Vehicle control device

Abstract

To provide a vehicular control device that can determine whether low gear shift is executed or not executed, without using a sensor for determining a road surface gradient.SOLUTION: When a vehicle speed is over a set speed (S11:YES), a throttle full-close instruction is output. When the throttle full-close instruction is output (S12:YES), it is determined whether estimated time of reaching an inflection point or more has elapsed since the throttle full-close instruction is output or not (Step S13). The estimated time of reaching the inflection point is set to a delay time during which output of an engine starts to decrease due to full close of an electronic throttle valve after the throttle full-close instruction is output. At a time point after the estimated time of reaching the inflection point or more has elapsed, when acceleration of a vehicle is equal to or above 0 (S14:YES), it is determined that execution of low gear shift is decided (S15), and when the acceleration of the vehicle is less than 0 (S14:NO), it is determined that non-execution of the low gear shift is decided (S16).SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, there are vehicles equipped with an adjustable speed limiter (ASL). The variable speed limiter is a function that limits the vehicle speed to an upper limit vehicle speed set by the user. With this function, even if the user unintentionally accelerates beyond the upper limit vehicle speed, the vehicle speed is limited to the upper limit vehicle speed, and the vehicle speed can be prevented from exceeding the upper limit vehicle speed unintentionally. [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 no acceleration operation is being performed (even if the accelerator opening is zero), the vehicle accelerates due to its own weight, so in order to prevent the vehicle speed from exceeding the upper limit vehicle speed, it may be necessary to decelerate by shifting the gear ratio of the transmission that changes the power from the driving source for driving to the low side (low shift). On the other hand, on a flat road, if a low shift is performed to decelerate, the rotation speed of the driving source increases unnecessarily, increasing NV (noise vibration), and otherwise deteriorating usability. Therefore, in order to perform a low shift, it is necessary to distinguish between flat roads and downhill roads.

[0005] A method of determining the gradient of the road surface on which a vehicle is located from the detection signal of a G sensor is widely used, but in order to reduce costs, there is a demand for a method that can distinguish between flat roads and downhill roads without using a G sensor and perform low gear shifts on downhill roads.

[0006] An object of the present invention is to provide a vehicle control device that can determine whether or not to perform a low gear shift without using a sensor for determining the road surface gradient. [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 generated by a drive source, and performs control for a vehicle speed limiting function that limits the vehicle speed to a set vehicle speed as an upper limit, predicts the timing when suppression control that suppresses an increase in vehicle speed will actually be started, and determines whether or not to perform a low shift that shifts the transmission to the low side based on the predicted timing.

[0008] According to this configuration, suppression control is performed to suppress an increase in vehicle speed as control for the vehicle speed limiting function that limits the vehicle speed to the set vehicle speed as an upper limit. In this case, the timing when the suppression control actually starts is predicted, and based on the predicted timing, it is determined whether or not to perform a low gear shift to shift the gear ratio of the transmission to the low side. Therefore, it is possible to determine (decide) whether to perform a low gear shift on a downhill road without using a sensor for determining the road surface gradient. As a result, it is possible to reduce the cost of a vehicle equipped with a vehicle speed limiting function.

[0009] The vehicle control device may estimate a delay time from when the suppression control is instructed to when the suppression control is actually started, and may determine the point in time at which the delay time has elapsed since the suppression control is instructed to be the timing at which the suppression control is actually started.

[0010] The vehicle control device may determine to perform a low shift when the vehicle speed is increasing after the timing at which the suppression control is actually started.

[0011] If the vehicle speed is increasing even though the suppression control has actually been started, it is assumed that the vehicle is traveling downhill. In this case, therefore, by performing a low shift, the vehicle can be decelerated and the vehicle speed can be effectively limited to the set vehicle speed.

[0012] The vehicle control device may estimate the amount of increase in vehicle speed from the time when the suppression control is instructed to the predicted timing based on the vehicle acceleration at the time when the suppression control is instructed, and may decide to perform a low gear shift if the estimated amount of increase is greater than or equal to a predetermined value.

[0013] The acceleration of the vehicle until the suppression control is actually started is greater when the vehicle is traveling on a downhill road than when the vehicle is traveling on a flat road. Therefore, if a predetermined value is set for the increase in vehicle speed from the time when the suppression control is instructed until the suppression control is actually started based on the increase when the vehicle is traveling on a flat road, it can be assumed that the vehicle is traveling on a downhill road if the estimated increase is equal to or greater than the predetermined value. Therefore, in this case, the vehicle can be decelerated by performing a low shift, and the vehicle speed can be effectively limited to the set vehicle speed. Effect of the Invention

[0014] According to the present invention, it is possible to determine whether or not to perform a low gear shift without using a sensor for determining the road surface gradient. [Brief description of the drawings]

[0015] [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] 3 is a diagram showing an example of a change in vehicle speed over time when the low shift execution determination process shown in FIG. 2 is performed. FIG. [Figure 4] 10 is a flowchart showing another example of the low shift execution determination process. [Diagram 5] 5 is a diagram showing an example of a change in vehicle speed over time when the low shift execution determination process shown in FIG. 4 is performed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] <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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] The EG / CVT-ECU 11 receives information on the accelerator opening and the vehicle speed.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] <Low gear shift execution determination process> Fig. 2 is a flowchart showing the flow of the low gear shift execution determination process Fig. 3 is a diagram showing an example of the time change of the vehicle speed when the low gear shift execution determination process shown in Fig. 2 is performed.

