Title of Invention

CONTROLLER FOR VEHICLE ALTERNATOR

Abstract

The present invention relates to a controller for a vehicle alternator. In a control device of an a.c. generator for a vehicle which is designed in such a way that for a first time right after an engine having been started, an output of the a.c. generator is suppressed to a minimum value, and for a second time following the first time, the output of the a.c. generator is gradually increased from the minimum value up to a maximum value to stabilize the revolution of the engine, the invention is intended to shorten a period of time required to suppress the output of the generator at high temperatures to thereby prevent a reduction in the charging performance of a battery .At high temperatures, a time interval of a timer 402, to which the first period of time is set, and a discharging time constant of a capacitor 407, which defines the second period of time, are both shortened on the basis of an output a of a temperature sensor 410.At high temperatures, a detection threshold for a revolution detector 40 I, on the basis of which the start of the engine is detected, is set to a low level to shorten an initial excitation period of the generator. FIG 1

Full Text

SPECIFICATION CONTROLLER FOR VEHICLE ALTERNATOR Field of the Invention The present invention relates to control of a vehicle alternator for supplying electric power to electric load of a vehicle immediately after startup of an engine. Description of Related Art A vehicle alternator is generally driven by an engine through a V-belt or the like, converts and outputs rotational energy into electric energy, and is demanded for higher and higher output as the electric load on the vehicle is recently more and more increased. However, when the alternator has a higher output, the engine suffers from higher load torque due to driving of the engine. This causes the engine to tend to unstably rotate during unstable state of explosion/combustion of the engine particularly immediately after startup of the engine. In addition, since the alternator outputs the highest output at the startup of the engine to charge a battery which is over discharged by a starter motor for startup, load on the engine becomes larger and larger, so that the engine tends to become more and more unstable in rotation. Such phenomenon is particularly significant in cold climate. Conventionally, to overcome such inconvenience, Japanese Patent Application Laid-Open No. 3-173324 has proposed a controller which attains stabilization of engine rotation by setting at the minimum the continuity rate of a switching element inserted in a field coil in series for a predetermined period of time after power generation by an alternator, thereby completely eliminating a load torque due to driving of the alternator immediately after startup of the engine, while incrementally controlling the setting of said continuity rate from the minimum value to the maximum value after the predetermine period of time expires, thereby preventing sudden increase of load on the engine, preventing generation of belt slip noise in a cold climate, and preventing generation of belt slip noise or reduction of engine rotation when the engine output recovers to the normal state. FIG. 6 shows a circuit diagram of such controller for a vehicle alternator, while FIG. 7 shows a control characteristic diagram of it. Operation of the controller is explained. Reference numeral 1 denotes an alternator, 2 a rectifier, 3 a voltage regulator, 4 a field current controller, 5 a battery, 6 a key switch, 7 electric load of vehicle, 8 a switch, 10 an initial exciting resistor. Since the alternator 1 does not yet generate power when the key switch 6 is turned on, a comparator 307 of the voltage regulator 3 is "low," and a timer 402 of the field current controller 4 is "low." Therefore, at the moment, a comparator 4 09 of the field current controller 4 is "high," and a power transistor 310 is turned "on," so that an initial exciting current flows into a field coil 102 through the initial exciting resistor 10. Then, when the alternator 1 is driven by the engine to start power generation, the timer 402 becomes "high" to start clocking. During a predetermined period of time Tl when the timer 402 operates, the voltage at point C is at a level set by divider resistors 403 and 404. The set level has a relationship with a chopping wave signal at point B as shown in FIG. 7a. They are compared by the comparator 409 of the field current controller 4, and its comparison output provides a continuity waveform of the power transistor 310, as shown in FIG. 7b. At the moment, the continuity rate of the power transistor 310 is at the minimum set value, the generated voltage by it is arranged to be less than the voltage of battery, so that output of the alternator 1 is 0 during the predetermined period of time Tl, as shown in FIG. 7c. Then, when the predetermined period of time ,T1- expires, and the timer 402 becomes "low," the voltage at point C decreased to a predetermined level over a predetermined period of time T2 set by a time constant circuit of a capacitor 407 and a resistor 406, as shown in