Abstract:
The power circuit device for vehicles is provided with a grounding portion for grounding portions closer to a power consumption device side than a relay of main conductive routes when the relays used for the main conductive routes extending from an accumulator of a vehicle to a fuel heating device, a catalyst heating device, an electric pump, or the like is turned OFF, so that a false power application is not executed even a short-circuit occurs in a part of a power circuit. Also, when two relays are arranged in series, the grounding portion is provided for the relay closer to the power consumption device in order to monitor a voltage level of the main conductive route and make it easy to detect a short-circuit or a disconnection occurrence.

Description:
INCORPORATION BY REFERENCE  
         [0001]    The disclosure of Japanese Patent Application No. 2001-347178 filed on Nov. 13, 2001 including the specification, drawings and abstract are incorporated herein by reference in their entirety.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to a power circuit device for vehicles for controlling a selective power supply to power consumption devices, such as a fuel heating device, a catalyst heating device, and an electric pump from an accumulator such as a battery, in a vehicle, and to a control method thereof.  
           [0004]    2. Description of the Related Art  
           [0005]    In vehicles such as an automobile, various power consumption devices are selectively activated by power supplied from an accumulator such as a battery. Examples of the power consumption devices are a fuel injector heater which heats a fuel, which is to be injected, at the time of a cold start of an internal combustion engine, a catalyst heater which heats a catalyst until an exhaust purifying catalyst warms up, an electric pump such as an oil pump or an air pump, or the like. In present vehicles, a power supply to the power consumption device from the accumulators is commonly executed by a power circuit device with a relay switched between ON (conductive state) and OFF (shut-off state) by a command signal from an electric vehicle operation control device with a computer.  
           [0006]    Basically an operation of the power consumption device mounted in this type of vehicle can be controlled based on a control judgment of the electric vehicle operation control device. However, an operating environment of the power consumption device may vary beyond the judgement of the vehicle operation control device. Also, a malfunction may occur in each power consumption device, particularly in a heating device and its peripheral devices, due to heating. Due to a disturbance, a malfunction also may occur in an operation of the electric vehicle operation control device. In consideration of such a disturbance, Japanese Patent Laid-Open Publication No. 8-326527 discloses an insertion of another relay in series with the relay, which is ON-OFF controlled by the operation control device, into a power circuit of an electric heater, in a control of current application to the electric heater by an electric heating catalyst which is disposed in an exhaust passage of the internal combustion engine. It has been proposed that the other relay is separately ON-OFF controlled by detecting a current application condition of the electric heater.  
           [0007]    When two relays are inserted in series in the middle of a main conductive route which passes a current to the power consumption device such as the electric heater of a catalyst from the accumulator, aside from ON-OFF conditions of each relay, a power supply of the power consumption device can be shut off also by turning OFF either of the relays when the power consumption device should not be activated, which ensures higher reliability in terms of security of the power consumption device.  
           [0008]    However, even a short-circuit failure occurs in the power circuit including these relays due to a malfunction or welding, and either or both of the two relays are switched OFF, a possibility that the power consumption device is damaged due to being supplied with uncontrollable power by a power supply device cannot be entirely eliminated.  
         SUMMARY OF THE INVENTION  
         [0009]    With respect to turning ON-OFF the power supply of the power consumption device in a vehicle, when the relay is turned OFF, a current may be falsely applied to the power consumption device due to a short-circuit failure occurrence, which is caused by welding, or the like in a part of the power circuit.  
           [0010]    It is a primary object of the invention to prevent a false power application with higher reliability not only by shutting off a current supply to the power consumption device by turning OFF the relay but also by effectively using a switchover of the relay to OFF separately.  
           [0011]    In addition, it is another object of the invention to achieve the following additional items by utilizing characteristics obtained from a relay double installation structure, when the power circuit device for vehicles includes the double installation structure of the relay. More specifically, the object is to make it possible not only to detect the above-mentioned occurrence of a short-circuit failure but also to detect other short-circuit failures or disconnection failures which may occur in such a power circuit for vehicles, when a failure occurs in a part of the power circuit or the power consumption device.  
           [0012]    In order to solve the above-mentioned primary problem, a power circuit device for vehicles according to one aspect of the invention is a power circuit device for vehicles for controlling a selective power supply to the power consumption device from the accumulator. It is also provided with a main conductive route that includes relays switched between ON and OFF and passes a current to the power consumption device from the power supply device, and a grounding portion for grounding a portion in the main conductive route closer to the power consumption device than the relay when the relay is turned OFF. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic view showing an embodiment of a power circuit device for vehicles according to the invention.  
         [0014]    [0014]FIG. 2 is a schematic view showing a modification example with respect to a part of the power circuit device for vehicles shown in FIG. 1.  
         [0015]    [0015]FIG. 3 is a diagram showing an example of failure detection procedures in an operation of the power circuit device for vehicles shown in FIG. 1 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Hereinafter, embodiments of the invention will be explained in detail, referring to the attached figures.  
         [0017]    [0017]FIG. 1 is a schematic view showing a power circuit device for vehicles according to the invention, for selectively supplying a current from an accumulator  10  to a power consumption device  20  in a vehicle, as an embodiment. The power consumption device  20  is provided with a fuel injector heater, an exhaust catalyst heater, and an oil pump or an air pump. According to the embodiment shown in the figure, a first armature  32 , which moves up and down pivoting on a first relay output terminal  31 , is drawn to a first coil  33  and brought to an open position abutting against an first relay input terminal  34 , when a current is applied to the first coil  33 . In a similar manner, a second armature  42 , which moves up and down pivoting on a second relay output terminal  41  of the second relay  40 , is drawn to a second coil  43  and brought to an open position abutting against a second relay input terminal  44 , when a current is applied to the second coil  43 .  
         [0018]    This brings about an “ON” state where the first relay output terminal  31  and the first relay input terminal  34 , and the second relay output terminal  41  and the second relay input terminal  44  are electrically connected respectively.  
         [0019]    Meanwhile, as shown in the figure, when a current is not applied to the first coil  33  and the second coil  43 , the first armature  32  and the second armature  42  are urged to the open positions which are away from the first relay input terminal  34  and the second relay input terminal  44  by a spring which is not shown in the figure. Then, an “OFF” state, where the first relay output terminal  31  and the first relay input terminal  34 , and the second relay output terminal  41  and the second relay input terminal  44  are electrically insulated, is brought about.  
         [0020]    Also, in the second relay  40 , when the second armature  42  is brought to the open position, the second armature  42  abuts against a ground-side terminal  45 .  
         [0021]    A positive terminal  52  for the accumulator of the accumulator  10 , which is grounded by a negative terminal  50  for the accumulator, is connected to the first relay input terminal  34  through a front half portion  56  of the main conductive route including an accumulator fuse  54 . The first relay output terminal  31  is connected to the second relay input terminal  44  through a middle portion  58  of the main conductive route. The second relay output terminal  41  is connected to a positive terminal  62  for the power consumption device through an end half portion  60  of the main conductive route. A negative terminal  64  for the power consumption device is grounded.  
         [0022]    The first coil  33  is excited with an exciting current, which is supplied from a first relay drive circuit embedded in an electric vehicle operation control device  66  with a built-in computer, through a first relay driving output terminal  68  and a first relay conductive route  70 . In a similar manner, the second coil  43  is excited with an exciting current, which is supplied from a second relay drive circuit embedded in an electric vehicle operation control device  66 , through a second relay driving output terminal  72  and a second relay conductive route  74 . The other ends of the first coil  33  and the second coil  43  are grounded along with the ground-side terminal  45 .  
         [0023]    A voltage monitoring circuit is also embedded in the electric vehicle operation control device  66 . An output terminal  76  for the voltage monitoring circuit, an output terminal of the electric vehicle operation control device, is connected to the end half portion  60  of the main conductive route, through a voltage monitoring conductive route  80  including a voltage monitoring circuit fuse  78 .  
         [0024]    The voltage monitoring circuit is means of applying a constant voltage of approximately 5 volts to the terminal  76  through a resistance element with an appropriate resistance as well as measuring a voltage level at the output terminal  76  for the voltage monitoring circuit.  
         [0025]    The voltage monitoring circuit checks a grounding state of the end half portion  60  of the main conductive route, when a voltage from the accumulator  10  is not applied to the end half portion  60  of the main conductive route. Also, the voltage monitoring circuit detects an insulation or a ground short-circuit if it occurs in the end half portion  60  of the main conductive route or the power consumption device  20 .  
         [0026]    The voltage monitoring circuit also checks whether a voltage level at the end half portion  60  of the main conductive route is normal, when a voltage from the accumulator  10  is applied to the end half portion  60  f the main conductive route. Details of the operation will be explained later referring to FIG. 3.  
         [0027]    Also, when the power consumption device  20  is a fuel heater for heating an injected fuel, it is usually provided for each cylinder of an internal combustion engine. Therefore, with respect to a multi-cylinder internal combustion engine, the circuit shown in FIG. 1 is provided to each cylinder except for the accumulator  10  and a main portion of the vehicle operation control device  66 . In such a case, it is also acceptable to provide the relay  30  as a common relay to all the cylinders, and to provide each portion downstream of the relay  40  to each cylinder.  
         [0028]    In an embodiment shown in FIG. 1, the second armature  42  moves up and down pivoting on the second relay output terminal  41 . However, when the second relay  40  is turned OFF, it is acceptable that the second armature  42   a  is detached from both the second relay input terminal  44  and the second relay output terminal  41 , which are on an ON side, and is abutted against the ground-side terminals  45  and  46  on OFF side, which is the opposite side of the terminals on the ON side. In this case, if the ground-side terminal  45  is grounded in a similar manner to FIG. 1, it is acceptable to connect the ground-side terminal  46  to the end half portion  60  of the main conductive route.  
         [0029]    In either of the above-mentioned structures, when the second relay  40  is turned OFF, not only the end half portion  60  of the main conductive route, which is closer to the power consumption device  20  than the second relay  40 , is insulated from the accumulator  10 , but also the end half portion  60  of the main conductive route is grounded by the relay  40  which has been turned OFF. Therefore, even a short-circuit failure occurs in an indifferent route from the accumulator  10  to the end half portion  60  of the main conductive route, the power consumption device  20  can avoid being damaged by such a short-circuit current.  
         [0030]    [0030]FIG. 3 is a diagram showing an embodiment of procedures to control the power circuit for vehicle, shown in FIG. 1, by the vehicle operation control device  66 , selectively supply a current from the accumulator  10  to the power consumption device  20 , and then detect whether the power circuit is properly operating using the voltage monitoring circuit.  
         [0031]    First, when the power consumption device is not operating, that is, both the first relay  30  and the second relay  40  are in OFF state (shut-off state), the end half portion  60  of the main conductive route is grounded through the ground-side terminal  45  of the second relay  40 . Therefore, a voltage level detected by the voltage monitoring circuit is supposed to be zero.  
         [0032]    A threshold value for a voltage level, which is detected by the voltage monitoring circuit in a state where both the first relay  30  and the second relay  40  are in OFF state (or, at least when the second relay  40  is turned OFF), is set at an appropriate small positive value, such as zero.  
         [0033]    Then, when the second relay is in OFF state and a disconnection or a current application failure (e.g. a contact failure between the second armature  42  and the ground-side terminal  45 ) occurs in the grounding circuit for grounding the power consumption device  20 , the disconnection or the current application failure) can be detected based on the fact that the voltage level detected by the voltage monitoring circuit exceeds the threshold value V 0 .  
         [0034]    Secondly, when the vehicle operation control device  66  determines that the power consumption device  20  should be newly activated, the second coil  43  is initially energized by the second relay drive circuit at the time of t 1 . When the second coil  43  is energized, the second armature  43  is drawn by the second coil  43  to be detached from the ground-side terminal  45  and be abutted against the second relay input terminal  44 .  
