JP2011085031A - Engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control device capable of improving fuel economy and capable of securing a brake force required to stop a travelling vehicle in economic traveling control. <P>SOLUTION: In an engine control device for stopping fuel injection based on required conditions that an accelerator is not operated even in travelling and booster negative pressure is higher than a set threshold value, a set threshold value P<SB>os</SB>is set based on at least one of the accelerator operated quantity L(S27-29) and an operated quantity changing speed V<SB>L</SB>(S22, 23). By this, in the case that a large brake force is estimated to be required, the set threshold value can be set at a large value (S24), and in the other case, the set threshold value can be set at a value smaller than the highly set value (S26). In the economic traveling control, fuel economy can be improved and the brake force required to stop a travelling vehicle can be secured. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  According to the present invention, on the condition that the accelerator operating member is not operated and the negative pressure in the negative pressure chamber of the vacuum booster is higher than a set threshold pressure, the engine is stopped so as to stop fuel injection into the engine. The present invention relates to an engine control device to be controlled.

  In recent years, for the purpose of improving fuel consumption, reducing emissions, etc., engine control that can perform so-called eco-run control, such as control that stops fuel injection to the engine when the vehicle is stopped due to a signal, etc. Devices have been studied and are already in practical use. If the driver has a clear intention to stop the vehicle even if the vehicle is traveling for the purpose of further improving fuel consumption, reducing emissions, etc., specifically, for example, the accelerator operation member by the driver. An engine control device that performs eco-run control even when the brake is not operated and the brake operation member is operated has been studied. The following patent document describes an example of an engine control device that stops fuel injection to the engine in eco-run control even during traveling.

JP 2002-221959 A

  As a condition for stopping fuel injection in the eco-run control even when the vehicle is traveling, it is usually adopted that the accelerator operation member is not operated and the brake operation member is operated. ing. And the conditions regarding the negative pressure state of the vacuum booster for boosting the operating force applied to the brake operating member may be further employed. The vacuum booster is structured to boost the operating force applied to the brake operating member by utilizing the pressure difference between the negative pressure chamber's air pressure and atmospheric pressure, and the vacuum booster's negative pressure As a negative pressure source for bringing the chamber into a negative pressure state, an intake portion of the engine is usually employed. For this reason, when the engine stops, the booster negative pressure, which is the negative pressure of the vacuum chamber of the vacuum booster, decreases, in other words, the air pressure in the negative chamber increases, and the vacuum booster operates the brake operating member. There is a risk that it will be difficult to boost the power. Therefore, it is adopted as the above condition that the booster negative pressure is in a somewhat high state, specifically, that the booster negative pressure is higher than the set threshold pressure.

  The condition regarding booster negative pressure is to ensure the boosting effect of the operation force of the brake operation by the driver, and the booster negative pressure is set to a certain level to ensure the braking force necessary to stop the vehicle. It is for maintaining. In particular, when the fuel injection is stopped while the vehicle is running in the eco-run control, it is necessary to maintain the booster negative pressure at a certain high level in order to stop the running vehicle with certainty. For this reason, it is desirable that the booster negative pressure threshold, which is the set threshold pressure of the booster negative pressure, be set to a large value to some extent. However, if the booster negative pressure threshold is set to a large value, the booster negative pressure is unlikely to be higher than the booster negative pressure threshold, and it is difficult to execute the eco-run control. That is, if the booster negative pressure threshold value is set to a large value, the frequency of stopping the engine is reduced, and it becomes difficult to improve fuel consumption, reduce emissions, and the like. The present invention has been made in view of such circumstances. In the eco-run control, a booster negative pressure is provided so as to improve the fuel consumption and secure the braking force necessary to stop the running vehicle. It is an object to provide an engine control device capable of setting a threshold value.

In order to solve the above problems, an engine control device of the present invention provides:
An engine control device for controlling an engine having an intake portion connected to a negative pressure chamber of a vacuum booster that boosts an operation force applied to a brake operation member,
An engine operation control unit that controls the operation of the engine by controlling the fuel injection amount to the engine according to the operation amount of the accelerator operation member;
Even if the vehicle is running, the accelerator operating member is not operated, and the booster negative pressure, which is the negative pressure of the negative pressure chamber, is higher than a set threshold pressure. A fuel injection stop section for stopping fuel injection into the engine;
A booster negative pressure threshold setting unit that sets the set threshold pressure of the booster negative pressure based on at least one of an operation amount of the accelerator operation member and a change speed of the operation amount.

  In the engine control apparatus of the present invention, the “operation amount change speed” is a change amount of the operation amount of the accelerator operation member per unit time, and is a speed at which the driver operates the accelerator operation member, that is, an operation by the driver. It may be a speed, or may be a speed changed by some member provided on the accelerator operation member. Specifically, many of the accelerator operation members have an elastic body that deforms according to the operation amount thereof, and the operation amount is reduced depending on the elastic force of the elastic body. For this reason, when the driver releases the accelerator operating member in a state where the accelerator operating member is being operated by the driver, the changing speed of the operation amount of the accelerator operating member is a speed that can be reduced by the elastic body. . Further, the “operation amount change speed” may be an increase speed of the operation amount or a decrease speed.

