JP5134494B2 - Engine control device - Google Patents

Description

  In particular, the present invention relates to an engine control apparatus that appropriately maintains the pressure in an intake manifold when the vehicle is in an idle state or coast state where the driver depresses an accelerator pedal.

  In general, in intake control of an engine, a basic intake air amount is set to compensate for engine operation at an appropriate intake manifold pressure even during idling or coasting when the driver depresses the accelerator pedal. . For example, in an engine having an electronically controlled throttle valve that is controlled to open and close by a motor or the like, in general, in addition to the throttle opening calculated according to the accelerator pedal depression amount by the driver, etc., the basic intake air amount The corresponding throttle opening is calculated, and these are added together to set the final target throttle opening. By doing so, the intake manifold pressure is maintained above the specified guard pressure even when the accelerator pedal is released. Such control is also performed for an engine in which an accelerator pedal and a throttle valve are mechanically connected by a cable or the like. In this type of engine, for example, the opening of a bypass passage that bypasses the throttle valve is set to ISC. This is realized by controlling the opening according to the basic intake air amount through a valve or the like.

By the way, in the engine control as described above, the basic intake air amount set to maintain a prescribed intake manifold pressure is generally set under conditions such as a predetermined external pressure and temperature in a lowland. For this reason, for example, when the driver depresses the accelerator pedal at a high altitude where the atmospheric pressure is low, the intake manifold pressure is significantly lower than a specified guard pressure, and there is a possibility that backflow of engine oil or the like may occur. Therefore, in order to prevent such a decrease in the intake manifold pressure, in this type of engine intake control, PID control based on the deviation between the target intake air amount and the actual intake air amount (see, for example, Patent Document 1) Etc. are widely performed.
JP-A-2-149737

  However, in order to optimize the pressure in the intake manifold with high responsiveness using PID control or the like as described above, various setting operations become complicated, such as the need to finely tune the gain of each term. On the other hand, for example, it is conceivable to prepare a plurality of patterns or the like for setting the basic intake air amount etc. according to the outside air pressure, the temperature in the engine room, etc. Requires an enormous amount of data, which not only complicates the setting work, but also may squeeze the ROM capacity and the like.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine control device that can appropriately maintain the pressure in the intake manifold by simple and responsive control.

  The present invention maintains ISC intake air amount calculation means for calculating the ISC intake air amount necessary for avoiding engine stall, and maintains the intake manifold pressure when the accelerator is in an off state above a predetermined guard pressure. A guard intake air amount calculating means for calculating a guard intake air amount necessary for the operation, and a basic intake air necessary for operating the engine based on a value that is larger of either the ISC intake air amount or the guard intake air amount. Basic intake air amount calculating means for calculating the amount, wherein the guard intake air amount calculating means is a value obtained by dividing the guard pressure by the intake manifold pressure detected by the sensor, and the intake air of the engine detected by the sensor A multiplication value with an air amount is set as the guard intake air amount.

  In addition, the present invention provides an ISC intake air amount calculation means for calculating an ISC intake air amount necessary for avoiding engine stall, and an intake manifold pressure when the accelerator is in an off state above a predetermined guard pressure set in advance. A guard intake air amount calculating means for calculating a guard intake air amount necessary to maintain the basic value necessary for operating the engine based on a value that is larger than either the ISC intake air amount or the guard intake air amount. A basic intake air amount calculating means for calculating an intake air amount, wherein the guard intake air amount calculating means includes a value obtained by dividing the guard pressure by an intake manifold pressure detected by a sensor, and the guard intake air amount. A multiplication value with the previous value is set as the current guard intake air amount.

  According to the engine control apparatus of the present invention, the pressure in the intake manifold can be properly maintained by simple and responsive control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an engine control system, FIG. 2 is a flowchart showing a target throttle opening calculation routine, FIG. 3 is a diagram showing a guard pressure calculation table, and FIG. It is a flowchart which shows the subroutine of the modification of air quantity calculation.

