JP2008038793A - Control device for internal combustion engine - Google Patents

Abstract

A control device for an internal combustion engine capable of accurately calculating the friction torque of the internal combustion engine is provided.
A control device for an internal combustion engine is a device for calculating a friction torque in the internal combustion engine. Specifically, the control device for the internal combustion engine calculates the friction torque based on the load torque acquired by the torque sensor when the throttle valve is controlled to be fully opened during fuel cut during deceleration. When such control is executed, the pumping loss hardly occurs, so that the indicated torque can be regarded as approximately “0”. Therefore, the friction torque can be calculated with high accuracy based on the acquired load torque. In addition, by correcting the friction characteristics based on the calculated friction torque, it is possible to accurately control the output torque for the internal combustion engine.
[Selection] Figure 2

Description

  The present invention relates to a control device for an internal combustion engine that calculates friction torque in the internal combustion engine.

  2. Description of the Related Art Conventionally, a technique for estimating mechanical loss such as friction in order to obtain torque in a vehicle is known. For example, in order to obtain the indicated torque of an internal combustion engine, a technique for obtaining a friction torque has been proposed. Patent Document 1 proposes a technique for correcting a standard friction characteristic by calculating a friction torque based on an in-cylinder pressure, a crank angular acceleration, or the like in a neutral state or a clutch non-engagement state. Here, the condition for calculating the friction torque is set in order to accurately calculate the friction torque in a stable state.

JP 2005-330837 A

  However, in the technique described in Patent Document 1 described above, there are cases in which the friction torque is not accurately calculated under normal operating conditions because the conditions for calculating the friction torque do not match the normal operating conditions. .

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can accurately calculate the friction torque of the internal combustion engine.

  In one aspect of the present invention, a control device for an internal combustion engine provides the load torque from a throttle control unit that controls a throttle valve to be fully open and a torque sensor that detects a load torque during fuel cut during vehicle deceleration. Load torque acquisition means for acquiring, friction torque calculation means for calculating friction torque in an internal combustion engine based on the load torque acquired when the throttle control means controls the throttle valve to fully open, and the friction torque Correction means for correcting a friction characteristic that defines a relationship between a predetermined parameter and the friction torque based on the friction torque calculated by the calculation means.

  The control device for the internal combustion engine is preferably used for calculating the friction torque in the internal combustion engine. Specifically, the control device for the internal combustion engine calculates the friction torque based on the load torque acquired by the torque sensor when the throttle valve is controlled to be fully opened during fuel cut during deceleration. The load torque corresponds to the net torque output from the internal combustion engine. As described above, when the throttle valve is controlled to be fully opened during fuel cut during deceleration, almost no pumping loss occurs, so that the indicated torque can be regarded as approximately “0”. Therefore, according to the control device for an internal combustion engine, the friction torque can be accurately calculated based on the load torque. In addition, since it can be said that the rotational speed during fuel cut at the time of deceleration is near the rotational speed experienced by humans rather than in a neutral state or the like, the friction torque under normal operating conditions can be obtained with high accuracy.

  Further, the control device for the internal combustion engine corrects a friction characteristic that defines a relationship between a predetermined parameter and the friction torque based on the calculated friction torque. As a result, even when the friction characteristic changes due to aging or deterioration, the friction characteristic can be corrected appropriately using the accurately calculated friction torque. Therefore, it is possible to accurately control the output torque of the internal combustion engine using the friction torque obtained from the friction characteristics.

  Preferably, in the control apparatus for an internal combustion engine, the friction torque calculating means can calculate the friction torque based on the load torque and a dynamic loss torque determined from angular acceleration and moment of inertia. . That is, the indicated torque can be regarded as approximately “0” by the control by the throttle control means, so that the friction torque can be calculated using the load torque and the dynamic loss torque without using the indicated torque.

  In one aspect of the control apparatus for an internal combustion engine, when the torque sensor is provided on either the propeller shaft or the drive shaft, a torque converter is provided when the friction torque calculating means calculates the friction torque. A means for forcibly locking up is further provided.

