JP2005337092A - Torque controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To beforehand prevent a vehicle from becoming an unstable state in turning travel. <P>SOLUTION: After demand torque Tr is computed depending on an acceleration opening, etc., it is determined whether or not the turning travel depending on a steering angle θ of a steering wheel and a vehicle decelerating amount ΔV (steps 101 to 103). When determined as the turning travel, an estimated cornering force Cf necessary for the turning travel is computed using the steering angle θ and a vehicle speed V. After a demand torque upper limit Tmax is set so that the estimated value of a driving force estimated from the demand torque Tr does not exceed the target value (an upper limit capable of obtaining the estimated cornering force Cf or the value a little less than it) using the estimated cornering force Cf, etc., the demand torque Tr is limited by the demand torque upper value Tmax (steps 104 to 108). Thereby, before the vehicle becomes the unstable state (the occurred state of a skid of the vehicle, etc.), the demand torque Tr is limited to suppress the generated torque. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a torque control device for an internal combustion engine with an improved control method for the torque generated by the internal combustion engine.

  In a torque control system for an internal combustion engine mounted on a vehicle, a required torque is calculated based on a driver's accelerator operation amount (accelerator opening), and the intake air amount and fuel injection amount are controlled based on the required torque. Then, there is one that controls the generated torque. However, if the generated torque of the internal combustion engine is too large during turning of the vehicle, the wheels (tires) may exceed the grip limit of the wheels (wheels), and the wheels may slip.

Therefore, as a technique for improving the safety during turning of the vehicle, for example, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-107803), the wheel speed of the driving wheel and the wheel speed of the non-driving wheel are described. The wheel slip is detected based on the above, and when the wheel slip exceeds a predetermined threshold and the vehicle becomes unstable, the maximum transmittable torque is set based on the lateral acceleration of the vehicle, etc. In some cases, the throttle opening and ignition timing are controlled so that the generated torque is suppressed to the maximum transmittable torque.
JP-A-11-107803 (page 3, etc.)

  However, in the technique of Patent Document 1 described above, the vehicle slips temporarily during turning of the vehicle in order to suppress the torque generated by the internal combustion engine after the wheel slip exceeds a predetermined threshold and the vehicle becomes unstable. It is unavoidable that the vehicle becomes unstable, and there is a drawback in that the safety during turning of the vehicle cannot be sufficiently improved.

  The present invention has been made in consideration of such circumstances. Accordingly, the object of the present invention is to prevent the vehicle from becoming unstable during turning, and to prevent the vehicle from turning. It is an object to provide a torque control device for an internal combustion engine that can sufficiently improve the safety of the engine.

  In order to achieve the above object, a torque control device for an internal combustion engine according to claim 1 of the present invention calculates a required torque based on an accelerator opening and the like, and generates a generated torque of the internal combustion engine based on the required torque. In the system to be controlled, information for predicting the traveling direction of the vehicle (hereinafter referred to as “traveling direction prediction information”) is detected by the traveling direction prediction information detecting means, and the required torque is determined based on the traveling direction prediction information by the required torque limiting means. Is intended to be restricted.

  In this way, it is possible to determine the turning of the vehicle from the traveling direction prediction information, and to limit the required torque so that the generated torque is suitable for the turning. As a result, even if the required torque based on the accelerator opening is excessive for turning, the required torque is limited before the vehicle becomes unstable (such as a side slip of the wheel) during turning. Thus, the generated torque can be suppressed, so that the vehicle can be prevented from becoming unstable during turning, and the safety during turning of the vehicle can be sufficiently improved.

  In this case, the operation amount of the steering wheel may be detected as the traveling direction prediction information. Since the direction of the wheels changes according to the operation amount (steering angle) of the steering wheel and the traveling direction of the vehicle changes, the traveling direction of the vehicle can be accurately predicted by detecting the operation amount of the steering wheel. .

