JPH01286786A - Engine-starting charger - Google Patents

Abstract

PURPOSE:To effectively utilize the output of a battery even if the terminal voltage of a battery is reduced at the time of the start of an engine by raising the terminal voltage of the battery to supply it to a motor-driven generator. CONSTITUTION:A booster circuit 9 is connected between both terminals of a battery 1 to raise the terminal voltage VB of the battery 1 to a predetermined DC voltage Vdc. A motor-driven generator controller 10 is connected between both terminals of the booster circuit 9, and applies the output voltage Vdc of the booster circuit 9 to the winding of a motor-driven generator 8. Thus, the output of the battery can be efficiently supplied to the generator to obtain a large torque at the time of the start of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine starting/charging device that integrates a starting motor and a charging generator.

[Conventional technology]

FIG. 13 is a circuit diagram showing a partial block diagram of a conventional engine starting charging device disclosed in, for example, Japanese Patent Publication No. 61-54949. In the circuit shown in FIG. 13, the negative electrode of the battery l is grounded, and the positive electrode is connected to the key switch 6. This key switch 6 has an ignition side contact a and a start side contact S. The ignition side contact a is connected to one end of the excitation current control circuit 5 and the positive side output end of the three-phase full-wave rectifier circuit 7. Note that the other end of the excitation current control circuit 5 and the negative output end of the three-phase full-wave rectifier circuit 7 are grounded. The start side contact is connected to the input side voltage of the armature current switching circuit 4. Synchronous machine 2
has three armature windings 201 (for U phase, ■ phase, and W phase) and excitation winding 202. Armature winding 2
01 have one end connected together to form a Y connection, and the other end connected to the input end of the three-phase full-wave rectifier circuit 7 and the output side of the armature current switching circuit 4. The armature current can be switched by. Three crank angle detectors 3 are also connected to this armature current switching circuit 4. Further, the excitation current of the excitation winding 202 of the synchronous machine 2 is controlled by the optical control circuit 5, which is connected between both ends of the excitation winding 202. Furthermore, the three-phase full-wave rectifier circuit 7 converts the generator output voltage into direct current and extracts it after the engine starts.

FIG. 14 is a circuit diagram showing the configuration of the armature current switching circuit shown in FIG. 13. In FIG. 14, a Zener diode 401 and a resistor 402 are connected in series between the start side contact and ground. Transistors 403 and 404, 405, 406, 407 and 408 for current switching
have 6 pairs each, and the 6 pairs of series circuits are connected between the start side contact, the connection point of the resistor 402, and the ground, and the branch points between the 6 pairs of transistors are connected to the armature winding 201 of FIG. It is connected to the U, V, and W phase terminals of the Each pace of transistors 403 to 408 has
The output ends of comparators 409-414 are connected. The inverting input terminals ((→input terminals) of the comparators 409, 411, and 413 are U and V of the crank angle detector 3.

It is connected to the terminals of each phase of W. Similarly, the non-inverting input ends ((+) input ends) of the comparators 410, 412, and 414 are also connected to the U, V, and W phase terminals of the crank angle detector 3. Comparator 409.411.

The non-inverting input terminal of 413 is connected to the connection point of resistors 415 and 416, the connection point of resistors 419 and 420, and the connection point of resistors 423 and 4, respectively.
It is connected to 24 connection points.

Resistors 415 and 416, 419 and 420, 423 and 424
Each series circuit is connected between a Zener diode 4010 cand and ground. Also, the comparator 410°41
The inverting input terminal of 2.414 is connected to the connection point between resistors 417 and 418, the connection point between resistors 421 and 422, and the connection point between resistors 425 and 426, respectively. Resistors 417 and 418
, 421, 422, 425 and 426 are connected between the cathode of the Zener diode 4010 and ground. These resistors 415-426 are resistors that divide the constant voltage produced by the Zener diode 401 and provide set voltages to the comparators 409-414.

Next, the operation will be explained. First, the excitation current control circuit 5
detects the terminal voltage of the battery 1 and controls the excitation current so as to maintain the voltage value at a predetermined value. In the starting state, a large current flows, so the terminal voltage of the battery 1 is low, and the excitation current remains constant at maximum. Armature current switching circuit 4
, the converters 409 to 414 compare the set voltage obtained from the Zener diode 401 and the resistors 415 to 426 with the output of the crank angle detector 3 for each phase of ty, v, and w, and turn on the transistors 403 to 408. /Generates a signal for turning off. As a result, six pairs of transistors, transistors 403 and 404, transistors 405 and 406, and transistors 40 and 408, operate complementary to each other and are turned on/off according to the crank angle.

