JP7455489B2 - Vehicle control device - Google Patents

Description

The present invention relates to a control device for controlling a vehicle equipped with an internal combustion engine as a power source.

Conventionally, in order to reduce the operating force required when braking a vehicle, that is, the force required to press the brake pedal, a vacuum system that uses the negative intake pressure generated downstream of the throttle valve in the intake passage of an internal combustion engine to boost the force applied to the brake pedal. Vacuum type brake boosters are widely used. This type of brake booster has a constant pressure chamber that stores intake negative pressure and a variable pressure chamber that introduces atmospheric pressure. When the driver is not pressing the brake pedal, the constant pressure chamber and variable pressure chamber communicate with each other, and atmospheric pressure is not introduced into the variable pressure chamber. When the driver depresses the brake pedal, the constant pressure chamber and variable pressure chamber are cut off, atmospheric pressure is introduced into the variable pressure chamber, and a boosting effect is performed due to the pressure difference between the constant pressure chamber and the variable pressure chamber (for example, (See patent documents below).

Japanese Patent Application Publication No. 2020-033959

The negative pressure stored in the constant pressure chamber of the brake booster is consumed when the vehicle driver depresses the brake pedal to activate the foot brake device. Therefore, it is required to replenish the constant pressure chamber of the brake booster with negative pressure in a timely manner.

Basically, the intake negative pressure generated downstream of the throttle valve in the intake passage of the internal combustion engine is supplied to the brake booster (in short, air is sucked out from the constant pressure chamber of the brake booster into the intake passage). However, when the throttle valve is opened wide, such as during high-load operation, sufficient negative intake pressure cannot be supplied to the brake booster.

Therefore, it is conceivable to attach an electric vacuum pump to the brake booster and operate the electric pump to supply negative pressure to the brake booster (the electric pump sucks air out of the constant pressure chamber of the brake booster). When the magnitude of the negative pressure stored in the brake booster falls below a certain value (when the pressure in the constant pressure chamber becomes higher than this value), the electric pump is activated to supply negative pressure. Thereafter, when the pressure in the constant pressure chamber is restored to a certain value stored in the brake booster or higher (when the pressure in the constant pressure chamber becomes lower than the value), the electric pump is stopped.

When the current output voltage (terminal voltage) of an on-vehicle power source (for example, a power storage device such as a lead battery, lithium ion battery, or nickel metal hydride battery) is low, the voltage or power applied to the electric pump decreases. As a result, even if an attempt is made to start a stopped electric pump, the electric pump cannot be started successfully, and the electric pump may malfunction.

In order to prevent such malfunctions, a threshold is set for the voltage or power supplied to the electric pump from the in-vehicle power supply, and the condition is that the voltage or power that can currently be supplied to the electric pump exceeds the threshold. It is conceivable to allow the operation of electric pumps and otherwise prohibit the operation of electric pumps.

However, if the above-mentioned threshold value is uniformly set, even though the electric pump may actually be operated, the pump remains stopped and negative pressure cannot be supplied to the brake booster, resulting in an unreasonable situation.

The amount of voltage or power that must be applied to the pump motor to start an electric pump depends on the amount of work required to start the pump mechanism. Assuming that a general piston pump is used as the vacuum pump, as shown in Figure 5, the larger the negative pressure currently stored in the brake booster (the lower the pressure inside the constant pressure chamber), the more required power supply voltage S. becomes larger. Conversely, the smaller the negative pressure stored in the brake booster (the higher the pressure inside the constant pressure chamber), the smaller the power supply voltage S can be.

Therefore, if the threshold value T is always a constant value, the pump may not be operated in the hatched area in FIG. 5, even though the pump could normally be operated. Currently, because the negative pressure inside the brake booster is low, the pump must be operated to supply the brake booster, but at that time, the pump is prohibited from operating.

The present invention, which was made with attention to the above points, aims to avoid malfunction of the electric vacuum pump while increasing its operation opportunities, and to enable the pump to supply negative pressure to the brake booster at any time. shall be.

The present invention controls a vehicle equipped with a brake booster that uses negative pressure to boost the brake pedal force, and an electric pump that supplies negative pressure to the brake booster. When the voltage or power that can be supplied exceeds a threshold, the electric pump is allowed to operate, and when it is below, the electric pump is prohibited from operating. A vehicle control device has been constructed that raises and lowers the vehicle according to engine speed or vehicle speed. If the electric pump is a pump in which the voltage or electric power that should be applied to the pump motor to start the electric pump increases as the negative pressure in the brake booster increases, the current negative pressure in the brake booster increases. The higher the pressure, the higher the threshold value is set, and the higher the current engine speed or vehicle speed, the higher the threshold value is set. Alternatively, if the electric pump is a pump in which the voltage or electric power that should be applied to the pump motor to start the electric pump decreases as the negative pressure inside the brake booster increases, the current The lower the negative pressure, the higher the threshold value is set, and/or the lower the current engine speed or vehicle speed, the higher the threshold value is set.