  Further, as in claim 3, the required torque may be limited after confirming a decrease in the vehicle speed. When the vehicle starts turning, cornering resistance acts on the wheels and the vehicle speed decreases, so if the required torque is limited after confirming the decrease in vehicle speed, the required torque will be reduced after the vehicle has surely entered turning. Can be limited. Accordingly, it is possible to prevent a problem that the drivability is deteriorated by limiting the required torque even though the vehicle is not turning.

  In general, when the vehicle is turning, a cornering force (centripetal force) acting in a direction perpendicular to the traveling direction of the wheels balances with the centrifugal force, so that the vehicle can turn in a stable state. In addition, the frictional force generated between the wheels and the road surface when the vehicle is turning is distributed to the driving force (or braking force) acting in the traveling direction and the cornering force acting in the direction perpendicular to the traveling direction. However, since the maximum value of the frictional force is determined by the ground contact load of the wheel, the road surface friction coefficient (friction coefficient between the wheel and the road surface), etc., the resultant force of the cornering force and the driving force (or braking force) is the maximum frictional force. Never exceed. For this reason, if the required torque is too large and the driving force (or braking force) acting on the wheels is too large when the vehicle is turning, the cornering force becomes small and cannot be balanced with the centrifugal force, and the sideslip of the wheels occurs. There is a fear.

  In consideration of such circumstances, the upper limit value of the required torque is set based on the traveling direction prediction information so that the estimated value of the driving force or braking force acting on the wheels does not exceed the target value, as in claim 4. It is better to set. Estimated cornering force (cornering force that can be balanced with centrifugal force) required for cornering can be obtained from the traveling direction prediction information, so the target value of the driving force (or braking force) acting on the wheels during cornering is estimated. Set the upper limit of the required torque so that the cornering force can be secured, or a value slightly smaller than that, and set the upper limit of the required torque so that the estimated value of the driving force (or braking force) estimated from the required torque does not exceed the target value. . In this way, the driving force (or braking force) during turning can be kept below the target value, and the estimated cornering force required for turning can be ensured, and the vehicle is in an unstable state ( It is possible to reliably prevent the wheel from slipping.

  As described above, there is a relationship that the resultant force of the cornering force and the driving force (or braking force) is less than the maximum frictional force. However, the estimated cornering force required for turning by changing the centrifugal force according to the vehicle speed. (Cornering force that can balance with centrifugal force) changes. Further, the maximum frictional force changes according to the ground load and the road surface friction coefficient according to the vehicle weight. For this reason, the upper limit value of the driving force (or braking force) that can secure the estimated cornering force changes according to the vehicle speed, the vehicle weight, and the road surface friction coefficient.

  Therefore, as in claim 5, when limiting the required torque based on the traveling direction prediction information, it is preferable to use at least one of the vehicle speed, the road surface friction coefficient, and the vehicle weight. In this way, the required torque upper limit value is set corresponding to the change in the upper limit value of the driving force (or braking force) that can secure the estimated cornering force according to the vehicle speed, the road surface friction coefficient, and the vehicle weight. The required torque upper limit value can be set with high accuracy.

  Further, as in claim 6, when the required torque is limited, the generated torque may be suppressed by adjusting at least one of the intake air amount, the ignition timing, and the fuel injection amount. If the generated torque is suppressed by adjusting the amount of intake air, it is possible to prevent sudden fluctuations in torque and reduce torque shock and improve fuel efficiency. Further, if the generated torque is suppressed by adjusting the ignition timing and the fuel injection amount, the generated torque can be suppressed with good response, and it is possible to cope with a sudden steering operation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a schematic configuration of the entire torque control system will be described with reference to FIG. A drive shaft 14 is connected to the output shaft of the engine 11, which is an internal combustion engine, via an automatic transmission 12 and a differential device 13, and drive wheels 15 are connected to both ends of the drive shaft 14. A wheel speed sensor 16 for detecting the wheel speed of the driving wheel 15 is provided in the vicinity of the driving wheel 15, and a wheel speed for detecting the wheel speed of the non-driving wheel 17 is provided in the vicinity of the non-driving wheel 17. A sensor 18 is provided. The vehicle speed is detected based on the output signal of the wheel speed sensor 18 of the non-driven wheel 17.

