JPS5965525A - Fuel injector for engine - Google Patents

Abstract

PURPOSE:To prevent generation of shock in case when injection form is switched, by controlling the injection amount by utilizing the demanded intake amount of an engine which is written previously into a map so as to be adapted for the operation state of the engine in the transient period of the injection state in which the demanded intake amount of the engine is sharply varied. CONSTITUTION:In a control circuit X, the loaded state of an engine is judged from each output of a throttle-valve opening sensor 15 and a crank-angle sensor 16, and each fuel injection valve 7 is controlled so that intermittent injection having an actual injection rate of 1/2 is carried-out in low load operation and the perfect injection having an actual injection rate of 1 is performed in high load operation. Opening and closing of a bypass valve 9 in a bypass passage 8 which makes a detour around a throttle valve 4 is properly controlled when injection form is switched, and the amount of intake air is accorded with a demanded intake amount. Consequently, each injection valve 7 is controlled according to the fuel injection amount determined on the basis of the output of each sensor 15, 16 in normal operation and according to the fuel injection amount read-out from a prescribed map on the basis of the output of each sensor 15, 16 when injection form is switched.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention changes the number of times fuel is injected into the cylinders of an engine during high-load operation that requires high output and during low-load operation that does not require high output, thereby reducing fuel consumption and reducing emissions. The present invention relates to a fuel injection device for an engine whose characteristics are improved.

Conventional examples of fuel injection devices that change the number of fuel injections to the engine according to the load condition of the engine include, for example, Japanese Patent Publication No. 47-42409, Japanese Patent Publication No. 46-34172, JP-A-52-1
The one shown in Japanese Patent No. 42132 is known.

By the way, in a fuel injection device that changes the number of fuel injections according to the engine load condition, when the number of injections is changed, that is, when the engine injection form is changed, the engine output is kept almost constant before and after the change. Therefore, it is necessary to maintain the required intake air amount and the required fuel injection amount, which change according to each injection form, quickly and accurately to prevent shocks from occurring during switching. For this reason, the present inventors provided a bypass valve in a bypass path that bypasses the throttle valve of the engine,
By quickly and accurately controlling the opening degree of this bypass valve according to the injection form, the intake air amount to the engine is corrected to match the engine's required intake air amount, and the fuel injection amount is A method was devised in which the corrected intake air amount is detected by an intake air amount detection device such as an air flow meter, and the air-fuel ratio is controlled to a predetermined air-fuel ratio based on this detected amount.

However, such an intake air amount detection device cannot fully follow the change in intake air amount when the intake air amount changes rapidly, such as during the transition period immediately after the injection form is switched (see Figure 4), and the device may not operate properly. A delay occurs, and as a result, an injection amount corresponding to an intake air amount that is different from the actual intake air amount is determined. Therefore, during the transition period immediately after switching the injection mode, it is necessary to use some means to compensate for the delay in the operation of the intake air amount detection device.

In view of the above-mentioned problems in engine fuel injection devices, the present invention improves the accuracy of fuel control during the transition period immediately after switching the injection mode, thereby preventing shock when switching the fuel injection mode and improving engine efficiency. The purpose of this invention is to provide a fuel injection device for an engine that is designed to improve combustion characteristics, exhaust characteristics, and fuel efficiency. A reference signal generation means for generating a reference signal, a load state detection means for detecting the load state of the engine, and an intake air amount for directly detecting the amount of intake air taken into the engine and outputting a signal proportional to the amount of intake air. a detection means, a rotation speed detection means for detecting the rotation speed of the engine, a sweetfish feed supply means for injecting fuel into the cylinders of the engine in response to first and third control signals of the control signal output means described below, and the above-mentioned control. A regulating valve drive means receives a second control signal from the signal output means and controls an air amount control valve that controls the amount of air taken into the engine; A first control signal that reduces the ratio of the number of injections to the number of reference signals during load operation compared to during high load operation, and a first control signal that reduces the ratio of the number of injections to the number of reference signals at the same time as the ratio of the number of injections to the number of reference signals changes. The second control signal for correcting the predetermined amount and the injection amount of fuel to be injected at one time are usually determined based on the output signal of the intake air amount detection means, while the ratio of the number of injections to the number of the reference signals changes. During the transition period, the third control signal is determined based on a set value given in advance for the engine operating state determined by the output signals of the load state detection means and the engine rotation speed detection means. The present invention is characterized in that a control signal output means is provided.