  In FIG. 1, reference numeral 1 denotes an engine, and a cylinder head 2 of the engine 1 is provided with an intake port 3 and an exhaust port 4 communicating with a combustion chamber 1 a of the engine 1. The cylinder head 2 is provided with an intake valve 5 that opens and closes the intake port 3 and an exhaust valve 6 that opens and closes the exhaust port 4, and further, an ignition plug 7 that exposes the discharge electrode at the tip in the combustion chamber 1a. It is attached.

  An intake manifold 8 is communicated with the intake port 3, and an injector 9 having a fuel injection port directed toward the intake valve 5 is disposed on the intake manifold 8 immediately upstream of the intake port 3. .

  In addition, an intake passage 10 is communicated with an air chamber 8 a formed at the upstream collecting portion of the intake manifold 8, and a throttle valve 11 is disposed in the middle of the intake passage 10. In this embodiment, the throttle valve 11 is an electronically controlled throttle valve whose opening degree is electronically controlled. A throttle actuator 20 such as a motor is connected to the throttle valve 11. Further, an air cleaner 12 is disposed in the middle of the intake passage 10 on the upstream side of the throttle valve 11.

  On the other hand, an exhaust passage 14 communicates with the exhaust port 4 via an exhaust manifold 13, and a catalyst 15 is interposed in the middle of the exhaust passage 14.

  In FIG. 1, reference numeral 50 denotes an electronic control unit (ECU) that electronically controls the engine 1, and the ECU 50 is configured around a microcomputer including a CPU, ROM, RAM, I / O interface, and the like. In addition, peripheral devices such as an A / D converter, a timer, a counter, and various logic circuits are provided. Various switches and sensors for detecting the operating state are connected to the input side of the ECU 50, and various auxiliary devices provided in the engine 1 are connected to the output side. Further, the ECU 50 controls a plurality of other ECUs connected to an in-vehicle network (not shown) based on a communication protocol such as CAN (Controller Area Network), for example, a transmission ECU for controlling a transmission and a brake. Various control information is input by data communication with other ECUs such as a brake ECU.

  The switches and sensors connected to the input side of the ECU 50 include an intake air amount sensor 30 that is provided immediately downstream of the air cleaner 12 in the intake passage 10 and detects the intake air amount Q, and a water temperature that detects the cooling water temperature Tw of the engine 1. A sensor 31, a suction pipe pressure sensor 32 that detects the intake manifold pressure Pm facing the air chamber 8 a, a crank angle sensor 33 that detects a crank angle, and a depression amount (accelerator opening) θacc of an accelerator pedal (not shown) An accelerator opening sensor 34 for detecting, a throttle opening sensor 35 for detecting the opening θth of the throttle valve 11, a switch for detecting an increase in load due to the operation of the auxiliary machinery, and the like are provided.

  In this embodiment, in order to detect a load change due to the operation of the compressor of the air conditioner, on the input side of the ECU 50, an air conditioner switch 36 for operating an air conditioner compressor (not shown) is turned on when the refrigerant pressure of the air conditioner is a predetermined value or more. A refrigerant pressure switch 37 is connected. The refrigerant pressure switch 37 is configured as, for example, a triple switch that is turned on at a low pressure set pressure, a high pressure set pressure, and an intermediate set pressure.

  On the other hand, auxiliary equipment connected to the output side of the ECU 50 includes the above-described injector 9, throttle actuator 20, igniter 21 for turning on and off an ignition coil (not shown) connected to the spark plug 7, and other air conditioners. Control valves, relays, and the like for controlling operations of compressors, generators, hydraulic pumps, and the like are provided.

  The ECU 50 calculates various control amounts based on signals from sensors / switches for detecting the engine operating state and various control information input via the in-vehicle network, and executes engine control.

  In this engine control, the ECU 50 calculates, for example, a throttle opening (driver required throttle opening) θthd corresponding to the accelerator pedal depression amount θacc by the driver, and the engine 1 also when the accelerator pedal depression is released. The throttle opening (basic throttle opening) θthb for securing the intake air amount (basic intake air amount) Qb necessary for the operation of is calculated. Then, the final throttle opening (target throttle opening) θtht is calculated based on the driver required throttle opening θthd and the basic throttle opening θthb.

