JP4905370B2 - Intake control device for internal combustion engine - Google Patents

Description

  The present invention relates to a technical field of an intake control device for an internal combustion engine capable of inertial supercharging such as impulse supercharging.

  As a method of supercharging intake air to an internal combustion engine, the intake control valve provided between the intake valve and the surge tank is opened, and the negative pressure in the cylinder is reduced using the piston lowering in the intake stroke. Impulse supercharging is known in which the impulse valve is promptly opened and an intake pressure wave is generated in the intake passage to positively utilize the inertial supercharging effect before it is shifted to the compression stroke. ing.

  For example, Patent Document 1 describes an engine output control device that determines the closing timing of an intake valve from a combination of an engine speed, a valve lift amount, and an intake pipe length. Patent Document 2 describes a pulse supercharging control device that performs at least one opening operation and one closing operation during one intake stroke. Patent Document 3 describes an engine intake device that changes the opening timing of a rotary valve in accordance with the engine speed. Patent Document 4 describes an engine intake device in which an intake layout is optimized in consideration of a pressure propagation path length.

JP 2003-41956 A JP 2007-224770 A JP-A 62-58016 JP 2002-81324 A

  However, even when the supercharging control based on the engine speed is executed, the timing at which the intake control valve is closed can be controlled to an optimal timing in a transient state where the engine speed changes, such as during acceleration or deceleration. Otherwise, there is a possibility that a sufficient supercharging effect cannot be obtained.

  The present invention has been made to solve the above-described problems, and can provide a sufficient supercharging effect even in a transient state in which the engine speed changes, thereby improving the engine torque. It is an object of the present invention to provide an intake control device for an internal combustion engine that can perform the above-described operation.

In one aspect of the present invention, an intake passage connected to a cylinder, an intake valve installed in the cylinder, an intake control valve installed in the intake passage and capable of adjusting an intake amount by opening and closing, An intake control device for an internal combustion engine applied to an internal combustion engine, comprising a surge tank installed in the intake passage upstream of the intake control valve, wherein the intake control is based on the rotational speed of the internal combustion engine The valve opening timing is controlled, and the closing timing of the intake control valve is determined based on the distance from the intake control valve to the opening end of the surge tank, the distance from the intake control valve to the intake valve, and the speed of sound. a control means for controlling said intake passage, a variable intake passage is an intake passage of variable length, said control means, said variable intake passage in correspondence to the change in length, closing of the intake control valve To control the timing.

An intake control device for an internal combustion engine includes an intake passage connected to a cylinder, an intake valve installed in the cylinder, an intake control valve installed in the intake passage and capable of adjusting an intake amount by opening and closing. And a surge tank installed in the intake passage on the upstream side of the intake control valve. The intake control apparatus for an internal combustion engine includes control means such as an ECU (Electronic Control Unit). The control means controls the opening timing of the intake control valve based on the number of revolutions of the internal combustion engine, and the distance from the intake control valve to the open end of the surge tank, the intake control valve to the intake valve The closing timing of the intake control valve is controlled based on the distance up to and the sound speed. In this way, even when the rotational speed of the internal combustion engine changes, the timing at which the intake control valve closes in the previous period can be controlled at an optimal timing to obtain a sufficient supercharging effect. The engine torque can be improved.
The intake passage is a variable intake passage that is a variable-length intake passage, and the control means controls the closing timing of the intake control valve in accordance with a change in the length of the variable intake passage. By doing so, even when the engine has a variable-length intake passage, the timing at which the intake control valve is closed can be controlled to an optimal timing.

  In another aspect of the intake control apparatus for an internal combustion engine, the sound speed is calculated based on either the intake air temperature or the outside air temperature. Thereby, the timing at which the intake control valve is closed can be controlled more accurately and optimally. For example, even when the intake air temperature or the outside air temperature changes greatly, such as during cold or high temperatures, the timing at which the intake control valve closes can be controlled to an optimal timing, The engine torque can be improved even during a transient time when the engine speed changes.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[overall structure]
FIG. 1 is a configuration diagram showing the configuration of an internal combustion engine according to each embodiment of the present invention. In FIG. 1, a solid line arrow indicates a gas flow, and a broken line arrow indicates a signal flow.

