Patent Publication Number: US-2022239295-A1

Title: Load Drive Device and Control Method of Load Drive Device

Description:
TECHNICAL FIELD 
     The present invention relates to a configuration of a load drive device that drives and controls an inductive load such as a solenoid valve and control thereof, and particularly relates to a technique that is effective when applied to an in-vehicle load drive device in which stability (linearity) of control is required. 
     BACKGROUND ART 
     Conventionally, in a vehicle automatic transmission (transmission system), a mechanism for driving a plurality of solenoid valves has been used. In a general transmission system, a plurality of inductive loads are connected to one controller (load drive device), and vehicle sides of the inductive loads are a common wiring for the purpose of reducing the number of connector terminals and reducing the size. 
     As a background art of the present technical field, for example, there is a technique such as PTL 1. PTL 1 discloses a “harness wiring method capable of reducing noise radiation and improving immunity of a solenoid valve control circuit”, in which one ends of a plurality of solenoid valves are a common wiring with respect to a connection portion of the plurality of solenoid valves and a control device therefor. 
     PTL 2 discloses a “drive device that achieves highly accurate current control based on a voltage across a flow detection resistor, and enables detection of disconnection of a common wiring by simultaneously detecting a direction of an energizing current”, and it is determined that a disconnection abnormality of a common wiring has occurred based on a current change in a common current path monitored by a current monitoring unit of each control drive unit. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2016-97850 A 
     PTL 2: WO 2017/057682 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     As described above, in a case where a plurality of inductive loads are connected to one load drive device and vehicle sides (sides opposite to the sides connected to the load drive device) of the inductive loads are connected by a common wiring, there is a concern about an influence of a reverse current in which a current flows from one inductive load to the other inductive load. 
     In the conventional load drive device, when the reverse current is detected, the operation of the load drive device is stopped, and there is a possibility that it is determined as abnormal although the common wiring is in a normal state. 
     In a vehicle automatic transmission (transmission system), when an operation of a load drive device is temporarily stopped, a speed change shock is deteriorated, that is, stability (linearity) of control is deteriorated, and ride comfort (driving comfort) of an occupant is deteriorated. 
     Therefore, an object of the present invention is to provide a load drive device with high stability (linearity) and a control method thereof capable of continuing a normal operation without stopping the load drive device even when a reverse current is temporarily detected with a specific inductive load in the load drive device in which a plurality of inductive loads are connected in parallel. 
     Solution to Problem 
     In order to solve the above problems, the present invention provides a load drive device, including: a first switch element; a second switch element; a current and direction detection unit that detects a current flowing through the first switch element in a forward direction and a reverse direction; a current and direction detection unit that detects a current flowing through the second switch element in the forward direction and the reverse direction; a control unit that calculates an average current based on signals from the current and direction detection units; a drive unit that drives the first switch element and the second switch element based on a deviation between the average current and a target current; and a plurality of inductive loads in which one end portions are connected to a common current path of the first switch element and the second switch element, and wirings for another end portions are connected to a common wiring at one point, in which a reverse current is detected by the current and direction detection unit when the second switch element is turned on, and a current is continuously monitored even when the average current calculated by the control unit is in a direction reverse to a normal direction. 
     Further, the present invention provides a control method of a load drive device in which a plurality of inductive loads are connected in parallel, the control method including: detecting a current value and a current direction of each of the plurality of inductive loads; comparing a detected current value with a predetermined threshold when a detected current direction is a direction reverse to a predetermined current direction; and continuing an operation of the load drive device when the detected current value is smaller than the predetermined threshold. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to realize the load drive device with high stability (linearity) and the control method thereof capable of continuing the normal operation without stopping the load drive device even when a reverse current is temporarily detected with a specific inductive load in the load drive device in which the plurality of inductive loads are connected in parallel. 
     As a result, in a vehicle automatic transmission (transmission system) that drives and controls a plurality of solenoid valves, it is possible to reduce a scene where a speed change shock is deteriorated, and ride comfort (driving comfort) of an occupant is improved. 
     Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a circuit configuration of a typical load drive device in a conventional vehicle automatic transmission (transmission system). 
         FIG. 2  is a diagram illustrating a circuit configuration of a load drive device according to a first embodiment of the present invention. 
         FIG. 3  is a timing chart illustrating an operation (action) of the load drive device of  FIG. 1 . 
         FIG. 4  is a timing chart illustrating an operation (action) of the load drive device of  FIG. 2 . 
         FIG. 5  is a flowchart illustrating an operation flow of an abnormality diagnosis function of a common wiring in the load drive device of  FIG. 1 . 
         FIG. 6  is a flowchart illustrating an operation flow of an abnormality diagnosis function of a common wiring in the load drive device of  FIG. 2 . 
         FIG. 7  is a diagram illustrating a circuit configuration of a load drive device according to a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and the detailed description of overlapping portions is omitted. 
     First Embodiment 
     A configuration of a load drive device and a control method thereof according to a first embodiment of the present invention will be described with reference to  FIGS. 1 to 6 . 
     In order to make the configuration of the present embodiment easy to understand, first, a conventional load drive device will be described with reference to  FIGS. 1, 3, and 5 .  FIG. 1  is a circuit configuration diagram of a conventional general load drive device illustrated as a comparative example. 
     As illustrated in  FIG. 1 , the conventional load drive device includes driver units Dr 1 - 1  to Dr 1 - 5 , a control unit  1 - 9  that controls each driver unit of the driver units Dr 1 - 1  to Dr 1 - 5 , and a connector terminal Co 1  capable of connecting a plurality of inductive loads in parallel. 
     The driver unit Dr 1 - 1  includes a first switch element  1 - 1 , a second switch element  1 - 2 , a first current detection switch element  1 - 3  connected in parallel to the first switch element  1 - 1 , a second current detection switch element  1 - 4  connected in parallel to the second switch element  1 - 2 , a current detection unit  1 - 5  for the first current detection switch element  1 - 3 , a current detection unit  1 - 6  for the second current detection switch element  1 - 4 , a first PWM drive unit  1 - 7  that drives the first switch element  1 - 1  and the first current detection switch element  1 - 3 , a second PWM drive unit  1 - 8  that drives the second switch element  1 - 2  and the second current detection switch element  1 - 4 , a current detection resistor  1 - 10  connected to a common current path of the first switch element  1 - 1  and the second switch element  1 - 2 , and a current and direction detection unit  1 - 11  that detects a current and a direction based on a voltage across the current detection resistor  1 - 10 . 
     The control unit  1 - 9  calculates an average current based on signals from the current detection unit  1 - 5  and the current detection unit  1 - 6 . 
     The driver units Dr 1 - 2  to Dr 1 - 5  have the same function as the driver unit Dr 1 - 1 . 
     The driver units Dr 1 - 1  to Dr 1 - 5  are connected to the connector terminal Co 1 . Connector terminals Co 1 - 1  to Co 1 - 5  which are one end portions of inductive loads SL 1 - 1  to SL 1 - 5  are respectively connected to the driver units Dr 1 - 1  to Dr 1 - 5 , and the other ends of the inductive loads SL 1 - 1  to SL 1 - 5  are respectively connected to a common wiring  1 - 17  via wirings  1 - 12  to  1 - 16 . 
       FIG. 3  is a timing chart illustrating an operation (action) of the conventional load drive device illustrated in  FIG. 1 . A to D of  FIG. 3  illustrate operations of A to D of  FIG. 1 , respectively. As illustrated in timing charts  3 - 1  and  3 - 2  of  FIG. 3 , by alternately turning on and OFF the first switch element  1 - 1  and the second switch element  1 - 2 , a current flows into the inductive load SL 1 - 1  as illustrated in a timing chart  3 - 4 . 
