[19]
`United States Patent
`7
`Furutani et a1.
`[43] Date of Patent:
`Feb. 15, 1994
`
`[11] Patent Number:
`
`5,285,862
`
`lllllllllllllllllllllllllllIlllllllllllllllllllllllllllllllllllllllllllllll
`U8005285862A
`
`[54] POWER SUPPLY SYSTEM FOR HYBRID
`VEHICLES
`
`FOREIGN PATENT DOCUMENTS
`
`[75]
`
`Inventors: Masayuki Furutani, Susono;
`Yoshiyuki Nakamura; Ryoji Oki,
`both of Toyota, all of Japan
`
`[73] Assignee:
`
`Toyota Jidosha Xabushiki Kaisha,
`Aichi, Japan
`
`[21] Appl. No.: 28,182
`
`[22] Filed:
`
`Mar. 9, 1993
`
`Foreign Application Priority Data
`[30]
`Mar. 16, 1992 [JP]
`Japan ...............................'..... 4-58370
`Oct. 2, 1992 [JP]
`Japan .................................. 4-264798
`
`
`Int. Cl.5 ....... .
`[51]
`......... B601. 11/10; BGOL 11/18
`[52] US. Cl. .................................... ISO/65.4; 318/139
`[58] Field of Search .................... 180/652, 65.3, 65.4,
`ISO/65.8; 318/139
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,187,436 2/1980 Etienne ........................... 318/139 X
`4,306,156 12/1981 Monaco et a1. ............. 318/139 X
`
`4,313,080
`1/1982 Park .......................... 180/652 X
`
`4,923,025
`5/1990 Ellers ........................ 180/65.4 X
`5,212,431
`5/1993 Origuchi et al.
`.............. 180/65.4 X
`
`54-150031 12/1978 Japan .
`56-166704 12/1981 Japan .
`
`Primary Examiner—Margaret A. Focarino
`Assistant Examiner—Peter English
`Attorney, Agent, or Firm—Finnegan, Henderson,
`Farabow, Garrett, Dunner
`
`[57]
`
`ABSTRACT
`
`When voltage at the main battery 10 is lowered, an
`EV-ECU 36 instructs a starting motor 24 to rotate to
`actuate an engine 26 for the initiation of power genera-
`tion. At that time, the starting motor receives electric
`current mainly from a power capacitor 34, while an
`auxiliary battery 22 is connected to the ECU 36 and an
`ECU 38 so that supply voltages at the ECU’s 36 and 38
`can be kept at a predetermined level irrespective of the
`drive of the starting motor 24. Also, when the upstream
`voltage of the auxiliary battery 22 is found to be less
`than a predetermined value through a comparator 40,
`the drive of the starting motor is not effected. This
`configuration prevents the voltage at the auxiliary bat-
`tery 22 from continuing to be lowered due to the drive
`of the starting motor 24 in the case where the power
`capacitor 34 is in a poorly charged state.
`
`7 Claims, 7 Drawing Sheets
`
`20
`
`25
`
`-EI']
`
`STARTER ON/OFF INSTRUCTION
`
`
`
`
` NUMBER n 0F
`
`7 REVOLUTIONS
`
`}STARTER OFF
`INSTRUCTION
`
`Pagé 1 of 12
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`FORD 1144
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`

`

`US. Patent
`
`Feb. 15, 1994
`
`Sheet 1 of 7 ‘
`
`5,285,862
`
`202.0:sz—
`
`F.9".
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`Page 2 of 12
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`FORD 1144
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`US. Patent
`
`Feb. 15, 1994
`
`Sheet 2 of 7
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`5,285,862
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`Page 3 of 12
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`FORD 1144
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`US. Patent
`
`Feb. 15, 1994
`
`Sheet 3 on
`
`5,285,862
`
`POWER GENERATION ON/OFF TIMING
`
`ON
`
`s‘PomT b? POINT a
`I——“——t—————-.SOC
`o
`20
`50
`100 (yo)
`
`Fig. 3
`
`Page 4 of 12
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`US. Patent
`
`Feb. 15, 1994
`
`Sheet 4 of 7
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`5,285,862
`
`afifi
`
`q.9“.
