Vehicle control device

Abstract

To provide a control device for a vehicle which can decelerate vehicle speed to setting vehicle speed by low gear change while restraining unnecessary rise of rotational frequency of a driving source.SOLUTION: Execution / non-execution of low gear change which shifts a transmission gear ratio of a CVT to low side of a gear is determined if vehicle speed exceeds setting vehicle speed. A gear change solenoid valve is controlled so that the transmission gear ratio of the CVT shifts gear toward a first transmission gear ratio (S22) if the execution of low gear change is determined (S21:YES). A target of the transmission gear ratio of the CVT is altered from the first transmission gear ratio to a second transmission gear ratio while the transmission gear ratio of the CVT is shifted toward the first transmission gear ratio if the vehicle speed is lowered to the setting vehicle speed. And then, the transmission gear ratio of the CVT is retained at the second transmission gear ratio.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] 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 larger than the accelerator opening limit that causes the vehicle speed to converge to the set vehicle speed, the driving source for traveling is controlled using the accelerator opening limit, thereby limiting the vehicle speed so that it does not exceed the set vehicle speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-6334 A Summary of the Invention [Problem to be solved by the invention]

[0004] On a downhill road, even if the throttle opening limit is set to 0, the vehicle will accelerate due to its own weight. Therefore, 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).

[0005] When the vehicle is shifted to a lower gear, the rotation speed of the drive source increases as the vehicle decelerates. Therefore, if the vehicle is shifted to a lower gear ratio than that required for decelerating the vehicle, the rotation speed of the drive source increases unnecessarily, which increases noise vibrations (NV), and reduces the usability of the vehicle.

[0006] An 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 a drive source. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the vehicle control device of the present invention is a control device that is used in a vehicle equipped with a transmission that changes the driving power output by a drive source, and performs control for a vehicle speed limiting function that limits the vehicle speed with a set vehicle speed as an upper limit, and when the vehicle speed exceeds the set vehicle speed, determines whether or not to perform a low gear shift, which shifts the gear ratio of the transmission to the low side, and 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.

[0008] 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 to shift 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 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 or equal to 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.

[0009] 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.

[0010] As a result, the gear ratio is maintained at the second gear ratio, so that unnecessary fluctuations in the rotation speed of the drive source due to changes in the gear ratio can be suppressed. Effect of the Invention

[0011] According to the present invention, the vehicle speed can be reduced to a set vehicle speed by low shifting while suppressing an unnecessary increase in the rotation speed of the drive source. [Brief description of the drawings]

[0012] [Figure 1] 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. [Diagram 2] 10 is a flowchart showing a process for determining whether or not a low gear shift is to be performed; [Diagram 3] 13 is a flowchart showing the flow of a low shift process. [Figure 4] 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0014] <ASLシステム> 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.

[0015] The ASL (Adjustable Speed ​​Limiter) system 1 is applied to, for example, a vehicle equipped with an engine 2 as a driving source for traveling, and is a system that limits the vehicle speed to a set vehicle speed (upper limit) that is arbitrarily set by the user.

[0016] 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 an ignition plug for generating an electrical discharge in the combustion chamber.

[0017] 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. A hydraulic circuit for supplying 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.

[0018] The ASL system 1 includes an EG / CVT-ECU (Electronic Control Unit) 11 for controlling the engine 2 and the CVT 4. A vehicle is equipped with a plurality of ECUs including the EG / CVT-ECU 11. Each ECU includes a microcontroller unit (microcontroller unit), and the microcontroller 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 plurality of ECUs are connected to enable two-way communication using a controller area network (CAN) 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 received from the various sensors, each ECU also receives information required for control from other ECUs.

[0019] The EG / CVT-ECU 11 receives information on the accelerator opening and the vehicle speed.

[0020] A 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 accelerator pedal operation to the maximum amount of accelerator pedal operation, can be obtained from the amount of accelerator pedal operation and the maximum amount of accelerator pedal operation.

[0021] The vehicle is also provided with a vehicle speed sensor that outputs a pulse signal as a detection 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.

[0022] 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 steering column of the vehicle is provided with an ASL switch (SW) 12 that instructs activation / deactivation of the ASL that limits the vehicle speed at a set vehicle speed, and a cruise control switch (SW) 13 that instructs activation / deactivation of the cruise control function and sets a set vehicle speed that is used in common 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.

[0023] The EG / CVT-ECU 11 substantially includes an ASL control unit 21, an engine control unit 22, and a T / M control unit 23 as functional processing units.

[0024] The ASL control unit 21 performs ASL control to limit the vehicle speed to a set vehicle speed when ASL operation is instructed by operating the ASL switch 12. In order to limit the vehicle speed to the set vehicle speed, the ASL control unit 21 is provided with an ASL throttle control logic that sets an accelerator opening according to the vehicle speed and the set vehicle speed as a limited accelerator opening, and an ASL shift control logic that outputs a low shift request to shift the gear ratio of the CVT4 to the low side.

[0025] When ASL control is being performed, the engine control unit 22 compares the driver accelerator opening, which is the accelerator opening due to 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 (throttle opening) of the electronic throttle valve 3 is stored in the non-volatile memory of the EG / CVT-ECU 11, and the engine control unit 22 determines a target throttle opening according to the smaller of the driver accelerator opening and the limited accelerator opening from that relationship. The EG / CVT-ECU 11 then controls the electronic throttle valve 3 so that the throttle opening matches the target.

