Patent Publication Number: US-11047328-B2

Title: Electromagnetic valve drive device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2018-181629, filed on Sep. 27, 2018, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an electromagnetic valve drive device. 
     Description of Related Art 
     Japanese Unexamined Patent Application, First Publication No. 2012-158985A discloses a fuel injection valve drive device which opens a fuel injection valve, by boosting a voltage of a battery (hereinafter referred to as a “battery voltage”) by a boost circuit, and supplying the boosted voltage (hereinafter referred to as an “output voltage”) to the fuel injection valve. 
     The boost circuit is configured to include an inductor, a first switch, a second switch, a diode, and an output capacitor. More specifically, one end of the inductor is connected to a battery power supply, and the other end thereof is connected to an anode of the diode. The first switch is connected between the other end of the inductor and a ground level. The second switch is connected in parallel with the diode. An output capacitor is connected between a cathode of the diode and the ground level. 
     With such a configuration, the fuel injection valve drive device accumulates energy in the inductor when the first switch is in an on-state and the second switch is in an off-state. Further, the fuel injection valve drive device can execute a synchronous rectification control of supplying the energy to the output capacitor via the second switch, by turning the second switch to the on-state after controlling the first switch such that it is brought into the off-state. 
     As a result, since the current flowing to the diode can be reduced, the heat generation of the diode can be suppressed and the loss can be reduced. 
     Incidentally, in the above-mentioned fuel injection valve drive device, when executing the synchronous rectification control, in order to prevent the first switch and the second switch from being simultaneously set to the turned-on state, a so-called dead time period is provided by setting the second switch to the turn-on state after measuring a predetermined time with a timer after executing the turn-off operation for the first switch. 
     However, when the resolution of time setting of the timer is low, it is necessary to set the dead time period to be longer than necessary from the viewpoint of safety. Therefore, in the synchronous rectification control, the period of time during which the first switch and the second switch are in the off-state becomes longer. As a result, the time for which the energy accumulated in the inductor is supplied to the output capacitor via the diode becomes longer, and it is not possible to improve the effect on the loss reduction of the diode due to the execution of the synchronous rectification control. 
     The present invention has been made in view of such circumstances, and an object thereof is to provide an electromagnetic valve drive device capable of suppressing heat generation caused by a diode in the synchronous rectification control. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is an electromagnetic valve drive device including: a boost circuit configured to be capable of executing a boosting operation of boosting an input voltage, by accumulating energy in an inductor when a first switch is in an on-state and a second switch is in an off-state, and by supplying the energy accumulated in the inductor to an output capacitor when the first switch is in the off-state and the second switch is in the on-state; a state detection unit configured to detect the on-state or the off-state of the first switch and the second switch; a boosting control unit configured to control the boosting operation, by performing a synchronous rectification control on switching of the first switch and the second switch, depending on the state of the first switch or the second switch detected by the state detection unit; and a drive circuit configured to drive the electromagnetic valve by supplying the voltage boosted by the boosting operation to the electromagnetic valve. 
     An aspect of the present invention is the electromagnetic valve drive device, wherein the boost control unit controls the second switch such that it is brought into the on-state from the off-state when the off-state of the first switch is detected by the state detection unit, and controls the first switch such that it is brought into the on-state from the off-state when the off-state of the second switch is detected. 
     An aspect of the present invention is the electromagnetic valve drive device wherein the first switch or the second switch enters the on-state or the off-state, depending on the voltage applied to the control terminal, and the state detection unit reads a voltage applied to a control terminal of the first switch or the second switch, and when the voltage value of the read voltage is equal to or less than a threshold value, the state detection unit determines that the first switch or the second switch is in the off-state. 
     An aspect of the present invention is the electromagnetic valve drive device wherein the first switch and the second switch are a MOSFET. 
     An aspect of the present invention is the electromagnetic valve drive device wherein the electromagnetic valve is a fuel injection valve configured to inject a fuel into an internal combustion engine. 
     As described above, according to the electromagnetic valve drive device of the above aspect, heat generation caused by the diode can be suppressed in the synchronous rectification control. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration diagram of a fuel injection valve drive device A according to an embodiment of the present invention. 
