JP2008030559A - Battery charging / discharging system for hybrid vehicle - Google Patents

Abstract

A self-discharge technology of an engine is used to completely discharge a high-voltage battery to recover the output voltage drop due to the memory effect.
A battery charging / discharging system 10 for a hybrid vehicle includes an engine 14, a motor / generator 16, a high voltage battery 22, a low voltage battery 24, an SOC monitoring unit 26, a discharging circuit 28, and a charging / discharging control unit 40. And the HVCPU 30 is configured. The charging / discharging control unit 40 instructs a complete discharge of the high-voltage battery 22 when the elapsed time after the complete discharge reaches a predetermined reference, and a progress monitoring module 42 that monitors the elapsed time from the previous complete discharge. And an autonomous start charge request module 46 that requests the HVCPU 30 to start the engine 14 autonomously and perform charging when there is a restart request of the engine 14 after complete discharge. The
[Selection] Figure 1

Description

  The present invention relates to a battery charge / discharge system for a hybrid vehicle, and more particularly to a battery charge / discharge system for a hybrid vehicle including a complete discharge of a high-voltage battery.

  As a battery mounted on a hybrid vehicle and used to supply driving energy to a motor / generator and regenerate braking energy, a rechargeable secondary battery such as a nickel metal hydride battery or a lithium ion battery is used. . And in order to ensure the voltage and current capacity which are required as a power supply for vehicles, these single cells are combined into an assembled battery and used as a predetermined high voltage battery. The chargeable high voltage battery is appropriately charged so that the state of charge / discharge of the battery called SOC (State of Charge) is monitored and the SOC is not lowered too much due to discharge to the load.

  Thus, since a high voltage battery repeats charging / discharging, for example, in a nickel metal hydride battery or a nickel cadmium battery, a memory effect is produced in which the output voltage decreases mainly in the SOC region used. As an example, when controlling charging / discharging in the range of 40% to 70% SOC, the output voltage in the SOC region gradually decreases by repeating charging / discharging, and in extreme cases, about 10% from the nominal value. It can happen that it falls. In order to recover the output voltage drop phenomenon due to the memory effect, it is known that complete discharge and complete charge are repeated several times.

  For example, in Patent Document 1, two power storage units are provided to prevent a decrease in power storage capacity due to the memory effect of a power storage device of a hybrid vehicle, and when one of the power storage units is completely discharged, the power storage amount SOC is predetermined. A configuration is disclosed in which when the value MC1 or less, the amount of charge SOC of the other power storage unit is maintained at a predetermined value MC2 or more, and the subsequent discharge of one power storage unit is executed.

  By the way, when complete discharge is performed, the high voltage battery does not have charging power, so that it is difficult to start the engine by the motor / generator. Therefore, attention is paid to a technique for autonomously starting the engine by fuel injection and ignition without receiving the starting assistance from the motor / generator. Even in the case of autonomous start, electric energy is used for ignition, but the power of a low-voltage battery, for example, a 12V battery is sufficient. Although it is not directly related to the complete discharge of the high voltage battery, the following techniques are known as autonomous engine starting techniques.

  For example, Patent Document 2 discloses an exhaust valve for a cylinder in an exhaust stroke when the engine is stopped as a method for improving startability when the engine is automatically stopped after idling or the like and then automatically restarted. It is in a closed state, fuel is supplied to it and forcibly ignited to reverse the piston, and fuel is supplied to the cylinder in the expansion stroke when the engine is stopped. It is disclosed that the cylinder that is in the expansion stroke in the subsequent stroke is started by supplying fuel, igniting, and burning.

  Also, in Patent Document 3, as a method for quick and quiet start in a cylinder injection internal combustion engine, a crankshaft is reversely rotated by a starter, and the combustion chamber of the cylinder that was in the latter half of the expansion stroke before starting the engine is compressed. It is disclosed to burn.

  Further, in Patent Document 4, as a method of obtaining a sufficient combustion torque when the expansion stroke cylinder is ignited even if the engine stop position varies, the piston of the fourth cylinder in the expansion stroke when the restart condition is satisfied is ATDC90. It is disclosed that control is performed by discriminating whether the vehicle is stopped between the position of 0 ° and the exhaust valve open position or whether it is stopped before the position of 90 ° ATDC. In the former state, the cylinder in the expansion stroke has a relatively large combustion chamber volume and sufficient air, so that the cylinder can be ignited to obtain a large combustion torque, and the engine can be rotated forward to start. it can. In the latter state, the volume of the combustion chamber is relatively small. At that time, the third cylinder in the compression stroke is ignited and the engine is reversed to compress the combustion chamber of the fourth cylinder, and then the cylinder is ignited. To do. It is stated that this allows a large combustion torque to be obtained and started.