  Here, when calculating the basic throttle opening degree θthb, the ECU 50 determines the intake air amount (ISC intake air amount) Qisc necessary for avoiding engine stall, the cooling water temperature of the engine 1 and the operating states of various auxiliary machines. And so on. Furthermore, in the case where the accelerator is off, that is, when the accelerator pedal is released, such as when the vehicle is stopped or coasted (hereinafter, this state is expressed as “the engine 1 is in a no-load state”), The ECU 50 calculates a guard intake air amount Qg necessary to maintain the intake manifold pressure Pm at a preset specified pressure (guard pressure) Pmg. Then, the ECU 50 calculates the basic intake air amount Qb necessary for the operation of the engine 1 based on the larger value of either the ISC intake air amount Qisc or the guard intake air amount Qg. As described above, in the present embodiment, the ECU 50 realizes functions as an ISC intake air amount calculation unit, a guard intake air amount calculation unit, and a basic intake air amount calculation unit. Here, as the guard pressure Pmg, for example, even when the engine pedal 1 is released and the driver requested torque T (that is, the driver requested throttle opening θthd) is zero, the engine oil is not loaded. A target value of the intake manifold pressure that needs to be compensated for in order to prevent reverse flow of the engine is set.

  Next, a target throttle opening setting routine executed by the ECU 50 will be described with reference to the flowchart shown in FIG. This routine is executed every set time. When this routine is started, the ECU 50 first, in step S101, for example, the engine speed Ne based on the crank pulse from the crank angle sensor 33 and the accelerator opening θacc. Based on the above, the driver request torque T is calculated. That is, the ECU 50 stores, for example, a three-dimensional map indicating the relationship between the engine speed Ne and the accelerator opening θacc and the driver request torque T in advance, and the ECU 50 refers to this map for the driver. The required torque T is calculated. In step S102, the ECU 50 refers to, for example, a preset table or the like, and calculates a throttle opening (driver requested throttle opening) θthd corresponding to the driver requested torque T.

  The subsequent steps S103 to S109 are processes for calculating the basic intake air amount Qb. First, in step S103, the ECU 50 calculates the ISC intake air amount Qisc. Here, the ECU 50 calculates, for example, an ISC basic intake air amount based on the cooling water temperature Tw or the like with reference to a preset table or the like, and uses this ISC basic intake air amount as a load by auxiliary equipment such as an air conditioner. The ISC intake air amount Qisc is calculated by correcting with a load correction amount for compensating the electrical load, various learning values, and the like.

  In subsequent step S104, the ECU 50 checks whether or not the engine 1 is in a no-load operation state. That is, in step S104, the ECU 50 determines that the current operating state of the engine 1 is an idle state in which the driver depresses the accelerator pedal, based on information such as the accelerator opening θacc and the own vehicle speed V input from the transmission ECU. Check if there is no load at the time or coast.

  If it is determined in step S104 that the current state of the engine 1 is in the no-load state, the ECU 50 proceeds to step S105 and calculates the guard pressure Pmg. In the present embodiment, the guard pressure Pmg is variably set according to the vehicle speed V. Specifically, for example, as shown in FIG. 3, the guard pressure Pmg is a map set in advance. Etc., a higher value is calculated as the vehicle speed V increases. As a parameter for calculating the guard pressure Pmg, for example, the engine speed Ne or the like can be used instead of the vehicle speed V.

  Then, when the process proceeds from step S105 to step S106, the ECU 50 calculates a value (pressure ratio (Pmg / Pm)) obtained by dividing the guard pressure Pmg by the intake manifold pressure Pm detected by the intake pipe pressure sensor 32, and continues. In step S107, the value obtained by multiplying the intake air amount Q detected by the intake air amount sensor 30 by the pressure ratio (Pmg / Pm) is calculated as a guard intake air amount Qg (= (Pmg / Pm) · Q). The process proceeds to step S109.

