TWI659151B - Atkinson cycle engine control method - Google Patents

Abstract

An Atkinson cycle engine control method includes the following steps. The engine control unit receives multiple torque commands transmitted by multiple controllers, determines whether an engine operation has entered a steady state operation, determines whether the engine is suitable for running in an Atkinson cycle, and adjusts a variable valve timing advance angle of the engine To a predetermined angle, and to adjust other elements of the engine.

Description

Atkinson cycle engine control method

The invention relates to a method for controlling an Atkinson cycle engine. In particular, there is an optimization control method for an Atkinson cycle engine.

As climate change brings various disasters to humans and the environment, extreme weather, melting glaciers, melting permafrost, death of coral reefs, sea level rise, ecosystem changes, increased flood and drought disasters, deadly heat waves, etc. Staged.

For more than a century, humans have been relying on fossil fuels to provide energy to meet their daily needs. The emission of greenhouse gases such as carbon dioxide has strengthened the greenhouse effect and triggered climate change. Destroying forests, producing refrigerants for refrigerators, industrialization of agriculture and animal husbandry, etc. will all exacerbate climate change.

Therefore, in order to cope with climate change, many major car manufacturers in the world have bet on researching vehicle energy-saving technologies in order to meet the increasingly stringent regulations and standards. The use of hybrid electric vehicles (HEVs) and electric vehicles (EVs) has become a trend.

Today, hybrid electric vehicles are still one of the development trends of the short- and medium-range automobile industry. Therefore, the energy efficiency of internal combustion engines is still the goal that major automakers are eager to improve. How to improve the efficiency of the internal combustion engine will help to improve the braking thermal efficiency of the driving vehicle, and can also reduce the impact of the car's driving process on climate change.

In view of this, the present invention discloses an Atkinson cycle engine control method to effectively improve the efficiency of the Atkinson cycle engine.

An embodiment disclosed in the present invention relates to a control method for an Atkinson cycle engine, which includes the following steps. First, the engine control unit receives a plurality of torque commands transmitted by a plurality of controllers, determines whether an engine operation has entered a steady state operation, determines whether the engine is suitable for running in an Atkinson cycle, and adjusts a variable valve timing of the engine. Advance the angle to a predetermined angle, and adjust other components of the engine.

The aforementioned engine control unit receives a plurality of torque commands transmitted by a plurality of controllers, including receiving a composite power control unit torque command, a tracking control system torque command, and a transmission control unit torque command.

Among them, the variable valve timing advance angle of the aforementioned adjustment engine is adjusted to a predetermined angle, and the variable valve timing advance angle is adjusted to 25 degrees.

In addition, adjusting other components of the engine further includes adjusting a fuel control unit to determine an amount of fuel in the engine and an injection start angle.

In one embodiment, the oil-based as _{m f, des = m f,} opn + m f, clos, _wherein, m _{f, opn} open-loop fuel quantity is _a, m _{f, clos} a closed loop fuel control correction amount, in after entering the closed loop control of fuel, according to the narrow-area type of oxygen sensor feedback voltage signal v _EGO, whether the in-cylinder air-fuel ratio that is too thick or too thin, then the use of proportional integral controller, determines the m _{f, clos} Correction:

Among them, P _{clc , rich} and P _{clc , lean} are the correction values of the rich oil and thin oil ratio respectively; I _{clc , rich} and I _{clc , lean} are the correction values of the rich oil and thin oil integration respectively; AFRm is the air-fuel ratio (Air-fuel ratio); t _rich and t _lean are times when the mixing ratio is too rich or too lean.

In addition, other components of adjusting the engine include adjusting an ignition control unit to control one of the engine's ignition advance angles.

Furthermore, other components of the adjustment engine further include an adjustment of an intake control unit. The air intake control unit includes a fresh gas controller and an exhaust gas recirculation gas controller. The fresh gas controller controls a valve opening and an intake pressure, and the exhaust gas recirculation gas controller controls an exhaust gas recirculation valve opening and an exhaust valve variable valve timing.

