CONTROL CIRCUIT FOR SOLENOID VALVE

Abstract

A control circuit (20) for a solenoid valve (10) with a solenoid coil (58) is provided with: a current feedback bias circuit (100) comprising a transistor (Trf) in which a base electrode is connected to a pull-up resistor (Rfb1) and a pull-down resistor (Rfb2), an emitter electrode connected to an emitter resistor (Rfe) connected to ground, and a collector electrode connected to a load resistor (Rfc), and which amplifies the AC component of a first voltage (V1) according to a current flowing through the solenoid coil; and a voltage output circuit (102) which outputs a second voltage (V2), which changes according to the amplified AC component, to a determining device (40).

Description

TECHNICAL FIELD

[0001] The present invention relates to a control circuit for a solenoid valve. STATE OF THE ART

[0002] JP H09-097116 A discloses a coil actuator / iron core movement detection circuit for a solenoid valve. The coil actuator / iron core movement detection circuit supplies the electromagnetic coil of the solenoid valve with an excitation current and detects a change in the excitation current. Consequently, the movement of the movable iron core is detected, and the opening of the valve element of the solenoid valve is detected. SUMMARY OF THE INVENTION

[0003] The coil drive / iron core motion detection circuit for the solenoid valve disclosed in JP H09-097116 A is large. Therefore, a large installation space is required.

[0004] The present invention aims to solve the aforementioned problem.

[0005] One aspect of the present invention is characterized by a control circuit for a solenoid valve comprising a solenoid coil, wherein the control circuit comprises: a current feedback bias circuit comprising a transistor comprising a base, an emitter and a collector, wherein the base is connected to a pull-up resistor and a pull-down resistor configured to share a supply voltage supplied by a current source, wherein the emitter is connected to an emitter resistor connected to ground, the collector is connected to a load resistor connected to the current source, the current feedback bias circuit is configured to amplify an AC component of a first voltage corresponding to a current flowing through the solenoid coil, wherein the AC component is applied to the base;and a voltage output circuit configured to output a second voltage to a determining device, which changes according to the AC component amplified by the current feedback bias circuit, wherein the determining device is configured to determine the communication between an input terminal and an output terminal of the solenoid valve based on the second voltage.

[0006] According to the present invention, the size of the control circuit for the solenoid valve can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing an application example of a control circuit for a solenoid valve; Fig. Figure 2 is a diagram illustrating a change in the current flowing through a magnetic coil; Fig. Figure 3 is a diagram illustrating a configuration example of the control circuit; Fig. 4 is a diagram illustrating a change in voltage; and Fig. 5A and Fig. 5B are diagrams illustrating changes in voltage with temperature. DETAILED DESCRIPTION OF THE INVENTION

[0007] Fig. Figure 1 is a diagram showing an application example of a control circuit 20 for a solenoid valve 10. A main control device 30 controls the solenoid valve 10 via a drive / determination device 40 and the control circuit 20 based on operator input. The main control device 30 is, for example, a PC (personal computer) or a PLC (programmable logic controller). The main control device 30 can control multiple solenoid valves 10.

[0008] In the present embodiment, the actuator / control device 40 and the control circuit 20 are provided for each solenoid valve 10. The actuator / control device 40 and the control circuit 20 can be provided for several solenoid valves 10. The actuator / control device 40 and the control circuit 20 can be provided in the main control unit 30.

[0009] The drive / control device 40 includes a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The drive / control device 40 outputs a drive control signal to actuate the solenoid valve 10. Furthermore, the drive / control device 40 determines the communication between an input terminal 62 and an output terminal 64 of the solenoid valve 10 based on the voltage received from the control circuit 20. The configuration of the control circuit 20 will be described later with reference to Fig. 3 described. Low-voltage current is supplied from a current source 80 to the control circuit 20.

[0010] Fig. Figure 1 schematically shows the configuration of the solenoid valve 10. The solenoid valve 10 comprises a stationary iron core 52, a movable iron core 54, a spring 56, and a solenoid coil 58 within a housing 50. The movable iron core 54 can be brought into contact with a valve seat 60, formed in the housing 50 of the solenoid valve 10, by an elastic force (repulsive force) of the spring 56. The movable iron core 54, which is in contact with the valve seat 60, is in Fig. 1 represented by a two-point catenary as a movable iron core 54s.