  An internal combustion engine (engine) is a diesel engine mounted as a driving power source in a vehicle such as an automobile, and includes a plurality of cylinders 12, an intake passage 13 and an exhaust passage 14 connected to each cylinder 12, and an intake passage. 13 and a turbocharger 18 arranged in series in the exhaust passage 14. The exhaust passage 14 is provided with an EGR (Exhaust Gas Recirculation) passage 17 for returning a part of the exhaust gas from the exhaust passage 14 to the intake passage 13. Hereinafter, a part of the exhaust gas recirculated by the EGR passage 17 is referred to as EGR gas. The EGR passage 17 is provided with an EGR cooler 23 for cooling the EGR gas and an EGR valve 33 for adjusting the amount of EGR gas. The EGR valve 33 is controlled by a drive signal S33 from the engine ECU 50a.

  In the intake passage (intake pipe) 13, an air cleaner 21, an air flow meter (A / F sensor) 41 that detects the amount of air (intake air) sucked from the outside, a compressor 18 a of the turbocharger 18, Intercooler 22, throttle valve 34 for adjusting the amount of intake air, surge tank 16 capable of storing intake gas (a mixed gas of EGR gas and intake air), and the amount of intake gas (intake amount) are adjusted. An intake control valve 31 is provided. The A / F sensor 41 detects the intake air amount and transmits a detection signal S41 corresponding to the detected intake air amount to the engine ECU 50a. The throttle valve 34 is controlled by a drive signal S34 from the engine ECU 50a. The intake control valve 31 is also called an impulse valve, and is controlled by a drive signal S31 from the impulse valve ECU 50c.

  The surge tank 16 is provided with an intake pressure sensor 43 and an intake air temperature sensor 42. The intake air temperature sensor 42 detects the temperature of the intake gas (intake air temperature), and transmits a detection signal S42 corresponding to the detected intake air temperature to the engine ECU 50a. The intake pressure sensor 43 detects the pressure of the intake gas (intake pressure) and transmits a detection signal S43 corresponding to the detected intake pressure to the engine ECU 50a.

  The exhaust passage 14 is provided with a turbine 18b of the turbocharger 18 and a catalyst 24. The catalyst 24 is, for example, a NOx occlusion reduction catalyst that occludes NOx in exhaust gas to reduce and purify it. Instead of the catalyst 24, an exhaust purification device that combines a particulate filter that collects particulate matter in the exhaust gas and the catalyst 24 may be used.

  The turbocharger 18 is configured such that the compressor 18a and the turbine 18b rotate integrally. Here, as shown in FIG. 1, the turbocharger 18 may be, for example, a variable capacity turbocharger including a variable nozzle vane 19 and capable of adjusting a supercharging pressure. In the variable capacity turbocharger, the supercharging pressure is adjusted by controlling the exhaust gas amount by adjusting the opening of the variable nozzle vane 19. Needless to say, as the supercharger, instead of using the turbocharger 18, another supercharger such as a supercharger or an electric supercharger may be used.

  An intake passage 13 and an exhaust passage 14 are connected to the combustion chamber 12b of the cylinder 12, and a fuel injection valve 5 for injecting fuel into the combustion chamber 12b is provided. The fuel injection valve 5 is controlled by a drive signal S5 from the injector ECU 50b. The cylinder 12 is provided with an intake valve 3 and an exhaust valve 4. The intake valve 3 controls conduction / interruption between the intake passage 13 and the combustion chamber 12b by opening and closing. The exhaust valve 4 is opened and closed to control conduction / interruption between the exhaust passage 14 and the combustion chamber 12b. In the cylinder 12, the force that pushes down the piston 12c to the bottom dead center is transmitted to the crankshaft 15 via the connecting rod 12d, and the crankshaft 15 rotates. Here, a crank angle sensor 44 is provided in the vicinity of the crankshaft 15. The crank angle sensor 44 detects the rotation angle (crank angle) of the crankshaft 15 and transmits a detection signal S44 corresponding to the detected crank angle to the engine ECU 50a.

  The ECU (Electronic Control Unit) 50 has a CPU, ROM, RAM, A / D converter, input / output interface, etc. (not shown), and detects and detects the operating state of the engine based on detection signals from various sensors. The engine is controlled based on the operating state. The ECU 50 includes an engine ECU 50a, an injector ECU 50b, and an impulse valve ECU 50c. The engine ECU 50 a receives detection signals from the A / F sensor 41, the intake air temperature sensor 42, the intake pressure sensor 43, and the crank sensors 44. Further, the engine ECU 50 a receives a detection signal corresponding to the pedal opening from the accelerator pedal 45, and receives a detection signal corresponding to the outside air temperature, which is a temperature outside the engine, from the outside air temperature sensor 46. The engine ECU 50a detects the operating state of the engine based on detection signals from these various sensors. The engine ECU 50a transmits a drive signal to the EGR valve 33 and the throttle valve 34 based on the detected operating state of the engine, and transmits a control signal to the injector ECU 50b and the impulse valve ECU 50c. The injector ECU 50b controls the fuel injection valve 5 based on the control signal from the engine ECU 50a, and the impulse valve ECU 50c controls the intake control valve 31 based on the control signal from the engine ECU 50a. The ECU 50 corresponds to an intake air control device for an internal combustion engine in the present invention, and specifically functions as a control means.

