Vehicle control device

Abstract

To provide a vehicular control device that can release low gear shift at a proper timing, without using a sensor for determining a road surface gradient.SOLUTION: Output of an engine 2 that is required when a vehicle travels on a downward slope road at a set speed is smaller than output of the engine 2 that is required when the vehicle travels on a flat road at the set speed. Therefore, a limited accelerator aperture that is set when the vehicle travels on the downward slope road at the set speed is smaller than a limited accelerator aperture that is set when the vehicle is travels on the flat road at the set speed. Based on this relationship, after a vehicle speed falls down to the set speed, low gear shift is not released when the limited accelerator aperture is less than a predetermined value (S32:NO), and the low gear shift is released (S33) when the limited accelerator aperture is above the predetermined value (S32:YES).SELECTED DRAWING: Figure 5

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 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 causes the vehicle speed to converge 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-6334 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, to prevent the vehicle speed from exceeding the upper limit, it may be necessary to decelerate by shifting the gear ratio of the transmission that changes the power from the drive source to a lower gear (low shift). On the other hand, on a flat road, if a low shift is performed to decelerate, the rotation speed of the drive source will unnecessarily increase, increasing noise and vibration (NV), and thereby worsening usability. Therefore, to perform a low shift, it is necessary to distinguish between flat roads and downhill roads.

[0005] A method for 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 for distinguishing between flat roads and downhill roads without using a G sensor, and for changing to low gear on a downhill road to return the gear ratio to its original value when the vehicle moves from the downhill road to a flat road.

[0006] An object of the present invention is to provide a vehicle control device that can cancel low speed shifting at an appropriate timing without using a sensor for determining 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 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 up to a set vehicle speed.When the vehicle speed exceeds the set vehicle speed, the transmission's gear ratio is shifted to the low side, and after the vehicle speed has decreased to the set vehicle speed due to the shift, the transmission's gear ratio is made free when the output of the drive source becomes equal to or greater than a predetermined output.

[0008] With this configuration, the gear ratio of the transmission may be shifted to the low side (low shift) when the vehicle speed exceeds the set vehicle speed. In this case, if the vehicle speed drops to the set vehicle speed due to the low shift, the purpose of the low shift is achieved, and it is possible to end the low shift. However, if the vehicle is traveling downhill, the vehicle speed will accelerate and exceed the set vehicle speed immediately after the low shift is completed.

[0009] The output of the drive source when the vehicle is traveling downhill at a set speed is smaller than the output of the drive source when the vehicle is traveling on a flat road at the set speed. Based on this relationship, once the vehicle speed has dropped to the set speed, if the output of the drive source is less than a predetermined output, the gear ratio of the transmission is not freed, whereas if the output of the drive source is equal to or greater than the predetermined output, the gear ratio of the transmission is freed. This allows the low gear shift to be released at an appropriate time after the vehicle moves from a downhill road to a flat road. Furthermore, the low gear shift can be released at an appropriate time without using a road gradient sensor.

[0010] The vehicle control device may maintain the gear ratio of the transmission at the gear ratio at the time when the vehicle speed has decreased to the set vehicle speed until the output of the drive source becomes equal to or greater than a predetermined output after the vehicle speed has decreased to the set vehicle speed.

[0011] In this configuration, the gear ratio is kept constant, so that it is possible to determine whether the output of the drive source has reached a predetermined output without fluctuations in the output of the drive source due to fluctuations in the gear ratio, which makes the determination more accurate and allows the low gear shift to be released at a more appropriate time.

[0012] The predetermined output may be set to the output of the drive source when the vehicle is traveling on a flat road at a set vehicle speed.

