JP2012172591A - Intake air amount measuring device of crank chamber compression two stroke engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an intake air amount per cycle of a crank chamber compression two stroke engine.SOLUTION: Using a crank chamber pressure sensor 19, pressure in a crank chamber 14 is detected at crank angle positions which include a point in the period from the end of closing of a scavenging port to the start of opening of an intake port, a point in the period from the end of closing of the intake port to the start of opening of the scavenging port and at least one point in the period from the start of opening of the intake port to the end of closing of the intake port, and the engine intake air amount per cycle is calculated based on the pressure data, crank chamber volume and intake air temperature at the crank angle positions. Further, during engine low speed operation, the pressure sensitivity and the zero drift amount of the pressure sensor 19 are corrected based on the outputs of the pressure sensor 19 at the crank angle positions of three points including a point near the bottom dead center and two points in either of the period from the end of closing of the scavenging port to the start of opening of the intake port or the period from the end of closing of the intake port to the start of opening of the scavenging port.

Description

  The present invention relates to an intake air amount measuring device for a crankcase compression two-cycle engine, and is a measuring device for obtaining the intake air amount of an engine by detecting the pressure in the crankcase.

  Currently, exhaust gas regulations are being strengthened in countries around the world, and the fuel supply device of a crankcase compression two-cycle engine is shifting from a carburetor to an electronic fuel injection device. In the electronic fuel injection device, measurement of the intake air amount of the engine is necessary. However, in the electronic fuel injection device of the conventional crankcase compression two-cycle engine, instead of directly measuring the intake air amount, the throttle opening, intake negative pressure, and engine speed are measured. A method of estimating the intake air amount using a reference table based on the above has been adopted. However, with these methods, the estimation accuracy of the intake air amount is poor in the operating range where the intake air amount changes greatly due to a slight change in the throttle opening and intake negative pressure, and the reference table is applied during steady operation of the engine In transient operation such as acceleration / deceleration, it is necessary to make corrections. Recently, in order to deal with exhaust gas regulation values and noise regulation values that differ for each country and region, the specifications of the exhaust system and intake system depending on the destination even for the same engine model There is a problem that the reference table must be created for each specification.

HONDA R & D Technical Review Vol. 4 (1992) "About PGM-FI engine for 2-stroke racer" Yamaha Motor Technical Report 2004-3 No. 37 (2004) "Gasoline direct injection 2-stroke outboard motor HPDI Z300, VZ300"

  In the conventional method of estimating the intake air amount using a reference table based on the throttle opening, the intake negative pressure and the engine speed in an electronic fuel injection device for a crankcase compression two-cycle engine, the estimation accuracy is poor and correction is made during transient operation. It is necessary to solve these problems in order to improve engine output and exhaust gas performance by electronic fuel injection devices.

  The intake air amount measuring device of the present invention is characterized in that the intake air amount per cycle is directly known by detecting the pressure in the crank chamber in a crank chamber compression two-cycle engine. First, the measurement principle by the intake air amount measurement device of the present invention will be described.

  FIG. 13 is a diagram for explaining the operation of one cycle from the bottom dead center of a crankcase compression two-cycle engine of a piston valve intake system. From the bottom dead center of FIG. 13 (a) to the scavenging port closing of FIG. 13 (b), the crank chamber 14 passes through the scavenging passage 16, the scavenging port 13, the cylinder 15, the exhaust port 12 and an exhaust pipe not shown in the figure. Communicate with the atmosphere. Next, from the closing of the scavenging port in FIG. 13B to the opening of the intake port in FIG. 13C, the crank chamber 14 is in a sealed state, and the air inside is adiabatically expanded. From the opening of the intake port in FIG. 13 (c) to the closing of the intake port in FIG. 13 (e) after the top dead center in FIG. 13 (d) is the intake period, the crank chamber 14 is connected to the intake passage 17 via the intake port 11. The air is introduced into the crank chamber 14 from the intake passage 17 and the fuel injected from the fuel injector 8 is carried to the crank chamber 14 by the intake flow. However, if the pressure in the crank chamber 14 becomes higher than the pressure in the intake passage 17 on the way, the air in the crank chamber 14 flows backward to the intake passage 17. This reverse flow phenomenon is called intake blowback, and normally, the intake air amount per cycle becomes maximum at an engine speed at which the intake port closing timing coincides with the blowback start timing, and intake blowback occurs at a rotational speed lower than the rotation speed. Although not shown in the figure, after the exhaust port 12 is closed between FIG. 13B and FIG. 13C, the air-fuel mixture filled in the cylinder 15 is compressed and the top dead in FIG. 13D. Just before the point, the spark plug 10 ignites and burns. From the closing of the intake port in FIG. 13 (e) to the opening of the scavenging port in FIG. 13 (f), the crank chamber 14 is again sealed and the air therein is adiabatically compressed. From the opening of the scavenging port in FIG. 13 (f) to the return to the bottom dead center in FIG. 13 (a) again, the compressed air in the crank chamber 14 flows into the cylinder 15 through the scavenging passage 16 and the scavenging port 13 and is generated by combustion. The combustion gas in the cylinder 15 is scavenged. At this time, the crank chamber 14 communicates with the atmosphere through the exhaust pipe as in FIGS. 13 (a) to 13 (b).

