinum wire that forms a bridge and is self-heated by supplying a constant voltage. - Since it is proportional to speed, the flow rate is detected from the unbalanced current of the bridge. On the downstream side of air flow sensor 2,
A throttle valve 4 is arranged to control the engine load by fully adjusting the amount of intake air. A linear throttle sensor 6 is connected to the throttle valve 4 to detect changes in the opening degree of the throttle valve over time and to detect whether or not the throttle valve is idling.

A surge tank 8 is arranged downstream of the throttle valve 4, and the surge tank 8 communicates with the combustion chamber of the engine via an intake manifold 10 and an intake port 12. A fuel injection valve 14 is attached to each branch pipe of the intake manifold 10. A space including the entire orifice 16 is formed at the tip of the fuel injection valve 14. This space is the unstair distribution room 20.
and communicates with the upstream side of the throttle valve 4 via a bypass passage 22. Further, an assist air control valve 24 is provided in the middle of the bypass passage 22, and the assist air control valve 24 is further connected to the surge tank 8 via an arrangement H26 (il-).

The fuel injection valve 14 is connected to the bottom of the fuel tank 34 via a fuel distribution chamber 28, a fuel flow path 30, and a fuel pump 32 driven by an electric motor or engine.

Between the fuel pump 32 and the fuel distribution chamber 28 in the fuel passage 30 is a fuel bypass passage 3 that returns fuel to the fuel tank 34.
6 is provided, and a linear solenoid type or linear motor type fuel flow control valve 38 is provided in the middle of this fuel bypass passage 36. Therefore, the fuel is in the fuel tank 34
By controlling the opening degree of the fuel flow control valve 38 and adjusting the 'fiS-' of the fuel that is supplied from the fuel pump 32 and the fuel distribution chamber 28 to the fuel injection valve 14 and returns to the fuel tank 34, Fuel pressure is controlled.

A first temperature sensor 40 that detects the temperature of the fuel in the fuel tank and a specific gravity sensor 42 that detects the specific gravity of the fuel in the fuel tank are attached so as to be in contact with the fuel in the fuel tank 34. Further, a first pressure sensor 44 made of a semiconductor or the like is attached to the fuel distribution chamber 28 to detect the pressure of the fuel supplied to the fuel injection valve 14. A pressure sensor 48 for detecting the pressure at the tip of the injection valve 14 is attached.

The distributor 54 has a first crank angle sensor 50 that outputs a pulse signal at the top dead center of a specific cylinder.
A second crank angle sensor 52 that outputs a pulse number (at every predetermined crank angle) is built-in.

First temperature sensor 401, specific gravity sensor 42, knee flow sensor 2, throttle sensor 5, second temperature sensor 4
6. First pressure sensor 44 and second pressure sensor 48
is connected to the input port of the microcomputer 56, and the first crank angle sensor 50 and the second crank angle sensor 52 are connected to the human powered boat via a waveform shaping circuit within the microcomputer 56. 1, it is connected to Microco24.

The microcomputer 56 mentioned above has +)-)゛J-only memory (ROM), random access memory 1 (R
AM), an analog-to-digital converter (ADC), and a microprocessing unit (MPU). Signals input from each sensor such as an air flow sensor, temperature sensor, and pressure sensor are input to the ADC, and instructions from the MPu are input to the ADC. It is sequentially converted into a binary signal according to □. The pulse signal from the second crank angle sensor is input to the human-powered boat via a waveform shaping circuit, and two communication signals representing one rotation number of the engine are formed from this pulse signal. The pulse signal from the first crank angle sensor is similarly input to the input port, and together with this pulse signal tS, an interrupt request signal for calculating the fuel injection pulse width, a fuel injection start signal, a cylinder discrimination signal, etc. It is used in the formation of In addition, a well-known fuel injection control circuit including a presettable down counter and a register is installed in the output boat.The output boat is equipped with a well-known fuel injection control circuit including a presettable down counter and a register. Forming a pulse signal and pulsing this injection -Q
are input into the fuel injection valve 14 sequentially or simultaneously to energize the injection valve. As a result, fuel is injected in an amount corresponding to the pulse width of the injection pulse signal. The ROM contains fuel pressure values or engine speed and load according to the engine speed and load (intake pressure, quality of intake air under standard atmospheric pressure per cylinder and one cycle, flow rate or injection pulse width). The fuel pressure values are stored in the form of a map. This fuel pressure value is determined by, for example, the differential pressure between the combustion air pressure and the assist air pressure.

The operation of this embodiment will be explained below. The assist air control valve 24 is controlled when the engine is cold, when idling after warming up, when under partial load, and the like. During cold idling, assist air is supplied to the space 18 via the bypass passage 22, and when fuel is injected from the fuel injection valve 14 at this time, it is atomized by the assist air. Furthermore, if the amount of intake air is insufficient, the assist air control valve 24 also injects the insufficient amount of air into the surge tank 8 according to a command from the microcomputer 56.