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`Page 5 of 12
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`US. Patent
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`Feb. 15, 1994
`
`Sheet 5 of 7
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`5,285,862
`
`TO STARTING
`MOTOR
`
`FROM DC-DC
`
`CONVERTER
`
`TO ECU
`
`
`
`22
`
`
`
`ECU
`STARTER OFF
`INSTRUCTION
`
`Page 6 of 12
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`»
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`US. Patent
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`Feb. 15, 1994
`
`Sheet 6 of 7
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`5,285,862
`
`
`ON-OFF
`FROM ECU
`SWITCH
`
`FROM DC-DC
`CONVERTER
`
`TO ecu
`
`TO STARTING
`MOTOR
`
`
`
`
`
`
`22
`
`1
`
`+
`
`POWER
`
`\CAPAC-
`34non
`
`ECU
`STARTER OFF
`INSTRUCTION
`
`Pagé 7 of 12
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`"
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`

`US. Patent
`
`Feb. 15, 1994
`
`'
`
`Shgét 7 of7 '
`
`5,285,862
`
`HV TRAVELING
`
`STARTER OFF
`
`Pa9e8 of12
`
`’
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`FORD 1144 ‘
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`

`1
`
`5,285,862
`
`POWER SUPPLY SYSTEM FOR HYBRID
`'
`VEHICLES
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`
`5
`
`10
`
`15
`
`The present invention relates to a power supply sys-
`tem for use in a hybrid vehicle in which is mounted an
`engine for power generation as well as a drive motor for
`vehicle propulsion, and more particularly, is directed to
`a drive control of a starting motor for actuating the
`power generation engine.
`2. Description of the Related Arts
`A hybrid vehicle taking advantage of both the lower
`polluting properties peculiar to an electric vehicle and
`the continuous traveling performance associated with
`an engine powered vehicle has been hitherto proposed.
`This type of hybrid vehicle usually travels as an electric
`vehicle through the drive of a motor by electric power
`derived from a main battery. Furthermore, the state of 20
`charge (hereinafter, abbreviated to SOC) of the battery
`is monitored during traveling. When the SOC becomes
`less than a predetermined lower level, the engine is
`actuated and the vehicle travels while performing
`power generation. Thus, the main battery is charged 25
`with electric current produced by a power generator.
`When the SOC is restored to a predetermined higher
`level, the engine is stopped and the hybrid vehicle is
`allowed to travel as an ordinary electric vehicle.
`In this manner, the hybrid vehicle also includes an 30
`engine which is driven exclusively for the purpose of
`charging the battery and hence is operated under a fixed
`load and a fixed number of revolutions. Therefore, un-
`like the engine vehicle using the engine as its drive
`source, there can be realized decreased noise generation
`and much lower contaminant content in the exhaust gas
`(Refer to Japanese Patent Laid-open Publication No.
`56166704, for example).
`The hybrid vehicle is commonly equipped with an
`auxiliary battery which provides electric power to an
`electronic control unit
`(hereinafter abbreviated as
`. ECU) which carries out a variety of control functions
`such as control of motor driving conditions and engine
`starting control, and to accessories such as headlights.
`The auxiliary battery is adapted to receive electric
`power from the main battery with the aid of a DC—DC
`converter.
`'
`
`35
`
`45
`
`This auxiliary battery is intended to supply electric
`power to a starting motor for starting the engine as well.
`For the drive of the starting motor, the auxiliary battery
`is required to consume the largest amount of electric
`power. As described above, the actuation of the engine
`is carried out depending on the SOC of the main bat-
`tery. It is therefore ordinarily impossible to control the
`timing of driving the motor. As a result, the voltage at
`the auxiliary battery may be disadvantageously substan-
`tially lowered when it has been already lowered due to
`turning on' headlights and windshield wipers at night or
`under rainy weather, or when the starting motor is
`continuously driven due to failing to actuate the engine.
`Hence, there arose a problem that the ECU malfunc-
`tions in the case where the voltage at the auxiliary bat-
`tery is substantially lowered, which results in a poor
`supply of electric power into the motor.
`
`SUMMARY OF THE INVENTION
`
`50
`
`55
`
`65
`
`The present invention was conceived to overcome
`the above problems, of the object is to provide a power
`
`2
`supply system for a hybrid vehicle capable of securely
`preventing a malfunction of an ECU.
