Patent Abstract:
A starter system for starting internal combustion engines including a plurality of starters connected in parallel, each having a starter motor and an engaging relay. This parallel starting system may be implemented simply and cost-effectively if at least one of the starters includes a power relay which switches the primary current path to the associated starter motor, and the engaging relay, the power relay, and the starter motor are implemented as a structural unit.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates to a parallel starting system for starting internal combustion engines. 
     BACKGROUND INFORMATION 
     Normally, electrically operated starters are used for starting internal combustion engines. In large engines having several tens or hundreds of liters of displacement such as, for example, marine engines, it is known to connect a plurality of starters in parallel to be able to provide the high starter power. 
       FIG. 1  shows a parallel starting system from the related art having two starters  1   a ,  1   b . Each of the starters includes a starter motor  2   a ,  2   b  and an engaging relay  4   a ,  4   b  which normally performs two functions. On the one hand, engaging relay  4   a ,  4   b  engages a pinion (not shown) driven by starter motor  2   a ,  2   b  with a ring gear of the internal combustion engine. On the other hand, engaging relay  4   a ,  4   b  closes a primary current path  8  via a normally open contact  5   a ,  5   b  when the pinion has engaged with the ring gear. This begins the actual starting operation. 
     To prevent one of the two starters  1   a ,  1   b  from beginning the starting operation earlier than the other, both starters  1   a ,  1   b  are interconnected in such a way that primary current path  8  to starter motors  2   a ,  2   b  is not closed until both pinions are engaged or both engaging relays  4   a ,  4   b  have completely pulled up. The two engaging relays  4   a ,  4   b  are in this case connected in parallel with respect to their control terminal and are connected to a terminal  50  which is connected to the starter switch (switch  6 ). The load terminals (terminals  30 ,  30   b ) of engaging relays  4   a ,  4   b  are, however, interconnected in series. Terminal  30  of first starter  1   a  is connected to a battery which supplies it a voltage U+. 
     In a starting operation, i.e., after ignition  6  is activated, windings HW (holding winding) and EW (pull-in winding) of engaging relays  4   a ,  4   b  are supplied with current. As a result, both engaging relays  4   a ,  4   b  pull in, switches  5   a ,  5   b  being closed. When both switches  5   a ,  5   b  are closed, both starter motors  2   a ,  2   b  are supplied with current simultaneously and start the internal combustion engine. It is a disadvantage in this case that both engaging relays  4   a ,  4   b  must switch and conduct the same current for both starter motors  2   a ,  2   b . Noise-contaminated actuating signals (signal bounce) can therefore result in high contact erosion and a high risk of contact welding exists. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is therefore to improve the switching reliability. A further object of the present invention is to develop a parallel starting system that can be wired using minimum complexity. This object is achieved according to the present invention. 
     An important idea of the present invention is to separate the customary concatenation of the functions “engage” and “switch primary current” of conventional engaging relays and instead provide two relays, one of which (engaging relay) performs the function “engage” and the other (power relay) exclusively performs the function “switch primary current.” The engaging relay and the power relay are preferably designed as a structural unit together with the associated starter motor. This makes it possible to devise a parallel starting system that may be wired in a simple and low-cost manner and in which the power relay need not be designed for excessively high loads. 
     The starters are preferably interconnected in such a way that the power relays do not switch the primary current to the starter motors until all engaging relays have pulled up (i.e., all pinions have engaged or the engaging springs are under tension). 
     According to a first embodiment ( FIG. 2 ) of the present invention, the engaging relays of two starters are connected with one another in series. This means the control terminal of the subsequent engaging relay is connected to the load terminal of the preceding engaging relay. The load terminals of the engaging relays are preferably connected to terminal  30 . If the engaging relays are connected in series, relatively high current flows to the second engaging relay, making a relatively thick connecting cable between the starters necessary. 
     According to a second embodiment ( FIG. 4 ) of the present invention, the engaging relays of two starters are connected in parallel with respect to their control terminals. The load terminals of the engaging relays are preferably connected in series, the first load terminal preferably being connected to terminal  30 . The load terminal of the last engaging relay is preferably interconnected with the control terminal ( 50   k ) of a power relay. The power relays are preferably connected in parallel. The advantage of the series connection of the load terminals is that the flow of current between two starters is substantially lower. 
     According to a preferred embodiment of the present invention, each of the starters has its own power relay which switches the flow of current to the starter motor. Optionally, at least one of the starters may also not have its own power relay ( FIG. 5 ). In this case, this engaging relay performs both functions, namely “engage” and “switch primary current.” 
     Preferably, a three-pole connection is provided between two starters connected in parallel. If the connecting cable of a starter has a plug connection, it is possible to connect a plurality of starters in a simple manner. When wiring the starters, it is only necessary to take note of the position of the starter in question in the chain of starters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the electrical circuit diagram of a parallel starting system known from the related art. 
         FIG. 2  shows the circuit diagram of a parallel starting system according to a first embodiment of the present invention. 
         FIG. 3  shows the structural design of a parallel starting system according to  FIG. 2 . 
         FIG. 4  shows the circuit diagram of a parallel starting system according to a second embodiment of the present invention. 
         FIG. 5  shows the circuit diagram of a parallel starting system according to a third embodiment of the present invention. 
         FIGS. 6   a  and  6   b  show the circuit diagram of a parallel starting system having three starters. 
     
