Engine control device

Abstract

To provide an engine control device capable of suppressing variations of impact on a vehicle in recovery from fuel cut.SOLUTION: An engine control device includes: a recovery processing section for recovering an engine mounted on a vehicle from fuel cut to keep output torque of the engine at target torque in a case where a rotating speed of the engine is lowered to a recovery rotating speed or less during the fuel cut of the engine; a negative torque calculation section for calculating negative torque as torque in a direction opposite to a rotating direction of the engine, which acts on the engine during the fuel cut; an addition torque calculating section for calculating addition torque as torque in the rotating direction of the engine to calculate the target torque; and a target torque calculating section for calculating the target torque on the basis of a value obtained by adding the addition torque to the negative torque.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an engine control device.

Background Art

[0002] When the engine speed drops below the return speed during fuel cut of the engine mounted on a vehicle, a control is known to return the engine from fuel cut so that the output torque of the engine becomes the target torque (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A negative torque, which is a torque in the direction opposite to the engine rotation direction, acts on the engine during fuel cut. The magnitude of the negative torque varies depending on various conditions. Therefore, if the target torque at the time of return from fuel cut is set uniformly regardless of the magnitude of the negative torque, there will be variations in the difference between the negative torque during fuel cut and the target torque at the time of return. As a result, there may be variations in the shock to the vehicle at the time of return from fuel cut, and the drivability may be degraded.

[0005] Therefore, an object of the present invention is to provide an engine control device in which variations in the shock to the vehicle at the time of return from fuel cut are suppressed.

Means for Solving the Problems

[0006] When the engine speed drops below the return speed during fuel cut of the engine mounted on the vehicle, a return processing unit that returns the engine from fuel cut so that the output torque of the engine becomes the target torque, a negative torque calculation unit that calculates a negative torque, which is a torque in the direction opposite to the rotation direction of the engine, acting on the engine during fuel cut, an addition torque calculation unit that calculates an addition torque, which is a torque in the rotation direction of the engine, for calculating the target torque, and a target torque calculation unit that calculates the target torque based on a value obtained by adding the addition torque to the negative torque are provided. , the addition torque calculation unit calculates the addition torque as a value smaller than the magnitude of the negative torque. The vehicle is equipped with a transmission and a torque converter having a lock-up clutch for transmitting the output torque of the engine to the transmission. The addition torque calculation unit calculates the addition torque in the engaged state of the lock-up clutch as a smaller value than the addition torque in the slip state of the lock-up clutch, and calculates the addition torque as a smaller value as the gear stage of the transmission is lower. It can be achieved by an engine control device.

[0009] The return processing unit may decrease the retard amount of the ignition timing at the time of returning the engine from fuel cut as the addition torque is larger.

[0010] An alternator and an air conditioner compressor linked to the rotation of the engine are mounted on the vehicle, and the negative torque calculation unit may calculate the negative torque based on the friction torque of the engine, the pumping loss torque of the engine, the load torque of the alternator, and the load torque of the compressor.

Advantages of the Invention

[0011] According to the present invention, an engine control device can be provided in which variations in shock to the vehicle at the time of returning from fuel cut are suppressed.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0013] [Schematic Configuration of Vehicle] FIG. 1 is a schematic configuration diagram of a vehicle 1. The vehicle 1 includes an engine 10, a torque converter 20, a lock-up clutch (hereinafter referred to as an LU clutch) 30, a transmission 40, a differential device 50, drive wheels 60, a hydraulic control circuit 70, an alternator 80, a compressor 85, an ECU (Electronic Control Unit) 100, and the like.

[0014] The engine 10 is a driving force source for traveling and is a multi-cylinder gasoline engine, but is not limited thereto, and may be, for example, a diesel engine. A crankshaft 11, which is an output shaft of the engine 10, is connected to the torque converter 20.

[0015] The torque converter 20 includes a pump impeller 21 on the input shaft side, a turbine runner 22 on the output shaft side, a stator 23 that exhibits a torque amplification function, and a one-way clutch 24, and performs power transmission between the pump impeller 21 and the turbine runner 22 via a fluid. The LU clutch 30 is provided in the torque converter 20. The LU clutch 30 is a single-plate or multi-plate hydraulic friction clutch that directly connects or connects the input side and the output side of the torque converter 20 in a slip state.

[0016] The transmission 40 is a stepped automatic transmission and includes a plurality of hydraulic friction engagement elements and a planetary gear device. In the transmission 40, a plurality of gear ratios can be selectively established by selectively engaging a plurality of friction engagement elements. As shown in FIG. 1, the input shaft 41 of the transmission 40 is connected to the turbine shaft 26 of the torque converter 20. The turbine shaft 26 corresponds to the output shaft of the torque converter 20. The output shaft 42 of the transmission 40 is connected to the drive wheels 60 via a differential device 50 or the like.

