JP7665403B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

Conventionally, vehicles equipped with a variable speed limiter (ASL) have been provided. The variable speed limiter is a function that limits the increase in vehicle speed to a vehicle speed set by the user. When the variable speed limiter is activated, if the accelerator opening operated by the driver is greater than the accelerator opening limit that converges the vehicle speed to the set vehicle speed, the driving source for driving is controlled using the accelerator opening limit, thereby limiting the vehicle speed so that it does not exceed the set vehicle speed.

JP 2010-6334 A

On a downhill road, even if the throttle opening limit is set to 0, the vehicle will accelerate due to its own weight, so in order to prevent the vehicle speed from exceeding the upper limit, it may be necessary to decelerate by shifting the gear ratio of the transmission, which changes the power from the drive source, to the lower side (low shift).

When shifting to a lower gear, the rotation speed of the drive source increases as the vehicle decelerates. Therefore, if the gear ratio is shifted to a lower gear ratio than that required to decelerate the vehicle, the rotation speed of the drive source increases unnecessarily, increasing noise vibrations (NV), and reducing the usability of the vehicle.

The object of the present invention is to provide a vehicle control device that can reduce the vehicle speed to a set vehicle speed by shifting to low while suppressing unnecessary increases in the rotation speed of the drive source.

To achieve the above object, the vehicle control device of the present invention is a control device used in a vehicle equipped with a transmission that changes the driving power output by a drive source, and controls a vehicle speed limiting function that limits the vehicle speed up to a set vehicle speed. When the vehicle speed exceeds the set vehicle speed, it determines whether or not to perform a low gear shift, which shifts the gear ratio of the transmission to the low side. In the low gear shift, the gear ratio of the transmission is shifted toward a first gear ratio that is set lower than the current gear ratio, and when the vehicle speed drops to the set vehicle speed, the target gear ratio is changed from the first gear ratio to a second gear ratio.

According to this configuration, when the vehicle speed exceeds a set vehicle speed, it is determined whether or not to perform a low gear shift, which shifts the gear ratio of the transmission to the low side. In a low gear shift, the gear ratio of the transmission is shifted toward a first gear ratio that is set to be lower than the current gear ratio, and when the vehicle speed drops to the set vehicle speed, the target gear ratio is changed from the first gear ratio to the second gear ratio. This makes it possible to prevent a low gear shift from being performed to a gear ratio greater than that required for decelerating the vehicle, and to prevent the rotation speed of the drive source from increasing unnecessarily. Moreover, the low gear shift allows the vehicle speed to be decelerated to the set vehicle speed.

The vehicle control device may set the second gear ratio to the gear ratio at the time when the vehicle speed has decreased to the set vehicle speed, and control the output of the drive source so that the vehicle speed is maintained at the set vehicle speed while maintaining the gear ratio at the second gear ratio after the vehicle speed has decreased to the set vehicle speed.

This keeps the gear ratio at the second gear ratio, suppressing unnecessary fluctuations in the rotation speed of the drive source caused by shifting the gear ratio.

According to the present invention, it is possible to reduce the vehicle speed to a set vehicle speed by shifting to low while suppressing unnecessary increases in the rotation speed of the drive source.

1 is a block diagram showing a configuration of an ASL system including an EG/CVT-ECU according to an embodiment of the present invention. 10 is a flowchart showing a process for determining whether or not a low gear shift is to be performed; 13 is a flowchart showing the flow of a low shift process. 11A and 11B are diagrams illustrating an example of time variations in vehicle speed, gear ratio, and limited accelerator opening degree when a low gear shift is performed.

The following describes in detail an embodiment of the present invention with reference to the attached drawings.

<ASL System>
FIG. 1 is a block diagram showing the configuration of an ASL system 1 including an EG/CVT-ECU 11 according to an embodiment of the present invention.

The ASL (Adjustable Speed Limiter) system 1 is applied to, for example, a vehicle equipped with an engine 2 as a driving source for driving, and is a system that limits the vehicle speed to a set speed (upper limit) that is arbitrarily set by the user.

The engine 2 is equipped with an electronic throttle valve 3 for adjusting the amount of air intake into the combustion chamber of the engine 2, an injector (fuel injection device) for injecting fuel into the intake air, and a spark plug for generating an electrical discharge in the combustion chamber.