In an embodiment, the throttle opening degree and the throttle flow coefficient correspond to each other, and the throttle flow coefficients C _{d , th , des} :

Among them, A _th is the throttle cross-sectional area, R _th is the throttle gas constant, P _boost is the boost pressure, P _{im , des} is the engine intake manifold pressure, T _boostT is the boost temperature, and k _th is the specific heat of the throttle. The ratio, m _{th , des} is the amount of intake air flowing into the throttle.

Therefore, the method for controlling an Atkinson cycle engine of the present invention can effectively improve the efficiency of the Atkinson cycle engine and increase the power output of the Atkinson cycle engine.

100‧‧‧Atkinson cycle engine control method

110 ~ 150‧‧‧step

210‧‧‧ Fuel Control Unit

212‧‧‧oil volume

214‧‧‧Injection start angle

220‧‧‧Ignition control unit

222‧‧‧Ignition advance angle

230‧‧‧Air intake control unit

231‧‧‧Fresh Gas Controller

232‧‧‧ Throttle opening

233‧‧‧Variable valve timing of intake valve

234‧‧‧Inlet pressure

235‧‧‧Exhaust gas recirculation gas controller

236‧‧‧ Exhaust gas recirculation valve opening

237‧‧‧Variable valve timing of exhaust valve

In order to make the above and other objects, features, advantages, and embodiments of the present disclosure more comprehensible, the description of the drawings is as follows: FIG. 1 is an Atkinson cycle engine according to an embodiment of the present invention. Schematic diagram of the control method.

FIG. 2 is a schematic diagram of various control units in an Atkinson cycle engine control method according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a variable valve timing test result of an Atkinson cycle engine control method according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a control result of an exhaust gas recirculation valve of an Atkinson cycle engine control method according to an embodiment of the present invention.

The following describes the embodiments in detail with the accompanying drawings. However, the examples provided are not intended to limit the scope covered by this disclosure, and the description of the operation of the structure is not intended to limit the order in which it is performed. Any structure reassembled by components, the device with equal efficacy is based on Disclose what is covered. In addition, the drawings are for illustrative purposes only, and are not drawn to the original dimensions. In order to facilitate understanding, the same elements or similar elements in the following description will be described with the same symbols.

In addition, the terms used throughout the specification and the scope of patent applications, unless otherwise specified, usually have the ordinary meaning of each term used in this field, the content disclosed here, and the special content. . Certain terms used to describe this disclosure are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art on the description of this disclosure.

Regarding the "first", "second", ..., etc. used herein, they do not specifically refer to the order or order, nor are they used to limit the present invention. They are only used to distinguish elements described by the same technical terms Or just operate.

Secondly, the terms "including", "including", "having", "containing" and the like used in this article are all open-ended terms, which means including but not limited to.

If the engine wants to achieve the goal of low fuel consumption and low emissions, in addition to improving the internal combustion engine technology, designing a good engine control method is also a very important task. In addition to improving the Engine Management System (EMS), it can also effectively Improve engine efficiency.

Torque-based engine management system architecture derived from automobiles with electronic throttle in recent years. This architecture mainly uses the engine control unit (ECU) to calculate the current torque demand of the engine and then converts it. It becomes the control command of each actuating element on the engine to adjust the engine's air intake and combustion situation. The control method of the Atkinson cycle engine of the present invention is based on the aforementioned torque control architecture, thereby optimizing the efficiency of the Atkinson cycle engine.

First, refer to FIG. 1, which is a schematic flowchart of the control method of the Atkinson cycle engine according to the present invention. As shown in the figure, the Atkinson cycle engine control method of the present invention includes the following steps. First, in step 110, when the ECU receives various controllers in the vehicle, for example, the components are transmitted by the Hybrid Control Unit (HCU), the Traction Control System (TCS), and the transmission control unit. Torque command. Step 120: Determine whether the engine operation enters a steady state operation. Among them, the steady state operation of the engine can be judged by the engine speed and the estimated torque. After confirming that the engine has entered stable operation, in step 130, the ECU further determines whether the current operating condition is suitable for running the Atkinson cycle engine. In one embodiment, the ECU determines whether the current operating condition is suitable for running the Atkinson cycle engine by using a preset parameter, for example, based on an experimental data lookup table or a preset formula recorded in the ECU as The criterion of judgment does not depart from the spirit and scope of the present invention. When it is determined in step 120 that the engine operation has not entered a steady-state operation, or in step 130, the ECU judges that the current operating conditions are not suitable for the Atkinson cycle engine operation, the Atkinson cycle engine control method will return to step 110, and the ECU again Receiving various controls in the vehicle Torque command transmitted by the device.

