JPH045817B2 - - Google Patents

Description

Detailed Description of the Invention <Technical Field> The present invention relates to a fuel supply device for an internal combustion engine, and in particular, to a device having a function of stopping the supply of fuel to the engine when the engine decelerates, the present invention relates to a fuel supply device for an internal combustion engine, and in particular to a device having a function of stopping the supply of fuel to the engine when the engine is decelerated. The present invention relates to a fuel supply device that can be appropriately controlled.

<Prior art> Conventionally, in internal combustion engines for vehicles, when the engine speed shifts to a deceleration state at a set value (fuel cutoff determination speed) or higher, the fuel supply is cut off and the deceleration state ends. A device is known in which fuel supply is resumed when the engine rotational speed drops to a fuel supply restart rotational speed (hereinafter referred to as recovery rotational speed) that is set smaller than the fuel cut determination rotational speed.

In addition, sufficient fuel savings can be obtained when the engine speed slowly drops while being driven from the vehicle side under engine braking conditions, and it is also effective when the engine speed drops rapidly with no load or after a sudden braking. In order to avoid the risk of engine stalling when the vehicle is stopped due to a collision, the recovery rotation speed is set according to the deceleration of the engine.
Proposed in No. 107927.

However, in such conventional fuel supply systems, the recovery rotation speed according to the deceleration of the engine was set in experiments to a value that would prevent engine stalling, which not only caused problems with the accuracy of the experiments but also caused problems. , a huge amount of experimentation is required, in-vehicle experiments are also essential, and furthermore, there is no theoretical support and a large safety factor is required, so there is the problem that sufficient fuel savings cannot necessarily be achieved. It was hot.

<Purpose of the Invention> In view of these conventional problems, the present invention is designed to appropriately set the recovery rotation speed according to the deceleration of the engine without conducting extensive experiments, and to set the recovery rotation speed to the maximum without fear of engine stalling. The purpose is to obtain a limited fuel consumption saving effect.

<Summary of the invention> For this reason, the present invention sets the lowest rotational speed at which the engine rotates without stalling as the first rotational speed N ₁ ,
From the engine deceleration N〓, calculate the second rotation speed N2 at which the first explosion after recovery occurs before the engine rotation speed drops to the first rotation speed _N1 , and calculate this second rotation speed _N2 . Recover rotation speed Nr based on rotation speed N ₂
It is designed to set .

To explain in more detail, the engine has a minimum rotational speed Nid that allows self-sustaining operation, which can be easily determined through experiments, so this is set as the first rotational speed N ₁ (=
Nid). Or by adding a small value to Nid, the first
Set the rotation speed _N1 .

In addition, when the fuel supply is restarted from a state where the fuel supply has been stopped, the fuel must be sucked into a certain cylinder and the cylinder must go into the explosion stroke before the first explosion after recovery, and the crank The shaft must rotate by a predetermined rotation angle θn.

Therefore, if fuel supply is started when the engine rotational speed is Ninj, the rotational speed Np at which the first explosion occurs can be found from the following equations (1) and (2).

Np=Ninj+∫ ^t _p N〓dt ……(1) θn=∫ ^t _p (Ninj+∫ ^t _p N〓dt) dt ……(2) Here, the first explosion rotation speed Np is the first rotation speed N ₁ (=
Nid), the engine will not stall.

Therefore, the second rotation speed _{N 2 (} =
Ninj), and the recovery rotation speed Nr is the second rotation speed.
If it is set to N2 _or more, engine stalling due to fuel cut will not occur. As a result, precise control becomes possible without extensive experimentation.

Therefore, the present invention, as shown in FIG.
Means for detecting engine rotation speed N and engine deceleration
a means for detecting N〓, and a crankshaft of the engine rotates a predetermined number of times from the deceleration N〓 of the engine until the number of revolutions of the engine decreases to a first predetermined number of revolutions _N1 at the deceleration N〓. means for setting a recovery rotation speed Nr based on a second rotation speed _N2 that rotates by an angle θn;
The apparatus includes means for comparing the engine rotational speed N and the recovery rotational speed Nr during fuel supply stop during deceleration and restarting the fuel supply when N≦Nr.

Note that the calculation formula for the second rotation speed N ₂ is determined as follows.

In the above equations (1) and (2), Np=N ₁ and Ninj=N ₂
Then, N ₁ = N ₂ +∫ ^t _p N〓dt ……(3) θn＝∫ ^t _p (N ₂ +∫ ^t _p N〓dt) dt ……(4) Equations (3) and (4) If N〓=constant, then N ₁ =N ₂ +N〓t ……(5) θn=∫ ^t _p (N ₂ +N〓t)dt =N ₂ t+1/2N〓t ² ……(6) ( 5), by eliminating t from equations (6), N ₂ = √ ₁ ² −2 Also, the second rotation speed N ₂ is calculated from the deceleration N〓 in the program, and the recovery rotation is calculated based on this. The number Nr may be set, or it may be calculated in advance and stored as table data, and the second rotation speed _N2 can be searched from the deceleration N〓, and then the recovery rotation speed Nr can be set based on this. You can also do this.