[0013] In this case, when the output of the drive source reaches or exceeds a predetermined output, it can be determined that the vehicle has moved from a downhill road to a flat road, and the low gear shift can be released at an appropriate timing after the vehicle has moved onto the flat road. [Effects of the Invention]

[0014] According to the present invention, it is possible to cancel low speed shifting at an appropriate timing without using a sensor for determining road surface gradient. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram showing the configuration of an ASL system including an EG / CVT-ECU according to an embodiment of the present invention. [Figure 2] 10 is a flowchart showing a flow of a low speed change execution determination process. [Figure 3] 10 is a flowchart showing the flow of a low speed change process. [Figure 4] 10A and 10B are diagrams illustrating examples of time-dependent changes in gear ratio, accelerator opening limit, vehicle speed, and road gradient when a low gear shift is performed. [Figure 5] 10 is a flowchart showing the flow of a low speed change release process. [Figure 6] 10 is a flowchart showing another example of the low speed change execution determination process. DETAILED DESCRIPTION OF THE INVENTION

[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 one 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 driving, 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 within the combustion chamber.

[0020] The vehicle is equipped with a CVT (Continuously Variable Transmission) 4 as a transmission that changes the speed of power from the engine 2 and outputs it to the drive wheels. The CVT4 is a belt-type continuously variable transmission. A hydraulic circuit that supplies hydraulic pressure to each part of the CVT4 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 CVT4.

[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 multiple ECUs, including the EG / CVT-ECU 11. Each ECU includes a microcontroller unit (microcomputer), which incorporates, for example, a CPU, a nonvolatile memory such as a flash memory, and a volatile memory such as a dynamic random access memory (DRAM). The multiple ECUs are connected to each other so as to enable bidirectional 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 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 vehicle speed.

[0023] A vehicle is provided with an accelerator pedal that is operated by the driver, and an accelerator sensor that outputs a detection signal corresponding to the accelerator pedal depression amount. The accelerator pedal depression amount can be determined from the accelerator sensor detection signal, and the accelerator opening, which is the ratio of the accelerator pedal depression amount to the maximum accelerator pedal depression amount, can be determined from the accelerator pedal depression amount and the maximum accelerator pedal depression amount.

[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 set by the user. The steering column of the vehicle is provided with an ASL switch (SW) 12 that commands activation / deactivation of the ASL, which limits the vehicle speed at the set speed, and a cruise control switch (SW) 13 that commands activation / deactivation of 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.

[0026] The EG / CVT-ECU 11 essentially 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 equipped with an ASL throttle control logic that sets an accelerator opening corresponding 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's accelerator opening, which is the accelerator opening determined by operating the accelerator pedal, with the limit accelerator opening input from the ASL control unit 21, and acquires the smaller of them (MIN acquisition). The nonvolatile memory of the EG / CVT-ECU 11 stores the relationship between the accelerator opening and the opening of the electronic throttle valve 3 (throttle opening), and the engine control unit 22 uses this relationship to determine a target throttle opening corresponding to the smaller of the driver's accelerator opening and the limit accelerator opening. The EG / CVT-ECU 11 then controls the electronic throttle valve 3 so that the throttle opening matches the target.

[0029] ASL-compatible control logic is incorporated into T / M control unit 23. When a low speed change request is output from ASL control unit 21, T / M control unit 23 uses the ASL-compatible control logic to set, for example, a target speed ratio of CVT 4 to a speed ratio that is higher by a predetermined value on the low side (higher speed ratio side) than the current speed ratio. Then, T / M control unit 23 controls shift solenoid valve 5 so that the speed ratio of CVT 4 matches the target.

[0030] <Low gear shift execution determination process> FIG. 2 is a flowchart showing the flow of the low speed change execution determination process.

[0031] When the vehicle speed exceeds a set vehicle speed, the ASL control unit 21 of the EG / CVT-ECU 11 performs a 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.

[0032] In this low shift execution determination process, first, it is determined whether or not the vehicle speed has exceeded 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 has exceeded 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, in accordance with the setting of the accelerator opening limit, 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).

[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 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 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, and can therefore be calculated from the engine 2 rotation speed.

[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 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.

[0036] Therefore, when the estimated time to reach the inflection point has elapsed since the output of the throttle fully closed command (YES in step S13), it is determined whether the acceleration calculated by time differentiation of the vehicle speed is equal to or greater than 0 (step S14). If the vehicle acceleration is equal to or greater than 0 (YES in step S14), a decision is made to perform a low shift (step S15), and a low 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 shift (step S16), and no low shift request is output from the ASL control unit 21.