  FIG. 14 illustrates the operation of one cycle from the bottom dead center of a reed valve intake type crankcase compression two-cycle engine. The difference in structure between the piston valve intake system and the reed valve intake system is that, in the piston valve intake system, the side surface of the piston 2 opens and closes the intake port 11 provided in the cylinder body 1, whereas in the reed valve intake system, it differs from the crank chamber 14. A reed valve 43 is provided between the intake passage 17 to open and close the vent due to a pressure difference between the intake passage 17 and the crank chamber 14. If the pressure in the crank chamber 14 is lower than the pressure in the intake passage 17, the reed is caused by the pressure difference. The air vent is pushed up to open and air flows into the crank chamber 14 from the intake passage 17, and there is an advantage that blowback at an engine low speed can be reduced as compared with the piston valve intake system. From the bottom dead center of FIG. 14A to the closing of the scavenging port of FIG. 14B, the crank chamber 14 is almost at atmospheric pressure, and the reed valve 43 is closed. When the air in the crank chamber 14 is adiabatically expanded after the scavenging port is closed and the pressure in the crank chamber 14 becomes lower than the pressure in the intake passage 17, the reed valve 43 is opened and the air flows into the crank chamber 14 as shown in FIG. To do. The timing of reed valve opening depends on operating conditions such as engine speed and throttle opening. 14C. After the top of the reed valve is opened and the top dead center of FIG. 14D is passed and the reed valve is closed in FIG. 14E, the crank chamber 14 is inhaled through the vent of the reed valve 43. Air is communicated with the passage 17 and air flows into the crank chamber 14 from the intake passage 17, and fuel injected from the fuel injector 8 is carried to the crank chamber 14 by the intake air flow. The timing for reed valve closing varies depending on the operating conditions, as does the timing for reed valve opening. After the reed valve is closed, the same operation as that described in FIG. 13 (e) after closing the reed valve is performed, and the operation in the cylinder 15 is also the same as that described in paragraph 0006 of the present specification. In the following description, the vent of the reed valve 43 is expressed as an intake port, the crank angle when the vent is opened is expressed as an intake port is opened, and the crank angle when the vent is closed is expressed as an intake port is closed.

  FIG. 15 shows the relationship between the intake port opening / closing timing and the scavenging port opening / closing timing of the piston valve intake system and the reed valve intake system. In the piston valve intake system, the opening and closing timing of the intake port is symmetrical and fixed with respect to the top and bottom dead center, whereas in the reed valve intake system, the opening and closing timing of the intake port is asymmetric with respect to the top and bottom dead center and changes depending on the engine speed range. However, in both the piston valve intake system and the reed valve intake system, the intake period is always included in the period in which the scavenging port is closed.

As described in paragraphs 0006 to 0008 of the present specification, in the crankcase compression two-cycle engine, the crankcase during the period when the scavenging port is closed is either sealed or only the intake port is opened and communicated with the intake passage. It is in the state. Therefore, if the change in the amount of air in the crank chamber is measured while the scavenging port is closed, the amount of air taken into the crank chamber through the intake port can be known. Now, the crank chamber pressure is P _c , the crank chamber volume is V _c , the crank chamber air mass is G _c , the specific heat ratio of air is κ, the gas constant is R, the intake air temperature is T _int, and the air in and out of the crank chamber is insulated (a case of increasing positive) effected by those with the rate of change dG c _/ d [theta] per unit crank angle G _c at the crank angle θ when can be obtained by equation 1 based on the thermodynamic theory. In Equation 1, dV _c / dθ and V are variables that can be given as design values, and κ and R can be given as physical property values of air. The intake air temperature T _int is the intake air when the air flows into the crank chamber from the intake passage, that is, when the calculated value of the numerator (P _c · dV _c / dθ + V _c / κ · dP _c / dθ) on the right side of Equation 1 is positive The intake air temperature measured in the passage and the air flowing out from the crank chamber to the intake passage, that is, if the calculated value of the numerator on the right side of Equation 1 is negative, the intake air temperature in the crank chamber.

