JP7418914B2 - Vehicle control device - Google Patents

Description

The present invention relates to a control device for controlling a vehicle in which a torque converter and an automatic transmission are interposed between an internal combustion engine and drive wheels.

As a drive system transmission interposed between an internal combustion engine mounted on a vehicle as a power source and drive wheels of the vehicle, a transmission equipped with a torque converter and a belt-type continuously variable transmission is known. (For example, see the following patent documents).

In torque converters that use fluid, when the load increases, the transmission efficiency decreases due to slippage. Therefore, when the vehicle speed increases beyond a certain level, it is customary to engage the input side and the output side with a lockup clutch to directly connect the input side and the output side to perform a lockup.

JP 2019-135383 Publication

Especially on snowy roads, icy roads, or other roads with a low coefficient of friction, when the driver of the vehicle tries to brake the vehicle suddenly by pressing down hard on the foot brake pedal, if the lock-up clutch is engaged, the wheels may As the rotation is locked, the rotation of the crankshaft, which is the output shaft of the internal combustion engine, is also locked, which may cause the engine to stall.

A vehicle equipped with a VSC (Vehicle Stability Control) is equipped with a sensor that detects the master cylinder pressure of a foot brake device. Further, some vehicles are equipped with a stroke sensor that detects the amount of depression of the brake pedal by the driver. When sudden braking is detected through these sensors, the lock-up of the torque converter caused by the lock-up clutch is released, thereby preventing the rotation of the internal combustion engine's crankshaft from locking up and eventually stalling the engine. can do.

On the other hand, vehicles equipped with a conventional ABS (Antilock Brake System) but not VSC are not equipped with a master cylinder pressure sensor or a brake pedal stroke sensor. Therefore, the fact that sudden braking is performed cannot be detected through these sensors. Therefore, in order to reliably avoid engine stall, it is necessary to release the lock-up of the torque converter at a relatively high vehicle speed, resulting in a corresponding disadvantage in fuel efficiency.

The present invention, which was developed with attention to the above problems, aims to prevent engine stalling during sudden braking without relying on a master cylinder pressure sensor or a brake pedal stroke sensor.

In order to solve the above-mentioned problems, in the present invention, a torque converter and a belt type continuously variable transmission are interposed between the output shaft of an internal combustion engine mounted on a vehicle and the drive wheels of the vehicle, and a master cylinder pressure sensor and It controls a vehicle that is not equipped with a brake pedal stroke sensor , and the absolute value increases as the current engine speed increases, or the absolute value increases as the current vehicle speed increases, or A threshold value is set such that the higher the gear ratio of current belt-type continuously variable transmissions, the greater the absolute value. The condition is that the amount of decrease in the instantaneous value of the engine rotation speed detected each time the shaft rotates by a predetermined angle exceeds the threshold value set according to the current engine rotation speed, vehicle speed, or gear ratio of the belt type continuously variable transmission. The vehicle control device releases the lock-up of the torque converter caused by the lock-up clutch , and if a fuel cut is being executed at the time of releasing the lock-up, ends the fuel cut and restarts fuel injection and combustion. was configured.

Furthermore, in the present invention, a torque converter and a belt-type continuously variable transmission are interposed between the output shaft of an internal combustion engine mounted on a vehicle and the drive wheels of the vehicle , and a master cylinder pressure sensor and a brake pedal stroke sensor are provided. This system controls vehicles that are not equipped with this system, and the condition is that it detects that the brake pedal is depressed by the vehicle driver, and that the absolute value of the decrease in vehicle speed per unit time exceeds a threshold. , releases the lock-up of the torque converter caused by the lock-up clutch , and if a fuel cut is being executed at the time of releasing the lock-up, the control device of the vehicle terminates the fuel cut and restarts fuel injection and combustion. Configured.

According to the present invention, engine stall during sudden braking can be prevented without relying on a master cylinder pressure sensor or a brake pedal stroke sensor.

1 is a diagram showing a schematic configuration of a vehicle internal combustion engine and a control device according to a first embodiment of the present invention. The figure which shows the structure of the drive system of the vehicle in the same embodiment. 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. 4 is a timing diagram illustrating a pattern of fluctuations when the engine speed decreases. FIG. 3 is a diagram showing the relationship between a vehicle speed, a gear ratio of an automatic transmission, and an engine speed, and a threshold value with which the amount of decrease in the instantaneous value of the engine speed is compared. FIG. 7 is a flowchart showing an example of a procedure of processing executed by a control device according to a second embodiment of the present invention according to a program. FIG. 3 is a timing diagram showing a pattern of control by the control device of the embodiment.