Next, the entire fuel pressure control routine will be explained using FIG. 2. First, in step 60, the engine speed, the intake air front G cL'c are read, and the fuel pressure value (set value) corresponding to this engine speed and intake air kGα is stored in all ROMs.
At the same time, the fuel pressure Pf and assist air pressure -P input from the pressure sensor and stored in the RAM are read from
Read a. In the next step 61, a pressure difference between the fuel pressure Pf and the assist air pressure Pa is played by the pressure difference play 1 means, and it is determined whether this pressure difference is equal to the fuel pressure value read from the ROM. If the pressure difference is equal to the fuel pressure value, the routine proceeds to the next routine; if the pressure difference is not equal to the fuel pressure value, the lifter of the fuel flow control valve 38 is moved in step 62', and feedback control is performed so that the pressure difference becomes the set value. do. This suppresses fluctuations in the amount of fuel 41 from cycle to cycle.

In addition, the fuel pressure changes depending on the engine speed and load, and the injection rate (unit time or (l-1:191 fuel amount per constant crank) changes. In other words, when the load is light, the fuel pressure is lowered and injection is performed. Even if the rate is lowered, atomization by assist air is improved.On the other hand, at high loads or full loads when atomization by assist air cannot be expected, fuel pressure?
By increasing it, the atomization rate can be improved. Furthermore, since the fuel injection valve has a static injection amount, it is controlled to increase the fuel pressure as the injection amount increases. By doing so, a large amount of fuel can be injected in a short period of time, and there is no need to expand the dynamic range of the fuel injection valve. Furthermore, the rate of change in the throttle opening with respect to time is determined based on the signal from the throttle sensor, and the fuel pressure is changed in accordance with this rate of change. In other words, if it is determined that the engine load is in a transient state such as an acceleration state where the engine load changes rapidly depending on the rate of change,
The fuel pressure is controlled to be high. As a result, the actual fuel injection rate is increased and lean spikes are prevented. In this case, by controlling the time to increase the fuel pressure,
Excessive fuel increase can also be completely prevented.

Next, the fuel injection routine will be explained with reference to FIG. First, in step 70'', the engine speed,
Intake air amount Gα, specific weight rf' detected by the specific gravity sensor 42 and stored in the RAM, fuel temperature T in the fuel tank input from the temperature sensor and stored in the RAM,
Fuel temperature TM near the injection valve seat and pressure difference Pf P
At the next step 72, the fuel injection M is calculated from the P9r required nitrous fuel ratio depending on the engine operating condition determined by the engine speed, etc., and the predetermined crank angle is reached.At this point, the fuel injection valve is fully controlled in step 73. Perform full fuel injection. That is, the air-fuel ratio is expressed as the ratio of the weight flow rate Gα of intake air to the flow rate Gf of fuel M, the weight flow rate Ga is determined from the air flow sensor output, and the weight flow rate Gf is calculated using the continuity theorem and Bernoulli's From the theorem, it can be expressed as the following formula.

Gf = μpfi Frado7 (1) where μ is the flow coefficient, F is the cross-sectional area of the injection hole of the fuel injector, 2 is the gravitational acceleration, and ΔPf is the pressure difference before and after the valve seat of the fuel injector (Pf - Pα) It is.

Therefore, in this embodiment, the accurate pressure difference ΔPf1 specific gravity γf
Since e is determined, the injection pulse width can be easily determined and accurate air-fuel ratio control can be realized.

Although the fuel flow control valve has been described with reference to an example in which it is provided in the fuel bypass flow path, it may be provided in the fuel distribution chamber from the viewpoint of simplification of design and responsiveness.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a flowchart showing a fuel pressure control routine, and FIG. 3 is a flowchart showing a fuel injection routine. 2... Air flow sensor, 6... Throttle sensor, 14... Fuel injection valve, 22... Bypass passage, 40.46... Temperature sensor, 42... Specific gravity sender, 44.48...・Pressure sensor. Agent Patent attorney Tatsuyuki Unuma (and 2 others) Figure 2 Figure 3

Claims (1)

[Claims] (1) An air flow sensor that detects the amount of intake air taken into the engine by weight flow rate, a bypass passage that supplies all the anost air from the upstream side of the throttle valve to the space with the orifice at the tip of the fuel injection valve, and the fuel tank. A fuel flow control valve that fully adjusts the fuel flow supplied to the fuel injection valve from the fuel injection valve, a specific gravity sensor that detects the specific gravity of the fuel stored in the fuel tank, and a specific gravity sensor that detects the temperature of the fuel stored in the fuel tank. a first temperature sensor that detects the entire temperature of the fuel supplied to the fuel injection valve;
a first pressure sensor that detects the pressure of fuel supplied to the fuel injection valve, a second pressure sensor that detects the pressure at the tip of the fuel injection valve, a load detection means that detects the load of the engine, and a first pressure sensor that detects the pressure of the fuel supplied to the fuel injection valve; pressure difference calculating means for calculating a pressure difference across the valve seat of the fuel injection valve from the output of the pressure sensor and the output of the second pressure sensor; and controlling a fuel flow control valve so that the pressure difference becomes a predetermined pressure difference. and a fuel pressure control means for controlling the fuel flow control valve so that the fuel pressure becomes high during high loads; a specific gravity calculation means for calculating the specific gravity of the fuel; a fuel amount calculation means for calculating the total weight flow rate of the fuel based on the pressure difference, the injection hole area of the fuel injection valve, and the specific gravity of the fuel supplied to the fuel injection valve; An electronically controlled fuel injection device including a fuel injection control means for controlling the opening/closing time of a fuel injection valve based on the weight flow rate of air amount and the weight flow rate of fuel.