The vehicle is equipped with a CVT (Continuously Variable Transmission) 4 as a transmission that changes the speed of the power from the engine 2 and outputs it to the drive wheels. The CVT 4 is a belt-type continuously variable transmission. The hydraulic circuit that supplies hydraulic pressure to each part of the CVT 4 includes a shift solenoid valve 5 that controls the hydraulic pressure supplied to the primary sheave and secondary sheave to change the gear ratio of the CVT 4.

The ASL system 1 includes an EG/CVT-ECU (Electronic Control Unit) 11 for controlling the engine 2 and the CVT 4. The vehicle is equipped with multiple ECUs, including the EG/CVT-ECU 11. Each ECU has a microcontroller unit (microcomputer), which includes, for example, a CPU, a non-volatile memory such as a flash memory, and a volatile memory such as a dynamic random access memory (DRAM). The multiple ECUs are connected to enable two-way communication using the CAN (Controller Area Network) communication protocol. Each ECU is connected to various sensors required for control, and receives detection signals from the connected sensors. In addition to the detection signals input from the various sensors, each ECU also receives information required for control from other ECUs.

Information on the accelerator opening and vehicle speed is input to the EG/CVT-ECU 11.

The vehicle is provided with an accelerator pedal that is operated by the driver's foot, and an accelerator sensor that is associated with the accelerator pedal and outputs a detection signal corresponding to the amount of accelerator pedal operation. The amount of accelerator pedal operation can be obtained from the detection signal of the accelerator sensor, and the accelerator opening, which is the ratio of the amount of operation to the maximum amount of accelerator pedal operation, can be obtained from that amount and the maximum amount of accelerator pedal operation.

The vehicle is also provided with a vehicle speed sensor that outputs a detection signal, a pulse signal synchronized with the rotation of a rotor that rotates as the vehicle travels. The vehicle speed can be calculated by determining the frequency of the detection signal of the vehicle speed sensor and applying the frequency to a conversion formula.

The vehicle is equipped with a cruise control function that maintains the vehicle speed at a set speed that is arbitrarily set by the user. The vehicle's steering column is provided with an ASL switch (SW) 12 that activates/deactivates the ASL, which limits the vehicle speed to a set speed, and a cruise control switch (SW) 13 that activates/deactivates the cruise control function and sets a set vehicle speed that is used commonly for the ASL and cruise control. Signals corresponding to the operation of the ASL switch 12 and the cruise control switch 13 are input to the EG/CVT-ECU 11.

The EG/CVT-ECU 11 essentially comprises an ASL control unit 21, an engine control unit 22, and a T/M control unit 23 as functional processing units.

When ASL operation is instructed by operation of the ASL switch 12, the ASL control unit 21 performs ASL control to limit the vehicle speed to a set vehicle speed. In order to limit the vehicle speed to the set vehicle speed, the ASL control unit 21 incorporates an ASL throttle control logic that sets the accelerator opening according to the vehicle speed and the set vehicle speed as the limited accelerator opening, and an ASL shift control logic that outputs a low shift request to shift the gear ratio of the CVT 4 to the low side.

When ASL control is being performed, the engine control unit 22 compares the driver accelerator opening, which is the accelerator opening caused by operation of the accelerator pedal, with the limited accelerator opening input from the ASL control unit 21, and acquires the smaller of them (MIN acquisition). The relationship between the accelerator opening and the opening of the electronic throttle valve 3 (throttle opening) is stored in the non-volatile memory of the EG/CVT-ECU 11, and the engine control unit 22 uses this relationship to determine a target throttle opening corresponding to the smaller of the driver accelerator opening and the limited accelerator opening. The EG/CVT-ECU 11 then controls the electronic throttle valve 3 so that the throttle opening matches the target.

The T/M control unit 23 incorporates ASL-compatible control logic. When a low-speed change request is output from the ASL control unit 21, the ASL-compatible control logic in the T/M control unit 23 sets, for example, the target gear ratio of the CVT 4 to a gear ratio that is a predetermined value higher on the low side (the side with a higher gear ratio) than the current gear ratio. The T/M control unit 23 then controls the gear change solenoid valve 5 so that the gear ratio of the CVT 4 matches the target.