[0011] The state in which the movable iron core 54 is in contact with the valve seat 60 is a closed state of the solenoid valve 10. In the closed state, the connection between the inlet port 62 and the outlet port 64 is blocked for any fluid formed in the housing 50 of the solenoid valve 10.

[0012] In the event that the actuator / control device 40 outputs an actuator control signal to the solenoid valve 10, electrical energy is supplied from the power source 80 to the solenoid coil 58. That is, a current flows through the solenoid coil 58. In this case, a magnetic force is generated. The magnetic force causes the movable iron core 54 to move against the spring force of the spring 56 in the direction of the stationary iron core 52. The movable iron core 54 is separated from the valve seat 60. The state in which the movable iron core 54 is separated from the valve seat 60 is an open state of the solenoid valve 10.

[0013] When the solenoid valve 10 is brought into the valve open state, the inlet port 62 and the outlet port 64 begin to communicate with each other. The fluid flows into the inlet port 62, flows from the inlet port 62 to the outlet port 64, and flows out of the outlet port 64. The movable iron core 54, which has continued to move and has reached the end of a movable section, is in Fig. 1 is represented by a solid line as the movable iron core 54e. When the movable iron core 54 has reached the end of the movable section, the solenoid valve 10 is in a fully open state.

[0014] Fig. Figure 2 is a diagram illustrating a change in the current flowing through the solenoid coil 58. At time T0, current begins to flow through the solenoid coil 58 of the solenoid valve 10, which is in the closed state. In this case, a force begins to develop that moves the movable iron core 54 (54s), which has brought the solenoid valve 10 into the closed state, towards the stationary iron core 52. However, the movable iron core 54 does not move until the force becomes greater than the spring force of the spring 56. During this time, the current flowing through the solenoid coil 58 increases.

[0015] At time TA, the force moving the movable iron core 54 of the solenoid valve 10 in the closed state balances the spring force of the spring 56. After time TA, the force becomes greater than the spring force of the spring 56. Therefore, the movable iron core 54 is separated from the valve seat 60 and begins to move within the solenoid coil 58. The solenoid valve 10 is thus opened. As the movable iron core 54 moves within the solenoid coil 58, the inductance of the solenoid coil 58 increases. Consequently, the current flowing through the solenoid coil 58 decreases.

[0016] At time TB, the movable iron core 54 (54e), having reached the end of the movable section, stops moving. When the movable iron core 54 stops moving, the inductance of the magnet coil 58 no longer changes. Therefore, after time TB, the current flowing through the magnet coil 58 increases. Then, at time TC, the increase in the current flowing through the magnet coil 58 stops. The movable iron core 54 remains stationary at the end of the movable section. After time TC, the current flowing through the magnet coil 58 is held at a constant value in a state where the movable iron core 54 is stationary.

[0017] A first voltage V1, obtained by subtracting the voltage drop caused by the solenoid coil 58 from the voltage supplied to the solenoid valve 10 by the power source 80 (e.g., 24 V), changes in the same way as the current flowing through the solenoid coil 58. That is, the first voltage V1 changes over time, as shown in Fig. 2 shown, corresponding to the current flowing through the magnetic coil 58.

[0018] At time TB, the solenoid valve 10 is brought into the fully open state. In this case, the input port 62 and the output port 64 are fully connected. There are instances in which the main control device 30 should detect a communication state between the ports, in which the input port 62 and the output port 64 are fully communicating. The main control device 30 can detect the communication state between the ports based on the first voltage V1. To detect the communication state between the ports, the control circuit 20 is used according to the present embodiment.

[0019] Fig. Figure 3 is a diagram illustrating a configuration example of the control circuit 20. The control circuit 20 outputs a second voltage V2 to the actuator / control device 40, which is derived from the first voltage V1 described above, corresponding to the current flowing through the solenoid coil 58. The second voltage V2 is described in detail later. The power source 80 comprises an actuator current source 80A for the solenoid valve 10 and a low-voltage current source 80B for the control circuit 20. A supply voltage Vref (for example, 3.3 V), which is lower than the voltage of the actuator current source 80A for the solenoid valve 10, is supplied to the control circuit 20 from the low-voltage current source 80B.

[0020] In Fig. 3. The processor of the drive / control device 40 outputs a voltage Vo as a drive control signal to the solenoid valve 10 from an output terminal 40o of the processor. The solenoid valve 10 comprises a transistor Trs, a solenoid coil Sv, a current-sensing resistor Rsense, a current-limiting resistor Rsb, and a coupling capacitor Ci.