     At this time, when the current flows to the inductive load SL 1 - 2  as illustrated in a timing chart  3 - 3 , the current (reverse current) also flows to the inductive load SL 1 - 1 . As illustrated in the timing chart  3 - 4 , the difference between the inflow current (reverse current) and the magnitude of the current flowing from the driver unit Dr 1 - 1  to the inductive load SL 1 - 1  is the current of the inductive load SL 1 - 1 . 
     When the current flows in the direction reverse to the normal direction in the inductive load SL 1 - 1 , the current and direction detection unit  1 - 11  detects the reverse current, determines that the common wiring  1 - 17  is disconnected, sets a disconnection flag in the control unit  1 - 9  as illustrated in the timing chart  3 - 5 , and turns OFF both the first switch element and the second switch element of each of the driver units Dr 1 - 1  to Dr 1 - 5  to stop the operations of the driver units Dr 1 - 1  to Dr 1 - 5 . 
       FIG. 5  is a flowchart illustrating an operation flow of an abnormality diagnosis function of the common wiring  1 - 17  in the load drive device of  FIG. 1 . In any one of the driver units Dr 1 - 1  to Dr 1 - 5 , it is determined whether or not a reverse current has flowed when the second switch element is turned on (step  5 - 1 ). When it is determined that the current detected by the current and direction detection unit  1 - 11  is in the normal direction (NO), the disconnection flag is turned OFF (step  5 - 2 ), and the normal operations of the driver units Dr 1 - 1  to Dr 1 - 5  are continued. 
     On the other hand, when it is determined in step  5 - 1  that the current detected by the current and direction detection unit  1 - 11  is in the direction reverse to the normal direction (reverse current) (YES), the disconnection flag is turned ON (step  5 - 3 ), and both the first switch element and the second switch element held by each of the driver units Dr 1 - 1  to Dr 1 - 5  are turned OFF, so that the operations of all the drivers (driver units Dr 1 - 1  to Dr 1 - 5 ) are stopped (step  5 - 4 ). As a result, a speed change shock is deteriorated, and driving comfort is significantly deteriorated. 
     Next, the load drive device according to the present embodiment will be described with reference to  FIGS. 2, 4 , and  6 . 
     &lt;&lt;Configuration of Load Drive Device&gt;&gt; 
       FIG. 2  is a circuit configuration diagram of the load drive device according to the present embodiment. As illustrated in  FIG. 2 , the load drive device according to the present embodiment includes driver units Dr 2 - 1  to Dr 2 - 5 , a control unit  2 - 9  that controls each driver unit of the driver units Dr 2 - 1  to Dr 2 - 5 , and a connector terminal Co 2  capable of connecting a plurality of inductive loads in parallel. 
     The driver unit Dr 2 - 1  includes a first switch element  2 - 1 , a second switch element  2 - 2 , a first current detection switch element  2 - 3  connected in parallel to the first switch element  2 - 1 , a second current detection switch element  2 - 4  connected in parallel to the second switch element  2 - 2 , a current and direction detection unit  2 - 5  for the first current detection switch element  2 - 3 , a current and direction detection unit  2 - 6  for the second current detection switch element  2 - 4 , a first PWM drive unit  2 - 7  that drives the first switch element  2 - 1  and the first current detection switch element  2 - 3 , and a second PWM drive unit  2 - 8  that drives the second switch element  2 - 2  and the second current detection switch element  2 - 4 . 
     The control unit  2 - 9  calculates an average current based on signals from the current and direction detection unit  2 - 5  and the current and direction detection unit  2 - 6 . 
     The driver units Dr 2 - 2  to Dr 2 - 5  have the same function as the driver unit Dr 2 - 1 . 
     The driver units Dr 2 - 1  to Dr 2 - 5  are connected to the connector terminal Co 2 . Connector terminals Co 2 - 1  to Co 2 - 5  which are one end portions of inductive loads SL 2 - 1  to SL 2 - 5  are respectively connected to the driver units Dr 2 - 1  to Dr 2 - 5 , and the other ends of the inductive loads SL 2 - 1  to SL 2 - 5  are respectively connected to a common wiring  2 - 15  via wirings  2 - 10  to  2 - 14 . 