The crank chamber air amount change δG between the crank angles θ ₁ and θ ₂ is obtained by integrating Equation 1 from θ ₁ to θ ₂ as shown in Equation ₂ . ₁ crank angle theta in the period from when the scavenging port is closed until opened _inlet, when the crank angle is within a period from closing the intake port to the scavenging port is opened and the theta _2, the equation 2 The obtained crank chamber air amount change δG is equal to the intake air amount per cycle.

In the electronic fuel injection device, since many calculations other than the fuel injection parameter calculation are executed in one cycle, it is required to simplify the intake air amount calculation as much as possible. Now, as shown in FIG. 16, it is assumed that the crank chamber pressure _Pc is detected at N crank angle points during one cycle, and the crank angle points are assigned serial numbers i from 1 to N in order from the bottom dead center. In addition, the crank angle position of No. 1 is within the period from the scavenging opening to the opening of the intake opening, and the crank angle position of No. N is within the period from the closing of the intake opening to the opening of the scavenging opening. When P _c and V _c between the crank angle numbers i and i + 1 are interpolated with a straight line, the crank chamber air amount change δG _i between the crank angle numbers i and i + 1 is obtained by Equation 3.

In the calculation of Equation 3, the calculation of (P _i + P _{i + 1} ) / 2 · ((V _{i + 1} −V _i ) + (V _i + V _{i + 1} ) / (2 · κ) · (P _{i + 1} −P _i ) is first performed. When the calculation result is Q, if Q is positive, air is flowing from the intake passage into the crank chamber, and T _int uses the intake air temperature measured in the intake passage. If Q is negative, the air flows from the crank chamber. T _int as being flowing into the intake passage using estimated intake air temperature in the crank chamber plus a correction value to the intake air temperature, measured in the intake passage.

The intake air amount G _ia per cycle is obtained by integrating δG _i from i = 1 to N−1 as shown in Equation 4.

  When calculating the amount of intake air per cycle using Equations 3 and 4, the crank angle position of No. 1 is within the period from the scavenging port closing to the intake port opening, and the crank angle position of No. N is the intake port closing. And at least one point in the intake period is included in the N crank angle points so that the calculation process includes the effects of pressure and volume change during the intake period. is necessary.

  As described above, the intake air amount measuring device for a crankcase compression two-cycle engine according to the present invention can directly measure the intake air amount per one cycle of the engine by detecting the crankcase pressure. Compared with the method of estimating the intake air amount using a reference table consisting of the engine speed and the engine speed.

  The purpose of measuring the amount of intake air per cycle in a crankcase compression two-cycle engine was realized by detecting the pressure in the crankcase. 1 to 12 show an embodiment of an intake air amount measuring device according to the present invention.

  FIG. 1 shows a first embodiment of the present invention. In the first embodiment, the intake air amount measuring device of the present invention is applied to a piston valve intake type crank chamber compression two-cycle engine, and FIG. 1 is a cross-sectional view in the direction perpendicular to the crankshaft of the engine. In FIG. 1, the piston 2 reciprocates up and down in a cylinder 15 formed in the cylinder body 1 by a crank mechanism including a crankshaft 5 and a connecting rod 4. A side surface of the cylinder body 1 is provided with one intake port 11 and one exhaust port 12 and two scavenging ports 13 as shown in FIG. 2, and the exhaust port 12 is not shown in the drawing through an exhaust passage 18. The exhaust pipe communicates with the atmosphere. The scavenging port 13 communicates with the crank chamber 14 through a scavenging passage 16. The intake port 11 communicates with an intake cleaner box 9 via an intake passage 17 having a throttle valve 7 for adjusting the intake air amount, and the intake cleaner box 9 communicates with the atmosphere. A combustion chamber is formed so that the top of the cylinder body 1 is closed, and a spark plug 10 and a fuel injector 8 are attached. The fuel injector 8 injects fuel corresponding to the injection amount calculated by the fuel injection amount calculation unit 38 of the engine control unit 27 into the cylinder 15 at a separately determined injection timing, and the spark plug 10 is determined separately. An electric spark is generated at the ignition timing near the dead center, and the compressed air-fuel mixture in the cylinder 15 is ignited.