[0026] An ASL-compatible control logic is incorporated in the T / M control unit 23. When a low-speed change request is output from the ASL control unit 21, the ASL-compatible control logic is used in the T / M control unit 23 to set, for example, a target gear ratio of the CVT 4 to a gear ratio that is higher than the current gear ratio by a predetermined value toward the low side (the side with a higher gear ratio). Then, the T / M control unit 23 controls the gear shift solenoid valve 5 so that the gear ratio of the CVT 4 coincides with the target.

[0027] <Low gear shift execution determination process> FIG. 2 is a flowchart showing the flow of the low shift execution determination process.

[0028] When the vehicle speed exceeds a set vehicle speed, the ASL control unit 21 of the EG / CVT-ECU 11 performs a low gear shift execution determination process shown in FIG. 2 to determine whether or not to execute a low gear shift, which shifts the gear ratio of the CVT 4 to the low side.

[0029] In this low shift execution determination process, first, it is determined whether or not 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 or not the vehicle speed exceeds the set vehicle speed.

[0030] If the vehicle speed exceeds the set vehicle speed (YES in step S11), the accelerator opening limit is set to 0. Then, depending on the setting of the accelerator opening limit, it is determined whether or not a command to fully close the electronic throttle valve 3 (throttle full closure command) has been output from the engine control unit 22 (step S12).

[0031] When a throttle full closure command is output (YES in step S12), it is determined whether or not an inflection point arrival estimated time or more has elapsed since the output of the throttle full closure command (which approximately coincides with the time when the vehicle speed exceeds 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 to when 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 rotation speed of the engine 2, and can be calculated from the rotation speed of the engine 2.

[0032] 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 begins to decrease. Therefore, when the vehicle is traveling on a flat road, the vehicle begins to decelerate, and the acceleration of the vehicle 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 acceleration of the vehicle is equal to or greater than 0, it is considered that the vehicle is accelerating due to its own weight because it is traveling downhill.

[0033] 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 differentiation of the vehicle speed is 0 or more (step S14). If the vehicle acceleration is 0 or more (YES in step S14), a decision is made to perform a low gear shift (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 decision is made not to perform a low gear shift (step S16), and no low gear shift request is output from the ASL control unit 21.

[0034] <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.

[0035] In order to perform a low gear shift, when it is determined in the low gear shift execution determination process described above, the ASL control unit 21 of the EG / CVT-ECU 11 executes the low gear shift process shown in FIG.

[0036] In the low gear shift process, it is determined whether or not the execution of the low gear shift has been determined in the low gear shift execution determination process (step S21). If it is determined in the low gear shift execution determination process that the low gear shift will not be executed (NO in step S21), the low gear shift process does not proceed thereafter.

[0037] When it is determined that a low speed change is to be performed (YES in step S21), a low speed change request for changing the gear ratio of the CVT 4 toward the first speed ratio is transmitted from the ASL control unit 21 to the T / M control unit 23. The first speed ratio is set to a speed ratio that is at least lower than the current speed ratio of the CVT 4, and is set to, for example, the lowest speed ratio (maximum speed ratio) of the CVT 4. Then, the T / M control unit 23 that has received the low speed change request controls the speed change solenoid valve 5 so that the gear ratio of the CVT 4 is changed toward the first speed ratio (step S22).

[0038] 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 a set vehicle speed (step S23). As shown in Fig. 4, as the gear ratio of the CVT 4 increases, the vehicle speed decreases.

[0039] Then, when the vehicle speed decreases 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 decreases to the set vehicle speed. In other words, when the vehicle speed decreases to the set vehicle speed, the second gear ratio, which is the gear ratio at that time, is set as the target gear ratio of the CVT4 thereafter. As a result, the gear ratio of the CVT4 is maintained at the second gear ratio (step S24).

[0040] Thereafter, 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 causes the vehicle speed to converge to the set vehicle speed, and the engine control unit 22 determines a target throttle opening according to the accelerator opening limit. The engine control unit 22 then controls the electronic throttle valve 3 so that the throttle opening coincides with the target. This maintains the vehicle speed at the set vehicle speed.

[0041] <Action and effect> As described above, when the vehicle speed increases to the set vehicle speed, a determination is made as to whether or not to perform a low gear shift, which shifts the gear ratio of the CVT4 to the low side. In the low gear shift, the gear ratio of the CVT4 is shifted toward the first gear ratio, which 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 gear shift from being performed to a gear ratio greater than or equal to that required for decelerating the vehicle, and to prevent the rotation speed of the engine 2 from increasing unnecessarily. Moreover, the low gear shift allows the vehicle speed to be decelerated to the set vehicle speed.

[0042] Furthermore, since the gear ratio after the vehicle speed has decreased to the set vehicle speed is maintained at the second gear ratio, unnecessary fluctuations in the rotation speed of the engine 2 due to changes in the gear ratio can be suppressed.

[0043] <Modification> Although one embodiment of the present invention has been described above, the present invention can be embodied in other forms.

[0044] For example, in the above-described 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 are equipped with a motor as a driving source for running, so long as the vehicle is equipped with a transmission that changes the power from the driving source for running.

[0045] 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).

[0046] In addition, various design modifications can be made to the above-described configuration within the scope of the claims. [Explanation of symbols]

[0047] 2: Engine (power source) 4: CVT (transmission) 11: EG / CVT-ECU (vehicle control device)

Claims

[Claim 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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