JP2015004348A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an occupant from feeling rapid acceleration at start while preventing engine stall at start.SOLUTION: A control device 10 for an internal combustion engine includes: maximum generating shaft torque calculation means (S10) for calculating maximum generating shaft torque that may be generated by increasing fuel injection amount without changing current engine speed and current intake air amount; surplus torque calculation means (S20) for calculating surplus torque that is a difference between the maximum generating shaft torque and torque necessary for maintaining idling; target torque range setting means (S30) for setting a target torque range within a torque range in which acceleration permitting starting of a vehicle and at start of the vehicle reaches acceleration allowable by an occupant; and torque control means (S40-S70) for controlling engine torque so that the surplus torque falls within the target torque range.

Description

  The present invention relates to torque control of an internal combustion engine.

  As control in an idle operation state of an internal combustion engine, idle feedback control for converging the engine rotational speed to a target idle rotational speed is known. According to this, idle operation can be maintained even when the operating environment, cooling water temperature, or the like changes.

  A torque obtained by subtracting the friction torque of the internal combustion engine from the torque generated by the internal combustion engine in the idling operation state when the vehicle is stopped is used for starting the vehicle.

  By the way, since the air density decreases at high altitudes, even if the intake air amount has the same volume, the substantial intake air amount decreases and the torque decreases. Also, powertrain friction is large during cold weather and decreases as warm-up progresses. For this reason, for example, in an idle operation state immediately after a cold start at high altitude, the torque used for vehicle start-up becomes small, and there is a possibility that the engine torque may be stalled without securing the drive torque necessary for start-up.

  As control for improving the startability, Patent Document 1 discloses increasing the target idle rotation speed to increase the intake air amount.

JP 11-315740 A

  However, the above document does not specifically describe how much the target idle rotation speed is increased. For this reason, the engine rotational speed at the time of starting becomes excessively high, and there is a possibility that the occupant may feel a sudden acceleration.

  In view of the above problems, an object of the present invention is to provide a control device capable of preventing an occupant from suddenly accelerating while starting while preventing an engine stall at the time of starting.

  According to an aspect of the present invention, the maximum generated shaft torque that can be generated by increasing the fuel injection amount while maintaining the current engine speed and the current intake air amount is calculated, and the maximum generated shaft torque and the idling operation are maintained. There is provided a control device for an internal combustion engine that calculates a surplus torque that is a difference from a necessary torque.

  The control device for the internal combustion engine sets the target torque range within a torque range in which the vehicle can start and the acceleration at the time of starting the vehicle is an acceleration that can be accepted by the occupant, and the engine torque is set so that the surplus torque falls within the target torque range. To control.

  According to the above aspect, since the engine torque is controlled within a torque range in which the vehicle can start and the acceleration at the time of starting the vehicle is an acceleration that can be accepted by the occupant, the engine stall at the time of starting is prevented, and the occupant feels sudden acceleration. Can be prevented.

FIG. 1 is a schematic configuration diagram of a vehicle to which an embodiment of the present invention is applied. FIG. 2 is a diagram for explaining the concept of the idle operation control of the present embodiment. FIG. 3 is a flowchart showing a torque control routine of the present embodiment. FIG. 4 is a flowchart showing a subroutine for calculating the maximum generated shaft torque. FIG. 5 is a limit λ calculation map.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a vehicle to which an embodiment of the present invention is applied.

  The vehicle is attached to an internal combustion engine 1, an automatic transmission 3 having a torque converter 2, a drive shaft 4, an axle 6 to which rotation of the drive shaft 4 is transmitted via a differential device 5, and the axle 6. Drive wheels 7. Note that the internal combustion engine 1 of the present embodiment is a diesel engine.

  Further, the vehicle has an inclination angle sensor 14 for detecting the inclination angle of the vehicle, a weight sensor 15 for detecting the vehicle weight, an atmospheric pressure sensor 16, an accelerator pedal opening sensor 17, and a brake pedal. A brake switch 18 for detecting whether or not the vehicle is running and a vehicle speed sensor 19. The detection signals of these sensors are read into the controller 10.

  Note that a so-called acceleration sensor is used as the tilt angle sensor 14. In the case of a vehicle having a towing mechanism, a sensor for detecting a towing weight may be provided.