[0017] According to the shift range of the transmission 40 being the parking range, reverse travel range, neutral range, and forward travel range, the engagement and release of a plurality of friction engagement elements are controlled. Also, in the case of the forward travel range, the engagement and release of a plurality of friction engagement elements are controlled so that one of the eight forward gear ratios is selectively established according to the accelerator opening degree, vehicle speed, etc. Among the eight forward gears, the lowest speed gear ratio with the largest gear ratio is the first speed gear, and the highest speed gear ratio with the smallest gear ratio is the eighth speed gear. The plurality of friction engagement elements are specifically a plurality of clutches and a plurality of brakes. Note that the transmission 40 is not limited to an automatic transmission and may be, for example, a manual transmission. The number of gear ratios that can be established in the transmission 40 is eight forward gears, but it is not limited to this, and it is sufficient if a plurality of gear ratios with different gear ratios can be established.

[0018] The hydraulic control circuit 70 is a known hydraulic control circuit that uses a mechanical oil pump driven by the engine 10 as a hydraulic supply source, supplies hydraulic pressure to the torque converter 20, the LU clutch 30, and the transmission 40, and controls the operations of each of them. Also, when the hydraulic command value output from the ECU 100 is input to the hydraulic control circuit 70, the supply hydraulic pressure to the torque converter 20, the LU clutch 30, and the transmission 40 is controlled based on the hydraulic command value. Also, the LU clutch 30 can be switched to either a released state, a slip state, or an engaged state according to the supplied hydraulic pressure.

[0019] The alternator 80 and the compressor 85 are auxiliary machines of the engine 10 and are interlocked with the rotation of the engine 10. Specifically, each of the alternator 80 and the compressor 85 is driven by transmitting the rotational force of the crankshaft 11 via a pulley and a timing belt. The alternator 80 rotates the field coil in an excited state to generate induced power in the stator coil, and the rectifier converts the induced current into a direct current to charge a battery (not shown). The compressor 85 is a compressor for an air conditioner and is of a variable capacity type whose discharge capacity can be adjusted. For example, it is a swash plate type (double swash plate type or single swash plate type) that changes the piston stroke and thus the discharge capacity by changing the inclination of the swash plate that drives the piston.

[0020] The ECU 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a backup RAM, etc. The ROM stores various control programs and maps, etc. that are referred to when executing these various control programs. The CPU executes arithmetic processing based on the various control programs and maps stored in the ROM. Also, the RAM is a memory that temporarily stores the arithmetic results in the CPU and the data input from each sensor, etc., and the backup RAM is a non-volatile memory that stores data, etc. that should be saved when the ignition is off, etc. The CPU, ROM, RAM, and backup RAM functionally realize a return processing unit, a negative torque calculation unit, an addition torque calculation unit, and a target torque calculation unit, which will be described in detail later.

[0021] The ECU 100 is connected to various sensors and switches such as an intake manifold pressure sensor 90, an engine speed sensor 91, a turbine speed sensor 92, an output shaft speed sensor 93, an accelerator opening sensor 94, a vehicle speed sensor 95, a gear position sensor 96, an ignition switch 97, and a refrigerant pressure sensor 98, and signals from these sensors and switches are input to the ECU 100. The ECU 100 controls the operating state of the engine 10 and the gear position of the transmission 40 based on the detection results of various sensors and the like. The ECU 100 is an example of an engine control device that controls the engine 10.

[0022] The intake manifold pressure sensor 90 detects the pressure in the intake pipe on the downstream side of the throttle valve of the engine 10. The engine speed sensor 91 detects the rotational speed of the crankshaft 11 (referred to as the engine speed). The turbine speed sensor 92 detects the rotational speed of the turbine shaft 26 of the torque converter 20 (referred to as the turbine speed). The output shaft speed sensor 93 detects the rotational speed of the output shaft 42 of the transmission 40 (referred to as the output shaft speed). The accelerator opening sensor 94 detects the accelerator opening operated by the accelerator pedal. The vehicle speed sensor 95 detects the traveling speed of the vehicle 1. The gear position sensor 96 detects the gear position established in the transmission 40. The ignition switch 97 detects the on and off of the ignition. The refrigerant pressure sensor 98 detects the refrigerant pressure of the air conditioner mounted on the vehicle 1.