`In order to accomplish the above object, the power
`supply system for a hybrid vehicle according to a first
`aspect of the present invention comprises a drive power
`supply for driving the drive motor; a starting motor for
`the actuation of the engine; a first power supply means
`which receives electric power from the drive power
`supply and provides electric power to the starting mo-
`tor; a control section which receives electric power
`from the drive power supply and controls the drive of
`the starting motor; and a second power supply means
`which is connected between the drive power supply
`and the control section in parallel with the control sec-
`tion and maintains supply voltage at the control section.
`A power supply system for a hybrid vehicle accord-
`ing to a second aspect of the present invention com-
`prises a drive power supply for driving the drive motor;
`a starting motor for the actuation of the engine; a first
`power supply means which receives electric power
`from the drive power supply and provides electric
`power to the starting motor; a control section which
`receives electric power from the first power supply
`means and controls the drive of the starting motor; a
`second power supply means which is connected be-
`tween the first power supply means and the control
`section in parallel with the first power supply means
`and maintains supply voltage at the control section; and
`an isolation means for separating the control section and
`the second power supply means from the first power
`supply means at the time of operation of the starting
`motor.
`
`In a supply system for a hybrid vehicle according to
`a third aspect of the present invention, at least one of the
`first and second power supply means comprises a bat-
`tery.
`In a power supply system for a hybrid vehicle ac-
`cording to a fourth aspect of the present invention,
`there is further provided a voltage detection means for
`detecting supply voltage at the control section, and the
`control section prohibits the drive of the starting motor
`in the case where the supply voltage at the control
`section detected by the voltage detection means is less
`than a predetermined value.
`In this manner, the present invention includes a cou-
`ple of power supply means consisting of a first supply
`means for providing electric power to a starting motor
`and a second power supply means for maintaining sup-
`ply voltage at a control section. Due to such construc-
`tion, the operation of the starting motor is exclusively
`carried out by electric power derived from the first
`power supply means so that supply voltage at the con—
`trol section can be maintained during the operation of
`the starting motor, thereby preventing a malfunction of
`the control section.
`
`Furthermore, the present invention may include an
`isolation means disposed between the first power supply
`means and the second power supply means. Due to such
`construction, the control section and the second power
`supply means are separated from the first power supply
`means by virtue of the isolation means during the opera-
`tion of the starting motor while maintaining the supply
`voltage at the control section by the second power
`supply means. Accordingly, the supply voltage at the
`control section can be maintained even though the volt-
`age at the first power supply means is temporarily
`caused to be lowered, to consequently prevent the con-
`
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`3
`trol section from malfunctioning. Moreover, in a case
`where the supply voltage at the control section is less
`than a predetermined value, the drive of the starting
`motor is prohibited for further secure prevention of a
`drop in supply voltage at the control section.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram illustrating an overall con-
`figuration of an embodiment of the present invention;
`FIG. 2 is a block diagram depicting an overall config-
`uration of another embodiment thereof;
`FIG. 3 is an explanatory diagram showing timing of
`start and stop of power generation;
`FIG. 4 is a block diagram illustrating an overall con-
`figuration of a variant of the embodiment shown in
`FIG. 1;
`FIG. 5 is a block diagram illustrating a partial config-
`uration of a further embodiment of the part enclosed by
`a chain line in FIG. 2;
`FIG. 6 is a block diagram illustrating a partial config-
`uration of a still further embodiment of the part en-
`closed by a chain line in FIG. 2; and
`FIG. 7 is a flowchart for explaining the operation at
`the time of actuating an engine.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Embodiments of the present invention will now be
`described with reference to the accompanying draw-
`ings. FIG. 1 is a block diagram illustrating an overall
`configuration of an embodiment. A main battery 10 is
`connected through an inverter 12 to an altemating-cur-
`rent induction motor 14. Direct-current power derived
`from the main battery is converted into three-phase
`altemating-current and supplied to the motor 14 which
`in turn drives a vehicle.
`
`The main battery 10 is further connected through a
`DC to DC converter 20 to a power capacitor 34 acting
`as a first power supply means, so that the power capaci-
`tor 34 can be charged with the current delivered from
`the main battery 10. Incidentally, the voltage of the
`main battery 10 is ordinarily in the order of 100V, while
`voltage of the power capacitor 34 is about 12V.
