Abstract:
A power system for a vehicle having a power source for supplying an electric energy to a plurality of electric load groups with mutually different voltages, comprises a plurality of load elements forming each electric load group, and a plurality of output means for taking out the electric energy for each preset voltage as an intermediate voltage from the power source, the plurality of output means being located in the power source, wherein the plurality of load elements in either load group are divided into some blocks and connected to each output means so as to allow an electrical power simultaneously consumed by each divided block to become substantially equal. Additionally, one of some blocks divided in the load group is set to have more load than the other blocks. The power system for the vehicle improves the load balancing of the battery without using a special battery monitoring device nor a DC/DC converter while taking out the desired intermediate voltage from the high voltage battery.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a power system for vehicles.  
           [0003]    The present application claims priority from Japanese Patent Application No.2001-291304, the disclosure of which is incorporated herein by reference for all purposes.  
           [0004]    2. Description of the Related Prior Art  
           [0005]    A standard battery of a voltage 12V (14V power system) has been used for vehicles for many years. However, when new functions such as electric devices (mild hybrid) assisting a start of an engine and an acceleration thereof, an electric power steering, an electric brake, and an electric air-conditioning system, are attempted to be equipped in a vehicle, the electric capacity of the conventional 12V battery is not enough to drive these functions. Therefore, there is an attempt to realize new functions with a high voltage and a high electric power, and an efficient generation of electric power and thus an effective utilization thereof by means of, in future, shifting a power source of an electric system to be mounted on the vehicle to a 36V battery (42V power system) equal to 3 times as high as the voltage which is presently used.  
           [0006]    However, it takes so much time in a technical or economical aspect at present time to have only the 42V power system correspond to all electric devices mounted on the vehicle, such as valves for a low voltage, or controllers comprising an ECU. Also, in order to do so, a total amount of load is now too small for the 42V load group. Then, it is necessary for the time being to use dual load systems in the form of using the load systems for 14V and 42V together.  
           [0007]    [0007]FIG. 3 shows an example of a power system for the vehicles equipped with such dual load systems. For example, a vehicle power system  1  comprises a first battery  3  of voltage 12V to supply an electric energy to a 14V load group  2 , and a second battery  5  of voltage 36V to supply the electric energy to a 42V load group  4 . For example, the second battery  5  is such that 18 cells (single battery) are serially connected or the three batteries of 12V are serially connected.  
           [0008]    However, in order to supply the electric energy to the load groups  2  and  4  whose voltages are 14V and 42V, respectively, in such a vehicle power system  1 , two kinds of batteries  3  and  5 , each standardized voltage of which is difficult, are necessary. As a result, the costs for parts rise, and at the same time, a space for mounting the two kinds of the batteries  3  and  5  must be secured in the vehicle.  
           [0009]    In order to solve the above-mentioned problems, as shown in the vehicle power system  6  of FIG. 4, the battery of 12V such as the first battery  3  can be omitted by taking the 12V energy out from the second battery  5  in place of the 12V battery. However, because, in the second battery  5 , the load current of a battery part of 36V and the load current of a battery part of 12V overlap each other, the battery part of 12V not only becomes over-discharged, but any monitor and control and any analysis of their completion are needed for the overcharge and an over-discharge of the second battery  5  which may be caused by the over-discharge of the 12V battery part. Consequently, more costs are needed than reducing the specified battery of 12 V because an expensive DC/DC converter  7  must be equipped for the control as mentioned above.  
           [0010]    Thus, the present invention is intended for solving the aforementioned problems of a power system for the conventional vehicles. The purpose of the present invention is to provide the power system for the vehicles which enables an improvement of load balancing of the battery to be achieved without equipping a special battery monitoring device or a DC/DC converter in the power circuit by taking out a desired intermediate voltage from the high voltage battery.  
         SUMMARY OF THE INVENTION  
         [0011]    In order to accomplish the above-mentioned purpose, according to one aspect of the present invention, there is provided a power system for vehicles having a power source for supplying an electric energy to a plurality of electric load groups formed with mutually different voltages, the power system comprising a plurality of load elements forming each electric load group, and a plurality of output means for taking out the electric energy for each preset voltage as an intermediate voltage from the power source, the plurality of output means being located into a power source, wherein the plurality of load elements in either load group are divided into a predetermined number of blocks and respectively connected to each output means so as to allow an electrical power simultaneously consumed by each divided block to become substantially equal.  
           [0012]    In the power system for vehicles of the present invention, therefore, the power system for the vehicles which improves the load balancing of the battery can be provided without using a special battery monitoring device nor a DC/DC converter while taking out the desired intermediate voltage from the power source.  
