JP4694781B2 - Fuel supply device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to fuel correction during deceleration suitable for an internal combustion engine using a gaseous fuel such as natural gas.

  In a CNG engine that converts a diesel engine to an Otto cycle engine (an internal combustion engine that uses compressed natural gas as fuel), a means for calculating the intake air amount by the speed density method based on the intake pressure and the engine speed, a throttle valve Some include means for controlling the fuel supply amount in accordance with the calculated value of the intake air amount so as to generate an air-fuel mixture having a substantially constant air-fuel ratio upstream or downstream.

In an internal combustion engine that uses gasoline fuel instead of gas fuel such as CNG, in order to maintain the fuel injection amount at the time of acceleration / deceleration appropriately, wall flow fuel (attached to the wall surface of the intake passage and the wall surface remains liquid A method is disclosed in which the excess / deficiency of the fluid flowing into the cylinder is corrected (Patent Document 1).
JP-A-10-18882

In the internal combustion engine using a gaseous fuel such as natural gas, unlike the case of an internal combustion engine using gasoline fuel, because there is no generation of wall flow fuel need not perform the fuel correction for the excess and deficiency, intake pressure Due to the delay in the output of the intake pressure sensor that detects the engine , especially during deceleration where the amount of depression of the accelerator pedal changes suddenly to the closed side, the fuel supply reduction control is delayed, and excess fuel supply continues, causing There is a possibility that the fuel ratio becomes rich and the exhaust characteristics temporarily deteriorate.

  An object of this invention is to provide an effective means for improving such a subject.

According to a first aspect of the present invention, there is provided a means for detecting an intake pressure inside an intake manifold of an engine, a means for calculating an intake air amount using a detected value of the intake pressure, and a throttle valve that is opened / closed in accordance with a depression amount of an accelerator pedal Means for calculating a fuel supply amount in accordance with a calculated value of the intake air amount so as to generate an air-fuel mixture having a substantially constant air-fuel ratio upstream or downstream of the control unit, and means for controlling the fuel supply amount based on the calculated value; in supercharged internal combustion engine of a vehicle that uses a gas fuel such as natural gas and means for detecting an engine speed, means for detecting a depression amount of an accelerator pedal as an accelerator opening, the accelerator opening and the engine speed means for storing the boost limit value as a map data corresponding to the intake pressure value corresponding to the supercharge intake air amount defined by the number, the detected value of the engine speed Contact Based on the detected value of the fine accelerator opening obtains a boost limiter value corresponding to these detected values from said map data, and means for controlling the supercharge pressure below a boost limiter value while monitoring the detection value of the intake pressure, The means for calculating the intake air amount includes means for comparing the boost limiter value corresponding to the detected value of the engine speed and the detected value of the accelerator opening with the detected value of the intake pressure at that time, and the comparison Based on the result, when the detected value of the intake pressure <the set value of the boost limiter, means for calculating the intake air amount using the detected value of the intake pressure, and similarly, when the detected value of the intake pressure ≥ the boost limiter value, the intake pressure Means for calculating the intake air amount using a boost limiter value instead of the detected value of the intake pressure in order to prevent a delay in the control of the fuel supply amount during deceleration due to a detection delay of Characterized in that that.

According to a second invention, in the first invention, means for calculating a change amount Δθ to the closing side of the accelerator opening per one execution cycle TDEC of control based on the detected value of the accelerator opening, and the change amount And means for correcting the fuel supply amount to decrease by a predetermined time at a rate corresponding to the detected value of the accelerator opening and the amount of change Δθ when Δθ becomes a predetermined value or more.

According to a third aspect, in the second aspect, when the amount of change Δθ toward the closing side of the accelerator opening is equal to or greater than a predetermined value, the fuel is detected at a rate corresponding to the detected value of the accelerator opening and the amount of change Δθ. It means for correcting the supply amount by a predetermined time weight loss, and means for integrating attenuation process gradually to the correction amount 0 ratio according to the detected value and the variation △ theta accelerator opening when a predetermined time has elapsed, in that it comprises Features.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the intake air amount is unconditionally calculated using the detected value of the intake pressure when the vehicle is stopped and during low-speed traveling close to idle operation. characterized in that it comprises a means.