<First Embodiment> 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 gasoline engine, and includes a plurality of cylinders 1 (typically three or four cylinders, 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 element includes an EGR valve 23 that controls the flow rate of EGR gas flowing through the passage 21. 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, specifically, to a surge tank 33.

FIG. 2 shows the transmission of the drive system included in the vehicle of this embodiment. This transmission includes a torque converter 7 and automatic transmissions 8 and 9. In this embodiment, as components of the automatic transmissions 8 and 9, a forward/reverse switching device 8 including a planetary gear mechanism and a belt type CVT 9 are employed.

The engine torque output by the internal combustion engine 100 is input from the crankshaft, which is the output shaft of the internal combustion engine 100, to the pump impeller 71 on the input side of the torque converter 7, and is transmitted to the turbine runner 72 on the output side. The rotation of the turbine runner 72 is transmitted to the drive shaft 94 of the CVT 9 via the forward/reverse switching device 8, and rotates the driven shaft 95 through a speed change in the CVT 9. Rotation of driven shaft 95 is transmitted to output gear 101 . The output gear 101 meshes with a ring gear 102 of a differential device, and rotates an axle (drive shaft) 103 and a drive wheel attached to the axle 103 via the differential device.

Torque converter 7 includes a lockup mechanism. The lock-up mechanism includes a lock-up clutch 73 that engages the input side and output side of the torque converter 7 so that they cannot rotate relative to each other, and a lock that controls hydraulic pressure (hydraulic pressure) for switching and driving the lock-up clutch 73. and an up solenoid valve (not shown).

In a vehicle equipped with the CVT 9, the torque converter 7 is almost constantly locked up when the vehicle speed is higher than a certain level. When the vehicle speed becomes lower than that, the lock-up of the torque converter 7 is released. During lockup, the speed ratio, which is the ratio of the output side rotation speed to the input side rotation speed of the torque converter 7, becomes 1. On the other hand, during non-lockup, the speed ratio of the torque converter 7 becomes smaller or larger than 1 depending on the driving state.

The forward/reverse switching device 8 has a sun gear 81 communicating with the turbine runner 72 and a ring gear 82 communicating with the drive shaft 94 . A forward brake 84, which is a hydraulic clutch that can be switched on and off, is interposed between the planetary carrier 83 that supports the planetary gear 831 and the transmission case. Further, a reverse clutch 85, which is a hydraulic clutch that can be switched on and off, is also interposed between the planetary carrier 83 and the sun gear 81 (or the output side of the torque converter 7).

In the D range of the driving ranges, the forward brake 84 is engaged and the reverse clutch 85 is disengaged. As a result, the rotation of the output shaft of the torque converter 7 is reversed, decelerated, and transmitted to the drive shaft 94, resulting in forward travel. On the other hand, in the R range, the reverse clutch 85 is engaged and the forward brake 84 is disengaged. As a result, the sun gear 81 and the planetary carrier 83 rotate integrally, and the output shaft of the torque converter 7 and the drive shaft 94 are directly connected, resulting in reverse travel.

In the N range of the non-driving ranges, both the forward brake 84 and reverse clutch 85 are disconnected. In the P range, the axle 103 is mechanically locked so that it does not move.

The CVT 9 is known in this field, and includes a drive pulley 91 supported non-rotatably on a drive shaft 94, and a driven pulley 92 non-rotatably supported on a driven shaft 95 disposed parallel to the drive shaft 94. and a belt 93 wound around a drive pulley 91 and a driven pulley 92. Due to the friction between both pulleys 91 and 92 and the belt 93, engine torque input to the drive shaft 94 is transferred to the driven shaft 95 and further. The power is transmitted to the axle 103.

The drive pulley 91 has a fixed sheave 911 fixed to the drive shaft 94 and a movable sheave 912 arranged opposite to the fixed sheave 911 so as to sandwich the belt 93 therebetween. The movable sheave 912 is supported on the drive shaft 94 via a roller spline so that it can be displaced in its axial direction and cannot rotate relative to it. Behind the movable sheave 912 and on the opposite side from the fixed sheave 911, a cylinder fixed to the drive shaft 94 is provided, and a hydraulic chamber 913 is formed between the cylinder and the movable sheave 912.

