JPH0480217B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to one that performs high-altitude correction of a mixture ratio under high load.

(Prior art) When aiming to reduce exhaust gas and improve fuel economy, fuel injection devices are more advantageous than carburetors and are widely used. Figure 1 shows an electronically controlled fuel injection device (for example, Showa 57-32059
(see issue).

In such a device, basically, the intake air amount Q detected by the engine intake air amount detection means (air flow meter) 1 and the rotation speed detection means (detects the ignition pulse from the ignition coil) 2 Based on the engine speed N detected by the basic pulse setting means 6 of the control unit 5, the basic pulse width Tp=
k・Q/N (k is a constant) is calculated, and this is applied to the basic pulse correction means 8 using other operating parameters.
A drive pulse with the result of this correction as the valve opening time is output to the fuel injection valve 4 of each cylinder attached to the intake port downstream of the throttle valve.

In this case, since the fuel pressure in the fuel supply system supplied to the fuel injection valve 4 is always kept at a constant value relative to the intake pipe pressure by the pressure regulator,
Fuel proportional to the opening time of the injection valve 4 is injected toward the cylinder.

Further, the basic air-fuel ratio is set by the above-mentioned coefficient k. For example, in an engine equipped with a three-way catalyst, a value (constant) that provides approximately the stoichiometric air-fuel ratio is selected so that the three-way catalyst functions most effectively.

However, at high loads that require engine output, a mixture richer than the stoichiometric air-fuel ratio is required. Set mixing ratio correction coefficient Kfuff (>1.0) at high load
is multiplied by the above-mentioned Tp, and this corrected Tp・
A drive pulse with Kfuff (>Tp) as the opening time of the injection valve 4 was output to obtain the output mixture ratio at high load.

By the way, in such a device, the correction coefficient
Kfuff is a constant regardless of atmospheric pressure; in other words, the fuel increase rate under high load is a constant value regardless of atmospheric pressure, and since the fuel increase is performed immediately when the load becomes high, it can be used in mountainous areas at high altitudes. When used, the reduction in suction efficiency due to the drop in atmospheric pressure causes the driver to feel a lack of power and press the accelerator pedal deeper.

In this case, the fuel amount is increased at the same fuel increase rate as the fuel increase rate set for the lowland driving range where the actual intake air amount is decreasing, so the mixture ratio exceeds the appropriate output mixture ratio. This results in over-concentration, which actually reduces output and worsens fuel efficiency. Furthermore, if the above fuel amount is increased frequently, HC and CO in the exhaust gas will increase.

(Purpose of the Invention) Therefore, the present invention corrects the fuel increase rate at high loads and the delay time until the fuel increase when moving from lowlands to highlands, thereby reducing the deterioration of exhaust performance in both lowlands and highlands. It is an object of the present invention to provide a fuel injection device that minimizes a decrease in output while preventing this.

(Structure and operation of the invention) The present invention provides means for setting the basic injection amount based on the engine intake air amount and engine speed, means for determining whether or not the engine is under high load, and based on the determination result, when the engine is under high load. The present invention is based on a fuel injection system for an internal combustion engine that includes means for increasing the basic injection amount and a fuel injection valve that injects fuel into the intake system in accordance with a fuel injection pulse generated from the correction result.

The device includes a means for detecting atmospheric pressure, a means for determining whether the detected atmospheric pressure is in a highland or a lowland by comparing it with a reference value, and a means for measuring when a high load is sustained. a correction means for making the fuel increase rate at high loads smaller than at low altitudes and making the delay time until the start of fuel increase at high loads longer than at low altitudes based on these determination results and the signal from the measuring means; A means for determining whether the area is in a highland or a lowland by looking at the value of a flag stored in a memory when the load is high based on the judgment result of the high load judgment means, and if the judgment result indicates that the area is in a lowland, the reference atmospheric pressure is set at the Means for setting a reference value, or a value larger than this reference atmospheric pressure by a predetermined width in the case of a highland, as the reference value, and a value in the memory so that the flag represents the judgment result of the highland judgment means. A means for updating the information shall be provided.

In this case, if the fuel increase rate at high loads is made smaller at high altitudes where the air density is lower than at low altitudes, the air-fuel ratio will not become overrich even if the output is increased, and this overrich Prevention improves exhaust performance and minimizes power loss.