[First Embodiment]
An intake control method for an internal combustion engine according to the first embodiment will be described. First, the principle of impulse supercharging will be described with reference to FIG. FIG. 2 is a graph showing changes with respect to the crank angle with respect to each of the operation of the intake valve and the intake control valve and the in-cylinder pressure of the cylinder when the impulse charge is performed. In FIG. 2, TDC indicates the top dead center of the piston, and BDC indicates the bottom dead center of the piston.

  In the impulse supercharging, first, the intake valve 3 starts to be opened with the intake control valve 31 provided between the intake valve 3 and the surge tank 16 being closed. Therefore, since the piston 12c is lowered as the intake stroke proceeds, the in-cylinder pressure, more precisely, the pressure in the cylinder 12 and the intake passage 13 between the intake control valve 31 and the intake valve 3 is the intake pressure. The pressure is reduced from the average value of. The average value of the intake pressure here is, for example, the intake pressure detected by the intake pressure sensor 43. As indicated by the arrow 151, as the piston 12c descends, the reduced pressure trough gradually increases. When the intake control valve 31 is quickly opened at a time (crank angle) θop in the middle of the intake stroke, the reduced pressure is released and an intake pressure wave is generated in the intake passage 13. The intake pressure wave propagates in the intake passage 13 toward the surge tank 16. The intake pressure wave propagating in the intake passage 13 is reflected at the opening end of the surge tank 16 and its phase is inverted, and propagates in the intake passage 13 toward the intake valve 3. The intake control valve 31 is quickly closed at the timing (crank angle) θcl so as to capture the intake pressure wave whose phase is inverted. This time θcl is a value close to the crank angle when the piston is at bottom dead center. By doing so, as shown by the arrow 152, the in-cylinder pressure in the cylinder 12 becomes larger than the average value of the intake pressure, and the charging efficiency of the intake gas in the cylinder 12 increases. Thereby, the supercharging effect can be obtained and the engine torque can be improved.

  However, in a general impulse supercharging method, the timing at which the intake control valve 31 is closed is controlled based on the engine speed, so at the time of transition where the engine speed changes, such as during acceleration or deceleration, The timing at which the intake control valve 31 is closed cannot be controlled to an optimum timing, and there is a possibility that a sufficient supercharging effect cannot be obtained. For this reason, there is a fear that the engine torque cannot be improved during a transition in which the engine speed changes.

  Therefore, in the intake control method for the internal combustion engine according to the first embodiment, the ECU 50 controls the timing at which the intake control valve 31 opens based on the engine speed, but the timing at which the intake control valve 31 closes. Is controlled based on the distance from the intake control valve 31 to the opening end of the surge tank 16, the distance from the intake control valve 31 to the intake valve 3, and the sound speed.

  Specifically, the ECU 50 sets the time Tcl from when the intake control valve 31 is opened to when the intake control valve 31 is closed to Tcl, which can obtain a sufficient supercharging effect, using the following formula (1) Calculate using. Here, as the sound speed Vs, for example, 331.45 [m / sec], which is the sound speed when the intake air temperature becomes 0 ° C., is substituted. Note that the values of L1, L2, and Vs are recorded in advance in the ROM of the ECU 50 and the like. The ECU 50 closes the intake control valve 31 when it is determined that the time Tcl calculated by the equation (1) has elapsed since the intake control valve 31 was opened.

