Patent Publication Number: US-2003232697-A1

Title: Methods for eliminating power drainage in power sources used with starter-generators

Description:
RELATED APPLICATIONS  
     [0001] This application is a divisional of U.S. patent application Ser. No. 09/960,108, filed Sep. 21, 2001. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates to starter-generators. More specifically, the invention relates to a starter-generator circuit that eliminates inadvertent power drainage from a power source.  
       [0003] Starter-generators are used in utility vehicles and equipment having internal combustion engines. Starter-generators are electromagnetic machines that combine the functions of a starter motor and a generator in a single device. A starter-generator is responsible for starting an engine and, once the engine is running, operating as a generator of electrical power. The electrical power is often used to recharge a starting battery and to power devices within or connected to the vehicle or equipment containing the starter-generator. Starter-generators are usually controlled by starter-generator circuits. Often the starter-generator circuit includes a voltage regulator to control the voltage level of generated electrical power.  
       [0004] Starter-generator circuits may also interact with components of the vehicle or devices in which they are installed. For example, known utility vehicles are equipped with pedal-actuated-starter-generator circuits, such as the circuit  110  shown in FIG. 1. The circuit  110  includes a ground or ground node  111 , a battery  112  with a positive terminal  114 , and a two-position key switch  118 . The switch  118  includes a ground terminal  120 , a magneto terminal  124 , a battery terminal  126 , and an accessory terminal  128 . The switch can be placed in one of two positions—an off/magneto kill position and a run/accessory power position. When in the off/magneto kill position, the switch  118  couples the magneto terminal  124  to the ground terminal  120 . When in the run/accessory power position, the switch  118  couples the battery terminal  126  to the accessory terminal  128 . In this position, power from the battery may be supplied to accessories (such as lights, a radio, etc. in the vehicle or device) and to a starter-generator (discussed below).  
       [0005] A pedal activated switch  132  is connected to the accessory terminal  128 . When the pedal activated switch  132  is closed (such as when a driver steps on an accelerator pedal of a utility vehicle), a coupling is established between the battery terminal  126  and a first inductor coil terminal  140  of a solenoid  142 .  
       [0006] The solenoid  142  has a second inductor coil terminal  144  and an open-in-neutral gearshift switch  152  is coupled to the terminal  144 . When the open-in-neutral gearshift switch  152  is closed (such as when a driver places a utility vehicle in gear) a coupling is established between the second inductor coil terminal  144  and ground  111 . This energizes the solenoid  142  such that a solenoid switch  148  is closed. When closed, the solenoid switch  148  couples the positive terminal  114  of the battery  112  to a node  155 . The node  155  is coupled to an inductor  160 . The inductor  160  is coupled to a terminal  161  of a starter-generator  162 . The starter-generator  162  is coupled to an engine (not shown). When the engine is off, the starter-generator acts as a starter and uses power supplied from the battery to start the engine. Once the engine starts and the engine speed reaches a certain level, the starter-generator acts as generator and generates current that may be used to recharge the battery  112 .  
       [0007] The starter-generator  162  is coupled to a transistor terminal  170  of a voltage regulator  172 . The voltage regulator  172  is coupled to the node  155  and regulates the voltage applied to the battery  112  by selectively creating a path between the terminal  161  and the ground.  
       [0008] Another example of a starter-generator circuit is a key actuated starter-generator circuit. Like a pedal-actuated-starter-circuit, a key actuated starter-generator circuit has a multi-position switch coupled to a solenoid relay, a voltage regulator, and a starter-generator. However, a key-actuated starter generator circuit lacks a pedal activated switch and may or may not include a gearshift switch.  
       SUMMARY OF THE INVENTION  
       [0009] The inventors have discovered that a problem with the pedal-actuated-starter-generator circuit  110  and key-actuated starter generator circuits is that so long as the key switch (such as switch  118 ) remains in the run/accessory power position, accessories can continue to draw power from the battery. In addition, if the engine stalls (in which case the switches  132  and  152  may remain closed in the circuit  110 ) or operates in such a way that the voltage at the starter-generator is less than the voltage at the positive terminal of the battery, power may be drawn from the battery. In some circumstances it is possible that these demands may deplete the battery. Once depleted, starting the vehicle or device in which the starter-generator is located is impossible until the battery is replaced or recharged with an another mechanism. Accordingly, there is a need for an improved starter-generator circuit such that inadvertent power drainage can be eliminated or reduced.  
       [0010] Embodiments of the invention provide a system for preventing power drain of a battery and utilizes a key actuated starter-generator circuit. The circuit includes a key switch with a plurality of predetermined positions to provide a connection between an electrical power source and a solenoid, and a bypass rectifier to prevent inadvertent drainage of an electrical power source. The solenoid couples the electrical power source to a starter-generator. The circuit also includes a starter-generator to start an engine and to generate power to charge the electrical power source and a voltage regulator to regulate a predetermined voltage applied to the electrical power source. The system may also include a gear-controlled neutrally closed switch to provide a ground for the solenoid.  