For example, in a certain period, transistors 403, 406, 408
is on, transistors 404, 405, and 407 are off, and the current supplied from the battery 1 is transferred to the armature winding 20.
The current flows from the U-phase terminal of 1 to the va terminal and the W-phase terminal, and in the next period, transistors 403, 405 and 408 are turned on.
Transistors 404, 406, and 407 are turned off, allowing current to flow from the U-phase terminal and V-phase terminal of armature winding 201 to the W-phase terminal, and in the next period, transistor 404 is turned off.
, 405, 408 are on, transistors 403, 406
. Switch the direction of the flowing WL flow, armature winding 2
The magnetic field created by 01 is made to be a rotating magnetic field that always has a constant phase difference with respect to the magnetic field generated by rotating field poles (not shown).

Now, when the engine (not shown) is stopped and the key switch 6 is set to the start side contact position, the excitation winding 202 and the armature winding 2011C!
[The current flows, which creates a torque on the rotating field poles, which causes the crankshaft (not shown) to rotate.

When the field pole (not shown) starts rotating, the crank angle detector 3 detects the field pole position, and the armature is adjusted so that the speed of the rotating magnetic field created by the armature winding 201 is the same as the rotation speed of the field pole. Since the WL flow switching circuit 4 is activated, the field pole obtains torque and further accelerates. In this way, the engine can be started in a short time.

After the engine starts, when the key switch 6 is set to the ignition side contact a position, the synchronous machine 2 operates as a synchronous generator, and the generated power is converted to DC by the three-phase full-wave rectifier circuit 7, and is transferred to the battery 1 and the vehicle. Supplied to electrical equipment.

[Problem to be solved by the invention]

In conventional engine starting charging devices, when the engine is started, the output current of the battery is large, so the terminal voltage of the battery decreases due to the influence of the internal resistance of the battery, and the voltage applied to the excitation winding and armature winding of the synchronous machine decreases. Therefore, there was a problem that sufficient starting torque could not be obtained. Further, as mentioned above, K has the problem that the synchronous machine must be large in order to obtain sufficient starting torque even when the battery terminal voltage decreases.

This invention was made to solve the above-mentioned problems, and it is possible to effectively utilize the battery output even if the terminal voltage of the battery drops when starting the engine, and to increase the size of the motor generator. In addition, after the engine starts, the motor-generator operates as a generator to charge the battery and charge the electrical components inside the vehicle.
An object of the present invention is to obtain an engine starting charging device capable of supplying M force.

[Means to solve the problem]

The engine starting charging device according to the present invention includes a booster circuit that boosts the terminal voltage of a battery to obtain a predetermined DC voltage, and a motor-generator control device that supplies DC power, which is the output of the booster circuit, to a motor-generator. It has been established.

[For production]

The booster circuit according to the present invention boosts the terminal voltage of the battery to achieve a predetermined voltage level. ! Generates pressure. This DC voltage is controlled so that it always remains at a predetermined voltage even if the battery terminal voltage fluctuates. Further, the booster circuit works to limit the output current of the battery so that the battery terminal voltage does not fall below a certain set value, and can effectively extract output from the battery.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an engine starting charging device according to the invention.

A booster circuit 9 is connected between both ends of the battery 1, and this booster circuit 9 boosts the terminal voltage VB of the battery 1 to a predetermined DC voltage Vdc. A motor-generator control device 10 is connected between both ends of the boost circuit 90, and this motor-generator control device 1
0 is the DC voltage VdCfit I which is the output of the booster circuit 9
t Apply K to the motor generator winding (not shown).