JP 2003-348774 A JP 2004-301081 A Japanese Patent Laid-Open No. 2005-299481 JP 2006-46091 A

  If a complete discharge is performed in order to recover the output voltage drop due to the memory effect of the high voltage battery, the vehicle operation system cannot cope with the engine restart as it is. Therefore, in Patent Document 1, two power storage units are provided. Further, Patent Documents 2 to 4 are intended to improve engine startability, and there is no technical idea that links autonomous start with complete discharge of a high-voltage battery.

  An object of the present invention is to provide a battery charging / discharging system for a hybrid vehicle including a complete discharge of a high-voltage battery using an engine autonomous starting technology. Another object is to provide a battery charging / discharging system for a hybrid vehicle that includes a complete discharge when only one high voltage battery is provided. The following means contribute to at least one of these purposes.

  A battery charging / discharging system for a hybrid vehicle according to the present invention includes an engine and a rotating electrical machine as a drive source, a high voltage battery and a low voltage battery as a power source for the vehicle, and a control unit that controls charging / discharging of the high voltage battery, The control unit monitors the elapsed time or mileage since the last high discharge of the high voltage battery, and instructs the complete discharge when the time or distance exceeding the specified value has passed. When the engine restart request is received after completion of the engine, engine starting means for performing autonomous start of the engine using ignition by the low voltage battery, charging means for charging the high voltage battery by the started engine, It is characterized by having.

  In the battery charging / discharging system for a hybrid vehicle according to the present invention, it is preferable that the engine starting means performs an autonomous start of the engine when the SOC is a predetermined value or less.

  In the battery charging / discharging system for a hybrid vehicle according to the present invention, the engine starting means closes the exhaust valve of the cylinder in the exhaust stroke when the engine is stopped, supplies fuel thereto, and forcibly ignites by the low voltage battery. The piston is rotated in the reverse direction, and fuel is supplied to the cylinder in the expansion stroke when the engine is stopped. After the reverse rotation, the low-voltage battery forcibly ignites and burns to cause the piston to rotate forward, and the expansion stroke is performed in the subsequent stroke. It is preferable to start the cylinder with fuel supply, ignition with a low voltage battery, and combustion.

  With the above configuration, the high voltage battery monitors the elapsed time or mileage since the last complete discharge, commands complete discharge when the time or distance exceeds the specified value, and after complete discharge, When the restart request is received, the engine is autonomously started using ignition by the low voltage battery, and the high voltage battery is charged by the started engine. Thereby, even if there is a request for restarting the engine after complete discharge, the engine can be autonomously started using ignition of the low-voltage battery without using the power of the high-voltage battery. Therefore, even when only one high voltage battery is provided, the high voltage battery can be completely discharged, and the memory effect can be recovered.

  Further, the engine is autonomously started when the SOC is equal to or less than a predetermined value. As the predetermined value, it is preferable to select an SOC value at which the engine can be started even if traveling by the rotating electrical machine is impossible. This allows starting with a high voltage battery.

  In addition, as an autonomous start of the engine, the exhaust valve of the cylinder in the exhaust stroke is closed when the engine is stopped, fuel is supplied to this, and the piston is reversed by forcibly igniting with a low voltage battery, and the expansion stroke when the engine is stopped Fuel is supplied to the cylinder in the cylinder, and after the reverse rotation, the low-voltage battery forcibly ignites and burns the piston so that the piston rotates in the forward direction. Then, fuel is supplied to the cylinder that becomes the expansion stroke in the subsequent stroke. Execute the method of starting by doing. Thereby, even if there is a restart request for the engine after complete discharge, the engine can be autonomously started using the ignition of the low-voltage battery without using the power of the high-voltage battery.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, an autonomous engine starting method will be described in which ignition is performed by a low-voltage battery in accordance with Patent Document 2 described above. However, this is only an example, and other methods may be used to start the rotating electrical machine. Anything can be used as long as the engine is started without assistance. For example, a method that can be ignited by a low-voltage battery and can be autonomously started based on the techniques disclosed in Patent Documents 3 and 4 may be used. Further, in the engine autonomous start method, a four-cylinder four-cycle engine will be described in accordance with the above-mentioned Patent Document 2. However, an engine of any other type may be used as long as it has a configuration capable of autonomous start. I do not care.