[0037] <Low gear shift processing> Fig. 3 is a flowchart showing the flow of low speed change 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 speed change is performed.

[0038] In order to perform a low speed shift, when it is determined in the low speed shift execution determination process described above, the ASL control unit 21 of the EG / CVT-ECU 11 performs the low speed shift process shown in FIG.

[0039] In the low speed change process, it is determined whether or not the execution of low speed change has been determined in the low speed change execution determination process (step S21). If it is determined in the low speed change execution determination process that low speed change will not be executed (NO in step S21), the low speed change process does not proceed thereafter.

[0040] If it is determined that a low speed change is to be performed (YES in step S21), a low speed change request to change the speed 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, upon receiving the low speed change request, the T / M control unit 23 controls the speed change solenoid valve 5 so that the speed ratio of the CVT 4 is changed toward the first speed ratio (step S22).

[0041] While the speed ratio of the CVT 4 is being shifted toward the first speed 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 speed ratio of the CVT 4 increases, the vehicle speed decreases.

[0042] Then, when the vehicle speed decreases to the set vehicle speed, the target gear ratio of the CVT 4 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 CVT 4 thereafter. As a result, the gear ratio of the CVT 4 is maintained at the second gear ratio (step S24).

[0043] Thereafter, while the speed ratio of the CVT 4 is maintained at the second speed 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 corresponding 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.

[0044] <Low gear release process> FIG. 5 is a flowchart showing the flow of the low speed change release process.

[0045] The low speed change release process is a process for determining whether to release the low speed change that shifts the gear ratio of the CVT 4 to the low side, and is performed in parallel with the low speed change process.

[0046] In the low speed change release process, it is determined whether or not a process for maintaining the gear ratio of the CVT 4 at the second speed change ratio has been started (step S31). If a process for maintaining the gear ratio at the second speed change ratio has not been started, the low speed change release process does not proceed thereafter.

[0047] When the process of maintaining the gear ratio at the second gear ratio is started (step S31), it is determined whether the accelerator opening limit output from the ASL control unit 21 to the engine control unit 22 is equal to or greater than a predetermined value (step S32). The engine control unit 22 sets a target throttle opening corresponding to the accelerator opening limit, and controls the electronic throttle valve 3 so that the throttle opening matches the target, so the accelerator opening limit corresponds to the output of the engine 2. Therefore, engine output equal to or greater than a predetermined output is equivalent to accelerator opening limit being equal to or greater than a predetermined value.

[0048] While the accelerator opening limit is less than the predetermined value (NO in step S32), the gear ratio is not released from being held at the second gear ratio.

[0049] When the limited accelerator opening becomes equal to or greater than a predetermined value (YES in step S32), the state in which the gear ratio is held at the second gear ratio is released, the low gear shift is released, and the control of the CVT4 returns to normal gear shift control (step S33).

[0050] <Action and effect> As described above, the low gear shift execution determination process shown in Fig. 2 makes it possible to determine whether to execute a low gear shift on a downhill road without using a sensor for determining the road gradient. As a result, it is possible to reduce the cost of the ASL system 1, and ultimately to reduce the cost of a vehicle equipped with the ASL system 1.

[0051] Furthermore, in a low gear shift, the gear ratio of the CVT 4 is shifted toward a first gear ratio that is set lower than the current gear ratio, and when the vehicle speed decreases to a set vehicle speed, the target gear ratio is changed from the first gear ratio to a second gear ratio. This makes it possible to prevent a low gear shift from being performed to a gear ratio higher than that required for decelerating the vehicle, and to prevent an unnecessary increase in the rotation speed of the engine 2. Moreover, the low gear shift allows the vehicle speed to be decelerated to the set vehicle speed.

[0052] Furthermore, 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.

[0053] When the speed ratio of the CVT 4 is held at the second speed ratio, an accelerator opening limit is set to converge the vehicle speed to a set vehicle speed. A target throttle opening is set according to the accelerator opening limit, and the electronic throttle valve 3 is controlled so that the throttle opening matches the target. This maintains the vehicle speed at the set vehicle speed.