When the ECU determines that the current operating condition is suitable for the Atkinson cycle operation, it proceeds to step 140 to adjust and determine the variable valve timing (Variable Valve Timing) advance angle to a predetermined angle. In one embodiment, the predetermined angle is about 25 degrees, but it is not limited thereto. However, since the operation of various components in the engine system will affect the engine running condition, when the VVT advance angle has not reached the predetermined angle, the ECU must continue to determine whether the engine has entered steady-state operation, that is, return to step 120 to perform Judge. When the VVT advance angle reaches a predetermined angle, step 150 further changes the operating timing and parameters of other components of the engine system, such as: fuel injection amount, ignition timing, intake pressure, and exhaust gas recirculation (Exhaust Gas Recirculation; EGR ) Valve opening, etc., so that Atkinson cycle engine has better fuel consumption performance.

Refer to FIG. 2, which is a schematic diagram showing various elements required for adjustment of the control method of the Atkinson cycle engine of the present invention. As shown in the figure, the torque output of the Atkinson cycle engine is mainly adjusted by the fuel control unit 210, the ignition control unit 220, and the intake control unit 230. The fuel control unit 210 determines a required fuel mass (Desire fuel mass) 212 and an injection start angle (Start of Injection (SOI) 214). The ignition control unit 220 controls a Desire spark advance 222. In the intake control unit 230, the path of the intake air can be divided into a Fresh Air-mass control unit 231 and an Excirculated Gas-Mass control unit 235. Among them, the fresh gas controller 231 can further control the throttle valve position (Desire throttle position) 232, the intake valve variable valve timing (Desire Intake Variable Valve Timing angle 233 and Desire manifold pressure 234. The exhaust gas recirculation gas controller 235 further controls the exhaust gas recirculation valve opening degree (Desire EGR valve position) 236 and the exhaust valve variable valve timing (Desire Exhaust Variable Valve Timing angle) 237. Among them, the intake valve variable valve timing 233 and the exhaust valve variable valve timing 237 are mainly used to switch the Atkinson cycle mode.

The parameters calculation and adjustment methods of each control unit will be described in detail below to optimize the efficiency of the Atkinson cycle engine. After entering the Atkinson cycle, the control commands of the control units on the engine are calculated to optimize the efficiency of the Atkinson cycle engine.

First, according to the friction torque T _{fric , estimate of the} current engine and the received torque command T _{brak , des} (that is, the brake torque command), the indicated torque demand of the engine can be calculated, and then equations (1) ~ (2) can be used Calculate the engine fuel mass flow rate demand m _{f , des} : T _{ind , des} = T _{brak , des} + T _{fric , estimate} (1)

Among them, T _{ind , des} is the torque required when the required ignition timing is at the Minimum Advance for Best Torque (MBT) position, and m _{f , des} is the mass flow rate requirement of the engine fuel in the engine control method. Q _HV is the heating value of the fuel, n is the number of cylinders, η _f is the fuel efficiency, AFR _des is the set air-fuel ratio, m _{int , des} is the calculated intake air mass, N is the engine speed, and n _event is the engine crankshaft revolution Number of power strokes per lap.

In one embodiment, the optimal ignition timing (MBT) is tested by using an engine in a laboratory to obtain relevant data.

In one embodiment, the friction torque T _{fric , estimate} can query the friction torque table established according to the experimental data of the corresponding engine, but the present invention is not limited thereto. η _f is the fuel efficiency, which can also be obtained by looking up the table of engine speed and intake manifold pressure. In addition, since the air-fuel ratio of the engine also affects the fuel efficiency of the engine, an additional one-dimensional look-up table can be used to further determine the fuel efficiency correction coefficient based on the air-fuel ratio set by the engine management system. The relevant data can be used to change the air-fuel ratio. Fuel ratio experiment, obtain relevant engine data for analysis, and store in ECU.