  Further, the “fuel injection stop unit” in the engine control device of the present invention satisfies a predetermined condition including that the accelerator operating member is not operated and the booster negative pressure is higher than the set threshold pressure. In addition, the fuel injection is stopped. As predetermined conditions, various conditions other than the above conditions, specifically, that the brake operation member is operated, and the traveling speed of the vehicle is lower than the set threshold speed. It may be adopted. When a plurality of conditions are adopted as the predetermined conditions, the fuel injection to the engine is stopped when all of the plurality of conditions are satisfied.

Further, the “booster negative pressure threshold setting unit” in the engine control device of the present invention is:
It may be configured to set the set threshold pressure based on at least a reduction rate of the operation amount of the accelerator operation member,
Further, the set threshold pressure is set to a specific value when the decrease speed is lower than the set threshold speed, and is set to a value larger than the specific value when the decrease speed is equal to or higher than the set threshold speed. It may be configured to set.

  When the “booster negative pressure threshold setting unit” is configured to set the set threshold pressure based on the decrease speed, as described above, when the decrease speed is lower than the set threshold speed, Depending on the case, the set threshold pressure may be set to a different value, or the set threshold pressure may be set to a higher value as the decrease rate is higher.

Further, the “booster negative pressure threshold setting unit” in the engine control device of the present invention is:
It may be configured to set the set threshold pressure based on at least the operation amount of the accelerator operation member,
Further, the set threshold pressure is set to a specific value when the operation amount of the accelerator operation member is smaller than the set threshold amount, and when the operation amount of the accelerator operation member is equal to or greater than the set threshold amount, You may comprise so that it may set to a bigger value than a certain specific value.

  When the “booster negative pressure threshold setting unit” is configured to set the set threshold pressure based on the operation amount of the accelerator operation member, as described above, the operation amount is set to be smaller than the set threshold amount. The set threshold pressure may be set to a different value depending on whether or not the threshold amount is exceeded, or the set threshold pressure may be set to a higher value as the operation amount is larger.

When the set threshold pressure is set based on the operation amount of the accelerator operation member and the decreasing speed of the operation amount, the “booster negative pressure threshold setting unit” in the engine control device of the present invention is
The set threshold pressure is set to a specific value when the operation amount of the accelerator operation member is less than the set threshold amount and the decrease speed is lower than the set threshold speed, and the operation amount of the accelerator operation member is When the amount is equal to or greater than the set threshold amount, or when the rate of decrease is equal to or greater than the set threshold rate, it may be configured to set a value larger than the specific value. In such a configuration, the value set when the manipulated variable is equal to or greater than the set threshold speed and the value set when the manipulated variable decrease rate is equal to or greater than the set threshold speed are the same value. Or different values.

  The magnitude of the braking force that must be secured to stop the vehicle varies depending on the traveling state of the vehicle. More specifically, for example, the braking force to be secured when the vehicle is traveling at a high speed is larger than the braking force to be secured when the vehicle is traveling at a low speed. Further, for example, the braking force that should be ensured against a sudden braking operation is greater than the braking force that should be ensured against a gentle braking operation. The booster negative pressure threshold value is for ensuring the boosting effect of the operating force of the brake operation by the driver. When the braking force to be ensured is large, the booster negative pressure threshold value is set to a large value. If the braking force to be secured is not so large, the booster negative pressure threshold need not be set to a large value.

  In the engine control device of the present invention, the booster negative pressure threshold can be set based on at least one of the operation amount of the accelerator operation member and the change speed of the operation amount, and the operation amount of the accelerator operation member It is possible to estimate the traveling state of the vehicle as described above from at least one of the change rate of the operation amount. Therefore, according to the engine control apparatus of the present invention, for example, when it is estimated that a large braking force is required, the booster negative pressure threshold is set to a large value, and in other cases, the booster negative pressure threshold is set to a large value. The booster negative pressure threshold can be set to a value smaller than the value.

  Specifically, when the amount of accelerator operation is large, it is estimated that the vehicle is traveling at high speed, so it is estimated that a large braking force is necessary, and the booster negative pressure threshold is set to a large value. It becomes possible to do. In addition, when the decrease rate of the accelerator operation amount is high, it is estimated that the driver is decreasing the accelerator operation amount so as to rapidly decrease the traveling speed of the vehicle, and a sudden brake operation is assumed. The For this reason, when the decrease rate of the accelerator operation amount is high, it is estimated that a large braking force is necessary for the sudden braking operation, and the booster negative pressure threshold can be set to a large value. In other words, in normal times, the booster negative pressure threshold that can guarantee the normal braking force is set, and when it is estimated that a large braking force is necessary based on the operation state of the accelerator operating member, the booster negative pressure threshold is set to the normal value. By setting the value larger than the threshold value, it is possible to improve the fuel consumption and secure the braking force required to stop the running vehicle.

1 is a diagram schematically showing a vehicle drive system including an engine control apparatus according to an embodiment of the present invention together with a brake system. It is a figure which shows the brake system of FIG. 1 schematically. It is a schematic sectional drawing which shows the vacuum booster and master cylinder with which the brake system of FIG. 1 and FIG. 2 is provided. It is a flowchart which shows an engine control program. It is a flowchart which shows the booster negative pressure threshold value setting subroutine for a stop performed in an engine control program. It is a flowchart which shows the fuel-injection propriety flag determination subroutine performed in an engine control program.

  Hereinafter, as the best mode for carrying out the present invention, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following Example, It can implement in the various aspect which gave various change and improvement based on the knowledge of those skilled in the art.