FIG. 7a. During such duration, the power transistor 310 has a continuity waveform by the comparison output of the comparator 409 as shown in FIG. 7b, in which the continuity rate of the power transistor 310 gradually increases and reaches the maximum value (100%) after the predetermined period of time T2 expires. Then, during the predetermi ned period of time T2, the output of alternator gradually increases from 0% to 100% as indicated by a solid line in FIG. 7c, and thereafter the control transfers to its original control by a comparison output from the comparator 307 of the voltage regulator 3. This conventional approach employs fixed values for the duration Tl for stabilizing the engine rotation by eliminating load torque due to driving of the alternator immediately after the engine is started up, and the duration T2 for gradually increasing the output of alternator to 100%. However, such control of the alternator is only necessary in a low temperature state, and not necessary in a high temperature state. It is because the engine has a good startup capability in a high temperature state. Tf the alternator is controlled in the high temperature state, it is not desirable because the output of alternator is svippressed immediately after startup of the engine, thereby the battery 5 discharging and being deteriorated for i.ts charging performance. Therefore, in the high temperature state, it is preferable to shorten the duration Tl for suppressing the output of alternator and the duration T2 for gradually increasing the alternator output to 100%, so that the alternator output reaches 100% in a short period of time. In addition, although it is arranged to suppress the output of alternator to a low level as an initial exciting duration until startup of the engine is detected (during the rotation is less than a threshold) to decrease load on the battery, it is preferable that the initial exciting duration is shortened in the high temperature state since the engine has a good startup capability in such state. BRIEF SUMMARY OF THE INVENTION An object of the present invention is a controller for vehicle alternator suppressing output of the alternator at the minimum value for a predetermined period of time immediately after the engine is started up, and then gradually increasing the output of alternator to the maximum value, wherein at least one of the duration for lowering the output of alternator to the minimum value and the duration for gradually increasing the output of alternator is shortened in a high temperature state, thereby preventing charging performance of a battery from being deteriorated. In addition, another object of the present invention is to stabilize rotation of an engine by setting to a longer period of time in a cold state the duration for suppressing the output of alternator to the minimum value immediately after startup of the engine and the duration for gradually increasing the output of alternator to the maximum value to eliminate load torque due to driving of the alternator. A still another object of the present invention is to provide a controller for vehicle alternator for preventing discharge of a battery by suppressing a field current to an initial exciting current until the number of rotation of an engine reaches a threshold, suppressing output of the alternator by setting the field current to the minimum value during a first duration after the number of rotation of the engine reaches the threshold, and gradually increasing the output of the alternator to the maximum value during a subsequent second duration, wherein the threshold for detecting the number of rotation of the engine is set to a lower value at a high temperature state to shorten an initial exciting duration. The controller for vehicle alternator according to the present invention relates to a one comprising an alternator having a field coil, a rectifier for rectifying alternate current output of the (said) alternator, a battery connected to an output terminal of said rectifier, a voltage regulator having a switching element for controlling a current through said field coil, detecting a terminal voltage of the (said) rectifier, and intermittently controlling the field current with the (said) switching element to regulate an. output voltage of the (said) alternator to a predetermined value, and a field current controller for setting a continuity rate of said switching element to the minimum set value during a first period of time after the (said) alternator starts power generation, gradually increasing the setting the continuity rate from the (said) minimum set value to the maximum value during a second period of time, and shortening at least one of the (said) first and second periods of time when temperature is equal to or higher than a predetermined value. Since at least one of the first period of time for suppressing the output of the alternator to the minimum value and the second period of time for gradually increasing the output of the alternator to the maximum value is shortened at the high temperature state, it is possible to prevent the charging performance of the battery from being deteriorated in a high temperature