  Further, a steering angle sensor 20 (traveling direction prediction information detecting means) for detecting the steering angle (operation amount) of the steering wheel 19 is provided in the vicinity of the steering wheel 19 for operating the direction of the drive wheel 15, and the accelerator pedal 21. Is provided with an accelerator sensor 22 for detecting an accelerator opening (accelerator operation amount).

  Next, a schematic configuration of the engine control system will be described based on FIG. An air cleaner 24 is provided at the most upstream portion of the intake pipe 23 of the engine 11, and an air flow meter 25 for detecting the intake air amount is provided downstream of the air cleaner 24. On the downstream side of the air flow meter 25, a throttle valve 27 whose opening is adjusted by a motor 26 such as a DC motor, and a throttle opening sensor 28 for detecting the throttle opening are provided.

  Further, a surge tank 29 is provided on the downstream side of the throttle valve 27, and an intake pipe pressure sensor 30 for detecting the intake pipe pressure is provided in the surge tank 29. The surge tank 29 is provided with an intake manifold 31 for introducing air into each cylinder of the engine 11, and a fuel injection valve 32 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 31 of each cylinder. Yes. A spark plug 33 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 33.

  On the other hand, the exhaust pipe 34 of the engine 11 is provided with a catalyst 35 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas. / An exhaust gas sensor 36 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting lean or the like is provided.

  A cooling water temperature sensor 37 that detects the cooling water temperature and a crank angle sensor 38 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 38, the crank angle and the engine speed are detected.

  Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 39. The ECU 39 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 32 according to the engine operating state. The ignition timing of the spark plug 33 is controlled.

  Further, the ECU 39 executes each torque control program shown in FIGS. 3 to 5 to be described later, thereby calculating the required torque Tr based on the accelerator opening degree Ac and the like, and the engine 11 based on the required torque Tr. The torque generated is controlled.

  At that time, the ECU 39 determines whether or not the vehicle is turning based on the steering angle θ or the like of the steering wheel 19, and when it is determined that the vehicle is turning, the required torque upper limit value Tmax is determined based on the steering angle θ or the like. And the required torque Tr based on the accelerator opening degree Ac and the like is limited by the required torque upper limit value Tmax, so that the vehicle becomes in an unstable state (a state in which a side slip of the wheel 15 occurs) during turning. In advance.

Here, a method for calculating the required torque upper limit value Tmax will be described.
In general, when the vehicle is turning, a cornering force (centripetal force) acting in a direction perpendicular to the traveling direction of the wheels 15 balances with the centrifugal force, so that the vehicle can turn in a stable state. In addition, the frictional force generated between the wheel 15 and the road surface during turning of the vehicle is a driving force or a braking force acting in the traveling direction (hereinafter collectively referred to as “driving force”) and a direction perpendicular to the traveling direction. The maximum value of the frictional force is determined by the ground contact load of the wheel 15, the road surface friction coefficient (friction coefficient between the wheel 15 and the road surface), etc., so the cornering force and the driving force The resultant force does not exceed the maximum frictional force. For this reason, if the required torque Tr is too large and the driving force acting on the wheel 15 is too large when the vehicle is turning, the cornering force becomes small and cannot balance with the centrifugal force, and the skid of the wheel 15 may occur. is there.

  Therefore, the ECU 39 first changes the steering angle θ and the vehicle speed V using the relationship that the turning radius changes according to the steering angle θ and the centrifugal force changes, and the centrifugal force changes according to the vehicle speed V. Based on this, an estimated cornering force Cf (cornering force that can be balanced with centrifugal force) required for turning is calculated.