[0031] 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.

[0032] 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.

[0033] 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).

[0034] 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.

[0035] 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 exhibits a negative value, as shown by vehicle speed change line B in Fig. 3. 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, as shown by vehicle speed change line A in Fig. 3, 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.

[0036] 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.

[0037] <Effects> As described above, it is possible to determine whether to shift to low on a downhill road without using a sensor for determining the road gradient, which results in a reduction in the cost of the ASL system 1 and, ultimately, in a reduction in the cost of the vehicle equipped with the ASL system 1.

[0038] <Another example of low gear shift execution determination process> Fig. 4 is a flow chart showing another example of the low gear shift execution determination process Fig. 5 is a diagram showing an example of a time change in vehicle speed when the low gear shift execution determination process shown in Fig. 4 is performed.

[0039] In order to determine whether or not to perform a low gear shift, which shifts the gear ratio of the CVT4 to the low side, when the vehicle speed exceeds a set vehicle speed, the ASL control unit 21 of the EG / CVT-ECU 11 may perform a low gear shift execution determination process shown in FIG. 4 instead of the low gear shift execution determination process shown in FIG. 2.

[0040] In this low shift execution determination process, first, it is determined whether or not the vehicle speed exceeds a set vehicle speed (step S21). 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.

[0041] If the vehicle speed exceeds the set vehicle speed (YES in step S21), the accelerator opening limit is set to 0. Then, according to 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 S22).

[0042] When the throttle fully closed command is output (YES in step S22), the vehicle acceleration is calculated by time-differentiating the vehicle speed at the time when the throttle fully closed command is output (almost coincident with the time when the vehicle speed exceeds the set vehicle speed). Also, as in the case of the process shown in FIG. 2, the estimated time to reach the inflection point is calculated by adding the throttle delay time and the combustion stroke delay time.

[0043] Assuming that the output of the engine 2 is the same, the acceleration of the vehicle is greater when the vehicle is traveling downhill than when the vehicle is traveling on a flat road. If the product of the vehicle acceleration at the time the throttle fully closed command is output and the estimated time to reach the inflection point is estimated as the increase in vehicle speed from the time the throttle fully closed command is output until the estimated time to reach the inflection point has elapsed (the time the inflection point is reached) and a predetermined value α is set based on the increase estimated when the vehicle is traveling on a flat road, it can be estimated that the vehicle is traveling downhill if the increase in vehicle speed is equal to or greater than the predetermined value α.

[0044] Therefore, if the increase in vehicle speed from the output of the throttle full closure command to the time when the estimated time to reach the inflection point has elapsed is equal to or greater than a predetermined value α, in other words, if the estimated vehicle speed obtained by adding the increase in the vehicle speed to the set vehicle speed (the estimated vehicle speed when the inflection point is reached) is equal to or greater than the set vehicle speed plus the predetermined value α (YES in step S23), then it is decided to perform a low shift (step S24), and a low shift request is transmitted from the ASL control unit 21 to the T / M control unit 23. On the other hand, if the estimated vehicle speed when the inflection point is reached is less than the set vehicle speed plus the predetermined value α (NO in step S23), then it is decided not to perform a low shift (step S25), and no low shift request is output from the ASL control unit 21.

[0045] <Effects> As described above, the execution of low gear shifting on a downhill road can be determined without using a sensor for determining the road surface gradient, also by the process shown in Fig. 4. As a result, the cost of the ASL system 1 can be reduced, and in turn, the cost of the vehicle equipped with the ASL system 1 can be reduced.

[0046] <Modification> Although the embodiment of the present invention has been described above, the present invention can be embodied in other forms.

[0047] 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.

[0048] 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).

[0049] In addition, various design modifications can be made to the above-described configuration within the scope of the claims. [Explanation of symbols]

[0050] 2: Engine (power source) 4: CVT (transmission) 11: EG / CVT-ECU (vehicle control device) α: Predetermined value

Claims

1. A control device is used in a vehicle equipped with a transmission that changes the speed of a driving power generated by a drive source, and performs control for a vehicle speed limiting function that limits the vehicle speed to a set vehicle speed as an upper limit, Predicts the timing at which suppression control to suppress an increase in vehicle speed will actually begin, determining whether or not to perform a low shift to shift the transmission to a low side based on the predicted timing; In this judgment, the vehicle control device estimates the amount of increase in vehicle speed from the time when the suppression control is instructed to the predicted timing based on the acceleration of the vehicle at the time when the suppression control is instructed, and decides to perform the low shift if the estimated amount of increase is greater than or equal to a predetermined value.

2. Estimating a delay time from when the suppression control is instructed to when the suppression control is actually started; The vehicle control device according to claim 1 , wherein the timing is a point in time when the delay time has elapsed since the instruction for the suppression control.

Images