state. In the controller for vehicle alternator according to the present invention, it is preferable to shorten in a high temperature state both the first period of time for suppressing the output of the alternator to the minimum value and the second period of time for gradually increasing the output of the alternator to the maximum value. Since both the first and second period of time are shortened, it is to further enhance the advantages that the duration for suppressing the output of the alternator is shortened, and that the charging performance of the battery is prevented from being deteriorated. In addition, the controller for vehicle alternator according to the present invention relates to a one comprising an alternator having a field coil, a rectifier for rectifying alternate current output of the (said) alternator, a battery connected to an output terminal of said rectifier, a voltage regulator having a switching element for controlling a current through said field coil, detecting a terminal voltage of the (said) rectifier, and intermittently controlling the field current with the (said) switching element to regulate an output voltage of the (said) alternator to a predetermined value, and a field current controller for controlling a continuity rate of the (said) switching element so that the (said) field current is an initial exciting current until startup of the engine is detected, setting the continuity rate of the (said) switching element to the minimum set value during a first period of time after the startup of the engine is detected, gradually increasing the setting of the (said) continuity rate from the (said) minimum set value to the maximum value during a second period of time, and setting a threshold for the number of rotation for detecting the startup of the engine to a lower value when the temperature is equal to or higher than a predetermined value. Since a threshold for the number of rotation for detecting the startup of the engine is set to a lower value in a high temperature state, it is possible to shorten the initial exciting duration and to suppress discharge from the battery. Furthermore, the controller for vehicle alternator according to the present invention relates to a gne comprising an alternator having a field coil, a rectifier for rectifying alternate current output of the (said) alternator, a battery connected to an output terminal of said rectifier, a voltage regulator having a switching element for controlling a current through said field coil, detecting a terminal voltage of the (said) rectifier, and intermittently controlling the field current with the (said) switching element to regulate an output voltage of the (said) alternator to a predetermined value, and a field current controller for controlling a continuity rate of the (said) switching element so that the (said) field current is an initial exciting current until startup of the engine is detected, setting the continuity rate of the (said) switching element to the minimum set value during a first period of time after the startup of the engine is detected, gradually-increasing the setting of the continuity rate from the minimum set value to the maximum value during a second period of time, and setting a threshold for the number of rotation for detecting the startup of the engine to a lower value and shortening the (said) first and second period of time when the temperature is equal to or higher than a predetermined value. Since a threshold for the number of rotation for detecting the startup of the engine to a lower value is set to a lower value in a high temperature state, it is possible to shorten the initial exciting duration and to suppress discharge from the battery. Furthermore, since the first and second period of time are shortened in a high temperature state, it is possible to shorten the duration for suppressing the output of alternator and to prevent the charging performance of the battery from being deteriorated. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of a controller for vehicle alternator according to the present invention; FIG. 2 is timing charts for describing the operation of the controller of FIG. 1 in a low temperature state; FIG. 3 is timing charts for describing the operation of the controller of FIG. 1 in a high temperature state; FIG. 4 is a circuit diagram showing another embodiment of a controller for vehicle alternator according to the present invention; FIG. 5 Is a circuit diagram showing still another embodiment of a controller for vehicle alternator according to the present invention; FIG. 6 is a circuit diagram showing an example of a conventional controller for vehicle alternator; and FIG. 7 is timing charts for describing the operation of the controller of FIG. 6. BEST MODE FOR CARRYING OUT THE INVENTION Now, a controller for vehicle alternator according to the present invention is described with reference to the drawings. Embodiment 1: FIG. 1 is a circuit diagram showing an embodiment of a controller for vehicle alternator according to the present invention, and FIG. 2 is timing charts showing operation in a low temperature state at a - i in the circuit of FIG. 