     &lt;&lt;Feedback Control Based on Reverse Current&gt;&gt; 
       FIG. 4  is a timing chart illustrating an operation (action) of the load drive device according to the present embodiment illustrated in  FIG. 2 . A to D of  FIG. 4  illustrate operations of A to D of  FIG. 2 , respectively. As illustrated in timing charts  4 - 1  and  4 - 2  of  FIG. 4 , by alternately turning ON and OFF the first switch element  2 - 1  and the second switch element  2 - 2 , a current flows into the inductive load SL 2 - 1  as illustrated in a timing chart  4 - 4 . 
     At this time, when the current flows to the inductive load SL 2 - 2  as illustrated in a timing chart  4 - 3 , the current (reverse current) also flows to the inductive load SL 2 - 1 . As illustrated in the timing chart  4 - 4 , the difference between the inflow current (reverse current) and the magnitude of the current flowing from the driver unit Dr 2 - 1  to the inductive load SL 2 - 1  is the current of the inductive load SL 2 - 1 . 
     Even when this current flows in the direction reverse to the normal direction in the inductive load SL 2 - 1 , monitoring of the average current is continued in the control unit  2 - 9 , and feedback control can be performed based on the divergence between the temporary transient reverse current that changes with time and a target value, so that a target current value can be held with high accuracy even in a low indicator current region. 
     As a result, even when the instruction current calculated by the control unit  2 - 9  is OA, OA can be reliably held while the feedback control is continued. 
     &lt;&lt;Operation Flow of Common Wiring Abnormality Diagnosis Function&gt;&gt; 
     In an abnormality diagnosis function of the common wiring  2 - 15 , it is determined that the common wiring  2 - 15  is abnormal (for example, disconnected) when the average current calculated by the control unit  2 - 9  is in the direction reverse to the normal direction and exceeds a predetermined abnormality determination threshold. 
     An operation flow of the abnormality diagnosis function according to the present embodiment is illustrated in  FIG. 6 . In any one of the driver units Dr 2 - 1  to Dr 2 - 5 , it is determined whether or not a reverse current has flowed when the second switch element is turned ON (step  6 - 1 ). When it is determined that the current detected by the current and direction detection unit  2 - 6  or the average current calculated by the control unit  2 - 9  is in the normal direction (NO), a disconnection flag is turned OFF (step  6 - 2 ), and the normal operations of the driver units Dr 2 - 1  to Dr 2 - 5  are continued. 
     On the other hand, when it is determined in step  6 - 1  that the current detected by the current and direction detection unit  2 - 6  or the average current calculated by the control unit  2 - 9  is in the direction reverse to the normal direction (reverse current) (YES), it is determined whether or not the magnitude of the current in the reverse direction is a predetermined value (predetermined threshold) or larger (step  6 - 3 ). 
     When the magnitude of the current in the reverse direction is smaller than the predetermined threshold (NO), the disconnection flag is turned OFF (step  6 - 2 ), and the normal operations of the driver units Dr 2 - 1  to Dr 2 - 5  are continued. 
     When the magnitude of the current in the reverse direction is equal to or larger than the predetermined value (predetermined threshold) (YES), the disconnection flag is turned ON (step  6 - 4 ), and both the first switch element and the second switch element of each of the driver units Dr 2 - 1  to Dr 2 - 5  are turned OFF, so that the operations of the driver units Dr 2 - 1  to Dr 2 - 5  are stopped. 
     Therefore, in the reverse current region smaller than the abnormality determination threshold, the normal state is continued without stopping the operation of the load drive device, so that it is possible to reduce the scene in which the speed change shock is deteriorated. 
     &lt;&lt;Abnormality Determination Threshold&gt;&gt; 
     The abnormality determination threshold is set to a value having a constant margin with respect to the magnitude of the current at which the inductive loads SL 2 - 1  to SL 2 - 5  operate or the magnitude of the current at which the inductive loads SL 2 - 1  to SL 2 - 5  operate. 