  FIG. 2 is a cross-sectional view in the crankshaft direction of the crankcase compression two-cycle engine shown in FIG. A bearing 40 that supports the crankshaft 5 is fitted to the crankcase body 6 and an oil seal 41 is attached to the outer side thereof, so that the airtightness of the crank chamber 14 is maintained. The crankshaft 5 is provided with a flywheel magneto 42 that generates power by the interaction of a permanent magnet incorporated in the flywheel and a power generation coil fixed to the crankcase body 6 side, and a part of the generated power is ignited. It is supplied to the system, and a part is sent to a storage battery (not shown) and then supplied to an electronic fuel injection system and other electrical systems. The above is the basic structure of the engine of this embodiment. Further, the operation of one cycle of the engine shown in the present embodiment is as described in paragraph 0006 of this specification, and the details are omitted.

  Next, a method for detecting the crank chamber pressure will be described. A pressure sensor 19 is attached to the side surface of the crankcase body 6. FIG. 3 shows details of the pressure sensor mounting portion. Both the pressure guide pipe 46 extending outward from the crankcase body 6 and the tip of the pressure sensor 19 are inserted into a rubber pipe 47 having a low thermal conductivity, and are stopped by a clip 48 to prevent them from coming out of the rubber pipe. With this attachment method, heat transfer from the crankcase body 6 that tends to become high temperature can be reduced to prevent the temperature of the pressure sensor 19 from rising. A pressure introducing hole is formed inside the tip of the pressure sensor 19, and a pressure receiving surface 49 is provided at the closed end thereof. The distortion of the pressure receiving surface 49 is converted into an electric signal and sent to the amplifier 33. The pressure sensor uses a strain gauge type, semiconductor strain gauge type, capacitance type, etc., but the frequency (1 / s) of the crank chamber pressure fluctuation during the scavenging port closing period to be measured is roughly the maximum rotation per second of the engine Since it is much lower than the intake / exhaust pressure and combustion pressure, it is possible to use a relatively inexpensive sensor. The pressure sensor may be either an absolute pressure measurement type or a gauge pressure measurement type, but hereinafter a gauge pressure measurement type will be used.

  Next, a method for detecting the engine crank angle position will be described. As shown in FIG. 2, a crank angle indexing disk 22 is attached to the outside of the flywheel magnet 42 and rotates integrally with the flywheel magnet 42. A row of projections of the crank angle detection projections 24 is arranged on one rotation surface of the outer periphery of the crank angle indexing disc 22, and one bottom dead center detection projection 23 is formed on a different rotation surface. Yes. Further, a crank angle sensor 21 and a bottom dead center sensor 20 are attached to the crankcase body 6 at positions where the protrusion rows and protrusions pass in the vicinity of the sensors by the rotation of the crank angle indexing disc 22. Both the crank angle sensor and the bottom dead center sensor are designed to generate an electric signal waveform when the distance between the protrusion and the sensor approaches, and the electric signal is output by the crank angle position determination unit 35 of the engine control unit 27 shown in FIG. It is detected as a crank angle signal.

  FIG. 4 shows an example of a crank angle value for pressure detection. Pressure detection is performed at seven crank angles from crank angle numbers 0 to 6 in FIG. 4, and the intake air amount calculation is performed using pressure data of five points from No. 1 at the intake opening to No. 5 at the intake opening. I do. The pressure data of No. 0 at the bottom dead center, No. 5 at the intake port closing, and No. 6 at the opening of the scavenging port are obtained by the pressure sensor calibration unit 39 executed after the calculation in the intake air amount calculation unit 37. Used for calculation. In the case of the piston valve intake system, Nos. 1 and 5 may not be strictly when the intake port is opened and when the intake port is closed, but may be slightly before the intake port is opened and slightly after the intake port is closed.

  In addition to the crank chamber pressure and crank angle, the atmospheric pressure sensor 25 detects the atmospheric pressure around the engine. An intake air temperature sensor 26 is attached to the intake cleaner box 9 so that the air temperature in the intake cleaner box can be measured.