<Configuration of vehicle drive system>
FIG. 1 schematically shows a vehicle drive system 12 including an engine electronic control unit (hereinafter, simply referred to as “engine ECU”) 10 of an embodiment provided in a vehicle. The drive system 12 includes an engine 20, a torque converter 22, a transmission 23, and a differential device 24. The engine 20 installed in the engine room in front of the vehicle is connected to a transmission 23 via a torque converter 22, and the output of the transmission 23 is transmitted to the left and right front wheels 25 FR and FL via a differential device 24. Communicated. That is, the drive system 12 is configured such that the engine 20 drives the front wheels 25FR and FL as drive wheels via the torque converter 22, the transmission 23, and the differential device 24. Further, a generator 26 is connected to the engine 20, and the generator 26 generates power as the engine 20 rotates, and the generated power is charged in the battery 28.

  The engine ECU 10 is an engine control device for controlling the engine 20, and is an electronically controlled throttle that adjusts the amount of air sucked into the engine 20 according to the amount of operation of an accelerator pedal as an accelerator operation member by a driver. The operation of the engine 20 is controlled by controlling the valve 30 (see FIG. 2), the fuel injection device 32 (see FIG. 2), and the like. Since the control method of the engine 20 is a well-known technique, a detailed description thereof will be omitted. However, in brief description, the engine ECU 10 includes a controller 34, a throttle mainly composed of a computer having a CPU, a ROM, a RAM, and the like. A drive circuit 36 corresponding to the drive source of the valve 30 and a drive circuit 38 corresponding to the drive source of the fuel injection device 32 are provided. The controller 34 is connected to an accelerator pedal stroke sensor [AS] 40 that detects the amount of operation of the accelerator pedal, and is further connected to the drive circuits 36 and 38. The controller 34 controls the drive circuits 36 and 38 based on the detection value from the accelerator pedal stroke sensor 40 to control the air intake amount and the fuel injection amount to the engine 20. The operation of the engine 20 is controlled according to the operation amount of the pedal. More specifically, with respect to the fuel injection amount, when the accelerator pedal is operated, that is, when the accelerator pedal operation amount detected by the accelerator pedal stroke sensor 40 is not zero, the fuel is based on the operation amount. Is determined, and the determined amount of fuel is injected. On the other hand, when the accelerator pedal is not operated, that is, when the operation amount of the accelerator pedal is 0, the fuel injection amount is set to 0, and the fuel injection is stopped.

  Further, when the operation of the accelerator pedal is released from the state where the accelerator pedal is operated, that is, when the operation amount becomes 0, the fuel injection to the engine 20 is stopped, and the rotational speed of the engine 20 is reduced. descend. Since the engine 20 stops when the rotational speed of the engine 20 becomes too low, so-called idling control is executed to maintain the rotational speed of the engine 20 in order to avoid stopping the engine 20 due to a decrease in the engine rotational speed. . That is, even when the accelerator pedal is not operated, the intake air amount to the engine 20 and the fuel injection amount are controlled to prevent the engine stall. Further, a starter motor 44 is connected to the engine 20, and a drive circuit 46 for the starter motor 44 is connected to the controller 34. When starting the stopped engine 20, the controller 34 controls the drive circuit 46 and the drive circuits 36 and 38, thereby starting the engine 20.

<Configuration of vehicle brake system>
Further, in a vehicle equipped with the present drive system 12, only the brake devices 50 provided for the respective wheels 25 (in FIG. 1, only the brake devices 50 provided for the right front wheel 25FR and the right rear wheel 25RR are illustrated. The brake system 52 equipped with the above is mounted. Each brake device 50 is a disc brake device, and includes a brake disc 54 that rotates together with the wheels 25, a brake caliper 55 that is attached to the vehicle body, a cylinder 56 (see FIG. 2) and a brake pad that are held by the brake caliper 55. 57 (see FIG. 2). When the brake pedal 58 as a brake operation member is operated by the driver's operation force, the operation force is boosted by the vacuum booster 60 connected to the brake pedal 58. Further, the boosted operating force is transmitted to the master cylinder 62 connected to the vacuum booster 60, and pressurizes the hydraulic fluid contained therein. The change in hydraulic fluid pressure is transmitted from the master cylinder 62 to the brake caliper 55 of the brake device 50 provided on each wheel 25 through the hydraulic fluid pipes 64a and 64b. Although a detailed description of the structure of the brake device 50 is omitted, the cylinder 56 is operated by pressurized hydraulic fluid and presses the brake pad 57 against the brake disc 54. Therefore, the brake device 50 can generate a braking force for decelerating the vehicle by suppressing the rotation of the wheel 25 by the friction generated between the brake pad 57 and the brake disk 54.

  As shown in FIG. 2, the vacuum booster 60 includes a negative pressure chamber 70 that is in a negative pressure state, and the negative pressure chamber 70 is provided with a suction port 72. A communication passage 74 is connected to the suction port 72, and the communication passage 74 is connected to a branch portion 78 of the intake manifold 76. The intake manifold 76 has openings at both ends thereof and functions as an air supply pipe for supplying air to the engine 20. More specifically, one opening of the intake manifold 76 serves as a suction port 80 for sucking air from the atmosphere, and the other opening is connected to an intake portion 82 for the engine 20 to suck air. . Further, the throttle valve 30 is installed between the intake port 80 of the intake manifold 76 and the branching portion 78. Since the throttle valve 30 can adjust the amount of air sucked into the engine 20 as described above, there is no throttle between the throttle valve 30 and the intake portion 82 inside the intake manifold 76. The negative pressure state corresponding to the opening degree of the valve 30 and the rotational speed of the engine 20 is set. Therefore, the communication path 74 connected to the branching portion 78 and the negative pressure chamber 70 are also brought into a negative pressure state. That is, the brake system 52 is configured such that the intake manifold 76 serves as a negative pressure source for bringing the negative pressure chamber 70 into a negative pressure state. The fuel injection device 32 is provided between the branching portion 78 and the intake portion 82 of the intake manifold 76, and the fuel injection device 32 injects fuel, so that the air-fuel mixture is mixed. Is sucked into the combustion chamber of the engine 20.