The driven pulley 91 has a fixed sheave 921 fixed to the driven shaft 95 and a movable sheave 922 arranged opposite to the fixed sheave 921 so as to sandwich the belt 93 therebetween. The movable sheave 922 is supported on the driven shaft 95 via a roller spline so that it can be displaced in its axial direction and cannot rotate relative to it. Behind the movable sheave 922 and on the opposite side from the fixed sheave 921, a cylinder fixed to the driven shaft 95 is provided, and a hydraulic chamber 923 is formed between the cylinder and the movable sheave 922.

In the belt type CVT 9, the hydraulic pressure (hydraulic pressure) supplied to each hydraulic pressure chamber 913, 923 of the driving pulley 91 and driven pulley 92 is controlled, and the width of the groove sandwiching the belt 93 in each pulley 91, 92 is changed. By doing so, the pulley ratio between the driving pulley 91 and the driven pulley 92, in other words, the gear ratio realized by the CVT 9 is continuously and steplessly changed. When the pulley ratio is reduced, the working hydraulic pressure supplied to the hydraulic pressure chamber 913 of the driving pulley 91 is relatively increased, and the working hydraulic pressure supplied to the hydraulic pressure chamber 923 of the driven pulley 92 is relatively reduced. be done. As a result, the movable sheave 912 of the drive pulley 91 moves toward the fixed sheave 911, and the distance between the fixed sheave 911 and the movable sheave 912, that is, the groove width becomes smaller. Accordingly, the winding diameter of the belt 93 around the drive pulley 91 increases, and the distance between the fixed sheave 921 and the movable sheave 922 of the driven pulley 92, that is, the groove width increases. As a result, the pulley ratio between the driving pulley 91 and the driven pulley 92 becomes small.

Conversely, when the pulley ratio is increased, the hydraulic pressure supplied to the hydraulic pressure chamber 913 of the driving pulley 91 is relatively reduced, and the working hydraulic pressure supplied to the hydraulic pressure chamber 923 of the driven pulley 92 is relatively reduced. will be increased to As a result, the thrust of the driven pulley 92 with respect to the belt 93 becomes larger than the thrust of the driving pulley 91 with respect to the belt 93, the distance between the fixed sheave 921 and the movable sheave 922 of the driven pulley 92 becomes smaller, and the distance between the fixed sheave 911 and the movable sheave 912 becomes larger. As a result, the pulley ratio between the driving pulley 91 and the driven pulley 92 increases.

The hydraulic pump (or oil pump, not shown) that discharges the hydraulic fluid to be supplied to the hydraulic servos 913 and 923 of the CVT 9 is a known hydraulic pump that operates by receiving engine torque from the crankshaft of the internal combustion engine 100. It is mechanical (non-electric). Generally, the hydraulic fluid for the CVT 9 is the same as the fluid used for the torque converter 7.

The thrust forces of the drive pulley 91 and the driven pulley 92 need to be large enough to prevent slippage between the pulleys 91, 92 and the belt 93. Therefore, the hydraulic pressure to be supplied to the hydraulic pressure chambers 913 and 923 of the pulleys 91 and 92 is increased or decreased so that a thrust corresponding to the magnitude of the engine torque input to the drive shaft 94 is obtained. The hydraulic pressure to be supplied to the hydraulic pressure chambers 913 and 923 is adjusted through the operation of a speed change control valve (not shown), that is, a solenoid valve that is a flow control valve.

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 (or the surge tank 33), and uses the negative pressure to boost the force applied to the brake pedal. , which 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 6. The master cylinder pressure output by the master cylinder 6, that is, the pressure of the brake fluid discharged by the master cylinder 6, is transmitted to a brake device such as a brake caliper or a wheel cylinder via a hydraulic circuit, and the brake device brakes the vehicle. used for.

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 is a plurality of ECUs or controllers connected to each other so as to be able to communicate with each other via a telecommunication line such as a CAN (Controller Area Network). This includes a general ECU that controls the internal combustion engine 100 and the drive systems 7, 8, and 9, an ABS-ECU that controls the brake system, and the like.

The input interface of the ECU 0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed, and a crank angle signal output from a crank angle sensor that detects the rotation angle and engine speed of the crankshaft of the internal combustion engine 100. b, 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 (so to speak, required engine torque or engine load rate); An intake temperature/intake pressure signal d output from a temperature/pressure sensor that detects the intake temperature and intake pressure in the surge tank 33 of the intake passage 3 or the intake manifold 34, and a shift lever (or selector lever) operated by the driver. a shift position signal e outputted from a shift position switch that detects the position of the internal combustion engine 100; A cooling water temperature signal g outputted from a water temperature sensor that detects the cooling water temperature indicating the temperature, a turbine rotation speed signal h outputted from a rotation sensor detecting the rotation speed of the turbine 72 of the torque converter 7, etc. are input.

