Vehicle control device

Abstract

To provide a control device for vehicle capable of preventing reduction in idle stop execution frequency, and capable of improving fuel economy.SOLUTION: A control device for vehicle which is mounted on a vehicle 1 which includes an engine 2, a starter 3 for starting the engine 2, a battery 4 for supplying power to the starter 3, and a battery voltage sensor 13 for detecting a voltage between terminals of the battery 4, and which bans idle stop in the case where the voltage detected by the battery voltage sensor 13 becomes below a threshold value TH in the period in which the engine 2 is started by the starter 3 includes: a start frequency count part 20 for counting the drive frequency of the starter 3; and a threshold value change part 21 for changing the threshold value TH according to the drive frequency counted by the start frequency count part 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 proposes a control method that references a first minimum value of battery voltage detected immediately after engine start, battery temperature, a second minimum value detected after the battery voltage reaches the first minimum value, and engine temperature, in order to ensure a restart after an idle stop while further improving fuel efficiency.The method determines a first threshold value to be compared with the first minimum value depending on the battery temperature, and determines a second threshold value to be compared with the second minimum value depending on the engine temperature.The method proposes a technology that permits the next idle stop if the first minimum value detected at the most recent engine start exceeds the first threshold value, the second minimum value detected at the most recent engine start exceeds the second threshold value, and the engine temperature is within a predetermined idle stop permitted temperature range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-74838 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional technologies such as that proposed in Patent Document 1 do not take into consideration battery degradation, and therefore may not permit idle stop even when the battery is in a state where restarting after idle stop is possible. As a result, conventional technologies have the problem of reducing the frequency with which idle stop is performed, which could result in a deterioration in fuel economy.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a vehicle control device that can prevent a decrease in the frequency at which idle stop is performed and improve fuel efficiency. [Means for solving the problem]

[0006] A vehicle control device according to the present invention is mounted on a vehicle having an engine, a starting device that starts the engine, a battery that supplies power to the starting device, and a battery voltage sensor that detects a voltage between the terminals of the battery, and prohibits an idle stop when the voltage detected by the battery voltage sensor falls below a threshold value while the engine is being started by the starting device, and includes: a start counting unit that counts the number of times the starting device is driven; and a threshold value changing unit that changes the threshold value in accordance with the number of times the starting device is driven. The threshold value changing unit decreases the threshold value as the number of times of driving counted by the start counting unit increases, and when the threshold value reaches a predetermined lower limit threshold value, maintains the threshold value at the lower limit threshold value regardless of the number of times of driving counted by the start counting unit. . [Effects of the Invention]

[0007] The present invention can provide a vehicle control device that can prevent a decrease in the frequency with which idle stop is performed and improve fuel economy. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with a vehicle control device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a conceptual diagram showing the relationship between the driving state of the starter and the terminal voltage of the battery in a vehicle equipped with a vehicle control device according to one embodiment of the present invention, where (a) shows the driving state of the starter and (b) shows the terminal voltage of the battery. [Figure 3] 3A and 3B are conceptual diagrams showing threshold maps in a vehicle control device according to one embodiment of the present invention, where (a) shows a first example of the threshold map and (b) shows a second example of the threshold map. [Figure 4]FIG. 4 is a flowchart showing the idle stop control operation of the vehicle control device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] A vehicle control device according to one embodiment of the present invention is mounted on a vehicle having an engine, a starting device that starts the engine, a battery that supplies power to the starting device, and a battery voltage sensor that detects the voltage across the battery, and prohibits idle stop when the voltage detected by the battery voltage sensor falls below a threshold while the engine is being started by the starting device, and is characterized by including: a start counting unit that counts the number of times the starter is driven; and a threshold changing unit that changes the threshold in accordance with the number of times the starter is driven. As a result, the vehicle control device according to the embodiment of the present invention can prevent a decrease in the frequency at which idle stop is performed and improve fuel efficiency. [Example]

[0010] A vehicle equipped with a vehicle control device according to an embodiment of the present invention will be described below with reference to the drawings.

[0011] As shown in FIG. 1, a vehicle 1 includes an engine 2, a starter 3, a battery 4, an alternator 5, and an ECU (Electronic Control Unit) 6.

[0012] The engine 2 is formed with a plurality of cylinders. In this embodiment, the engine 2 generates power by performing a series of four strokes for each cylinder, which are an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0013] In this embodiment, the engine 2 is described as using gasoline as fuel, but it may also use diesel or hydrogen as fuel. Also, the engine 2 may be a bi-fuel engine that can switch between two types of fuel, such as gasoline and LPG (Liquefied Petroleum Gas) or CNG (Compressed Natural Gas).