    
    
     DETAILED DESCRIPTION 
     With respect to the explanation of  FIG. 1 , reference is made to the introduction of the background information. 
       FIG. 2  shows a parallel starting system having two starters  1   a ,  1   b . Each of starters  1   a ,  1   b  has a starting relay  13   a ,  13   b , an engaging relay  4   a ,  4   b , a power relay  12   a ,  12   b  and a starter motor  2   a ,  2   b . The primary current of starter motors  2   a ,  2   b  is switched by power relays  12   a ,  12   b . Engaging relays  4   a ,  4   b  are used only for engaging the pinion (not shown) with the ring gear and providing the starting current. 
     In a starting operation, starting relays  13   a ,  13   b , which are connected in parallel and connected to terminal  50 , pull in simultaneously and close associated switches  14   a ,  14   b . This closes a current path  7  between terminal  30  and terminal  50   i  and current is supplied to the control terminal of both engaging relays  4   a ,  4   b . In this case, engaging relays  4   a ,  4   b  are connected in series, i.e., the control terminal of engaging relay  4   b  is connected with the load terminal (terminal  50   n ) of engaging relay  4   a . Therefore, switch  16   a  of first engaging relay  4   a  closes first and after that, switch  16   b  of second engaging relay  4   b  closes. The load terminals (terminal  50   m ) of the two engaging relays  4   a ,  4   b  are connected to terminal  30 . 
     The load terminal (terminal  50   n ) of second engaging relay  4   b  is interconnected with the control terminals (terminal  50   k ) of power relays  12   a ,  12   b . Closing second switch  16   b  therefore causes current to be supplied to the control terminals of power relays  12   a ,  12   b . Power relays  12   a ,  12   b  are connected in parallel in this case. As a result, both associated switches  18   a ,  18   b  close approximately simultaneously and close the current path  8  between terminal  30  and terminal  45  of starter motors  2   a  and  2   b , respectively. The internal combustion engine (not shown) is thus started approximately simultaneously by both starter motors  2   a ,  2   b.    
     The two starters  1   a ,  1   b  in this case are connected with one another by a three-pole electrical line  11 . A relatively high current of, e.g., 200 A, which is necessary for actuating relay  4   b , flows between terminal  50   n  and  50   i  via control line  7 . In the parallel starting system shown in  FIG. 4 , this current is substantially reduced, making it possible to use a thinner cable. 
       FIG. 3  shows the physical configuration of the parallel starting system of  FIG. 2 . Each of starters  1   a ,  1   b  is designed as a structural unit, having a starter motor  2   a ,  2   b , a starting relay  13   a ,  13   b , an engaging relay  4 , and a power relay  12   a ,  12   b . Starters  1   a ,  1   b  in this case are connected with one another via a three-pole electrical lead  11 . 
       FIG. 4  shows a parallel starting system having two starters  1   a ,  1   b  that essentially have the same configuration as the starters of  FIG. 2 . With respect to the explanation of the individual elements and their mode of functioning, reference is therefore made to the description regarding  FIG. 2 . In contrast to the system of  FIG. 2 , the load terminals (terminals  50   m ,  50   n ) of engaging relays  4   a ,  4   b  are interconnected in series. As a result, only a substantially lower control current of approximately 20 A flows in control line  7  between terminals  50   n  and  50   m , making it possible to use a substantially thinner line. 
     Load switch  18   b  of engaging relay  4   b  is in turn connected to terminals  50   k  of power relays  12   a ,  12   b , which are connected in parallel. The control terminals (terminal  50   i ) of engaging relays  4   a ,  4   b  are connected in parallel and each of them is connected to terminal  30  via load contact  14   a ,  14   b  of the starting relays. 
       FIG. 5  shows a third embodiment of a parallel starting system having two starters  1   a ,  1   b  connected in parallel similar to  FIG. 2 . In this version, however, only first starter  1   a  has its own power relay  12   a . In contrast to  FIG. 2 , the primary current of starter motor  2   b  is switched by combined engaging relay  4   b . Engaging relay  4   b  in this case operates a switch  16   b  which is connected between terminal  30  and terminal  45  of starter motor  2   b . When contact  16   b  is closed, current is supplied to control terminal  50   k  of power relay  17   a . Contact  18   a  switches the current for motor  2   a  with a slight time delay with respect to  16   b . This version has the advantage that only one power relay  4  is needed. However, a slight time delay results when starting motors  2   a ,  2   b , since engaging relay  4   b  first switches on motor  2   b  and only after that supplies current to series-connected power relay  12   a  which then switches the primary current to motor  2   a.    
       FIGS. 6   a  and  6   b  show a parallel connection of three starters  1   a ,  1   b , and  1   c . Optionally, even more starters  1  could be connected in parallel. The internal configuration of all starters  1  is identical. Only the external wiring is configured differently depending on the position of starter  1   a ,  1   b , or  1   c  in the starter chain. In the case of a chain of n starters  1 , all of the starters located in the middle are configured identically with regard to their external wiring. Only first and last starters  1   a  and  1   n  must be wired differently in this case. This may be implemented in a manner which is simple and cost-effective in particular. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Starter 
           2  Starter motor 
           3  Series winding 
           4  Engaging relay 
           5  Load switch of engaging relay  4   
           6  Starter switch 
           7  Control lead 
           8  Primary current lead 
           9  Ground wire 
           11  Connecting leads 
           12  Power relay 
           13  Starting relay 
           14  Load switch of the starting relay 
           15  Normally closed contact of the engaging relay. 
           16  Normally open contact of the engaging relay 
           17  Winding of the power relay 
           18  Load switch of power relay  12

Technology Classification (CPC): 5