FIG. 2 is a circuit diagram showing a specific example of the booster circuit in the embodiment of FIG. 1. The booster circuit 9 is a booster control circuit 90,
It has transistors Trl and Trz, diodes Dl and D2, a reactor, and a capacitor C. A boost control circuit 90 that controls on/off of the transistors Tr and Trz has one end grounded via the battery 1 and the other end grounded via the capacitor C. Further, the control terminals 1)t and bz of the boost control circuit 900 are transistors Tr1. It is connected to each base of Tr2. Each transistor Tr1. Tr
A diode D1.z is connected in parallel with the collector-emitter circuit of z.
D2 is connected in the direction shown. One end of the reactor L is connected to the batch I71, and the other end is connected to the connection point between the emitter of the transistor Tri and the collector of the transistor Tr2, and therefore to the connection point between the anode of the diode DI and the cathode of the diode D2. .

The booster circuit 90 is configured as described above, and first,
The operation when the battery 1 is discharged will be explained. When the boost control circuit 90 turns off the transistor Tr1 and turns on the transistor Tr2, the voltage from the battery 1 to the reactor L and the transistor ! 'Current flows through Tr2 and energy is stored in reactor I. Next, when the transistor Trz is turned off, this current flows into the capacitor CK through the diode Ds due to the energy stored in the reactor L, and charges the capacitor C. By repeating this operation, battery 1
The DC power of is converted to DC power of DC voltage Vdc.

This is the operation of a so-called boost chopper.

Next, the operation when charging the battery 1 will be explained. When the transistor Trl is turned on, the battery 1 flows from the capacitor C through the transistor Tri and the reactor L.
When current flows into , and transistor Tri is turned off, this ! ! The current flows back through diode D2. By repeating this operation, the battery l is charged. This is the operation of a so-called step-down chopper.

The discharging and charging operations of the battery 1 are controlled by the on/off periods of the two transistors Trl and Tf2. FIG. 3 is a circuit diagram showing a specific example of the boost control circuit 90 shown in FIG. 2.

The boost control circuit 90 includes an error amplifier 901, a triangular wave generation circuit 902, a comparator 903, and a NOT circuit 904. The error between the crushing voltage Vdc and the boost voltage command Vdc'' is amplified by an error amplifier 901, and its output Ve is compared with the triangular wave v'r!I, which is the output of the triangular wave generating circuit 902, and the comparator 90.
3 will be compared. The output of the comparator 903 is the transistor T
The signal becomes the ri pace signal and is input to the NOT circuit 904. The output of the NOT circuit 904 is the transistor Tf
It becomes the base signal of 2.

FIG. 4 shows a waveform diagram for explaining the operation of the boost control circuit of FIG. 3. Boosted voltage Vdc is boosted voltage command Vdc"
If the error amplifier 901 is smaller, the output of the error amplifier 901 is as shown in FIG.
Like e, it becomes K. As a result, the on period of the transistor is T
rt becomes short and Tr2 becomes long, and a current t flows out from the battery 1 and acts to charge the capacitor C. On the contrary, V
dc"< Vdc, the on period of Trl becomes longer, and a current of 1! flows from the capacitor C to the battery 1, and the battery 1 is charged.

Furthermore, by adding an integral element to the error intensifier 901, the on/off period of the transistor Tri + Tr2 is controlled so that Vdc = Vdc'' at all times.

Since the booster circuit 9 operates in this manner, the boosted voltage Vdc is set to the boosted voltage command Vd regardless of whether the battery 1 is charged or discharged.
c”.

Here, we will briefly discuss the characteristics of battery 1. Second
As shown in a specific example in the figure, the equivalent circuit of battery 1 is MW
It can be expressed by a power supply E and an internal resistance RB. If the output current of battery 1 is in, then the terminal voltage of battery 1 is V
B and output power PB are respectively given by the following equations.

VB = E -RB iB (1)P
B = ViiB = (E-RBin) iB (2
) From formula (2), the output power PB of battery 1 is iB=E
/ 2RB (3) VB = E
/ 2 It is maximum when (4). In this way, the output power PB of battery 1 is
Therefore, if the output current in of the battery 1 is made larger than the value shown by equation (3), the loss due to the internal resistance RBK increases and the output power PB decreases. Therefore, in order to effectively utilize the output of battery 1, K
is always smaller than the value shown in equation (3), or the battery terminal voltage VB is (4
) should always be larger than the value shown in the formula. A specific example of a boost control circuit that limits the battery output current iB or the battery terminal voltage VB in this way will be described below.