     In the load drive device according to the present embodiment, the current and direction detection units  2 - 5  and  2 - 6  detect not only the magnitude of the current but also the flowing direction of the current, and even if the flowing direction of the average current calculated by the control unit  2 - 9  is in the direction reverse to the normal direction, the current is continuously monitored without stopping the driving of the inductive load SL 2 - 1  by the driver unit Dr 2 - 1 , as compared with the conventional technique. In the present embodiment, the current value and the current direction are detected for each of the plurality of switch elements constituting the load drive device. 
     Even when the flowing direction of the average current is the reverse direction, feedback control can be performed based on the divergence between the average current calculated by the control unit  2 - 9  and a target value, so that a target current value can be held with high accuracy even in a low indicator current region. 
     As described above, the load drive device according to the present embodiment includes the first switch element  2 - 1 , the second switch element  2 - 2 , the current and direction detection unit  2 - 5  that detects the current flowing through the first switch element  2 - 1  in the forward direction and the reverse direction, the current and direction detection unit  2 - 6  that detects the current flowing through the second switch element  2 - 2  in the forward direction and the reverse direction, the control unit  2 - 9  that calculates the average current based on the signals from the current and direction detection units  2 - 5  and  2 - 6 , the drive unit (driver unit Dr 2 - 1 ) that drives the first switch element  2 - 1  and the second switch element  2 - 2  based on the deviation between the average current and the target current, and the plurality of inductive loads SL 2 - 1  to SL 2 - 5  in which one end portions are connected to the common current path of the first switch element  2 - 1  and the second switch element  2 - 2 , and the wirings for the other end portions are connected to the common wiring  2 - 15  at one point, in which the reverse current is detected by the current and direction detection unit  2 - 5  when the second switch element  2 - 2  is turned ON, and the current is continuously monitored even when the average current calculated by the control unit  2 - 9  is in the direction reverse to the normal direction. 
     Even when the average current calculated by the control unit  2 - 9  is in the direction reverse to the normal direction, the average current is canceled, and the feedback control is continued so as to approach the target current. 
     In addition, the current detected by the current and direction detection unit  2 - 5  or the average current calculated by the control unit  2 - 9  has the abnormality determination threshold of the common wiring  2 - 15  in the current region in the direction reverse to the normal direction, and when the current or the average current exceeds the abnormality determination threshold, it is determined that the common wiring  2 - 15  is abnormal, and one inductive load SL 2 - 1  or the plurality of inductive loads SL 2 - 1  to SL 2 - 5  are controlled based on the abnormality determination process of the control unit  2 - 9 . 
     The abnormality determination threshold is set in the current region in the direction reverse to the normal direction so as to have a magnitude of the current being a magnitude for operating the inductive loads SL 2 - 1  to SL 2 - 5  or smaller than the magnitude. 
     Further, in the present embodiment ( FIG. 2 ), the common wiring  2 - 15  is a GND line connected to GND, and the second switch element  2 - 2  is a switch element connected to a low side. 
     According to the load drive device and the control method thereof according to the present embodiment, it is possible to realize the load drive device with high stability (linearity) and the control method thereof capable of continuing the normal operation without stopping the load drive device even when a reverse current is temporarily detected with a specific inductive load in the load drive device in which the plurality of inductive loads are connected in parallel. 
     As a result, in a vehicle automatic transmission (transmission system) that drives and controls a plurality of solenoid valves, it is possible to reduce a scene where a speed change shock is deteriorated, and ride comfort (driving comfort) of an occupant is improved. 
     In addition, the detectability of the abnormality diagnosis on the common wiring  2 - 15  can be improved, and the reliability of the load drive device can be improved. 
     Second Embodiment 
     A configuration of a load drive device and a control method thereof according to a second embodiment of the present invention will be described with reference to  FIG. 7 .  FIG. 7  is a circuit configuration diagram of the load drive device according to the present embodiment. 