  In the following, a motor / generator having both functions of an electric motor and a generator will be described as a rotating electric machine. However, other than this, a motor / generator function may be provided. Moreover, although a nickel metal hydride assembled battery will be described as the high voltage battery, other high voltage secondary batteries may be used that have a memory effect.

  FIG. 1 is a diagram illustrating a configuration of a battery charge / discharge system 10 of a hybrid vehicle. The battery charging / discharging system 10 of the hybrid vehicle includes an engine 14 and a motor / generator 16 as a drive source 12, a high-voltage battery 22 and a low-voltage battery 24 as a vehicle power source, and a charge / discharge state of the high-voltage battery 22. An SOC monitoring unit 26 for monitoring the SOC, a discharge circuit 28 for completely discharging the high-voltage battery 22, a charge / discharge control unit 40 for controlling charge / discharge, and a hybrid CPU (HVCPU) for controlling the operation of the entire hybrid vehicle 30 is comprised.

  The high-voltage battery 22 is a high-voltage secondary battery mounted on a hybrid vehicle. Specifically, the high-voltage battery 22 is an assembled battery by combining a plurality of nickel metal hydride cells. For example, a high voltage nickel metal hydride battery of about 200 V can be used by stacking 100 or more nickel metal hydride cells. The high voltage battery 22 stores electric energy generated when the motor / generator 16 functions as a generator by charging, and supplies electric energy by discharge as driving energy when the motor / generator 16 functions as an electric motor.

  The SOC monitoring unit 26 has a function of sequentially acquiring a charging current value and a discharging current value of the high-voltage battery 22, monitoring the SOC value as the charging / discharging state, and transmitting the SOC value to the charging / discharging control unit 40. . For example, 40% to 70% or the like is used as an appropriate SOC value range.

  The discharge circuit 28 is a circuit for discharging the high-voltage battery 22 and is generally used to equalize the charge / discharge state of each unit cell constituting the assembled battery. Used to execute. That is, since the nickel metal hydride battery is known to have a memory effect, the discharge of the high voltage battery 22 is executed by the discharge circuit 28 at appropriate intervals under the control of the charge / discharge control unit 40.

  The low voltage battery 24 is, for example, a 12V battery. The low voltage battery 24 is charged with low voltage direct current power converted from the power of the high voltage battery 22 using means such as a DC / DC converter. The low-voltage battery 24 is used as a power source for auxiliary equipment such as an air conditioner of the vehicle, and is used particularly as an ignition power source for the engine 14 here.

  The charge / discharge control unit 40 has a function of monitoring the SOC value of the high-voltage battery 22 and controlling the charge / discharge so that the charge / discharge state is within a predetermined SOC value range. Specifically, the SOC value of the high voltage battery 22 is acquired from the SOC monitoring unit 26, and the HVCPU 30 is notified of the necessity of charging or discharging of the high voltage battery 22 based on the acquired SOC value. The HVCPU 30 instructs to drive or regenerate the motor / generator 16 according to the information from the charge / discharge control unit 40, so that the SOC value falls within a predetermined range, for example, 40% to 70% in the above example. Control to fit.

  In addition, the charge / discharge control unit 40 has a function of performing charge / discharge control including complete discharge of the high-voltage battery 22 using the autonomous start of the engine 14 in particular. That is, after the complete discharge progress monitoring module 42 for monitoring the elapsed time from the previous complete discharge in order to periodically execute the complete discharge, and when the elapsed time from the previous complete discharge has reached a predetermined standard When there is a complete discharge command module 44 for instructing the discharge circuit 28 to completely discharge the high voltage battery 22 and a restart request of the engine 14 after the complete discharge, the HVCPU 30 autonomously starts the engine 14 to perform charging. And an autonomous start charging request module 46 for requesting.

  The charge / discharge control unit 40 can be configured by a control circuit or a computer, and its function can be integrated with the function of another control device mounted on the vehicle. For example, the function of the charge / discharge control unit 40 can be included in the function of the HVCPU 30. Moreover, each function of the charge / discharge control unit 40 can be realized by software, specifically, by executing a corresponding battery charge / discharge control program. Some of these functions may be realized by hardware.

  The HVCPU 30 has a function of controlling the operation of the entire hybrid vehicle as described above, but a function of controlling the driving and regeneration of the motor / generator 16 according to the information on the SOC value in relation to the charge / discharge control unit 40. Have And it has the function of the autonomous start module 32 especially, and controls the autonomous start of the engine 14 according to the request | requirement of the engine autonomous start of the charging / discharging control part 40. Below, the method of the autonomous start of the engine 14 is demonstrated.