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. A signal l, an opening operation signal t for the lockup solenoid valve for switching on and off of the lockup clutch 73, an opening operation signal u for the solenoid valve for switching on and off of the forward brake 84 or reverse clutch 85, It outputs a gear ratio control signal v etc. to the CVT 9.

The processor of the ECU 0 interprets and executes programs stored in the memory in advance, calculates operating parameters, and controls the internal combustion engine 100, the drive systems 7, 8, 9, and the brake device. ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operational control of internal combustion engine 100 via an input interface, and determines the amount of intake air to be filled into cylinder 1 (or required fuel injection amount, fuel injection timing, spark ignition timing, required EGR rate (or EGR gas amount), whether to lock up the torque converter 7, the gear ratio of the CVT 9, and the pulley 91, Various operating parameters such as the squeezing force of the belt 93 by the belt 92 are determined. ECU0 applies various control signals i, j, k, l, t, u, v corresponding to operating parameters via an output interface.

Further, the ECU 0 executes a fuel cut in which fuel injection from the injector 11 to each cylinder 1 is temporarily stopped when a predetermined fuel cut condition is satisfied. In ECU0, the fuel cut condition is satisfied when the accelerator pedal depression amount is at least below a threshold value of 0 or close to 0 (the accelerator pedal is not depressed) and the engine speed is equal to or higher than the fuel cut permission rotation speed. judge it as something.

After the start of the fuel cut, when a predetermined fuel cut end condition is satisfied, the fuel cut is ended and fuel injection and ignition combustion are restarted. ECU0 indicates that the amount of accelerator pedal depression has exceeded a threshold value (the accelerator pedal has been depressed), the engine speed has fallen below the fuel cut recovery speed, or a sudden braking event (described later) has occurred. If either of these conditions is met, it is determined that the fuel cut termination condition is satisfied.

For example, when the driver of a vehicle attempts to suddenly brake the vehicle by strongly depressing the brake pedal on a snowy road, icy road, or other road surface with a low coefficient of friction, the lock-up clutch 73 of the torque converter 7 may be engaged. The rotation of the wheels is locked by the brake device, and accordingly, the rotation of the crankshaft of the internal combustion engine 100 is also locked, creating a risk that the engine stalls.

In order to prevent such an engine stall, the ECU0 of this embodiment detects, via a stop lamp switch, that the brake pedal is depressed by the driver of the vehicle, as shown in FIG. 3 (step S1). , and the amount of decrease in the instantaneous value of the engine rotation speed detected each time the crankshaft of the internal combustion engine 100 rotates by a predetermined angle exceeds a threshold (step S2), determining that a sudden braking event has occurred; The lock-up clutch 73 of the torque converter 7 is disengaged (step S3).

Although the stop lamp switch can detect whether or not the driver is currently pressing the brake pedal, it cannot detect how strongly the driver is pressing the brake pedal. Therefore, in the present embodiment, a sign of sudden braking that will lock the rotation of the wheels is detected by referring to the transition of the instantaneous value of the engine speed.

FIG. 4 shows an example of a pattern of fluctuations in engine speed. The instantaneous value of the rotational speed of a four-stroke engine pulsates through the stroke transition of each cylinder. Each time the crankshaft rotates, for example, by 30° CA (crank angle), the ECU 0 counts the time required for the 30° CA rotation. The required time of 30° CA suggests the instantaneous value of the rotational speed of the crankshaft, that is, the engine rotational speed.

Then, the ECU0 uses the instantaneous value of the engine rotational speed at the timing when the piston of each cylinder 1 reaches a specific position to calculate the amount of decrease in step S2. For example, the instantaneous value Ne ₀ of the engine speed at timing t ₀ when 90° CA has elapsed since a certain cylinder 1 reached the compression top dead center, and the cylinder 1 that will reach the compression top dead center next to that cylinder 1 will be compressed. The difference dNe (=Ne ₁ - _{Ne 0} ) from the instantaneous value Ne ₁ of the engine rotation speed at timing t ₁ when 90° CA has elapsed since reaching the top dead center is calculated as 90° after the compression top dead center of each cylinder 1. Calculate each time the CA timing comes. This difference dNe becomes the amount of decrease in the instantaneous value of the engine speed referred to in step S2. ECU0 compares the difference dNe with a threshold value each time the timing of 90° CA after compression top dead center of each cylinder 1 comes, and if the difference dNe exceeds the threshold value, it determines that a sudden braking event has occurred. .

