Patent Publication Number: US-9899178-B2

Title: Electronic control device including interrupt wire

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 13/362,295 filed on Jan. 31, 2012, which is based on and claims priority to Japanese Patent Application No. 2011-22931 filed on Feb. 4, 2011, the disclosures of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an electronic control device including an interrupt wire for overcurrent protection. 
     BACKGROUND 
     Conventionally, an electronic control device includes a fuse in case of a fault in the electronic control device. In an electronic control device in which small components are densely arranged, because a short-circuit current generated at a short-circuit fault in the small components does not reach a high current, it takes a long time to interrupt by the fuse. Especially when a large fuse is used for protecting a plurality of electronic control devices so as to reduce the number of fuses and a cost, it takes a longer time. Thus, temperatures of the components may be increased at an interruption and a voltage drop in a power supply wire and the like may be caused for a long time. In contrast, in a common wire, such as a power supply wire (e.g., a battery path and a ground path), that supplies electric power required for operating many circuits and many components mounted in accordance with advancement and diversification of electronic control, a relatively high current flows. Thus, an interrupting current of a large fuse disposed in a common wire path is further increased, and the electronic control device does not secure a sufficient interrupt performance at a short-circuit fault in each circuit or each component. The above-described issue becomes noticeable, for example, in an electronic control device for a vehicle used at a higher temperature and including many mounted devices. 
     JP-A-2007-311467 discloses a printed circuit board control device in which an interrupt wire is disposed in a power supply wire in each substrate. If an overcurrent flows, the interrupt wire melts and the power supply wire is interrupted in each substrate or each device. 
     In some cases, a plurality of circuit blocks is disposed on the substrate so that the circuit blocks perform different functions. When a short-circuit fault and the like occurs in one of the circuit blocks, an overcurrent may be generated in the short-circuited circuit block and a voltage drop may occur in other circuit blocks due to the overcurrent. The voltage drop may adversely affect operations of other circuit blocks, as disclosed in JP-A-2007-311467. Thus, the interrupt wire is disposed on the substrate for overcurrent protection. However, when the interrupt wire melts for any reason, entire circuit blocks coupled with the interrupt wire stop operations. 
     SUMMARY 
     In view of the foregoing problems, it is an object of the present invention to provide an electronic control device, which can protect a plurality of circuit blocks with interrupt wires. 
     An electronic control device according to an aspect of the present invention includes one or more substrates, a casing, a plurality of circuit blocks, a common wire, a plurality of branch wires and two interrupt wires. The circuit blocks are disposed on the substrates and the substrates are disposed in the casing. The common wire is shared by the circuit blocks. The branch wires are respectively coupled between the circuit blocks and the common wire. The two interrupt wires are respectively coupled with two of the common wire and the branch wires for overcurrent protection of the circuit blocks. 
     In the above electronic control device, when one of the interrupt wires is coupled with one of the branch wires and melts by heat generated by overcurrent, the corresponding circuit block is interrupted and stops operation. However, other circuit blocks except the circuit block interrupted by the one of the interrupt wires continue operation. Thus, the plurality of circuit blocks can be protected by the interrupt wires. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional objects and advantages of the present invention will be more readily apparent from the following detailed description when taken together with the accompanying drawings. In the drawings: 
         FIG. 1  is a block diagram showing a vehicle control system including an electronic control device according to a first embodiment of the present disclosure; 
         FIG. 2  is a diagram showing the electronic control device according to the first embodiment; 
         FIG. 3  is a diagram showing a part of the electronic control device shown in  FIG. 2 ; 
         FIG. 4  is a diagram showing an electronic control device according to a first modification of the first embodiment; 
         FIG. 5  is a diagram showing an electronic control device according to a second modification of the first embodiment; 
         FIG. 6  is a diagram showing an electronic control device according to a third modification of the first embodiment; 
         FIG. 7  is a diagram showing the electronic control device viewed from a direction XII in  FIG. 6 ; 
         FIG. 8  is a diagram showing a module circuit substrate of the electronic control device according to the third modification of the first embodiment; 
         FIG. 9  is a diagram showing a part of an electronic control device according to a second embodiment of the present disclosure; 
         FIG. 10  is a diagram showing a device including a test interrupt wire and a test opening portion; 
         FIG. 11  is a graph showing a relationship between an interrupting current and a melting time of the test interrupt wire in each case where the test opening portion is defined and where test opening portion is not defined; and 
         FIG. 12  is a diagram showing a part of an electronic control device according to a third embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     (First Embodiment) 
     An electronic control device  20  according to a first embodiment of the present disclosure will be described with reference to drawings. 