[0021] The base of transistor Trs is connected via the current-limiting resistor Rsb to the output terminal 40 of the processor of the drive / determination device 40. The current-limiting resistor Rsb limits the current flowing through the base of transistor Trs. The emitter of transistor Trs is connected to the drive current source 80A, which outputs a supply voltage Vsup. As described above, the supply voltage Vsup is, for example, 24 V. The collector of transistor Trs is connected to the magnetic coil Sv.

[0022] The current-sense resistor Rsense is connected to a point P1, which corresponds to the other end of the magnetic coil Sv, located between the two ends of the magnetic coil Sv on the opposite side from the end connected to the collector of the transistor Trs. The current-sense resistor Rsense is connected to ground.

[0023] The transistor Trs is switched on by the voltage Vo output from terminal 40°. In this case, current from the 80A drive current source flows through the solenoid Sv. By connecting the current-sense resistor Rsense, which is linked to point P1 and ground, the first voltage V1 is obtained at point P1.

[0024] The coupling capacitor Ci is located between point P1 and the control circuit 20. The control circuit 20, which is supplied with the low supply voltage Vref from the low-voltage source 80B, is isolated by the coupling capacitor Ci from the solenoid valve 10, which is supplied with the supply voltage Vsup from the drive current source 80A. Circuit constants such as a resistance value and a capacitor capacitance used for the control circuit 20 can be determined independently of the solenoid valve 10. The coupling capacitor Ci removes the DC component from the first voltage V1 and extracts the AC component from the first voltage V1.

[0025] The control circuit 20 comprises a current feedback bias circuit 100, a voltage output circuit 102, and a coupling capacitor Co. The coupling capacitor Co of the control circuit 20 is located between the current feedback bias circuit 100 and the voltage output circuit 102. The current feedback bias circuit 100 comprises only one transistor Trf, which has a base, an emitter, and a collector. The base of the transistor Trf is connected to a pull-up resistor Rfb1 and a pull-down resistor Rfb2. The pull-up resistor Rfb1 is connected to the low-voltage current source 80B. The pull-down resistor Rfb2 is connected to ground.

[0026] That is, one end of the pull-up resistor Rfb1 is connected to the low-voltage current source 80B, and the other end of the pull-up resistor Rfb1 is connected to the pull-down resistor Rfb2. One end of the pull-down resistor Rfb2 is connected to the pull-up resistor Rfb1, and the other end of the pull-down resistor Rfb2 is connected to ground. It should be noted that in the present embodiment, the pull-up resistor Rfb1 and the pull-down resistor Rfb2 are contained within the current feedback bias circuit 100.

[0027] The base of transistor Trf is connected to point P2, which is located between pull-up resistor Rfb1 and pull-down resistor Rfb2. The coupling capacitor Ci of solenoid valve 10 is also connected to point P2. That is, both electrodes of coupling capacitor Ci are connected to point P1 of solenoid valve 10 and point P2 of current feedback bias circuit 100, respectively.

[0028] The emitter of transistor Trf is connected to an emitter resistor Rfe. The emitter resistor Rfe is connected to ground. That is, one end of the emitter resistor Rfe is connected to the emitter of transistor Trf, and the other end of the emitter resistor Rfe is connected to ground. It should be noted that in the present embodiment, the emitter resistor Rfe is included in the current feedback bias circuit 100.

[0029] The collector of transistor Trf is connected to a load resistor Rfc. The load resistor Rfc is connected to the low-voltage current source 80B. That is, one end of the load resistor Rfc is connected to the low-voltage current source 80B, and the other end of the load resistor Rfc is connected to the collector of transistor Trf. It should be noted that in the present embodiment, the load resistor Rfc is contained within the current feedback bias circuit 100.

[0030] The coupling capacitor Co of the control circuit 20 is connected to a point P3 located between the load resistor Rfc and the collector of the transistor Trf. The voltage output circuit 102 is isolated from the current feedback bias circuit 100 by the coupling capacitor Co. Circuit constants, such as a resistance value used for the voltage output circuit 102, can be determined independently of the current feedback bias circuit 100.

