JP5304625B2 - Automatic stop / start control device for internal combustion engine - Google Patents

Description

  The present invention provides at least one of assisting means for assisting steering and braking means for generating a braking force of a vehicle, an internal combustion engine as an in-vehicle main engine, a battery, the battery as a power source, and the internal combustion engine. And an initial rotation applying means for applying an initial rotation to the crankshaft. After the automatic stop process of the internal combustion engine, and after the automatic stop process, the initial rotation applying means is operated to operate the internal combustion engine. The present invention relates to an automatic stop / start control device for an internal combustion engine that performs an automatic start process.

  In vehicles in which an in-vehicle main engine is an internal combustion engine, for the purpose of reducing fuel consumption, a so-called idle stop function for automatically stopping the internal combustion engine under a predetermined operating condition is installed. In order to further improve the effect of reducing the fuel consumption by this automatic stop, it is proposed to perform an automatic stop process in a region where the traveling speed of the vehicle is greater than zero, as seen in Patent Document 1 below. .

JP 2006-161565 A

  By the way, when restarting the internal combustion engine after the automatic stop process of the internal combustion engine, if the starter performs a process of applying an initial rotation to the internal combustion engine, the battery voltage decreases as the starter starts. For this reason, during the period when the starter is operated, there is a concern that it may hinder the driving of the auxiliary device using the battery as a power source. In particular, after the automatic stop process is performed when the traveling speed of the vehicle is greater than zero, there is a process for applying an initial rotation to the internal combustion engine by the starter due to a request to restart the internal combustion engine before the vehicle stops. In the case where it is made, there is a concern that the driving of the auxiliary machine used for traveling of the vehicle may be hindered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine as a vehicle-mounted main engine, a battery, an initial rotation to the crankshaft of the internal combustion engine using the battery as a power source. The initial rotation applying means is applied to a vehicle, and after the automatic stop processing of the internal combustion engine, when the initial rotation applying means is operated to perform the automatic start processing of the internal combustion engine, there is a problem in driving the auxiliary machine. An object of the present invention is to provide an automatic stop / start control device for an internal combustion engine that can suitably suppress the occurrence of the failure.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

According to the first aspect of the present invention, at least one of assist means for assisting steering and braking means for generating braking force of the vehicle, an internal combustion engine as an in-vehicle main engine, a battery, and the battery as a power source And an initial rotation applying means for applying an initial rotation to the crankshaft of the internal combustion engine. The automatic rotation processing of the internal combustion engine, and after the automatic stop processing, the initial rotation applying means is operated. In the automatic stop / start control apparatus for an internal combustion engine that performs the automatic start process of the internal combustion engine, the at least one includes an electronically controlled actuator using the battery as a power source, and the automatic stop process is performed by a user by the user. on condition that the braking force is required, which traveling speed of the vehicle can be permitted even if greater than zero, the reed Maximum required voltage bets means and the braking means is, the higher the running speed is greater, based on the terminal voltage of the battery that is assumed when the energizing the initial rotation imparting means by the automatic starting process, the automatic and wherein the obtaining Bei variable means for variably setting to hinder the threshold value of the traveling speed to allow stopping processing on the at least one drive does not occur.

  The required maximum value of the change speed of the steering angle increases as the traveling speed increases. In addition, the maximum value of the braking force of the vehicle increases as the traveling speed increases. For this reason, it is considered that the required value of the terminal voltage of the battery as the power source of the assist means and the braking means increases as the traveling speed increases. In the above invention, in view of this point, the automatic stop process is executed by variably setting the threshold of the running speed at which the automatic stop process is permitted based on the battery terminal voltage assumed when the initial rotation applying means is energized. It is possible to prevent the assist means and the braking means from being hindered as much as possible while securing the opportunity to do as much as possible.

  According to a second aspect of the invention, in the first aspect of the invention, the variable means reduces the threshold value when the internal resistance of the battery is large.