By the way, if the delay time until the fuel increase starts is the same at low altitudes and at high altitudes, for example, if the delay time optimally set for low altitudes is used as is at high altitudes, the time it takes for exhaust to deteriorate at high altitudes will be On the other hand, if the delay time set for high altitudes is used as it is at low altitudes, the increase in output will be greatly delayed, even though exhaust emissions are not so bad at low altitudes, and drivability will be adversely affected. Deteriorate.

On the other hand, in this invention, if the delay time at high altitudes is made longer than that at low altitudes, the longer delay time reduces the time during which the exhaust deteriorates due to the increase in output at high altitudes, so that the exhaust performance at high altitudes improves. In addition, the delay time is shorter at low altitudes, so the timing of increasing output is not unnecessarily delayed. By making the delay time before the fuel increase starts different between high and low altitudes, the balance between exhaust performance and output performance can be improved for both high and low altitudes.

By the way, if the reference value for determining whether or not the area is at high altitude is a constant value, when the atmospheric pressure fluctuates up and down near this reference value, even if the atmospheric pressure change is small, a high load may occur. As a result, the fuel increase rate and the delay time until the start of fuel increase at high loads are frequently switched between high and low altitudes.
It has an unnatural effect on drivability.

In contrast, in this embodiment, when it was determined from the memory value that the area was at a high altitude last time, the current reference value is set to a value that is increased by a predetermined width to the reference atmospheric pressure.
If it was determined that the area was in a lowland last time, the standard atmospheric pressure will be used as the current standard value.

In other words, if it is determined that the atmospheric pressure has decreased by passing the standard atmospheric pressure and that the area is at high altitude, then even if the atmospheric pressure rises again and crosses the standard atmospheric pressure, it is still considered to be at high altitude. It is not determined that the atmospheric pressure is higher than the reference atmospheric pressure by more than a predetermined width, and the switch to the lowland side is not performed unless the atmospheric pressure changes to the higher atmospheric pressure side by more than a predetermined width than the reference atmospheric pressure.

Similarly, when it is determined that the vehicle has reached a low-lying area for the first time, the same applies when the vehicle travels in a direction where the atmospheric pressure is decreasing.

As a result, even when the atmospheric pressure fluctuates up and down near the standard value, the fuel increase rate and delay time mentioned above will not change frequently between high and low altitudes, which will cause unnatural drivability. It has no negative impact.

(Embodiment) FIG. 2 is a schematic diagram of an embodiment of the present invention.

Reference numeral 5 denotes a control unit, which is mainly composed of a microprocessor (central processing unit), memory (storage device), and interface (input/output signal processing device). A signal from a rotation speed sensor 2 that detects the engine rotation speed N (for example, detects the ignition pulse from the ignition coil), and a throttle valve full switch 3 that detects when the throttle valve 10 is fully open or at a predetermined opening degree (for example, 40°) or more. , a signal from an atmospheric pressure sensor (for example, a semiconductor piezoelectric element) 11 that detects atmospheric pressure, and a signal from an oxygen concentration sensor 12 that detects oxygen concentration in exhaust gas, and based on these signals, the basic Specifically, a fuel injection pulse is created that is synchronized with the engine rotation and has a pulse width corresponding to the amount of intake air, and this pulse drives the fuel injection valve 4 of each cylinder. In addition, 13 is the engine body,
14 is an intake pipe, and 15 is a pressure regulator.

At the same time, the control unit 5 increases the amount of fuel at high load based on the signal from the throttle valve full switch 3. This will be explained based on the block diagram of the control unit shown in FIG.

7 is a high load judgment means for the engine, which inputs the signal from the throttle valve full switch 3 and determines whether the throttle valve full switch 3 is
When it is ON (throttle valve 10 is fully open), it is determined that a high load state is present.

6 is a basic pulse setting means, which determines the basic pulse width Tp=k・Q/N from the intake air amount Q and the engine speed N.
(where k is a constant for obtaining a predetermined air-fuel ratio) is calculated.