1. FIG. 3 is timing charts showing operation in a high temperature state at a - i in the circuit of FIG. 1. In FIG. 1, an alternator 1 has an armature coil 101 and a field coil 102, and is connected to a rectifier 2. The rectifier 2 has an output terminal 201 and a grounding terminal 202. Reference numeral 3 denotes a voltage regulator section of the controller accordi ng to the present invention, while reference numeral 4 denotes a power generation controller section. A constant voltage source A consists of a resistor 301 and a Zener diode 302, and is supplied as a power supply for the controller. A comparator 307 is for detecting an output voltage of the alternator, compares a potential which is the output voltage divided by resistors 305 and 306 with reference to a divided voltage of resistors 303 and 304, and output H level if the divided voltage of the alternator is at or higher than the reference voltage, and I. level if it is lower than that. Voltage of the battery 5 may be detected, instead of detecting the output voltage of the alternator. An initial exciting oscillator 308 of the alternator outputs a rectangular wave with a fixed frequency and fixed duty. Reference numeral 310 denotes a power transistor for intermittently controlling the field coil, and Reference numeral 309 denotes a NOR gate of a driver for the power transistor, which outputs H level if all inputs are at "L" level to turn on the power transistor, and L level if either one input is H level to turn off the power transistor. A diode 311 is connected to the field coil in parallel to absorb surge when the field coil is shut off. Reference numerals 403 and 404 denote dividing resistors for determining charge potential for a capacitor 407, reference numeral 405 denotes a diode for preventing a counter flow through the capacitor 40 7, reference numeral 406 is a discharge resistor for the capacitor 407, reference numeral 408 denotes a chopping wave generator for PWM and connected to a comparator 409 for PWM together with the capacitor 407. Reference numeral 401 denotes a rotation detector of the alternator 1 receiving a single-phase half-waveform as input, which detects the rotation of the alternator 1, and indirectly determines the rotation of the engine, a drive source. Output of the rotation detector 4 01 is turned on at a predetermined number of rotations or higher, and connected to an initial exciter 308 and a timer 402. In addition, the rotation for determination is changed over with an input signal of a temperature sensor. The timer 402 is turned on with a trigger by an output of the rotation detector 401, and turned off in a predetermined period of time. Output of this timer is connected to a dividing point of the resistors 403 and 404. In addition, the predetermined period of time is changed over with an input signal of a temperature sensor. The temperature sensor 410 is mounted in the controller, and its output is turned on at a predetermined temperature or less, and off at a higher temperature than it, and connected to the rotation detector 401 and the timer 402. Reference numeral 5 denotes a battery of the vehicle, 6 a key switch, 7 an electrical load of the vehicle, 8 a switch for the electrical load, 10 an initial exciting resistor. Now, operation of the circuit of FIG. 1 is described at a-i in the low and high temperature states with reference to the timing charts of FIGS. 2 and 3. FIGS. 2 a-i are waveforms at a-i of FIG. 1 in the low temperature state. FIGS. 3 a-i are waveforms at a-i of FIG. 1 in the high temperature state. ! In FIG. 2, since the temperature is at the predetermined value or less, the temperature sensor 410 outputs an ON signal a to set the rotation detector 401 and the timer 402 to the low temperature state. That is, the rotation detector 401 is set for a higher threshold for the number of rotation to detect startup of the engine (higher than the number of rotation for comp.l ete explosion at startup of the engine, for example, 1,500 rpm in term of the alternator), and the time constant Tl of the timer 402 is set at a higher value. Since output of the timer 402 is turned off until the rotation detector 401 detects startup of the engine (FIG. 2c), the dividing point of the resistors 403 and 404 is grounded to reduce the potential of the capacitor 407, and the positive input of the comparator 4 09 is grounded through the resistor 406 (FIG. 2e), so that output of the comparator 409 becomes L level (FIG. 2f). During output of the rotation detector 401 is in Off state (FIG. 2b), the timer 402 is in a reset off state, and the initial exciter 308 is in an operating state (FIG. 2d). In a state before the engine is started up, and when its number of rotation is lower than the threshold detected by the rotation detector 401, the operation of the transistor 310 depends on the operation of the initial exciter 308, and in the initial excited state (FIG. 2g). Since the output of the alternator 1 is lower than the reference voltage at the moment, the output of the comparator 307 is at L level. In addition, the output f of the comparator 409 is also at L level. Accordingly, in an interval in which the output d of the