Hereinafter, the fuel injection device for an engine of the present invention will be explained based on the embodiment shown in FIGS. 1 to 6. FIG. It is shown. This fuel injection device
An air cleaner 6 is connected to an intake manifold 3 that supplies intake air to each cylinder 1, 1, etc. of the engine via an intake pipe 2.
and an air flow meter 5 for detecting the amount of intake air.

At a position near the intake pipe 2 at the joint between the intake manifold 3 and the intake pipe 2, a throttle valve 4 is attached which is interlocked with an accelerator pedal (not shown). The opening degree of the throttle valve 4 is detected by a throttle valve opening sensor 15, and is inputted to a control circuit X, which will be described later, as a factor for detecting the load state of the engine. Furthermore, a bypass passage 8 that bypasses the throttle valve 4 is provided between the intake pipe 2 and the intake manifold 3, and a bypass valve (air amount control valve) that opens and closes the bypass passage 8 is provided in the bypass passage 8. )9 is installed. This bypass valve 9 is controlled by a control circuit X.

On the other hand, fuel injection valves 7, 7, . . . are attached to branch passages 3a, 3a, . . . branched from the intake manifold 3, respectively. The fuel injection valves 7, 7... are controlled to open and close by a control circuit X described later, and a fuel supply pipe 10 connects each fuel injection valve 7, 7...
The fuel pumped through the fuel pump 13 is injected into each cylinder 1, 1, . . . . or,
A known pressure integrator (not shown) is disposed in the fuel return pipe 14 that connects the fuel supply pipe 10 and the fuel tank 11 to keep the fuel pressure in the fuel supply pipe 10 constant. Further, a crank angle sensor 16 is provided at a position facing the flywheel portion (not shown) of the engine as a reference signal generating means for detecting the crank angle of the engine crankshaft and generating a reference signal synchronized with the rotation of the engine. is installed, and the detection signal of the crank angle sensor 16 is inputted directly as a pulse signal, or converted to a voltage corresponding to the frequency of the pulse signal via the F/V converter 17, and inputted to the control circuit X. As will be described later, this is used as a factor for setting the injection amount, etc.

In addition, the above-mentioned crank angle sensor 16 and F/V converter 1
7 constitutes a rotation speed detection means for detecting the rotation speed of the engine.

When operating the engine under high load, this fuel injection device injects fuel into each cylinder from the fuel injection valves 7, 7, etc. by a standard number of injections corresponding to the standard number of injections synchronized with the rotation of the engine.
In other words, in a 4-stroke engine, fuel is injected only once during two rotations of the crankshaft (hereinafter referred to as full injection operation), and conversely, when operating the engine at low load, the number of injections is reduced from the above number of injections. Fuel injection is performed intermittently (hereinafter referred to as intermittent injection operation).

In the following, the fuel injection form will be expressed as the ratio of (engine reference number of injections) to (actual number of injections) (hereinafter referred to as the actual injection rate). For example, 4
In a cycle engine, when fuel is injected only once during four revolutions of the crankshaft, it is called intermittent injection with an actual injection rate of 1/2, and full injection where fuel is injected once every two revolutions of the crankshaft. In this case, the actual injection rate is 1. In this embodiment, the injection mode is switched between two modes: full injection with an actual injection rate of 1 and intermittent injection with an actual injection rate of 1/2.

When the injection form is switched according to a change in the load condition using the method described above, the bypass valve 9 is opened and closed as appropriate to match the amount of intake air taken into the engine with the amount of intake air required by the engine. For example, when the injection form shifts from full injection to intermittent injection, the amount of fuel injection per injection increases (
(described later), the intake air volume is increased to almost double, and conversely, when transitioning from intermittent injection to full injection, the intake air volume is reduced to almost half in response to a decrease in the amount of fuel injected per injection. In addition, the fuel injection amount is set to a predetermined air-fuel ratio based on the intake air amount detected by the airflow meter 5 during both full injection operation and intermittent injection operation, but especially when the injection form is switched. Immediately after the transition period, the intake air amount suddenly becomes segmented as shown by the chain line in FIG. 4, so that the air flow meter 5 is no longer able to follow the change in the intake air amount. For this reason, in the illustrated embodiment, during the transitional period when the air flow meter 5 is likely to be delayed in operation, as shown in FIG. The injection amount is controlled by In addition, this FIG. 4 shows the output curve of the air flow meter when the injection form shifts from intermittent injection to full injection.

