JP2012172614A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine, obtaining a fuel economy improving effect by fuel cut operation and surely avoiding an engine stop by properly setting a fuel supply restarting rotation speed when an air conditioning device is turned on during fuel cut operation.SOLUTION: When an air conditioner clutch 31 is engaged during fuel cut operation and a compressor 32 is shifted from a non-operating state to an operating state, until a stabilization period TSTBL required for stabilization of refrigerant pressure elapses from the time point of clutch engagement, the fuel supply restarting rotation speed NFCE is set according to the alternative value (TDCTA) showing a load which is put on an engine 1 by the operation of the compressor 32, and after elapse of the stabilization period TSTBL, the fuel supply restarting rotation speed NFCE is set according to the refrigerant pressure correlation estimating torque TDCP calculated according to air conditioner refrigerant pressure.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device that performs a fuel cut operation during engine deceleration.

  Patent Document 1 discloses a control device that performs a fuel cut operation during engine deceleration. According to this control device, the refrigerant pressure on the downstream side of the compressor of the air conditioner driven by the engine is detected, and when the air conditioner is turned on during the fuel cut operation, the fuel supply is performed according to the detected refrigerant pressure. The engine speed to restart (fuel supply restart speed) is set. Considering that the driving load of the air conditioner is applied to the engine, the fuel supply resumption rotational speed is set higher than when the air conditioner is off, and the engine stop is avoided.

JP 2003-336531 A

  When the air conditioner is turned on, the clutch that transmits the engine driving force to the compressor is engaged, and the refrigerant pressure is increased. However, since there is a delay until the refrigerant pressure becomes stable, the refrigerant pressure detected by the refrigerant pressure sensor does not accurately indicate the load applied to the engine immediately after the air conditioner starts operation. Therefore, if the fuel supply restart speed is set according to the detected refrigerant pressure, the restart of fuel supply is delayed and the engine may stop before restarting.

  The present invention has been made paying attention to this point, and when the compressor of the air conditioner starts operating during the fuel cut operation, the fuel supply restart speed is appropriately set to obtain the fuel efficiency improvement effect by the fuel cut operation. In addition, an object of the present invention is to provide a control device for an internal combustion engine that can reliably avoid engine stoppage.

  In order to achieve the above object, the invention according to claim 1 executes a fuel cut operation for stopping fuel supply to the engine when the internal combustion engine decelerates, and the engine speed (NE) is the fuel supply restart speed. (NFCE) In an internal combustion engine control device comprising a fuel cut control means for ending the fuel cut operation and restarting fuel supply when the pressure is reduced to (NFCE), the compressor (32,) of the air conditioning means (23) driven by the engine 32a) an operating state detecting means for detecting the operating state, a refrigerant pressure correlation value calculating means for calculating a refrigerant pressure correlation value (TDCP) correlated with the refrigerant pressure (Pd) of the air conditioning means, and the refrigerant pressure correlation value ( Fuel supply restart speed setting means for setting the fuel supply restart speed (NFCE) according to TDCP), and the fuel supply restart speed setting means is configured to perform the fuel cut operation. When the compressor (32, 32a) shifts from the non-operating state to the operating state, the refrigerant pressure correlation value (TDCP) is replaced with the substitute value (TDCTA) until the stable period (TSTBL) elapses from the transition point. And the fuel supply restart speed (NFCE) is set, and the stable period (TSTBL) is set as a period from the transition time until the refrigerant pressure (Pd) is stabilized.

  According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect of the present invention, the control apparatus for the internal combustion engine further includes an outside air temperature correlation temperature acquisition unit that acquires an outside air temperature correlation temperature (TA) correlated with the outside air temperature, (TSTBL) is set according to the outside air temperature correlation temperature (TA).

  The invention according to claim 3 is the control apparatus for an internal combustion engine according to claim 2, further comprising refrigerant pressure acquisition means for acquiring the refrigerant pressure (Pd) of the air conditioning means, wherein the stable period (TSTBL) is: It is set longer as the outside air temperature correlation temperature (TA) is higher, and is set longer as the refrigerant pressure (Pd) immediately after the start of the compressor operation is lower.

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to the second aspect, the substitute value (TDCTA) is set to increase as the outside air temperature correlation temperature (TA) increases. Features.

  According to a fifth aspect of the present invention, in the control apparatus for an internal combustion engine according to the fourth aspect, during the stable period, a difference between the refrigerant pressure correlation value (TDCP) and the alternative value (TDCTA) is a predetermined value (DTDX). ) It is a period until it becomes smaller.

  According to a sixth aspect of the present invention, in the control device for an internal combustion engine according to the third aspect, the refrigerant pressure correlation value (TDCP) is estimated based on the refrigerant pressure (Pd). It is characterized by being.

  The invention according to claim 7 is the control apparatus for an internal combustion engine according to claim 4 or 5, further comprising refrigerant pressure acquisition means for acquiring the refrigerant pressure (Pd) of the air conditioning means, wherein the refrigerant pressure correlation value ( TDCP) is a driving torque of the compressor estimated based on the refrigerant pressure (Pd).

  The invention according to claim 8 is the control apparatus for an internal combustion engine according to claim 6 or 7, wherein the compressor is a fixed displacement compressor (32), and the refrigerant pressure acquisition means is the air conditioning means. A low-pressure side refrigerant pressure (Ps), a low-pressure side refrigerant pressure acquisition means for acquiring a low-pressure side refrigerant pressure (Ps) upstream of the compressor, and a low-pressure side refrigerant pressure (Ps). The difference (DEN) between the enthalpy (EPs) of the refrigerant on the upstream side of the compressor calculated on the basis of the pressure and the enthalpy (EPd) of the refrigerant on the downstream side of the compressor calculated on the basis of the high-pressure side refrigerant pressure (Pd). ) For calculating the enthalpy difference, the engine speed detecting means for detecting the engine speed (NE), and the refrigerant based on the engine speed (NE). A refrigerant flow rate calculating means for calculating an amount (Gr), wherein the refrigerant pressure correlation value calculating means is based on the enthalpy difference (DEN), the engine speed (NE), and the refrigerant flow rate (Gr). The driving torque (TDCP) of the compressor is estimated.