8 is a basic pulse correction means, and the basic pulse Tp is
Multiply by the mixing ratio correction coefficient K to obtain the normal output pulse width.
Te=Tp·K is determined, and a drive pulse (injection signal) with Te as the valve opening time is supplied to the fuel injection valve 4.

In this case, K is a coefficient stored in the memory such that K=Kfuff (>1.0) at high load when the throttle valve full switch 3 is ON, and K=1.0 in other operating ranges.

Therefore, in operating ranges other than high load, K=
1.0, the injection valve 4 is opened for a time corresponding to the value of Tp, and fuel is injected and supplied in proportion to this valve opening time, but when the load is high, Tp・Kfuff
The valve is opened for a time corresponding to the value of (>Tp), and the amount of fuel is increased during high loads.

The above configuration is the same as the conventional one, but in the present invention, an atmospheric pressure sensor 11, a high altitude determining means 20, an elapsed time measuring means 21, and a correcting means 8 are provided therein.

The high altitude determination means 20 compares the atmospheric pressure P detected by the atmospheric pressure sensor 11 with the reference P ₀ and determines that PT<
If P ₀ , it is determined that the area is a highland, and if P≧P ₀ , it is determined that the area is a lowland.

More specifically, as shown in FIG.
- It is determined whether the value of P is "0" or "1". When the value of this flag is "0", it means that the place is in a lowland, and when the value is "1", it means that it is in a highland.

As a result of the determination, the reference value setting means 33 enters the reference atmospheric pressure (constant) Pc into the reference value P ₀ when the area is low (FLAG-P=0), and when the area is high (FLAG
-P=1), the reference value setting means 33 sets the value obtained by adding a predetermined width ΔP (>0) to Pc as the reference value _P0 .

The reference value P ₀ set in this way is the comparison means 34
is compared with the atmospheric pressure P from the atmospheric pressure sensor 11,
If P<P ₀ , it is determined that the area is highland, and if P≧ _P0 , it is determined that it is lowland.

On the other hand, the flag value updating means 35
Highland or lowland determination result and flag FLAG−
The value of the flag FLAG-P stored in the memory 31 is updated so that the value of P corresponds to the value of the flag FLAG-P (when it is determined that it is a lowland, "0" is stored in the memory 31, and when it is determined that it is a highland, "0" is stored in the memory 31. 1”).

Returning to FIG. 3, the elapsed time measuring means 21 is a timer, which is set by the ON signal from the high load determining means 7, and measures the duration T after the throttle valve 10 is fully opened.
Measure.

The correction means 8 has an additional function to further control the fuel increase rate and the delay time until the fuel increase starts based on the signals from the high altitude determination means 20 and the elapsed time measurement means 21 in addition to the above-mentioned fuel increase correction function during high load. At high altitudes, the fuel increase rate is set lower than at low altitudes, and the delay time is set longer than at low altitudes.

In this example, a function is added to perform feedback control of the air-fuel ratio to the stoichiometric air-fuel ratio when the engine temperature is higher than the set engine temperature based on the signal from the oxygen concentration sensor 12.

That is, the air-fuel ratio determining means 22 determines whether the actual air-fuel ratio is higher or lower than the stoichiometric air-fuel ratio, and the correcting means 8 multiplies the above-mentioned Tp by using this determination result as the air-fuel ratio feedback correction coefficient α.
In this case, k is selected as a constant that provides the stoichiometric air-fuel ratio, and during steady driving, feedback control is performed to the stoichiometric air-fuel ratio by increasing or decreasing the value of α, thereby improving the exhaust composition and fuel efficiency.

Then, in the high load range, the feedback control is removed by setting α=1, and as described above, the amount of fuel is increased during high loads to increase the output.

Next, the operation will be explained based on the flowchart shown in FIG. However, in the following explanation or in FIG. 4, the actual value detected for atmospheric pressure and the actual value measured for the elapsed time after the throttle valve is fully opened are respectively referred to as P and T, and the standard also set by the control unit 5 is used. value and target value respectively P ₀ ,
TD. Also TH, TL (TH>TL)
are the high-altitude side target value and the low-altitude side target value that are selectively determined as the delay time target value TD, and similarly,
KH, KL (however, KH<KL and KH, KL>1.0)
are the highland side target value and the lowland side target value that are selectively determined as the high load mixing ratio correction coefficient target value Kfuff.