  FIG. 2 is a diagram schematically illustrating the stroke and combustion operation of each cylinder when the four-cylinder four-cycle engine is normally operating. In FIG. 2, four cylinders in the vertical direction on the paper surface are designated No. 1 to No. These are arranged as 4, and the time change of the stroke is shown in the horizontal direction of the drawing. For example, no. When one cylinder is in the compression stroke, no. The second cylinder is in the expansion stroke. Similarly, at that time, no. The third cylinder is in the intake stroke. The fourth cylinder is in the exhaust stroke. Each cylinder repeats the process of compression-expansion-exhaust-intake-compression-expansion-exhaust as time elapses. In accordance with the stroke, the opening timing of the intake valve and the opening timing of the exhaust valve are also shown. In FIG. 2, T and B indicate the positions of the top dead center and the bottom dead center of the crank. In addition, the fuel injection timing 50 is indicated by a hatched rectangular pattern, and the ignition timing 52 is indicated by a spark pattern. As described above, in the normal operation, the fuel injection timing 50 is set to a time slightly after the top dead center of the intake stroke in which the intake valve is open, and the ignition timing 52 is the end of the compression stroke or the start of the expansion stroke. Is set at the point of time.

  FIG. 3 is a diagram for explaining timing control such as an exhaust valve, fuel injection, and ignition when autonomous start is executed for the four-cylinder four-cycle engine described in FIG. Here, it is assumed that the engine is idlingly stopped, and the state is the first state in FIG. That is, no. One cylinder is in the compression stroke. Two cylinders are in the expansion stroke. 3 cylinder is the intake stroke, No. Assume that 4 cylinders are in the exhaust stroke. To start the engine autonomously from this state, the following procedure is used. In FIG. 3, the procedures are arranged in the vertical direction on the paper surface in time series.

  First, the cylinder in the exhaust stroke when the engine is stopped is specified. Here, no. 4 cylinders. At that time, since the exhaust valve is open (S30), it is closed (S32). As a result, no. Since the four cylinders are made into compression cylinders, fuel is injected there and ignited by a low voltage battery (S34). As a result, the engine reverses (S36).

  Further, the cylinder in the expansion stroke is specified when the engine is stopped. Here, no. Two cylinders. Fuel is injected into this cylinder (S38), and the engine is ignited by the low voltage battery after the engine reverse rotation at S36 (S40). As a result, the engine rotates forward again (S42).

  Then, the cylinder in the expansion stroke is specified in the next cycle with reference to the time when the engine is stopped. This cylinder is in the compression stroke when the engine is stopped. One cylinder. Fuel is injected into this cylinder (S44), and ignition is performed by the low voltage battery at the timing of starting the expansion stroke by the normal rotation of S42, that is, at the same timing as the normal operation (S46). As a result, the ignition timing of the normal operation described with reference to FIG. 2 is the same. After that, if fuel injection and ignition are performed at the same timing as that of the normal operation, the engine operates smoothly after starting. Thus, the electric energy can be started autonomously using only the ignition of the low-voltage battery as the electric energy, without receiving the starting assistance of the motor / generator.

  The operation of the above configuration, particularly each function of the charge / discharge control unit will be described with reference to the flowchart of FIG. In addition, the code | symbol used in FIG. 1 shall be used about each element in the following description. FIG. 4 is a flowchart showing each procedure of battery charging / discharging of the hybrid vehicle, and each procedure corresponds to each processing procedure of the corresponding battery charging / discharging program.

  First, it is confirmed that the engine 14 is stopped. Next, it is determined how much time has elapsed from the time of the previous complete discharge to the current time (S10). This function is executed by the post-complete discharge progress monitoring module 42 of the charge / discharge control unit 40. The determination of progress can be made using several methods. One is the running time from the previous complete discharge. This is because in a hybrid vehicle, the travel time can be used as a measure of the charge / discharge frequency. The determination of the progress in this case can be made based on whether or not the travel distance from the previous complete discharge to the current time is equal to or greater than a predetermined travel distance reference value. The travel distance reference value can be set to 5000 km, for example. Another method is the time lapse from the previous complete discharge to the current time. This is because when the operation of the hybrid vehicle is performed at a stable frequency, the elapsed time can also be used as a guide for the frequency of charging and discharging.