  According to a ninth aspect of the present invention, in the control device for an internal combustion engine according to the sixth or seventh aspect, the compressor is a variable displacement compressor (32a), and the refrigerant pressure acquisition means is provided downstream of the compressor. A first high-pressure side refrigerant pressure detection means for detecting a first high-pressure side refrigerant pressure (Pda) that is an upstream refrigerant pressure of a condenser (33) provided on the side, and a first refrigerant pressure that is a downstream refrigerant pressure of the condenser (33). 2 low pressure side refrigerant pressure acquisition means for acquiring low pressure side refrigerant pressure (Ps) upstream of the compressor, and low pressure side refrigerant pressure detection means for detecting high pressure side refrigerant pressure (Pd) The enthalpy (EPs) of the refrigerant on the upstream side of the compressor calculated based on the refrigerant pressure (Ps) and the co-calculated based on the first or second high-pressure side refrigerant pressure (Pda, Pd). An enthalpy difference calculating means for calculating a difference (DEN) from the refrigerant enthalpy (EPd) on the downstream side of the presser, a rotational speed detecting means for detecting the rotational speed (NE) of the engine, and the first high-pressure side refrigerant pressure ( A refrigerant flow rate calculating means for calculating a flow rate (Gr) of the refrigerant in accordance with a differential pressure (DPH) between Pda) and the second high-pressure side refrigerant pressure (Pd), wherein the refrigerant pressure correlation value calculating means comprises: The compressor driving torque (TDCP) is estimated based on the enthalpy difference (DEN), the engine speed (NE), and the refrigerant flow rate (Gr).

  According to the first aspect of the present invention, when the compressor of the air-conditioning means shifts from the non-operating state to the operating state during the fuel cut operation, the stable period required for stabilizing the refrigerant pressure elapses from the transition point. The fuel supply restart speed is set by switching the refrigerant pressure correlation value to an alternative value. The fuel supply restart speed is set according to the refrigerant pressure correlation value. Therefore, by setting the alternative value to a value corresponding to the load applied to the engine by starting the operation of the compressor, in the transient state immediately after the compressor of the air conditioning means shifts from the non-operating state to the operating state, the fuel supply restarting rotational speed is set. It can be set appropriately. As a result, it is possible to obtain the fuel efficiency improvement effect by the fuel cut operation and to reliably avoid the engine stop.

  According to the second aspect of the invention, the outside air temperature correlation temperature correlated with the outside air temperature is acquired, and the stable period is set according to the outside air temperature correlation temperature. The period until the refrigerant pressure of the air-conditioning means stabilizes changes depending on the outside air temperature, so by setting it according to the outside air temperature correlation temperature, set the stabilization period appropriately and enhance the fuel efficiency improvement effect Can do.

  According to the third aspect of the present invention, the refrigerant pressure is acquired, and the stable period is set longer as the outside air temperature correlation temperature becomes higher, and is set longer as the refrigerant pressure immediately after the start of the compressor operation is lower. The higher the outside air temperature and the lower the refrigerant pressure immediately after the start of compressor operation, the longer the time until the refrigerant pressure stabilizes.Therefore, the longer the stable period is set, the higher the outside air temperature correlation temperature becomes. By setting the length longer as the engine speed decreases, it is possible to appropriately set the stable period, enhance the fuel efficiency improvement effect, and reliably avoid the engine stop.

  According to the invention described in claim 4, the substitute value is set so as to increase as the outside air temperature correlation temperature increases. The engine load applied when the compressor of the air-conditioning means starts operating increases as the outside air temperature increases, so by calculating so as to increase as the outside air temperature correlation temperature increases, the fuel supply restart speed in the transient state is calculated. Appropriately set, it is possible to enhance the fuel efficiency improvement effect and reliably avoid the engine stop.

  According to the invention described in claim 5, the stable period is a period until the difference between the refrigerant pressure correlation value and the alternative value becomes smaller than a predetermined value. Since the refrigerant correlation value correlates with the refrigerant pressure, and the refrigerant pressure correlates with the load applied to the engine, it is determined that the refrigerant pressure has stabilized when the difference between the refrigerant pressure correlation value and the alternative value becomes smaller than a predetermined value. By doing so, a stable period can be set more appropriately.

  According to the invention described in claim 6 or 7, the refrigerant pressure correlation value is the compressor driving torque estimated based on the refrigerant pressure. Since the compressor driving torque correlates with the refrigerant pressure and directly indicates the load applied to the engine, the fuel supply resumption rotational speed can be appropriately set by using this.

  According to the invention described in claim 8, the compressor of the air-conditioning means is a fixed displacement type compressor, the high-pressure side refrigerant pressure on the downstream side of the compressor and the low-pressure side refrigerant pressure on the upstream side of the compressor are acquired, and the low-pressure side refrigerant is obtained. A difference between the enthalpy of the refrigerant on the upstream side of the compressor calculated based on the pressure and the enthalpy of the refrigerant on the downstream side of the compressor calculated based on the high-pressure side refrigerant pressure is calculated. Further, the flow rate of the refrigerant is calculated based on the detected engine speed, and the compressor driving torque is estimated based on the enthalpy difference, the detected engine speed, and the refrigerant flow rate. The compressor driving torque is proportional to the enthalpy difference and the refrigerant flow rate, and is inversely proportional to the compressor speed, that is, the engine speed. Therefore, according to the configuration of claim 8, these parameter values are accurately calculated, and the compressor driving torque is accurately calculated. Can be estimated. In the fixed displacement compressor, the refrigerant flow rate can be accurately calculated according to the differential pressure between the high-pressure side refrigerant pressure and the low-pressure side refrigerant pressure.