  The vehicle weight here is the sum of the weight of the vehicle body and the weight of the passenger. Since the vehicle weight is known from the vehicle specifications, the weight sensor 15 detects the weight of the passenger. Specifically, the number of seat switches that are turned on is input to the controller 10 using a seat switch that detects whether an occupant is sitting in the seat. The controller 10 calculates the product of the number of seat switches turned on and the weight per passenger, and sets this as the vehicle weight. As for the weight per passenger, the detected value may be used as long as the weight of the passenger sitting on the seat can be detected as well as the seat switch ON / OFF. It may be used.

  The internal combustion engine 1 includes an air flow meter 11 that detects an intake air amount, a crank angle sensor 13 that detects an engine rotation speed, and a water temperature sensor 12 that detects a cooling water temperature. Is read.

  The intake air amount may be calculated using the temperature and pressure of the collector tank 8 and the engine rotational speed without using the air flow meter 11, or may be calculated using the excess air ratio and the fuel injection amount. May be.

  The controller 10 performs fuel injection control to the internal combustion engine 1 based on signals of the accelerator depression amount from the accelerator pedal opening sensor 17, the engine rotation speed from the crank angle sensor 13, and the intake air amount from the air flow meter 11. Do. If necessary, the fuel injection amount and the ignition timing are corrected based on the signals of the cooling water temperature from the water temperature sensor 12 and the atmospheric pressure signal from the atmospheric pressure sensor 16.

  The controller 10 includes a microcomputer that includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller 10 with a plurality of microcomputers.

  Further, during idle operation, the controller 10 sets a basic idle rotation speed (basic idle rotation speed), and executes idle operation control described below in order to improve startability from the idle operation state.

  FIG. 2 is a diagram for explaining the concept of idle operation control according to the present embodiment.

  The maximum generated shaft torques Tmax1 and Tmax2 in the figure are crankshaft torques (hereinafter also simply referred to as torque) that can be generated by increasing the fuel injection amount while keeping the intake air amount constant at the engine rotational speed. Similarly, the friction torques Tf1 and Tf2 are friction torques when the internal combustion engine 1 is operated.

  The maximum generated shaft torque Tmax1 and the friction torque Tf1 indicated by the solid line in the figure are values on an altitude land (hereinafter referred to as a lowland) equivalent to that near the coast. Further, the maximum generated shaft torque Tmax2 and the friction torque Tf2 indicated by broken lines in the figure are values on a land with a high altitude (hereinafter referred to as a highland) such as a mountain area.

  When the altitude is reached, the air density decreases due to a decrease in atmospheric pressure, so the maximum generated shaft torque decreases from Tmax1 to Tmax2. Further, when the cooling water temperature is low as in the cold start, the viscosity of the lubricating oil is high and the clearance of each part is small, so the friction torque increases from Tf1 to Tf2.

  Therefore, even when the maximum generated shaft torque Tmax1 is larger than the friction torque Tf1 in the entire rotational speed region in the warm-up state in the lowland, immediately after the cold start in the highland, the friction is higher than the maximum generated shaft torque Tmax2 in the low rotational speed region. The torque Tf2 may be larger. Since starting the vehicle requires a torque that is at least larger than the friction torque, if the friction torque is larger than the maximum generated shaft torque, the vehicle cannot start. Therefore, during the idling operation, control is performed so that the internal combustion engine 1 generates a torque larger than the friction torque.

  On the other hand, as the torque obtained by subtracting the friction torque from the maximum generated shaft torque increases, the acceleration at the start of the vehicle increases. If the acceleration increases excessively, a sense of rapid acceleration is given to the occupant. Therefore, the torque of the internal combustion engine 1 during idle operation is controlled to a magnitude that provides an acceleration that does not give the occupant a sudden acceleration feeling when the vehicle starts.

  That is, the torque of the internal combustion engine 1 during idle operation is larger than the lower limit value (start limit) of the torque required for vehicle start, and from the upper limit value (rapid acceleration limit) of the torque that gives an acceleration that does not give the passenger a feeling of rapid acceleration. Is also controlled to be smaller.

  Even with the same acceleration G, the acceleration feeling given to the occupant differs depending on the vehicle specifications such as noise including engine sound, attitude change and vibration accompanying acceleration, etc. Set individually by evaluation.

  FIG. 3 is a flowchart showing a specific control routine of the above control. This routine is repeatedly executed, for example, at intervals of several milliseconds during idle operation. That is, this routine is executed when the vehicle speed is zero and the accelerator pedal opening is zero. At the time of the first calculation, the engine speed is set to the basic idle speed.