上述の式（１）は、次のようにして求められたものである。即ち、図１より、吸気制御弁３１が開弁すると、吸気圧力波は、吸気制御弁３１からサージタンク１６の開口端までの距離Ｌ１を伝播する。そして、吸気圧力波は、サージタンク１６の開口端で反射することにより位相が反転して、再度、サージタンク１６の開口端から吸気制御弁３１までの距離Ｌ１を伝播する。その後、吸気圧力波は、吸気制御弁３１から吸気弁３までの距離Ｌ２を伝播する。つまり、吸気圧力波は、吸気制御弁３１が開弁してから、２×Ｌ１＋Ｌ２の距離を伝播した後、吸気弁３に到達する。ここで、吸気圧力波の伝播速度を音速Ｖｓに等しいとすると、吸気制御弁３１が開弁してから吸気圧力波が吸気弁３に到達するまでの時間は、２×Ｌ１＋Ｌ２の距離を音速Ｖｓで割ることにより求められる。このようにして、上述の式（１）は求められる。

The above equation (1) is obtained as follows. That is, as shown in FIG. 1, when the intake control valve 31 is opened, the intake pressure wave propagates a distance L1 from the intake control valve 31 to the open end of the surge tank 16. Then, the intake pressure wave is reflected at the opening end of the surge tank 16 so that the phase is reversed, and again propagates the distance L1 from the opening end of the surge tank 16 to the intake control valve 31. Thereafter, the intake pressure wave propagates a distance L2 from the intake control valve 31 to the intake valve 3. That is, the intake pressure wave reaches the intake valve 3 after propagating a distance of 2 × L1 + L2 after the intake control valve 31 is opened. Here, assuming that the propagation speed of the intake pressure wave is equal to the sonic velocity Vs, the time from when the intake control valve 31 is opened until the intake pressure wave reaches the intake valve 3 is a distance of 2 × L1 + L2 as the sonic velocity Vs. It is calculated by dividing by. In this way, the above equation (1) is obtained.

  As can be seen from the above equation (1), the closing timing of the intake control valve 31 does not depend on the engine speed. Therefore, according to the intake control method during the internal combustion period according to the first embodiment, the timing at which the intake control valve 31 is closed is optimal for obtaining a sufficient supercharging effect even during a transition in which the engine speed changes. It is possible to control at a proper timing. In other words, according to the intake control method for the internal combustion engine according to the first embodiment, it is possible to improve the transient responsiveness of the impulse charge even during the transient time when the engine speed changes, and to improve the engine torque. be able to.

(Control processing of the first embodiment)
Next, control processing for the internal combustion engine according to the first embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing a control process of the internal combustion engine according to the first embodiment. In the control process of the internal combustion engine according to the first embodiment, the ECU 50 calculates the opening timing of the intake control valve 31 based on the engine speed, and then from the intake control valve 31 to the open end of the surge tank 16. The timing for closing the intake control valve 31 is calculated based on the distance, the distance from the intake control valve 31 to the intake valve 3, and the sound speed. In the control process according to the first embodiment, for example, the crank angle sensor 44 transmits a detection signal to the ECU 50 every time the crank angle changes by 30 ° CA. Therefore, the ECU 50 counts up the crank counter every time a detection signal is received from the crank angle sensor 44, that is, every time the crank angle changes by 30 ° CA.

  First, in step S101, the ECU 50 acquires the accelerator opening degree acc based on the detection signal from the accelerator pedal 45. In step S102, the ECU 50 determines the engine speed based on the detection signal from the crank angle sensor 44. Get Ne.

  In step S103, the ECU 50 determines whether to perform impulse supercharging based on the accelerator opening degree acc and the engine speed Ne. Specifically, the ECU 50 determines whether or not the engine is in a high load and low engine speed state based on the accelerator opening degree acc and the engine speed Ne, and the engine condition is high. If it is determined that the engine is in a low rotational speed state, impulse supercharging is permitted. For example, the ECU 50 holds in advance a map showing the relationship between the accelerator opening degree acc and the engine speed Ne and the permission of impulse supercharging, as shown in FIG. 4, and the accelerator opening degree acc is used using the map. Is determined to be equal to or greater than the predetermined value acc1 and the engine speed Ne is equal to or less than the predetermined value Ne1, the intake control valve 31 is closed to allow the impulse supercharging (step S103: Yes). . On the other hand, when the ECU 50 determines that the accelerator opening degree acc is smaller than the predetermined value acc1 or that the engine speed Ne is larger than the predetermined value Ne1, the ECU 50 prohibits impulse supercharging. As a result, the intake control valve 31 is opened (step S103: No), and this control process is returned.

  In step S104, the ECU 50 calculates the opening timing θop of the intake control valve 31. Specifically, the ECU 50 holds in advance a map showing the relationship between the engine speed Ne and the crank angle θop as shown in FIG. 5, and uses the map to intake air corresponding to the engine speed Ne. A timing θop for opening the control valve 31 is calculated. For example, as shown in FIG. 5, when the engine speed Ne is a predetermined value NeA, the ECU 50 calculates the crank angle θA corresponding to the predetermined value NeA as the timing θop for opening the intake control valve 31. .