  In addition, a check valve 88 is provided in the communication path 74, and the check valve 88 allows negative pressure to be supplied from the intake manifold 76 to the negative pressure chamber 70, but from the negative pressure chamber 70 to the intake manifold 76. Supply of negative pressure to is prohibited. In other words, the check valve 88 prohibits the supply of air from the intake manifold 76 to the negative pressure chamber 70, but allows the supply of air from the negative pressure chamber 70 to the intake manifold 76. For this reason, when the engine negative pressure that is the negative pressure of the intake manifold 76 is higher than the booster negative pressure that is the negative pressure of the negative pressure chamber 70, that is, when the absolute atmospheric pressure of the intake manifold 76 is lower than the absolute pressure of the negative pressure chamber 70. Accordingly, the check valve 88 is opened, and the air in the negative pressure chamber 70 is sucked into the intake manifold 76. On the other hand, when the negative pressure in the negative pressure chamber 70 is higher than the negative pressure in the intake manifold 76, that is, when the absolute atmospheric pressure in the negative pressure chamber 70 is lower than the absolute atmospheric pressure in the intake manifold 76, the check valve 88 is closed. Air in the negative pressure chamber 70 is not sucked into the intake manifold 76.

  FIG. 3 is a cross-sectional view of the vacuum booster 60 and the master cylinder 62. The vacuum booster 60 includes a hollow housing 90 and a power piston 92 provided in the housing 90. The power piston 92 includes a hub 94 and a diaphragm 96, and the housing 90 includes a negative pressure chamber 70 on the master cylinder 62 side and a variable pressure chamber 98 on the brake pedal 58 side by the hub 94 and the diaphragm 96. It is divided into and.

  A recess 100 is provided on the hub 94 on the master cylinder 62 side. A rubber reaction disk 102 is inserted into the recess 100, and one end of the push rod 104 is inserted into the recess 100. The other end of the push rod 100 is engaged with the pressure piston 106 a of the master cylinder 62. A compression coil spring 108 is disposed in parallel with the push rod 104.

  The master cylinder 62 includes a housing 110 and two pressure pistons 106a and 106b. The two pressure pistons 106a and 106b are arranged in series inside the housing 110, and are fitted into the housing 110 so as to be slidable inside. Further, the master cylinder 62 is provided with two pressurizing chambers 114a and 114b adjacent to the two pressurizing pistons 106a and 106b, respectively. The pressurizing chambers 114a and 114b are respectively compressed. Coil springs 116a and 116b are provided.

  A stepped hole 118 communicating with the recess 100 is provided on the brake pedal 58 side of the hub 94, and a reaction rod 120 is fitted therein. The reaction rod 120 is engaged with one end of the valve operating rod 122, and the other end of the valve operating rod 122 is connected to the brake pedal 58. The hub 94 and the reaction rod 120 are coupled to each other at a stepped hole 118 by a plate-like stopper key 124. Therefore, when the brake pedal 58 is operated, the hub 94 is moved through the valve operating rod 122 and the reaction rod 120, and further, the pressure is applied through the reaction disk 102 and the push rod 100 by the movement of the hub 94. The piston 106a is moved. That is, the negative pressure booster 60 and the master cylinder 62 are configured such that the pressurizing piston 106a is moved by the operation of the brake pedal 58.

  When the pressurizing piston 106a is moved by operating the brake pedal 58, since the pressurizing chamber 114a is filled with the working fluid, the working fluid in the pressurizing chamber 114a is pressurized, and the pressurizing piston 106b is , And moved by the pressurized hydraulic fluid. Further, when the pressure pistons 106a and 106b are moved and the pressure of the hydraulic fluid in the pressure chambers 114a and 114b is increased, the pressure of the hydraulic fluid is increased through the hydraulic fluid pipes 64a and 64b. The brake device 50 generates a braking force. Incidentally, the hydraulic fluid piping 64a is connected to the pressurizing chamber 114a, and the hydraulic fluid piping 64b is connected to the pressurizing chamber 114b. Is transmitted to the brake cylinder 56. Incidentally, the hydraulic fluid pipe 64a is connected to two brake cylinders 56 disposed on the left front wheel 25FL and the right rear wheel 25RR, and the hydraulic fluid pipe 64b is provided with two brakes disposed on the right front wheel 25FR and the left rear wheel 25RL. The cylinder 56 is connected.