         [0035]    When the second armature is detached from the ground-side terminal  45 , the grounding of the end half portion  60  of the main conductive route is reset, and a voltage applied from the voltage monitoring circuit to the end half portion  60  of the main conductive route is applied to the power consumption device  20 . Also, when the circuit device and the power consumption device  20  are in normal state, a monitor voltage is a predetermined voltage level Vm in accordance with an amount of monitor current passing through the power consumption device  20 . Therefore, if a voltage level detected by the voltage monitoring circuit is zero during time period when the first relay  30  is still in OFF state and only the second relay  40  is in ON state, it can be ascertained that a ground short-circuit (e.g. a welding of the second armature  42  to the ground-side terminal  45 ) has occurred in the end half portion  60  of the main conductive route.  
         [0036]    Also, when the end half portion  60  of the main conductive route and the power consumption device  20  are in normal state, a current is passed through the power consumption device from the voltage monitoring circuit. Therefore, the above-mentioned voltage Vm must be lower than the above-mentioned constant voltage of approximately 5 volts, which the voltage monitor has. Then, during this period, an appropriate threshold value exceeding Vm, such as Vs, should be set for the voltage level detected by the voltage monitoring circuit. This makes it possible to ascertain that a disconnection has occurred somewhere in the route extending from the end half portion  60  of the main conductive route to grounding through the power consumption device, when the voltage monitoring circuit detects a voltage level higher than the threshold value. Also, as a matter of course, when a voltage level of the end half portion  60  of the main conductive route abnormally rises close to the voltage level of the power supply device during this period when the first relay  30  is still in OFF state, it can be ascertained that there is a short-circuit failure with respect to the first relay  30 .  
         [0037]    Next, the first relay  30  is turned ON (conduction state) at the time t 2 , which is with a time lag of, for example, approximately 100 ms after the time t 1 . This allows the accumulator  10  to execute a regular power supply to the power consumption device through the main conductive routes  56 ,  58 , and  60 , provided that the circuit device and the power consumption device  20  are properly operating. When both the first relay  30  and the second relay  40  are turned ON, a voltage level detected by the voltage monitoring circuit must be Vb, which is a rated output voltage level of the accumulator  10 . Therefore, if a voltage level detected by the voltage monitoring circuit drastically drops below Vb, this means that a grounding short-circuit has occurred somewhere in the main conductive route. Such a grounding short-circuit can be detected by setting an appropriate predetermined threshold value Vt for a monitor voltage.  
         [0038]    When an operation of the power consumption device should be stopped, the second relay  40  is initially turned OFF at the time t 3 . When the second relay  40  is turned OFF, a voltage level at the end half portion  60  of the main conductive route is supposed to drop to zero. If the monitor voltage level is equal to or higher than Vo at this time, it can be ascertained that a connection of a circuit for re-grounding the end half portion  60  of the main conductive route has not been properly established by turning OFF the second relay  40 , which makes it possible to immediately detect an operation failure at the time of the grounding circuit recovery.  
         [0039]    When an operation of the power consumption device is stopped, it is acceptable to turn OFF the first relay  30  and the second relay  40  simultaneously. However, the figure shows an example in which a time point t 4  when the first relay  30  is turned OFF is delayed from the time point t 3  for approximately 100 ms. As shown in the figure, if a time difference is set between time points on which these two relays are turned OFF, a failure can be detected by each of the voltage monitoring circuit when a failure occurs in ON-OFF operations of either of the relays. In this case, turning ON the second relay  40  prior to turning ON the first relay  30  at the time of an activation of the power consumption device provides remarkable effects as described above. Therefore, it is possible to expand a capability of individual check with respect to the ON-OFF operations of the relays by turning OFF the first relay  30  after the second relay  40 , as shown in the example in the figure, so that an ON-OFF relation between the first relay  30  and second relay  40  at the time of an operation completion of the power consumption device becomes reverse of the relation at the time of activation of the power consumption device.  
         [0040]    Up to this point, the invention has been explained in detail with respect to one embodiment. It may be apparent for those skilled in the art that not only the invention is limited to such an embodiment, but also various embodiments are available within a scope of the invention