  According to the ninth aspect of the present invention, the compressor of the air conditioning means is a variable displacement compressor, the first high-pressure side refrigerant pressure that is the refrigerant pressure upstream of the condenser provided on the downstream side of the compressor, and the condenser downstream side. A second high-pressure side refrigerant pressure that is a side refrigerant pressure is detected, a low-pressure side refrigerant pressure upstream of the compressor is acquired, and the refrigerant enthalpy on the compressor upstream side calculated based on the low-pressure side refrigerant pressure A difference from the refrigerant enthalpy on the downstream side of the compressor calculated based on the first or second high-pressure side refrigerant pressure is calculated. Further, the flow rate of the refrigerant is calculated according to the differential pressure between the first high pressure side refrigerant pressure and the second high pressure side refrigerant pressure, and the driving torque of the compressor is estimated based on the enthalpy difference, the engine speed, and the refrigerant flow rate. Thus, the compressor driving torque can be estimated with high accuracy in the same manner as in the eighth aspect of the invention. In the variable capacity compressor, the refrigerant flow rate can be accurately calculated according to the differential pressure between the first high-pressure side refrigerant pressure on the upstream side of the condenser and the second high-pressure side refrigerant pressure on the downstream side of the condenser.

It is a figure which shows the structure of the internal combustion engine concerning one Embodiment of this invention, the air conditioner driven by this engine, and those control apparatuses. It is a figure which shows the structure of the refrigerant | coolant circulation system of the air conditioner shown by FIG. It is a figure which shows the relationship between the refrigerant | coolant pressure (PCM) in a refrigerant | coolant circulation system, and the enthalpy (EN) of a refrigerant | coolant. It is a flowchart of the process which performs control of the fuel cut driving | operation which stops the fuel supply to an engine. It is a flowchart of the process which calculates the compressor drive torque (TDCP) of an air conditioner. It is a figure which shows the map and table referred by the process of FIG. It is a figure for demonstrating the calculation method of enthalpy (EN). It is a time chart for demonstrating the control action by the process of FIG. It is a flowchart of the modification of the process shown in FIG. It is a figure which shows the structure of the refrigerant circulation system in the 2nd Embodiment of this invention. It is a flowchart of the process which calculates the compressor drive torque (TDCP) of an air conditioner (2nd Embodiment). It is a figure which shows the table referred by the process of FIG. It is a figure which shows the table used in the modification of 1st and 2nd embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of an internal combustion engine according to an embodiment of the present invention, an air conditioner driven by the engine, and their control devices. A throttle valve 3 is arranged in the middle of an intake pipe 2 of an internal combustion engine (hereinafter simply referred to as “engine”) 1. The throttle valve 3 is provided with a throttle valve opening sensor 4 for detecting the opening TH of the throttle valve 3, and the detection signal is supplied to an engine control electronic control unit (hereinafter referred to as “EG-ECU”) 5. Is done. An actuator 7 that drives the throttle valve 3 is connected to the throttle valve 3, and the operation of the actuator 7 is controlled by the EG-ECU 5.

  A fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown). Each injection valve is connected to a fuel pump (not shown) and is electrically connected to the EG-ECU 5 so that the EG- The valve opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5. The ignition plug 13 of each cylinder is connected to the EG-ECU 5, and an ignition signal is supplied from the EG-ECU 5.

  An intake air amount sensor 14 for detecting an intake air amount GAIR [g / sec] is mounted on the upstream side of the throttle valve 3 of the intake pipe 2, and a cooling water temperature sensor 9 for detecting the engine cooling water temperature TW is installed in the main body of the engine 1. The detection signals of these sensors are supplied to the EG-ECU 5.

  A crank angle position sensor 10 that detects the rotation angle of the crankshaft 8 of the engine 1 is connected to the EG-ECU 5, and a signal corresponding to the rotation angle of the crankshaft is supplied to the EG-ECU 5. The crank angle position sensor 10 is a cylinder discrimination sensor that outputs a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and relates to a top dead center (TDC) at the start of the intake stroke of each cylinder. It consists of a TDC sensor that outputs a TDC pulse at a crank angle position before a predetermined crank angle, and a CRK sensor that generates a CRK pulse at a constant crank angle cycle shorter than the TDC pulse (for example, a cycle of 6 degrees), and includes a CYL pulse, a TDC pulse and a CRK pulse. Is supplied to the EG-ECU 5. These signal pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE.

  The EG-ECU 5 includes an outside air temperature sensor 11 that detects an outside air temperature TA, an accelerator sensor 12 that detects an amount of depression of an accelerator pedal of a vehicle driven by the engine 1 (hereinafter referred to as “accelerator pedal operation amount”), and an engine. A vehicle speed sensor 13 for detecting the vehicle speed VP of the vehicle driven by 1 is connected, and detection signals from these sensors are supplied to the EG-ECU 5.

  The crankshaft 8 is connected to an automatic transmission (not shown) having a lock-up clutch, and the driving force of the engine 1 is transmitted to the driving wheels of the vehicle via the automatic transmission and other power transmission mechanisms. .

  The EG-ECU 5 shapes an input signal waveform from various sensors, corrects a voltage level to a predetermined level, and converts an analog signal value into a digital signal value. CPU ”), a storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, and an output circuit that supplies a drive signal to the actuator 7, the fuel injection valve 6, the spark plug 13, and the like.

  The EG-ECU 5 performs valve opening time control (fuel supply control) and ignition timing control based on the sensor detection signal described above, and calculates the target opening THCMD of the throttle valve 3, Throttle valve opening control for driving the actuator 7 is performed so that the detected throttle valve opening TH coincides with the target opening THCMD.

  The crankshaft 8 of the engine 1 is connected to an air conditioner (hereinafter referred to as “air conditioner”) 23 via a transmission mechanism 21 and a shaft 22, and a compressor 32 of the air conditioner 23 is driven by the shaft 22 via an air conditioner clutch 31. It is configured to be able to. The operation of the air conditioner 23 is controlled by an air conditioner control electronic control unit (hereinafter referred to as “AC-ECU”) 20.