  In this aspect, when the output of the torque sensor installed on the propeller shaft or the drive shaft is used, the torque converter is forcibly locked up when calculating the friction torque. By locking up the torque converter in this manner, it is possible to suppress the influence of the torque converter, so that the friction torque can be calculated with high accuracy.

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

[overall structure]
FIG. 1 is a schematic diagram showing a configuration of an internal combustion engine 1 to which a control device for an internal combustion engine according to the present embodiment is applied. In FIG. 1, solid arrows indicate gas flows, and broken arrows indicate input / output of signals.

  The internal combustion engine 1 mainly includes an intake passage 3, a throttle valve 4, a fuel injection valve 5, a cylinder (cylinder) 6a, an intake valve 7, an exhaust valve 8, an exhaust passage 9, and a spark plug 10. The crankshaft 11, the crank angle sensor 13, the torque sensor 14, and the water temperature sensor 15. The internal combustion engine 1 is mounted on a vehicle or the like, and is configured as, for example, a gasoline engine or a diesel engine.

  Air (fresh air) introduced from the outside passes through the intake passage 3, and the throttle valve 4 adjusts the flow rate of air passing through the intake passage 3. Specifically, the throttle valve 4 is controlled to an opening (throttle opening) corresponding to a control signal supplied from the ECU 30.

  The air that has passed through the intake passage 3 is supplied to the combustion chamber 6b of the cylinder 6a. The fuel injected by the fuel injection valve 5 is supplied to the combustion chamber 6b. In the combustion chamber 6b, the mixture of the supplied air and fuel is combusted by being ignited by ignition of the spark plug 10. In this case, the piston 6c reciprocates by combustion, and this reciprocating motion is transmitted to the crankshaft 11 via the connecting rod 6d and the crank arm 6e, and the crankshaft 11 rotates. Further, the exhaust gas generated by the above-described combustion is discharged to the exhaust passage 9.

  Further, an intake valve 7 and an exhaust valve 8 are provided on the cylinder 6a. The intake valve 7 controls conduction / interruption between the intake passage 3 and the combustion chamber 6b by opening and closing. Further, the exhaust valve 8 controls opening / closing of the exhaust passage 9 and the combustion chamber 6b by opening and closing.

  The crank angle sensor 13 is a sensor that detects a rotation angle (crank angle) of the crankshaft 11 and the like. For example, the crank angle sensor 13 outputs an angle signal and a reference angle signal for each predetermined piston position in addition to each unit crank angle.

  The torque sensor 14 is provided on the crankshaft 11 and is a sensor that detects torque. Specifically, the torque sensor 14 detects a load torque indicating a net torque output from the internal combustion engine 1. On the other hand, the water temperature sensor 15 detects the temperature of cooling water for cooling the internal combustion engine 1 (hereinafter simply referred to as “water temperature”). The crank angle sensor 13, the torque sensor 14, and the water temperature sensor 15 described above supply detection signals to the ECU 30, respectively.

  The ECU (Electronic Control Unit) 30 includes a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like (not shown). ECU30 acquires a detection signal from the various sensors mentioned above, and performs various processes and control based on this.

  In the present embodiment, the ECU 30 calculates a friction torque in the internal combustion engine 1 and performs a process of correcting a friction characteristic that defines a relationship between a predetermined parameter and the friction torque based on the calculated friction torque. Specifically, the ECU 30 controls the throttle valve 4 to be fully open during fuel cut when the vehicle is decelerating (hereinafter, such a vehicle state is also expressed as “deceleration F / C”). The friction torque is calculated based on the load torque detected by the torque sensor 14. Thus, the ECU 30 functions as a control device for the internal combustion engine according to the present invention. Specifically, the ECU 30 operates as throttle control means, load torque acquisition means, friction torque calculation means, and correction means.

[Friction torque calculation method]
Next, a friction torque calculation method according to this embodiment will be described. In the present embodiment, it is obtained by calculating the friction torque in the internal combustion engine 1. This is because in order to output a desired torque from the internal combustion engine 1 with high accuracy, it is necessary to obtain a friction torque corresponding to a so-called mechanical loss. Further, since it is difficult to directly detect the friction torque by a sensor or the like, the friction torque is obtained by calculating the friction torque.