  In step S105, the ECU 50 calculates the opening interruption counter cntop of the intake control valve 31. As described above, since the crank angle sensor 44 transmits a detection signal to the ECU 50 every time the crank angle changes by 30 ° CA, the ECU 50 divides the crank angle θop calculated in step S104 by 30 °. Thus, the opening interruption counter cntop (= θop / 30 °) of the intake control valve 31 can be calculated.

  In step S106, the ECU 50 calculates the opening timing timer reserved time top. The opening timing reservation timer time is a value obtained by converting the crank angle of the remainder when the crank angle θop is divided by 30 ° into time in step S104. Accordingly, the opening timing timer reserved time top is calculated by, for example, the following formula: top [sec] = (θop−30 ° × cntop) / (Ne [rpm] / 60) × (1/360 °). In this equation, the engine speed Ne [rpm] is divided by 60 to obtain the engine speed per second.

  In step S107, the ECU 50 determines the equation (1) based on the distance L1 from the intake control valve 31 to the opening end of the surge tank 16, the distance L2 from the intake control valve 31 to the intake valve 3, and the sound velocity Vs. ) To calculate the time Tcl from when the intake control valve 31 is opened until it is closed. Here, the values of L1, L2, and Vs are recorded in advance in the ROM of the ECU 50 or the like. Thereby, the optimal timing for closing the intake control valve 31 to obtain a sufficient supercharging effect can be obtained.

  In step S108, the ECU 50 acquires the value of the crank counter, and in the subsequent step S109, the ECU 50 determines whether or not the value of the crank counter matches the open interrupt counter cntop. If the ECU 50 determines that the value of the crank counter does not coincide with the open interrupt counter cntop (step S109: No), the ECU 50 returns to the process of step S108. On the other hand, when the ECU 50 determines that the value of the crank counter is equal to the open interrupt counter cntop (step S109: Yes), the ECU 50 proceeds to the process of step S110.

  In step S110, the ECU 50 sets a reservation timer for a drive signal for driving the intake control valve 31. Specifically, as shown in FIG. 6, the ECU 50 sets a reservation time top as the start time of the rise of the pulse signal, and sets the time Tcl calculated using the equation (1) as the rise time of the pulse signal. Set. While this pulse signal rises, the intake control valve 31 is opened. In step S111, the ECU 50 executes the operation of the intake control valve 31 in accordance with the setting in step S110, and then returns to the present control process. At this time, the intake control valve 31 is closed at an optimal timing to obtain a sufficient supercharging effect.

  As described above, it is possible to control the timing at which the intake control valve 31 closes to an optimal timing for obtaining a sufficient supercharging effect even during a transition in which the engine speed changes. The engine torque can be improved.

[Second Embodiment]
Next, an intake control method for an internal combustion engine according to the second embodiment will be described. In the intake control method for the internal combustion engine according to the first embodiment described above, the ECU 50 performs the distance L1 from the intake control valve 31 to the opening end of the surge tank 16, the distance L2 from the intake control valve 31 to the intake valve 3, The timing for closing the intake control valve 31 is controlled based on the sonic velocity Vs.

  Here, the speed of sound varies depending on the temperature of the medium through which the sound is transmitted (here, the intake air temperature). Therefore, as described in the first embodiment, when the sound speed Vs is fixed to 331.45 [m / sec], which is the value of the sound speed when the intake air temperature is 0 ° C., in the expression (1), for example, When the temperature is high, it is difficult to accurately obtain the time Tcl from when the intake control valve 31 is opened until it is closed, that is, the optimal timing for closing the intake control valve 31. There is a fear.

  Therefore, in the intake control method for the internal combustion engine according to the second embodiment, the ECU 50 calculates the sonic velocity Vs in Expression (1) based on the intake air temperature. In general, the sound speed Vs is a predetermined speed each time the medium temperature increases by 1 ° C. with respect to the sound speed Vs0 (eg, 331.45 [m / sec]) when the medium temperature (here, the intake air temperature) is 0 ° C. It has a property of increasing by a minute K (for example, 0.607 [m / sec], hereinafter K is referred to as a temperature coefficient). Therefore, the ECU 50 obtains a time Tcl from when the intake control valve 31 is opened to when it is closed using the following equation (2). In equation (2), the sound velocity Vs is obtained as a function of the intake air temperature T1. Here, the ECU 50 can obtain the intake air temperature T <b> 1 based on the detection signal from the intake air temperature sensor 42.