  A valve mechanism 126 is provided inside the hub 94. Although detailed explanation is omitted, the valve mechanism 126 is configured to be able to communicate or block the negative pressure chamber 70 and the variable pressure chamber 98 or to communicate or block the variable pressure chamber 98 and the atmosphere. The valve mechanism 126 can communicate and block these in conjunction with the valve operating rod 122 that is moved in response to the operation of the brake pedal 58. When an operating force is applied to the brake pedal 58 in order to increase the braking force, the valve mechanism 126 shuts off the negative pressure chamber 70 and the variable pressure chamber 98 and allows the variable pressure chamber 98 and the atmosphere to communicate with each other. It becomes a state. Therefore, the negative pressure chamber 70 is in a negative pressure state, but the variable pressure chamber 98 is at atmospheric pressure. That is, a pressure difference is generated between the negative pressure chamber 70 and the variable pressure chamber 98, and the differential pressure due to the pressure difference acts in the same direction as the moving direction of the power piston 92 by the operating force. The operating force can be boosted.

  On the other hand, when the operating force applied to the brake pedal 58 is released, the valve mechanism 126 communicates the negative pressure chamber 70 and the variable pressure chamber 98 and shuts off the variable pressure chamber 98 and the atmosphere. Therefore, air flows from the variable pressure chamber 98 into the negative pressure chamber 70, and the negative pressure chamber 70 and the variable pressure chamber 98 have the same air pressure in the negative pressure state. That is, the pressure difference between the negative pressure chamber 70 and the variable pressure chamber 98 is eliminated, and the operating force is also eliminated. Therefore, the pressurizing piston 106, the power piston 92, and the like are caused by the spring force of the compression coil spring 108 and the compression coil springs 116a and 116b. The brake pedal 58 is returned to the position when it is not operated. The housing 90 of the vacuum booster 60 is provided with a negative pressure sensor 128 that detects the negative pressure in the negative pressure chamber 70.

<Eco-run control>
In the present drive system 12, as described above, the engine operation control corresponding to the operation amount that controls the operation of the engine 20 according to the operation amount of the accelerator pedal of the driver is executed, and the accelerator pedal is not operated. However, idling control is performed in order to avoid engine stoppage due to a decrease in engine speed. However, the idling control is an engine rotation maintaining control for maintaining the engine speed, and is not a control for rotating the wheel by driving the engine. Therefore, if the idling control is suppressed, unnecessary fuel consumption is reduced. It becomes possible to suppress. Therefore, in the present system 12, when a predetermined condition is satisfied, control for stopping fuel injection to the engine 20, that is, so-called eco-run control is executed instead of idling control.

  Since the eco-run control is a control for stopping the engine by stopping the fuel injection to the engine 20, it should be executed when the driver clearly expresses the intention to stop the vehicle. For this reason, as a predetermined condition for executing the eco-run control in the present system 12, the vehicle traveling speed (hereinafter may be abbreviated as “vehicle speed”) is a set threshold speed (15 km / h in the present system) or less. In addition, the brake pedal 58 or the parking brake is operated. That is, in the present system 12, even when the vehicle is running, if the driver's intention to stop the vehicle is clear, the eco-run control is executed, and the eco-run control is executed only when the vehicle is stopped. Thus, it is possible to improve the fuel consumption of the vehicle.

  Further, when the engine 20 is stopped, the power generation by the power generator 26 is stopped, and the battery 26 is not charged by the power generator 26, and the charge amount of the battery 28 may be reduced. For this reason, the fact that the amount of charge of the battery 28 is secured to some extent, specifically, that the amount of charge of the battery 28 is larger than the set threshold amount is also adopted as a predetermined condition for executing the eco-run control. .

  Further, when the engine 20 is stopped, the air in the intake manifold 76 is not sucked by the engine 20 and the engine negative pressure is reduced. That is, the absolute atmospheric pressure of the intake manifold 76 as the negative pressure source of the vacuum booster 60 approaches the atmospheric pressure. When the engine negative pressure decreases, the air in the negative pressure chamber 70 of the vacuum booster 60 is not sucked into the intake manifold 76, and the booster negative pressure in the negative pressure chamber 70 cannot be increased. For this reason, when the engine 20 is stopped, the booster negative pressure may become low. In a state where the booster negative pressure is low, it is difficult to boost the driver's operating force during brake operation, so that the booster negative pressure is higher than the set threshold pressure as a predetermined condition for executing the eco-run control. Is adopted.

The controller 34 of the engine ECU 10 includes the negative pressure sensor [P _B ] 128 that detects the booster negative pressure, the charge amount sensor [E] 130 that detects the charge amount of the battery 28, and the parking brake operation position, that is, A parking brake position sensor [PS] 132 that detects whether the parking brake device is operating or released, a vehicle speed sensor 134 [V] that detects the vehicle speed, and a liquid that detects the master cylinder pressure that is the hydraulic pressure of the master cylinder 62 A pressure sensor 136 [P _M ] is connected. The controller 34 determines whether or not the predetermined condition is satisfied based on the detected values, and when it is determined that all the conditions are satisfied, the controller 34 controls the fuel injection device 32, The fuel injection to the engine 20 is stopped. If even one of the above conditions is not satisfied, the controller 34 controls the throttle valve 30, the fuel injection device 32, and the starter motor 44 to restart the engine 20, and after restarting the engine, When the accelerator pedal is operated, the engine operation control corresponding to the operation amount is executed, and when the accelerator pedal is not operated, idling control is executed.