     As shown in  FIG. 1 , a vehicle control system  11  includes a plurality of electronic control devices  12 , such as an engine electronic control unit (ECU), a brake ECU, a steering ECU, a body ECU and a navigation device, which are mounted on a vehicle  10 . 
     The electronic control device  20  according to the present embodiment can be suitably used as an electronic control device  12  included in the vehicle control system  11 . The electronic control device  20  performs multiple functions including a less important function and a more important function. Specifically, as the less important function, the electronic control device  20  restricts an acceleration slip of a driving wheel, and as the more important function, the electronic control device  20  controls an engine as the engine ECU and controls a brake as the brake ECU. The electronic control device  20  may also control other vehicle-mounted devices. The controls of other vehicle-mounted devices include a less important control, such as a control regarding to a communication function, and a more important control. 
     The electronic control devices  12  including the electronic control device  20  according to the present embodiment are electrically coupled with a battery  13  via one of fuses  14   a ,  14   b  used for overcurrent protection. The battery  13  is a direct-current power source. Because each of the fuses  14   a ,  14   b  is disposed on a power supply path for supplying electric power to many electronic control devices, each of the fuses  14   a ,  14   b  may be a large fuse for  15  A or  20  A. When one of the electronic control devices  12  coupled with the fuse  14   a  has abnormality and an overcurrent greater than a predetermined current value is generated, the fuse  14   a  blows out by the overcurrent, and a power supply via the fuse  14   a  is interrupted. Thus, an adverse influence to the other electronic control devices  12  can be restricted. In an example shown in  FIG. 1 , each of the electronic control devices  12  is electrically coupled with the battery  13  via one of the fuses  14   a ,  14   b . However, all the electronic control devices  12  may also be electrically coupled with the battery  13  via a single fuse, or each of the electronic control devices  12  may also be electrically coupled with the battery  13  via one of more than two fuses. 
     A configuration of the electronic control device  20  according to the present embodiment will be described with reference to  FIG. 2  and  FIG. 3 . In  FIG. 2 , circuit blocks  40  and  50  are shown by two-dot chain lines for convenience of drawing. 
     The electronic control device  20  includes a casing C, a circuit substrate  21  and circuit blocks  30 ,  40 ,  50 . The circuit blocks  30 ,  40 ,  50  are disposed on the circuit substrate  21 , and the circuit substrate  21  is disposed in the casing C. The circuit block  30  restricts the acceleration slip of the driving wheel, the circuit block  40  controls the engine as the engine ECU, and the circuit block  50  controls the brake as the brake ECU. The circuit substrate  21  is electrically coupled with external devices and other electronic control devices  12  via a connector  22 . Each of the circuit blocks  30 ,  40 ,  50  performs a corresponding function according to a predetermined signal transmitted from outside. 
     As shown in  FIG. 2 , the circuit blocks  30 ,  40 ,  50  are electrically coupled with a power supply wire  23  via branch wires  31 ,  41 ,  51 , respectively. The power supply wire  23  supplies electric power of the battery  13  to the circuit blocks  30 ,  40 ,  50  via the connector  22 . Thus, the power supply wire  23  can function as a common wire shared by the circuit blocks  30 ,  40 ,  50 . 