[0014] Power generated by the engine 2 is transmitted to drive wheels via a power transmission path that includes a transmission. In this embodiment, the transmission is configured by an AMT (Automated Manual Transmission).

[0015] The transmission may be a manual transmission such as an MT (Manual Transmission), or may be other automatic transmissions such as a CVT (Continuously Variable Transmission), an AT (Automatic Transmission), a DCT (Dual-Clutch Transmissions), and an AGS (Auto Gear Shift).

[0016] The starter 3 includes a motor and a pinion gear. When starting the engine 2, the starter 3 applies a rotational force to the engine 2 by meshing the pinion gear with the crankshaft of the engine 2 and rotating the motor, thereby rotating the crankshaft. In this embodiment, the starter 3 constitutes a starting device of the present invention.

[0017] The battery 4 is configured as a chargeable and dischargeable secondary battery, for example, a lead-acid battery capable of generating an output voltage of 12 V. The battery 4 supplies power to various electrical devices of the vehicle 1, including the starter 3. The various electrical devices of the vehicle 1 include an injector that injects fuel into the combustion chamber of the engine 2, a spark plug that ignites the combustion chamber of the engine 2, an air conditioning system, lighting equipment, etc.

[0018] The alternator 5 has a pulley that is connected to the crankshaft of the engine 2 via a belt. The alternator 5 generates electricity by converting the rotational force of the engine 2 transmitted to the pulley into electric power. The electric power generated by the alternator 5 is charged into the battery 4.

[0019] The ECU 6 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, input ports, and output ports.

[0020] The ROM of this computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the ECU 6. That is, the CPU executes the program stored in the ROM using the RAM as a work area, causing the computer unit to function as the ECU 6 in this embodiment.

[0021] Various sensors are connected to an input port of the ECU 6, including a vehicle speed sensor 10 that detects the vehicle speed, a brake stroke sensor 12 that detects the amount of operation of a brake pedal 11 (hereinafter simply referred to as "brake stroke"), a battery voltage sensor 13 that detects the voltage across the terminals of the battery 4, and an ignition switch (hereinafter simply referred to as "IG") 14. Various control targets are connected to an output port of the ECU 6, including the starter 3 and the injectors and spark plugs.

[0022] When the automatic stop condition is satisfied, the ECU 6 executes an idle stop to automatically stop the engine 2, and when the restart condition is satisfied, the ECU 6 restarts the engine 2. In this embodiment, when the restart condition is satisfied, the ECU 6 restarts the engine 2 by controlling the starter 3.

[0023] When determining whether the automatic stop condition is satisfied, the ECU 6 refers to the idle stop prohibition flag stored in the RAM. The idle stop prohibition flag indicates whether or not the execution of idle stop is prohibited.

[0024] When the idle stop prohibition flag is on, execution of idle stop is prohibited. When the idle stop prohibition flag is off, execution of idle stop is permitted. The ECU 6 initializes the idle stop prohibition flag to off when the IG 14 is turned off or when the IG 14 is turned on.

[0025] In this embodiment, when the engine 2 is in an operating state, the ECU 6 determines that the automatic stop condition is met when the idle stop prohibition flag is off, the vehicle speed detected by the vehicle speed sensor 10 is equal to or lower than a predetermined vehicle speed, and the brake stroke detected by the brake stroke sensor 12 is equal to or greater than a predetermined amount. The automatic stop condition described above is an example and is not limited to this.

[0026] Furthermore, the ECU 6 determines that the restart condition is met when the brake stroke detected by the brake stroke sensor 12 becomes less than a predetermined amount while the engine 2 is automatically stopped.

[0027] Figure 2 shows the relationship between the driving state of the starter 3 and the terminal voltage of the battery 4. The vertical axis of Figure 2(a) represents the driving state of the starter 3 (labeled "starting device" in the figure), the vertical axis of Figure 2(b) represents the terminal voltage of the battery 4 (labeled "battery voltage" in the figure), and the horizontal axis of Figures 2(a) and 2(b) commonly represents the passage of time.

[0028] In FIG. 2(b), the terminal voltage of the battery 4 when the degree of degradation of the battery 4 is low is indicated by a solid line, and the terminal voltage of the battery 4 when the degree of degradation of the battery 4 is high is indicated by a dashed line.

[0029] As shown in FIG. 2, during the period Te when the engine 2 is started by the starter 3 (hereinafter simply referred to as the "starter drive period"), the terminal voltage of the battery 4 drops due to an inrush current caused by driving the starter 3. At this time, the terminal voltage of the battery 4 during the starter drive period Te drops more when the degree of degradation of the battery 4 is high than when the degree of degradation of the battery 4 is low. In other words, the terminal voltage of the battery 4 during the starter drive period drops more significantly as the degradation of the battery 4 progresses. In other words, the more the degradation of the battery 4 progresses, the greater the amount of drop in the terminal voltage becomes, and the lower the minimum voltage at starting becomes.