According to the present invention, it is possible to increase the chances of operation of the electric vacuum pump while avoiding malfunction of the electric vacuum pump, and to supply negative pressure to the brake booster from the pump at any time.

1 is a diagram showing the configuration of a vehicle internal combustion engine and a control device in an embodiment of the present invention. FIG. 3 is a flow diagram showing an example of a procedure of processing executed by the control device according to the embodiment according to a program. FIG. 3 is a diagram illustrating control by the control device of the embodiment. FIG. 3 is a diagram illustrating control by the control device of the embodiment. FIG. 2 is a diagram illustrating the problem to be solved by the present invention.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overview of a vehicle internal combustion engine 100 in this embodiment. Internal combustion engine 100 supplies driving force for running to an axle 103 and drive wheels via a drive system of the vehicle. The internal combustion engine 100 is, for example, a spark ignition four-stroke reciprocating engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). Upstream of the intake valve of each cylinder 1 and near the intake port connected to each cylinder 1, an injector 11 is provided that injects fuel toward the intake port. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 causes a spark discharge between a center electrode and a ground electrode upon application of an induced voltage generated in an ignition coil. The ignition coil is integrally built into the coil case together with the igniter, which is a semiconductor switching element.

The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream.

The exhaust passage 4 for discharging exhaust gas guides exhaust gas generated by burning fuel in the cylinders 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and a three-way catalyst 41 for exhaust purification are arranged on the exhaust passage 4.

The exhaust gas recirculation device 2 includes an external EGR passage 21 that communicates the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21 that opens and closes the EGR passage 21. The EGR valve 23 that controls the flow rate of EGR gas flowing through the EGR valve 21 is an element. The entrance of the EGR passage 21 is connected to a predetermined location downstream of the catalyst 41 in the exhaust passage 4 . The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

The vehicle of this embodiment is equipped with a brake booster 5 for reducing the operating force required during braking with the foot brake, that is, the depression force on the brake pedal. The brake booster 5 introduces negative intake pressure from the downstream side of the throttle valve 32 in the intake passage 3 of the internal combustion engine 100, particularly from the surge tank 33 or the intake manifold 34, and uses the negative pressure to double the depression force on the brake pedal. It is widely known in this field. The brake booster 5 has a constant pressure chamber that stores negative pressure and a variable pressure chamber that receives atmospheric pressure, and the constant pressure chamber is connected to the intake passage 3 via a negative pressure pipe 51. The negative pressure pipe 51 guides the intake negative pressure downstream of the throttle valve 32 to the constant pressure chamber. A check valve 52 is provided on the negative pressure conduit 51 to keep the negative pressure within the constant pressure chamber and to prevent positive pressure from being applied to the constant pressure chamber.

When the brake pedal is not operated by the driver, the constant pressure chamber and variable pressure chamber communicate with each other, and the variable pressure chamber is isolated from atmospheric pressure. When the brake pedal is operated, the constant pressure chamber and the variable pressure chamber are cut off, and the atmosphere is introduced into the variable pressure chamber. As a result, the pressure difference between the constant pressure chamber and the variable pressure chamber becomes a control pressure that doubles the force applied to the brake pedal. The brake pedal force amplified by the brake booster is converted into hydraulic pressure in the master cylinder. The master cylinder pressure output by the master cylinder, that is, the pressure of the brake fluid discharged by the master cylinder, is transmitted to a foot brake device such as a brake caliper or wheel cylinder via a hydraulic circuit, and is used by the brake device to brake the vehicle. It will be done.

An electric vacuum pump 6 is attached to the brake booster 5. The electric pump 6 is connected to the constant pressure chamber of the brake booster 5 via a negative pressure conduit 61, and supplies negative pressure to the brake booster 5 by sucking air from the constant pressure chamber through the negative pressure conduit 61. A check valve 62 is provided on the negative pressure line 61 to keep the negative pressure within the constant pressure chamber and prevent positive pressure from being applied to the constant pressure chamber. The electric pump 6 operates by receiving power from an on-vehicle power source, for example, a power storage device such as a lead battery, a lithium ion battery, or a nickel metal hydride battery.

An ECU (Electronic Control Unit) 0, which is a control device for a vehicle in this embodiment, is a microcomputer system that includes a processor, a memory, an input interface, an output interface, and the like. The ECU0 may include a plurality of ECUs or controllers connected to each other so as to be communicable via a telecommunication line such as a CAN (Controller Area Network).