Here, generally, when the volume efficiency is μ, the engine speed is Ne, the cylinder volume is Vc, the gas constant is R, and the intake air temperature is T, the intake air amount Q and the intake manifold pressure Pm are as follows: 1) It is expressed by the relationship of the formula.
Q = ((μ · Ne · Vc) / (R · T)) · Pm (1)
In this equation (1), if α = (μ · Ne · Vc) / (R · T),
Q = α · Pm (1) ′
It becomes. Similarly, the intake air amount Q ′ after time Δt and the intake manifold pressure Pm ′ can be expressed by the relationship of the following equation (2):
Q ′ = α ′ · Pm ′ (2)
Assuming that the time Δt is very small, α can be set to α ′. Therefore, the relationship of the following equation (3) is derived from the equations (1) ′ and (2).
Q ′ = (Pm ′ / Pm) · Q (3)
In the equation (3), assuming that Pm ′ is a target value (guard pressure Pmg) to be controlled after time Δt, the intake air amount necessary for realizing the guard pressure Pmg (= Pm ′) after time Δt. Can be calculated by dividing the guard pressure Pmg by the current intake manifold pressure Pm and multiplying that value by the current intake air amount Q. In the present embodiment, based on such a technical idea, the guard intake air amount Qg is calculated based on the procedure described in steps S105 to S107.

  On the other hand, if it is determined in step S104 that the current state of the engine 1 is not a no-load state, the ECU 50 proceeds to step S108, sets the guard intake air amount Qg to “0”, and then proceeds to step S109.

  When the process proceeds from step S107 or step S108 to step S109, the ECU 50 performs the basic intake necessary (essential) for a suitable operation of the engine 1 based on the larger value of either the ISC intake air amount Qisc or the guard intake air amount Qg. The air amount Qb is calculated. In the present embodiment, specifically, the ECU 50 sets, for example, a value that is larger of either the ISC intake air amount Qisc or the guard intake air amount Qg as the basic intake air amount Qb. In step S110, the ECU 50 calculates a basic throttle opening θthb corresponding to the basic intake air amount Qb with reference to a preset table or the like.

  Then, when proceeding from step S110 to step S111, the ECU 50, for example, adds a value obtained by adding the driver requested throttle opening θthd calculated in step S102 and the basic throttle opening θthb calculated in step S110 to the final target throttle opening. After calculating the degree θtht, the routine is exited.

  According to such an embodiment, it is necessary to maintain the ISC intake air amount Qisc necessary for avoiding engine stall and the intake manifold pressure when the engine 1 is in the no-load state at a specified guard pressure Pmg or higher. By correcting the current intake air amount Q with the pressure ratio (Pmg / pm) to the correct guard intake air amount and obtaining the guard intake air amount Qg, no complicated setting work such as gain setting is required. By the simple control with good response, the appropriate guard intake air amount Q can be calculated and the pressure in the intake manifold 8 can be properly maintained. That is, the guard intake air amount Qg can be changed within a fluctuation range corresponding to the relationship between the actual intake manifold pressure Pm and the guard pressure Pmg. For example, when the intake manifold pressure Pm is significantly lower than the guard pressure Pmg. As the pressure ratio (Pmg / Pm) largely changes to the increase side, the guard intake air amount Qg can be greatly changed to the increase side. When the guard intake air amount Qg appropriately variably set is larger than the ISC intake air amount Qisc, the basic intake air amount Qb is set based on the guard intake air amount Qg. That is, particularly when the intake air density decreases due to a decrease in the external air pressure or the temperature inside the engine chamber, and the intake manifold pressure Pm falls below the guard pressure Pmg, the intake manifold pressure Pm is appropriately set. It is possible to make an early recovery to a value equal to or higher than the guard pressure Pmg by changing according to the fluctuation range.

  Here, the calculation of the guard intake air amount Qg is performed by, for example, using the previous value Qg (n−1) of the guard intake air amount as the pressure ratio instead of the calculation of correcting the intake air amount Q by the pressure ratio (Pmg / Pm). It is also possible to calculate by correcting with (Pmg / Pm).

  In such a modification, the ECU 50 executes the process of step S107 described above, for example, according to a subroutine shown in FIG. That is, when this subroutine starts, the ECU 50 first checks in step S201 whether or not the engine 1 has just shifted to a no-load state.

  If it is determined in step S201 that the engine 1 has just shifted to the no-load state, the ECU 50 proceeds to step S202, sets the current ISC intake air amount Qisc as the guard intake air amount Qg, and then executes a subroutine. Exit.