           [0013]    According to the other aspect of the present invention, one of a predetermined number of blocks divided in the load group is set to have more load than the other blocks, thereby reducing the load applied to one of some blocks.  
           [0014]    Furthermore, the load group comprises devices mounted on the vehicles. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    These and other objects and advantages of the present invention will become clearly understood from the following description with reference to the accompanying drawings, wherein:  
         [0016]    [0016]FIG. 1 is a system configuration view for explaining an embodiment of a power system for vehicles of the present invention;  
         [0017]    [0017]FIG. 2 is the system configuration view for explaining the other embodiment of the power system for the vehicle of the present invention;  
         [0018]    [0018]FIG. 3 is the system configuration view for explaining an example of a conventional power system for the vehicle; and  
         [0019]    [0019]FIG. 4 is the system configuration view for explaining the other example of the conventional power system for the vehicle. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    The following is an explanation of an embodiment considered to be the most preferred in the present invention shown in FIG. 1. FIG. 1 shows a view of a system configuration for explaining an embodiment of a power system for vehicles in the present invention.  
         [0021]    A vehicle power system  10  of the present invention, as shown in FIG. 1, depicts the system in which dual load systems are applied, comprising a load group  11  of 14V, a load group  12  of 42V, and a high voltage battery  13  (for example, voltage 36V battery) to supply electric energy to the load group  11  of 14V and to the load group  12  of 42V.  
         [0022]    The load group  11  of 14V is the system suitable for a drive using the conventional voltage 12V. For example, the load group  11  comprises right and left head lamps  14 ,  15  with which it is difficult to increase a voltage by using a filament, width indicating lights or other lights (small lamps)  16 , and the other system  17  including controllers equipped with an ECU or the like. Additionally, the 14V load group  11  is controlled by ON/OFF switching of relay switches (or the switch to break circuits)  18 - 21  which are controlled by a control section (not illustrated).  
         [0023]    The load group  12  of 42V is the system suitable for the drive using the voltage 36V. For example, it comprises a starter  22  to start the engine which stops idling, an alternator (generator)  23  driven by a belt of the engine for driving accessories, a simplified power circuit  24  for supplying a preset voltage to a battery part when the battery part of a high voltage battery  13  is loaded, an electric power steering  25  for operating an actuator by an electric motor, a seat heater  26  and a defroster  27 , of which an electricity consumption is large, respectively, and the other load group  28  of 42V including air compressors or the like driven by the electric motor.  
         [0024]    The 42V load group  12  is controlled by ON/OFF switching by relay switches (or the switch to break the circuits)  29 - 33  controlled by the control section (not illustrated). Additionally, instead of a combined structure of the starter  22  and the alternator  23 , a motor/generator may be used which can switch the functions of motors and alternators according to running conditions.  
         [0025]    For example, the high voltage battery  13  comprises serially connected and 18 cells of each 2.1V to make the specified voltage 36V or 3 batteries of each 12V which are serially connected. A positive terminal of the high voltage battery is connected to a first power line  34 , and a negative terminal thereof is connected and grounded to a vehicle body. Between the first power line  34  and a ground line, the starter  22 , the alternator  23 , the simplified power circuit  24 , the electric power steering  25 , the seat heater  26 , the defroster  27 , and the other 42V load group  28  are connected in parallel.  
         [0026]    Furthermore, in an intermediate part of the high voltage battery  13 , a plurality of terminals  35 - 38  (in the present embodiment, there are 4) are provided as output means, and each 12V electric power energy can be taken out as an intermediate voltage from the three parts formed between the first power line  34  and the terminal  35 , between the terminals  36  and  37 , and between the terminal  38  and the ground line. In other words, the system is designed to set the high voltage load among 36V, 24V and 12V, by choosing and connecting two terminals from arbitrary terminals  35 - 38 .  
         [0027]    In an attempt to make the electric power simultaneously consumed approximately equal, between the terminal  35  and the first power line  34 , the left head lamp  14  is directly connected, while the right head lamp  15  is connected between the terminals  36  and  37 . Between the terminal  38  and the ground line, the width indicating lights and other lights  16  and the other load group  17  of 14V are connected in parallel via the second power line  39  so as to allow the 12V battery part, which is positioned between the terminal  38  and the ground line, to be a little more loaded than the other battery parts.  