  Next, the estimated cornering force Cf and the wheel 15 are determined using the relationship that the maximum frictional force changes according to the ground contact load of the wheel 15 and the road surface friction coefficient, and the resultant force of the cornering force and the driving force is equal to or less than the maximum frictional force. Based on the ground contact load and the road surface friction coefficient, the target value of the driving force is set to an upper limit value that can secure the estimated cornering force Cf or a value slightly smaller than that, and the driving force estimated from the required torque Tr is estimated. The required torque upper limit value Tmax is set so that the value does not exceed the target value. As a result, the required torque upper limit value Tmax that achieves the maximum driving force or a slightly smaller driving force within a range in which no side slip of the wheel 15 occurs is set.

  Hereinafter, the processing contents of each program for torque control shown in FIGS. 3 to 5 executed by the ECU 39 will be described.

[Torque control]
The torque control program shown in FIG. 3 is executed at a predetermined cycle during engine operation, and serves as torque control means in the claims. When this program is started, first, in step 101, a required torque calculation program of FIG. 4 described later is executed to calculate the required torque Tr based on the accelerator opening degree Ac and the like.

  Thereafter, the process proceeds to step 102, and after the steering angle θ of the steering wheel 19 detected by the steering angle sensor 20 and the vehicle speed V detected by the wheel speed sensor 18 are read, the process proceeds to step 103 and the following (1) and ( Whether or not the vehicle is turning is determined by whether or not both of the conditions in 2) are satisfied.

(1) The absolute value of the steering angle θ is greater than or equal to the predetermined threshold θ1
(2) Decrease amount ΔV per predetermined period of vehicle speed V is greater than or equal to a predetermined deceleration determination value ΔV1. After determining that both of the above conditions (1) and (2) are satisfied, the vehicle is turning. Until the next condition (1) is not satisfied, the condition (2) is omitted and whether or not the vehicle is turning is determined only by whether or not the condition (1) is satisfied. To do.

  If it is determined in this step 103 that the vehicle is turning, the process proceeds to step 104, and an estimated cornering force Cf (a cornering force that can be balanced with centrifugal force) according to the steering angle θ and the vehicle speed V is represented by a map or an equation. Calculate using.

  Thereafter, the process proceeds to step 105, and the required torque upper limit value Tmax corresponding to the estimated cornering force Cf, the ground contact load of the wheel 15 and the road surface friction coefficient is calculated using a map or a mathematical expression. In this case, the required torque upper limit value Tmax is set so that the estimated value of the driving force estimated from the required torque Tr does not exceed the target value (the upper limit value that can secure the estimated cornering force Cf or a value slightly smaller than that).

  The ground load of the wheel 15 is calculated based on, for example, a vehicle weight stored in advance or a vehicle weight detected by a sensor or the like. The road surface friction coefficient is calculated using, for example, a road surface friction coefficient map corresponding to the vehicle speed V detected by the wheel speed sensor 18 and the acceleration Vg (change rate of the vehicle speed V).

  After calculating the required torque upper limit value Tmax, the routine proceeds to step 106, where it is determined whether the required torque Tr calculated in step 101 is larger than the upper limit value Tmax, and it is determined that the required torque Tr is larger than the upper limit value Tmax. If YES, the routine proceeds to step 107, where the required torque Tr is guarded with the upper limit value Tmax (Tr = Tmax). The processing of these steps 103 to 107 serves as required torque limiting means in the claims.

  On the other hand, if it is determined in step 106 that the required torque Tr is less than or equal to the upper limit value Tmax, or if it is determined in step 103 that the vehicle is not turning, the process proceeds to step 108 and step 101 described above. The required torque Tr calculated in the above is adopted as it is (Tr = Tr).

  After the final required torque Tr is thus set, the routine proceeds to step 109, where a required throttle opening degree calculation program shown in FIG. 5 described later is executed to calculate the required throttle opening degree Th based on the required torque Tr and the like. To do.