         FIG. 2  is a schematic configuration diagram of a control unit  3  according to an embodiment of the present invention. 
         FIG. 3  is a diagram illustrating a flow of a synchronous rectification control in the fuel injection valve drive device A according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, a fuel injection valve drive device according to an embodiment of the present invention will be described using drawings. 
     A fuel injection valve drive device A according to the present embodiment is a drive device that drives a fuel injection valve L. That is, the fuel injection valve drive device A according to the present embodiment is an electromagnetic valve drive device that drives the fuel injection valve L (an electromagnetic valve) that injects fuel to an internal combustion engine mounted on a vehicle. 
     As illustrated in  FIG. 1 , the fuel injection valve drive device A includes a boost circuit  1 , a drive circuit  2 , and a control unit  3 . 
     The boost circuit  1  is a chopper circuit capable of executing a boosting operation for boosting a battery voltage VB that is input from a battery BT mounted on a vehicle to a predetermined target voltage (a boosted voltage Vc). The boost circuit  1  generates a predetermined boosted voltage Vc from the battery voltage VB by executing the boosting operation. The boost circuit  1  has a boosting ratio of, for example, about ten to several tens, and the boosting operation is controlled by the control unit  3 . Further, the boost circuit  1  has functions of both synchronous rectification and asynchronous rectification. Here, the battery voltage VB is an example of the “input voltage” of the present invention. 
     The drive circuit  2  supplies the battery voltage VB or the boosted voltage Vc to the fuel injection valve L on the basis of the drive signal from control unit  3 . For example, when the drive circuit  2  acquires a first drive signal from the control unit  3 , the drive circuit  2  opens the fuel injection valve L, by supplying the boosted voltage Vc to the fuel injection valve L. Further, when the drive circuit  2  acquires a second drive signal from the control unit  3 , the drive circuit  2  maintains the open state of the fuel injection valve L after the valve opening, by supplying the battery voltage VB to the fuel injection valve L. 
     The control unit  3  is, for example, an integrated circuit (IC) that controls the boost circuit  1  and the drive circuit  2  on the basis of a command signal that is input from an upper control system. 
     A configuration of the boost circuit  1  according to an embodiment of the present invention will be specifically described below with reference to  FIG. 2 . 
     As illustrated in  FIG. 2 , the boost circuit  1  includes a shunt resistor  11 , an inductor  12 , a first switch  13 , a second switch  14 , a rectifying diode  15 , and an output capacitor  16 . 
     One end of the shunt resistor  11  is connected to a positive terminal of the battery BT, and the other end thereof is connected to one end of the inductor  12 . 
     The other end of the inductor  12  is connected to the first switch and the second switch. Further, the other end of the inductor is connected to the anode of the rectifying diode  15 . 
     The first switch  13  is a metal oxide semiconductor field effect transistor (MOSFET). A drain terminal of the first switch  13  is connected to the other end of the inductor  12 , and a source terminal thereof is connected to a negative terminal of the battery BT. Further, a gate terminal (a control terminal) of the first switch  13  is connected to the control unit  3 . 
     The second switch  14  is a MOSFET. A source terminal of the second switch  14  is connected to the other end of the inductor  12  and the drain terminal of the first switch  13 , and a drain terminal thereof is connected to one end of the output capacitor  16 . Further, a gate terminal (control terminal) of the second switch  14  is connected to the control unit  3 . The second switch  14  is a synchronous rectification element in the boost circuit  1  and is a MOSFET having a small on-resistance. 
     The rectifying diode  15  is connected in parallel to the second switch  14 . That is, an anode of the rectifying diode  15  is connected to the source terminal of the second switch  14 , and a cathode thereof is connected to the drain terminal of the second switch  14 . Further, the rectifying diode  15  is an asynchronous rectification element in the boost circuit  1 . 
     One end of the output capacitor  16  is connected to the cathode of the rectifying diode  15 , the drain terminal of the second switch  14 , and the drive circuit  2 . Further, the other end of the output capacitor  16  is connected to the negative terminal of the battery BT. 
     The configuration of the control unit  3  according to an embodiment of the invention will be specifically described below using  FIG. 2 . 