As mentioned earlier, the control unit 5 controls the high load mixture ratio correction coefficient Kfull and the delay time target value TD to ultimately adjust the output mixture ratio at high loads and the increase in fuel amount at high loads. It operates so that the delay time becomes a target value according to the operating state at that time.In order to do this, the atmospheric pressure P is first detected, and then the delay time is determined according to the comparison result between this P and the reference value _P0 . , the high-load mixing ratio correction coefficient target value and the delay time target value are set.

When P≧P ₀ , it is determined that the location is in a lowland, and the lowland target value TL of the delay time is entered in TD, and the lowland target value KL of the mixture ratio correction coefficient is entered in Kfull (step ,
), P<P When at a higher altitude than ₀ , set the high altitude target value TH which is larger than TL to TD, and set KL to Kfull.
Enter the high altitude target value KH which is smaller than the value (step...). The specific values of these target values (TL, TH, KL, KH) are:
For example, TL (about 1.0 to 0.5 seconds), TH (about 1.0 to 10.0 seconds), KL (about 1.05 to 1.30), and KH (about 1.01 to 1.20), and set the values so that TH>TL and KH<KL. select.

Next, the correction means 8 compares the delay time target value TD and the actual elapsed time T, and when T≧TD, it is determined that the true engine output is required for continuous hill climbing, etc., and K= Kfull and multiply Tp by this (step, , ). In addition, when T<TD, it is determined that the engine output is not required so much, such as when performing gentle acceleration during normal driving, and K=
1.0, and in this case, even if it is multiplied by Tp, it is still Tp (step, , ). The correction means 8 repeatedly performs such operations while continuously detecting and measuring P and T to perform mixture ratio correction control and delay time control at high loads.

In this case, at high altitudes where the air density is lower than at low altitudes, the output is increased because the high-altitude target value TH, which is smaller than the low-altitude target value KL, is used as the rate of increase at high load (Kfull). However, the air-fuel ratio will not become overrich, and by preventing this overriching, exhaust performance will be improved and the decrease in output will be minimized.

In addition, by setting a delay time (TD) before the start of fuel increase, the fuel amount is increased only when performing long-duration acceleration operations that truly require output, such as continuous climbing, so that the driver can output the engine output desired by the driver. demonstrate,
On the other hand, it is possible to avoid worsening exhaust emissions by not increasing the amount of fuel when performing acceleration operations that require short pedal depression, such as gentle acceleration. If the delay time is the same at high altitudes, exhaust performance and driving performance will deteriorate.

For example, if the low-altitude target value TL is used as is at high altitudes, the time it takes for exhaust to deteriorate at high altitudes will be prolonged; conversely, if the high-altitude target value TH is used as is at low altitudes, the exhaust emissions will be reduced less at low altitudes. Although the situation does not deteriorate, the increase in output is significantly delayed, and drivability worsens.

On the other hand, in this example, different delay times are set in consideration of the difference between highlands and lowlands, and the delay time at highlands is longer than at lowlands. The longer delay time reduces the amount of time it takes for exhaust to deteriorate as output increases at high altitudes, further improving exhaust performance at high altitudes, and the shorter delay time at low altitudes reduces the amount of time it takes for exhaust to deteriorate as output increases. This prevents the timing from being unnecessarily delayed. In other words,
By making the delay time before the fuel increase starts different between high and low altitudes, the balance between exhaust performance and output performance can be improved for both high and low altitudes.

On the other hand, if the atmospheric pressure fluctuates up and down near P ₀ with the throttle valve full switch ON, even a small change in atmospheric pressure will cause Kfull and TD to change between the high-altitude target value and the low-altitude target value. Switching control will be performed frequently, which may have an unnatural effect on drivability.

In contrast, in this embodiment, the reference value is set so that switching control is not performed unless the atmospheric pressure changes within a predetermined range.
P ₀ changes.

For example, if it was previously determined that the area is in a lowland based on FLAG-P=0, the current reference value _P0 is a constant Pc (step). Since the vehicle has traveled in a direction where the atmospheric pressure is decreasing from this state, by comparing this reference value P, if it is determined that this is the first time that the vehicle has reached a high altitude, the value of the flag FLAG-P is set to "1" (step), and the next time The reference value P ₀ increases by a predetermined width ΔP (step).