  As the internal resistance increases, the amount of voltage drop in the internal resistance of the battery increases with energization of the initial rotation applying means, and thus the degree of decrease in the terminal voltage of the battery increases. In the above invention, in view of this point, the threshold is lowered when the internal resistance is large.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the variable means includes an internal resistance calculation means for calculating an internal resistance of the battery, and the threshold is set when the calculated internal resistance is large. It is characterized by lowering.

  As the internal resistance increases, the amount of voltage drop in the internal resistance of the battery increases with energization of the initial rotation applying means, and thus the degree of decrease in the terminal voltage of the battery increases. In view of this point, the above invention includes an internal resistance calculating means.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects of the present invention, the variable means may be configured such that the rush current flows when an inrush current flows with the start of power supply to the initial rotation applying means. It further comprises a minimum voltage predicting means for predicting the minimum voltage, and the threshold is lowered when the predicted minimum voltage is low.

  In the above-described invention, even when an inrush current flows along with the start of power supply to the initial rotation applying means, it is possible to make a setting that suitably suppresses troubles in driving the assist means and the braking means.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to third aspects, the variable means predicts a voltage of the battery during cranking by the initial rotation applying means. And means for lowering the threshold when the predicted cranking voltage is low.

  In the above-described invention, it is possible to make a setting that suitably suppresses the driving of the assist means and the braking means even during cranking by the initial rotation applying means.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the at least one and the battery are electrically connected without a converter. To do.

  In the above invention, since at least one of the assist means and the braking means is directly connected to the converter, this at least one power supply voltage is directly affected by the voltage drop of the battery. For this reason, the utility value of the variable means is particularly great.

1 is a system configuration diagram according to a first embodiment. FIG. The time chart which shows the behavior of the battery voltage accompanying starter starting. An equivalent loop circuit including a battery and a starter when starting starter energization. The flowchart which shows the procedure of calculation processes, such as internal resistance concerning the said embodiment. The flowchart which shows the procedure of the automatic stop process concerning the embodiment. The figure which shows the variable setting aspect of the threshold value of the vehicle travel speed concerning the embodiment. The figure which shows the effect of the same embodiment. The flowchart which shows the procedure of the automatic stop process concerning 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of an automatic stop / start control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a system configuration according to the present embodiment.

  As shown in the figure, the driving force of the internal combustion engine (engine 10) is transmitted to the drive wheels 14 via the automatic transmission 12 or the like. A braking force can be applied to the driving wheel 14 and the driven wheel 16 by a hydraulically driven brake actuator 20. In addition to the electric brake pump 22, the brake actuator 20 includes a holding valve for holding the pressure of hydraulic oil supplied to the wheel cylinder 24 for each wheel (each driving wheel 14 and each driven wheel 16). A pressure reducing valve for reducing the pressure of the hydraulic oil in the wheel cylinder 24 is provided. These valves are operated to perform automatic braking control that is performed independently of the brake operation of the user, such as anti-brake lock control (ABS), traction control control, and skid prevention control.

  The driven wheel 16 is a steering wheel, and the steering angle is operated by the electric power steering system 30. That is, the electric power steering system 30 includes a handle 31 and a power steering motor 32. Here, the power steering motor 32 is for assisting the operation of the handle 31.

  The auxiliary battery 40 is a power supply means for in-vehicle auxiliary equipment such as the brake pump 22 and the power steering motor 32. The auxiliary battery 40 is further connected to an alternator 36 as a charging means and a starter 38 for applying initial rotation to the engine 10. A DCDC converter 42 is connected to the auxiliary battery 40, and a navigation system 44, an audiovisual device 46, and the like are connected to the output side of the DCDC converter 42. The DCDC converter 42 is for suppressing the influence of the decrease in the terminal voltage of the auxiliary battery 40 on the navigation system 44 and the audiovisual device 46. The terminal voltage of the auxiliary battery 40 is set to a predetermined voltage (normal time). The voltage is assumed to be approximately the voltage assumed as the terminal voltage of the auxiliary battery 40) and output. An electronic control unit (ECU 50) is further connected to the auxiliary battery 40.