  The AC-ECU 20 is connected to an on / off switch, a temperature setting switch (not shown), and the like, and switching signals of these switches are supplied to the AC-ECU 20. Similar to the EG-ECU 5, the AC-ECU 20 includes an input circuit, a CPU, a storage circuit, and an output circuit. AC-ECU 20 is connected to EG-ECU 5 and transmits necessary information to each other. A signal indicating the detected outside air temperature TA is supplied from the EG-ECU 5 to the AC-ECU 20, while a signal indicating a refrigerant pressure, which will be described later, is supplied from the AC-ECU 20 to the EG-ECU 5.

  The AC-ECU 20 controls the air conditioner 23 based on the outside air temperature TA, the room temperature, the set temperature, and the like.

  FIG. 2 is a diagram showing the configuration of the refrigerant circulation system of the air conditioner 23. The refrigerant circulation system includes a compressor 32, a condenser 33, an evaporator 34, and first, second, and third refrigerants that connect them. Passages 36, 37, and 38 and an expansion valve 39 provided in the third refrigerant passage 38 are provided. In the present embodiment, the compressor 32 is a fixed displacement compressor.

  The evaporator 34 is provided with a surface temperature sensor 41 that detects the surface temperature TSRF of the evaporator 34. The first refrigerant passage 36 is provided with a first refrigerant pressure sensor 42 that detects refrigerant pressure Ps upstream of the compressor 32 (hereinafter referred to as “low-pressure side refrigerant pressure”) Ps, and the third refrigerant passage 38 has an expansion valve. A second refrigerant pressure sensor 43 that detects refrigerant pressure Pd upstream of 39 (hereinafter referred to as “high pressure refrigerant pressure”) Pd is provided. The detection signals of these sensors 41 to 43 are supplied to the AC-ECU 20.

  FIG. 3 shows a simplified Mollier diagram for explaining the operation of the refrigerant circulation system shown in FIG. The horizontal axis of FIG. 3 is enthalpy EN [kJ / kg], and the vertical axis is the refrigerant pressure PCM [MPa]. Also, curves L1 and L2 shown in FIG. 3 are a saturated vapor line and a saturated liquid line, respectively, and state points PC1, PC2, and PC3 are a first refrigerant path 36, a second refrigerant path 37, and a third line, respectively. The state of the refrigerant in the refrigerant passage (upstream side of the expansion valve 39) is shown. On the right side of the saturated vapor line L1, the refrigerant is a gas, and on the left side of the saturated liquid line L2, the refrigerant is a liquid.

  By being compressed by the compressor 32, both the enthalpy EN and the pressure PCM of the refrigerant increase, and the state point PC1 is shifted to PC2. In the condenser 33, the refrigerant is liquefied, the enthalpy EN is greatly reduced, the refrigerant pressure PCM is slightly reduced, and the state point PC2 is shifted to PC3. The refrigerant pressure PCM rapidly decreases at the expansion valve 39, the enthalpy EN increases at the evaporator 34, and returns from the state point PC3 to PC1.

  As will be described later, the estimated drive torque TDCP, which is an estimated value of the drive torque of the compressor 32 (load torque applied to the engine 1), is calculated by using the low pressure enthalpy EPs at the state point PC1 and the high pressure enthalpy EPd at the state point PC2. The enthalpy difference DEN (= EPd−EPs) is applied.

  FIG. 4 is a flowchart of a process for controlling the fuel cut operation for temporarily stopping the fuel supply to the engine 1 when the engine 1 is decelerated. This process is executed by the CPU of the EG-ECU 5.

  In step S11, it is determined whether or not an accelerator pedal off flag FAPOFF is “1”. The accelerator pedal off flag FAPOFF is set to “1” when the accelerator pedal is not depressed (when the accelerator pedal operation amount AP is “0”). If the answer to step S11 is affirmative (YES), it is determined whether or not the engine speed NE is equal to or less than a fuel cut start speed NFCS (step S12). When the answer is affirmative (YES), it is further determined whether or not the lockup clutch engagement flag FLCON is “1”. The lockup clutch engagement flag FLCON is set to “1” when the lockup clutch of the automatic transmission is in an engaged state.

  When the answer to any of steps S11 to S13 is negative (NO), it is determined that the fuel cut operation execution condition is not satisfied, the fuel cut flag FFC is set to “0” (step S14), and this process is performed. finish.

  If the answer to step S13 is affirmative (YES), it is determined that the fuel cut operation execution condition is satisfied, and it is determined whether or not the fuel cut flag FFC is “1” (step S15). Initially, this answer is negative (NO), so the fuel cut flag FFC is set to “1” (step S16). Thereafter, since the answer to step S15 is affirmative (YES), the process immediately proceeds to step S17.

  In step S17, it is determined whether or not the air conditioner ON flag FACON is “1”. The air conditioner ON flag FACON is set to “1” when the air conditioner 23 is in an operating state. If the answer to step S17 is negative (NO), the engine speed at which the fuel cut operation is terminated, that is, the fuel supply restart speed NFCE, which is the engine speed at which fuel supply is restarted, is set to the minimum restart speed NFCEMIN. (Step S18), the process proceeds to Step S30.

  If the answer to step S17 is affirmative (YES), that is, if the air conditioner is operating, it is determined whether or not a sensor failure flag FSFAIL is “1” (step S19). The sensor failure flag FSFAIL is set to “1” when a failure of any of the various sensors provided in the air conditioner 23 is detected. If the answer to step S19 is affirmative (YES), the fuel supply restart speed NFCE is set to the maximum restart speed NFFCEMAX (step S20), and the process proceeds to step S30.

  If the answer to step S19 is negative (NO), it is determined whether or not an air conditioner clutch on change flag FCLONCNG is “1” (step S21). The air conditioner clutch on change flag FCLONCNG is set to “1” only immediately after the air conditioner clutch 31 shifts from the non-engaged state to the engaged state. If the answer to step S21 is affirmative (YES) and immediately after the air conditioner clutch 31 is engaged, the TSTBL map shown in FIG. 6A is searched according to the outside air temperature TA and the high-pressure side refrigerant pressure Pd. Then, the stable period TSTBL is calculated (step S22). The stable period TSTBL is set according to the outside air temperature TA and the high-pressure side refrigerant pressure Pd as a period required from when the air conditioner clutch 31 is engaged until the refrigerant pressure is stabilized. P1 to P3 shown in FIG. 6A are predetermined refrigerant pressures and satisfy the relationship P1 <P2 <P3. The TSTBL map is set such that the higher the outside temperature TA, the longer the stable period TSTBL, and the lower the high-pressure side refrigerant pressure Pd, the longer the stable period TSTBL.