         [0028]    Furthermore, the third power line  40  extending from the simplified power circuit  24  is designed to be connected to the terminal  38 , and the current ichg (for example, the maximum voltage is 14V) is supplied from the simplified power circuit  24  to the battery part of 12V between the terminal  38  and the ground line when necessary. Assuming that the current which flows through the left head lamp  14  and the right head lamp  15  are i 1  and i 2 , respectively, and that the current flowing through the width indicating light and the other lights  16  is i 3  and that the current flowing through the other electric load group  17  of 14V is i 4 , and when illuminating the right and left head lamps, in other words, the relay switches  18 - 21  are turned ON, the current flowing through the left head lamp  14  and right head lamp  15  are approximately identical, thus, the current ichg 1  determined by the simplified power circuit  24  is calculated as follows; 
           i   1 ≈ i   2 ≦ i   3 + i   4   
           ichg   1 = i   3 + i   4 − i   1   
         [0029]    On the other hand, when the small lamps are turned ON, in other words, the relay switches  18  and  19  are OFF and the relay switches  20  and  21  are ON, the current ichg 2  determined by the simplified power circuit  24  is calculated as follows; 
           i   1 = i   2 =0 
           ichg   2 = i   3 + i   4   
         [0030]    Thus, the current ichg 2  charged when only the small lamps are ON becomes maximum charged current in the load group  11  of 14V.  
         [0031]    As described above, according to the power system  10  for the vehicles of the present invention, there is presupposed the existence of the dual load systems comprising the 14V load group  11  and the 42V load group  12 . The 14V load group  11 , which is substantially equally divided into three, is connected to the intermediate voltage taken from the high voltage battery  13  which supplies the electric energy to these dual load systems, respectively, so that the current simultaneously consumed becomes substantially equal when the relay switches  18 - 21  are ON. The 14V load group  11  divided into three includes, for example, the right and left head lamps  14  and  15 , and the other lamps  16  and  17 . Particularly, the battery part of the high voltage battery  13  to which the lamps  16  and  17  are connected is set to be loaded a little more, and at the same time, the charged current occurred by the alternator  23  is designed to be supplied to the battery part by the more amount of the load than that of the other parts through the simplified power circuit  24 .  
         [0032]    Therefore, according to the present invention, dual load systematization of an existing vehicle can be promoted easily, and the load increase of the high voltage battery  13  can also easily be coped with. Besides, when the right and left head lamps  14  and  15  are connected directly to the high voltage battery  13  without a vehicle body grounding, the load group such as the starter  22 , the alternator  23 , the electric power steering  25 , the seat heater  26 , the defroster  27  of which electricity consumption is large, respectively, needs less current by the supplied higher voltage than that of the conventional system, so that fineness of wire harness, and thus light weighting of the vehicle can be planned, and the simplification of 14V load group  11  and thus cost reduction can be promoted.  
         [0033]    Additionally, the load of a battery part of the high voltage battery  13  which the other lamps  16  and  17  are connected to can be reduced, and load balancing can be achieved by distributing the load to be applied to the high voltage battery  13  so as to become 12V, 24V and 36V. Moreover, the controlling work in the management of charging state of the high voltage battery  13  can be reduced to a large extent.  
         [0034]    Furthermore, in the present invention, further simplification of the power circuits are achieved, that is, as shown in FIG. 2, the simplified power circuit  24  can be omitted from the power circuit. In addition, a tap (not illustrated) through which the current ichg is supplied via the power line  41  to the battery part of 12V between the terminal  38  and the ground line may be attached to the alternator  23  when necessary.  
         [0035]    By doing so, electricity generating efficiency near that of the single output of 42V is realized because the output of the alternator of 14V falls down to a large amount.  
         [0036]    Furthermore, because alternator  23  which takes the form of dual voltage output is designed to supply the current ichg when necessary, the problem that the voltage of the both two voltages in the dual load systems is hard to be output can approximately be solved.  
         [0037]    Additionally, the present invention may be applied not only to the dual load systems but also to a single 48V load group.  
         [0038]    In other words, in the dual load systems of the present invention, each 14V load group  11  which is in a state of being divided into three, of which electricity consumption is almost the same, is connected to an intermediated voltage (for example, the voltage 12V) taken from the high voltage battery  13 . However, instead of this structure, the defroster  27  and auxiliary machines such as an air-conditioner, of which electricity consumption can be divided into three in the 42V load group  12 , may be connected to the intermediate voltage of the high voltage battery  13  under the situation being divided into three.  
         [0039]    As a result, the intermediate voltage can be easily taken out from the high voltage battery  13 , without using a special battery monitoring device. Besides, the electric current of the 14V and 42V load groups  11  and  12  can be minimized, and thus the reduction of the costs in the power resource can be realized.  
         [0040]    As described so far, according to the power system for the vehicles of the present invention, the power system therefor which improves the load balancing of the battery can be provided without using the special battery monitoring device nor the DC/DC converter while taking out the desired intermediate voltage from the high voltage battery.  
         [0041]    While the present invention has been described in conjunction with the preferred specific embodiment thereof, it will be understood that the description is intended to illustrate and not limit the scope of the present invention, which is defined by the following claims.