initial exciter 308 is at L level, output of the NOR gate 309 becomes H level to turn on the transistor 310 (FIG. 2g). If the key switch 6 is left in the On state, the battery 5 may be exhausted. To prevent such situation, in a state where the key switch 6 is turned on, and the engine is not yet started up, the field current of the alternator 1 which is a 1oad of the battery 5 is chopped by the transistor 310 to suppress the alternator output to about 1/5. This is the initial exciting state, and corresponding to interval A of FIG. 2h. Then, when the engine is started up, and its. number of rotation exceeds the threshold, the output of the rotation detector 4 01 is turned on (FIG. 2b) to stop the operation of the initial exciter 308 (FIG. 2d), and to cause the timer 402 to start time count. Once the output of the timer 402 is turned on (FIG. 2c), it releases the dividing point of the resistors 403 and 404, so that the capacitor 407 is charged to a divided potential divided by the resistors 403 and 404. The potential is set to a value slightly lower than the peak value of chopping wave at the negative input of the comparator 409, in which the possibility at which the output of the comparator 409 becomes L is 10-15% (FIG. 2f). The operation of the transistor 310 is changed over from the On duty determined by the initial exciter 308 to the On duty determined by the comparator 409. The On duty changes from about 20% determined by the initial exciter 308 to the above-mentioned 10-15% (FIG. 2g). The value of 10-15% duty is set to a value at which the output voltage of the alternator 1 does not exceed the voltage of the battery 5, or the mini mum value at which the alternator 1 does not perform output. Then, when the time constant Tl of the timer 402 expires, and times tip, the output of the timer 402 is turned off (FIG. 2c) , the dividing point of the. resistors 403 and 4 04 is grounded, and the capacitor 407 starts discharge through the resistor 406, so that the positive input potential of the comparator 409 decreases (FIG. 2e). As the positive input potential decreases, the possibility at which the output of the comparator 409 (FIG. 2f) becomes L, or the continuity (On) rate of the transistor 310 gradually increases (FIG. 2g). The operation described above is described with the continuity rate of field coil of FIG. 2h or the continuity rate of the transistor 310 and the alternator output of FIG. 21. The field current of the alternator 1 operates at the continuity rate A of the initial excitation when the engine is started up but at the number of rotation lower than the predetermined value, and at the continuity rate B slightly lower than the initial excitation when the number of rotation is higher than the predetermined value. Since the generation voltage of the alternator is set to be lower than the voltage of the battery 5 in the regions A and B, there is no possibility that the alternator provides output. Then, when a first period of time for the generation cut region B (Lime constant Tl of the timer 402) expires, the continuity rate of the field coil gradually increases from the minimum value, and enters the increment region C where the alternator starts output. Its value gradually increases during a second period of time (time constant T2 determined by the capacity of the capacitor 4 07 and the value of the resistor 406), thereby suppressing sudden increase of load on the engine due to output of the alternator. Thereafter, the controller performs normal voltage control. As described above, when the engine is started up in a low temperature state, the startup performance can be ^improved by setting the first period of time in which the output voltage of the alternator is at the minimum and the second period of time in which the output of the alternator is then gradually increased to the maximum to a relatively long, thereby stabilizi ng the rotation of the engine. FIG. 3 shows operation when the temperature is higher than the predetermined value. The output of the temperature sensor 410 is turned off (FIG. 3a), and the detection threshold of the rotation detector 401 for detecting startup of the engine is set to a value lower than that in the low temperature state (in this example, 800 rpm in term of the alternator). In addition. the time constant Tl of the timer 402 is also set to a shorter period of time (in this example, about 1/10). Since the detection threshold of the rotation detector 401 is set at a lower value, the timing is advanced to turn off the output d of the initial exciter 308 with the output b of the rotation detector 401. This shorten the interval in which the initial exciting current is supplied as the field current of the alternator 1 (region A of FIG. 3h). Operation of each component .in the initial exciting state is same as that in FIG. 2 except that their interval is shortened. When the engine is started up, and its number of rotation exceeds the detection threshold of the rotation detector 401, the output b of the rotation detector 401 is turned on (FIG. 3b) to cause the output of the initial exciter 308 to be L level, thereby completing the initial excitation interval (FIG. 3d). In