The input interface of the ECU 0 receives a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crankshaft of the internal combustion engine 100 and the engine speed, an accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal operated by the driver or the opening of the throttle valve 32 as the accelerator opening (in other words, the required engine torque or engine load rate), an intake passage 3 connected to the cylinder 1 of the internal combustion engine 100 (downstream of the throttle valve 32, particularly the surge tank 33 or the intake manifold 34), and a gasoline intake port 35 connected to the intake port 36. The input signals include an intake air temperature/intake pressure signal d output from a temperature/pressure sensor that detects the intake air temperature and intake pressure in the intake casing 34, a cooling water temperature signal e output from a water temperature sensor that detects the cooling water temperature of the internal combustion engine 100, a brake depression amount signal f output from a sensor that detects the depression amount of the brake pedal operated by the driver or the master cylinder pressure, a negative pressure signal g output from a negative pressure sensor that detects the negative pressure stored in the constant pressure chamber of the brake booster 5, and a battery SOC (State of Charge) signal h output from a sensor (particularly a battery current and/or battery voltage sensor) that detects the amount of charge stored in the on-board power storage device.

From the output interface of the ECU 0, an ignition signal i is sent to the igniter of the spark plug 12, a fuel injection signal j is sent to the injector 11, an opening operation signal k is sent to the throttle valve 32, and an opening operation signal is sent to the EGR valve 23. It outputs a signal l, a control signal n, etc. to the electric vacuum pump 6.

The processor of ECU0 interprets and executes programs stored in memory, calculates operating parameters, and controls the operation of internal combustion engine 100. ECU0 acquires various information a, b, c, d, e, f, g, h necessary for control via the input interface, learns the engine rotation speed, and detects the air (fresh air) taken into cylinder 1. ), and estimate the required fuel injection amount and fuel injection timing (including the number of fuel injections for one combustion) commensurate with the intake air amount (achieving the stoichiometric air-fuel ratio or a target air-fuel ratio close to it). , various operating parameters such as fuel injection pressure, ignition timing (including the number of ignitions for one combustion), required EGR rate (or EGR gas amount, EGR gas partial pressure), whether or not to operate the electric pump 6, etc. decide. ECU0 applies various control signals i, j, k, l, n corresponding to operating parameters via an output interface.

The ECU0 refers to the negative pressure signal g and learns the magnitude of the negative pressure currently stored in the brake booster 5. As a general rule, when the magnitude of the negative pressure falls below a certain value (the pressure in the constant pressure chamber becomes higher than the value), the electric pump 6, which had been stopped, is started and activated. , the electric pump 6 supplies negative pressure to the brake booster 5. Thereafter, when the negative pressure stored in the brake booster 5 recovers to exceed a certain value (the pressure in the constant pressure chamber becomes lower than the value), the electric pump 6 is stopped.

However, when the negative pressure in the brake booster 5 decreases, the electric pump 6 is not always activated. If the amount of charge stored in the on-vehicle power storage device decreases and the voltage or power that can be applied from the power storage device to the electric pump 6 decreases, the electric pump 6 cannot be started properly and the electric pump 6 may malfunction. There is a risk of falling.

Therefore, as shown in FIG. 2, the ECU 0 of this embodiment sets a variable threshold value according to the current negative pressure in the brake booster 5 and/or the vehicle speed (step S1), and also sets a variable threshold value according to the current negative pressure in the brake booster 5 and/or the vehicle speed (step S1), and also If the voltage or power that can be supplied to the brake booster 6 exceeds the threshold value (step S2), the operation of the electric pump 6 is permitted (step S3); otherwise, even if the negative pressure in the brake booster 5 is reduced, the electric pump 6 is operated. Operation of the pump is prohibited (step S4).

The threshold value T to be compared with the current power supply capacity of the power storage device, which is set in step S1, depends on the type and characteristics of the pump 6. Assuming that a general piston pump or the like is used as the vacuum pump 6, as shown in FIG. Or the electric power S increases. Therefore, the larger the current negative pressure in the brake booster 5 is, the higher the threshold value T is set, and/or the higher the current engine speed or vehicle speed is, the higher the threshold value T is set. The reason for changing the threshold value T according to the engine speed or vehicle speed is that the higher it is, the larger the intake negative pressure generated in the intake passage 3 of the internal combustion engine 100 tends to be (the intake pressure downstream of the throttle valve 32 becomes lower). (Of course, this depends on the opening degree of the throttle valve 32 at that time).