<Example> Examples of the present invention will be described below.

FIG. 2 shows a first embodiment.

1 is an engine, 2 is an intake pipe, 3 is a throttle valve provided in the intake pipe 2, 4 is an electromagnetic fuel injection valve that injects and supplies fuel to the engine 1, and 5 is a fuel injection valve that injects fuel from a fuel pump (not shown). This is a fuel pipe that supplies fuel to the fuel injection valve 4. 6 is the amplifier, fuel injection valve 4
Supplies driving power to the 7 is an air flow meter that measures the flow rate of intake air flowing through the intake pipe 2; 8 is an idle switch that detects the fully closed state of the throttle valve 3; and 9 is a crank that generates a pulse signal in accordance with the rotation of the crankshaft of the engine 1. It is an angle sensor.

10 is a microcomputer.

To explain the microcomputer 10, 11 calculates the engine 1 from the signal of the crank angle sensor 9.
12 is a means for calculating the amount of fuel Qf to be supplied to the engine 1 from the rotation speed N of the engine 1 and the intake air flow rate Qa measured by the air flow meter 7. 13 is means for calculating the deceleration N〓 from the rotational speed of the engine 1 detected at different times;
14 is means for storing the first rotation speed N ₁ and the predetermined rotation angle θn; 15 is a means for calculating the second rotation speed N ₂ from the deceleration N〓, the first rotation speed N ₁ and the predetermined rotation angle θn 16 is a means for comparing the rotation speed N of the engine 1 and the recovery rotation speed Nr (=N ₂ ). Reference numeral 17 denotes means for controlling fuel supply and stop according to the ON/OFF of the idle switch 8, the engine speed N, and the comparison result between the engine speed N and the recovery speed Nr.

Next, the action will be explained.

The fuel supply amount Qf when the fuel supply is not stopped is:
As conventionally known, for example, from the intake air amount Qa measured by the air flow meter 7 and the rotation speed N calculated by the rotation speed calculation means 11 from the number of output pulses of the crank angle sensor 9 counted during a predetermined time, The fuel supply amount calculation means 12 calculates Qf=
It is calculated as K·Qa/N (K is a constant).

Further, the deceleration N〓 is calculated by the deceleration calculating means 13 as shown in the following equation from the engine rotational speeds N(t ₁ ) and N(t ₂ ) detected at a predetermined time interval (t ₂ - t ₁ ). Ru.

N = (N (t ₂ ) - N (t ₁ )) / (t ₂ /t ₁ ) Next, the third
The explanation will be based on the flowchart shown in the figure.

In S1, the idle switch 8 determines whether or not the throttle valve 3 is fully closed, and if it is fully closed, the S
If not, proceed to S2.

In S2, it is determined whether or not fuel is already being cut. If fuel is being cut, the process proceeds to S4; otherwise, the process proceeds to S3.

In S3, it is determined whether the engine rotation speed N is larger than the fuel cut determination rotation speed Nc at which fuel cut can be started, and if it is, the process proceeds to S22 to start fuel cut, and if it is small, the process proceeds to S21 to start fuel supply. continue.

In S4, the deceleration N〓 and the first
The second rotation speed N ₂ is calculated from the rotation speed N ₁ and the predetermined rotation angle θn using the following equation.

N ₂ = √ ₁ ² −2 Next, proceed to S5 and set the recovered rotation speed Nr = N ₂ , then proceed to S7 and compare the engine rotation speed N and the recovered rotation speed Nr, and if N≦Nr, proceed to S21. Proceed to resume fuel supply, and if N>Nr, proceed to S22 and continue fuel cut.

The predetermined rotation angle θn is the crankshaft rotation angle θip (for example, 23π/6) from fuel injection after recovery to the occurrence of the first detonation, which has been determined in advance through experiments, or the timing of the recovery determination is determined at the rotation angle θip. The required rotation angle θm caused by the variation is added (θip + θm).

Regarding θm, the time it takes from recovery determination to fuel injection is actually not zero.
For example, if we have an engine that injects fuel into all cylinders simultaneously at a predetermined crank angle once per revolution, and supplies fuel for one explosion with two injections, fuel is always injected at a predetermined crank angle. Therefore, the crankshaft rotation angle θip required from fuel injection to explosion is constant, but since the recovery determination is not synchronized with the crank angle, it is not known at which point within 720° the recovery determination is made. Therefore, in the case of two injections, a maximum of 360° is required from the recovery determination until the fuel is actually injected. Therefore, this is set as θm.