  Here, the calculation method of the friction torque according to the present embodiment will be specifically described.

  The following equation (1) represents an equation for obtaining a load torque corresponding to the net torque output from the internal combustion engine 1.

Tl = Ti−J × (dω / dt) −Tf Formula (1)
In Expression (1), “Tl” represents a load torque (in other words, shaft torque) corresponding to the net torque output from the internal combustion engine 1, and “Ti” represents a torque generated by combustion in the internal combustion engine 1. The corresponding indicated torque is indicated, and “Tf” indicates the friction torque in the drive unit or the like. Specifically, the friction torque Tf is a torque due to mechanical friction of each fitting portion such as friction between the piston 6c and the inner wall of the cylinder 6a, and includes torque due to mechanical friction of auxiliary machinery. “J” represents the moment of inertia in the drive unit and the like, and “dω / dt” represents the angular acceleration of the crankshaft 11. Here, “J × (dω / dt)” is a dynamic loss torque (hereinafter referred to as “dynamic loss torque”) due to the angular acceleration (dω / dt) of the crankshaft 11.

  In the present embodiment, in order to accurately calculate the friction torque Tf, the friction torque Tf is calculated in a situation where the indicated torque Ti can be regarded as approximately “0”. Specifically, the friction torque Tf is calculated in a situation where the throttle valve 4 is controlled to be fully open (WOT; Wide Open Throttle) during fuel cut when the vehicle is decelerated. In such a situation, since the pumping loss hardly occurs, the indicated torque Ti can be regarded as approximately “0”. Thus, when the indicated torque Ti can be regarded as approximately “0”, the friction torque Tf can be calculated from the load torque Tl and the dynamic loss torque (J × (dω / dt)).

  Specifically, the friction torque Tf can be calculated based on the following equation (2). Expression (2) is an expression obtained by substituting “Ti = 0” into Expression (1) described above.

Tf = Tl−J × (dω / dt) Equation (2)
The load torque Tl in the first term on the right side of Equation (2) corresponds to the torque detected by the torque sensor 14. On the other hand, the moment of inertia J is determined by the mechanical parameters of the machine and is a value corresponding to the design value. The angular acceleration (dω / dt) is obtained based on the detection value of the crank angle sensor 13. Therefore, it can be said that the dynamic loss torque (J × (dω / dt)) in the second term on the right side of Equation (2) can be calculated. Accordingly, the friction torque Tf can be obtained using the obtained load torque Tl and dynamic loss torque (J × (dω / dt)).

  As described above, in the friction torque calculation method according to the present embodiment, the friction torque Tf is calculated when the throttle valve 4 is controlled to be fully opened during fuel cut (deceleration F / C) during vehicle deceleration. Therefore, it is possible to calculate the friction torque Tf with high accuracy. Further, since the rotational speed during the deceleration F / C can be said to be in the vicinity of the rotational speed experienced by humans rather than in the neutral state or the like, according to the present embodiment, the friction torque under normal operating conditions can be obtained with high accuracy. .

  In the present embodiment, when the friction torque Tf is calculated as described above, the calculated friction torque Tf is used to calculate predetermined parameters (such as the rotational speed of the internal combustion engine 1 and the water temperature) and the friction torque Tf. Is corrected (hereinafter also referred to as “friction torque map”). The reason why the friction torque map is corrected in this way is that the relationship between the predetermined parameter and the friction torque Tf changes due to changes over time or deterioration. The friction torque map mainly indicates characteristics (such as viscosity coefficient) in the temperature of the lubricating oil and the rotational speed of the internal combustion engine 1. The friction torque map is referred to when performing control for outputting a desired torque from the vehicle (hereinafter also referred to as “output torque control”).

[Friction torque map correction processing]
Next, the friction torque map correction process according to the present embodiment will be described. In the friction torque map correction process, calculation of the friction torque Tf in the internal combustion engine 1 and correction of the friction torque map using the calculated friction torque Tf are performed. Further, this process is repeatedly executed by the ECU 30 at a predetermined cycle while the vehicle is traveling.