  Next, a procedure for obtaining the intake air amount from the pressure data detected by the crank chamber pressure sensor 19 in the first embodiment will be described. Since the subject of the present invention is in the data processing procedure, detailed description regarding the circuit configuration and structure of each arithmetic unit in the engine control unit 27 in the following description will be omitted.

  As shown in FIG. 1, first, the output signal of the pressure sensor 19 is amplified by the amplifier 33 and then input to the input port 32 of the engine control unit 27, and the outputs of the atmospheric pressure sensor 25 and the intake sensor 26 are input to the input ports 28 and 29. After that, it is converted into a digital signal by the A / D converter 34. Output signals from the bottom dead center sensor 20 and the crank angle sensor 21 are input to the input ports 30 and 31, respectively.

  When the crank angle position determination unit 35 detects a crank angle signal at the input port 30 or 31, the input signals at the input ports 28, 29, and 32 are sampled and the subsequent processing is performed. Data processing in the crank angle position determination unit 35 and the crank chamber volume memory reference unit 36 is shown in FIG. When the bottom dead center signal is detected, the crank angle number i is set to zero, and every time the crank angle signal is detected, 1 is added to the crank angle number i. Reset to zero. Thus, the crank angle position can be specified by the value of the crank angle number i.

In the crank chamber volume memory reference unit 36, in addition to the crank chamber volume V _i at each crank angle for pressure detection, the crank chamber volume difference DV _i used in the intake air amount calculation unit 37, the crank chamber volume sum AV _i and the crank chamber volume The value of the ratio RV _i is calculated in advance and stored as a constant array memory, and the array memory is accessed based on the crank angle number i specified by the crank angle position determination unit 35 to obtain a value. The crank chamber volume is the volume of the air gap inside the crank case body 6 and the cylinder body 1 below the piston formed at a certain crank angle. The crank chamber volume at the top dead center is V _TDC , and the cylinder bore area is A _bore. When the piston displacement from the top dead center is S, it can be obtained by Equation 5. The V _TDC can be measured by filling the entire space including the crank chamber, the cylinder below the piston, the scavenging passage, etc., with a liquid such as oil without a gap, with the piston 2 at the top dead center.

FIG. 6 shows a processing flow in the intake air amount calculation unit 37. When the crank angle number determination unit 35 determines that the crank angle number is zero, the crank angle is at the bottom dead center, and the intake air amount G _ia is reset to zero. Next, the crank chamber pressure signal of the input port 32 is converted into pressure. When the pressure sensor 19 is a gauge pressure measurement type, if the input voltage at the input port 32 is E (Volt), the sensor sensitivity / amplification factor is C, and the input voltage at the input port 32 at atmospheric pressure is E ₀ , the absolute pressure in the crank chamber Can be obtained by Equation 6. In Equation 6, _Patm is the atmospheric pressure detected by the atmospheric pressure sensor. As C and E ₀ , values calibrated in advance can be used. However, these values may change depending on the temperature of the sensor or may change over time due to long-time use. .

Assume that the crank angle numbers are all N + 2 points from 0 to N + 1, and pressure data from 1 to N is used for the intake air amount calculation. The value P _i-1 at the crank angle number i is 2 or more and the value in the case of the following N crank angle number i P _i and the previous number _i-1, DV in those two crank angle number, AV value, and the intake air temperature Using T _int , an air amount change δG in the crank chamber between the crank angle numbers i and i−1 is obtained by the calculation shown in Equation 3, and δG is added to the value of the intake air amount G _ia . In the calculation of δG, the value of Q _i is first obtained by using the value of DV _i · (P _i + P _i-1 ) + AV _i · ((P _i -P _i-1 ) in Equation 3 as Q, and the intake air temperature T changing the value of _int. that air if the value of Q is positive or zero is used as the value T _m of a input port 29 of the intake air temperature to a value of T _int and flows into the crank chamber, the value of Q is negative Then, the air flows out of the crank chamber, and the value of T _int uses the value of T _m + α as an estimated value of the air temperature in the crank chamber, because the air temperature in the crank chamber when blowback occurs is higher than T _m . α is a positive value.

When the processing at the crank angle number N is completed by the intake air amount calculation unit 37, the process at the fuel injection amount calculation unit 38 is performed before the crank angle number N + 1 is detected to determine the fuel injection amount. FIG. 7 shows a processing procedure in the fuel injection amount calculation unit 38. It is assumed that a formula or a reference table for calculating the fuel injection amount from two variables of the engine speed RPM and the intake air amount _Gia per cycle is created in advance. When the crank angle number N is detected, the fuel injection amount G _f is calculated using an arithmetic expression based on the intake air amount G _ia obtained as the calculation result of the intake air amount calculation unit 37 and the engine speed RPM detected separately. Calculate The fuel injection command unit calculates parameters necessary for fuel injection, such as fuel injection pressure, fuel injection start timing, and injection time.