Further, when the depression of the brake pedal 58 is released after the depression, the negative pressure chamber 70 is communicated with the variable pressure chamber 98 that has become the atmospheric pressure as described above, so that the booster negative pressure decreases. . In the eco-run control, when the depression of the brake pedal 58 is released when the engine is stopped, the booster negative pressure is reduced along with the brake operation in a situation where the air in the negative pressure chamber 70 is not sucked. For this reason, when the eco-run control is executed with the booster negative pressure slightly exceeding the set threshold pressure and the engine is stopped, the booster negative pressure becomes lower than the set threshold pressure by a slight brake operation by the driver. May be restarted. Even if the engine is restarted by a slight brake operation after the engine is stopped, fuel consumption cannot be efficiently suppressed. Therefore, in the present system 12, with respect to the set threshold pressure of the booster negative pressure P _B, a set threshold pressure used for stopping fuel injection (hereinafter sometimes referred to as “stop booster negative pressure threshold”) P _0S , A set threshold pressure (sometimes referred to as a restart booster negative pressure threshold) P _0R used for restarting the engine is individually set, and the stop booster negative pressure threshold P _0S is used for restart. The booster negative pressure threshold P _0R is set to a larger value.

Further, the eco-run control in the present system 12 is executed even while the vehicle is traveling as described above. For this reason, the booster negative pressure threshold value P _0S for stopping is set to a value that can ensure the braking force necessary to stop the running vehicle, and the booster negative pressure is set from the set threshold value P _0S . If the value is large, the vehicle can be stopped using the boost effect of the vacuum booster 60. That is, as the stop booster negative pressure threshold P _0S is set to a larger value, a larger braking force can be secured. However, on the other hand, by setting the stop booster negative pressure threshold P _0S large value, the booster negative pressure is hardly greater than the threshold P _0S, it becomes difficult to perform the eco-run control. That is, it becomes difficult to improve fuel consumption. Therefore, in the present system 12, the vehicle stops at a threshold value P _0ST set to a value that can ensure the braking force required during normal driving (hereinafter, sometimes referred to as “normal time stop setting threshold value”). When the booster negative pressure threshold value P _0S is normally set and a large braking force is assumed to be required, the stop booster negative pressure threshold value P is set to a value _larger than the normal stop threshold value P _{0ST. 0S} is set.

Specifically, assuming that a large braking force is required when the amount of operation of the accelerator pedal is large and when the return speed of the accelerator pedal is high, the stop booster negative pressure threshold P _{0S is set} to It is set to a value _larger than the setting threshold value P _0ST . This is because when the amount of operation of the accelerator pedal is large, the vehicle speed is relatively high, and it is estimated that a large braking force is necessary to stop the vehicle in a high-speed traveling state. In addition, when the return speed of the accelerator pedal, that is, the decrease speed of the operation amount of the accelerator pedal is high, it can be estimated that the driver has released his / her foot from a state where the accelerator pedal is depressed to some extent. In many cases, after such an accelerator operation is performed, the brake pedal is suddenly depressed to suddenly stop the vehicle. That is, when the rate of decrease in the operation amount of the accelerator pedal is high, it is estimated that a large braking force is necessary for the sudden braking operation.

Specifically, when the operation amount of the accelerator pedal is less than the set threshold amount and the decrease rate of the operation amount is lower than the set threshold speed, the stop booster negative pressure threshold value P _{0S is set} to a certain specific value. Set to the stop threshold setting threshold P _0ST and the accelerator pedal operation amount exceeds the set threshold amount, or the decrease amount of the operation amount exceeds the set threshold speed, the stop booster negative The pressure threshold value P _0S is set to a value (P _0ST + α) that is α (> 0) larger than the normal-time stop setting threshold value P _0ST . By setting the stop booster negative pressure threshold P _0S in this way, it is possible to improve fuel efficiency and maintain the booster negative pressure at a high level when a large braking force is required.

<Control program>
Control of the engine 20 in the system 12 is repeatedly executed by the controller 34 of the engine ECU 10 at a set time interval ΔT ₀ while the ignition switch is in the ON state, while the engine control program shown in the flowchart of FIG. Is done. The control flow will be briefly described below with reference to the flowchart shown in the figure.

In the processing according to this program, first, in step 1 (hereinafter simply referred to as “S1”; the same applies to other steps), the accelerator pedal stroke sensor 40 detects the operation amount L of the accelerator pedal. Next, in S2, a flowchart is shown in FIG. 5 in order to set a stop booster negative pressure threshold value P _0S that is a set threshold value of the booster negative pressure P _B used for stopping the fuel injection to the engine in the eco-run control. Processing for executing the stop booster negative pressure threshold setting subroutine is executed. In this subroutine, first, in S21, the flag value set threshold increase flag F _Z is determined whether it is to 1. The flag F _Z is a flag indicating whether or not the stop booster negative pressure threshold P _0S is set to a value _larger than the normal stop setting threshold P _0ST , and the flag value of the flag F _Z is set to 1. Indicates that the stop booster negative pressure threshold P _0S is set to a value _larger than the normal stop setting threshold P _0ST , and if it is 0, the stop booster negative pressure threshold It shows that P _0S is set to the normal stop threshold value P _0ST . The initial value of the flag F _Z is 0.