  Thereafter, the process proceeds to step 110, where a control signal is output so that the actual throttle opening coincides with the required throttle opening Th, the intake air amount is adjusted by adjusting the throttle opening, and the generated torque of the engine 11 is determined as the required torque. Control to Tr. As a result, when the required torque Tr is limited, the amount of intake air is adjusted to suppress the generated torque.

[Required torque calculation]
In the required torque calculation program of FIG. 4 executed in step 101 of FIG. 3, first, in step 201, the accelerator opening degree Ac detected by the accelerator sensor 22, the engine rotational speed Ne detected by the crank angle sensor 38, etc. are read. .

  Thereafter, the routine proceeds to step 202, where the required torque Tr corresponding to the accelerator opening degree Ac and the engine rotational speed Ne is calculated using a map or a mathematical expression. When a torque down request from an ABS (anti-lock brake system) or the like is generated, the required torque Tr is corrected according to the torque down request.

[Required throttle opening calculation]
In the required throttle opening calculation program of FIG. 5 executed in step 109 of FIG. 3, first, in step 301, the required torque Tr set in step 107 or 108 of FIG. 3 and the engine rotation detected by the crank angle sensor 38. The speed Ne, the atmospheric pressure Pa detected by the atmospheric pressure sensor (not shown), and the intake air temperature Ta detected by the intake air temperature sensor (not shown) are read.

  Thereafter, the routine proceeds to step 302, where the required air amount Gn corresponding to the required torque Tr and the engine rotational speed Ne is calculated using a map or mathematical formula, and then the routine proceeds to step 303, where the required air amount Gn and the engine rotational speed Ne are calculated. The required intake pressure Pm corresponding to the above is calculated using a map or a mathematical expression.

  Thereafter, the process proceeds to step 304, and the required throttle opening degree Th according to the engine speed Ne, the required air amount Gn, the required intake pressure Pm, the atmospheric pressure Pa, and the intake air temperature Ta is used using a map or a mathematical formula. To calculate.

  An execution example of the torque control of this embodiment described above will be described with reference to the time chart of FIG. As shown in FIG. 6, during engine operation, the required torque Tr is calculated based on the accelerator opening and the like, and the generated torque of the engine 11 is controlled based on the required torque Tr.

  Then, at the time t1 when the steering angle θ of the steering wheel 19 is equal to or greater than the threshold θ1 and the vehicle speed decrease ΔV is equal to or less than the deceleration determination value ΔV1, it is determined that the vehicle is turning, and the required torque upper limit value is determined based on the steering angle θ and the like. The process for calculating Tmax is started.

  Thereafter, at a time t2 when the required torque Tr based on the accelerator opening becomes larger than the required torque upper limit value Tmax, the required torque Tr is guarded with the upper limit value Tmax to limit the required torque Tr to the upper limit value Tmax. .

  In the conventional torque control, the required torque is limited at the time t3 when the side skid of the wheel occurs during turning. On the other hand, in this embodiment, when turning, the required torque Tr can be limited and the generated torque can be suppressed at time t2 before the side slip of the wheel occurs. It is possible to prevent the vehicle from entering a state, and it is possible to sufficiently improve the safety when the vehicle is turning.

  Further, in this embodiment, when the vehicle starts turning, the cornering resistance acts on the wheels to reduce the vehicle speed, and the required torque Tr is limited after confirming the decrease in the vehicle speed. Therefore, the required torque Tr can be limited after the vehicle has surely started turning, and the drivability is deteriorated by limiting the required torque Tr even though the vehicle is not turning. Can be prevented.