In addition, if the engine ignition is not at the optimal ignition timing position, it can be corrected using equation (4): T _{ind , des} = T _{ind , MBT} η _spark (4)

Among them, η _spark is the ignition timing efficiency. When the ignition timing is MBT, the efficiency is 100%. However, if the ignition timing is delayed from MBT, the actual output torque of the engine will decrease, which means that the ignition timing efficiency starts to decrease. Use the corresponding engine to change the ignition timing to obtain relevant data.

After determining the demand for the intake air mass flow rate of the engine, the intake control unit 230 needs to convert it into the required throttle opening 232, external exhaust gas recirculation valve opening 236, and turbine pressure relief valve opening. Equation (5) is calculated to classify the engine air intake and use equation (6) to convert the engine intake manifold pressure P _{im , des} at this time. This pressure command can be used to issue the opening degree of the turbine pressure relief valve to Achieving the intake pressure 234 is not limited to this.

among them, For the amount of intake air flowing in from the throttle valve, For the intake air flow from the external EGR valve, R _cyl is the gas constant in the cylinder, T _im is the intake manifold gas temperature, which can be measured by the intake temperature sensor, and V _d is the displacement of the cylinder. η _v is the volumetric efficiency.

In one embodiment, η _v volumetric efficiency, can be controlled intake manifold pressure and the engine rotation speed that lookup table and stored in the in ECU.

when After both P _{im and des are} determined, the equations (7) and (8) can be used to calculate the throttle flow coefficient demand.

Among them, C _{d , th , des} are throttle flow coefficients, which can be used to check the comparison table of throttle opening and throttle flow coefficients to obtain the throttle opening θ _{th, des} , and A _th is the throttle cut. Area, R _th is the throttle gas constant, P _boost is the boost pressure, which can be measured by the boost pressure sensor, T _boostT is the boost temperature, which can be measured by the boost temperature sensor, and k _th is the specific heat of the throttle ratio. In an embodiment, the throttle opening degree corresponds to the throttle flow coefficient. The comparison table of the throttle flow coefficient can be tested by the corresponding engine in the laboratory to obtain the data corresponding to the throttle opening degree and the flow coefficient. The invention is not limited to this.

You can refer to the above method to change the pressure and temperature to the exhaust pressure and exhaust temperature, and then convert it into the required EGR valve opening degree. Then, the ECU can control the operation of each component through the control unit.

Next, the fuel control unit 210 further determines the fuel injection quantity demand of the fuel injection nozzle, and further converts it into the fuel injection pulse width of the fuel injection nozzle. Before calculating the fuel injection demand of the injector, the fuel control unit 210 first determines the fuel quality requirement in the cylinder, which is mainly divided into two parts, one is the open-loop fuel amount, and the other is the closed-loop fuel control correction amount. See the equation ( 9): m _{f , des} = m _{f , opn} + m _{f , clos} (9)

Among them, m _{f and opn} are the amount of open-loop fuel, which is calculated in the same way as equation (2), and m _{f and clos} are the closed-loop fuel control corrections, which are determined when the ECU determines the changes in engine speed and engine output torque. When the engine is currently operating in a steady state, the fuel control unit 210 then enters closed-loop fuel control. After entering the closed-loop fuel control, first learn whether the air-fuel ratio in the cylinder is too rich or lean based on the feedback voltage signal v _{EGO of the} narrow-range oxygen-containing sensor, and then use the proportional-integral controller to determine m _{f , clos} correction, see equation (10):

Among them, P _{clc , rich} and P _{clc , lean} are the correction values of the rich oil and thin oil ratio respectively; I _{clc , rich} and I _{clc , lean} are the correction values of the rich oil and thin oil integral respectively; AFRm is the air-fuel ratio (Air-fuel ratio); t _rich and t _lean are respectively matched with the formula (10). The obtained mixture ratio is too rich or too lean. When the engine leaves steady state operation, the fuel control strategy immediately stops the closed-loop fuel control, and sets m _{f , clos is} set to 0.