  If it is determined in S10 that the progress after complete discharge is equal to or greater than the reference value, a complete discharge command is issued (S12). This function is executed by the complete discharge command module 44 of the charge / discharge control unit 40. Specifically, the discharge circuit 28 is instructed to cause the high voltage battery 22 to be completely discharged. The simplest complete discharge is to short-circuit each of the nickel metal hydride cells simultaneously. In general, discharge can be performed by a procedure such as discharging with an appropriate limiting resistor and decreasing the value of the limiting resistor sequentially. Then, the discharge process is continued until the complete discharge is completed (S14).

  When the complete discharge is completed, the process waits until a restart command is issued for the engine 14 (S16). If it is determined that an engine restart command has been issued, the SOC value at that time is confirmed. When full discharge is performed, the SOC value should be zero, but for some reason the SOC value may not be zero. Here, it is determined whether or not the SOC value is equal to or less than a predetermined value A (S18). The predetermined value A is not an SOC value that allows the motor / generator 16 to drive the vehicle, but can be set as an SOC value that allows the engine 14 to be started by the motor / generator 16. When the SOC value exceeds the predetermined value A in S18, the process proceeds to S22, and the engine 14 is started normally. That is, it is started by the motor / generator 16. The motor / generator 16 is driven by the started engine 14, and the electric energy generated thereby charges the high-voltage battery 22 (S24).

  When the SOC value is equal to or smaller than the predetermined value A in S18, the engine 14 is requested to start autonomously (S20). This function is executed by the autonomous start charge request module 46 of the charge / discharge control unit 40. Specifically, a request for engine autonomous start is issued to the HVCPU 30, and the timing command such as the exhaust valve, fuel injection, ignition by the low-voltage battery 24 described in FIG. Is executed against.

  After the engine starts autonomously, the motor / generator 16 is driven by the engine 14, and the electric energy generated thereby charges the high-voltage battery 22 (S24). Then, the vehicle continues to travel and the like (S26), returns to S10, the progress from the complete discharge of S14 is monitored, and the steps after S12 are thereafter repeated. In this way, the autonomous discharge of the engine is used to completely discharge the high voltage battery, and the memory effect caused by repeated charge and discharge of the high voltage battery, that is, the decrease in output voltage can be periodically recovered. it can.

It is a figure which shows the structure of the battery charging / discharging system of the hybrid vehicle in embodiment which concerns on this invention. It is a figure which illustrates typically the stroke and combustion operation of each cylinder at the time of operating normally in a 4 cylinder 4 cycle engine. It is a figure explaining timing control, such as an exhaust valve, fuel injection, and ignition, about the autonomous start of the engine used in the embodiment concerning the present invention. It is a flowchart which shows each procedure of the battery charge / discharge of the hybrid vehicle in embodiment which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Battery charging / discharging system of hybrid vehicle, 12 Drive source, 14 Engine, 16 Motor generator, 22 High voltage battery, 24 Low voltage battery, 26 SOC monitoring part, 28 Discharge circuit, 30 HVCPU, 32 Autonomous starting module, 40 charge Discharge control unit, 42 progress monitoring module after complete discharge, 44 complete discharge command module, 46 autonomous start charge request module, 50 fuel injection timing, 52 ignition timing.

Claims (3)

An engine and a rotating electric machine as drive sources;
A high voltage battery and a low voltage battery as a power source for vehicles;
A control unit that controls charging and discharging of the high-voltage battery;
With
The control unit
Means for monitoring the elapsed time or distance traveled since the last complete discharge of the high-voltage battery, and commanding complete discharge when the time or distance exceeding a specified value has elapsed;
Engine starting means for performing autonomous start of the engine using ignition by a low voltage battery when an engine restart request is received after complete discharge is completed;
Charging means for charging the high-voltage battery by the started engine;
A battery charging / discharging system for a hybrid vehicle characterized by comprising: In the battery charging / discharging system of the hybrid vehicle according to claim 1,
The engine starting means
A battery charging / discharging system for a hybrid vehicle, wherein the engine is autonomously started when the SOC is equal to or less than a predetermined value. In the battery charging / discharging system of the hybrid vehicle according to claim 1,
The engine starting means
When the engine is stopped, the exhaust valve of the cylinder that is in the exhaust stroke is closed, fuel is supplied to this, and the piston is reversely ignited by a low-voltage battery, and fuel is supplied to the cylinder that is in the expansion stroke when the engine is stopped Then, after the reverse rotation, the low-voltage battery forcibly ignites and burns the piston so that the piston rotates in the forward direction, and the cylinder that becomes the expansion stroke in the subsequent stroke is supplied with fuel, ignited and burned by the low-voltage battery, and started. A battery charging / discharging system for a hybrid vehicle.

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