According to the first aspect, at the time of deceleration when the accelerator pedal is returned to the closing side, the boost limiter value decreases as the detected value of the accelerator opening decreases. If the boost limiter value falls below the intake pressure detection value due to the output delay of the intake pressure detection value, the boost limiter value is used instead of the intake pressure detection value to calculate the intake air amount that defines the fuel supply amount. Therefore, the fuel supply amount corresponding to the detected value of the intake pressure exceeding the boost limit value (the output delay of the detected value of the intake pressure) can be reduced. Therefore, it is possible to prevent the exhaust characteristic from being temporarily deteriorated due to the rich air-fuel ratio during deceleration due to the output delay of the detected value of the intake pressure.

According to the second invention, at the time of deceleration when the accelerator pedal is returned to the closing side, when the change amount Δθ to the closing side of the accelerator opening per one execution cycle TDEC of the control becomes a predetermined value or more, Since the fuel supply amount is corrected to decrease by a predetermined time at a rate corresponding to the accelerator opening and the change amount Δθ, excess fuel injection due to the output delay of the detection means with respect to the actual opening (actual accelerator opening) Since the amount can be reduced, it is possible to prevent the air-fuel ratio at the time of deceleration from becoming rich and exhaust characteristics from temporarily deteriorating.

According to the third invention, at the time of deceleration when the accelerator pedal is returned to the closing side, if the change amount Δθ calculated based on the detected value of the accelerator opening becomes equal to or greater than a predetermined value, the accelerator opening at that time and The fuel supply amount is corrected to decrease by a predetermined time at a rate corresponding to the change amount Δθ, but when the predetermined time elapses, the fuel supply correction amount is gradually reduced to 0 by the integral attenuation process. Fluctuations can be kept small .

According to the fourth aspect of the invention, the detected value of the intake pressure is likely to exceed the boost limiter value depending on the load condition when the vehicle is stopped and during low-speed traveling close to idle operation, but the detected value of the intake pressure is used unconditionally. Since the intake air amount is calculated, the occurrence of engine stall can be prevented. If the intake air amount is calculated using a boost limiter value lower than the intake pressure detection value, the fuel supply amount is reduced by the amount that the intake pressure detection value exceeds the boost limit value, which may cause engine stall .

  In FIG. 1, 10 is an engine with a supercharger mounted on a vehicle, and CNG (compressed natural gas) is used as fuel. A throttle valve 12 is interposed in the intake passage 11 of the engine 10, and a nozzle 15 of the fuel supply device 14 is disposed upstream thereof. The throttle valve 12 controls the intake flow rate to the engine 10 and is opened and closed according to the amount of depression of the accelerator pedal (accelerator opening). Reference numeral 13 denotes an ISC (idle speed control) valve that controls the engine speed during idling to a target idling speed.

  The fuel supply device 14 is provided with a pipe for supplying fuel (CNG) from a gas cylinder (not shown) to the nozzle 15. In addition to the gas control valve 16 (injection valve), the gas supply valve from the gas cylinder is not shown. A high-pressure fuel shut-off valve, a gas regulator, and a low-pressure fuel shut-off valve are installed in this order. The high-pressure fuel shut-off valve and the low-pressure fuel shut-off valve are controlled to open when the ignition switch is turned on and close when the ignition switch is turned off. The gas regulator regulates (depressurizes) the high-pressure fuel to a predetermined low-pressure fuel, and the gas control valve 16 supplies the low-pressure fuel to the nozzle 15 so as to generate an air-fuel mixture having a substantially constant air-fuel ratio. The (injection amount) is controlled according to the operating state.

  Reference numeral 17 denotes an engine spark plug. The air-fuel mixture is drawn into a cylinder of the engine, and is ignited by the spark plug 17 near the dead center of the compression stroke. The spark plug 17 is controlled to an optimal ignition timing according to the operating state.

  The engine control unit 20 controls the gas control valve 16, the spark plug 17, the ISC valve 13, etc., and an accelerator opening sensor 21 that detects the amount of depression of the accelerator pedal, a crank angle that detects the crank angle and the engine speed. An angle sensor 22 and an intake pressure sensor 23 for detecting intake pressure (intake manifold internal pressure) are provided.

  The engine control unit 20 boosts the boost pressure in addition to means for controlling the fuel injection amount of the gas control valve 16, means for controlling the ignition timing of the spark plug 17, means for controlling the opening of the ISC valve 13, etc. Means for controlling to keep the limiter value or less is provided. In FIG. 1, the boost limiter correcting means 30 constitutes a part of a means for controlling the supercharging pressure to be below the boost limit value and also constitutes a part of a means for controlling the fuel injection amount of the gas control valve 16. To do.