`The power capacitor 34 is connected to a starting
`motor 24 which is mainly driven by electric current
`supplied from the power capacitor 34. A rotational
`shaft of the starting motor 24 is drivingly connected to
`an engine 26 for starting. The engine 26 is linked
`through a speed reducer 28 to an electric generator 30
`so that the rotation of the engine 26 can cause electric
`power within the generator 30. The output of the gener-
`ator 30 is connected to the main battery 10 so that the
`latter can be charged with electric power produced by
`the generator 30.
`.
`The main battery 10 is further connected through the
`DC to DC converter 20 to an auxiliary battery 22 acting
`as a second power supply means, and then to an Electric
`Vehicle-Electronic Control Unit (EV-ECU) 36 and an
`Engine-Electronic Control Unit (E/G-ECU) 38 each
`serving as a control section. Thus, the electric power
`arising from the main battery 10 allows the EV—ECU 36
`and E/G-ECU 38 to operate. Voltages at power
`supplies of the EV~EC S6 and E/G-ECU 38 each being
`connected to the main battery 10 are intended to be
`maintained by the auxiliary battery 22.
`Therefore, at the time of actuation of the starting
`motor 24, electric power for driving the starting motor
`24 is mainly supplied from the power capacitor 34,
`
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`while the supply voltages of the EV-ECU 36 and E/G-
`ECU 38 are kept unvaried by virtue of the auxiliary
`battery 22, to thereby prevent malfunction of the con-
`trol sections.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`FIG. 2 is a block diagram illustrating a complete
`configuration of another embodiment of the present
`invention. In FIG. 2, constituent elements correspond-
`ing to those in FIG. 1 are designated by reference nu-
`merals identical with those used in FIG. 1. FIG. 2 de-
`picts an auxiliary battery 22 acting as a first power
`supply means, a power capacitor 34 serving as a second
`power supply means, and a main battery 10 being con-
`nected through a DC to DC converter 20 to the auxil-
`iary battery 22 acting as the first power source means. A
`starting motor 24 is thus driven by electric current de-
`rived from the auxiliary battery 22.
`By way of a diode 32 functioning as an isolation
`means, the auxiliary battery 22 is connected to the
`power capacitor 34, and then to an EV-ECU 36 and an
`E/G-ECU 38 each acting as a control section. Accord-
`ingly, electric power arising from the auxiliary battery
`22 causes the EV-ECU 36 and the E/G-ECU 38 to
`operate. Furthermore, voltages at power supplies of the
`EV-ECU 36 and the E/G-ECU 38 each being con-
`nected through the diode 32 to the auxiliary battery 22
`are maintained by the power capacitor 34. Hence, even
`if the voltage at the auxiliary battery 22 undesirably
`drops, the electric current is not permitted to flow from
`the power capacitor 34 toward the auxiliary battery 22
`due to the presence of the diode 32. As a result, supply
`voltages of the EV-ECU 36 and the E/G-ECU 38 are
`kept unvaried with the aid of the power capacitor 34,
`thereby preventing the control sections from malfunc-
`tioning.
`Moreover, it is preferable in the above embodiments
`as shown in FIG. 1 and FIG. 2 that the upstream volt-
`age of the second power supply means, that is, the sup-
`ply voltage at the ECU’s 36 and 38, is applied to a com-
`parator 40 acting as a voltage detection means in com-
`parison with a predetermined reference voltage Vref.
`Then, a signal representing the result of comparison
`effected by the comparator 40 is supplied to the EV-
`ECU 36. In addition, an SOC meter 25 is connected to
`the main battery 10 so as to supply a signal representing
`a state of charge of the main battery 10 to the EV-ECU
`36. Besides, the EV—ECU 36 also receives a signal rep-
`resenting a number n of revolutions of the engine 26.
`In such an arrangement, during ordinary traveling,
`electric current arising from the main battery 10 is sup-
`plied through the inverter 12 to the motor 14 whose
`rotation is used to drive an electric vehicle. In other
`words, the inverter 12 is controlled by the EV-ECU 36
`in response to the state of depressing an accelerator, to
`rotate the motor 14 at a corresponding rotational speed.
