JPH0469738B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring intake pipe pressure of an internal combustion engine.

One known method for determining the optimal fuel injection amount according to the state of the internal combustion engine is to measure the intake pipe pressure of the internal combustion engine and use this as a parameter to determine the basic fuel injection amount. .

In this system, even if the throttle opening is constant, the intake pipe pressure constantly pulsates due to the pumping action of the internal combustion engine, so it is necessary to prevent it from being affected by the pulsations.

[Conventional technology]

The conventional method for eliminating the influence of intake pipe pressure pulsations is to reduce the diameter of the pipe that connects the intake pipe and the pressure sensor to prevent small pulsations from reaching the pressure sensor, and to prevent the pressure transmitted to the pressure sensor from reaching the intake pipe. As shown in Fig. 6, a filter is installed between the pressure sensor 2, which directly detects the pressure inside the intake pipe 1, and the A/D converter 3, to cut out pulsating components. A method of providing 4 is known.

[Problem that the invention seeks to solve]

However, in general, the pulsation frequency of intake pipe pressure increases in proportion to the engine speed, so for example, the pipe diameter is made sufficiently thin so that the pulsation component in the low rotation range can be sufficiently removed. If the time constant of 4 is increased, changes in the intake pipe pressure when the throttle opening changes suddenly cannot be detected with good response.On the other hand, in order to improve the response when the throttle opening changes suddenly, the pipe diameter is made thicker.
If the time constant of the filter 4 is made small in this method, it becomes difficult to eliminate the influence of pulsation in the low rotation range. Furthermore, in general, with conventional methods, it is difficult to accurately determine the average value of the intake pipe pressure, and some pulsation components remain.

The present invention has improved these conventional drawbacks, and its purpose is to maintain the intake pipe over a wide range of internal combustion engines, from low to high rotational speeds, without being affected by the pulsating components caused by the pumping action of the cylinder. The purpose is to be able to accurately determine the average value of pressure and to improve responsiveness during transient times.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention includes a pressure sensor 11 that detects the pressure inside an intake pipe 10, and an A/D converter that converts the output of the pressure sensor 11 into a digital value, as shown in FIG. 12 and A/
an average value calculating means 13 for sampling the output of the D converter 12 at every predetermined crank angle, and calculating an average value of the intake pipe pressure using the plurality of immediately preceding sampling values; The acceleration determination level set based on the maximum value of the values is compared with the output of the A/D converter 12, and the A/D
When the output of the converter 12 exceeds the acceleration determination level, it is determined that the internal combustion engine is accelerating, and the A/D converter 12
an acceleration determining means 14 that determines that the internal combustion engine is in a steady state when the output of the engine is below the acceleration determining level; a deceleration determining level that is set based on the minimum value of the plurality of sampling values; and A/D conversion. When the output of the A/D converter 12 is less than the deceleration determination level, it is determined that the internal heat engine is decelerating, and when the output of the A/D converter 12 is equal to or higher than the deceleration determination level. The deceleration determining means 15 sometimes determines that the internal combustion engine is in a steady state, and the output of the average value calculating means 13 is selected when the internal combustion engine is in the steady state according to the determination results of the acceleration determining means 14 and the deceleration determining means 15,
During the acceleration or deceleration, the output of the A/D converter 12 is selected only during the initial period after it is determined that the acceleration or deceleration is occurring, and then the output of the average value calculation means 13 is selected, and the fuel injection amount is determined respectively. A selection means 16 is provided for outputting the intake pipe pressure used in calculating the intake pipe pressure.

In a preferred embodiment of the invention, e.g.
In the case of a four-cylinder cylinder internal combustion engine, the average value calculation means 13 samples the output of the A/D converter 12 every 45 degrees of the crank angle, and calculates the average value from the previous four sampling values. In addition, in this case, the maximum value among the plurality of sampling values becomes approximately the maximum value of the pulsating component, and the minimum value among the sampling values approximately becomes the minimum value of the pulsating component, so that the acceleration determination level of the acceleration determining means 14 is set to a value based on the maximum value, and the deceleration determination level of the deceleration determining means 15 is set to a value based on the minimum value.

[Effect]

The pressure in the intake pipe 10 is detected as an analog quantity by the pressure sensor 11, converted to a digital quantity by the A/D converter 12, and then added to the average value calculation means 13, where the internal combustion engine is calculated based on the crank angle signal. A plurality of A/D conversion values at a predetermined rotational position are accumulated, and an average value of the intake pipe pressure is calculated from the accumulated values and output.

Further, the output of the A/D converter 12 is applied to the average value calculating means 13, the acceleration determining means 14, and the deceleration determining means 15.
In step 5, the selection means 16 determines whether acceleration or deceleration has been performed by comparing the A/D conversion value with an acceleration determination level and a deceleration determination level, respectively.
During a period when acceleration is not determined by the acceleration determining means 14 and deceleration is not determined by the deceleration determining means 15, the output of the average value calculating means 13 is selected, and whether the acceleration is determined by the acceleration determining means 14 or the deceleration is determined by the deceleration determining means 15. When deceleration is determined, the output of the A/D converter 12 is selected instead of the average value for a predetermined period thereafter.