  In this embodiment, an estimated cornering force Cf (cornering force that can be balanced with centrifugal force) required for turning travel is calculated based on the steering angle θ and the vehicle speed V, and the driving force acting on the wheels 15 during the turning travel is calculated. Is set to an upper limit value that can secure the estimated cornering force Cf or a value slightly smaller than the upper limit value so that the estimated value of the driving force estimated from the required torque Tr does not exceed the target value. Therefore, the driving force acting on the wheel 15 during turning travel can be suppressed to a target value or less, and the estimated cornering force Cf necessary for turning traveling can be ensured reliably. It is possible to reliably prevent a stable state (a state in which a side slip of the wheel 15 occurs).

  Furthermore, in this embodiment, when calculating the required torque upper limit value Tmax, the vehicle speed V, the road surface friction coefficient, and the vehicle weight are used. Therefore, the estimated cornering force is set according to the vehicle speed V, the road surface friction coefficient, and the vehicle weight. The required torque upper limit value Tmax can be changed corresponding to the change of the upper limit value of the driving force that can be ensured, and the required torque upper limit value Tmax can be set with high accuracy.

  In this embodiment, when the required torque Tr is limited, the intake air amount is adjusted by adjusting the throttle opening to suppress the generated torque. This can reduce the fuel consumption.

  Note that when the required torque Tr is limited, the generated torque may be suppressed by adjusting the ignition timing and the fuel injection amount, and in this way, the generated torque can be suppressed with good response, It is possible to cope with a sudden handle.

  In the present embodiment, the steering angle θ of the steering wheel 19 is used as the traveling direction prediction information. However, the present invention is not limited to this. For example, the steering angle of the wheel 15 is used as the traveling direction prediction information. May use map information of a navigation system mounted on the vehicle.

It is a schematic block diagram of the whole torque control system in one Example of this invention. It is a schematic block diagram of an engine control system. It is a flowchart which shows the flow of a process of a torque control program. It is a flowchart which shows the flow of a process of a request torque calculation program. It is a flowchart which shows the flow of a process of a request | requirement throttle opening calculation program. It is a time chart which shows the execution example of the torque control of a present Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 15 ... Drive wheel, 16 ... Wheel speed sensor, 17 ... Non-drive wheel, 18 ... Wheel speed sensor, 19 ... Steering wheel, 20 ... Steering angle sensor (travel direction prediction information detection means), 22 ... Accelerator sensor, 23 ... Intake pipe, 27 ... Throttle valve, 32 ... Fuel injection valve, 33 ... Spark plug, 34 ... Exhaust pipe, 39 ... ECU (torque control means, required torque limiting means)

Claims (6)

In a torque control device for an internal combustion engine that includes a torque control means that calculates a required torque based on an accelerator opening and the like and controls a generated torque of the internal combustion engine based on the required torque.
Traveling direction prediction information detecting means for detecting information for predicting the traveling direction of the vehicle (hereinafter referred to as “traveling direction prediction information”);
A torque control device for an internal combustion engine, comprising: requested torque limiting means for limiting the requested torque based on the traveling direction prediction information.   The torque control device for an internal combustion engine according to claim 1, wherein the traveling direction prediction information detection unit detects an operation amount of a steering wheel as the traveling direction prediction information.   The torque control device for an internal combustion engine according to claim 1 or 2, wherein the required torque limiting means limits the required torque after confirming a decrease in vehicle speed.   The required torque limiting means sets an upper limit value of the required torque so that an estimated value of driving force or braking force acting on a wheel does not exceed a target value based on the traveling direction prediction information. The torque control device for an internal combustion engine according to any one of claims 1 to 3.   5. The required torque limiting means uses at least one of a vehicle speed, a road surface friction coefficient, and a vehicle weight when limiting the required torque based on the traveling direction prediction information. The torque control device for an internal combustion engine according to any one of the above.   2. The torque control unit according to claim 1, wherein when the required torque is limited, the generated torque is suppressed by adjusting at least one of an intake air amount, an ignition timing, and a fuel injection amount. The torque control device for an internal combustion engine according to any one of claims 1 to 5.

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