  In the means for controlling the boost pressure to be equal to or lower than the boost limit value, the boost pressure exceeds the boost limit value while monitoring the boost pressure (detection signal of the intake pressure sensor 23) based on the boost limit value. Then, control is performed to reduce the supercharging pressure below the boost limit value by exhaust bypass or the like.

  The boost limiter correction means 30 stores the map data (boost limiter map as shown in FIG. 4) of the boost limit value defined by the engine speed and the accelerator opening, and the engine speed detection signal and the accelerator opening Based on the detection signal, a boost limiter value obtained from the map data of FIG. 4 is output. A load SW24 (operation switch such as an air conditioner) is provided, and a function for correcting the boost limiter value is set by turning the load SW24 on and off.

  In the means for controlling the fuel injection amount of the gas control valve 16, the output of the boost limiter correcting means 30 (boost limiter value) and the output of the intake pressure sensor 23 (detection signal) are inputted to the comparator 31, and the smaller one is inhaled. It is output to the air amount calculation means 32. When the output of the intake pressure sensor 23 is equal to or greater than the output of the correction means 30 (boost limiter value), the comparator 31 outputs the output of the correction means 30 (boost limiter value) as the intake pressure used to calculate the intake air amount, and the intake pressure sensor. If the output of 23 <the output of the correction means 30 (boost limiter value), the detection signal of the intake pressure sensor 23 is also output. The boost limiter correction means 30 is provided with a vehicle speed sensor 25, and has a function of giving a signal to the comparator 31 so as to output the detection signal of the intake pressure sensor 23 unconditionally when the vehicle is stopped and during low-speed traveling close to idle operation. Is set.

In the intake air amount calculation means 32, the intake air temperature for detecting the output of the comparator 31 (the output of the intake pressure sensor 23 or the output of the correction means 30), the detection signal of the engine rotation sensor, and the intake air temperature (internal temperature of the intake manifold). An intake air amount is calculated by a speed density method based on a detection signal of a sensor (not shown).

  In the deceleration fuel reduction correction means, map data (a deceleration fuel reduction correction map as shown in FIG. 5) of the correction coefficient Kdec defined by the accelerator opening and the amount of change Δθ toward the closing side is stored. Based on the output (detection signal) of the accelerator opening sensor 21, the change amount Δθ is calculated as Δθ = previous detection value−current detection value. When the amount of change Δθ is equal to or greater than a predetermined value (DDTVODEC), a correction coefficient Kdec corresponding to these is obtained from the map data of FIG. 5 based on the accelerator opening and the amount of change Δθ at that time, and the predetermined time (TKDEC) is While the output of the correction coefficient Kdec is kept constant until it elapses, when the predetermined time (TKDEC) elapses, the correction coefficient Kdec is gradually reduced to 0 at a predetermined rate (integral attenuation control).

  The fuel injection amount calculation means 34 calculates the fuel injection amount Te (effective injection pulse width) of the gas control valve according to the intake air amount (output of the calculation means 32). The effective injection pulse width Te is corrected to decrease to Te = Te × (1−Kdec) until it is attenuated to the correction coefficient Kdec = 0 based on the correction coefficient Kdec from the fuel decrease correction means 33 during deceleration. .

  FIG. 2 is a flowchart for explaining the control contents related to the calculation of the intake air amount, and is repeated every predetermined execution cycle. In S1, based on the detection value of the vehicle speed sensor 25, it is determined whether vehicle speed ≧ boost limiter determination vehicle speed. The boost limiter determination vehicle speed is a reference value for determining the conditions under which the boost limiter value is allowed for the calculation of the intake air amount GA, and a boost limiter value lower than the output of the intake pressure sensor 23 is calculated for the intake air amount GA. If it is used, the vehicle speed value (for example, 1 km / h to 10 km / h) that may cause engine stall is set. When the determination of S1 is yes, the process proceeds to S2, while when the determination of S1 is no, the intake pressure Pd = the output of the intake pressure sensor 23 is set at S7.

  In S2, the detection value of the accelerator opening sensor 21 is read, and in S3, the detection value (engine speed) of the crank angle sensor 22 is read. In S4, based on these detected values, a boost limiter value corresponding to the accelerator opening and the engine speed is obtained from the boost limiter map. In S5, it is determined whether or not the output of the intake pressure sensor 23 ≧ the boost limiter value. When the determination of S5 is yes, the intake pressure Pd = boost limiter value used for calculation of the intake air amount GA is set at S6. On the other hand, when the determination of S5 is no, the intake pressure Pd = Sets the output of the intake pressure sensor.