  In this embodiment, since an appropriate amount of fuel determined based on the intake air amount in the current cycle can be supplied to the engine in the scavenging process in the current cycle, the air-fuel ratio of the in-cylinder mixture can be controlled with high accuracy. However, if the installation position of the fuel injector 8 is in the intake passage, even if the fuel injection amount is determined, it can be supplied into the crank chamber in the intake process of the next cycle, and this advantage cannot be utilized. Therefore, as shown in FIG. 1, the fuel injector 8 is attached to the cylinder head and either directly injects fuel into the cylinder, is attached to the crankcase body 6 and is injected into the crank chamber 14 or injected into the scavenging passage 16. Use the method.

  FIG. 8 shows the execution order of intake air amount calculation, fuel injection amount calculation, fuel injection command unit calculation, and fuel injection. After the intake port is closed, fuel injection amount calculation and fuel injection command unit calculation are continuously executed to determine the fuel injection parameters as early as possible to lengthen the possible injection period and to control the injection pattern according to the engine requirements that change depending on the operating conditions Is possible.

  As the crank chamber pressure sensor 19 for the intake air amount measuring device, one having pressure sensitivity and zero point output calibrated in advance can be used. However, the pressure sensitivity and zero point movement amount of the pressure sensor vary depending on the sensor temperature. Or may change over time with prolonged use. Therefore, pressure sensitivity and zero point movement are corrected during engine operation.

  FIG. 9 shows changes in the crank angle of the crank chamber pressure of a piston chamber intake type crank chamber compression two-cycle engine. In the figure, SO is the scavenging port open, SC is the scavenging port closed, IO is the intake port open, IC is the intake port closed, TDC is the top dead center, and BDC is the bottom dead center. When the scavenging port is opened and the air in the crank chamber is sent to the cylinder, the crank chamber pressure decreases.At low speeds, scavenging ends before the bottom dead center, and during the period from the bottom dead center to the scavenging port closing, the crank chamber pressure is The pressure is kept close to atmospheric pressure. Normally, scavenging is completed by the bottom dead center in the engine speed range of about 1/4 or less of the engine maximum output speed during both the ignition operation and the driving operation at the start, and the crank chamber pressure at the bottom dead center is roughly It can be regarded as being equal to atmospheric pressure. Further, the crank chamber is in a sealed state during the period from the closing of the scavenging opening to the opening of the intake opening and the period from the closing of the intake opening to the opening of the scavenging opening, and the air in the crank chamber is in an adiabatic expansion or compression state.

The pressure sensor is calibrated by the following method using the characteristics observed in the crank angle change of the crank chamber pressure described in paragraph 0033 of this specification. First, since the crank chamber pressure at the bottom dead center during low-speed operation is equal to the atmospheric pressure, the voltage E of the input port 32 of the crank chamber pressure at the bottom dead center is directly set as the zero point movement amount E ₀ . Next, C is obtained by the following procedure from the ratio of the input voltage of the input port 32 at the two crank angles of intake port closing and scavenging port opening.

_Assuming that the crank chamber pressure at two crank angles is P _c1 and P _c2 and the crank chamber volumes are V _c1 and V _c2 , the relationship between the pressure and the volume between the two crank angles is expressed by Equation 7 according to the equation of adiabatic change. . In Expression 7, V _c1 , V _c2 and κ are known, and RV can be obtained in advance. Further, Expression 8 for obtaining the correction value of C is obtained from Expression 7.

FIG. 10 shows the calculation procedure of C and E ₀ in the pressure sensor calibration unit 39. Let E be the crank chamber pressure signal input voltage value. The separately detected engine speed RPM is lower than the set engine speed threshold RPM _s and the detected crank angle number i = 0 (bottom dead center) or i = N (inlet closing) or i = N + 1 ( The following processing is performed only when the scavenging port is open. First Save i = 0 if E as it is as the zero point moving amount E _0. If i = N, the voltage E is stored as E ₁ , and if i = N + 1, the voltage E is set to E _2, and then the calculation according to Equation 8 is performed to obtain C. The E ₀ and C obtained here are not updated until the correction calculation process is next performed in the pressure sensor calibration unit 39.