  In step S23, the downcount timer TMSTBL is set to the stable period TSTBL and started. In step S25, the TDCTA table shown in FIG. 6B is searched according to the outside air temperature TA, and the outside air temperature correlation estimated torque TDCTA is calculated. The outside air temperature correlation estimated torque TDCTA is an estimated value of compressor driving torque (torque serving as a load on the engine 1) generated when the air conditioner clutch 31 is engaged. The outside air temperature correlation estimated torque TDCTA is an estimated torque that is estimated according to the outside air temperature TA and is not affected by a delay in change in the high-pressure side refrigerant pressure Pd. The TDCTA table is set so that the outside air temperature correlation estimated torque TDCTA increases as the outside air temperature TA increases. In step S26, the compressor drive torque TDCMP is set to the outside air temperature correlation estimated torque TDCTA, and the process proceeds to step S29.

  Only after the air-conditioner clutch 31 is engaged, the answer to step S21 is affirmative (YES), but after that the answer to step S21 is negative (NO), the process proceeds to step S24, and the value of the timer TMSTBL is “0”. It is determined whether or not. Since this answer is negative (NO) at first, the process proceeds to step S25.

  When the stable period TSTBL elapses from the time when the air conditioner clutch 31 is engaged, the answer to step S24 is affirmative (YES), the process proceeds to step S27, the TDCP calculation process shown in FIG. 5 is executed, and the refrigerant pressure correlation estimated torque TDCP is calculated. calculate. The refrigerant pressure correlation estimated torque TDCP is an estimated value of the compressor driving torque calculated based on the detected refrigerant pressures Ps and Pd. The refrigerant pressure correlation estimated torque TDCP shows an accurate estimated torque because the influence of the refrigerant pressure change delay disappears after the stable period TSTBL elapses. In step S28, the compressor driving torque TDCMP is set to the refrigerant pressure correlation estimated torque TDCP.

  In step S29, the NFCE table shown in FIG. 6C is searched according to the compressor driving torque TDCMP, and the fuel supply restart speed NFCE is calculated. The NFCE table is set so that the fuel supply restart speed NFCE increases as the compressor drive torque TDCMP increases. The fuel supply restart speed NFCE calculated in step S29 is not less than the minimum restart speed NFCEMIN and not more than the maximum restart speed NFCEMAX.

  In step S30, it is determined whether or not the engine speed NE is equal to or less than the fuel supply restart speed NFCE, and the process is immediately terminated while the answer is negative (NO). Therefore, the fuel cut operation is continued. If the answer to step S30 is affirmative (YES), the fuel cut flag FFC is returned to “0”, and fuel supply is resumed (fuel cut operation ends).

FIG. 5 is a flowchart of the TDCP calculation process executed in step S27 of FIG.
In step S41, the low pressure side enthalpy EPs is calculated according to the low pressure side refrigerant pressure Ps. Specifically, the low pressure side enthalpy EPs is calculated as follows using the enthalpy calculation map in which the saturated vapor line L1 and the isothermal line (indicated by a thin broken line) in the Mollier diagram shown in FIG. 7 are mapped. In FIG. 7, TCM1 to TCM6 are predetermined refrigerant temperatures and satisfy the relationship of TCM1 <TCM2 <TCM3 <TCM4 <TCM5 <TCM6.

1) The state point PCS1 on the saturated vapor line L1 corresponding to the low-pressure side refrigerant pressure Ps is obtained.
2) The first low-pressure refrigerant temperature TCMS1 corresponding to the state point PCS1 is calculated by performing an interpolation operation of the refrigerant temperatures (TCM1, TCM2) corresponding to the isothermal lines.
3) The second low-pressure refrigerant temperature TCMS2 (= TCMS1 + TADDS) is calculated by adding the predetermined low-pressure side addition temperature TADDS to the first low-pressure refrigerant temperature TCMS1.
4) The state point PCS2 corresponding to the low-pressure side refrigerant pressure Ps and the second low-pressure refrigerant temperature TCMS2 is obtained. The enthalpy corresponding to the state point PCS2 corresponds to the low pressure side enthalpy EPs.

  The predetermined low-pressure side additional temperature TADDDS is set in advance to a value in the range of, for example, about 0 to 20 degrees in consideration of heat received from the engine 1, and depends on the positional relationship between the air conditioner 23 and the engine 1.

  In step S42, the high pressure side enthalpy EPd is calculated according to the high pressure side refrigerant pressure Pd. The calculation method is the same as that of the low-pressure enthalpy EPs. That is, the state point PCD1 shown in FIG. 7 is obtained according to the high-pressure side refrigerant pressure Pd, the first high-pressure refrigerant temperature TCMD1 corresponding to the state point PCD1 is calculated, and the predetermined high-pressure side added temperature TADDD is added to the first high-pressure refrigerant temperature TCMD1. Addition is performed to calculate the second high-pressure refrigerant temperature TCMD2 (= TCMD1 + TADDD), the state point PCD2 corresponding to the second high-pressure refrigerant temperature TCMD2 is obtained, and the high-pressure side enthalpy EPd is calculated. The predetermined high-pressure side additional temperature TADDD is a parameter that depends on the operating characteristics of the compressor 32, and is set, for example, within a range of about 20 to 50 degrees.

In step S43, the enthalpy difference DEN and the pressure difference DP are calculated by the following formulas (1) and (2).
DEN = EPd-EPs (1)
DP = Pd−Ps (2)

  In step S44, a refrigerant flow rate Gr is calculated by searching a map (not shown) corresponding to the engine speed NE and the pressure difference DP. The refrigerant flow rate Gr is calculated so as to increase as the engine speed NE increases and to increase as the pressure difference DP increases.