`The state of charge of the main battery 10 is moni-
`tored at all times by the SOC meter 25 and the EV-ECU
`36 controls the charging into the battery 10 in such a
`manner that the SOC of the main battery is always
`within a predetermined range. As seen in FIG. 3, when
`the SOC reaches, for example, 20% (point b), the gener-
`ation of electrical energy (charging) ‘is initiated to
`thereby charge the main battery 10. When the SOC
`rises to 50% (point a), the generation of electricity is
`terminated. Hence, the SOC of the main battery 10 is
`usually set to lie within the range 20 to 50%. It is to be
`noted that the reason to impart a hysteresis to the on-off
`control of the power generation is to reduce the number
`of times starting the engine 26. Also, the values of the
`
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`5,285,862
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`5
`SOC at the time when the power generation is started
`and stopped are not limited to the above-mentioned
`one, but may lie within a range 20 to 80%. In order to
`assure an effective reception of charging current which
`may be supplied into the main battery 10 due to regener-
`ative braking, the SOC on charging is to be less than
`100%. Moreover, if the SOC is entirely discharged to
`0%, it is impossible for the vehicle to travel, and ac-
`cordingly the generation of electrical energy may be
`initiated prior to the completion of discharge.
`A variant of the embodiment shown in FIG. 1 is
`illustrated in FIG. 4 where a first and a second power
`supply means both comprise an auxiliary battery 22, and
`an ON-OFF switch 42 acting as an isolation means is
`interposed between the two power supply means and
`connected thereto.
`At the time of non-drive of a starting motor 24, the
`ON-OFF switch 42 is closed to charge the auxiliary
`battery 22 acting as the first power supply means, while
`supply voltages at an EV-ECU 36 and an E/G-ECU 38
`are maintained by the other auxiliary battery 22 acting
`as the second supply means.
`While on the contrary, at the time of drive of the
`starting motor 24, the OFF-OFF switch 42 is opened
`under an instruction issued from the EV-ECU 36 so as
`to separate the auxiliary battery 22 acting as the first
`power supply means and the starting motor 24 from the
`ECU’s 36 and 38, thereby preventing the supply volt-
`ages at the ECU’s 36 and 38 from being lowered due to
`a voltage drop of the auxiliary battery 22 acting as the
`first power supply means.
`FIGS. 5 and 6 illustrate further embodiments, respec-
`tively, of the area enclosed by a chain line in FIG. 2.
`FIG. 5 shows an embodiment where an auxiliary bat-
`tery 22 and an power capacitor 34 acting as a first and
`a second power supply means, respectively, are inter-
`changed with each other. In this embodiment, a starting
`motor 24 is driven by electric current derived from the
`power capacitor 34, while an EV-ECU 36 and an E/G-
`ECU 38 are" operated by electric current from the auxil-
`iary battery 22 having larger capacity than the power
`capacitor 34. This configuration ensures more stabilized
`supply voltages at the ECU’s 36 and 38.
`In the above-described embodiment, one of the first
`and second power supply means is the auxiliary battery
`and the other is the power capacitor, but instead, both
`the power supply means may comprise the auxiliary
`battery in the same manner as the embodiment shown in
`FIG. 4.
`
`FIG. 6 depicts an embodiment employing as an isola-
`tion means an ON-OFF switch 42 in place of a diode S2.
`The ON-OFF switch 42 is the same as that used in the
`FIG. 4 embodiment. With the ON-OFF switch 42 being
`ordinarily closed, an EV-ECU 36 and an E/G-ECU 38
`are operated by electric current derived from an auxil-
`iary battery 22. On the other hand, at the time of drive
`of a starting motor 24, the ON-OFF switch 42 is opened
`in compliance with an instruction issued by the EV-
`ECU 36 so as to separate the ECU’s 36 and 38 and a
`power capacitor 34 from the auxiliary battery 22. In this
`case, the ECU’s 36 and 38 are operated only by virtue of
`the current from the power capacitor 34, and accord-
`ingly, a temporary drop in the voltage at the auxiliary
`battery 22 arising from the actuation of the starting
`motor 24 does not lead to a drop in the supply voltages
`at the ECU’s 36 and 38.