  In S8, the intake air amount GA = K × Pd / Tb × N is calculated using the intake pressure Pb (boost limiter value) in S6 or the intake pressure Pb (output of the intake pressure sensor 23) in S7. K is the intake air volume coefficient, Pd is the intake pressure (kpa absolute pressure), Tb is the intake air temperature (K absolute temperature), and N is the engine speed. Based on the calculated value of the intake air amount GA, the fuel injection amount Te required to generate the air-fuel mixture with the predetermined air-fuel ratio is calculated, and if there is no output of the fuel reduction correction coefficient Kdec during deceleration, the intake air amount GA is calculated A fuel injection amount signal corresponding to the value is output to the gas control valve 16.

  FIG. 6 is a timing chart illustrating changes in the engine speed, the output of the accelerator opening sensor 21, the output of the intake pressure sensor 23, the boost limiter value, the intake air amount, and the excess air ratio λ during deceleration. When the accelerator pedal is returned to the closing side and the output of the opening degree sensor 21 decreases, the intake pressure (actual intake pressure) decreases due to the operation of the throttle valve 12 toward the closing side. The boost limiter value also decreases as the engine speed and accelerator opening decrease.

The output of the intake pressure sensor 23 decreases after the boost limiter value (see the dotted line in the figure). However, when the output of the intake pressure sensor 23 ≥ the boost limiter value, the boost limiter is used for calculating the intake air amount GA during that time. The value is used. Therefore, compared with the case where the calculation of the intake air amount GA is continued using the output of the intake pressure sensor 23, the excessive fuel injection amount due to the output delay of the intake pressure sensor 23 is suppressed, and the excess air ratio λ The decrease is also reduced, and the exhaust characteristics during deceleration can be prevented from deteriorating.

  FIG. 3 is a flowchart for explaining the control contents related to the fuel reduction correction during deceleration, and is repeated every predetermined execution cycle. In S11, it is determined whether or not the change amount Δθ ≧ the predetermined value (DDTVODEC) by comparing the change amount Δθ calculated based on the output of the accelerator opening sensor 21 with a predetermined value (DDTVODEC). When the determination of S1 is yes, the process proceeds to S12, while when the determination of S11 is no, the process proceeds to RETURN.

  In S12, the accelerator opening is detected (the output of the accelerator opening sensor 21 is read). In S13, the change amount Δθ of the accelerator opening is calculated. That is, when the change amount Δθ ≧ predetermined value (DDTVODEC) is established in S11, the accelerator opening and the change amount Δθ at that time are determined in S12 and S13.

  In S14, a deceleration fuel decrease correction coefficient Kdec corresponding to the accelerator opening (determined value) and the change amount Δθ (determined value) is obtained from the deceleration fuel decrease correction map. In S15, the fuel injection amount Te (effective injection pulse width) corresponding to the intake air amount GA (calculated value in S8 in FIG. 2) is corrected to decrease to Te = Te × (1−Kdec). In S16, the fuel decrease correction coefficient Kdec during deceleration is held until a predetermined time (TKDEC) elapses. That is, until the predetermined time (TKDEC) elapses, the processing from S11 to S14 is passed, and the processing from S15 to S16 is repeated every execution cycle.

  When the predetermined time (TKDEC) elapses in S16, a process (integral damping control) for gradually reducing the deceleration fuel reduction correction coefficient Kdec to 0 is started in S17. As a result of this process, (1-Kdec) gradually increases, and the effective injection pulse width Te is gradually returned to the release state of the deceleration fuel reduction correction. In S17, the process from S1 to S16 is passed by the integral attenuation process of the deceleration correction coefficient Kdec until Kdec ≦ 0, and when Kdec ≦ 0 is reached, Kdec = 0 is set in S18. Set. Thereafter, the above-described processing is repeated from S11 every predetermined execution cycle.