A second embodiment is shown in FIGS. 4 and 5.

In this embodiment, when setting the recovery rotation speed Nr, the second rotation speed N ₂ is not used as is, but N ₂
A value obtained by adding a predetermined rotational speed difference Nm to the rotational speed difference Nm is used.

To explain the different parts, in Fig. 4, 1
8 is a means for storing a predetermined rotational speed difference Nm, and 19 is a second memory as a recovery rotational speed Nr to the comparison means 16.
This means adds a predetermined rotational speed difference Nm to the rotational speed _N2 and outputs the result. In the flowchart of FIG. 5, at S5', the recovery rotation speed Nr=N ₂ +
It is set as Nm.

To explain Nm using an example, the measured value of the engine rotational speed N at the time of recovery determination causes an error for the following two reasons.

One is that the rotation speed is measured by counting the pulses output from the crank angle sensor within a certain period of time, so the counting gate time is Tms.
Then, there is a relationship between the measured value Nms at the completion of the measurement and the true rotational speed Ne as shown in the following equation.

Nms−Ne=1/Tms∫ ^Tms _p ∫ ^t _p N〓dt ^2If N〓=constant, then Nms−Ne=1/2N〓Tms.

The second reason is that recovery determination is not performed all the time, but at every TJD. In other words, after measuring the rotational speed, a recovery determination is made based on the variation between 0 and Tjd. During this time, the engine speed decreases by the following equation.

∫ ^Tjd _p N〓dt If N〓=constant, then N〓Tjd.

The sum of these two is Nm.

Nm=(1/2Tms+Tjd)N〓 Although Nm is calculated from the above formula and stored as a table value, it may also be calculated in the program using the above formula.

In these first and second embodiments, the recovery rotation speed Nr is calculated in the program, so the recovery rotation speed is determined according to the deceleration N〓.
It has the advantage of saving memory for storing Nr.

A third embodiment is shown in FIGS. 6 and 7.

In this example, the recovery rotation speed Nr (=N ₂ or N ₂ +Nm) calculated by corresponding to the deceleration N〓
is stored in the memory as a table value, and the recovery rotation speed Nr is set by searching from the deceleration N〓.

To explain the different parts, 20 in Figure 6
21 is means for storing the recovery rotation speed Nr corresponding to the deceleration N〓, and means 21 is means for searching the recovery rotation speed Nr stored in advance from the deceleration N〓.

Referring to the flowchart of FIG. 7, when the engine is in a deceleration state and fuel is being cut off, in S6, the recovery rotation speed Nr stored in the memory in advance is retrieved from the deceleration N〓. Then, in S7, the engine speed N and the recovery speed Nr are compared, and if N>Nr, the process proceeds to S22 to continue fuel cut, and N≦
If Nr, proceed to S21 and restart fuel supply.

<Effects of the Invention> As explained above, according to the present invention, the recovery rotation speed is determined as the deceleration, the crankshaft rotation angle required from fuel injection to the first explosion after recovery, and the first rotation speed determined as the lower limit rotation speed. Because it is determined by calculation from the rotational speed of the engine, precise control can be performed without the need for extensive experiments on the vehicle, and it is possible to maximize fuel savings while preventing engine stalling.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of the present invention, Figure 2 is a block diagram showing the configuration of the present invention.
The figure is a schematic diagram showing the first embodiment, Figure 3 is a flowchart of the first embodiment, Figure 4 is a schematic diagram showing the second embodiment, and Figure 5 is a flowchart of the second embodiment. FIG. 6 is a schematic diagram showing the third embodiment, and FIG. 7 is a flowchart of the third embodiment. 1... Engine, 4... Fuel injection, 8... Idle switch, 9... Crank angle sensor, 10... Microcomputer.

Claims (1)

[Scope of Claims] 1. A fuel supply system for an internal combustion engine having means for stopping the supply of fuel to the engine when the engine decelerates, comprising: means for detecting the rotational speed of the engine; and means for detecting the deceleration of the engine. , which is determined by the following calculation formula from the deceleration of the engine, and the crankshaft of the engine rotates by a predetermined rotation angle θn until the engine rotation speed decreases to a predetermined first rotation speed N ₁ at the deceleration N 〓. the second rotational speed such that
N ₂ = √ 1 2 −2 N ₂ = √ ₁ ² −2 Comparing the engine speed during the stoppage of heat supply during deceleration with the set fuel supply restart speed; A fuel supply device for an internal combustion engine, comprising: means for restarting fuel supply when the engine rotational speed falls below the fuel supply restart rotational speed.