[0054] The output of the engine 2 required when the vehicle is traveling downhill at a set speed is smaller than the output of the engine 2 required when the vehicle is traveling on a flat road at the set speed. Therefore, the accelerator opening limit set when the vehicle is traveling downhill at the set speed is smaller than the accelerator opening limit set when the vehicle is traveling on a flat road at the set speed. Due to this relationship, after the vehicle speed has decreased to the set vehicle speed, if the accelerator opening limit is less than a predetermined value, the low gear shift is not released, but is released when the accelerator opening limit is equal to or greater than the predetermined value. This allows the low gear shift to be released at the appropriate time after the vehicle moves from a downhill road to a flat road. Moreover, the low gear shift can be released at the appropriate time without using a sensor for determining the road gradient.

[0055] <Another example of low speed change execution determination processing> Fig. 6 is a flowchart showing another example of the low speed change execution determination process Fig. 5 is a diagram showing an example of the time change of the vehicle speed when the low speed change execution determination process shown in Fig. 6 is executed.

[0056] In order to determine whether or not to perform a low gear shift, which shifts the gear ratio of the CVT 4 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. 6 instead of the low gear shift execution determination process shown in FIG. 2.

[0057] In this low shift execution determination process, first, it is determined whether or not the vehicle speed has exceeded a set vehicle speed (step S41). While the vehicle speed is equal to or less 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 has exceeded the set vehicle speed.

[0058] If the vehicle speed exceeds the set vehicle speed (YES in step S41), the accelerator opening limit is set to 0. Then, in accordance with the setting of the accelerator opening limit, 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 S42).

[0059] When the throttle fully closed command is output (YES in step S42), the vehicle acceleration is calculated by time-differentiating the vehicle speed at the time when the throttle fully closed command is output (which approximately coincides with the time when the vehicle speed exceeds the set vehicle speed). Also, as in the process shown in Figure 2, the estimated time to reach the inflection point is calculated by adding the throttle delay time and the combustion stroke delay time.

[0060] Assuming the output of engine 2 is the same, the acceleration of the vehicle will be 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 close 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 close command is output until the estimated time to reach the inflection point has elapsed (when 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.

[0061] Therefore, if the increase in vehicle speed from the time when the throttle fully closed command is output until 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 value obtained by adding the predetermined value α to the set vehicle speed (YES in step S43), a decision is made to perform a low shift (step S44), 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 value obtained by adding the predetermined value α to the set vehicle speed (NO in step S43), a decision is made not to perform a low shift (step S45), and no low shift request is output from the ASL control unit 21.

[0062] <Effects> As described above, the execution of a low gear shift on a downhill road can be determined without using a sensor for determining the road gradient, even by the process shown in Fig. 6. As a result, the cost of the ASL system 1 can be reduced, and ultimately the cost of a vehicle equipped with the ASL system 1 can be reduced.

[0063] <Modification> Although the embodiment of the present invention has been described above, the present invention can be embodied in other forms.

[0064] 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 driving, 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 driving, as long as the vehicle is equipped with a transmission that changes the speed of power from the driving source for driving.

[0065] 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, a stepped automatic transmission (AT), or a manual transmission (MT).

[0066] In addition, various design modifications can be made to the above-described configuration within the scope of the claims. [Explanation of symbols]

[0067] 2: Engine (power source) 4: CVT (transmission) 11: EG / CVT-ECU (vehicle control unit)

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, In the control for the vehicle speed limiting function, 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; A vehicle control device that, when the gear ratio of the continuously variable transmission is shifted to the lower side in response to the vehicle speed exceeding the set vehicle speed, if the vehicle speed drops to the set vehicle speed as a result of the gear shift, sets the limit accelerator opening degree to converge the vehicle speed to the set vehicle speed, holds the gear ratio of the continuously variable transmission at the gear ratio at the time the vehicle speed dropped to the set vehicle speed until the output of the drive source becomes equal to or greater than the specified output, and frees the gear ratio of the continuously variable transmission when the output of the drive source becomes equal to or greater than the specified output.

2. 2. The vehicle control device according to claim 1, wherein the predetermined output is set to an output of the drive source when the vehicle runs on a flat road at the set vehicle speed.

Images