     In the power supply wire  23 , an interrupt wire  24  that functions as overcurrent protection for the circuit substrate  21 , which includes the circuit blocks  30 ,  40 ,  50 , is disposed. The interrupt wire  24  melts by heat generated by an overcurrent and interrupts an electric connection via the interrupt wire  24 . The interrupt wire  24  has a wire width sufficiently smaller than a wire width of the power supply wire  23 . The wire width means a dimension in a direction that is perpendicular to a direction of electric current on a surface of the circuit substrate  21 . For example, the interrupt wire  24  has a wire width within a range from 0.2 mm to 0.3 mm, and the power supply wire  23  has a wire width of 2 mm. The interrupt wire  24  functions as a first interrupt wire. 
     A configuration of the circuit block  30  will be described with reference to  FIG. 3 . In the circuit block  30 , a plurality of electronic components  32  for restricting the acceleration slip is densely-mounted on the circuit substrate  21 . One of the electronic components  32  on the circuit substrate  21  is a ceramic capacitor  33 . The ceramic capacitor  33  may be formed by stacking a high-permittivity ceramic made of barium titanate and an internal electrode in layers for improving temperature characteristics and frequency characteristics, and thereby having a large capacity with a small size. 
     The circuit block  30  is coupled with the power supply wire  23  via the branch wire  31 . In the branch wire  31 , an interrupt wire  34  that functions as overcurrent protection for the circuit block  30  is disposed. The interrupt wire  34  melts by heat generated by an overcurrent and interrupts an electric connection via the interrupt wire  34 . The interrupt wire  34  has a wire width smaller than the wire width of the interrupt wire  24  so that an interrupting current of the interrupt wire  34  is smaller than an interrupting current of the interrupt wire  24 . The interrupt wire  34  functions as a second interrupt wire. 
     In the electronic control device  20  having the above-described configuration, for example, when a short-circuit fault occurs in the ceramic capacitor  33  and an overcurrent flows in the interrupt wire  34 , the interrupt wire  34  generates heat in accordance with the overcurrent. When the generated heat becomes greater than a predetermined temperature, the interrupt wire  34  melts, and the electric connection via the interrupt wire  34  is interrupted. Accordingly, the other circuit blocks  40  and  50  coupled with the power supply wire  23  can be protected from the overcurrent. The current at interruption is not high enough to blow the interrupt wire  24  and the fuse  14   a . Thus, the damage of the circuit block  30  does not influence to the other circuit blocks  40  and  50  supplied with power via the interrupt wire  24  and other electronic control devices  12  supplied with power via the fuse  14   a . A time from generation of the overcurrent to the melting of the interrupt wire  34  is a few milliseconds, and a melting time of each of the fuses  14   a ,  14   b  is generally about 0.02 seconds. Thus, the overcurrent protection can be appropriately achieved even to an electronic control device or an electronic component that is required to improve a processing speed. 
     Each of the circuit blocks  40  and  50  does not include the interrupt wire  34 . When a short-circuit fault and the like occurs in the circuit block  40  or  50 , an overcurrent generates and flows to the power supply wire  23 . Then the interrupt wire  24  melts by heat generated by the overcurrent. Thus, the circuit blocks  30 ,  40 ,  50  stop operation. In a case where the interrupt wire  24  is not disposed, the overcurrent in the power supply wire  23  causes a voltage drop in the power supply wire  23 , and the voltage drop may cause false operations of the circuit blocks coupled with the power supply wire  23 . Therefore, when the interrupt wire  24  is disposed, false operations in other circuit blocks except the circuit block in which the short-circuit fault occurs are restricted. Accordingly, a plurality of circuit blocks  30 ,  40 ,  50  disposed on the circuit substrate  21  is protected by the interrupt wires  24  and  34 . 