  The ECU 50 is a control device that controls the engine 10. The ECU 50 includes a wheel speed sensor 26 that detects the rotational speeds of the drive wheels 14 and the driven wheels 16, a brake sensor 52 that detects the presence or absence of a brake operation, a current sensor 54 that detects an output current of the auxiliary battery 40, and an auxiliary battery. The detection values of the voltage sensor 56 for detecting the terminal voltage 40 and the temperature sensor 58 for detecting the temperature of the auxiliary battery 40 are taken in. Based on these, the control amount of the engine 10 is controlled.

  In particular, the ECU 50 performs automatic stop start control (idle stop control) that automatically stops the engine 10 when a predetermined stop condition is satisfied and restarts the engine 10 when a predetermined restart condition is satisfied. In the present embodiment, it is assumed that the logical product of the stop condition being equal to or less than the threshold speed and that the brake operation is being performed (the user has requested the braking force of the vehicle) is true. However, when the automatic stop process is performed when the vehicle traveling speed is greater than zero, a restart request may occur before the vehicle stops. In this case, there is a concern that the operation of the electric power steering system 30 and the brake actuator 20 may be hindered when the terminal voltage of the auxiliary battery 40 decreases as the starter 38 is started. Therefore, in the present embodiment, the threshold speed is variably set based on the minimum voltage of the auxiliary battery 40 assumed when the starter 38 is started. This will be described in detail below.

  FIG. 2 shows the voltage fluctuation of the auxiliary battery 40 due to the starter 38 being activated. As illustrated, the terminal voltage of the auxiliary battery 40 decreases with the start of energization of the starter 38. Specifically, after decreasing to the lowest voltage Vbtm (time t1), it becomes about the cranking voltage Vc during the cranking period Tc, and increases to the voltage corresponding to the voltage immediately before the start of energization as the starter 38 is deenergized.

  Here, the minimum voltage Vbtm is a value when a large current (inrush current) flows through the starter 38 because no induced voltage is generated because the starter 38 is still in a stopped state. This current can be predicted by the equivalent circuit shown in FIG. FIG. 3 shows a circuit in which the internal resistance (resistance value Rb) of the auxiliary battery 40, the wiring resistance (resistance value Rh), and the resistance of the starter 38 (resistance value Rs) are connected in series. Here, when the open-circuit voltage V0 (voltage that does not include a voltage drop due to internal resistance) that is the electromotive force of the auxiliary battery 40 is used, the maximum energization current Imax of the starter 38 accompanying the start of energization of the starter 38 is When current does not flow from the battery 40 to other auxiliary machines, it becomes “V0 / (Rb + Rh + Rs)”. For this reason, if the resistance values Rb, Rh, and Rs can be calculated, the minimum voltage Vbtm can be predicted.

  FIG. 4 shows a procedure for calculating the resistance values Rb, Rh, and Rs. This process is repeatedly executed by the ECU 50 at a predetermined cycle, for example.

  In this series of processing, first, in step S10, voltage sampling before and after starting the starter 38 and current sampling synchronized with this are performed. In subsequent step S12, a resistance value Rb of the internal resistance is calculated. For example, this may be performed by dividing the change in the terminal voltage by the change in the discharge current of the auxiliary battery 40 as the starter 38 is started. Alternatively, for example, a method described in Japanese Patent Application Laid-Open No. 2007-223530 may be used. In the subsequent step S14, a combined resistance (Rh + Rs) of the wiring resistance and the resistance of the starter 38 is calculated. This can be calculated, for example, as “Vbtm = (Rh + Rs) · Imax” based on the current (maximum energization current Imax) that flows through the starter 38 when the terminal voltage of the auxiliary battery 40 becomes the minimum voltage Vbtm. When the process of step S14 is completed, this series of processes is once ended.

  FIG. 5 shows a procedure for automatic stop processing of the engine 10 according to the present embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle, for example.