このようにすることで、第１実施形態に係る内燃機関の吸気制御方法を用いた場合と比較して、吸気制御弁３１の閉弁するタイミングを、より正確に、最適なタイミングに制御することができる。例えば、冷間時や高温時等のように、吸気温度が大きく変化する場合であっても、この内燃機関の吸気制御方法によれば、吸気制御弁３１の閉弁するタイミングを最適なタイミングに制御することができ、エンジン回転数が変化する過渡時においても、エンジントルクの向上を図ることができる。

By doing in this way, compared with the case where the intake control method of the internal combustion engine which concerns on 1st Embodiment is used, the timing which the intake control valve 31 closes is controlled more correctly to the optimal timing. Can do. For example, even when the intake air temperature changes greatly, such as when it is cold or hot, according to the intake control method for the internal combustion engine, the timing for closing the intake control valve 31 is set to the optimal timing. It is possible to control the engine torque, and it is possible to improve the engine torque even in a transient state where the engine speed changes.

  Further, instead of obtaining the sound speed Vs as a function of the intake air temperature T1, the sound speed Vs may be obtained as a function of the outside air temperature T2, as shown in the following equation (3). Here, the ECU 50 can obtain the outside air temperature T <b> 2 based on the detection signal from the outside air temperature sensor 46.

このようにしても、第１実施形態に係る内燃機関の吸気制御方法を用いた場合と比較して、吸気制御弁３１の閉弁するタイミングを、より正確に、最適なタイミングに制御することができる。例えば、冷間時や高温時等のように、外気温度が大きく変化する場合であっても、この内燃機関の吸気制御方法によれば、吸気制御弁３１の閉弁するタイミングを最適なタイミングに制御することができ、エンジン回転数が変化する過渡時においても、エンジントルクの向上を図ることができる。

Even in this case, it is possible to control the timing at which the intake control valve 31 closes more accurately and optimally than when the intake control method for the internal combustion engine according to the first embodiment is used. it can. For example, even when the outside air temperature changes greatly, such as when the temperature is cold or high, according to the intake control method for the internal combustion engine, the timing for closing the intake control valve 31 is set to the optimal timing. It is possible to control the engine torque, and it is possible to improve the engine torque even in a transient state where the engine speed changes.

[Third Embodiment]
Next, an intake control method for an internal combustion engine according to the third embodiment will be described. In the second embodiment, the ECU 50 obtains the intake air temperature T1 based on the detection signal from the intake air temperature sensor 42, obtains the sound velocity Vs based on the intake air temperature T1, and obtains the sound velocity Vs as a function of the intake air temperature T1. However, for example, some engines, such as a low-cost engine, do not have the intake air temperature sensor 42.

  Therefore, in the intake air control method for the internal combustion engine according to the third embodiment, the ECU 50 is based on the outside air temperature and the temperature increase due to the work of the turbocharger 18 (hereinafter referred to as “supercharger work”). Thus, the sound speed Vs is calculated.

  First, the case where the engine does not have the intercooler 22 will be described. In this case, the ECU 50 obtains a time Tcl from when the intake control valve 31 is opened to when it is closed using the following equation (4). In equation (4), the speed of sound Vs is obtained as a function of the outside air temperature T2 and the temperature increase Δtup due to the supercharger work.

式（４）を見ると分かるように、ＥＣＵ５０は、外気温度Ｔ２と過給機仕事による温度上昇Δｔｕｐの和を吸気温度（温度Ｔ３）として推測している。ここで、過給機仕事による温度上昇Δｔｕｐを求める方法としては、例えば、ＥＣＵ５０は、図７に示すような、エンジン負荷及びエンジン回転数Ｎｅと過給機仕事による温度上昇Δｔｕｐとの関係を示すマップを予め保持しておくことが考えられる。図７に示すマップでは、ハッチングがされた領域毎に夫々、予めΔｔｕｐの大きさ（Δｔｕｐ１〜Δｔｕｐ５）が設定されている。ＥＣＵ５０は、エンジン負荷とエンジン回転数Ｎｅとに基づいて決まる動作点が図７に示すマップ上のどの領域に位置するかを判定することにより、ΔｔｕｐがΔｔｕｐ１〜Δｔｕｐ５の何れかになるかを決定することができる。なお、他の方法として、ＥＣＵ５０は、物理モデルを用いて、過給機仕事による温度上昇Δｔｕｐを求めることとしてもよい。