addition, the output of the timer 402 becomes H level to start counting (FIG. 3c). This causes the voltage of the capacitor 407 to be high, to be applied to the positive input terminal of the comparator 409 (FIG. 3e), and the conductive interval g of the transistor 310 becomes controlled by the output f of the comparator 409 (FIG. 3f, g). Since the time constant Tl of the timer 4 02 is set in the high temperature state to about 1/10 of that in the low temperature state, the timer 402 completes in a shorter period of time, and its output becomes L level to complete the generation cut region B. Therefore, the voltage of the capacitor 4 07 attenuates in a time constant T2 determined by the capacity of the capacitor 407 and the resistor 406, and the positive input of the comparator 409 also attenuates accordingly (FIG. 3e). Thus, the interval in which the output f of the comparator 409 becomes L level gradually increases (FIG. 3f), and, accordingly, the interval in which the transistor 310 is in the on state gradually increases from the minimum to the maximum (FIG. 3g). This also causes the continuity rate of the field current of the alternator 1 to gradually increase from the minimum to the maximum (FIG. 3h), and the output of the alternator to accordingly increase from the minimum to the maximum (FIG. 3i) . In describing the above operation with the continuity rate of the field coil (FIG. 3h) and the output of the alternator (FIG. 31), when the predetermined rotation of the alternator is detected, the operation immediately proceeds from the initial exci t.ation region A to the increment region C through a very short generation cut region B. Embodiment 2: FIG. 4 is a circuit diagram showing another embodiment of the controller for vehicle alternator according to the present invention. In FIG. 4, there is shown a temperature sensor 9 mounted outside of the alternator, for example, on a part of the engine, and performs a similar operation to that of the temperature sensor 410 in FIG. 1. The operation timing of the circuit in FIG. 4 is the same as that of FIGS. 2 and 3. Embodiment 3: FIG. 5 is a circuit diagram showing still another embodiment of the controller for vehicle alternator according to the present invention. This embodiment makes shorter in the high temperature state both the period of time (first period of time) in which the output of the alternator is suppressed to the minimum, and the period of time (second period of time) in which the output of the alternator is gradually increased from the minimum to the maximum. Since the period of time in which the output of the alternator is suppressed can be further shortened than in Embodiment 1, it is possible for the charging of the battery to be prevented from deterioration when the engine is started up in the high temperature state. In FIG. 5, reference numeral 411 denotes a resistor for discharging the capacitor 407 which is connected to the capacitor 407 and the resistor 406 in parallel, and reference numeral 412 denotes a transistor for controlling the resistor 411 and is controlled by the output of the temperature sensor 410. In the low temperature state, since the output of the temperature sensor is turned on, the transistor 412 is shut off, and the resistor 411 does not act, the second period of time determined by the discharge time constant of the capacitor 407 becomes longer. In the high temperature state, since the output of the temperature sensor i s turned off, the transistor 412 is conductive, and the resistor 43 1 forms a discharge circuit for the capacitor 407 together with the resistor 406, the time constant becomes shorter for discharge, and the second period of time becomes shorter. That is, the increment time T2 becomes shorter during the interval i n which the transistor 412 is conductive, so that both the startup characteristics of the engine in the low temperature state and the charging performance of the battery can be effectively attained by changing the increment interval in the low and high temperature states. In addition, in the high temperature state, the first period of time Tl for suppressing the output of the alternator to the minimum is shortened by shortening the time limit of the timer 402 with the output of the temperature sensor 410. Its operation waveforms are same as those of Embodiment 1. In addition, in the high temperature state, the threshold of the rotation detector 401 for detecting the startup of the engine is set to a lower value by the output of the temperature sensor 410, thereby shortening the initial excitation interval for the alternator. Its operation is same as those of Embodiment 1. As described above, the present invention is a controller for vehicle alternator suppressing output of the alternator at the minimum value in a first period of time when the alternator starts rotation, and then gradually increasing the output of alternator from the minimum to the maximum in a subsequent second period of time, wherein at least one of the first and second period of time is shortened in a high temperature state to suppress the output of the alternator immediately after the startup of the engine, whereby