     Specifically, because the interrupting current of the interrupt wire  34  is smaller than the interrupting current of the interrupt wire  24 , when a short-circuit fault and the like occurs in the circuit block  30 , the interrupt wire  34  melts earlier than the interrupt wire  24  by an overcurrent generated in the circuit block  30 . By this way, adverse effects to other circuit blocks  40  and  50  are restricted with certainty. 
     An electronic control device  20  according to a first modification of the first embodiment will be described with reference to  FIG. 4 . In the electronic control device  20  according to the first modification of the first embodiment, an interrupt wire  34  may also be disposed in the circuit block  40  or  50  in addition to the interrupt wire  34  disposed in the circuit block  30 . For example, as shown in  FIG. 4 , the interrupt wire  34  may be disposed in the branch wire  51  of the circuit block  50 . In this case, an interrupting condition of the interrupt wire may be adjusted according to an importance of the function of the corresponding circuit block. 
     An electronic control  20  device according to a second modification of the first embodiment will be described with reference to  FIG. 5 . In the electronic control device  20 , at least two of the circuit blocks  30 ,  40 ,  50  may include respective interrupt wires  34 . For example, as shown in  FIG. 5 , two interrupt wires  34  are disposed in the respective circuit blocks  30  and  50  without disposing the interrupt wire  24 . 
     In a case where two interrupt wires  34  are disposed in two respective circuit blocks performing different functions including a more important function and a less important function, the interrupt wire  34  disposed in the circuit block performing a less important function may be configured to have a smaller interrupting current than the interrupt wire  34  disposed in the circuit block performing a more important function. 
     By the above-described configuration, the interrupt wire  34  disposed in the circuit block performing the less important function, such as the restriction of the acceleration slip of the driving wheel, has smaller interrupting current than the interrupting current of the interrupt wire  34  disposed in the circuit block performing the more important function, such as control of the brake. Thus, the interrupt wire  34  disposed in the circuit block performing the less important function melts earlier than the interrupt wire  34  disposed in the circuit block performing the more important function. As described above, the interrupt wires  34  is disposed according to the importance of the function of the circuit block so that the circuit block performing the more important function continues operation even when the circuit block performing the less important function stops operation. The interrupt wire  34  disposed in the circuit block performing the less important function corresponds to the second interrupt wire, and the interrupt wire  34  disposed in the circuit block performing the more important function functions as a third interrupt wire. 
     An electronic control device  20  according to a third modification of the first embodiment will be described with reference to  FIG. 6  to  FIG. 8 . In  FIG. 6 , a configuration in a casing  61  of the electronic control device  20  is shown. In  FIG. 6 , some connectors are omitted for convenience of drawing. 
     In the electronic control device  20  according to the third modification of the first embodiment, a plurality of circuit blocks may be disposed on a circuit substrate or on a plurality of circuit substrates. For example, as shown in  FIG. 6  and  FIG. 7 , the circuit blocks  30 ,  40 ,  50  are disposed on circuit substrates that are electrically coupled with each other, and the circuit substrates are disposed in the casing  61 . Specifically, a power supply circuit  62   a  including common electronic components are mounted on a mother substrate  62 . A common electronic component means an electronic component that is shared by the circuit blocks  30 ,  40 ,  50 . The mother substrate  62  is electrically coupled with module substrates  63 ,  64 ,  65  that respectively perform the functions of the circuit blocks  30 ,  40 ,  50  via connectors  66 . Each of the connectors  66  is disposed between two adjacent substrates  63 ,  64 ,  65 . 
     In this case, the power supply wire  23 , which is the common wire, may be disposed on the mother substrate  62 , and branch wires may be disposed on respective module substrates and coupled with the power supply wire  23  via the connectors  66 . Additionally, the interrupt wire  24  may be disposed in the power supply wire  23  on the mother substrate  62 , and at least one of the branch wires may include the interrupt wire  34 . For example, as shown in  FIG. 8 , interrupt wires  34  may be disposed in the branch wire  63   a  of the module substrate  63  and in the branch wire  64   a  of the module substrate  64 . By the above-described configuration, circuit blocks disposed on the module substrates  63 - 65  and the mother substrate  62  can be protected by the interrupt wires  24  and  34 . 