  On the other hand, if it is determined in step S201 that the engine 1 is not immediately after the transition to the no-load state, the ECU 50 proceeds to step S203, and the pressure ratio (Pmg / Pm) is added to the previous value Qg (n-1) of the guard intake air amount. ) Is set as a new guard intake air amount Qg, and the subroutine is exited.

  Even in such a modification, it is possible to achieve substantially the same effect as in the above-described embodiment. In this case, in particular, it is possible to use a predetermined intake air amount set in advance as the guard intake air amount Qg immediately after the transition to the no-load state, but by using the ISC intake air amount Qisc, As the initial value of the intake air amount Qg, a value according to the actual operating state of the engine 1 can be set.

  In the above-described embodiment, an example in which the present invention is applied to control of an electronically controlled throttle valve has been described. However, the present invention is not limited to this. For example, in an engine or the like in which an accelerator pedal and a throttle valve are mechanically connected by a cable or the like, the basic intake air described above is used as a parameter for controlling the opening degree of a bypass passage that bypasses the throttle valve through an ISC valve or the like. It is also possible to apply the quantity Qb.

Configuration diagram of engine control system Flow chart showing target throttle opening calculation routine Chart showing guard pressure calculation table Flowchart showing a subroutine of a modified example of the guard intake air amount calculation

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine 1a ... Combustion chamber 2 ... Cylinder head 3 ... Intake port 4 ... Exhaust port 5 ... Intake valve 6 ... Exhaust valve 7 ... Spark plug 8 ... Intake manifold 8a ... Air chamber 9 ... Injector 10 ... Intake passage 11 ... Throttle valve DESCRIPTION OF SYMBOLS 12 ... Air cleaner 13 ... Exhaust manifold 14 ... Exhaust passage 15 ... Catalyst 20 ... Throttle actuator 21 ... Igniter 30 ... Intake air amount sensor 31 ... Water temperature sensor 32 ... Intake pipe pressure sensor 33 ... Crank angle sensor 34 ... Accelerator opening sensor 35 ... Throttle opening sensor 36 ... Air conditioner switch 37 ... Refrigerant pressure switch 50 ... Electronic control device (ISC intake air amount calculating means, guard intake air amount calculating means, basic intake air amount calculating means)
Ne ... Engine speed Pm ... Intake manifold pressure Pmg ... Guard pressure Q ... Intake air quantity Qb ... Basic intake air quantity Qg ... Guard intake air quantity Qisc ... ISC intake air quantity T ... Driver required torque Tw ... Cooling water temperature V ... Vehicle speed θacc … Accelerator opening θthb… basic throttle opening θthd… driver requested throttle opening θtht… target throttle opening

Claims (3)

ISC intake air amount calculating means for calculating an ISC intake air amount necessary for avoiding engine stall;
A guard intake air amount calculating means for calculating a guard intake air amount necessary to maintain the intake manifold pressure when the accelerator is in an off state above a predetermined guard pressure set in advance;
Basic intake air amount calculation means for calculating a basic intake air amount necessary for engine operation based on a value that is larger of either the ISC intake air amount or the guard intake air amount;
The guard intake air amount calculation means sets, as the guard intake air amount, a value obtained by dividing the guard pressure by the intake manifold pressure detected by the sensor and the intake air amount of the engine detected by the sensor. An engine control device. ISC intake air amount calculation means for calculating an ISC intake air amount necessary for avoiding engine stall;
A guard intake air amount calculating means for calculating a guard intake air amount necessary to maintain the intake manifold pressure when the accelerator is in an off state above a predetermined guard pressure set in advance;
Basic intake air amount calculation means for calculating a basic intake air amount necessary for engine operation based on a value that is larger of either the ISC intake air amount or the guard intake air amount;
The guard intake air amount calculation means sets a multiplication value of a value obtained by dividing the guard pressure by an intake manifold pressure detected by a sensor and a previous value of the guard intake air amount as the current guard intake air amount. An engine control device. 3. The engine control device according to claim 2, wherein the guard intake air amount calculation means sets the ISC intake air amount as the guard intake air amount immediately after shifting to the accelerator off state.

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