`
`Referring next to FIG. 7, the operation of initiating
`power generation will be described with respect to the
`
`6
`embodiment shown in FIG. 2. An ignition key is first
`switched on (81). When the vehicle is in operating
`mode, the EV-ECU 36 receives a detection value from
`the SOC meter 25 to judge whether it is less than 20%
`or not (82). With the SOC not less than 20%, there is no
`necessity for charging, and hence the motor 14 is driven
`by electric power derived from the main battery 10
`without performing power generation, to thereby allow
`traveling as an ordinary electric vehicle (EV) (S3).
`While on the contrary, with the SOC less than 20%,
`the EV-ECU 36 receives a detection result from the
`
`comparator 40 to judge whether the upstream voltage
`Va of the power capacitor 34 acting as the second
`power supply means exceeds the reference value Vref
`or not (S4). Providing that the supply voltage Va is less
`than the reference voltage Vref, the power of the DC to
`DC converter 20 is upped without driving the starting
`motor 24 (SS). In other words, the fact that the voltage
`Va on the upstream side of the power capacitor 34 is
`less than the predetermined value implies a presence of
`a lower voltage at the auxiliary battery 22 acting as the
`first power supply means. Therefore, if the starting
`motor 24 is driven under these conditions, the voltage at
`the auxiliary battery 22 will be subjected to a further
`drop. For this reason, during the drive of the starting
`motor 24, current supply to the power capacitor 34 is
`not carried out. Accordingly, the upstream voltage of
`the power capacitor 34 will be further lowered due to
`the current supply to the ECU’s 36 and 38. In the case
`where the voltage Va does not reach the minimum
`compensation voltage for the operation of the ECU’s 36
`and 38, predetermined operations thereof are not to be
`expected. In this embodiment, therefore, the power of
`the DC-DC converter 20 is upped to increase the quan-
`tity of charging to the auxiliary battery 22, thereby
`restoring the voltage at the auxiliary battery 22. The
`restoration of the voltage at the auxiliary battery 22
`results in a current supply to the power capacitor 34,
`thus restoring the upstream voltage Va of the power
`capacitor 34 exceeding the reference voltage Vref.
`While on the contrary, if the voltage Va is more than
`the reference voltage Vref, the power capacitor 34 is in
`a fully charged condition, and hence the starting motor
`is turned on (S6). That is, the starting motor 24 is driven
`by the power supply from the auxiliary battery 22 to
`actuate the engine 26. In this case, although the actua-
`tion of the starting motor 24 may bring about a drop in
`voltage at the auxiliary battery 22, the presence of the
`diode 32 serving as an isolation means prevents the flow
`of electric current from the power capacitor 34 toward
`the auxiliary battery. As a result, the electric power
`being accumulated within the power capacitor 34 main-
`tains the supply voltages at the ECU’s 36 and 38 so as to
`prevent a malfunction of the ECU’s 36 and 38. This
`necessitates the power capacitor 34 having sufficient
`capacity to operate the ECU’s 36 and 38 for a period of
`time corresponding to one drive period for the ordinary
`starting motor.
`Then, whether a given period of time tufhas elapsed
`(S7), and whether the number of revolutions of the
`engine 26 has reached a given reference number nmfof
`revolutions are judged. The reference number it"; is
`provided for judging whether the engine has started or
`not. The number of revolutions of the engine 26 exceed-
`ing the reference number of revolutions signifies that
`the engine has started. Unless the reference number of
`revolutions has been accomplished, the procedure re-
`turns to S6 by way of S4 to continue the rotation of the
`
`5
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`10
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`15
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`20
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`25
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`30
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`
`7
`starting motor. 0n the other hand, the lapse of the per-
`iod of time exceeding the reference period of time Infill
`S7 signifies that the engine has not yet started in spite of
`the rotation of the starting motor 24 during the period
`of time exceeding the reference period of time. Hence,
`the starting motor is deenergized (S9), and the power of
`the DC to DC converter 20 is upped (SS) to enable the
`hybrid vehicle to travel as an electric vehicle (S3).
`While on the contrary, providing the number n of
`revolutions of the engine surpasses the reference num-
`ber nrefin $8 and the engine 26 has started up, the start-
`ing motor 24 is switched off ($10) to actuate the engine
`while supplying the electric power from the power
`generator 30 to the main battery 10 for traveling (511).
`Then, the power of the DC-DC converter 20 is restored
`to its original level (812).