     The control unit  3  includes a current detection unit  31 , a state detection unit  32 , a boost control unit  33 , a voltage detection unit  34 , and a drive control unit  35 . 
     The current detection unit  31  detects a current value (hereinafter, referred to as a “charging current value”) flowing through the inductor  12  via the shunt resistor  11 . Specifically, the current detection unit  31  detects the charge current value, by measuring a potential difference between both ends of the shunt resistor  11 . 
     The state detection unit  32  detects the on-state or the off-state of the first switch  13  and the second switch  14 . That is, the state detection unit  32  detects whether the first switch  13  is in the on-state or the off-state. Further, the state detection unit  32  detects whether the second switch  14  is in the on-state or the off-state. 
     For example, the state detection unit  32  is connected to the gate terminal of the first switch  13 , and acquires a voltage (hereinafter referred to as a “gate voltage”) Vg 1  of the gate terminal. Further, when the acquired gate voltage Vg 1  of the first switch  13  is equal to or higher than a first threshold value Vth 1 , the state detection unit  32  determines that the first switch  13  is in the on-state. The first threshold value Vth 1  is a gate voltage required to turn on the first switch  13 . 
     Further, when the acquired gate voltage Vg 1  of the first switch  13  is equal to or less than a second threshold value Vth 2  (&lt;first threshold value Vth 1 ), the state detection unit  32  determines that the first switch  13  is in the off-state. The second threshold value Vth 2  is a gate voltage at which the first switch  13  is in the off-state. 
     For example, the state detection unit  32  is connected to the gate terminal of the second switch  14 , and acquires the gate voltage Vg 2  of the gate terminal. Further, when the acquired gate voltage Vg 2  of the second switch  14  is equal to or higher than a third threshold value Vth 3 , the state detection unit  32  determines that the second switch  14  is in the on-state. The third threshold value Vth 3  is a gate voltage required to set the second switch  14  to the on-state. 
     Further, when the acquired gate voltage Vg 2  of the second switch  14  is equal to or less than a fourth threshold value Vth 4  (&lt;third threshold value Vth 3 ), the state detection unit  32  determines that the second switch  14  is in the off-state. The fourth threshold value Vth 4  is a voltage at which the second switch  14  is in the off-state. 
     The boost control unit  33  is connected to each of the gate terminals of the first switch  13  and the second switch  14 . The boost control unit  33  controls the on-state or the off-state of the first switch  13  and the second switch  14  to execute the boosting operation of the boost circuit  1 . Specifically, the boost control unit  33  outputs the first control signal to the gate terminal of the first switch  13  to control the first switch  13  to the on-state. Further, the first control signal is a voltage equal to or higher than the first threshold value Vth 1 . The boost control unit  33  outputs the second control signal to the gate terminal of the second switch  14  to control the second switch  14  to the on-state. Further, the second control signal is a voltage equal to or higher than the third threshold value Vth 3 . 
     Here, one of the features of the boost control unit  33  according to the present embodiment is to perform a synchronous rectification control of switching of the first switch  13  and the second switch  14  to execute the boosting operation, depending on the state of the first switch  13  or the second switch  14  detected by the state detection unit  32 . That is, the boost control unit  33  certainly checks that the first switch  13  is in the off-state, and controls the second switch  14  to the on-state after the checking. This makes it possible to prevent the first switch  13  and the second switch  14  from being simultaneously in the on-state without using a timer. 
     The voltage detection unit  34  detects the voltage that is output from the boost circuit  1 , that is, the boosted voltage Vc. For example, the voltage detection unit  34  detects the boosted voltage Vc by resistive-dividing and acquiring the voltage (boosted voltage Vc) that is output from one end of the output capacitor  16 . The voltage detection unit  34  outputs the detected boosted voltage Vc to the drive control unit  35 . 
     The drive control unit  35  controls the drive circuit  2 . Specifically, the drive control unit  35  outputs the first drive signal to the drive circuit  2  when the boosted voltage Vc detected by the voltage detection unit  34  becomes equal to or higher than a predetermined value. 
     Further, the drive control unit  35  outputs the second drive signal to the drive circuit  2  to hold the valve opening of the fuel injection valve L after the valve opening. 