[0023] When the accelerator opening becomes 0 or less than or equal to the threshold value, the ECU 100 executes a fuel cut that stops the fuel supply to the engine 10. As a result, the vehicle 1 decelerates. If the engine speed drops below the return speed while the accelerator opening remains 0 or less than or equal to the threshold value during the fuel cut, the ECU 100 resumes the fuel supply to the engine 10 to drive the engine 10 in order to avoid stalling. The return from such a fuel cut is referred to as a natural return. Also, when the accelerator pedal is depressed by the driver during the fuel cut and the accelerator opening exceeds the threshold value, the ECU 100 resumes the fuel supply to the engine 10 to drive the engine 10 in accordance with the driver's request. The return from such a fuel cut is referred to as a forced return.

[0024] [Fuel Cut Resume Control] Figure 2 is a flowchart illustrating the fuel cut resume control executed by the ECU 100. This control is repeatedly executed at a predetermined cycle while the ignition is on. The ECU 100 determines whether it is in the fuel cut state (step S1). If the answer in step S1 is No, this control ends. If the answer in step S1 is Yes, the ECU 100 determines whether there is a natural resume request (step S2). If the answer in step S2 is No, the ECU 100 determines whether there is a forced resume request (step S3). If the answer in step S3 is No, this control ends. If the answer in step S3 is Yes, the ECU 100 calculates the target torque at the time of resume based on the accelerator opening degree, etc. (step S4). Next, the ECU 100 executes a resume process to resume the fuel supply to the engine 10 by controlling the fuel injection amount, intake air amount, ignition timing, etc. so that the output torque of the engine 10 matches the target torque (step S8).

[0025] If the answer in step S2 is Yes, the ECU 100 calculates a negative torque, which is a torque in the direction opposite to the rotation direction of the engine 10 during fuel cut (step S5). Step S5 is an example of the process executed by the negative torque calculation unit. For example, the negative torque is the sum of the friction torque of the engine 10, the pumping loss torque of the engine 10, the load torque of the alternator 80, and the load torque of the compressor 85. All of these torques act in the direction opposite to the rotation direction of the engine 10. The ECU 100 calculates these torques based on the following maps.

[0026] Figure 3A is an example of a map defining the friction torque of the engine 10. Figure 3B is an example of a map defining the pumping loss torque of the engine 10. Figure 4A is an example of a map defining the load torque of the alternator 80. Figure 4B is an example of a map defining the load torque of the compressor 85. These maps are defined in advance based on experimental results and simulation results and are stored in the ROM of the ECU 100.

[0027] As shown in FIG. 3A, the higher the engine speed [rpm] detected by the engine speed sensor 91, the greater the magnitude of the friction torque [N·m]. As shown in FIG. 3B, the lower the intake manifold pressure [Pa] detected by the intake manifold pressure sensor 90, the greater the magnitude of the pumping loss torque [N·m]. As shown in FIG. 4A, the higher the required power generation current [A] to the alternator 80, the greater the magnitude of the load torque [N·m] of the alternator 80. As shown in FIG. 4B, the higher the refrigerant pressure [Pa] of the air conditioner detected by the refrigerant pressure sensor 98, the greater the magnitude of the load torque [N·m] of the compressor 85. When there is no power generation request to the alternator 80 or when the air conditioner is off, the ECU 100 calculates the respective load torques of the alternator 80 and the compressor 85 as zero. Using the map as described above, the ECU 100 calculates the negative torque.

[0028] In addition, the pumping loss torque may be calculated so as to increase as the engine speed increases in addition to the intake manifold pressure. The load torque of the alternator 80 may be calculated so as to increase as the engine speed increases in addition to the required power generation current to the alternator 80. The load torque of the compressor 85 may be calculated so as to increase as the engine speed increases in addition to the refrigerant pressure of the air conditioner. Also, the negative torque may be calculated by an arithmetic expression using the engine speed, intake manifold pressure, required power generation current, refrigerant pressure, etc. as arguments. Instead of the required power generation current, the detected value of the power generation current of the alternator 80 may be used. Additionally, the friction torque of the engine 10, the pumping loss torque of the engine 10, the load torque of the alternator 80, and the load torque of the compressor 85 may be calculated by known methods.

[0029] Next, the ECU 100 calculates an additional torque for calculating the target torque (step S6). Step S6 is an example of the process executed by the additional torque calculation unit. FIG. 5 is an example of a map defining the additional torque. As shown in FIG. 5, the lower the gear position, the smaller the additional torque. This is because when the gear position is lower, the shock to the vehicle 1 due to the increase in the output torque of the engine 10 at the time of return is greater. Also, the additional torque in the engaged state of the LU clutch 30 is smaller than the additional torque in the case where the LU clutch 30 is in a slip state. This is because when the LU clutch 30 is in the engaged state rather than the slip state, the shock to the vehicle 1 due to the increase in the output torque of the engine 10 at the time of return is greater.