As can be seen from the equation (4), the ECU 50 estimates the sum of the outside air temperature T2 and the temperature increase Δtup due to the supercharger work as the intake air temperature (temperature T3). Here, as a method for obtaining the temperature rise Δtup due to the supercharger work, for example, the ECU 50 shows the relationship between the engine load and the engine speed Ne and the temperature rise Δtup due to the supercharger work as shown in FIG. It is conceivable to hold the map in advance. In the map shown in FIG. 7, the size of Δtup (Δtup1 to Δtup5) is set in advance for each hatched region. The ECU 50 determines which region on the map shown in FIG. 7 is the operating point determined based on the engine load and the engine speed Ne, thereby determining which Δtup is any of Δtup1 to Δtup5. can do. As another method, the ECU 50 may obtain the temperature increase Δtup due to the supercharger work using a physical model.

  As described above, even in an engine that does not have the intake air temperature sensor 42, the speed of sound in the intake passage 13 can be estimated, and the intake air control method for the internal combustion engine according to the first embodiment. Compared with the case of using, the timing at which the intake control valve 31 is closed can be controlled more accurately and optimally.

  Next, the case where the engine has the intercooler 22 will be described. When the engine has the intercooler 22, the ECU 50 calculates the sonic velocity Vs based on the outside air temperature, the temperature rise due to the supercharger work, and the temperature fall due to the intercooler 22. And Specifically, the ECU 50 obtains a time Tcl from when the intake control valve 31 is opened to when it is closed using the following equation (5). In equation (5), the speed of sound Vs is obtained as a function of the outside air temperature T2, the temperature increase Δtup due to the supercharger work, and the temperature decrease Δtdown due to the intercooler 22.

式（５）を見ると分かるように、ＥＣＵ５０は、外気温度Ｔ２と過給機仕事による温度上昇Δｔｕｐとの和からインタークーラ２２による温度下降Δｔｄｏｗｎを引いた値を吸気温度（温度Ｔ４）として推測している。ここで、インタークーラ２２による温度下降Δｔｄｏｗｎは、例えば、以下に示すインタークーラ効率の式（６）から求めることができる。

As can be seen from equation (5), the ECU 50 estimates the intake air temperature (temperature T4) as a value obtained by subtracting the temperature decrease Δtdown due to the intercooler 22 from the sum of the outside air temperature T2 and the temperature increase Δtup due to the supercharger work. is doing. Here, the temperature drop Δtdown due to the intercooler 22 can be obtained, for example, from the following formula (6) of the intercooler efficiency.

具体的には、ＥＣＵ５０は、インタークーラ効率ηを予め実験などで求めておき、上述の式（６）において、インタークーラ入口温度Ｔｉｎを外気温度Ｔ２とし、インタークーラ入口温度Ｔｉｎとインタークーラ出口温度Ｔｏｕｔとの差分Ｔｉｎ−ＴｏｕｔをΔｔｄｏｗｎとすることにより、インタークーラ２２による温度下降Δｔｄｏｗｎを求めることができる。なお、他の方法として、ＥＣＵ５０は、物理モデルを用いて、インタークーラ２２による温度下降Δｔｄｏｗｎを求めることとしてもよい。

Specifically, the ECU 50 obtains the intercooler efficiency η through experiments and the like in advance, and in the above formula (6), the intercooler inlet temperature Tin is set as the outside air temperature T2, and the intercooler inlet temperature Tin and the intercooler outlet temperature are set. By setting the difference Tin−Tout from Tout to Δtdown, the temperature drop Δtdown by the intercooler 22 can be obtained. As another method, the ECU 50 may obtain the temperature decrease Δtdown by the intercooler 22 using a physical model.

  As described above, even in an engine that does not have the intake air temperature sensor 42 and is provided with the intercooler 22, the speed of sound in the intake passage 13 can be estimated. Compared to the case where the intake control method for an internal combustion engine according to the embodiment is used, the timing at which the intake control valve 31 is closed can be controlled more accurately and optimally.

[Fourth Embodiment]
Next, an intake control method for an internal combustion engine according to the fourth embodiment will be described. The intake control method for the internal combustion engine according to the fourth embodiment differs from the intake control method for the internal combustion engine according to the first embodiment when the intake passage 13 is a variable-length intake passage (variable intake passage). This is an intake control method. Specifically, in the fourth embodiment, the intake passage 13 is, for example, a variable intake passage in which the distance L1 from the intake control valve 31 to the opening end of the surge tank 16 is variable, and the length of the distance L1 varies. In response to this, the closing timing of the intake control valve 31 is controlled.