charging performance of a battery can prevented from being deteriorated. In addition, since, immediately after the startup of the engine in the low temperature state, it is arranged to suppress the output of the alternator to the minimum during the first period of time, and to increase it from the minimum to the maximum during in the subsequent second period of time, it is possible to eliminate load torque due to driving of the alternator in starting up the engine in the low temperature state, thereby stabilizing the rotation of the engine and preventing sudden increase of the engine load, so that generation of belt slip noise and dropping of rotation of the engine can be prevented, and the startup performance of the engine can be improved. In addition, since the present invention sets the threshold of number of rotation for detecting the startup of the engine to a lower value in the high temperature state, it is possible to shorten the initial excitation interval for the alternator and to shorten the interval in which the output of the alternator can be suppressed. WE CLAIMS: 1. A controller for vehicle alternator comprising an alternator having a field coil, a rectifier for rectifying alternate current output of said alternator, a battery connected to an output terminal of said rectifier, a voltage regulator having a switching element for controlling a current through said field coil, detecting a terminal voltage of said rectifier, and intermittently controlling the field current with said switching element to regulate an output voltage of said alternator to a predetermined value, and a field current controller for setting a continuity rate of said switching element to the minimum set value during a first period of time after the alternator starts power generation, incrementally control ling the setting of said continuity rate from the (said) minimum set value to the maximum value during a second period of time, and shortening at least one of said first and second periods of time when temperature is equal to or higher than a predetermined value. 2. The controller for vehicle alternator according to Claim 1, wherein the field current controller shortens both the first and second period of time. 3. A controller for vehicle alternator comprising an alternator having a field coil, a rectifier for rectifying alternate current output of said alternator, a battery connected to an output terminal of said rectifier, a voltage regulator having a switching element for controlling a current through said field coil, detecting a terminal voltage of said rectifier, and intermittently controlling the field current with said switching element to regulate an output voltage of said alternator to a predetermined value, and a field current controller for controlling a continuity rate of said switching element so that said field current is an initial exciting current until the number of rotation of the engine reaches the threshold, setting the continuity rate of said switching element to the minimum set value during a first period of time after the number of rotation of engine reaches the threshold, incrementally controlling the setting of said continuity rate from said minimum set value to the maximum value during a second period of time, and setting said threshold to a lower value when the temperature is equal to or higher than a predetermined value. 4. A controller for vehicle alternator comprising an alternator having a field coil, a rectifier for rectifying alternate current output of said alternator, a battery connected to an output terminal of said rectifier, a voltage regulator having a switching element, for controlling a current through said field coil, detecting a terminal voltage of said rectifier or said battery, and intermittently controlling the field current with said switching element to regulate an output voltage of said alternator to a predetermined value, and a field current controller for controlling a continuity rate of said switching element so that said field current is an initial exciting current when the number of rotation of the engine is less than the threshold, setting the continuity rate of said switching element to the minimum set value during a first period of time after the number of rotation of the engine reaches the threshold, incrementally controlling the setting of said continuity rate from said minimum set value to the maximum value during a second period of time, and setting said threshold to a lower value and shortening said first and second period of time when the temperature is equal to or higher than a predetermined value. 5. A controller for vehicle alternator substantially as herein described with reference to the accompanying drawings.

Documents:

1725-mas-1998-abstract.pdf

1725-mas-1998-claims duplicate.pdf

1725-mas-1998-claims original.pdf

1725-mas-1998-correspondance others.pdf

1725-mas-1998-correspondance po.pdf

1725-mas-1998-description complete duplicate.pdf

1725-mas-1998-description complete original.pdf

1725-mas-1998-drawings.pdf

1725-mas-1998-form 1.pdf

1725-mas-1998-form 26.pdf

1725-mas-1998-form 3.pdf

1725-mas-1998-other documents.pdf

abs-1725-mas-1998.jpg