  FIG. 11 shows a second embodiment of the present invention. In the second embodiment, the intake air amount measuring device of the present invention is applied to a reed valve intake type crank chamber compression two-cycle engine, and FIG. 11 is a cross-sectional view of the engine in the direction perpendicular to the crankshaft. In FIG. 11, the piston 2 reciprocates up and down in a cylinder 15 formed in the cylinder body 1 by a crank mechanism including a crankshaft 5 and a connecting rod 4. One exhaust port 12 and two scavenging ports 13 are provided on the side surface of the cylinder body 1, and the exhaust port 12 communicates with an exhaust pipe (not shown) via an exhaust passage 18 so that the exhaust pipe is connected to the atmosphere. Communicate. The scavenging port 13 communicates with the crank chamber 14 through a scavenging passage 16. An intake passage 17 having a throttle valve 7 for adjusting the amount of intake air is attached to the crankcase body 6 with a reed valve block 44 interposed therebetween. The intake passage 17 further communicates with the atmosphere through an intake cleaner box. Yes. The reed valve block 44 is provided with a vent in the center, but the vent is blocked by the reed valve 43 when the engine is stopped. Further, the reed valve 43 is not damaged by excessive lifting of the reed valve to the back of the reed valve 43. A stopper 45 is attached. The operation of the reed valve 43 during engine operation is as described in paragraph 0007 of the present specification, and the intake port opening / closing timing is as described in paragraph 0008 of the present specification. A combustion chamber is formed so that the top of the cylinder body 1 is closed, and a spark plug 10 and a fuel injector 8 are attached. The fuel injector 8 injects fuel corresponding to the injection amount calculated by the fuel injection amount calculation unit 38 of the engine control unit 27 into the cylinder 15 at a separately determined injection timing, and the spark plug 10 is determined separately. An electric spark is generated at the ignition timing near the dead center to ignite the compressed air-fuel mixture in the cylinder 15.

  FIG. 12 shows an example of a crank angle arrangement for performing pressure detection in the second embodiment. Pressure detection is performed at all N + 1 crank angles from crank angle numbers 0 to N in FIG. 12. Of these, pressure data of N crank angle points from No. 1 at the intake opening to No. N at the opening of the scavenging opening. Is used to calculate the intake air amount. In the reed valve intake system, it is difficult to know the opening / closing timing of the intake port accurately unless the operation of the reed is measured by any method. Therefore, the position of the pressure detection crank angle number 1 for calculating the intake air amount is the end of the scavenging port closing before the top dead center can be considered to be surely closed, and the position of the number N is the same as the intake port after the top dead center. Start scavenging opening that can be regarded as closed reliably. The three pressure data including No. 0, No. N-1, and No. N are used for calculation in the pressure sensor calibration unit 39 executed after calculation in the fuel injection amount calculation unit 38.

The processing procedures in the crank angle position determination unit 35, crank chamber volume memory reference unit 36, intake air amount calculation unit 37, and fuel injection amount calculation unit 38 in the second embodiment are the same as those in the first embodiment. Omitted. Here, the processing calculation in the pressure sensor calibration unit 39 will be described. Similar to the piston valve intake system, the reed valve intake system can be regarded that the crank chamber pressure at the bottom dead center is approximately equal to the atmospheric pressure. Therefore, the voltage E of the crank chamber pressure input port 32 at the bottom dead center in the low speed operation is set as the zero point movement amount E ₀ as it is. Further, as shown in FIG. 15, it is known that the reed valve inlet closing timing is near the top dead center at a normal low speed. The reason for this is that at low speed, the intake time until the top dead center is reached after the reed valve is opened is long, and therefore the crank chamber pressure becomes higher than the intake passage near the top dead center. Therefore, at low speed, the reed valve is already closed at the crank angle after top dead center and close to the scavenging port opening, and the crank chamber can be regarded as being in a sealed state. Therefore, the pressure sensitivity C is obtained using the pressure data of the N-1 and Nth, which are the last two of the crank angle numbers shown in FIG.

  It can be used for measuring the intake air amount of an electronic fuel injection device for a crankcase compression two-cycle engine.