  In step S10, the controller 10 calculates the maximum generated shaft torque by executing a subroutine described later.

  FIG. 4 is a flowchart showing a subroutine executed by the controller 10 in step S10.

  In step S100, the controller 10 reads detection signals for the engine speed, the intake air amount, and the coolant temperature.

  In step S102, the controller 10 calculates the limit λ by searching the map shown in FIG. 5 based on the engine speed and the intake air amount. FIG. 5 is a limit λ map, where the vertical axis represents torque and the horizontal axis represents excess air ratio. If the fuel injection amount is increased while the intake air is kept constant since the vehicle is operating leaner than the stoichiometric state, the excess air ratio shifts to the rich side and the torque increases. However, when it becomes richer than a certain excess air ratio, the torque remains constant even if the fuel injection amount is increased. The limit on the lean side of the excess air ratio at which the torque does not increase even when the fuel injection amount is increased is the limit λ. Therefore, the controller 10 stores the map of FIG. 5 for each engine speed before the intake air amount and the fuel injection amount increase, and calculates the limit λ by referring to this map.

  After calculating the limit λ in step S102, the controller 10 calculates the maximum injection amount Qfmax in step S104. The maximum injection amount Qfmax is calculated by the equation (1) from the limit λ (λlim) and the current intake air amount Qair.

    Qfmax = Qair / λlim (1)

  In step S106, the controller 10 calculates the fuel injection timing. Specifically, the fuel injection timing is calculated by referring to a map in which the maximum injection amount Qfmax and the coolant temperature are assigned.

  In step S108, the controller 10 calculates the maximum generated shaft torque by referring to a torque map that is preset and stored. The torque map used here is a map of the torque with respect to the fuel injection amount for each engine speed. The torque sensitivity with respect to the fuel injection amount in the torque map may be corrected using the coolant temperature and the fuel injection timing.

  When the maximum generated shaft torque is calculated as described above, the flow returns to the flowchart of FIG.

  In step S20, the controller 10 calculates surplus torque Tmrg. The surplus torque Tmrg here is a value obtained by subtracting a torque (hereinafter also referred to as a current torque) Teng currently generated by the internal combustion engine 1 from a maximum generated shaft torque Tmax. That is, the current torque Teng is calculated using the torque map for the fuel injection amount for each engine speed, and the value obtained by subtracting this from the maximum generated shaft torque Tmax is used as the surplus torque Tmrg.

  In step S30, the controller 10 sets a target torque range. The target torque range is a range of torque that satisfies the condition that the vehicle can start and does not give the passenger a feeling of rapid acceleration.

  Here, a method for calculating the surplus torque at the upper limit value of the target torque range (hereinafter, the maximum surplus torque Tmrgmax) and the surplus torque at the lower limit value (hereinafter, the minimum surplus torque Tmrgmin) will be described.

(Maximum surplus torque calculation method)
Even if the maximum surplus torque Tmrgmax is the smallest within the range where the running resistance can be assumed and the lightest within the range where the vehicle weight can be assumed, the acceleration at the start of the vehicle does not give the passenger a feeling of sudden acceleration. This is the upper limit of torque. In the present embodiment, since the vehicle is started, the running resistance does not include air resistance, but mainly includes rolling resistance and gradient resistance.

  The lightest state within the range where the vehicle weight can be assumed is a state where the occupant is one driver. The vehicle weight in this state is Mmin. Here, if the upper limit value of acceleration that does not give the occupant a sudden acceleration feeling is Gmax, the force required to accelerate the vehicle at the acceleration Gmax is represented by Mmin · Gmax.

  Further, when the minimum value of the vehicle inclination angle θ is θmin and the minimum value of the rolling resistance μ of the driving wheel 7 is μmin, the gradient resistance is expressed as Mmin · gsinθmin, and the rolling resistance is expressed as Mmin · gcosθmin · μmin. Here, the inclination angle is positive when going up and negative when going down. That is, the minimum inclination angle θmin sets the inclination angle of the steepest downhill within the range that can be assumed.

  The minimum value μmin of the rolling resistance of the drive wheel 7 is set to a minimum value within an assumed range. For example, a value is set when the thinnest driving wheel 7 among the sizes that the vehicle can be mounted is mounted and the road surface is in a smooth state just after paving.