The threshold value to be compared with the difference dNe in step S2 is set according to the vehicle speed, the gear ratio of the CVT 9, and the engine rotation speed at the time of the comparison. FIG. 5 shows the relationship between the vehicle speed, the gear ratio of the CVT 9, and the engine speed, and the threshold value. Note that since the difference dNe becomes a negative value in the process of decreasing the engine speed, the threshold value is also a negative value. "The amount of decrease in the instantaneous value of the engine speed exceeds the threshold value" means that the negative difference dNe is less than the negative threshold value (exceeds as an absolute value).

In FIG. 5, the solid line represents the threshold when the engine speed is relatively low, the broken line represents the threshold when the engine speed is higher, and the dashed line represents the threshold when the engine speed is higher, The two-dot chain line represents the threshold value when the engine speed is higher than that. As a tendency, the higher the engine speed, the lower the negative threshold value (larger as an absolute value), and the more difficult it becomes for the condition of step S2 to hold. This corresponds to the fact that the higher the current engine speed, the more margin there is until the engine stalls.

Moreover, the higher the vehicle speed, the lower the negative threshold value becomes, and the more difficult it becomes for the condition of step S2 to hold. This corresponds to the fact that the higher the current vehicle speed is, the higher the gear ratio of the CVT 9 is controlled (the value of the reduction ratio becomes smaller), and the engine is less likely to stall. Incidentally, the current vehicle speed may be obtained through a sensor that detects the rotational speed of the wheels, or may be obtained from the engine rotational speed, the gear ratio of the CVT 9, the gear ratio (final reduction ratio) of the differential device, and the circumference of the driving wheels. It may be calculated from the length (=diameter of drive wheel x pi).

In addition to the above, if a fuel cut is being executed (step S4) when a sudden braking event occurs (step S2) and the lock-up of the torque converter 7 is released (step S3), the fuel cut is After finishing, fuel injection and ignition combustion are restarted (step S5).

In this embodiment, a torque converter 7 and automatic transmissions 8, 9 are interposed between the output shaft of an internal combustion engine 100 mounted on the vehicle and the drive wheels of the vehicle to control a vehicle. It is detected that the brake pedal is depressed by the driver, and the amount of decrease in the instantaneous value of the engine rotation speed detected each time the output shaft of the internal combustion engine 100 rotates by a predetermined angle is the current vehicle speed or the automatic transmission 8, The vehicle control device 0 is configured to release the lock-up of the torque converter 7 by the lock-up clutch 73 on the condition that the torque exceeds a threshold value set according to the gear ratio of 9.

According to this embodiment, it is possible to reliably prevent engine stall during sudden braking. Therefore, it is now acceptable to maintain and continue locking up the torque converter 7 even in vehicles with lower vehicle heights, which contributes to improving fuel efficiency. Since the method of this embodiment does not require a master cylinder pressure sensor or a brake pedal stroke sensor, it is possible to eliminate these and further reduce costs.

<Second Embodiment> In the second embodiment of the present invention, which will be described subsequently, the conditions for releasing the lock-up of the torque converter 7 are partially changed from the first embodiment. Hereinafter, differences from the first embodiment will be mainly described. Elements common to the first embodiment may be configured in the same manner as the first embodiment, and description thereof will be omitted for the sake of brevity.

As shown in FIG. 6, the ECU0 of this embodiment detects, via the stop lamp switch, that the brake pedal is depressed by the driver of the vehicle (step S1), and also detects the amount of decrease in vehicle speed per unit time. If the absolute value of exceeds the threshold value (step S6), it is determined that a sudden braking event has occurred, and the lock-up clutch 73 of the torque converter 7 is disengaged (step S3).

As already mentioned, the stop lamp switch can detect whether or not the driver is currently depressing the brake pedal, but cannot know how strongly the driver is depressing the brake pedal. Therefore, in the present embodiment, a sign of sudden braking such as locking the rotation of the wheels is detected by referring to the time differential value of the deceleration of the vehicle, that is, the vehicle speed.