In step S45, the compressor rotational speed NC is calculated by the following equation (3). KC in equation (3) is a conversion coefficient corresponding to the transmission ratio of the transmission mechanism 21.
NC = NE × KC (3)

In step S46, the enthalpy difference DEN, the compressor rotational speed NC, and the refrigerant flow rate Gr are applied to the following equation (4) to calculate the refrigerant pressure correlation estimated torque TDCP. Ηm in equation (4) is the mechanical efficiency (constant) of the compressor 32.
TDCP = DEN × Gr × ηm / NC (4)

  With the processing in FIG. 5, it is possible to calculate the refrigerant pressure correlation estimated torque TDCP that accurately approximates the compressor driving torque in the steady state.

  FIG. 8 is a time chart for explaining the fuel cut control in the present embodiment, and shows an example in which the air conditioner clutch 31 is engaged at time t0. FIG. 8A shows changes in the high-pressure side refrigerant pressure Pd (broken line), refrigerant pressure correlation estimated torque TDCP, and outside air temperature correlation estimated torque TDCTA, and FIG. 8B shows changes in the engine speed NE. . The one-dot chain line shown in FIG. 8A shows the actual compressor driving torque TDCACT for reference.

  The broken line shown in FIG. 8B indicates that the fuel supply restart speed NFCE is set to the first restart speed NFCE1 calculated according to the refrigerant pressure correlation estimated torque TDCP (or the refrigerant pressure Pd itself), and at time t2. The transition of the engine speed NE when the fuel supply is resumed is shown. In this case, the engine supply stall occurs because the fuel supply restart time is too late. Note that NECEA in FIG. 8B indicates the fuel supply restart speed set according to the actual compressor drive torque TDCACT. In this case, the fuel supply is restarted at time t1.

  In the present embodiment, the outside air temperature correlation estimated torque TDCTA is calculated at time t0, and the outside air temperature correlation estimated torque TDCTA takes an approximate value of the steady value of the actual compressor driving torque TDCACT (the value after the stable period TSTBL has elapsed from time t0). The fuel supply restart speed NFCE is set to the second restart speed NFCE2 in accordance with the outside air temperature correlation estimated torque TDCTA. Thereby, fuel supply is restarted at time t1a slightly before time t1, and engine stall can be avoided.

  As described above, in the present embodiment, when the refrigerant pressure correlation estimated torque TDCP is calculated as the refrigerant pressure correlation value correlated with the refrigerant pressure of the air conditioner 23 and the refrigerant pressure is stable (for example, a state where the compressor is operating) In the case where the fuel cut operation is started), the fuel supply restart speed NFCE is set according to the refrigerant pressure correlation estimated torque TDCP. When the air conditioner clutch 31 is engaged during the fuel cut operation and the compressor 32 shifts from the non-operating state to the operating state, the outside air temperature correlation estimation torque is used as an alternative value correlated with the load applied to the engine 1 by the operation of the compressor 32. TDCTA is calculated and fuel supply is resumed using the outside air temperature correlation estimated torque TDCTA instead of the refrigerant pressure correlation estimated torque TDCP until the stable period TSTBL required for the refrigerant pressure stabilization elapses after the compressor operation start time (t0). The rotational speed NFCE is set. Therefore, in the transient state immediately after the compressor 32 shifts from the non-operating state to the operating state, the fuel supply restart speed NFCE is set according to the outside air temperature correlation estimated torque TDCTA, and the fuel supply restart speed NFCE is set appropriately. be able to. As a result, the fuel efficiency improvement effect by the fuel cut operation can be obtained, and the engine stall can be surely avoided.

  Further, the stable period TSTBL is set longer as the outside air temperature TA becomes higher, and is set longer as the high-pressure side refrigerant pressure Pd immediately after the start of the compressor operation is lower. The longer the outside temperature TA is, and the lower the high-pressure side refrigerant pressure Pd immediately after the start of compressor operation is, the longer the time until the refrigerant pressure Pd is stabilized. Therefore, the stabilization period TSTBL is set longer as the outside temperature TA becomes higher. In addition, by setting the longer the high-pressure side refrigerant pressure Pd immediately after the start of the compressor operation, the longer the stable period TSTBL is set to the optimum value, the fuel efficiency improvement effect can be enhanced and the engine stall can be avoided reliably.

  The outside air temperature correlation estimated torque TDCP is calculated so as to increase as the outside air temperature TA increases. Since the engine load applied when the compressor 32 starts operation increases as the outside air temperature TA increases, the outside air temperature correlation estimated torque TDCP is calculated so as to increase as the outside air temperature TA increases. It is possible to appropriately set the fuel supply restart speed NFCE to increase the fuel efficiency improvement effect and to reliably avoid engine stall.

  In the present embodiment, the air conditioner 23 corresponds to air conditioning means, the crank angle position sensor 10 corresponds to rotation speed detection means, the second refrigerant pressure sensor 43 corresponds to refrigerant pressure acquisition means, and the first refrigerant pressure sensor 42 corresponds to The outside air temperature sensor 11 is equivalent to the outside air temperature correlation temperature obtaining means, and the EG-ECU 5 is the fuel cut control means, the operation state detecting means, the refrigerant pressure correlation value calculating means, and the fuel supply restart. A rotation speed setting unit, an enthalpy difference calculation unit, and a refrigerant flow rate calculation unit are configured. Specifically, the process in FIG. 4 corresponds to the fuel cut control means, the process in FIG. 5 corresponds to the refrigerant pressure correlation value calculation means, and steps S21 to S26, steps S28, and S29 in FIG. 5 corresponds to the rotation speed setting means, steps S41 to S43 in FIG. 5 correspond to the enthalpy difference calculation means, and steps S43 and S44 correspond to the refrigerant flow rate calculation means.

[Modification 1]
The process shown in FIG. 4 may be replaced with the process shown in FIG. In the process of FIG. 9, steps S22 and S23 of FIG. 4 are deleted, step S24 is changed to step S24a, and steps S21a, S24b, and S26a are added.