     Further, at least one of the module substrates may include a plurality of circuit blocks as the above-described circuit substrate  21 . On the module substrate, the interrupt wire  34  may be disposed at least in one of the branch wires of the circuit blocks. 
     (Second Embodiment) 
     An electronic control device  20   a  according to a second embodiment of the present disclosure will be described with reference to  FIG. 9 . In  FIG. 9 , a solder resist layer that defines an opening portion  28   a  is not shown for convenience. 
     In the electronic control device  20   a , the solder resist layer, which functions as a protective layer protecting a surface of the circuit substrate, defines the opening portion  28   a  so that at least a portion of the interrupt wire  34  is exposed outside. 
     As shown in  FIG. 9 , the solder resist layer defines the opening portion  28   a  in such a manner that a middle portion of an entire length of the interrupt wire  34 , which is most likely to generate heat, is exposed outside. 
     Reasons of providing the opening portion  28   a  will be described with reference to  FIG. 10  and  FIG. 11 . 
     In a device shown in  FIG. 10 , a portion of a test interrupt wire  101  is exposed outside through a test opening portion  102  defined by a solder resist layer. The test interrupt wire  101  is supplied with a predetermined current, and an interrupting current I with which the test interrupt wire  101  melts and a melting time t when the test interrupt wire  101  melts are measured. Furthermore, an interrupting current I and a melting time t of a test interrupt wire  101  in a case where a solder resist layer does not define a test opening portion  102  are also measured. The test interrupt wire  101  has an entire length L 1  of 2.85 mm and has a width W 1  of 0.25 mm. The test opening portion  102  has an opening length L 2  of 0.6 mm in a direction parallel to a length direction of the test interrupt wire  101  and has an opening width W 2  of 0.25 mm in a width direction of the test interrupt wire  101 . In  FIG. 10 , the opening width W 2  is drawn as being longer than the width W 1  for convenience of drawing. 
     In  FIG. 11 , a bold solid line S 1  shows a relationship between the interrupting current I and the melting time t of the test interrupt wire  101 , a portion of which is exposed through the test opening portion  102 , and a range between bold dashed lines centered on the bold solid line S 1  shows a variation range of the melting time t with respect to the interrupting current I. A thin solid line S 2  shows a relationship between the interrupting current I and the melting time t of the test interrupt wire  101  in a case where a test opening portion  102  is not defined, and a range between thin dashed lines centered on the thin solid line S 2  shows a variation range of the melting time t with respect to the interrupting current I. 
     As shown in  FIG. 11 , at the same interrupting current, the melting time t decreases and the variation range decreases when the test opening portion  102  is defined by the solder resist layer. In contrast, in the case where the test opening portion  102  is not defined by the solder resist layer, the melting time t of the test interrupt wire  101  increases in each overcurrent range and the variation range increases compared with the case where the test opening portion  102  is defined. This is because a melt conductor generated by melting of the test interrupt wire  101  flows from the test opening portion  102  and the melt conductor is less likely to stay at a position of the test interrupt wire  101  before melting. 
     Thus, when at least a portion of the interrupt wire  34  is exposed through the opening portion  28   a , the melting time t decreases, the overcurrent protection action can be achieved early, and a temperature rise of a protected component can be restricted. Furthermore, a time for which a voltage of the power supply wire  23  decreases due to interruption by the interrupt wire  34  can be reduced. In addition, because the variation of the melting time t decreases, a capacity of a stabilizing capacitor that is designed in view of the melting time of the interrupt wire  34  in each device or each circuit can be reduced, and a cost and a size can be reduced. Furthermore, because the melting time t decreases also in a rated region of current, a circuit can be designed more freely. 