Hereinafter, each of the above-mentioned control methods by the control circuit X will be explained with reference to the control circuit diagram shown in FIG. That is, a crank angle sensor 16 detects the crank angle of the engine crankshaft, a throttle valve opening sensor (load state detection means) 15 detects the load state of the engine, and directly detects the amount of intake air taken into the engine. an air flow meter (intake air amount detection means) 5 that outputs a signal proportional to the intake air amount; and an F/V converter 17 that receives the output of the crank angle sensor 16 and generates a detection signal corresponding to the rotation speed. Based on the detection results of these detection means, the control circuit X controls the fuel injection amount and intake air amount and controls the switching of the injection form.

Inside the control circuit An injection pulse width setting circuit 21 is incorporated, and the output of the air flow meter 5 (intake air amount: Q
) and the output (rotation speed: N) of the crank angle sensor 16 outputted via the F/V converter 17 are input to the first injection pulse width setting circuit 20.
At 0, a signal with a pulse width (time) proportional to Q/N is output, and based on this output signal, the drive circuit 24 controls the opening time of the injection valves 7, 7, etc., and injects a predetermined amount of fuel. (both during full injection and during intermittent injection).

On the other hand, during a transient period, the rotation signal output from the F/V converter 17 and the voltage signal from the throttle valve opening sensor 15 are input to the second injection pulse width setting circuit 21. In this second injection pulse width setting circuit 21, as shown in FIG. 6, the injection pulse width (opening time of the injection valve), each engine rotation speed, and each engine rotation speed are set in advance by experiments or the like to adapt to the operating conditions of each engine. The current engine speed and the injection pulse width corresponding to the throttle valve opening are read from the map 32 stored at the address corresponding to the throttle valve opening and input to the drive circuit 24 to control the fuel injection amount.

This switching between the injection amount control system during the steady state and the control system during the transient period is performed in conjunction with the injection mode switching operation.

When selecting the injection form, the area boundary line l0 of the injection form is set in advance in correspondence with the engine speed and throttle valve opening as shown in FIG. The part (shaded part) is an intermittent injection region, and the upper part is a full injection region, and the reference voltage generation circuit 26 receives a signal (a voltage signal corresponding to the engine rotation speed) input from the F/V converter 17. A voltage signal proportional to the throttle valve opening on the area boundary line 10 corresponding to this input signal is output. For example, if the engine speed input from the F/V converter 17 is n, the reference voltage generation circuit 26 generates a voltage proportional to the throttle valve opening E1 on the region boundary line 10 corresponding to the engine speed n. A signal is output.

Further, at the gate 27, a voltage signal input from the reference voltage generation circuit 26 (reference throttle valve opening corresponding to the engine speed: E1) and a voltage signal directly input from the throttle valve opening sensor 15 (current Throttle valve opening: E2) is compared and determined, and if E1>E2, it is an intermittent injection region, so a signal (L) indicating the intermittent region is output,
Conversely, if E1<E2, the entire injection region is reached, and therefore a signal (H) indicating the entire injection region is output. The output signal of this gate 27 is a switching control signal (third control signal) of the fuel control system.
As a result, a signal for setting the engine's actual injection rate is sent to the timer 23 (
The signal is input to the actual injection rate setting circuit 29 as a first control signal) and to the correction circuit 31 as an intake air amount correction signal (second control signal).

The actual injection rate setting circuit 29 sets the actual injection rate of the engine according to the output signal of the gate 27. For example, if the input signal is (
In H), since we are in the full injection region, the actual injection rate = 1, and if the input signal is (L), we are in the intermittent injection region, so the actual injection rate = 1/2 signal is sent to the injection pulse position setting circuit. 2
The injection pulse position setting circuit 28 receives this input signal and sets the injection pulse position on the reference pulse output from the crank angle sensor 16 in accordance with each actual injection rate. Therefore, fuel is reliably injected every reference number of times during full injection, and once every two reference times during intermittent injection.