  If the answer to step S21 is affirmative (YES), that is, immediately after the air-conditioner clutch 31 is engaged, steps S25 and S26 are immediately executed, and then the stable period flag FPSTBL indicating that the stable period is in effect is set to “1”. "(Step S26a). Thereafter, the process proceeds to step S29.

  If the answer to step S21 is negative (NO), the process proceeds to step S21a to determine whether or not the stable period flag FPSTBL is “1”. Initially, the answer is affirmative (YES), so the process proceeds to step S24a to determine whether or not the absolute value of the difference between the refrigerant pressure correlation estimated torque TDCP and the outside air temperature correlation estimated torque TDCTA is smaller than a predetermined torque difference DTDX. To do. If the answer to step S24a is negative (NO), the process proceeds to step S25.

  When the high-pressure side refrigerant pressure Pd increases and the answer to step S24a becomes affirmative (YES), the process proceeds to step S24b, and the stable period flag FPSTBL is returned to “0”. Therefore, after that, the answer to step S21a is negative (NO), and the process immediately proceeds from step S21a to step S27.

  According to the process of FIG. 9, the period from when the air conditioner clutch 31 is engaged until the absolute value of the difference between the refrigerant pressure correlation estimated torque TDCMP and the outside air temperature correlation estimated torque TDCTA becomes smaller than the predetermined torque difference DTDX. This corresponds to the stable period TSTBL in the above-described embodiment. The refrigerant pressure correlation estimated torque TDCP correlates with the high pressure side refrigerant pressure Pd, and the high pressure side refrigerant pressure Pd correlates with the compressor load applied to the engine 1. Therefore, the difference between the refrigerant pressure correlation estimated torque TDCP and the outside air temperature correlation estimated torque TDCTA. When the absolute value of becomes smaller than the predetermined torque difference DTDX, the stable period TSTBL can be set more appropriately by determining that the high-pressure side refrigerant pressure Pd has stabilized.

[Modification 2]
In step S44 of FIG. 5, the refrigerant flow rate Gr is calculated according to the engine speed NE and the pressure difference DP. However, a Gr table for calculating the refrigerant flow rate Gr based only on the engine speed NE is stored in the memory in advance. Alternatively, the refrigerant flow rate Gr may be calculated by searching the Gr table in accordance with the engine speed NE. The Gr table is set such that the refrigerant flow rate Gr increases as the engine speed NE increases.

[Second Embodiment]
In the present embodiment, the fixed displacement compressor 32 in the first embodiment is replaced with a variable displacement compressor 32a as shown in FIG. 10, and a third refrigerant pressure sensor is installed in the second refrigerant passage 37 (upstream of the condenser 33). 44 is provided. Except for the points described below, the second embodiment is the same as the first embodiment.

  The third refrigerant pressure sensor 44 detects the refrigerant pressure (hereinafter referred to as “first high-pressure side refrigerant pressure”) Pda in the second refrigerant passage 37 and supplies the detection signal to the AC-ECU 20. In the present embodiment, the refrigerant pressure Pd detected by the second refrigerant pressure sensor 43 is referred to as “second high-pressure side refrigerant pressure Pd”.

  FIG. 11 is a flowchart of the TDCP calculation process in this embodiment. In this process, steps S43 and S44 of the process shown in FIG. 5 are changed to steps S43a and S44a, respectively.

In step S43a, the enthalpy difference DEN is calculated, and the high pressure side pressure difference DPH is calculated by the following equation (5).
DPH = Pda-Pd (5)
In step S44a, the Gr table shown in FIG. 12 is searched according to the high pressure side pressure difference DPH, and the refrigerant flow rate Gr is calculated.

  Since the variable displacement compressor 32a is used, the refrigerant flow rate Gr cannot be calculated in the same manner as in the first embodiment. Therefore, in the present embodiment, the refrigerant flow rate Gr is set according to the pressure difference DPH between the first high-pressure side refrigerant pressure Pda on the upstream side of the condenser 33 and the second high-pressure side refrigerant pressure Pd on the downstream side by the processing of FIG. I am trying to calculate.

  In the present embodiment, the third refrigerant pressure sensor 44 and the second refrigerant pressure sensor 43 correspond to first high pressure side refrigerant pressure detection means and second high pressure side refrigerant pressure detection means, respectively, and the processing of FIG. This corresponds to the value calculation means, and steps S43a and 44a in FIG. 11 correspond to the refrigerant flow rate calculation means.

[Modification]
The high pressure side enthalpy EPd may be calculated according to the first high pressure side refrigerant pressure Pda instead of the second high pressure side refrigerant pressure Pd.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the first refrigerant pressure sensor 42 is provided to detect the low-pressure side refrigerant pressure Ps, but the low-pressure side refrigerant pressure Ps has a correlation with the surface temperature TSRF of the evaporator 34, The low pressure side refrigerant pressure Ps may be calculated (estimated) by searching the Ps table shown in FIG. 13A according to the temperature TSRF. In this case, the surface temperature sensor 41 and the EG-ECU 5 constitute a low-pressure side refrigerant pressure acquisition unit.

  The refrigerant pressure correlation estimated torque TDCP may be calculated by searching a TDCP table shown in FIG. 13B according to the high-pressure side refrigerant pressure Pd.

  In the above-described embodiment, the substitute value of the refrigerant pressure correlation estimated torque TDCP is calculated according to the outside air temperature TA. However, for example, a predetermined torque value corresponding to the maximum load torque assumed at the start of compressor operation is used. You may make it set. Further, instead of switching the refrigerant pressure correlation estimated torque TDCP to an alternative value in the stable period TSTBL, the fuel supply resumption rotational speed NFCE may be fixed to, for example, the maximum resuming rotational speed NFCEMAX.