If the flag value set threshold increase flag F _Z is determined to be 0, in S22, whether the operation amount L of the accelerator pedal is reduced is determined. Specifically, from the previous operation amount L _P detected by the accelerator pedal stroke sensor 40 in the last execution of the present program, whether the detected operation amount L in this program current is small it is determined. When it is determined that the operation amount L is smaller than the previous operation amount L _P , that is, when it is determined that the operation amount L of the accelerator pedal is decreasing, the decrease speed V _{L of the} operation amount is determined in S23. It is determined whether or not the set threshold speed _V0L or higher. Specifically, the decrease speed V _L is calculated according to the following equation, and it is determined whether or not the calculated decrease speed V _L is equal to or higher than the set threshold speed V _0L .
V _L = (L _P −L) / ΔT ₀
ΔT ₀ is a time set for repeatedly executing this program and is a fixed time. Therefore, even if it is determined whether or not the angle difference (L _P −L) between the previous operation amount L _P and the operation amount L is greater than or equal to the set threshold, the operation amount decrease speed V _L is equal to the set threshold speed V _0L. It is possible to determine whether or not this is the case.

If it is determined that the decrease speed V _L is equal to or higher than the set threshold speed V _0L , the stop booster negative pressure threshold P _0S is larger than the normal stop set threshold P _{0ST in S24} , that is, P _0ST. + is set to alpha, in S25, the flag value set threshold increase flag F _Z is 1. On the other hand, if it is determined that the decrease speed V _L is lower than the set threshold speed V _0L , the stop booster negative pressure threshold P _0S is set to the normal stop set threshold P _0ST in _S26 . If it is determined in S22 that the accelerator pedal operation amount L has not decreased, it is determined in S27 whether or not the accelerator pedal operation amount L is greater than the maximum accelerator operation amount _LMAX . The maximum accelerator operation amount L _MAX is the largest value among the operation amounts L detected from when the accelerator pedal is operated until it is released, and the initial value of the maximum accelerator operation amount L _MAX is set to 0. Every time the accelerator pedal is released, it is reset to zero. When the operation amount L is determined as the maximum accelerator operation amount is greater than L _MAX, in S28, the maximum accelerator operation amount L _MAX is updated to the operation amount L. Next, in S29, it is determined whether or not the maximum accelerator operation amount L _MAX is greater than or equal to the set threshold amount L ₀ . If it is determined that the maximum accelerator operation amount L _MAX is equal to or greater than the set threshold amount L ₀ , the stop booster negative pressure threshold P _0S is _greater than the normal stop set threshold P _0ST (P _{0ST) in S24.} If the maximum accelerator operation amount L _MAX is determined to be less than the set threshold amount L ₀ , the stop booster negative pressure threshold P _0S is set to the normal stop set threshold P _0ST in _S26. The

Further, when the flag value set threshold increase flag F _Z in S21 is is determined to be 1, in S30, whether the accelerator pedal is released is determined. Specifically, it is determined whether or not the accelerator pedal operation amount L is zero. If it is determined that the accelerator pedal is released, the maximum accelerator operation amount L _MAX is reset to 0 in S31, and the flag value of the accelerator release flag F _K is set to 1 in S32. The flag F _K is a flag indicating whether or not the accelerator pedal is released after the stop booster negative pressure threshold P _0S is set to a value (P _0ST + α) larger than the normal stop setting threshold P _0ST . When the flag value of the flag F _K is 1, it indicates that the accelerator pedal is released, and when it is 0, it indicates that the accelerator pedal is not released.

Further, when it is determined that the accelerator pedal is not released in S30, in S33, whether or not the flag value of the accelerator release flag F _K is 1 it is determined. When it is determined that the flag value of the accelerator release flag F _K is 1, the flag value of the setting threshold increase flag F _{Z and} the flag value of the accelerator release flag F _K are set to 0 in S34, and S22 The following processing is executed as described above. After the processes in S25, 26, and 32, or after it is determined in S33 that the flag value of the accelerator release flag F _K is set to 0, this subroutine ends.

After execution of the stop booster negative pressure threshold setting subroutine, it is determined in S3 whether or not the accelerator pedal is being operated. Specifically, it is determined whether or not the operation amount L of the accelerator pedal is not zero. If it is determined that the operation amount L is 0, that is, if it is determined that the driver is not operating the accelerator pedal and the accelerator pedal is released, the vehicle speed sensor 134 is determined in S4. Thus, the vehicle speed V is detected. Then, in S5, whether the detected vehicle speed V is lower than or equal to the set threshold speed V ₀ is determined. When it is determined that the vehicle speed V is not less than or equal to the set threshold speed V ₀ , and when it is determined in S3 that the accelerator pedal is being operated, the operation amount corresponding engine operation control is executed in S6.

Further, when the vehicle speed V is determined to be less than the set threshold speed V _0, in S7, in order to determine the fuel injection permission flag F _F is a flag indicating whether or not fuel injection to the engine 20, FIG. A process for executing the fuel injection propriety flag determination subroutine shown in the flowchart in FIG. 6 is executed. The flag F _F is the permitted fuel injection in the idling control, a flag indicating whether to stop the fuel injection in the eco-run control, if the flag value of the flag F _F is a 1, the eco-run control In order to execute, the fuel injection to the engine 20 is stopped, and when it is set to 0, the fuel injection to the engine 20 is allowed to perform the idling control. The initial value of the flag F _F is zero.

In this subroutine, first, in S41, the master cylinder pressure P _M is detected by the pressure sensor 136, in S42, the parking brake system by the parking brake position sensor 132 or in release or during operation is detected. Further, in S43, the booster negative pressure P _B is detected by the negative pressure sensor 128, and in S44, the charge amount E of the battery 28 is detected by the charge amount sensor 130. Next, in S45, it is determined whether or not the brake device 50 or the parking brake device is operating. If it is determined that the brake device 50 is operating, the charge amount E of the battery 28 is set to a set threshold amount in S46. It is determined whether or not E ₀ is exceeded. When it is determined that the charge amount E exceeds the set threshold amount E ₀ , the booster negative pressure P _B is set to the stop booster negative pressure threshold set in the stop booster negative pressure threshold setting subroutine in S47. It is determined whether or not P _0S is exceeded. If the booster negative pressure P _B is determined to be beyond the stop booster negative pressure threshold P _0S, in S48, in order to execute the eco-run control, the flag value of the fuel injection permission flag F _F is a 1 .