On the other hand, when the output signal from the gate 27 changes from (L) to (H) or from (H) to (L), the switching circuit 22 is instantaneously activated via the timer 23, and the injection amount control system is kept constant. From the injection amount control by the first injection pulse width setting circuit 20 using the airflow meter 5 for only time (timer setting time) to the second injection pulse width setting circuit 2 using the map 32
1 map control. In addition, timer 23
After the set time has elapsed, the control system is automatically switched from map control to control using the air flow meter 5. Further, the set time of the timer 23 is set based on the followability recovery time of the air flow meter 5.

Furthermore, when switching the injection form, it is necessary to appropriately open and close the bypass valve 9 to increase or decrease the amount of intake air into the engine. This is controlled by the correction circuit 31.

That is, the opening degree of the bypass valve 9 at the time of full injection and at the time of intermittent injection is set in advance in correspondence with the opening degree of the throttle valve 4 as shown in the control curves l1 and l2 shown in FIG. The required opening of the bypass valve 9 is set according to the throttle angle input from the opening sensor 15 to the function voltage generation circuit 30. For example, when the throttle valve opening is the opening degree a, the opening degree of the bypass valve 9 is the opening degree x or the opening degree y. Further, the selection of the opening degree x or the opening degree y is made by the gate 27.
This is performed based on a signal inputted to the correction circuit 31 from the above. For example, when the input signal from the gate 27 is (H), the opening degree x is adopted because it is in the full injection operation region,
(L), the opening degree y is adopted because it is an intermittent injection region. In response to the control signal from the correction circuit 31, the drive circuit 25 controls the opening and closing of the bypass valve 9. Therefore, the required amount of intake air according to the injection form is accurately supplied to the engine.

Next, to explain the effects of the present invention, the engine fuel injection device of the present invention is an engine fuel injection device that changes the number of fuel injections according to the engine's required output. During the transition period of the injection form when the intake air amount suddenly changes, the fuel injection amount is controlled using the engine's required intake air amount written in the map in advance to adapt to the engine operating condition. This problem tends to occur when the fuel injection amount is controlled based on the intake air amount detected by a mechanically operated intake air amount detection means such as an air flow meter even during a transient period as in a conventional fuel injection device. It is possible to prevent deterioration in fuel control accuracy due to a delay in the operation of the intake air amount detection means,
This has the effect of preventing a shock when switching the fuel injection mode, and further improving the combustion characteristics, exhaust characteristics, or fuel efficiency of the engine.

[Brief explanation of the drawing]

1 is a system diagram of a fuel injection device according to an embodiment of the present invention, FIG. 2 is a control circuit diagram of the fuel injection device of FIG. 1, and FIG. 3 is a diagram showing a full injection operation region and an intermittent operation region, FIG. 4 is a diagram showing the characteristics of the air flow meter, FIG. 5 is a diagram showing the relative relationship between the throttle valve opening and the bypass valve opening, and FIG. 6 is a map. 1... Engine cylinder 4... Throttle valve 5... Air flow meter 7... Fuel injection valve 9... Bypass valve 15... Throttle valve Opening sensor 16...
・Crank angle sensor 17...F/V converter Applicant: Toyo Kogyo Co., Ltd. Agent Patent attorney: Hiroshi Ohama Time throttle valve opening

Claims (1)

[Claims] 1. A reference signal generating means that generates a reference signal synchronized with engine rotation, a load state detecting means that detects the load state of the engine, and a means that directly detects the amount of intake air taken into the engine and is proportional to the amount of intake air. an intake air amount detection means for outputting a signal, a rotation speed detection means for detecting the rotation speed of the engine, and in response to first and third control signals of the control signal output means described later, fuel is injected and supplied to the cylinders of the engine. A fuel supply means, a regulating valve driving means for controlling an air amount regulating valve that controls the amount of intake air taken into the engine in response to a second control signal from the control signal outputting means, and inputting output signals from each of the above means. When the engine load state is low load operation, a first control signal that reduces the ratio of the number of injections to the number of reference signals than during high load operation, and a first control signal that simultaneously controls the engine when the ratio of the number of injections to the number of reference signals changes. The second control signal for correcting the amount of intake air taken in by a predetermined amount and the injection amount of fuel injected at one time are normally determined based on the output signal of the intake air amount detection means. The transition period during which the ratio of the number of injections to the number of injections changes is determined based on a preset value given for the engine operating state determined by the output signals of the load state detection means and the engine rotation speed detection means. 1. A fuel injection device for an engine, comprising: a third control signal that outputs a third control signal; and a control signal output means that outputs a third control signal.