     As described above, when the interrupt wire  34  melts in accordance with heat generated by the overcurrent, a melt conductor generated by melting of the interrupt wire  34  flows from the opening portion  28   a . Accordingly, the melt conductor is less likely to stay at a position of the interrupt wire  34  before melting, variations in the melt position and the melting time due to stay of the melt conductor can be restricted, and adverse effects to other electronic components  32  due to the heat generated by the interrupt wire  34  are restricted. Further, a decrease in an interrupt performance by the interrupt wire  34  can be restricted. 
     In the electronic control device  20   a  according to the present embodiment, the opening portion  28   a  is disposed so that the middle portion of the interrupt wire  34  which is most likely to melt is exposed outside. Alternatively, the opening portion  28   a  may be disposed so that another portion of the interrupt wire  34  is exposed outside or the whole interrupt wire  34  is exposed outside. The above-described configuration of the opening portion  28   a , through which at least a portion of the interrupt wire  34  or  24  is exposed, may be applied to other embodiments and modifications. 
     (Third Embodiment) 
     An electronic control device  20   b  according to a third embodiment of the present disclosure will be described with reference to  FIG. 12 . 
     In the electronic control device  20   b , the interrupt wire  34  is coupled with the power supply wire  23  via a connection wire  70 . 
     As shown in  FIG. 12 , an end of the interrupt wire  34  is electrically coupled with the power supply wire  23  via the connection wire  70 . A wire width of the connection wire gradually increases toward the power supply wire  23  in an arc manner (R-shape) so that a cross-sectional area at an end of the connection wire  70  adjacent to the interrupt wire  34  is smaller than a cross-sectional area at the other end of the connection wire  70  adjacent to the power supply wire  23 . Thus, side ends of the connection wire  70  smoothly connect with respective side ends of the interrupt wire  34  and gradually extend toward the power supply wire  23 . 
     Thus, when heat generated at the interrupt wire  34  by an overcurrent is transmitted to the power supply wire  23  via the connection wire  70 , heat required for melting the interrupt wire  34  is not absorbed excessively to the power supply wire  23  compared with a case where heat is transmitted directly to the power supply wire  23 . Accordingly, a variation in temperature rise in the interrupt wire  34  can be restricted, and the decrease in interrupt performance of the interrupt wire  34  can be restricted. In particular, the heat generated at the interrupt wire  34  by the overcurrent is gradually diffused in the connection wire  70  and is widely transmitted to the power supply wire  23 . Thus, a local temperature rise in the power supply wire  23  can be restricted. During a steady state of the electronic control device  20   b , the interrupt wire generates heat due to the current flowing through the interrupt wire. In the steady state, overcurrent is not generated. Because the heat generated at the interrupt wire may be gradually diffused via the power supply wire  23  in the steady state, a temperature rise of the interrupt wire can be restricted and a long-term reliability of the electronic control device can be increased. 
     Because the side ends of the interrupt wire  34  and the respective side ends of the connection wire  70  are smoothly connected with each other, when the interrupt wire  34  and the connection wire  70  are formed using etching liquid, the etching liquid can uniformly flow at connecting portions of the side ends of the interrupt wire  34  and the respective side ends of the connection wire  70 . Accordingly, the etching liquid is less likely to stay at the connecting portions and a variation in the wire width of the interrupt wire  34  can be restricted. Thus, the decrease in interrupt performance by the interrupt wire  34  can be restricted. 
     The connection wire  70  may be disposed between the interrupt wire  34  and the branch wire  31 , or may also be disposed between the interrupt wire  24  and the power supply wire  23 . The above-described configuration of the connection wire  70  may be applied to other embodiments and modifications. 
     While the present disclosure has been described with reference to preferred embodiments thereof, it is to be understood that the present disclosure is not limited to the above-described embodiments and constructions. The invention is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure.