Abstract:
A field winding type rotary electric machine includes: a controller; a field current integration portion provided in the controller to calculate an integral value by integrating an excessive field current exceeding a field current threshold; a field current limiting portion provided in the controller and carrying out limiting processing to limit a field current to or below a predetermined value when the integral value reaches an integral value threshold defined as a reference value at or above which the field current is limited; a controller power supply connection switch switched ON and OFF for power feeding to the controller; a controller power supply connection determination portion switching ON and OFF the controller power supply connection switch; and a power feeding ON state maintaining portion maintaining an ON state of the power feeding to the controller from start to end of the limiting processing by the field current limiting portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a field winding type rotary electric machine chiefly incorporated into a vehicle and provided with a control apparatus as well as having an armature winding and a field winding. 
     2. Background Art 
     A rotary electric machine for vehicle is generally incorporated into an engine room. An operating temperature of the rotary electric machine for vehicle is therefore extremely high. An internal temperature of the rotary electric machine for vehicle rises further due to heat generated by the rotary electric machine for vehicle in association with power generating and driving operations. Hence, when a temperature of the rotary electric machine for vehicle rises exceedingly due to a continuous operation over a long period, the rotary electric machine for vehicle may possibly break down because of damage on inner parts. 
     To overcome this inconvenience, an output control method and an output control apparatus of an AC generator for vehicle in the related art propose a technique as follows as a prevention of a breakdown of the AC generator for vehicle caused by a rise in temperature. That is, a temperature of the AC generator or ambient temperature thereof is measured and an output current of the AC generator is limited upon detection of the measured temperature exceeding a pre-set abnormal temperature value so that thermal burden on the control apparatus is lessened (see, for example, Patent Document 1). 
     The output control method and the output control apparatus described in Patent Document 1, however, protect the AC generator for vehicle against a rise in temperature by limiting a field current according to the temperature of the AC generator for vehicle detected by a temperature sensor. Accordingly, there is a need to incorporate the temperature sensor and this need poses a problem that the cost of the AC generator for vehicle increases and the structure thereof has to be changed. 
     To eliminate this problem, Patent Document 2 describes a technique to prevent an excessive rise in temperature by limiting a field current to be passed to a range within which no damage is caused by heat generation in a case where a field current flowing to a field winding remains at or above a predetermined threshold value for a predetermined time. 
     Patent Document 1: JP-A-8-9567 (FIG. 1 and a description thereof) 
     Patent Document 2: JP-A-2010-279085 (FIG. 3 and a description thereof) 
     The AC generator for vehicle described in Patent Document 2, however, is silent about a case where an initial temperature condition of the AC generator for vehicle is unknown, such as at the start-up of the power supply. For example, in a case where the internal temperature of the AC generator for vehicle is high at the start-up of the power supply, it is difficult to prevent a rise in temperature at appropriate timing with the technique in the related art in which no temperature sensor is incorporated. Hence, in such a case, an excessive rise in temperature may possibly give rise to damage on the AC generator for vehicle. 
     SUMMARY OF THE INVENTION 
     The invention was devised to solve the problems discussed above and has an object to provide a field winding type rotary electric machine requiring no temperature sensor and capable of suppressing a rise in temperature by limiting a field current flowing to a field winding and hence capable of preventing damage caused by a rise in temperature in a reliable manner even when an initial condition is unknown, such as at the start-up of the power supply. 
     A field winding type rotary electric machine according to an aspect of the invention includes: a controller; a field current integration portion that is provided in the controller and calculates an integral value by integrating an excessive field current exceeding a field current threshold; a field current limiting portion that is provided in the controller and carries out limiting processing to limit a field current to or below a predetermined value when the integral value calculated by the field current integration portion reaches an integral value threshold defined as a reference value at or above which the field current is limited; a controller power supply connection switch that is switched ON and OFF for power feeding to the controller; a controller power supply connection determination portion that switches ON and OFF the controller power supply connection switch; and a power feeding ON state maintaining portion that maintains an ON state of the power feeding to the controller from start to end of the limiting processing by the field current limiting portion. 