In an embodiment, P _{clc , rich} and P _{clc , lean are} approximately equal to 0.9, and I _{clc , rich} and I _{clc , lean are} approximately equal to 0.5, which are all verified by experiments and can be stored in the ECU.

In one embodiment, the air-jet engine is taken as an example. After the fuel is injected from the fuel injection nozzle, a layer of oil film is formed on the wall of the intake pipe. Therefore, the fuel quality requirements in the cylinder can only be obtained after dynamic compensation of the oil film. The fuel injection volume of the injector needs to be m _{inj , EMS} . Because the fuel injection system of the airway injection engine uses a fixed injection pressure (3.5kg / cm2), when the pressure of the intake manifold changes, the pressure difference between the inlet and outlet ends of the nozzle will change, which will cause the same injection pulse width. The fuel injection amount is not the same, and the battery voltage will affect the fuel injection amount under the same injection pulse width. Therefore, the Atkinson cycle engine control method 100 of the present invention will also be based on the battery voltage and the fuel injection nozzle injection. The fuel demand determines the basic injection pulse width, and then multiplies it by the nozzle pressure difference correction factor C _pres calculated by equation (11) to get the final injection pulse width.

Among them, P _inj is the nozzle pressure, P _a is the atmospheric pressure, and P _m is the intake manifold negative pressure.

The spark plug ignition is controlled according to the ignition advance angle and the ignition coil magnetization closing angle. Generally speaking, the magnetization closing angle is set to about 3 ~ 5 milliseconds (millisecond; ms), which can saturate the coil magnetization, except at idle speed. In addition to cold-start pollution emission and closed-loop ignition control with knock sensors, the ignition advance angle is usually set at the MBT position.

The control of the throttle opening degree 232 is mainly based on the calculated door opening degree command θ _{th, des} combined with the throttle door position sensor feedback signal for closed-loop opening degree control.

It is worth noting that the Atkinson cycle operation mode is mainly achieved through the early opening and late closing of the valve. Therefore, valve timing control is extremely important. An oil control valve (OCV) is usually installed in the engine. It has an oil inlet hole and a drain hole. When this valve acts, it will control the valve timing device. Into or drain oil to control the valve timing. The valve timing is the valve opening position calculated by the ECU, which is obtained by comparing the output signals of the crankshaft position sensor and the camshaft position sensor. In one embodiment, it can use the proportional integrator to compare the advance angle command issued and the advance angle signal correction control command for feedback. Refer to FIG. 3, which is a schematic diagram of a variable valve timing test result of the Atkinson cycle engine control method 100 of the present invention. As shown in the figure, when the engine is running from stand (Stall) to idle (Idle), the valve advance angle is 0 degrees when the engine is at rest, and then the oil pressure is still being established during the start phase, so even if there is advance The corner command does not operate, and when it runs at idle speed, Began to act and reach control orders. In one embodiment, the valve advance angle is about 25 degrees.

Refer to FIG. 4, which is a schematic diagram showing the control results of the exhaust gas recirculation valve of the Atkinson cycle engine control method 100 of the present invention. As shown in the figure, after the PWM signal is output by the ECU, the EGR valve opening degree is converted according to the feedback current value. In an embodiment, the conversion method can use a dial indicator and a power supply to provide different currents, and then record the opening of the EGR valve corresponding to the different currents and establish it as a lookup table, and then use a proportional integrator to compare and release the The EGR valve opening command and the feedback EGR valve signal correction control command have achieved the required control results.

Finally, the intake pressure is controlled by an electronic turbo pressure relief valve. The pipeline of the electronic turbo pressure relief valve will be connected to three places, the compressor side, the relief valve mechanism side and the air filter side. The compressor side will Air is sent to the electronic pressure relief valve, and the control of the valve will affect the direction of the air flow. When the airflow flows into the pressure relief valve mechanism side, the valve on the turbine side will open, reducing the exhaust gas flowing in the turbine side, reducing the turbocharger speed and reducing the intake air volume, which will cause the intake air pressure to decrease. On the side, a large amount of exhaust gas will flow into the turbine end, which is used to increase the turbocharger speed and increase the intake air volume so that the intake air pressure rises. Therefore, the intake control unit 230 may use the calculated intake manifold pressure command and then perform closed-loop control based on the feedback Manifold Absolute Pressure (MAP) sensor signal.

In summary, the method for controlling an Atkinson cycle engine of the present invention can effectively improve the efficiency of the Atkinson cycle engine and increase the power output of the Atkinson cycle engine.

Although this disclosure has been disclosed as above in the form of implementation, it is not intended to limit this disclosure. Any person with ordinary knowledge in the field can make various changes and modifications without departing from the spirit and scope of this disclosure. Therefore, this disclosure The scope of protection shall be determined by the scope of the attached patent application.

Claims (11)

An Atkinson cycle engine control method includes: an engine control unit receives a plurality of torque commands transmitted by a plurality of controllers; and when the engine control unit receives the plurality of torque commands transmitted by the plurality of controllers, judges Whether an engine operation has entered a steady state operation; when it is judged that the engine operation has entered the steady state operation, it is judged whether the engine is suitable for running in an Atkinson cycle; when it is judged that the engine has been operated in the Atkinson cycle, After adjusting a variable valve timing advance angle of the engine to a predetermined angle, and after adjusting the variable valve timing advance angle of the engine to the predetermined angle, adjust other components of the engine. The Atkinson cycle engine control method according to claim 1, wherein the engine control unit receives a plurality of torque commands transmitted by a plurality of controllers, including receiving a composite power control unit torque command, and a tracking control system torque Command and a gearbox control unit torque command. The control method of the Atkinson cycle engine according to claim 2, wherein the variable valve timing advance angle of the engine is adjusted to a predetermined angle, and the variable valve timing advance angle is adjusted to 25 degrees . The method for controlling an Atkinson cycle engine according to claim 1, wherein the adjusting of other components of the engine includes adjusting a fuel control unit. The method for controlling an Atkinson cycle engine according to claim 4, wherein the fuel control unit determines an oil quantity of the engine and an injection start angle. The Atkinson cycle engine control method according to the requested item, wherein said the oil-based as _{m f, des = m f,} opn + m f, clos, _wherein, m _{f, opn} to open loop fuel quantity, m _{f , clos} is the closed-loop fuel control correction amount. After entering the closed-loop fuel control, according to the feedback voltage signal v _{EGO of the} narrow-range oxygen-containing sensor, learn whether the air-fuel ratio in the cylinder is too rich or too lean, and then use Proportional-integral controller to determine m _{f , clos} correction: Among them, P _{clc , rich} and P _{clc , lean} are the correction values of the rich oil and lean oil ratio, respectively; I _{clc , rich} and I _{clc , lean} are the correction values of the rich oil and lean oil respectively; AFRm is the air-fuel ratio. ratio); t _rich and t _lean are times when the mixing ratio is too rich or too lean. The method for controlling an Atkinson cycle engine according to claim 1, wherein the adjusting of other components of the engine includes adjusting an ignition control unit. The method for controlling an Atkinson cycle engine according to claim 7, wherein the ignition control unit controls one of the engines' ignition advance angle. The method for controlling an Atkinson cycle engine according to claim 1, wherein the adjusting of other components of the engine includes adjusting an intake control unit. The method for controlling an Atkinson cycle engine according to claim 9, wherein the intake air control unit adjusts a fresh gas controller and an exhaust gas recirculation gas controller, and the fresh gas controller controls a throttle opening and an intake valve. The exhaust gas recirculation gas controller controls an exhaust gas recirculation valve opening degree and an exhaust valve variable valve timing control. The Atkinson cycle engine control method according to claim 10, wherein the throttle opening degree corresponds to a throttle valve flow coefficient, and the throttle valve flow coefficients C _{d , th , des} : Among them, A _th is the throttle sectional area, R _th is the throttle gas constant, P _boost is the boost pressure, P _{im , des} is the engine intake manifold pressure, T _boostT is the boost temperature, and k _th is the specific heat of the throttle. ratio, It is the amount of intake air flowing into the throttle valve.