  In this series of processes, it is first determined in step S20 whether or not the brake is on. If the brake is on, the resistance value Rb of the internal resistance is read in step S22. This process is a process of reading the resistance value Rb calculated in the process shown in FIG. 4 when the engine 10 is started last time. In subsequent step S24, the resistance value Rb of the internal resistance is corrected in accordance with the SOC and temperature TH of the auxiliary battery 40. Specifically, the resistance value Rb of the internal resistance is corrected based on changes in the SOC and temperature TH of the auxiliary battery 40 and the current SOC and temperature TH when the processing in step S10 of FIG. 4 is performed. This is because the resistance value Rb of the internal resistance depends on the SOC and temperature. The SOC is a physical quantity obtained by quantifying the discharge capacity of the auxiliary battery 40. Specifically, the ratio of the current charge amount to the full charge of the auxiliary battery 40 is quantified. The SOC is usually quantified by “5 hour rate capacity”, “10 hour rate capacity” or the like.

  In the subsequent step S26, assuming that automatic stop processing has been performed, the minimum voltage Vbtm of the auxiliary battery 40 when performing restart processing thereafter is predicted. Here, first, the current voltage V1 of the auxiliary battery 40 is divided by the sum “Rb + Rh + Rs” of the combined resistance (Rh + Rs) of the wiring resistance and the resistance of the starter 38 and the resistance value Rb of the internal resistance, thereby obtaining the starter 38. The maximum energization current Imax to is calculated. Here, the value calculated by the process shown in step S14 of FIG. 4 is used as the combined resistance. Based on the calculated maximum energization current Imax and the current terminal voltage V1 of the auxiliary battery 40, the minimum voltage Vbtm is predicted as “V1−Rb · Imax”.

  In the subsequent step S28, the traveling speed of the vehicle (vehicle speed SPv) is detected. For example, the detection value of the wheel speed sensor 26 may be used. Specifically, for example, the maximum value or the average value of the detection values of the wheel speed sensor 26 may be used. In a subsequent step S30, it is determined whether or not the vehicle speed Spv is equal to or less than a threshold speed SPth. This process is for determining whether or not to execute the automatic stop process. Here, as shown in FIG. 6A, the threshold speed SPth is decreased as the minimum voltage Vbtm is lower. Specifically, it may be lowered continuously as shown by a solid line in FIG. 6A, or may be lowered stepwise as shown by a broken line.

  As shown in FIG. 6 (b), the threshold speed SPth variable setting process increases the maximum required voltage of the electric power steering system 30 as the vehicle speed increases. As shown in FIG. 6 (c), the vehicle speed This is because the maximum required voltage of the brake actuator 20 is increased as the value is higher. That is, as the traveling speed increases, the maximum value of the rotational speed required for the power steering motor 32 to change the traveling direction increases, and thus the maximum required voltage increases. Further, as the traveling speed increases, the maximum value of the braking force required for the vehicle increases, so that the required maximum voltage increases. Here, as a request | requirement of braking force, there exists a request | requirement by the side slip prevention control at the time of changing a steering angle, for example. Further, for example, when a spark ignition type internal combustion engine or the like is adopted as the engine 12 and the user performs a brake operation in a state where the negative pressure of the engine 10 is reduced by the automatic stop process, there is a request generated for the brake actuator 20. is there.

  If an affirmative determination is made in step S30 of FIG. 5, the automatic stop process is executed in step S32. On the other hand, when a negative determination is made in steps S20 and S30, or when the process of step S32 is completed, this series of processes is temporarily terminated.

  According to the above process, even if the resistance value Rb of the internal resistance increases due to the aging of the auxiliary battery 40, it is possible to secure the execution opportunity of the automatic stop process as much as possible by reducing the threshold speed SPth. Become. That is, as shown in FIG. 7A, the minimum voltage Vbtm decreases as the usage period of the auxiliary battery 40 extends, but according to the present embodiment, as shown in FIG. As much as possible. On the other hand, when the minimum voltage Vbtm is equal to or higher than the threshold value as an execution condition for the automatic stop process, there is no problem in driving the brake actuator 20 and the electric power steering system 30 at a vehicle speed at which the automatic stop is permitted. Thus, it is necessary to set the threshold value as described above. Therefore, as shown in FIG. 7C, it is not possible to ensure a sufficient execution opportunity for the automatic stop process.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) The threshold speed SPth is variably set based on the terminal voltage of the auxiliary battery 40 assumed when the starter 38 is energized by the automatic start process. Thereby, it is possible to suppress the trouble of driving the electric power steering system 30 and the brake actuator 20 as much as possible while securing the opportunity to execute the automatic stop process as much as possible.