     According to an aspect of the invention, the field winding type rotary electric machine includes: the controller; the field current integration portion that is provided in the controller and calculates an integral value by integrating an excessive field current exceeding the field current threshold; the field current limiting portion that is provided in the controller and carries out the limiting processing to limit a field current to or below a predetermined value when the integral value calculated by the field current integration portion reaches the integral value threshold defined as the reference value at or above which the field current is limited. The field winding type rotary electric machine further includes the controller power supply connection switch that is switched ON and OFF for power feeding to the controller; the controller power supply connection determination portion that switches ON and OFF the controller power supply connection switch; and the power feeding ON state maintaining portion that maintains an ON state of the power feeding to the controller from start to end of the limiting processing by the field current limiting portion. It thus becomes possible to obtain a field finding type rotary electric machine capable of limiting the field current in a reliable manner so as to prevent a temperature of the field current type rotary electric machine from rising excessively by monitoring the field current flowing to the field current. 
     The foregoing and other object, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view schematically showing the configuration when a field winding type rotary electric machine of the invention is incorporated into a vehicle; 
         FIG. 2  is a view showing the configuration of a field winding type rotary electric machine according to a first embodiment of the invention; 
         FIG. 3  is a view showing the configuration of a field current limiting portion of  FIG. 2  according to the first embodiment of the invention; 
         FIG. 4  is a view showing time changes of a field current and a field current integral value in the field current limiting portion according to the first embodiment of the invention; 
         FIG. 5  is a view showing time changes of a field current, a field current integral value, and a field current limiting time counter value in the field current limiting portion according to the first embodiment of the invention in a case where the field current is limited; 
         FIG. 6  is a view showing time changes of a field current, a field current integral value, a field current limiting time counter value, and an IG signal in the field current limiting portion according to the first embodiment of the invention in a case where the IG signal is switched OFF while the field current is limited; 
         FIG. 7  is a view showing time changes of the IG signal and a controller power supply connection switch according to the first embodiment of the invention in a case where the field current integral value is greater than 0; and 
         FIG. 8  is a view showing time changes of the IG signal and the controller power supply connection switch according to the first embodiment of the invention in a case where the field current limiting time counter value is greater than 0. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     First Embodiment 
     Hereinafter, a field winding type rotary electric machine according to a first embodiment of the invention will be described with reference to  FIG. 1  through  FIG. 8 . Like components are labeled with like reference numerals in the respective drawings. 
       FIG. 1  is a view schematically showing the configuration when the field winding type rotary electric machine of the first embodiment is incorporated into a vehicle. As is shown in the drawing, a field winding type rotary electric machine  40  is connected to an internal combustion engine  10  via a connection portion  20 , such as a belt and pulleys. Also, a battery  30  is electrically connected to the field winding type rotary electric machine  40 . It should be noted that there is a case where the field winding type rotary electric machine  40  is directly connected to the internal combustion engine  10  without using the connection portion  20 . Further, the internal combustion engine  10  is not limited to either a gasoline engine or a diesel engine. Furthermore, the battery  30  may be dedicated to the field winding type rotary electric machine  40  or shared by a load for vehicle other than the field winding type rotary electric machine  40 . 
       FIG. 2  is a view showing the configuration of the field winding type rotary electric machine  40 .  FIG. 3  is a view showing the configuration of a field current limiting portion of the field winding type rotary electric machine  40 .  FIG. 4  is a view showing time changes of a field current and a field current integral value in the field current limiting portion. 
     As is shown in  FIG. 2 , the field winding type rotary electric machine  40  is formed of three prominent parts: a motor generator  50 , a power converter  60 , and a controller  70 . The battery  30  is connected to the power converter  60  so that the power converter  60  receives a supply of power from the outside. Also, a controller power supply  170  is connected to the controller  70  and a controller power supply connection switch  160  switches ON and OFF states of a connection to the controller power supply  170 . 
     The motor generator  50  includes a Y-connected or delta-connected three-phase armature winding  51 , a field winding  52 , and a current detector  53 . It should be noted that the motor generator  50  may use an armature winding  51  other than a three-phase armature winding. The power converter  60  includes a field winding current switching element  61  connected to the field winding  52  with a three-phase inverter, power conversion switching elements  63   a  through  63   c  and  64   a  through  64   c  connected to the respective phases of a flywheel diode  62  and the armature winding  51 . The controller  70  includes a gate driving portion  80 , a driving control portion  90 , a power generation control portion  100 , a field current control portion  110 , a field current detection portion  120 , a field current instruction portion  130 , a field current limiting portion  140 , a controller power supply connection determination portion  150 , and the controller power supply connection switch  160 . 
     The gate driving portion  80  drives the motor generator  50  or controls power generation thereof by driving the field winding current switching element  61  and the power conversion switching elements  63   a  through  63   c  and  64   a  through  64   c  according to ON and OFF instructions for the armature winding  51  and the field winding  52  sent from the driving control portion  90 , the power generation control portion  100 , and the field current control portion  110 . The driving control portion  90  controls ON and OFF timings of the power conversion switching elements  63   a  through  63   c  and  64   a  through  64   c  when the motor generator  50  is driven. Further, the power generation control portion  100  controls ON and OFF timings of the power conversion switching elements  63   a  through  63   c  and  64   a  through  64   c  for synchronous rectification while the motor generator  50  is generating power. 
     The field current detection portion  120  detects a field current I flowing to the field winding  52  by means of the current detector  53 . The field current instruction portion  130  sends to the field current control portion  110  a field current instruction value I r  for which the field current I is set as a control target. 
     The field current limiting portion  140  determines whether the field current I is to be limited according to the field current I detected by the field current detection portion  120 . In a case where a need to limit the field current I is determined as the result, the field current limiting portion  140  sends a field current limiting value I lim  to the field current control portion  110 . 
     The controller power supply connection determination portion  150  switches ON and OFF the controller power supply connection switch  160  according to an ON or OFF state of an IG signal  180  inputted from the outside and an instruction from the field current limiting portion  140 . 
     Herein, upon receipt of the field current limiting value I lim  from the field current limiting portion  140 , the field current control portion  110  sends a signal that controls the field current I to be flown to the field winding  52  to the gate driving portion  80  by setting the field current limiting value I lim  as a control target value. It should be noted, however, that in a case where the field current instruction value I r  is smaller than the field current limiting value I lim , that is, a relation, field current instruction value I r &lt;field current limiting value I lim , is established, the field current control portion  110  sends a signal that controls the field current I to take the field current instruction value I r . In a case where the field current control portion  110  does not receive the field current limiting value I lim  from the field current limiting portion  140 , the field current control portion  110  constantly sends a signal that controls the field current I to be flown to the field winding  52  according to the field current instruction value I f . 
     An operation of the field winding type rotary electric machine  40  will now be described in detail with reference to  FIG. 3  showing the configuration of the field current limiting portion  140  and  FIG. 4  showing time changes of the field current I and a field current integral value in the field current limiting portion  140 . 
     The field current limiting portion  140  includes a storage portion  141 , a field current limiting determination portion  142 , and a field current limiting instruction portion  143 . The storage portion  141  includes a field current threshold storage portion  141   a , a field current integral threshold storage portion  141   b , a field current limiting value storage portion  141   c , and a field current limiting time storage portion  141   d . The field current limiting determination portion  142  includes a field current integrator  142   a  and the field current limiting instruction portion  143  includes a field current limiting time measuring instrument  143   a.    
     The field current threshold storage portion  141   a  pre-stores a first field current threshold I th1  and a second field current threshold I th2  set to a value smaller than the first field current threshold I th1 . In short, the relation between the first and second field current thresholds I th1  and I th2  is expressed as: first field current threshold I th1 &gt;second field current threshold I th2 . 
     Also, the field current integral threshold storage portion  141   b  pre-stores a field current integral threshold S th  and the field current limiting determination portion  142  is connected thereto. 
     The field current limiting value storage portion  141   c  pre-stores the field current limiting value I lim . The field current limiting time storage portion  141   d  pre-stores a field current limiting time T lim  of the field current I. 
     An operation of the field current limiting determination portion  142  will now be described with reference to  FIG. 4 . Firstly, in a case where a relation, field current I&gt;first field current threshold I th1 , is established, the field current limiting determination portion  142  adds a difference ΔI 1  between the field current I and the first field current threshold I th1  to a field current integral value S (integration in the positive direction). On the contrary, in a case where a relation, field current I&lt;second field current threshold I th2 , is established, the field current limiting determination portion  142  subtracts a difference ΔI 2  between the second field current threshold I th2  and the field current I from the field current integral value S (integration in the negative position). Meanwhile, the field current limiting determination portion  142  maintains the current field current integral value S in a case where both the following relations are established: field current I≦first field current threshold I th1  and field current I≧second field current threshold I th2 . 
     Subsequently, in a case where a relation, field current integral value S&gt;field current integral threshold S th , is established, the field current limiting determination portion  142  determines that it is necessary to limit the field current I. The field current limiting determination portion  142  then sends a determination result to the field current limiting instruction portion  143 . 
     According to the determination result of the field current limiting determination portion  142  indicating a need to limit the field current I, the field current limiting instruction portion  143  obtains the field current limiting value I lim  from the field current limiting value storage portion  141   c  and the field current limiting time T lim  from the field current limiting time storage portion  141   d  and sets the field current limiting time T lim  to a field current limiting time counter value C lim  in accordance with Equation (1) as follows:
 
C lim =T lim   (1).