  FIG. 2 is a flowchart showing the friction torque map correction process according to the present embodiment.

  First, in step S101, the ECU 30 determines whether or not the vehicle is under fuel cut during deceleration (during deceleration F / C). Here, the ECU 30 determines whether or not there is an operating state in which the friction torque Tf should be calculated. If the vehicle is decelerating F / C (step S101; Yes), the process proceeds to step S102. In this case, it can be said that the operating state in which the friction torque Tf is to be calculated. On the other hand, when the deceleration F / C is not being performed (step S101; No), the process exits the flow. In this case, it can be said that the operating state is not to calculate the friction torque Tf.

  In step S102, the ECU 30 controls the throttle valve 4 to fully open (WOT). Specifically, the ECU 30 supplies a control signal to the throttle valve 4 so that the throttle valve 4 is fully opened. This is because the friction torque Tf is calculated with high accuracy while minimizing the pumping loss. Then, the process proceeds to step S103.

  In step S103, the ECU 30 acquires a detection signal corresponding to the load torque Tl detected by the torque sensor 14. The load torque Tl is obtained as a negative value. Then, the process proceeds to step S104.

  In step S104, the ECU 30 obtains the angular acceleration (dω / dt) of the crankshaft 11 based on the crank angle ω detected by the crank angle sensor 13. Specifically, the ECU 30 calculates the angular acceleration (dω / dt) from the required time per angle. Then, the process proceeds to step S105.

  In step S105, the ECU 30 acquires the rotation speed and water temperature of the internal combustion engine 1. Specifically, the ECU 30 obtains the rotation speed of the internal combustion engine 1 based on the detection signal supplied from the crank angle sensor 13 and obtains the water temperature based on the detection signal supplied from the water temperature sensor 15. These rotation speed and water temperature are used to correct the friction torque map. When the above process ends, the process proceeds to step S106.

  In step S106, the ECU 30 calculates the friction torque Tf. In this case, since the indicated torque Ti can be regarded as approximately “0” because the deceleration F / C is being performed, the friction torque Tf can be calculated using the above-described equation (2). Specifically, the ECU 30 substitutes the load torque Tl acquired in step S103, substitutes the angular acceleration (dω / dt) acquired in step S104, and further stores it in a memory or the like. By substituting the inertia moment J, the friction torque Tf is calculated. When the above process ends, the process proceeds to step S107.

  In step S107, the ECU 30 corrects the friction torque map using the friction torque Tf calculated in step S106. Specifically, the ECU 30 updates the friction torque Tf corresponding to the rotation speed and the water temperature acquired in step S105 with the friction torque Tf calculated in step S106. For example, the ECU 30 corrects a two-dimensional map representing the friction torque Tf by the rotation speed of the internal combustion engine 1 and the water temperature. When the above process ends, the process exits the flow.

  According to the above friction torque map correction processing, even when the friction torque map changes due to aging or deterioration, the friction torque map can be corrected appropriately using the accurately calculated friction torque Tf. . As a result, the output torque control of the internal combustion engine 1 can be accurately performed using the friction torque Tf obtained from the friction torque map.

[Modification]
In the above, an embodiment has been described in which the friction torque map is corrected using the calculated friction torque Tf. Instead of correcting such a map, a polynomial indicating the friction characteristics is corrected based on the friction torque Tf. It is also possible.

  In the above, the embodiment has been described in which the load torque is acquired from the torque sensor 14 provided on the crankshaft 11 and the friction torque Tf is calculated based on the load torque. However, the present invention is not limited to this. In another example, it is also possible to install a torque sensor on the propeller shaft or drive shaft connected to the internal combustion engine 1, and obtain the load torque from this torque sensor to calculate the friction torque Tf.

  In yet another example, when using the output of a torque sensor installed on the propeller shaft or drive shaft, the torque converter can be forcibly locked up when calculating the friction torque Tf. This is for calculating the friction torque Tf with high accuracy. Specifically, by locking up the torque converter, the output of the internal combustion engine 1 is effectively transmitted to the propeller shaft or the drive shaft, thereby suppressing the influence of the torque converter.