Further, when the booster negative pressure P _B is determined not to exceed the stop booster negative pressure threshold P _0S, at S49, determines whether or not the flag value of the fuel injection permission flag F _F is a 1 If it is determined that the flag value is 1, the booster negative pressure P _B exceeds the restart booster negative pressure threshold P _0R used for restarting the engine 20 in S50. It is determined whether or not there is. If the booster negative pressure P _B is determined to be exceeded for restarting the booster negative pressure threshold P _0R, in S48, the flag value of the fuel injection permission flag F _F is set to 1. On the other hand, when it is determined that the booster negative pressure P _B does not exceed the restart booster negative pressure threshold P _0R , when it is determined in S45 that both the brake device 50 and the parking brake device are released. , when the charge amount E is determined not to exceed the set threshold amount E ₀ in S46, if the flag value of the fuel injection permission flag F _F is determined to be zero in S49, in S51, in order to execute the idling control, the flag value of the fuel injection permission flag F _F is zero. The flag value of the fuel injection permission flag F _F is determined to be one of the values, this subroutine ends.

After execution of the fuel injection permission flag decision subroutine, in S8, the flag value of the fuel injection permission flag F _F determined in the subroutine it is determined whether or not 1. In that case the flag value of the flag F _F is determined to be 1, in S9, in order to execute the eco-run control to stop the fuel injection to the engine 20. Further, when the flag value of the flag F _F is determined to be 0, in S10, if the engine 20 is determined whether it is stopped, is determined to be stopped, If it is determined in S11 that the engine 20 is restarted and is not stopped, engine rotation maintaining control, that is, idling control is executed in S12. After execution of the above controls or restart of the engine 20, one execution of this program is completed.

<Functional configuration of controller>
The controller 34 of the engine ECU 10 that executes the engine control program can be considered to have a functional configuration as shown in FIG. 1 in view of its execution processing. As can be seen from the figure, the controller 34 uses the engine operation control unit 150 as the functional unit that executes the process of S6, that is, the functional unit that controls the operation of the engine according to the operation amount of the accelerator pedal. Even when the accelerator is not operated, the function unit to be executed, that is, the non-operation engine rotation maintaining unit 152 as the function unit for maintaining the engine rotation, the function unit for executing the process of S9, Even when the engine rotation should be maintained by the non-operating engine rotation maintaining unit 152, as a functional unit that stops fuel injection to the engine in order to perform eco-run control when a predetermined condition is satisfied the fuel injection stop 154, a functional portion to execute the processing in S7, that is, to set the booster negative pressure threshold P _0S for performing eco-run control As a functional unit, the booster negative pressure threshold setting unit 156 includes, respectively. Further, the booster negative pressure threshold value setting unit 156 is a function unit that executes the processes of S27 to S29, that is, a function unit that sets the booster negative pressure threshold value P _0S depending on the operation amount of the accelerator pedal. The setting unit 158 is a functional unit that executes the processes of S22 and S23, that is, a functional unit that sets the booster negative pressure threshold P _0S depending on the change speed of the operation amount of the accelerator pedal, in other words, the operation speed of the accelerator pedal. Each of them has an accelerator operation speed dependency setting unit 160.

  10: Engine electronic control unit (engine control device) 20: Engine 58: Brake pedal (brake operation member) 60: Vacuum booster 70: Negative pressure chamber 82: Intake section 150: Engine operation control section 154: Fuel injection stop section 156: Booster negative pressure threshold setting section

Claims (3)

An engine control device for controlling an engine having an intake portion connected to a negative pressure chamber of a vacuum booster that boosts an operation force applied to a brake operation member,
An engine operation control unit that controls the operation of the engine by controlling the fuel injection amount to the engine according to the operation amount of the accelerator operation member;
Even if the vehicle is running, the accelerator operating member is not operated, and the booster negative pressure, which is the negative pressure of the negative pressure chamber, is higher than a set threshold pressure. A fuel injection stop section for stopping fuel injection into the engine;
An engine control device comprising: a booster negative pressure threshold setting unit that sets the set threshold pressure of the booster negative pressure based on at least one of an operation amount of the accelerator operation member and a change speed of the operation amount. The booster negative pressure threshold setting unit is
While setting the set threshold pressure based on at least the rate of decrease of the operation amount of the accelerator operation member,
The set threshold pressure is set to a specific value when the decrease speed is lower than the set threshold speed, and is set to a value larger than the specific value when the decrease speed is equal to or higher than the set threshold speed. The engine control device according to claim 1 configured as described above. The booster negative pressure threshold setting unit,
While setting the set threshold pressure based on at least the operation amount of the accelerator operation member,
The set threshold pressure is set to a specific value when the operation amount of the accelerator operating member is smaller than the set threshold amount, and the specified value is set when the operation amount of the accelerator operating member is equal to or larger than the set threshold amount. The engine control device according to claim 1 or 2, wherein the engine control device is configured to be set to a value larger than the value of.

Images