If another type of pump is used as the vacuum pump 6, as shown in FIG. may become smaller. For such a pump 6, the lower the current negative pressure in the brake booster 5, or the lower the current engine speed or vehicle speed, the higher the threshold value T is set.

In step S2, the magnitude of the voltage or power that can currently be supplied from the power storage device to the electric pump 6 can be learned with reference to the battery SOC signal h (which may be the terminal voltage of the battery). Referring to the example shown in FIG. 3, if the current output voltage of the power storage device is V2, the output voltage V2 always exceeds the threshold T, and starting the electric pump 6 is permitted. On the other hand, if the output voltage of the power storage device has decreased to V1, the current negative pressure in the brake booster 5 is lower than P (or the engine speed or vehicle speed is lower than the corresponding value). In this case, the output voltage V1 exceeds the threshold value T, and starting the electric pump 6 is permitted (step S3). On the other hand, if the negative pressure in the brake booster 5 is greater than P (or the engine speed or vehicle speed is higher than the corresponding value), the output voltage V1 is less than the threshold T, and the electric pump 6 is activated. Activation is prohibited (step S4).

Referring to the example shown in FIG. 4, only when the negative pressure in the brake booster 5 is smaller than P (or the engine speed or vehicle speed is lower than the corresponding value), the power storage device outputs When the voltage V1 falls below the threshold T, starting the electric pump 6 is prohibited (step S4).

In step S4, if the operation of the electric pump 6 is to be prohibited, the opening degree of the throttle valve 32 is reduced from the normal opening degree corresponding to the amount of depression of the accelerator pedal, and a larger intake air is generated in the intake passage 3. A negative pressure will be generated and the intake negative pressure will be supplied to the brake booster 5.

According to this embodiment, it is possible to increase the chances of operation of the electric vacuum pump 6 while avoiding malfunction of the electric vacuum pump 6, and to supply negative pressure to the brake booster 5 by the pump 6 at any time.

In the example shown in FIG. 3, when the negative pressure inside the brake booster 5 is reduced (the pressure inside the constant pressure chamber is close to atmospheric pressure), it is allowed to operate the electric pump 6, and the brake booster 5 is reliably operated. This makes it possible to secure the necessary negative pressure, which contributes to improving the drivability of the vehicle. When the negative pressure within the brake booster 5 is greater than P, operation of the electric pump 6 is prohibited, but the negative pressure necessary for the brake booster 5 has already been secured in the first place. Furthermore, if the current engine speed or vehicle speed is high, the intake negative pressure in the intake passage 3 is increasing, or the generator (alternator or motor generator) attached to the internal combustion engine 100 can generate electricity. The probability is high that there will be no problem with braking the vehicle.

Note that the present invention is not limited to the embodiments detailed above. For example, the intake negative pressure downstream of the throttle valve 32 in the intake passage 3, in other words, the negative pressure inside the brake booster 5, is affected by the current temperature of the internal combustion engine 100. In view of this, it is also conceivable to correct the threshold value T to be compared with the current power supply capacity of the power storage device in accordance with the current cooling water temperature of the internal combustion engine 100. The higher the cooling water temperature, the smaller the intake negative pressure (the higher the intake pressure), and the more difficult it becomes to supply the intake negative pressure to the brake booster 5, so the threshold T is lowered accordingly to increase the opportunity for the electric pump 6 to operate. That's one idea.

In addition, the specific configuration of each part, processing procedure, etc. can be variously modified without departing from the spirit of the present invention.

0...Control unit (ECU)
100...Internal combustion engine 3...Intake passage 32...Throttle valve 5...Brake booster 6...Electric pump d...Intake pressure signal g...Brake booster negative pressure signal h...Battery SOC signal n...Electric pump control signal

Claims (1)

It controls a vehicle equipped with a brake booster that uses negative pressure to boost the brake pedal force, and an electric pump that supplies negative pressure to the brake booster.
If the voltage or power that can currently be supplied to the electric pump from the in-vehicle power source exceeds a threshold, the electric pump will be allowed to operate, and if it falls below, the electric pump will be prohibited from operating.
If the electric pump is such that the larger the negative pressure in the brake booster, the greater the voltage or power that should be applied to the pump motor to start the electric pump, the current negative pressure in the brake booster is The larger the threshold value is, the higher the threshold value is set, and the higher the current engine speed or vehicle speed is, the higher the threshold value is set.
or,
If the electric pump is such that the larger the negative pressure in the brake booster, the smaller the voltage or electric power that should be applied to the pump motor to start the electric pump, the current negative pressure in the brake booster is A vehicle control device that sets the threshold value higher as the threshold value is smaller, or sets the threshold value higher as the current engine rotation speed or vehicle speed is lower .

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