〔Example〕

FIG. 2 is a block diagram of main parts of an embodiment of the present invention, showing a case where the present invention is applied to an engine control device that controls fuel injection, ignition timing, and idle speed of an internal combustion engine.

In the figure, 20 is an intake pipe, and a pressure sensor 21 is attached thereto. As the pressure sensor 21, various types of sensors such as a capacitive sensor, a semiconductor piezoresistive sensor, etc. can be used.
In this embodiment, the detection end of the pressure sensor 21 is inserted directly into the intake pipe 20, or connected through a thick pipe, so that pulsation components can also be detected.
The output of the pressure sensor 21 is input to an A/D converter 24 via an input interface 23 of a controller 22, where it is converted into a digital quantity and input to a microprocessor (MPU) 26. In addition,
The signal may be configured to be passed through a filter that removes noise before being input to the A/D converter 24.

The input interface 23 also receives the output of the crank angle sensor 25 and outputs from various sensors necessary for fuel injection, ignition timing, and idle speed control, and those that need to be A/D converted are input to the A/D.
Those that are not needed are input to the MPU 26 via the converter 24 and directly to the MPU 26 .

The MPU 26 reads the output of the A/D converter 24 and the output of the input interface 23 at a predetermined period, performs various calculations, and generates a fuel injection control signal a.
Ignition timing control signal b, idle speed control signal c
is output to the external circuit via the output interface 27. Programs and the like necessary for causing the MPU 26 to perform predetermined processing are stored in the memory 28.

3 and 4 are flowcharts showing an example of the processing of the MPU 26 in a 4-cylinder, 4-cycle internal combustion engine. The intake pipe pressure treatment is performed every 45 degrees of crank angle based on the output. In addition, S1~
S11 and S20 to S30 indicate each step.

Generally, the pulsation frequency f of the intake pipe pressure is determined by the number of cylinders in the internal combustion engine being M and the engine speed being N (rpm).
Then, f=M×N/120, which may vary depending on the engine speed, but the pulsation is synchronized with the intake stroke of the engine. That is, in the case of a four-cylinder engine, for example, the change in intake pipe pressure depends on the crank angle, as shown in Figure 5.
It appears once every 180 degrees. Therefore, for example, by accumulating digital values of the intake pipe pressure every 45 degrees of the crank angle and calculating the average of the immediately preceding four accumulated values, it becomes possible to obtain an accurate average value.

Next, the operation of this embodiment will be explained with reference to FIGS. 2 to 5.

The MPU 26 is interrupted every 2 msec by an internal timer and executes the processing shown in FIG. In this process, first, the digital value of the pressure sensor 21 is read from the A/D converter 24 shown in FIG. 2, and the read A/D converted value is set as the current A/D converted value PMAD (S1 ).

The MPU 26 monitors the output of the crank angle sensor 25 and performs processing as shown in FIG. 4 every 45 degrees of the crank angle. That is, every time the crank angle passes 45 degrees, the value of the counter CRNK inside the MPU is incremented by +1, and when the value of the count CRNK exceeds 3, the value of the counter CRNK is initialized to 0 (S20 ~S22), counter
If the value of CRNK is 0, that is, if the crank angle is 0 degrees, the current A/D conversion value PMAD is set to the sampling value PM1 of the crank angle of 0 degrees, and regardless of the value of counter CRNK is 1, 2, or 3. In other words, if the crank angle is 45 degrees, 90 degrees, or 135 degrees, this A/
D conversion value PMAD is crank angle 45 degrees, 90 degrees, 135
A process is performed to set the sampling values PM2, PM3, and PM4, respectively (S23 to S30).
In addition, when the crank angle reaches 180 degrees, the counter
Since the value of CRNK is returned to 0, the A/D conversion value PMAD at that time is again set to the sampling value PM1 at a crank angle of 0 degrees.

Therefore, when the intake pipe pressure is changing as shown in Fig. 5, when the crank angle passes from 0 degrees to 135 degrees, the sampling values PM1 to PM4 at the points A to D in Fig. 5 will change. I will be looking for
As shown in step S2 of FIG. 3, the MPU 26
Calculate their average value PMMEAN. Also,
When reaching point E in FIG. 5, the average is calculated from the four sampled values at points B, C, D, and E.

In addition, in the next steps S3 and S4, the MPU 26 extracts the maximum and minimum values of the four sampling values obtained so far, and sets them at the acceleration judgment level.
PMMAX and deceleration judgment level PMMIN,
By comparing each with the current A/D conversion value PMAD, it is determined whether acceleration has been performed and whether deceleration has been performed (S5, S6).