     Hereinafter, the operation of the fuel injection valve drive device A according to an embodiment of the present invention will be described in detail. First, the operation of the fuel injection valve drive device A with respect to the fuel injection valve L will be described. 
     When the fuel injection valve L is driven from the closed state to the opened state by the fuel injection valve drive device A, the drive control unit  35  supplies the boosted voltage Vc generated by the boost circuit  1  to the fuel injection valve L. Therefore, first, the boost control unit  33  performs the synchronous rectification control of the switching of the first switch  13  and the second switch  14 , thereby performing the boosting operation on the boost circuit  1  to generate the boosted voltage Vc. 
     Further, the drive control unit  35  supplies the boosted voltage Vc to the fuel injection valve L when the boosted voltage Vc detected by the voltage detection unit  34  becomes equal to or greater than a predetermined value. As a result, a peak rising current flows to the fuel injection valve L. Such a peak rising current speeds up the valve opening operation of the fuel injection valve L. 
     When the fuel injection valve L is opened, the drive control unit  35  supplies the battery voltage BT lower than the boosted voltage Vc to the fuel injection valve L to maintain the open state of the fuel injection valve L. As a result, the open state of the fuel injection valve L is maintained. 
     Next, the operation of the synchronous rectification control in the fuel injection valve drive device A will be described with reference to  FIG. 3 . 
     First, the boost control unit  33  outputs the first control signal to the gate terminal of the first switch  13  to set the first switch  13  to the on-state when the second switch  14  is in the off-state (step S 101 ). As a result, the gate voltage Vg 1  of the first switch  13  rises, and when the gate voltage Vg 1  becomes equal to or higher than the first threshold value Vth 1 , the switch enters the on-state. Thus, the battery voltage BT is applied to the inductor  12  and energy is accumulated in the inductor  12 . 
     After outputting the first control signal, the boost control unit  33  determines whether the charging current value detected by the current detection unit  31  has reached a preset current upper limit threshold value (step S 102 ). When it is determined that the charging current value detected by the current detection unit  31  has reached the current upper limit threshold value, the boost control unit  33  stops the output of the first control signal to control the first switch  13  to the off-state (step S 103 ). On the other hand, when it is determined that the charging current value detected by current detection unit  31  does not reach the current upper limit threshold value, the boost control unit  33  continues outputting the first control signal, and performs the process of step S 102  again. 
     When the output of the first control signal is stopped by the boost control unit  33 , the voltage value of the gate voltage Vg 1  gradually decreases, and the first switch  13  enters the off-state when the voltage becomes equal to or less than the second threshold value Vth 2 . Therefore, when the output of the first control signal is stopped by the boost control unit  33 , the state detection unit  32  acquires the gate voltage Vg 1  of the first switch  13  in a constant cycle (step S 104 ), and determines whether the acquired gate voltage Vg 1  is equal to or less than a second threshold value Vth 2  (step S 105 ). 
     When it is determined that the gate voltage Vg 1  is equal to or less than the second threshold value Vth 2 , the state detection unit  32  determines that the first switch  13  changes from the on-state to the off-state. Further, when the state detection unit  32  determines that the first switch  13  changes from the on-state to the off-state, the boost control unit  33  outputs the second control signal to control the second switch  14  to the on-state (step S 106 ). Therefore, when the second switch  14  is turned on, it is possible to prevent the first switch  13  and the second switch  14  from simultaneously entering the on-state without using a timer. That is, when the second switch  14  is turned on, it is possible to prevent the first switch  13  and the second switch  14  from simultaneously entering the on-state, without setting the dead time period to be longer than necessary. 
     When the second control signal is output to the second switch  14 , the voltage value of the gate voltage Vg 2  gradually increases, and the second switch  14  enters the on-state when the voltage becomes equal to or higher than the third threshold value Vth 3 . Here, the energy accumulated in the inductor  12  is supplied to the output capacitor  16  via the rectifying diode  15  until the second switch  14  is in the on-state. Further, when the second switch  14  is in the on-state, the energy accumulated in the inductor  12  is supplied to the output capacitor  16  via the second switch  14 . 