       [0011] The inventors also devised methods of starting an engine with a key switch. One method involves turning a key switch to a starting position and energizing a solenoid by an electrical power source. The closing of the solenoid energizes a starter-generator. The method also involves turning the key switch to a running position, and charging the electrical power source by the starter-generator. The method further involves de-energizing the solenoid by moving the key switch to a second predetermined position, or by opening the switched circuit path. The method may further involve keeping a gear in a neutral position. By configuring a rectified circuit path and the solenoid in parallel, and with either the key switched to the second predetermined position or the switched circuit path opened, the electrical power source is recharged by the generator through the rectified circuit path.  
       [0012] Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013] In the drawings:  
     [0014]FIG. 1 is a schematic diagram of a prior-art pedal actuated starter-generator circuit.  
     [0015]FIG. 2 is a schematic diagram, partially in block form, of a key actuated starter-generator circuit with a bypass rectifier embodying the invention.  
     [0016]FIG. 3 is a detailed schematic diagram of the key actuated starter-generator circuit with the bypass rectifier shown in FIG. 2, along with electrical system components found in a typical utility vehicle.  
     [0017]FIG. 4 is a schematic diagram of one preferred embodiment of the bypass rectifier. FIG. 4A is a schematic diagram of another preferred embodiment of the bypass rectifier.  
     [0018]FIG. 5 is a flow chart depicting a method of preventing power drain utilizing a circuit embodying the invention. 
    
    
     DETAILED DESCRIPTION  
     [0019] Before embodiments of the invention are explained, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.  
     [0020]FIG. 2 illustrates an improved key actuated starter-generator circuit  210  with bypass rectifier (discussed below). The circuit  210  includes a ground or ground node  211  and a battery  212  having a positive terminal  214 . The circuit  210  also includes a three-position key switch  218 . The key switch  218  has a ground terminal  220 , a kill or magneto terminal  222 , a battery terminal  226 , a start terminal  227 , and an accessory terminal  228 . The key switch  218  can be placed in one of three positions—an off/magneto kill position (not shown), a start position (not shown), and a run/accessory power position (also not shown). In the off/magneto kill position, the key switch  218  couples the magneto terminal  222  to the ground terminal  220 . In the start position, the key switch  218  couples the battery terminal  226  to the start terminal  227 . In this position, power from the battery is supplied to a starter-generator (discussed below). In the run/accessory power position, the key switch  218  couples the battery terminal  226  to the accessory terminal  228 . In this position, power from the battery  212  may be supplied to accessories (such as lights, a radio, etc. in the vehicle or device). The start terminal  227  is coupled to a first solenoid inductor coil terminal  240  of a solenoid  242 . The solenoid  242  also has a second solenoid inductor terminal  244 .  
     [0021] The second solenoid inductor terminal  244  is connected to a closed-in-neutral gearshift switch  252 . When the closed-in-neutral gear shift switch  252  is closed, (such as when a transmission is in neutral) a coupling is established between the second solenoid inductor coil terminal  244  and ground  211 . This energizes the solenoid  242  such that a solenoid switch  248  is closed. This further couples the battery terminal  214  to a first inductor coil terminal  260  of an inductor  261 . The inductor  261  is coupled to a starter-generator  262  at a node  263 . The starter-generator  262  is coupled to a transistor terminal  270  of a voltage regulator  272 , which is coupled to the first inductor coil terminal  260  or the battery terminal  214  (the preferred coupling is shown with a solid line while the alternative connection is shown with a dashed line). The voltage regulator  272  regulates the voltage applied to the battery  212  by selectively creating a path from the node  263  to ground  211 .  
     [0022] A bypass rectifier  280  having a positive terminal  282  and a negative terminal  284  is coupled in parallel to the solenoid  242  to provide a circuit path  285  for recharging the battery  212 . The rectifier allows current flow in a single direction to the positive terminal of the battery and prevents or reduces current flow from the positive terminal of the battery along path  285 . When the closed-in-neutral gear shift switch  252  is open (for example, while the vehicle is in gear and moving), the solenoid  242  is de-energized. This opens the solenoid switch  248 , leaving the bypass rectifier  280  as the remaining circuit path through which the battery  212  is recharged. The positive terminal  282  is also coupled to the first inductor coil terminal  262  and the negative terminal  284  is coupled to the positive terminal  214  of the battery  212 .  