In this case, if you turn around and drive in the direction of increasing atmospheric pressure, from the next time onward the atmospheric pressure P will be (Pc
+ΔP) or more, the value of the flag FLAG-P remains at "1", meaning the highland side (step).

In other words, if it is determined that the atmospheric pressure P has decreased by passing Pc and it is determined that the area is at high altitude, then even if the atmospheric pressure rises again from this state and crosses Pc, it is not determined that the area has reached high altitude. First, the atmospheric pressure
Unless the atmospheric pressure changes to a higher side by more than ΔP than Pc, switching to the lowland side will not occur.

If it is determined that the area has become a lowland for the first time,
The same holds true when the vehicle travels in a direction where atmospheric pressure is decreasing.

In this way, the last time it was determined to be a highland,
The value obtained by increasing the standard atmospheric pressure Pc by a predetermined width ΔP is the current standard value P ₀ , and if it was determined to be a lowland last time,
By setting the reference atmospheric pressure Pc to the current reference value P ₀ , even when the atmospheric pressure fluctuates up and down near P ₀ , Kfull and TD will frequently change between the high-altitude target value and the low-altitude target value. There is no need for switching, and as a result, there is no unnatural effect on drivability.

Note that the fuel amount is not increased unless the load is high (step...).

(Effects of the Invention) As described above, according to the present invention, it is determined whether the area is in a highland or a lowland by comparing atmospheric pressure with a reference value, and based on this judgment result, if the area is in a highland, the fuel consumption under high load is determined. The fuel increase rate is lower than that at low altitudes, and the delay time until the start of fuel increase at high loads is longer than at low altitudes, and the value of the flag stored in memory is checked at high loads to determine whether the area is at high altitudes or low altitudes. However, based on this determination result, if the area is at a low altitude, the reference atmospheric pressure is set as the reference value, and if the area is at a high altitude, a value larger than this reference atmospheric pressure by a predetermined width is set as the reference value. Since the memory is configured to update the value in the memory so that the flag represents the determination result of whether the vehicle is in a highland or a lowland, it is possible to improve the balance between exhaust performance and output performance for both highland and lowland. Even when the atmospheric pressure fluctuates up and down near the reference value, the fuel increase rate and delay time described above are not switched frequently between high and low altitudes, which causes unnatural drivability. The effect of having no influence can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a conventional block diagram, FIG. 2 is a schematic diagram of an embodiment of the present invention, FIG. 3 is a block diagram of the control unit in FIG. 2, FIG. 4 is a flowchart thereof, and FIG. FIG. 2 is a detailed block diagram of the high altitude determination means 20. FIG. 1...Air flow meter, 2...Ignition coil,
3... Throttle valve full throttle, 4... Fuel injection valve, 5...
...Control unit, 6...Basic pulse setting means, 7...High load judgment means, 8...Basic pulse correction means, 9...Driving means, 11...Atmospheric pressure sensor, 20...High altitude judgment means, 21... ...Elapsed time measuring means, 31...Memory, 32...Flag determining means, 33...Reference value setting means, 34...Comparing means, 35...Flag value updating means.

Claims (1)

[Claims] 1. Means for calculating the basic injection amount based on the engine intake air amount and engine speed, means for determining whether or not it is under high load, and means for increasing the basic injection amount during high load based on the determination result. In an internal combustion engine equipped with a fuel injection valve that injects fuel into an intake system in accordance with a fuel injection pulse generated from the correction result, there is provided a means for detecting atmospheric pressure, and a means for detecting atmospheric pressure and a reference value. means for determining whether the area is at high altitude or low altitude by comparison of correction means for making the delay time until the start of fuel increase at high load longer than at low altitude and smaller than at low altitude; and means for determining whether the location is in a lowland or a lowland, and based on the determination result, if the location is in a lowland, the reference atmospheric pressure is set as the reference value, and if the location is in a highland, a value greater than the reference atmospheric pressure by a predetermined width is set as the reference value. A fuel injection device for an internal combustion engine, comprising: means for setting each as a reference value; and means for updating the value in the memory so that the flag represents the determination result of the high altitude determination means.