     After outputting the second control signal, the boost control unit  33  determines whether the charging current value detected by the current detection unit  31  has become equal to or less than a preset current lower limit threshold value (&lt;current upper limit threshold) (step S 107 ). When it is determined that the charging current value detected by the current detection unit  31  has become equal to or less than the current lower limit threshold value, the boost control unit  33  stops the output of the second control signal to control the second switch  14  to the off-state (step S 108 ). On the other hand, when it is determined that the charging current value detected by the current detection unit  31  does not become equal to or lower than the current lower limit threshold value, the boost control unit  33  continues outputting the second control signal, and performs the process of step S 107  again. 
     When the output of the second control signal is stopped by the boost control unit  33 , the voltage value of the gate voltage Vg 2  gradually decreases, and the second switch  14  enters the off-state when the voltage value becomes equal to or less than the fourth threshold value Vth 4 . Therefore, when the boost control unit  33  stops the output of the second control signal, the state detection unit  32  acquires the gate voltage Vg 2  of the second switch  14  at a constant cycle (step S 109 ), and determines whether the acquired gate voltage Vg 2  becomes equal to or less than the fourth threshold value Vth 4  (step S 110 ). Further, when it is determined that the gate voltage Vg 2  becomes equal to or less than the second threshold value Vth 2 , the state detection unit  32  determines that the second switch  14  is switched from the on-state to the off-state. 
     When the state detection unit  32  determines that the second switch  14  changes from the on-state to the off-state, the boost control unit  33  returns to the process of step S 101 , and outputs the first control signal to control the first switch  13  to the on-state. Thus, even when the first switch  13  is turned on, it is possible to prevent the first switch  13  and the second switch  14  from simultaneously entering the on-state without using a timer. That is, even when the first switch  13  is turned on, the first switch  13  and the second switch  14  can be prevented from simultaneously entering the on-state without setting the dead time period to be longer than necessary. 
     As described above, the fuel injection valve drive device A according to an embodiment of the present invention includes: the state detection unit  32  configured to detect the on-state or the off-state of the first switch  13  and the second switch  14 ; and the boosting control unit  33  configured to control the boosting operation, by performing a synchronous rectification control on switching of the first switch  13  and the second switch  14 , depending on the state of the first switch  13  or the second switch  14  detected by the state detection unit  32 . 
     According to such a configuration, since there is no need for set the dead time period by the timer, the dead time period does not become longer than necessary. This makes it possible to shorten the time for which the energy accumulated in the inductor  12  is supplied to the output capacitor  16  via the rectifying diode  15 . Therefore, in the synchronous rectification control, the heat generation due to the rectifying diode  15  can be suppressed, and the effect of loss reduction of the rectifying diode  15  can be enhanced. 
     Furthermore, since the charging efficiency to the output capacitor  16  can be improved by the reduction of the loss of the rectifying diode  15 , the boost recovery capability of the boost circuit  1  can be improved. The boost recovery capability is to raise the boosted voltage Vc, which is lower than the opening of the fuel injection valve L, to a voltage value (predetermined value) necessary to open the fuel injection valve L again. That is, the fuel injection valve drive device A can shorten the time for raising the boosted voltage Vc, which is lower than the opening of the fuel injection valve L, to a predetermined value again, which contributes to the performance improvement of multi-stage injection. 
     The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and also includes design and the like within the scope of the present invention. 
     Although the aforementioned embodiment has described the case where the first switch  13  and the second switch  14  are a MOSFET, this invention is not limited thereto. For example, the first switch  13  and the second switch  14  may be an insulated gate bipolar transistor (IGBT), a relay, or the like. 
     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims. 
     EXPLANATION OF REFERENCES 
     
         
         
           
             A Fuel injection valve drive device 
               1  Boost circuit 
               2  Drive circuit 
               3  Control unit 
               12  Inductor 
               13  First switch 
               14  Second switch 
               15  Rectifying diode 
               16  Output capacitor 
               31  Current detection unit 
               32  State detection unit 
               33  Boost control unit 
               34  Voltage detection unit 
               35  Drive control unit 
             L Fuel injection valve