[0030] Therefore, if the battery 4 deteriorates, the voltage detected by the battery voltage sensor 13 may fall below the threshold value TH during the starter driving period Te, even if the remaining capacity of the battery 4 is sufficient.

[0031] In this case, even if the remaining capacity of the battery 4 is sufficient, the voltage detected by the battery voltage sensor 13 may fall below the threshold value TH during the starter driving period Te, causing the idle stop prohibition flag to be turned on and idle stop to be prohibited.

[0032] Therefore, in this embodiment, the ECU 6 counts the number of times the starter 3 is driven (hereinafter simply referred to as the "starter drive count") and changes the threshold value TH in accordance with the counted number of times the starter is driven. In this way, the ECU 6 has the functions of a start counting unit 20 that counts the number of times the starter is driven, and a threshold value changing unit 21 that changes the threshold value TH in accordance with the number of times the starter is driven.

[0033] Also, assuming that the degree of deterioration of battery 4 is the same, when the remaining capacity of battery 4 is low, the voltage before the starter driving period will be low, and the minimum voltage at starting when the terminal voltage drops will be lower than when the remaining capacity of battery 4 is high.

[0034] Here, as described above, the voltage across the terminals of the battery 4 during the starter driving period Te drops significantly as the deterioration of the battery 4 progresses.

[0035] Therefore, in this embodiment, the ECU 6 decreases the threshold value TH as the counted number of times of driving increases. Furthermore, when the threshold value TH reaches a predetermined lower limit threshold value THmin, the ECU 6 maintains the threshold value at the lower limit threshold value THmin regardless of the counted number of times of driving.

[0036] Specifically, a map as shown in Fig. 3(a) is stored in advance in the ROM. The ECU 6 determines the threshold value TH by referring to the threshold value map stored in the ROM. In the threshold value map shown in Fig. 3(a), the vertical axis represents the threshold value TH, and the horizontal axis represents the number of times the starter is driven.

[0037] The threshold map shown in FIG. 3(a) is set so that the threshold value TH decreases as the number of times the starter is driven increases, and once the threshold value TH reaches the lower limit threshold value THmin, the threshold value TH is maintained at the lower limit threshold value THmin regardless of the number of times the starter is driven.

[0038] The lower limit threshold THmin is predetermined to be the minimum value that will not cause a power shortage for the various electrical devices of the vehicle 1 when the engine 2 is started due to deterioration of the battery 4 having progressed to the extent that replacement of the battery 4 is required.

[0039] It is also possible to set the lower limit threshold value THmin from the beginning, but in this case, even if the remaining capacity of the battery 4 is low, there is a possibility that the execution of idle stop will be permitted because the minimum voltage at startup will not fall below the threshold value TH, and it is therefore necessary to change the threshold value TH appropriately.

[0040] When the threshold value TH reaches the lower limit threshold value THmin, the ECU 6 may notify the occupant of the vehicle 1 by a lamp, a speaker, a display device, or the like provided on the instrument panel of the vehicle 1 to urge the occupant of the vehicle 1 to replace the battery 4.

[0041] The threshold map may be set so that the threshold value TH decreases as the number of times the starter is driven increases in a certain range of the number of times the starter is driven, depending on the characteristics of the battery 4. For example, as shown in FIG. 3(b), the threshold value map may be set so that the threshold value TH remains constant regardless of the number of times the starter is driven in a range where the number of times the starter is driven is small.

[0042] In addition, the threshold map may be set so that, in a certain range of the number of times the starter is driven, the threshold value TH decreases nonlinearly as the number of times the starter is driven increases, or may be set so that the threshold value TH decreases in stages as the number of times the starter is driven increases.

[0043] The number of times the starter has been driven is reset by the ECU 6 when a count reset button is pressed. The count reset button is provided on the vehicle 1 so that it can be pressed by a mechanic who has replaced the battery 4, but cannot be pressed by a passenger in the vehicle 1 in a normal operation. Therefore, the number of times the starter has been driven is not actually reset until the battery 4 is replaced.

[0044] The idle stop control operation by the ECU 6 configured as above will be described with reference to Fig. 4. The idle stop control operation described below is repeatedly executed while the ECU 6 is automatically stopping the engine 2.

[0045] First, in S1, the ECU 6 determines whether or not a start condition for the engine 2 is satisfied. In this embodiment, the ECU 6 determines that the start condition for the engine 2 is satisfied when a request to start the engine 2 is made by the IG 14 or when a restart condition is satisfied during idle stop.