`In this manner, the traveling as a hybrid powered
`vehicle while performing power generation contributes
`to a restoration of the SOC of the main battery 10.
`Accordingly, when the SOC of the main battery 10 has
`reached a predetermined value as described above, the
`EV-ECU 36 issues an engine stop instruction to the
`E/G-ECU 38 which in turn brings the engine 26 to a
`standstill.
`
`According to the arrangement of this embodiment,
`thus, in the case of lower supply voltages at the ECU’s
`36 and 38, the starting motor 24 is not allowed to be
`furnished with electric current, thereby preventing the
`supply voltages at the ECU’s 36 and 38 from being
`lowered to a level below the predetermined value. Fur-
`thermore, the increase of electric charge to be accumu-
`lated in the auxiliary battery 22 in this case makes it
`possible to restore the voltage at the auxiliary battery,
`thereby driving the starting motor 24 to ensure hybrid
`vehicle traveling. Thus, the SOC of the main battery 10 _
`is capable of being properly restored.
`As detailed hereinabove, a power supply apparatus
`for a hybrid vehicle according to the present invention
`comprises a couple of power supply means consisting of
`a first power supply means for providing electric power
`to the starting motor and a second power supply means
`for maintaining the supply voltage at the control sec-
`tion, and an optional isolation means for keeping the
`supply voltage at the control section within a predeter-
`mined range, thereby preventing a drop in voltage at
`the control section during the supply of electric power
`into the starting motor. Also, if the supply voltage at the
`control section is below the predetermined value, the
`drive of the starting motor is prohibited to place a fur.
`ther reliable restraint on the drop in the supply voltage
`at the control section.
`What is claimed is:
`
`40
`
`4s
`
`50
`
`55
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`8
`a first power supply means which receives electric
`power from said drive power supply and provides
`electric power to said starting motor;
`a control section which receives electric power from
`said drive power supply and controls the drive of
`said starting motor; and
`a second power supply means which is connected
`between said drive power supply and said control
`section in parallel with said control section and
`maintains supply voltage at said control section.
`2. A power supply system for a hybrid vehicle ac-
`cording to claim 1, further comprises an isolation means
`for separating said starting motor and said first power
`supply means from said control section and said second
`power supply means at the time of operation of said
`starting motor.
`3. A power supply system for a hybrid vehicle ac-
`cording to claim 1, further comprising a voltage detec-
`tion means for detecting supply voltage at said control
`section, wherein
`said control section prohibits the drive of said starting
`motor in the case where said supply voltage at said
`control section detected by said voltage detection
`means is less than a predetermined value.
`4. A power supply system for a hybrid vehicle ac-
`cording to any one of claims 1 to 3, wherein
`at least one of said first and second power supply
`means comprises a battery.
`5. A power supply system for use in a hybrid vehicle
`including an engine for power generation as well as a
`drive motor for vehicle propulsion, comprising:
`a drive power supply for driving said drive motor;
`a starting motor for the actuation of said engine;
`a first power supply means which receives electric
`power from said drive power supply and provides
`electric power to said starting motor;
`a control section which receives electric power from
`said first power supply means and controls the
`drive of said starting motor;
`a second power supply means which is connected
`between said firSt power supply means and said
`control section in parallel with said first power
`supply means and maintains supply voltage at said
`control section; and
`an isolation means for separating said control section
`and said second power supply means from said first
`power supply means at the time of operation of said
`starting motor.
`6. A power supply system for a hybrid vehicle ac-
`cording to claim 5, further comprising a voltage detec-
`tion means for detecting supply voltage at said control
`section, wherein
`said control section prohibits the drive of said starting
`‘ motor in the case where said supply voltage at said
`control section detected by said voltage detection
`means is less than a predetermined value.
`7. A power supply system for a hybrid vehicle ac-
`cording to claim 5 or 6, wherein
`'
`at least one of said first and second power supply
`means comprises a battery.
`.
`t
`i
`t
`t
`
`l. A power supply system for use in a hybrid vehicle
`including an engine for power generation as well as a
`drive motor for vehicle propulsion, comprising:
`a drive power supply for driving said drive motor;
`a starting motor for the actuation of said engine;
`
`60
`
`65
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`Page 12 of 12
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`FORD 1144
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`Page 12 of 12
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`FORD 1144
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