  In the embodiment described above, the refrigerant pressure correlation estimated torque TDCP is used as the refrigerant pressure correlation value, but the high-pressure side refrigerant pressure Pd itself may be used. Instead of the outside air temperature TA, for example, as shown in Japanese Patent No. 3417035, an estimated outside air temperature estimated based on the engine coolant temperature TW may be used as the “outside air temperature correlation temperature”. In that case, the cooling water temperature sensor 9 constitutes a part of the outside air correlation temperature acquisition means.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Engine control electronic control unit (Fuel cut control means, operating state detection means, refrigerant pressure correlation value calculation means, fuel supply restart speed setting means, enthalpy difference calculation means, refrigerant flow rate calculation means, low pressure side refrigerant pressure Acquisition means)
6 Fuel injection valve 9 Cooling water temperature sensor (outside air temperature correlation temperature acquisition means)
11 Outside air temperature sensor (outside air temperature correlation temperature acquisition means)
20 Electronic control unit for air conditioner control 23 Air conditioner (air conditioner)
31 Air Conditioner Clutch 32 Compressor 33 Condenser 34 Evaporator 36 First Refrigerant Passage 37 Second Refrigerant Passage 38 Third Refrigerant Passage 41 Surface Temperature Sensor (Low Pressure Side Refrigerant Pressure Acquisition Unit)
42 1st refrigerant | coolant pressure sensor (low pressure side refrigerant | coolant pressure acquisition means)
43 Second refrigerant pressure sensor (refrigerant pressure acquisition means, second high-pressure side refrigerant pressure detection means)
44 3rd refrigerant | coolant pressure sensor (1st high side refrigerant pressure detection means)

Claims (9)

A fuel cut operation for stopping the fuel supply to the engine when the internal combustion engine decelerates is executed. When the engine speed decreases to the fuel supply restart speed, the fuel cut operation is terminated and the fuel supply is resumed. In a control device for an internal combustion engine comprising a fuel cut control means,
Operating state detecting means for detecting the operating state of the compressor of the air conditioning means driven by the engine;
Refrigerant pressure correlation value calculating means for calculating a refrigerant pressure correlation value correlated with the refrigerant pressure of the air conditioning means;
A fuel supply restart speed setting means for setting the fuel supply restart speed according to the refrigerant pressure correlation value;
When the compressor shifts from the non-operating state to the operating state during the fuel cut operation, the fuel supply restart speed setting means substitutes the refrigerant pressure correlation value until a stable period elapses from the transition point. The control apparatus for an internal combustion engine according to claim 1, wherein the rotation speed of the fuel supply is switched to a value and the rotation speed of the fuel supply is set, and the stable period is set as a period until the refrigerant pressure is stabilized after the transition time. It further comprises an outside air temperature correlation temperature acquisition means for acquiring an outside air temperature correlation temperature correlated with the outside air temperature,
The control apparatus for an internal combustion engine according to claim 1, wherein the stable period is set according to the outside air temperature correlation temperature. Further comprising a refrigerant pressure acquisition means for acquiring a refrigerant pressure of the air conditioning means,
3. The control device for an internal combustion engine according to claim 2, wherein the stable period is set to be longer as the outside air temperature correlation temperature is higher, and is set to be longer as the refrigerant pressure immediately after starting the compressor operation is lower.   The control apparatus for an internal combustion engine according to claim 2, wherein the substitute value is set so as to increase as the outside air temperature correlation temperature increases.   The control apparatus for an internal combustion engine according to claim 4, wherein the stable period is a period until a difference between the refrigerant pressure correlation value and the alternative value becomes smaller than a predetermined value.   The control device for an internal combustion engine according to claim 3, wherein the refrigerant pressure correlation value is a driving torque of the compressor estimated based on the refrigerant pressure. Further comprising a refrigerant pressure acquisition means for acquiring a refrigerant pressure of the air conditioning means,
The control apparatus for an internal combustion engine according to claim 4 or 5, wherein the refrigerant pressure correlation value is a driving torque of the compressor estimated based on the refrigerant pressure. The compressor is a fixed capacity compressor, and the refrigerant pressure acquisition unit acquires a high-pressure side refrigerant pressure downstream of the air conditioning unit.
Low pressure side refrigerant pressure acquisition means for acquiring low pressure side refrigerant pressure upstream of the compressor;
An enthalpy difference calculating means for calculating a difference between the enthalpy of the refrigerant on the upstream side of the compressor calculated based on the low-pressure side refrigerant pressure and the enthalpy of the refrigerant on the downstream side of the compressor calculated based on the high-pressure side refrigerant pressure. When,
A rotational speed detecting means for detecting the rotational speed of the engine;
Refrigerant flow rate calculating means for calculating the flow rate of the refrigerant based on the rotational speed of the engine,
The internal combustion engine control according to claim 6 or 7, wherein the refrigerant pressure correlation value calculating means estimates a driving torque of the compressor based on the enthalpy difference, the engine speed, and the refrigerant flow rate. apparatus. The compressor is a variable displacement compressor, and the refrigerant pressure acquisition means detects a first high-pressure side refrigerant pressure that detects a first high-pressure side refrigerant pressure that is an upstream side refrigerant pressure of a condenser provided downstream of the compressor. Detection means and second high-pressure side refrigerant pressure detection means for detecting a second high-pressure side refrigerant pressure that is the refrigerant pressure downstream of the condenser,
Low pressure side refrigerant pressure acquisition means for acquiring low pressure side refrigerant pressure upstream of the compressor;
The difference between the enthalpy of the refrigerant on the upstream side of the compressor calculated based on the low-pressure side refrigerant pressure and the enthalpy of the refrigerant on the downstream side of the compressor calculated based on the first or second high-pressure side refrigerant pressure is calculated. Enthalpy difference calculating means to
A rotational speed detecting means for detecting the rotational speed of the engine;
A refrigerant flow rate calculating means for calculating a flow rate of the refrigerant according to a differential pressure between the first high pressure side refrigerant pressure and the second high pressure side refrigerant pressure;
The internal combustion engine control according to claim 6 or 7, wherein the refrigerant pressure correlation value calculating means estimates a driving torque of the compressor based on the enthalpy difference, the engine speed, and the refrigerant flow rate. apparatus.

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