  The sum of Mmin · Gmax, Mmin · gsinθmin, and Mmin · gcosθmin · μmin calculated as described above is added to the torque using the gear ratio of the automatic transmission 3, the transmission efficiency, the torque ratio of the torque converter 2, etc. The converted value is the maximum surplus torque Tmrgmax.

(Minimum surplus torque calculation method)
The minimum surplus torque Tmrgmin is the maximum within the range where the running resistance can be assumed, the maximum weight within the range where the vehicle weight can be assumed, and the torque that can start the vehicle even immediately after the cold start. Is the lower limit. As in the case of the maximum surplus torque Tmrgmax, the running resistance does not include air resistance, but mainly includes rolling resistance and gradient resistance.

  The maximum weight state within the range where the vehicle weight can be assumed is a state in which the number of passengers is the maximum number of passengers of the vehicle and the loading weight is the maximum loading weight of the vehicle. When towing, the maximum weight of the towed vehicle and cargo is also added. If the vehicle weight in this state is Mmax and the minimum acceleration required for starting the vehicle is Gmin, the force required to accelerate the vehicle at the acceleration Gmin is expressed by Mmax · Gmin.

  Further, when the maximum value of the vehicle inclination angle θ is θmax and the maximum value of the rolling resistance μ of the driving wheel 7 is μmax, the gradient resistance is Mmax · g sin θmax, and the rolling resistance is Mmax · gcos θmax · μmax. Here, the inclination angle is positive when going up and negative when going down. In other words, the maximum inclination angle θmax sets the inclination angle of the steepest uphill within an assumed range.

  The maximum value μmax of the rolling resistance of the drive wheel 7 is set to a maximum value within an assumed range. For example, a value is set when the road surface condition is bad such that the thickest driving wheel 7 among the sizes that can be mounted by the vehicle is mounted and unevenness is scattered. Further, the friction from the automatic transmission 3 to the drive wheels 7 is defined as Tflic.

  Mmmax · Gmin, Mmax · gsinθmax, Mmax · gcosθmax · μmax and Tflic calculated as described above are added together, and the gear ratio of the automatic transmission 3, the transmission efficiency, the torque ratio of the torque converter 2, etc. are used. The value converted into torque is the minimum surplus torque Tmrgmin.

  When setting the target torque range, the detected value of the tilt angle sensor 14 may be used instead of the minimum value θmin and the maximum value θmax of the tilt angle. Thereby, a target torque range more suitable for the current state can be set. Instead of the tilt angle sensor 14, the current tilt angle θ may be read using navigation information.

  When the target torque range is set as described above, the processing after step S40 is executed.

  In step S40, the controller 10 determines whether or not the surplus torque Tmrg is equal to or greater than the minimum surplus torque Tmrgmin. If the surplus torque Tmrg is equal to or greater than the minimum surplus torque Trgmin, the controller 10 executes the process of step S50. The process of step S60 is executed.

  In step S50, the controller 10 determines whether or not the surplus torque Tmrg is equal to or less than the maximum surplus torque Tmrgmax. If the surplus torque Tmrg is equal to or less than the maximum surplus torque Trgmax, the current routine is terminated. The process of S70 is executed.

  In step S60, the controller 10 increases the torque of the internal combustion engine 1 by increasing the fuel injection amount, for example, and ends the current routine. On the other hand, in step S70, the controller 10 decreases the torque of the internal combustion engine 1, for example, by decreasing the fuel injection amount, and ends the current routine. The increase / decrease amount of the fuel injection amount may be a predetermined constant amount. This is because by repeating this routine, the target torque range will be entered.

  As described above, the controller 10 calculates the current maximum generated shaft torque Tmax and surplus torque Tmrg (S10, S20), and further sets a target torque range in which the vehicle can start and does not give the occupant a sudden acceleration feeling. (S30). Then, torque control of the internal combustion engine 1 is executed so that the surplus torque Tmrg is within the target torque range (S40-S70).

  It is as follows when the effect of this embodiment mentioned above is put together.

(1) The controller 10 includes a maximum generated shaft torque calculating means (S10) for calculating a maximum generated shaft torque, a surplus torque calculating means (S20) for calculating surplus torque, and a target torque range setting means for setting a target torque range. (S30). Furthermore, the controller 10 includes torque control means (S40-S70) for controlling the engine torque so that the surplus torque falls within the target torque range.