  This will be specifically described with reference to FIG. FIG. 3 shows a system configuration example in the case of using the output of the torque sensor installed on the propeller shaft. The internal combustion engine 1 shown in FIG. 3 is the same as that shown in FIG. Therefore, the description for the internal combustion engine 1 is omitted here.

  In this configuration, the propeller shaft 23 is connected to the internal combustion engine 1 via a transmission (T / M) 22 and a torque converter 21. Specifically, the propeller shaft 23 is a propulsion shaft that is provided between the transmission 22 and a differential gear (not shown) and transmits the driving force obtained from the internal combustion engine 1 to the rear wheel side. The propeller shaft 23 is provided with a torque sensor 24 that detects torque. The torque sensor 24 detects the load torque Tl and supplies a detection signal corresponding to the load torque Tl to the ECU 31.

  The transmission 22 is provided between the torque converter 21 and the propeller shaft 23, and includes a plurality of gears (planetary gears) corresponding to the respective speed stages. The torque converter 21 is provided between the internal combustion engine 1 and the transmission 22 and functions as a clutch that intermittently transmits torque output from the internal combustion engine 1 to the transmission 22 by using a working fluid such as oil. And a function of increasing the torque and transmitting it to the transmission 22. The torque converter 21 is locked up by a control signal supplied from the ECU 31.

  The ECU 31 includes a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like (not shown). The ECU 31 acquires detection signals from the torque sensor 24 and the sensor (see FIG. 1) in the internal combustion engine 1, and performs various processes and controls based on the detection signals. Specifically, the ECU 31 performs a process of calculating the friction torque Tf in the internal combustion engine 1 and correcting the friction torque map using the calculated friction torque Tf.

  Specifically, the ECU 31 performs control to fully open the throttle valve 4 during deceleration F / C of the vehicle, and performs control to lock up the torque converter 21, and the load torque Tl detected by the torque sensor 24 at this time is controlled. Based on this, the friction torque Tf is calculated. The calculation method of the friction torque Tf and the correction method of the friction torque map are the same as the method performed by the ECU 30 described above. According to the processing by the ECU 31 described above, the torque converter 21 is locked up when calculating the friction torque Tf, so that the friction torque Tf can be calculated with high accuracy.

  FIG. 3 shows an example in which the friction torque Tf is calculated using the output of the torque sensor 24 installed on the propeller shaft 23, but instead of the torque sensor 24 installed on the propeller shaft 23, the drive shaft In the case where the friction torque Tf is calculated using the output of the torque sensor installed at, control for locking up the torque converter can be executed as described above.

1 is a schematic view showing a configuration of an internal combustion engine according to an embodiment of the present invention. It is a flowchart which shows the friction torque map correction process which concerns on this embodiment. It is the schematic which shows the system configuration example which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Intake passage 4 Throttle valve 6a Cylinder 9 Exhaust passage 11 Crankshaft 13 Crank angle sensor 14, 24 Torque sensor 15 Water temperature sensor 21 Torque converter 23 Propeller shaft 30, 31 ECU

Claims (3)

Throttle control means for controlling the throttle valve to fully open during fuel cut during deceleration of the vehicle;
Load torque acquisition means for acquiring the load torque from a torque sensor for detecting load torque;
Friction torque calculating means for calculating a friction torque in the internal combustion engine based on the load torque acquired when the throttle control means controls the throttle valve to fully open;
A control device for an internal combustion engine, comprising: correction means for correcting a friction characteristic that defines a relationship between a predetermined parameter and the friction torque by the friction torque calculated by the friction torque calculation means.   2. The control of the internal combustion engine according to claim 1, wherein the friction torque calculating unit calculates the friction torque based on the load torque and a dynamic loss torque determined from an angular acceleration and an inertia moment. apparatus.   In the case where the torque sensor is provided on either the propeller shaft or the drive shaft, the torque sensor further includes means for forcibly locking up the torque converter when the friction torque calculating means calculates the friction torque. 3. The control device for an internal combustion engine according to claim 1, wherein the control device is an internal combustion engine.

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