FIG. 5 is a circuit diagram showing another example of the convex body of the boost control circuit. In FIG. 5, the same reference numerals as in FIG. 3 indicate the same or corresponding parts. The only difference between the boost control circuit 90A in FIG. 5 and the boost control circuit 9o in FIG.
5 was inserted. The error amplifier 901 amplifies the error between the boosted voltage Vdc and the boosted voltage command Vdc" and outputs the battery YIl flow command iB*. Vdc < Vd
When there are c numbers, iB*>O, and the command is such that the battery output current in increases. Conversely, Vdc > Vdc”
When iB"< O, the command is to flow the battery IK charging current. Here, a limit is added to the 18 outputs of the error amplifier 901. In other words, iB* has an upper limit value (for example, given by equation (q1) Next, the error between the 18 battery current commands and the battery current iB, which is the output of the battery current detector (not shown), is determined by an error amplifier 905.
It is amplified by , and is used as one input of comparator 903 . The other operations are the same as those of the boost control circuit 90 shown in FIG. 3, and will therefore be omitted. Since this circuit has a battery current feedback loop, the battery current in follows the 13 battery current commands with good response. Therefore, the current flowing through the battery will not exceed the upper limit value of iB*, and no more current than necessary will flow from the battery 1.

FIG. 6 is a circuit diagram of a boost control circuit that has a function of preventing battery voltage VB from dropping below a certain set value. The boost control circuit 90B shown in FIG. 6 is added to the output side of the NOT circuit 904 included in the specific example shown in FIG. 3 or 5. In FIG. 6, the output side of NOT circuit 904 is connected to one input terminal of AND circuit 907, and the other input terminal is connected to the ratio I! ! device 906 is connected. The battery terminal voltage VB is compared with a certain set value Vat (for example, the value given by equation (4)) by a comparator 906 (hysteresis may be provided), and a low level output is output when VB<VBI. When the output of the comparator 906 is at a low level, the output b2 of the AND circuit 907 is always at a low level, and the transistor Tra is turned off. In this way, when the battery terminal voltage VB falls below a certain set value VB1, the transistor Tri is forcibly turned off, the battery output current decreases, and the battery terminal voltage VB does not decrease. Therefore, the battery output current The flow will no longer exceed the maximum output condition.

Next <, Excite 1 [Consider the case of a synchronous machine where #8 has an excitation winding. Since this type of synchronous machine is the same as the conventional example, the explanation will be omitted. A specific example of the motor generator control device 1o in this case is shown in a circuit diagram in FIG. The motor-generator control device 1o in FIG.
A transistor Tr3 connected to and included in
~Inverter control circuit 1 that outputs the base signal of Tr8
00, and an excitation IT current control circuit 300 that is connected to the inverter control circuit 100 and controls the current flowing to the excitation winding of the synchronous machine.

First, the operation of the excitation current control circuit 300 will be explained. Comparator 3001 works to turn on Tr9 when battery terminal voltage VB is lower than battery voltage command VB, and works to turn off Tr9 when VB)VBI. When the transistor Tr9 is turned on, the boosted voltage Vdc is applied to the excitation winding, and an excitation current flows. Then T
When r9 is turned off, the excitation current flows back through diode D9. In this way, T so that K and Va match VBI
r9 repeats on/off operation, and the excitation current is controlled. Special K: When the engine starts, the battery terminal voltage VB
Tr9 is always turned on and the maximum excitation current flows.