<Low gear shift execution determination process>
FIG. 2 is a flowchart showing the flow of the low shift execution determination process.

When the vehicle speed exceeds a set vehicle speed, the ASL control unit 21 of the EG/CVT-ECU 11 performs the low-speed shift execution determination process shown in FIG. 2 to determine whether or not to execute a low-speed shift, which shifts the gear ratio of the CVT 4 to the low side.

In this low-speed shift execution determination process, first, it is determined whether the vehicle speed exceeds a set vehicle speed (step S11). While the vehicle speed is equal to or lower than the set vehicle speed, the process does not proceed to the next step, and it is repeatedly determined whether the vehicle speed exceeds the set vehicle speed.

If the vehicle speed exceeds the set vehicle speed (YES in step S11), the throttle opening limit is set to 0. Then, depending on the throttle opening limit setting, it is determined whether or not an instruction to fully close the electronic throttle valve 3 (throttle full closure instruction) has been output from the engine control unit 22 (step S12).

When a throttle full closure command is output (YES in step S12), it is determined whether or not the inflection point arrival estimated time has elapsed since the throttle full closure command was output (which approximately coincides with the time when the vehicle speed exceeded the set vehicle speed) (step S13). The inflection point arrival estimated time is set to the delay time from the output of the throttle full closure command until the output of the engine 2 begins to decrease due to the electronic throttle valve 3 being fully closed. The delay time is calculated by adding the throttle delay time (fixed value) according to the time constant of the motor that opens and closes the electronic throttle valve 3, and the combustion stroke delay time required from the intake stroke to the combustion stroke of the engine 2. The combustion stroke delay time depends on the engine 2 rotation speed, so it can be calculated from the engine 2 rotation speed.

Therefore, when the estimated time to reach the inflection point has elapsed since the output of the throttle fully closed command, an inflection point is reached where the output of engine 2 changes from increasing to decreasing, and when the estimated time to reach the inflection point has elapsed, the output of engine 2 has begun to decrease. Therefore, when the vehicle is traveling on a flat road, the vehicle has begun to decelerate, and the vehicle acceleration indicates a negative value. On the other hand, when the estimated time to reach the inflection point has elapsed since the output of the throttle fully closed command and the output of engine 2 has decreased, the vehicle is accelerating and the vehicle acceleration is 0 or greater, it is considered that the vehicle is traveling downhill and accelerating due to its own weight.

Therefore, when the estimated time to reach the inflection point has elapsed since the output of the throttle full closure command (YES in step S13), it is determined whether the acceleration calculated by the time derivative of the vehicle speed is 0 or greater (step S14). If the vehicle acceleration is 0 or greater (YES in step S14), a low gear shift is determined to be performed (step S15), and a low gear shift request is sent from the ASL control unit 21 to the T/M control unit 23. On the other hand, if the vehicle acceleration is less than 0 (NO in step S14), a low gear shift is not determined to be performed (step S16), and no low gear shift request is output from the ASL control unit 21.

<Low gear shift processing>
Fig. 3 is a flowchart showing the flow of low gear shift processing. Fig. 4 is a diagram showing an example of time-dependent changes in vehicle speed, gear ratio, and accelerator opening limit when a low gear shift is performed.

When it is determined in the low-speed shift execution determination process described above that a low-speed shift should be performed, the ASL control unit 21 of the EG/CVT-ECU 11 executes the low-speed shift process shown in FIG. 3 in order to perform a low-speed shift.

In the low gear shift process, it is determined whether or not a low gear shift has been decided to be performed in the low gear shift execution determination process (step S21). If a low gear shift has not been decided to be performed in the low gear shift execution determination process (NO in step S21), the low gear shift process does not proceed further.

When it is determined that a low gear shift is to be performed (YES in step S21), a low gear shift request to shift the gear ratio of the CVT 4 toward the first gear ratio is sent from the ASL control unit 21 to the T/M control unit 23. The first gear ratio is set to a gear ratio that is at least lower than the current gear ratio of the CVT 4, for example, set to the lowest gear ratio (maximum gear ratio) of the CVT 4. Then, the T/M control unit 23 that has received the low gear shift request controls the gear shift solenoid valve 5 so that the gear ratio of the CVT 4 is shifted toward the first gear ratio (step S22).