It is explanatory drawing which showed the implementation method of the intake air amount measuring device. (First embodiment) 1 is a plan view of a multi-cylinder engine to which a first embodiment is applied. It is explanatory drawing which showed the attachment method of the crank chamber pressure sensor. It is explanatory drawing which showed arrangement | positioning of a pressure detection crank angle. It is explanatory drawing which shows a data processing method. It is explanatory drawing which shows a data processing method. It is explanatory drawing which shows the example of a crank chamber pressure change. It is explanatory drawing which shows a data processing method. It is explanatory drawing which shows a data processing method. It is explanatory drawing which shows a data processing method. It is explanatory drawing which showed the implementation method of the intake air amount measuring device. (Second embodiment) It is explanatory drawing which showed arrangement | positioning of the pressure detection crank angle in a 2nd Example. It is explanatory drawing which shows the action | operation of the crank chamber compression type | mold 2 cycle engine of a piston valve intake system. It is explanatory drawing which shows the action | operation of a crankcase compression type 2 cycle engine of a reed valve intake system. It is explanatory drawing which shows the relationship of the timing of intake and scavenging of a crankcase compression type 2 cycle engine. It is explanatory drawing which showed arrangement | positioning of a pressure detection crank angle.

DESCRIPTION OF SYMBOLS 1 Cylinder body 2 Piston 3 Piston pin 4 Connecting rod 5 Crankshaft 6 Crankcase body 7 Throttle 8 Fuel injector 9 Intake cleaner box 10 Spark plug 11 Intake port 12 Exhaust port 13 Scavenging port 14 Crank chamber 15 Cylinder 16 Scavenging passage 17 Intake passage 18 Exhaust passage 19 Crank chamber pressure sensor 20 Bottom dead center sensor 21 Crank angle sensor 22 Crank angle indexing disk 23 Bottom dead center detection protrusion 24 Crank angle detection protrusion 25 Atmospheric pressure sensor 26 Intake temperature sensor 27 Engine control unit 28 Large Atmospheric pressure input unit 29, intake air temperature input unit 30 bottom dead center signal input unit 31 crank angle signal input unit 32 crank chamber pressure signal input unit 33 amplifier 34 A / D converter 35 crank angle position determination unit 36 crank chamber volume memory Part 37 intake air quantity calculating section 38 pressure sensor calibration unit 39 fuel injection amount calculating portion 40 bearing 41 Oil seal 42 flywheel magneto 43 reed valve 44 reed valve block 45 stopper 46 Shirube圧 pipe 47 a rubber pipe 48 clip 49 receiving surface
P pressure V volume G _c crank chamber air mass δG change in crank chamber air mass G _ia intake air amount per cycle T _int intake air temperature
T _m Intake temperature measurement value α Intake temperature correction value κ Specific heat ratio
R Air gas constant P _atm atmospheric pressure θ Crank angle N Number of crank angle points DV Constant related to volume difference AV Constant related to volume sum RV Constant related to volume ratio A _bore cylinder bore area S Piston displacement from top dead center C Pressure sensor pressure Sensitivity E ₀ Zero point travel
RPM engine speed RPM _s engine speed threshold Subscript _c Crank chamber Subscript _i i-th data Subscript _TDC top dead center

Claims (3)

  In a crankcase compression two-cycle engine, a method of obtaining the amount of intake air by detecting the crankcase pressure is used. One point in the period from the end of the scavenging opening to the beginning of opening of the intake opening and the scavenging opening from the end of closing the intake opening is used. Intake air based on crank chamber pressure, crank chamber volume and intake air temperature detected at a crank angle position including one point in the period until opening and at least one point in the period from the start of opening of the intake port to the end of closing of the intake port An intake air amount measuring device for a crankcase compression two-cycle engine characterized by calculating an amount.   Based on the crank chamber pressure and the crank chamber volume at two adjacent crank angle positions among the crank angle positions, it is determined whether air is flowing into the crank chamber from the intake passage or out of the crank chamber into the intake passage. After correcting the intake air temperature based on the result, the calculation of the intake air amount between the two crank angle positions is performed based on the crank chamber pressure, the crank chamber volume and the intake air temperature at the two crank angle positions. The intake air amount measuring device according to claim 1.   One point near the bottom dead center of the pressure sensor that detects the crank chamber pressure and 2 within either the period from the end of closing of the scavenging port to the start of opening of the intake port or the period from the end of closing of the intake port to the start of opening of the scavenging port The intake air amount measuring device according to claim 1, wherein calibration of the pressure sensitivity and the zero point movement amount of the pressure sensor is performed based on outputs at three crank angle positions in combination.

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