     [0023]FIG. 3 is a detailed schematic diagram of the key actuated starter-generator circuit  210  in conjunction with components commonly found in a utility vehicle (not shown). The components include a left head light  301 , a right head light  302 , a dashboard  303 , and an electrical component box  304 . The utility vehicle also includes components such as the battery  212 , the bypass rectifier  280 , and the starter-generator  262 .  
     [0024] The dashboard  303  includes a light switch  320 , an oil light  325 , a meter gauge  327 , a reverse buzzer  330 , and the three-position key switch  218 . The light switch  320  couples the left head light  301  and the right head light  302  to the positive terminal  214  of the battery  212  through a fuse block  334 . The solenoid  242 , which is embedded in the electrical component box  304 , is coupled to the fuse block  334 . The left headlight  301  and the right headlight  302  are also coupled to a second rectifier unit  335 , which is coupled to the ground  211 . The oil light  305  is coupled to an oil sensing unit  340  and the meter gauge  307 . The meter gauge  307  is further coupled to a fuel tank sensing unit  345 . The accessory terminal  228  of the three-position key switch  218  is coupled to the meter gauge  307 . The reverse buzzer  308  is coupled to a reverse limit switch  353  and the ground  211 . A forward limit switch  354  is also coupled to the positive terminal  214  of the battery  212  through the fuse block  334  and the solenoid  242 .  
     [0025] As should be apparent, since FIG. 3 simply includes more details of the circuit  210  plus additional well-known components, the operation of the circuit shown in FIG. 3 need not be addressed herein. However, FIG. 3 does illustrate that the closed-in-neutral gearshift  252  can be implemented using the limit switches  353  and  354 . In addition, FIG. 3 shows additional details regarding the construction of one preferred embodiment of the bypass rectifier  280 . For even further clarity, the preferred embodiment of the rectifier shown in FIG. 3 is reproduced in FIG. 4.  
     [0026]FIG. 4 is a schematic diagram of one preferred bypass rectifier  400 . The rectifier  400  includes a first diode  402  in a first circuit path  404  and a second diode  406  in a second circuit path  408  that is parallel to the first circuit path  410 . The rectifier  400  also includes a third diode  410  coupled in series to the first diode  402  in the first circuit path  404  and a fourth diode  408  coupled in series to the second diode  406  in the second path  408 . FIG. 4A is a schematic diagram of another preferred embodiment of the bypass rectifier  450 . The rectifier  450  includes a first diode  452  in a first circuit path  454  in parallel to a second diode  456  in a second circuit path  458 . The rectifier  450  further includes a third diode  462  in a third circuit path  466 . The third diode  462  in the third circuit path  466  is parallel to both the first circuit path  454  and the second circuit path  458 .  
     [0027] Although other rectifiers including a single diode or other diode combinations beyond what is shown could be used, the arrangement shown in FIG. 4 has several advantages. Diodes arranged in a series configuration increase the reverse voltage blocking capability of the diode combination. (While the forward current flows remain the same, the reverse breakdown voltage is the maximum of the two individual breakdown voltages.) Further, connecting diodes in parallel increases the current rating of the rectifier. Therefore, connecting diodes-in-series and then in parallel increases both the reverse blocking capability and the current rating. FIG. 4A shows yet another embodiment of three diodes in parallel. This arrangement increases the current rating of the rectifier as described earlier.  
     [0028] A method for preventing power drain of a battery utilizing a control circuit embodying the invention is illustrated in a flow chart  500  shown in FIG. 5. The method begins at a starting step  502 . Whether a transmission is in neutral is determined at a first decision  504 . If the transmission is not in neutral, no action occurs. Once in neutral, whether the key is at a start position is determined at step  508 . (However, it should be noted that the invention may be implemented in devices without gear-controlled switches and step  504  may be eliminated.) If the key is not at a start position, no further action is taken.  
     [0029] If the key is at a start position, the battery is coupled to the solenoid as shown in a coupling step  512 . Thereafter, the solenoid is energized by the battery at step  516 . The solenoid switch is then closed at step  520 . The starter generator inductor is then energized at step  524 .  
     [0030] Whether the key is at a run position is determined at step  528 . If the key is not at the run position, the circuit continues to apply a start current to the starter-generator. Once the key is in the run position, the engine status is checked at step  530 . If the engine is not running, no recharging will take place (step  548 ). Otherwise, the starter-generator begins to act as a generator at step  532 . The rectifier path is then enabled at step  536 . The battery is then recharged at step  540 . The key position is then checked at step  544 . If the key is at a stop position, the engine is shut off and recharging of the battery stops (step  548 ). Otherwise, the engine continues to run and recharge the battery so long as the battery is not fully charged.  
     [0031] As can be seen from the above, the invention provides a method and apparatus for eliminating inadvertent power drain from a power source used with a starter-generator. Various features and advantages of the invention are set forth in the following claims.