 
     The field current limiting instruction portion  143  sends the field current limiting value I lim  to the field current control portion  110  during the field current limiting time T lim . Accordingly, upon receipt of the field current limiting value I lim , the field current control portion  110  controls the field current I to take the field current limiting value I lim  (see  FIG. 5 ). It should be appreciated, however, that the field current I is controlled to take the field current instruction value I f  while the relation, field current instruction value I f &lt;field current limiting value I lim , is established. 
     It should be noted that the second field current threshold I th2  is set so that a temperature of the field winding type rotary electric machine  40  falls within a normal range while the field winding type rotary electric machine  40  is continuously operating. In this instance, the field current limiting value I lim  is set to or below the second field current threshold value I th2 . Owing to these settings, it becomes possible to lower the temperature of the field winding type rotary electric machine  40  to a normally operable temperature in a more reliable manner. 
     Herein, in a case where the field current integral value S exceeds the field current integral threshold S th , the field current limiting determination portion  142  clears the field current integral value S to 0. 
     When the field current limiting time T lim  has elapsed since the limiting of the field current I started, the field current limiting instruction portion  143  stops sending the field current limiting value I lim  to the field current control portion  110 . In other words, the limiting of the field current I is released and the field current I is controlled according to the field current instruction value I f . 
     An operation of the controller power supply connection determining portion  150  will now be described with reference to  FIG. 6  through  FIG. 8 . 
     In the related art, when the IG signal  180  is switched OFF, the controller power supply connection determination portion  150  cuts off the connection between the controller  70  and the controller power supply  170  by switching OFF the controller power supply connection switch  160 . However, for example, as is shown in  FIG. 6 , when a connection to the controller power supply  170  is cut off while the field current I is limited, measuring of the field current limiting time T lim  using the field current limiting time counter value C lim  is interrupted. Hence, even when the IG signal  180  is switched ON next time and a connection to the controller power supply  170  is switched to an ON state within a period during which the field current I is to be limited, the field current I is no longer limited. In such a case, it becomes impossible to limit the field current I at appropriate timing and elements may possibly break due to excessive heat generation. 
     To avoid such an inconvenience, the invention is configured in such a manner that the controller power supply connection determination portion  150  keeps the controller power supply connection switch  160  switched ON even when the IG signal  180  is switched OFF in a case where either one or both of the following conditions are satisfied: 
     (1) the field current integral value S is greater than 0; and 
     (2) the field current limiting time counter value C lim  is greater than 0. 
       FIG. 7  shows an operation when the IG signal  180  is switched OFF in a case where the field current integral value S is greater than 0. 
     When the IG signal  180  is switched OFF, the controller power supply connection determination portion  150  determines whether the field current integral value S of the field current limiting determination portion  142  is greater than 0. In a case where the field current integral value S is greater than 0, the controller power supply connection determination portion  150  keeps the controller power supply connection switch  160  switched ON. Because the field current control stops when the IG signal  180  is switched OFF, the field current drops to 0 A and the difference ΔI 2  between the second field current threshold I th2  and the field current I (=0) is subtracted from the field current integral value S. The controller power supply connection determination portion  150  monitors the field current integral value S and keeps the controller power supply connection switch  160  switched ON until the field current integral value S decreases to 0. When the field current integral value S decreases to 0, the controller power supply connection determination portion  150  switches OFF the controller power supply connection switch  160  to cut off the connection to the controller power supply  170 . In a case where the IG signal  180  is switched ON again while the controller power supply connection determination portion  150  keeps the controller power supply connection switch  160  switched ON, the controller power supply connection determination portion  150  continues to keep the controller power supply connection switch  160  switched ON according to the IG signal  180  independently of the field current integral value S. 
     An operation when the IG signal  180  is switched OFF when the field current limiting time counter value C lim  is greater than 0 will now be described with reference to  FIG. 8 . 
     When the IG signal  180  is switched OFF, the controller power supply connection determination portion  150  determines whether the field current limiting time counter value C lim  in the field current limiting instruction portion  143  is greater than 0. In a case where the field current limiting time counter value C lim  is greater than 0, that is, in a case where the field current limiting time T lim  has not elapsed, the controller power supply connection determination portion  150  keeps the controller power supply connection switch  160  switched ON until the field current limiting time counter value C lim  decreases to 0 and the field current limiting time has elapsed. When the field current limiting time counter value C lim  decreases to 0 and the field current limiting time T lim  has elapsed, the controller power supply connection determination portion  150  switches OFF the controller power supply connection switch  160  to cut off the connection to the controller power supply  170 . In a case where the IG signal  180  is switched ON again while the controller power supply connection determination portion  150  keeps the controller power supply connection switch  160  switched ON, the controller power supply connection determination portion  150  continues to keep the controller power supply connection switch  160  switched ON according to the IG signal  180  independently of the field current limiting time counter value C lim . 