  FIG. 7 is a timing chart for explaining the control related to fuel reduction correction during deceleration. When the pedal is returned to the closing side, the output of the accelerator opening sensor 21 decreases with a delay from the actual opening (actual accelerator opening). Due to this output delay, excess fuel injection continues as indicated by the dotted line in the figure, and the excess air ratio λ decreases greatly. However, the change amount Δθ of the accelerator opening to the closed side is a predetermined value (DDTVDEC ), The fuel supply amount Te (the effective injection pulse width calculated from the intake air amount GA at each execution cycle) is predetermined based on the correction coefficient Kdec corresponding to the accelerator opening and change amount Δθ at that time Since the time (TKDEC) is corrected to Te = Te × (1−Kdec), the decrease in the excess air ratio λ caused by the output delay of the accelerator opening sensor 21 with respect to the actual opening (actual accelerator opening) is small. It can be suppressed. When the predetermined time (DDTVDEC) elapses, the fuel supply correction amount is gradually reduced to 0 by the integral attenuation process, so that fluctuations in the engine speed associated with the cancellation of the deceleration fuel reduction correction can be kept small.

  In this embodiment, the excess fuel supply amount caused by the output delay of the intake pressure sensor 23 and the excess fuel supply amount caused by the output delay of the accelerator opening sensor 21 are obtained by the control of FIG. 2 and the control of FIG. Therefore, the exhaust characteristics during deceleration can be prevented from being temporarily deteriorated.

It is a system outline figure concerning the embodiment of this invention. It is a flowchart explaining the control content of a control unit similarly. It is a flowchart explaining the control content of a control unit similarly. It is a characteristic view which similarly illustrates a boost limiter map. It is a characteristic view which similarly illustrates the fuel reduction correction map during deceleration. It is a timing chart explaining the contents of control similarly. It is a timing chart explaining the contents of control similarly.

Explanation of symbols

11 Intake passage
12 Throttle valve
13 ISC valve
14 Fuel supply system
15 Fuel supply nozzle
16 Gas control valve (injection valve) of fuel supply system
17 Spark plug
20 Control unit

Claims (4)

Means for detecting the intake pressure inside the intake manifold of the engine;
Means for calculating the intake air amount using the detected value of the intake pressure;
Means for calculating a fuel supply amount according to a calculated value of an intake air amount so as to generate an air-fuel mixture having a substantially constant air-fuel ratio upstream or downstream of a throttle valve that is opened and closed according to the amount of depression of an accelerator pedal;
Means for controlling the fuel supply amount based on the calculated value;
In an internal combustion engine with a supercharger for a vehicle that uses a gaseous fuel such as natural gas,
It means for detecting an engine speed,
It means for detecting a depression amount of an accelerator pedal as an accelerator opening,
And means for storing the boost limit value as a map data corresponding to the intake pressure value corresponding to the supercharge intake air amount defined by the accelerator opening and the engine speed,
Based on the detected value of the engine speed and the detected value of the accelerator opening, the boost limit values corresponding to these detected values are obtained from the map data, and the boost pressure is less than the boost limit value while monitoring the detected intake pressure value. and means for controlling the,
The means for calculating the intake air amount is based on the comparison result between the boost limiter value corresponding to the detected value of the engine speed and the detected value of the accelerator opening and the detected value of the intake pressure at that time. When the detected value of intake pressure <the set value of boost limiter, means for calculating the intake air amount using the detected value of intake pressure, and when the detected value of intake pressure ≥ boost limiter value, the detection delay of intake pressure Means for calculating an intake air amount using a boost limiter value instead of a detected value of the intake pressure in order to prevent a delay in control of the fuel supply amount at the time of deceleration due to the fuel supply of the internal combustion engine apparatus. Means for calculating a change amount △ theta to the closed side of the accelerator opening per execution cycle TDEC control based on the detected value of the accelerator opening degree, when the amount of change △ theta is equal to or greater than a predetermined value the accelerator at the time The fuel supply device for an internal combustion engine according to claim 1, further comprising means for correcting the fuel supply amount to decrease by a predetermined time at a rate corresponding to the detected value of the opening and the change amount Δθ. When the change amount Δθ to the closing side of the accelerator opening becomes equal to or greater than a predetermined value, the means for correcting the decrease in the fuel supply amount for a predetermined time at a ratio according to the detected value of the accelerator opening and the change amount Δθ at that time, 3. A fuel for an internal combustion engine according to claim 2, further comprising means for performing integral attenuation processing for gradually adjusting the ratio corresponding to the detected value of the accelerator opening and the change amount Δθ to a correction amount of 0 when a predetermined time has elapsed. Feeding device. 4. The apparatus according to claim 1, further comprising: a unit that unconditionally calculates the intake air amount using the detected value of the intake pressure when the vehicle is stopped and during low-speed traveling close to idle operation. A fuel supply device for an internal combustion engine.

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