  (2) The minimum voltage Vbtm of the auxiliary battery 40 when an inrush current flows with the start of energization to the starter 38 is predicted, and the threshold speed SPth is reduced according to the predicted minimum voltage Vbtm. Thereby, even when an inrush current flows along with the start of energization of the starter 38, it is possible to make a setting that suppresses the driving of the electric power steering system 30 and the brake actuator 20 as much as possible.

  (3) The electric power steering system 30 or the brake actuator 20 and the auxiliary battery 40 are electrically connected without passing through the DCDC converter 42. In this case, since the electric power steering system 30 and the brake actuator 20 are directly affected by the voltage drop of the auxiliary battery 40, the utility value of the process of variably setting the threshold speed SPth according to the minimum voltage Vbtm is particularly great.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 8 shows a procedure of automatic stop processing according to the present embodiment. In the process shown in FIG. 8, the same step number is attached for convenience to the process corresponding to the process shown in FIG.

  In the present embodiment, the cranking voltage Vc shown in FIG. 2 is predicted in step S26a. This can be done by calculating the cranking current Ic. The cranking current Ic is a value obtained by subtracting the induced voltage E (the assumed value in this case) of the starter 38 from the current voltage V1 of the auxiliary battery 40, and a combined resistance (Rh + Rs) of the wiring resistance and the resistance of the starter 38. It is calculated by dividing by the sum “Rb + Rh + Rs” with the resistance value Rb of the internal resistance. Based on the cranking current Ic thus calculated and the current terminal voltage V1 of the auxiliary battery 40, the cranking voltage Vc is predicted as “V1−Rb · Ic”.

  Based on the cranking voltage Vc thus predicted, in step S30a, the threshold speed SPth is variably set by the cranking voltage Vc.

  According to the present embodiment described above, in addition to the effects according to the above (1) and (3) of the first embodiment, the following effects can be further obtained.

  (4) The voltage (cranking voltage Vc) of the auxiliary battery 40 during cranking by the starter 38 is predicted, and the threshold speed SPth is lowered when the predicted cranking voltage Vc is low. Thereby, even during cranking by the starter 38, it is possible to make a setting that suppresses the driving of the electric power steering system 30 and the brake actuator 20 as much as possible.

(Other embodiments)
Each of the above embodiments may be modified as follows.
<Minimum voltage prediction means>
The minimum voltage predicting means is not limited to that exemplified in the first embodiment. For example, the maximum battery voltage drop ΔV during the previous automatic start process may be subtracted from the current voltage of the auxiliary battery 40. Further, instead of using the current voltage of the auxiliary battery 40 as the voltage assumed in the automatic stop period, a value obtained by removing the terminal voltage change of the auxiliary battery 40 according to the current output current of the alternator 36 is obtained. It may be used. Further, the maximum decrease amount ΔV may be corrected according to at least one of the temperature of the battery 40 and the SOC for both the previous automatic stop process and the current time.
<Cranking voltage prediction means>
The cranking voltage predicting means is not limited to the one exemplified in the first embodiment. For example, the difference ΔV between the battery voltage at the time of cranking during the previous automatic start process and the battery voltage before starting the starter 38 may be subtracted from the current voltage of the auxiliary battery 40. Further, instead of using the current voltage of the auxiliary battery 40 as the voltage assumed in the automatic stop period, a value obtained by removing the terminal voltage change of the auxiliary battery 40 according to the current output current of the alternator 36 is obtained. It may be used. Further, the difference ΔV may be corrected according to at least one of the temperature of the battery 40 and the SOC for both the previous automatic stop process and the current time.
<Internal resistance calculation means>
As the internal resistance calculating means, as exemplified in the above embodiments, the means for calculating based on the combination of the detected value of the voltage of the auxiliary battery 40 before and after starting the starter 38 and the detected value of the current at the same time. Not limited to. For example, after the travel permission switch (ignition switch) of the vehicle is turned off, a process of reducing the current of the auxiliary battery 40 is performed, and a set of a detected voltage value before and after the reducing process and a detected current value at the same time In short, any means may be used as long as it is a means for calculating based on a set of the detected voltage value of the auxiliary battery 40 and the detected current value at the same time. However, the internal resistance is not limited to the one using the above set, and for example, the internal resistance is calculated by gradually increasing the internal resistance value as a reference in accordance with the vehicle travel distance from when the auxiliary battery 40 is replaced (at the time of product shipment). It may be a means.