     &lt;&lt;Configuration of Load Drive Device&gt;&gt; 
     In the first embodiment ( FIG. 2 ), the common wiring  2 - 15  is the GND line, and this is based on the assumption that the driving system of the inductive loads SL 2 - 1  to SL 2 - 5  is high-side driving. When the driving system of the inductive loads SL 2 - 1  to SL 2 - 5  is low-side driving, as illustrated in  FIG. 7 , the common wiring  2 - 15  is a battery line. 
     &lt;&lt;Operation Flow of Common Wiring Abnormality Diagnosis Function&gt;&gt; 
     A current flowing through the inductive loads SL 2 - 1  to SL 2 - 5  in the reverse direction flows into the first switch element  2 - 1 , and the current and direction detection unit  2 - 5  detects the current in the reverse direction. 
     Therefore, as in the present embodiment ( FIG. 7 ), in the operation flow in a case where the driving system of the inductive loads SL 2 - 1  to SL 2 - 5  is the low-side driving, in step  6 - 1  of  FIG. 6 , a reverse current flows when the first switch element is turned ON. 
     In the present embodiment ( FIG. 7 ), the common wiring  2 - 15  is a power supply (battery) line connected to a power supply VB, and the second switch element  2 - 2  is a switch element connected to a high side. 
     The present invention is not limited to the embodiments described above, but includes various modifications. 
     For example, the embodiments described above have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and further, the configuration of one embodiment can be added to the configuration of another embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. 
     INDUSTRIAL APPLICABILITY 
     In each of the embodiments described above, the load drive device of the vehicle automatic transmission (transmission system) including a linear solenoid valve has been described, but the present invention is also applicable to, for example, an inkjet printer valve, a massage chair, and the like using a plurality of solenoid valves as a pressure adjustment valve and a direction switching valve for oil or air. 
     REFERENCE SIGNS LIST 
     
         
           1 - 1  first switch element 
           1 - 2  second switch element 
           1 - 3  (first) current detection switch element 
           1 - 4  (second) current detection switch element 
           1 - 5  current detection unit (of first switch element) 
           1 - 6  current detection unit (of second switch element) 
           1 - 7  (first) PWM drive unit 
           1 - 8  (second) PWM drive unit 
           1 - 9  control unit 
           1 - 10  current detection resistor 
           1 - 11  current and direction detection unit 
           1 - 12  to  1 - 16  other end portion of inductive load (wiring) 
           1 - 17  common wiring 
         Co 1  connector terminal (of load drive device) 
         Co 1 - 1  to Co 1 - 5  one end portion of inductive load (connector terminal) 
         Dr 1 - 1  to Dr 1 - 5  driver unit 
         SL 1 - 1  to SL 1 - 5  inductive load 
           2 - 1  first switch element 
           2 - 2  second switch element 
           2 - 3  (first) current detection switch element 
           2 - 4  (second) current detection switch element 
           2 - 5  current and direction detection unit (of first switch element) 
           2 - 6  current and direction detection unit (of second switch element) 
           2 - 7  (first) PWM drive unit 
           2 - 8  (second) PWM drive unit 
           2 - 9  control unit 
           2 - 10  to  2 - 14  other end portion of inductive load (wiring) 
           2 - 15  common wiring 
         Co 2  connector terminal (of load drive device) 
         Co 2 - 1  to Co 2 - 5  one end portion of inductive load (connector terminal) 
         Dr 2 - 1  to Dr 2 - 5  driver unit 
         SL 2 - 1  to SL 2 - 5  inductive load 
           3 - 1  to  3 - 5  timing chart (at time of detection of reverse current in conventional technique) 
           4 - 1  to  4 - 5  timing chart (at time of detection of reverse current in first embodiment) 
           5 - 1  to  5 - 4  step (in flowchart at time of detection of reverse current in conventional technique) 
           6 - 1  to  6 - 5  step (in flowchart at time of detection of reverse current in first embodiment)