[0030] Incidentally, the gear position can be detected by the gear position sensor 96. The state of the LU clutch 30 can be determined based on the differential rotational speed between the engine rotational speed and the turbine rotational speed. For example, when this differential rotational speed is equal to or less than the threshold value, it can be determined that the LU clutch 30 is in the engaged state, assuming that the engine rotational speed and the turbine rotational speed are substantially constant. Also, when the differential rotational speed is within a predetermined range greater than the threshold value, it can be determined that the LU clutch 30 is in the slip state, assuming that the engine rotational speed and the turbine rotational speed do not match. Incidentally, the state of the LU clutch 30 may be detected by other known methods. For example, the state of the LU clutch 30 may be determined based on the detection value of a hydraulic pressure sensor that detects the hydraulic pressure supplied to the LU clutch 30.

[0031] Here, the magnitude of the above-described additional torque is calculated to be smaller than the magnitude of the calculated negative torque. That is, the maximum value of the additional torque is set to a value smaller than the minimum value of the negative torque.

[0032] Next, the ECU 100 calculates the target torque by adding the additional torque to the negative torque (step S7). Step S7 is an example of the process executed by the target torque calculation unit. As described above, the magnitude of the additional torque is smaller than the magnitude of the calculated negative torque. Therefore, the target torque is calculated as a negative value. Next, the ECU 100 executes a return process according to the target torque calculated as described above (step S8). Step S8 is an example of the process executed by the return processing unit. Thereby, compared with the case where the target torque at the time of return from fuel cut is calculated as a positive value, the shock to the vehicle 1 at the time of return can be suppressed.

[0033] Also, in the return process when there is a natural return request, the ECU 100 decreases the retard amount of the ignition timing of the engine 10 as the additional torque increases. Specifically, when the additional torque is less than or equal to a predetermined value, the retard amount of the ignition timing of the engine 10 decreases as the additional torque increases. Thereby, the magnitude of the additional torque can be ensured, and the deterioration of fuel consumption due to the retard of the ignition timing can be suppressed. Note that the retard amount of the ignition timing is the retard amount from a predetermined ignition timing, for example, the retard amount from the MBT (Minimum advance for the Best Torque) ignition timing.

[0034] As described above, the target torque at the time of natural return is calculated by adding a predetermined additional torque to the negative torque during fuel cut. Therefore, the difference between the negative torque during fuel cut and the target torque at the time of natural return can be made constant, and the variation in the shock to the vehicle 1 at the time of return is also suppressed.

[0035] In the above-described embodiment, the sum of the friction torque of the engine 10, the pumping loss torque of the engine 10, the load torque of the alternator 80, and the load torque of the compressor 85 is calculated as the negative torque, but it is not limited thereto. For example, the sum of the friction torque and the pumping loss torque may be calculated as the negative torque. Even if the load torques of the alternator 80 and the compressor 85 are excluded from the negative torque, by calculating the target torque based on the negative torque including the friction torque and the pumping loss torque, the occurrence of shock at the time of fuel cut return can be suppressed more than when the target torque is uniformly set regardless of the magnitude of the negative torque.

[0036] As described above in detail with respect to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0037] 1 Vehicle 10 Engine 20 Torque Converter 30 Lock-up Clutch 40 Transmission 80 Alternator 85 Compressor 100 ECU (Engine Control Unit, Return Processing Unit, Negative Torque Calculation Unit, Added Torque Calculation Unit, Target Torque Calculation Unit)

Claims

1. When the rotational speed of the engine mounted on the vehicle drops below the return rotational speed during fuel cut of the engine, a return processing unit that returns the engine from fuel cut so that the output torque of the engine becomes the target torque; A negative torque calculation unit that calculates a negative torque, which is a torque in a direction opposite to the rotational direction of the engine and acts on the engine during fuel cut; An addition torque calculation unit that calculates an addition torque, which is a torque in the rotational direction of the engine, for calculating the target torque; A target torque calculation unit that calculates the target torque based on a value obtained by adding the addition torque to the negative torque, and the addition torque calculation unit calculates the addition torque as a value smaller than the magnitude of the negative torque, the vehicle is equipped with a transmission and a torque converter having a lock-up clutch that transmits the output torque of the engine to the transmission, the addition torque calculation unit calculates the addition torque in the engaged state of the lock-up clutch as a smaller value than the addition torque in the slip state of the lock-up clutch, and calculates the addition torque as a smaller value as the gear stage of the transmission is lower. An engine control device.

2. The return processing unit according to claim 1, wherein the larger the addition torque is, the smaller the retard angle amount of the ignition timing at the time of return of the engine from fuel cut is.

3. The vehicle is equipped with an alternator linked to the rotation of the engine and a compressor for an air conditioner, The negative torque calculation unit according to claim 2, wherein the negative torque is calculated based on the friction torque of the engine, the pumping loss torque of the engine, the load torque of the alternator, and the load torque of the compressor.

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