  When the torque of the internal combustion engine 1 is changed beyond the maximum generated shaft torque at the current engine speed, it is necessary to change not only the fuel injection amount but also the intake air amount. However, the change in the intake air amount causes a response delay unlike the change in the fuel injection amount. For this reason, even if an attempt is made to increase the torque after detecting a lack of torque at the time of starting, there is a possibility that the engine will stall due to a response delay of the intake air amount.

  In this respect, the controller 10 sets a target torque range within a torque range in which the vehicle can start and the acceleration at the time of starting the vehicle is an acceleration that the occupant can tolerate, and the maximum generated shaft torque and the torque necessary for maintaining idle operation are set. The engine torque is controlled so that the surplus torque as the difference falls within the target torque range. Therefore, it is possible to reliably start the vehicle without being affected by the response delay of the intake air amount, and to prevent the passenger from feeling a sudden acceleration.

(2) When the fuel injection amount is increased at the current engine speed and the current intake air amount, the controller 10 sets a limit λ that is a limit value of the excess air ratio at which the torque increases with the increase in the fuel injection amount. The maximum generated shaft torque is calculated based on the fuel injection amount at the limit λ and the current engine speed. Thereby, the maximum generated shaft torque can be accurately calculated.

(3) Since the controller 10 estimates the torque necessary for maintaining the idle state based on the friction of the power train, the estimation accuracy of the torque necessary for maintaining the idle state is taken into consideration by considering the change according to the temperature of the friction. Will improve.

(4) The controller 10 sets the lower limit of the target torque range as the start limit and the upper limit as the rapid acceleration limit, and increases the engine torque when the surplus torque falls below the lower limit of the target torque range, and the surplus torque exceeds the upper limit of the target torque range. When it becomes, reduce the engine torque. Further, the controller 10 calculates the target torque range based on the vehicle state including the number of passengers, the inclination angle, the presence or absence of towing, and the like. As a result, it is possible to reliably start the vehicle and prevent the occupant from feeling a sudden acceleration.

(5) Since the controller 10 uses the mass flow rate as the intake air amount in the above calculation, it can calculate the torque according to the change in altitude.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Torque converter 3 Automatic transmission 10 Controller 11 Air flow meter 12 Water temperature sensor 13 Crank angle sensor S10 Maximum generation shaft torque calculation means S20 Surplus torque calculation means S30 Target torque range setting means S40-S70 Torque control means

Claims (7)

Maximum generated shaft torque calculating means for calculating the maximum generated shaft torque that can be generated by increasing the fuel injection amount while maintaining the current engine speed and the current intake air amount;
Surplus torque calculating means for calculating a surplus torque that is a difference between the maximum generated shaft torque and a torque necessary for maintaining idle operation;
Target torque range setting means for setting a target torque range within a torque range in which the vehicle can start and the acceleration at the time of starting the vehicle is an acceleration that can be accepted by the occupant;
Torque control means for controlling engine torque so that the surplus torque falls within the target torque range;
A control device for an internal combustion engine, comprising: The control apparatus for an internal combustion engine according to claim 1,
The maximum generated shaft torque calculation means is a limit that is a limit value of an excess air ratio at which the torque increases as the fuel injection amount increases when the fuel injection amount is increased at the current engine speed and the current intake air amount. A control apparatus for an internal combustion engine, wherein λ is calculated, and the maximum generated shaft torque is calculated based on a fuel injection amount at the limit λ and a current engine speed. The control apparatus for an internal combustion engine according to claim 1 or 2,
The control device for an internal combustion engine, wherein the surplus torque calculating means estimates a torque necessary for maintaining idle operation based on powertrain friction. The control apparatus for an internal combustion engine according to any one of claims 1 to 3,
The control device for an internal combustion engine, wherein the torque control means increases the engine torque when the surplus torque becomes equal to or less than a lower limit of the target torque range. The control apparatus for an internal combustion engine according to any one of claims 1 to 4,
The control device for an internal combustion engine, wherein the torque control means reduces the engine torque when the surplus torque becomes equal to or greater than an upper limit of the target torque range. The control apparatus for an internal combustion engine according to any one of claims 1 to 5,
The control apparatus for an internal combustion engine, wherein the target torque range setting means estimates an upper limit value and a lower limit value of the target torque range based on a vehicle state. The control apparatus for an internal combustion engine according to any one of claims 1 to 6,
The control device for an internal combustion engine, wherein the maximum generated shaft torque calculation means uses a mass flow rate of intake air as the current intake air amount.

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