FIG. 8 is a circuit diagram showing a specific example of the inverter control circuit 100 included in the motor generator control device 10 shown in FIG. The inverter control circuit 100 in FIG. 8 includes a phase generator 1001 that generates the phase of an AC voltage applied to a three-phase armature winding of a synchronous machine, an error amplifier 1o02, a triangular wave generation circuit 1003, and these error amplifiers 1002. and a comparator 10 that compares the outputs of the triangular wave generation circuit 1003 with each other.
04 and NO connected to the output side of this comparator 1004.
T circuit 1005, phase generator 1001, comparator 1004
and the output side of the NOT circuit 1005, and when the input a from the phase generator 1001 is at a high level, the comparator 10
The input from 04 becomes the output e, and the input C from the NOT circuit 1005 becomes the output e when the input a is at a low level. NOT circuits 1006-1008 and ANDM circuits 1012-10
17. A specific example of the phase generator 1001 is the crank angle detector shown in the conventional example, and its output has a waveform as shown in FIG. 9(a). The error amplifier 1002 functions to set the output al to the amplitude Vaz of the output of the triangular wave generation circuit 1003 when the boosted voltage Vdc matches a certain set value vdcl, and to decrease al when vdc<VdCl. This output a1 and the triangular wave generation circuit 10
A comparator 1004 compares the signal a2 with the output a2 of the output signal A3, and outputs a signal a3 as shown in FIG. 9(b). This output a3
becomes an input to the NOT circuit 1005 and also becomes an input to the data selection circuits 1009 to 10110. NOT circuit 1
The output of 005 becomes input C of data selection circuits 1009 to 10110. The two inputs of each of the data selection circuits 1009 to 1011, i and c, are the output bt of the phase generator 1001.
It is selected by r, by, and bw, and becomes the output e. This output e
are the inputs of the NOT circuits 1006 to 1008, respectively, and one input of the AND circuits 1012, 1014, and 1016.

The outputs of NOT circuits 1006 to 1008 are each ANDed.
It becomes one input of circuits 1013, 1015, and 1017.

The other inputs of the AND circuits 1012 to 1017 are the start signals ST (signals that go high at the start), and the outputs b3 to b8 become base signals of the corresponding transistors Tr3 to Tr@ in FIG. 7, respectively. (However, the base amplifier is not shown.) Now, assume that Vdc > Vdcl, that is, the output a3 of the comparator 1004 is always at a high level, and assume that the engine is started. At this time, if the start signal ST is at a low level, the transistors Tr3 to
The pace signals b3 to b8 of Trl are all at low level,
The transistors Tr3 to Tra are all turned off, and no current tR flows through the armature winding of the synchronous machine. Start signal ST
When becomes a high level, the base signal bM, b51
bV7. by.

bw signal appears, base signal 1)4 s 1)'
A signal obtained by inverting ba, bv, and bw appears at +ba. As a result, the corresponding transistor of the inverter 200 is turned on, and the armature winding Kl current of the synchronous machine flows.

Furthermore, since the maximum excitation IE current flows through the excitation winding as described above, a large starting torque is generated in the synchronous machine and accelerates the engine. When the start signal ST becomes low level after the engine starts, the transistor Tr of the inverter 200
3 to Tr8 are all turned off, and the inverter 200 becomes a diode rectifier circuit, converting the AC 1tlt force generated by the synchronous machine into DC power. This DC power is supplied to the battery 1 and the electrical components in the vehicle through the booster circuit 9. Next K,
In the inverter control circuit lOO, Vdc < Vdc
Let us discuss the case of s. At this time, the output a3 of the comparator 1004 has a waveform as shown in FIG.
8 repeats on/off at the frequency of the triangular wave a2 which is the output of the triangular wave generating circuit 1003. This is what is called PWM (Pulse Width Modulation) control.
The average voltage applied to the g-mode winding of a synchronous machine is kept small. By performing PWM control in this way, the torque supplied to the Isogo winding can be v4!1, so the synchronous machine does not require more power than the output obtained from battery 1 when starting the engine, so the boost voltage The power obtained from the battery 1 can be effectively utilized while Vdc is maintained at a predetermined value.

Although the phase generator 1001 included in the inverter control circuit 100 shown in FIG. 8 uses the output of the flank angle detector, FIG. 10 shows a block diagram of another specific example that does not use the signal from the crank angle detector. show.

Oscillator 1018 generates a constant or variable frequency square wave signal. The divider 1019 divides the square wave signal generated by the oscillator 1018 to produce three outputs bU having a phase relationship as shown in FIG. 9(a).

by, l) Output w. For example, when starting the engine, if the frequency of the output of the oscillator 1018 is gradually increased, b
The frequencies of U, bV, bW also increase gradually. Therefore, the frequency of the current flowing through the armature winding of the synchronous machine also increases. At this time, rotational torque that follows this frequency is generated in the synchronous machine, allowing the engine to accelerate.

The motor-generator control device 10 shown in FIG. 7 was designed for a synchronous machine with an excitation winding as a motor-generator, but the same applies when a synchronous machine with a permanent magnet as an excitation pole is used as a motor-generator. starter.