[0046] If it is determined in S1 that the start conditions for the engine 2 are not met, the ECU 6 ends the idle stop control operation. If it is determined in S1 that the start conditions for the engine 2 are met, the ECU 6 executes the process of S2. If it is determined that the start conditions for the engine 2 are met, the ECU 6 starts the start of the engine 2 in parallel with executing the process of S2.

[0047] In S2, the ECU 6 updates the starter actuation count by adding 1 to the starter actuation count. After executing the process of S2, the ECU 6 executes the process of S3. In S3, the ECU 6 changes the threshold value TH in accordance with the actuation count updated in S2. After executing the process of S3, the ECU 6 executes the process of S4.

[0048] In S4, the ECU 6 determines whether or not the voltage detected by the battery voltage sensor 13 falls below the threshold value TH during the starter driving period. If it is determined in S4 that the voltage detected by the battery voltage sensor 13 is not below the threshold value TH, the ECU 6 ends the idle stop control operation.

[0049] If it is determined in S4 that the voltage detected by the battery voltage sensor 13 is lower than the threshold value TH, the ECU 6 executes the process of S5. In S5, the ECU 6 turns on the idle stop prohibition flag. After executing the process of S5, the ECU 6 ends the idle stop control operation.

[0050] As described above, the vehicle control device according to this embodiment counts the number of times the starter is driven, changes the threshold value TH according to the counted number of times the starter is driven, and prohibits idle stop if the terminal voltage of the battery 4 falls below the threshold value TH during the starter drive period. This prevents a decrease in the frequency with which idle stop is performed due to deterioration of the battery 4, thereby improving fuel efficiency.

[0051] Furthermore, the vehicle control device according to this embodiment reduces the threshold value TH as the number of times the starter is driven increases, so that the threshold value TH can be appropriately set according to the degree of deterioration of the battery 4.

[0052] In addition, the vehicle control device of this embodiment maintains the threshold value TH at the lower limit threshold value THmin once the threshold value TH reaches a predetermined lower limit threshold value THmin regardless of the number of times the starter is driven, thereby preventing various electrical devices of the vehicle 1 from suffering from a power shortage when the engine 2 is started.

[0053] In this embodiment, an example has been described in which the engine 2 is restarted by the starter 3. However, a vehicle equipped with a vehicle control device according to an embodiment of the present invention may be provided with an ISG (Integrated Starter Generator), and the ISG may restart the engine 2. In this way, the starting device of the present invention may be configured by the starter 3 and the ISG.

[0054] If the vehicle 1 is equipped with an ISG, the ECU 6 counts the number of times the ISG is driven in addition to the number of times the starter is driven, and changes the threshold value TH according to the counted number of times the ISG is driven. In this case, since the power consumption of the starter 3 and the ISG is different, the ECU 6 may weight the number of times the starter is driven and the number of times the ISG is driven before counting the number of times the starter is driven.

[0055] In such a configuration, when the voltage detected by the battery voltage sensor 13 falls below the threshold value TH during the starter driving period as well as during the period when the engine 2 is restarted by the ISG, the ECU 6 turns on the idle stop prohibition flag to prohibit idle stop.

[0056] Furthermore, in addition to the engine 2, the vehicle 1 may further be provided with a motor generator as a drive source for the vehicle 1. When the vehicle 1 is provided with a motor generator, the vehicle 1 is provided with a high-voltage battery that supplies and receives power to and from the motor generator, in addition to the battery 4. Therefore, the vehicle control device of this embodiment can also be applied to a vehicle provided with a motor generator as a drive source.

[0057] While the present invention has been disclosed by way of example, it will be apparent to those skilled in the art that modifications may be made thereto without departing from the spirit and scope of the invention, and it is intended that all such modifications and equivalents be included within the scope of the following claims. [Explanation of symbols]

[0058] 1 vehicle 2 engines 3 Starter (starting device) 4 Battery 13 Battery Voltage Sensor 20 Start count unit 21 Threshold change unit

Claims

[Claim 1] The engine and a starting device for starting the engine; a battery that supplies power to the starter; a battery voltage sensor for detecting a voltage between the terminals of the battery, A vehicle control device that prohibits an idle stop when a voltage detected by the battery voltage sensor falls below a threshold value while the engine is being started by the starter, a start counting unit that counts the number of times the starter device is driven; a threshold value changing unit that changes the threshold value in accordance with the number of times of driving counted by the start-up number counting unit, The threshold value changing unit The threshold value is decreased as the number of times of driving counted by the start number counting unit increases, A vehicle control device characterized in that, when the threshold value reaches a predetermined lower threshold value, the threshold value is maintained at the lower threshold value regardless of the number of times of driving counted by the start-up number counting unit.

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