Note that the resistance value Rb of the internal resistance this time is not limited to the one calculated by correcting the value previously calculated for both the SOC and the temperature TH, and is calculated by correcting one of them. It may be. Further, the previously calculated value may be used without correction.
<About variable means>
The variable means for variably setting the threshold value of the traveling speed for permitting the automatic stop process based on the terminal voltage of the battery assumed when the starter 38 is energized by the automatic start process is exemplified in the above embodiments. Not limited to things. For example, the threshold speed SPth may be variably set using the calculated resistance value Rb of the internal resistance as a direct input. Further, for example, the threshold speed SPth may be variably set using the vehicle travel distance from when the auxiliary battery 40 is replaced (when the product is shipped) as a direct input.

Further, the variable method of the threshold speed SPth is not limited to a multi-stage or continuously variable of two or more stages, and may be a variable setting in one stage, for example.
<Other>
The assist means for assisting steering is not limited to electric power steering. For example, in a configuration in which the mechanical connection between the steering wheel 31 and the steering wheel is interrupted, a so-called steering-by-wire system that operates the steering angle according to the operation of the steering wheel 31 may be used.

  In each of the above embodiments, both the brake pump 22 and the power steering motor 32 are directly connected to the auxiliary battery 40 (electrically connected without interposing a converter therebetween), but not limited thereto, at least one of them is a DCDC converter The auxiliary battery 40 may be connected via the terminal 42. Here, when both are connected to the auxiliary battery 40 via the DCDC converter 42, the influence of the voltage drop of the auxiliary battery 40 due to the starter 38 energization with respect to the supply voltage to both of them is alleviated by the DCDC converter 42. The However, even in this case, when the terminal voltage of the auxiliary battery 40 drops significantly, there is a concern that the output voltage of the DCDC converter 42 may be lowered, so that the application of the present invention is effective.

  -As a vehicle, it is not restricted to what has a distinction with a driving wheel and a driven wheel. Further, the steering wheel is not limited to the driven wheel 16.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 14 ... Drive wheel, 16 ... Drive wheel, 20 ... Brake actuator, 30 ... Electric power steering system, 40 ... Auxiliary battery, 50 ... ECU (one embodiment of an automatic stop start control device).

Claims (1)

At least one of assisting means for assisting steering and braking means for generating a braking force of the vehicle, an internal combustion engine as an in-vehicle main engine, a battery, the battery as a power source, and a crankshaft of the internal combustion engine The internal rotation engine is mounted on a vehicle having an initial rotation applying means for applying an initial rotation, and after the automatic stop process, the initial rotation applying means is operated to perform an automatic start process of the internal combustion engine. In the internal combustion engine automatic stop / start control device to perform,
The at least one includes an electronically controlled actuator using the battery as a power source,
The automatic stop process may be permitted even when the traveling speed of the vehicle is greater than zero, on condition that the braking force of the vehicle is requested by a user.
The maximum required voltage of the assist means and the braking means increases as the traveling speed increases.
Based on the terminal voltage of the battery assumed when the initial rotation applying means is energized by the automatic starting process, the threshold of the traveling speed for permitting the automatic stopping process is hindered in the at least one drive. the automatic stop and start control system for an internal combustion engine, wherein the obtaining Bei variable means for variably set not occur.

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