While the gear ratio of the CVT 4 is being shifted toward the first gear ratio, it is repeatedly determined whether the vehicle speed is equal to or lower than the set vehicle speed (step S23). As shown in FIG. 4, as the gear ratio of the CVT 4 increases, the vehicle speed decreases.

Then, when the vehicle speed drops to the set vehicle speed, the target gear ratio of the CVT4 is changed from the first gear ratio to the second gear ratio. The second gear ratio is set to the gear ratio at the time when the vehicle speed drops to the set vehicle speed. In other words, when the vehicle speed drops to the set vehicle speed, the second gear ratio, which is the gear ratio at that time, becomes the target gear ratio of the CVT4 thereafter. This causes the gear ratio of the CVT4 to be held at the second gear ratio (step S24).

After that, while the gear ratio of the CVT 4 is held at the second gear ratio, the ASL control unit 21 of the EG/CVT-ECU 11 sets an accelerator opening limit that converges the vehicle speed to the set vehicle speed, and the engine control unit 22 determines a target throttle opening that corresponds to the accelerator opening limit. The engine control unit 22 then controls the electronic throttle valve 3 so that the throttle opening matches the target. This maintains the vehicle speed at the set vehicle speed.

<Action and effect>
As described above, when the vehicle speed increases to the set vehicle speed, it is determined whether or not to perform a low speed shift, which shifts the gear ratio of the CVT 4 to the low side. In the low speed shift, the gear ratio of the CVT 4 is shifted toward a first gear ratio that is set to be lower than the current gear ratio, and when the vehicle speed decreases to the set vehicle speed, the target gear ratio is changed from the first gear ratio to the second gear ratio. This makes it possible to prevent a low speed shift from being performed to a gear ratio greater than or equal to the gear ratio required for decelerating the vehicle, and to prevent the rotation speed of the engine 2 from increasing unnecessarily. Moreover, the low speed shift allows the vehicle speed to be decelerated to the set vehicle speed.

In addition, since the gear ratio is maintained at the second gear ratio after the vehicle speed has decreased to the set vehicle speed, unnecessary fluctuations in the rotation speed of the engine 2 due to changes in the gear ratio can be suppressed.

<Modification>
Although one embodiment of the present invention has been described above, the present invention can be embodied in other forms.

For example, in the above embodiment, the ASL system 1 is applied to a vehicle equipped with an engine 2 as a driving source for running, but the present invention can also be applied to electric vehicles (hybrid vehicles, electric automobiles) that use a motor as a driving source for running, as long as the vehicle is equipped with a transmission that changes the speed of the power from the driving source for running.

The transmission is not limited to a belt-type continuously variable transmission, but may be a toroidal type or other type of continuously variable transmission, or may be a stepped automatic transmission (AT). The transmission may also be a manual transmission (MT).

In addition, various design modifications can be made to the above-mentioned configuration within the scope of the claims.

2: Engine (power source)
4: CVT (transmission)
11: EG/CVT-ECU (vehicle control device)

Claims (1)

A control device is used in a vehicle equipped with a continuously variable transmission that changes the speed of a driving power output from a drive source, and performs control for a vehicle speed limiting function that limits the vehicle speed up to a set vehicle speed,
controlling an output of the drive source to an output corresponding to a smaller one of a driver accelerator opening, which is an accelerator opening operated by a driver of the vehicle, and a limited accelerator opening, which is an accelerator opening corresponding to a vehicle speed and the set vehicle speed;
When the vehicle speed exceeds the set vehicle speed, it is determined whether or not to perform a low shift to shift the gear ratio of the continuously variable transmission to a low side;
In the low shift, the gear ratio of the continuously variable transmission is shifted toward a first gear ratio that is set to a lower side than the current gear ratio, and when the vehicle speed decreases to the set vehicle speed, the gear ratio at the time when the vehicle speed has decreased to the set vehicle speed is set to a second gear ratio, and a target of the gear ratio is changed from the first gear ratio to the second gear ratio , and while the gear ratio is maintained at the second gear ratio,
A vehicle control device that sets the accelerator opening limit for converging the vehicle speed to the set vehicle speed and controls the output of the drive source so that the vehicle speed is maintained at the set vehicle speed .

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