  Specifically, the ECU 50 obtains a time Tcl from when the intake control valve 31 is opened to when it is closed using Expression (1), from the intake control valve 31 to the opening end of the surge tank 16. The distance L1 is not a fixed value, but is substituted with the value of the distance L1 when the time Tcl is obtained instead. As a method for obtaining the distance L1 when obtaining this time Tcl, it may be obtained by measuring using an intake pipe length sensor, or it is used if the engine is a system that switches a plurality of intake passages. The design intake pipe length of the intake passage may be obtained as the distance L1. Furthermore, the ECU 50 may hold in advance a map that shows the relationship between the engine load and engine speed Ne and the distance L1, as shown in FIG. In the map shown in FIG. 8, the size of the distance L1 (L1a, L2a) is set in advance for each hatched area. In FIG. 8, the relationship L1a> L1b is established. That is, the distance L1 from the intake control valve 31 to the open end of the surge tank 16 is set longer as the engine speed decreases. The ECU 50 determines from which region on the map shown in FIG. 8 the operating point determined based on the engine load and the engine speed Ne is located, and thereby from the intake control valve 31 to the open end of the surge tank 16. It can be determined whether the distance L1 is L1a or L1b.

  In the above-described embodiment, the distance L1 from the intake control valve 31 to the opening end of the surge tank 16 is variable. However, the distance L1 is not limited to this. The distance L2 to the valve 3 may be variable. In this case, when obtaining the time Tcl from when the intake control valve 31 is opened until it is closed, the distance L2 from the intake control valve 31 to the intake valve 3 is not a fixed value, What is necessary is just to substitute the value of distance L2 at the time of calculating | requiring time Tcl.

  As described above, even with an engine having a variable-length intake passage, the timing at which the intake control valve 31 is closed can be controlled to an optimal timing.

  Note that it is also possible to execute a combination of the intake control method for the internal combustion engine according to the fourth embodiment and the intake control method for the internal combustion engine according to the second to third embodiments. By executing in combination with the intake control method for the internal combustion engine according to the second to third embodiments, the timing at which the intake control valve 31 is closed can be more accurately controlled to the optimal timing.

It is a block diagram which shows the structure of the internal combustion engine which concerns on each embodiment of this invention. It is a graph which shows the change with respect to the crank angle about the operation of an intake valve and an intake control valve, and the in-cylinder pressure of a cylinder at the time of implementation of impulse supercharging. It is a flowchart which shows the control processing of the internal combustion engine which concerns on 1st Embodiment. It is a graph which shows the relationship between an accelerator opening, an engine speed, and permission of impulse supercharging. It is a graph which shows the relationship between an engine speed and a crank angle. It is a graph which shows the change with respect to time of a crank counter and a drive signal. The graph which shows the relationship between the engine load and engine speed, and the temperature rise by supercharger work. It is a graph which shows the relationship between an engine load and engine speed, and an intake pipe length.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Intake valve 4 Exhaust valve 5 Fuel injection valve 12 Cylinder 13 Intake passage 14 Exhaust passage 15 Crankshaft 16 Surge tank 17 EGR passage 18 Turbocharger 22 Intercooler 31 Intake control valve 34 Throttle valve 42 Intake temperature sensor 44 Crank angle sensor 45 Accelerator pedal 46 Outside air temperature sensor 50 ECU

Claims (2)

An intake passage connected to the cylinder, an intake valve installed in the cylinder, an intake control valve installed in the intake passage and capable of adjusting an intake amount by opening and closing, and the upstream side of the intake control valve An intake control device for an internal combustion engine applied to an internal combustion engine having a surge tank installed in an intake passage,
Based on the number of revolutions of the internal combustion engine, the opening timing of the intake control valve is controlled, the distance from the intake control valve to the opening end of the surge tank, the distance from the intake control valve to the intake valve, the speed of sound , based on, a control means for controlling the closing timing of the intake control valve,
The intake passage is a variable intake passage that is a variable-length intake passage;
The intake control device for an internal combustion engine, wherein the control means controls the closing timing of the intake control valve in response to a change in the length of the variable intake passage .   The intake control device for an internal combustion engine according to claim 1, wherein the control means calculates the sound speed based on one of intake air temperature and outside air temperature.

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