The ECU0 measures the current vehicle speed at predetermined intervals. Then, the current acceleration or deceleration of the vehicle is calculated by subtracting the previously measured vehicle speed value from the currently measured vehicle speed value to determine the difference between the two. If the difference is a positive value, it is the amount of increase in vehicle speed per unit time, that is, acceleration. If the difference is a negative value, it is the amount of decrease in vehicle speed per unit time, that is, deceleration. In step S6, the ECU0 determines that a sudden braking event has occurred if the difference between the vehicle speed measured this time and the vehicle speed measured last time is a negative value and its absolute value exceeds a threshold value. Note that the threshold value referred to here is a positive value.

In addition to the above, if a fuel cut is being executed (step S4) when a sudden braking event occurs (step S2) and the lock-up of the torque converter 7 is released (step S3), the fuel cut is After finishing, fuel injection and ignition combustion are restarted (step S5).

In this embodiment, a torque converter 7 and automatic transmissions 8, 9 are interposed between the output shaft of an internal combustion engine 100 mounted on the vehicle and the drive wheels of the vehicle to control a vehicle. The lock-up of the torque converter 7 by the lock-up clutch 73 is released on condition that it is detected that the brake pedal is depressed by the driver and the absolute value of the amount of decrease in vehicle speed per unit time exceeds a threshold value. A control device 0 for a vehicle was constructed.

According to this embodiment, as shown in FIG. 7, it is possible to release the lockup during sudden braking and reliably prevent engine stall. After time _T0 when the driver depresses the brake pedal and the stop lamp switch outputs a signal f indicating this, the lock-up solenoid valve is operated at time _T1 when the amount of decrease in vehicle speed per unit time exceeds the threshold value. Since the lock-up of the torque converter 73 is released in this manner, the engaged lock-up clutch 73 can be disengaged before the time point _T2 when the rotation of the wheels declines. Therefore, as in the first embodiment, as long as the vehicle is not suddenly braked, the lock-up of the torque converter 7 can be maintained and continued even if the vehicle is lower than the vehicle, which contributes to improving fuel efficiency. Since the method of this embodiment does not require a master cylinder pressure sensor or a brake pedal stroke sensor, it is possible to eliminate these and further reduce costs.

Note that the present invention is not limited to the embodiments detailed above. For example, the aspect of the automatic transmission installed in the vehicle is not limited to the forward/reverse switching device 8 and the belt type CVT 9.

Further, a vehicle to which the present invention is applied may include a master cylinder pressure sensor or a brake pedal stroke sensor. The present invention can also function as a fail-safe in case these sensors malfunction.

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

INDUSTRIAL APPLICATION This invention is applicable to the control of the lock-up clutch of the torque converter mounted in a vehicle.

0...Control unit (ECU)
100... Internal combustion engine 7... Torque converter 73... Lock-up clutch 9... Automatic transmission (belt type CVT)
a... Vehicle speed signal b... Crank angle signal f... Stop lamp switch signal t... Lock-up solenoid valve opening operation signal v... Gear ratio control signal

Claims (2)

A torque converter and a belt-type continuously variable transmission are interposed between the output shaft of the internal combustion engine mounted on the vehicle and the vehicle's drive wheels to control vehicles that are not equipped with a master cylinder pressure sensor or brake pedal stroke sensor. It is something that
The higher the current engine speed, the greater the absolute value, or the higher the current vehicle speed, the greater the absolute value, or the higher the gear ratio of the current belt-type continuously variable transmission, the greater the absolute value. Set a threshold such that
It is detected that the brake pedal is depressed by the driver of the vehicle, and the amount of decrease in the instantaneous value of the engine speed detected each time the output shaft of the internal combustion engine rotates by a predetermined angle is determined by the current engine speed, vehicle speed, or The lock-up of the torque converter by the lock-up clutch is released on the condition that the speed exceeds the threshold value set according to the gear ratio of the belt-type continuously variable transmission , and furthermore, when the lock-up is released, a fuel cut is executed. A vehicle control device that terminates fuel cut and restarts fuel injection and combustion if A torque converter and a belt-type continuously variable transmission are interposed between the output shaft of the internal combustion engine mounted on the vehicle and the vehicle's drive wheels to control vehicles that are not equipped with a master cylinder pressure sensor or brake pedal stroke sensor. It is something that
When it is detected that the brake pedal is pressed by the vehicle driver and the absolute value of the decrease in vehicle speed per unit time exceeds a threshold, the lock-up of the torque converter by the lock-up clutch is released. Further, if a fuel cut is being executed when the lockup is released, the vehicle control device terminates the fuel cut and restarts fuel injection and combustion .

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