Provides alternator function. FIG. 11 shows another specific example of the motor/generator control device when the motor/generator is a permanent magnet type synchronous machine. In FIG. 11, the same reference numerals as in FIG. 7 indicate the same or corresponding parts. Since the motor-generator control device 10A shown in FIG. 11 has almost the same configuration as the motor-generator control device t10 shown in FIG. 7, only the specific parts will be described below. First, since the synchronous machine does not have an excitation winding, the excitation current control circuit 390 is not required. Next, since the excitation magnetic flux cannot be adjusted in the power generation region after the engine is started, the amount of power generation is adjusted by controlling on/off the toranogistor included in the inverter 200.

A specific example of the inverter control circuit 100A in this case is shown in a circuit diagram in FIG. In FIG. 12, the same reference numerals as in FIG. 8 indicate the same or corresponding parts.

1020 is an inverter voltage command circuit that adjusts the voltage generated by the inverter 2000, and the INV signal is the inverter 20
This is a signal that controls the operation and stop of the engine.When the engine is stopped, it becomes a signal similar to the start signal ST, and when the engine is running, it is always at a high level.

The inverter voltage command circuit 1020 adjusts the output according to the magnitude of the boosted voltage Vdc when the engine is started, as explained in FIG. Adjust the output to . In other words, as mentioned above, the voltage applied to the armature winding of the synchronous machine can be adjusted based on the magnitude K of one input of the comparator 1004, so the output WL of the synchronous machine as a generator can be adjusted.
The amount can be adjusted.

The inverter control circuit 100A shown in FIG. 12 can control the alternating current force generated by the inverter 2000 with variable voltage and variable frequency using the inverter voltage command circuit 1020 and the phase generator 1001. Needless to say, it can still function as a starter and alternator.

〔Effect of the invention〕

As detailed above, according to the present invention, a booster circuit is added that boosts the DC voltage of the battery to obtain a predetermined DC voltage, so even if the battery terminal voltage fluctuates (drops) when the engine starts, the Since the output of the battery can be supplied to the effective KW, and the battery output current is limited so that the battery terminal voltage does not fall below a certain set value, the current that exceeds the battery's maximum output condition will not flow. , it became possible to efficiently supply battery output to the motor generator. As a result, a large torque can be obtained when starting the engine, and the motor generator can be made smaller. In addition, after the engine starts, the motor generator operates as a generator, and the amount of power generated can be adjusted, so a single motor generator can provide both starter and alternator functions, which is effective in saving space in the engine room. There is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the engine starting charging device of the present invention, FIG. 2 is a circuit diagram showing a specific example of the booster circuit in the embodiment of FIG. 1, and FIG. A circuit diagram showing a specific example of a boost control circuit included in one specific example, FIG. 4 is a waveform diagram showing a part of the operation of the boost control circuit shown in FIG. 3, and FIG. 5 is a boost control circuit 6 is a circuit diagram of a boost control circuit added to the specific example shown in FIG. 3 or 5, and FIG. 7 is a circuit diagram of an electric power generator in the embodiment of FIG. 1. 8 is a circuit diagram showing a specific example of the inverter control circuit included in the motor generator control device of FIG. 7, and FIG.
FIG. 10 is a block diagram showing a specific example of the phase generator included in the inverter control circuit shown in FIG. 12 is a block diagram showing another specific example of the motor generator control device; FIG. 12 is a circuit diagram showing a specific example of the inverter control circuit included in the motor generator control device of FIG. 11; FIG.
The figure is a block diagram showing an example of a conventional engine starting charging device, and FIG. 14 is a circuit diagram showing the configuration of the armature current switching circuit in FIG. 13. In the figure, 1...Battery, 8...Motor generator, 9φ
- Boost circuit, 10...t@generator control device. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Flood 1 figure v Day 10: @Kankodenkikei 葎P device 瑀2 figure 3 figure 4 figure city 5 figure flood 6 figure 7 figure! ○ Figure 9 bv Figure 1o L J 2 No≧>F

Claims (1)

[Claims] A battery, a boost circuit that boosts the DC voltage by limiting the output current of the battery so that the terminal voltage of this battery does not fall below a certain set value, and a DC voltage that is the output of this boost circuit is applied to the motor generator windings. An engine starting charging device characterized by comprising a motor generator control device for applying voltage.