When acceleration or deceleration is detected, the internal counter CPM, which counts up every few milliseconds, is reset to 0 (S7), and the counter
Until CPM reaches a predetermined value time, for example, about 200 msec, the A/D conversion value PMAD, which is sequentially obtained every 2 msec, is used as the intake pipe pressure value PMTP used to calculate the basic injection amount. Except for the period when the opening is constant and the above transient period, the intake pipe pressure is set as PMTP.
Use the average value PMMEAN obtained in S2 (S9~
S11).

Therefore, for example, as shown after point E in Figure 5, the throttle valve is suddenly opened and the current A/D conversion value is
When PMAD exceeds the acceleration judgment level PMMAX,
Acceleration is determined in step S5, and then the basic injection amount of fuel is calculated using the A/D conversion value PMAD for a predetermined period of time, and when the predetermined period of time has elapsed, the average value PMMEAN determined in step S2 also increases in accordance with the acceleration. Furthermore, since the internal combustion engine is sufficiently accelerated, if the basic injection amount is calculated again using the average value, the accuracy of calculation can be improved without impairing responsiveness.

In the above embodiment, the digitized output of the pressure sensor 21 was sampled at every crank angle of 45 degrees, but a configuration may be adopted in which sampling is carried out at every other angle. Furthermore, although the maximum and minimum values of the plurality of sampling values sampled just before are used as the acceleration determination level and the deceleration determination level, each determination level may be a value with some level changes. Furthermore, after detecting acceleration and deceleration, the A/D is used instead of the average value for a predetermined period of time.
As a method of using the converted value PMAD, it is also possible to specify it by crank angle in addition to specifying it by time.

〔Effect of the invention〕

As explained above, in the present invention, the output of the pressure sensor is sampled at every predetermined angle of the crank angle by means of an average value calculating means that inputs the crank angle signal of the output of the A/D converter that converts the output of the pressure sensor into a digital value. Since the average value of the intake pipe pressure is calculated from the most recent A/D conversion values, an accurate average value can be obtained within the same crank angle in both the low and high rotation ranges, which is different from the conventional method. filter 4
This is equivalent to increasing the time constant in the low rotation range and decreasing it in the high rotation range, and it is not affected by the pulsation component due to the pumping action of the cylinder over a wide range from the low rotation range to the high rotation range of the internal combustion engine. It becomes possible to detect the average value of intake pipe pressure with good responsiveness.

In addition, the output of the acceleration determination means, the deceleration determination means, and the output of the average value calculation means and the A/D according to the results of these determinations are
According to the configuration in which a selection means is provided for selecting, for example, the intake pipe pressure used for calculating the fuel injection amount from among the outputs of the converter, it is possible to improve both responsiveness and measurement accuracy during transitions of acceleration and deceleration. There is.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of the present invention, FIG. 2 is a block diagram of main parts of an embodiment of the present invention, and FIGS. 3 and 4 are flowcharts showing an example of processing of the MPU 26 in a four-cylinder internal combustion engine. FIG. 5 is a diagram showing an example of changes in intake pipe pressure, and FIG. 6 is a configuration diagram of a conventional example. In the figure, 10, 20 are intake pipes, 11, 21
is a pressure sensor, 12 and 24 are A/D converters, 13
14 is an acceleration determining means; 15 is a deceleration determining means; 16 is a basic injection amount calculating means; 17
is a selection means, 22 is a controller, 23 is an input interface, 25 is a crank angle sensor, 26 is an MPU,
27 is an output interface, and 28 is a memory.

Claims (1)

[Claims] 1. A device for measuring intake pipe pressure used for calculating the fuel injection amount of an internal combustion engine, comprising: a pressure sensor that detects the intake pipe pressure; and A that converts the output of the pressure sensor into a digital value. a /D converter; and an average value calculation means that samples the output of the A/D converter at every predetermined crank angle and calculates an average value of the intake pipe pressure based on the plurality of immediately preceding sampling values; An acceleration determination level set based on the maximum value of the plurality of immediately preceding sampling values is compared with the output of the A/D converter, and the output of the A/D converter exceeds the acceleration determination level. acceleration determination means for determining that the internal combustion engine is in a steady state when the output of the A/D converter exceeds the acceleration determination level; The output of the A/D converter is compared with the deceleration determination level set based on the minimum value of the deceleration determination level, and when the output of the A/D converter is less than the deceleration determination level, it is determined that the internal combustion engine is decelerating. deceleration determining means for determining that the internal combustion engine is in a steady state when the output of the A/D converter is equal to or higher than the deceleration determining level; Sometimes, the output of the average value calculation means is selected, and during the acceleration or deceleration, the output of the A/D converter is selected only during the initial period after determining that the acceleration or deceleration is occurring, and then the average value calculation is performed. An intake pipe pressure measuring device for an internal combustion engine, comprising selection means for selecting an output of the means and outputting the selected output as an intake pipe pressure used for calculating the fuel injection amount.