     In a case where both the field current integral value S and the field current limiting time counter value C lim  are 0 when the IG signal  180  is switched OFF, the controller power supply connection determination portion  150  switches OFF the controller power supply connection switch  160  as soon as the IG signal  180  is switched OFF. 
     As has been described above, the second field current threshold I th2  is set so that a temperature of the winding type rotary electric machine  40  falls within a normal range in a reliable manner while the field winding type rotary electric machine  40  is operating continuously. In contrast, the first field current threshold value I th1  is set to a value with which the temperature of the field winding type rotary electric machine  40  rises beyond the normal range while the field winding type rotary electric machine  40  operates continuously. More specifically, when a difference between the field current I and the second field current threshold I th2  is used for integration, the field current I is limited too early in comparison with a case where a difference between the field current I and the first field current threshold I th1  is used for integration. 
     An addition of the field current integral value S can be performed through computation by an internal CPU (not shown) of the controller  70 . 
     The IG signal  180  is a signal sent from the vehicle to the field winding type rotary electric machine  40  (the controller  70  thereof) to play a role of an activation signal of the controller  70 . 
     The field current limiting time counter value C lim  is a time measuring count value used in the field current limiting time measuring instrument  143   a  of  FIG. 3 . 
     The field current limiting time measuring instrument  143   a  counts down the field current limiting time counter value C lim  at predetermined timing using an internally furnished subtraction counting function. The field current limiting instruction portion  143  sends the field current limiting value I lim  to the field current control portion  110  while the field current limiting time counter value C lim  is greater than 0 (that is, within the field current limiting time T lim ) and thereby limits the field current I. 
       FIG. 6  shows an operation in a case without the configuration to keep the controller power supply connection switch  160  switched ON whereas  FIGS. 7 and 8  show an operation with the configuration to keep the controller power supply connection switch  160  switched ON. When the IG signal  180  is switched ON while the control portion power supply connection switch  160  is kept switched ON in  FIGS. 7 and 8 , an operation is the same as the normal operation (an operation in a case where the IG signal  180  is switched ON continuously). As an advantage of this configuration, it becomes possible to continue the field current limiting processing because a connection to the controller power supply  170  is not cut off during the field current limiting processing. In a case where the IG signal  180  is switched ON after the controller power supply connection switch  160  is kept switched ON (when a state of being kept switched ON ends), an operation is the same as the normal power supply start-up operation and the connection to the controller power supply  170  is maintained until the field current limiting processing ends. 
     As has been described, according to the first embodiment described above, a rise in temperature of the field winding type rotary electric machine  40  is suppressed by forming the field winding type rotary electric machine  40  with: the motor generator  50  having the field winding  52 ; the field current detection portion  120  that detects a field current flowing to the field winding  52 ; the field current control portion  110  that controls the field current; the field current limiting determination portion  142  that calculates a field current integral value by integrating the field current over time and determines whether the calculated field current integral value has reached a predetermined field current integral threshold; the field current limiting instruction portion  143  that outputs an instruction to the field current control portion  110  to set the field current at or below a predetermined field current limiting value for a predetermined limiting time when it is determined that the calculated field current integral value has reached the predetermined field current integral threshold and outputs an instruction to change the predetermined limiting time in response to the field current; and the controller power supply connection switch  160  that switches ON and OFF the controller power supply  170  according to an instruction from the outside and information of the field current limiting determination portion  142  and the field current limiting instruction portion  143 . 
     As has been described, according to the field winding type rotary electric machine of the first embodiment, in a case where the field current is limited according to a detection result of the field current flowing to the field winding so that a temperature of the field winding type rotary electric machine does not rise excessively, when the field current integral value, which is the limiting determination value of the field current, is greater than 0 or the field current is being limited, a connection between the controller and the controller power supply is switched to an ON state independently of an instruction from the outside and the ON state is maintained until the field current integral value decreases 0 and the limiting of the field current ends. Owing to this configuration, there can be achieved a significant advantage that it becomes possible to obtain a field winding type rotary electric machine capable of preventing damaged caused by a rise in temperature in a reliable manner. 
     Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this is not limited to the illustrative embodiments set forth herein.