[0031] The voltage output circuit 102 comprises only one transistor Trp with a base, an emitter, and a collector. The base of transistor Trp is connected to a pull-up resistor Rpb1 and a pull-down resistor Rpb2. The pull-up resistor Rpb1 is connected to the low-voltage current source 80B. The pull-down resistor Rpb2 is connected to ground.

[0032] That is, one end of the pull-up resistor Rpb1 is connected to the low-voltage power source 80B, and the other end of the pull-up resistor Rpb1 is connected to the pull-down resistor Rpb2. One end of the pull-down resistor Rpb2 is connected to the pull-up resistor Rpb1, and the other end of the pull-down resistor Rpb2 is connected to ground. It should be noted that in the present embodiment, the pull-up resistor Rpb1 and the pull-down resistor Rpb2 are contained within the voltage output circuit 102.

[0033] The base of transistor Trp is connected to point P4, which is located between pull-up resistor Rpb1 and pull-down resistor Rpb2. The coupling capacitor Co of control circuit 20 is also connected to point P4. That is, both electrodes of coupling capacitor Co are connected to point P3 of current feedback bias circuit 100 and point P4 of voltage output circuit 102, respectively. The emitter of transistor Trp is connected to ground. Transistor Trp is an open-collector transistor.

[0034] The collector of transistor Trp is connected to a load resistor Rpc. The load resistor Rpc is connected to the low-voltage power source 80B. That is, one end of the load resistor Rpc is connected to the low-voltage power source 80B, and the other end of the load resistor Rpc is connected to the collector of transistor Trp. It should be noted that in the present embodiment, the load resistor Rpc is contained within the voltage output circuit 102.

[0035] An input terminal 40i of the processor of the drive / determination device 40 is connected to a point P5 located between the load resistor Rpc and the collector of transistor Trp. The voltage output circuit 102 (the collector of transistor Trp) outputs the second voltage V2 at point P5 to the processor of the drive / determination device 40. The second voltage V2 output by the voltage output circuit 102 is fed into input terminal 40i.

[0036] As described above, the first voltage V1 at point P1 changes over time, as shown in Fig. Figure 2 shows that the second voltage V2 at point P5 also changes over time in accordance with the time-dependent change of the first voltage V1. This is described below. First, the current feedback bias circuit 100 is described, which amplifies the AC component of the first voltage V1 extracted by the coupling capacitor Ci.

[0037] As described above, the solenoid valve 10 is connected to the drive power source 80A. The control circuit 20 is connected to the low-voltage power source 80B, whose supply voltage is lower than that of the drive power source 80A. The control circuit 20 is isolated from the solenoid valve 10 by the coupling capacitor Ci, which is located between point P1 and point P2.

[0038] Therefore, the voltage level of a voltage Vfb at point P2 in the current feedback bias circuit 100 is a voltage level that is shifted relative to the voltage level of the first voltage V1 at point P1 in the solenoid valve 10. The operating point of the transistor Trf, whose base is connected to point P2, corresponds to a voltage obtained by dividing the supply voltage Vref supplied by the low-voltage current source 80B by the pull-up resistor Rfb1 and the pull-down resistor Rfb2 of the current feedback bias circuit 100.

[0039] The voltage Vfb at point P2 is the AC component of the first voltage V1, which is extracted by the coupling capacitor Ci. The voltage Vfb at point P2 is amplified by transistor Trf of the current feedback bias circuit 100. The gain, corresponding to the amplification factor, is determined by the ratio between the resistance value of the load resistor Rfc connected to the collector of transistor Trf and the resistance value of the emitter resistor Rfe connected to the emitter of transistor Trf. Therefore, a voltage Vfc is obtained at point P3 in the current feedback bias circuit 100 that is amplified more than the voltage Vfb at point P2. The voltage Vfc changes in accordance with the voltage Vfb, which is the AC component of the first voltage V1.

[0040] Furthermore, the emitter of transistor Trf is connected to ground via the emitter resistor Rfe. Therefore, when the voltage Vfb at point P2 increases, the voltage Vfc at point P3 decreases, and conversely, when the voltage Vfb at point P2 decreases, the voltage Vfc at point P3 increases. That is, the waveform showing the change in voltage Vfc over time at point P3 is inverted with respect to the waveform showing the change in voltage Vfb at point P2. This characteristic will be discussed later with reference to… Fig. 4 described.

[0041] A DC voltage gain hfe and a base-emitter voltage Vbe of transistor Trf in the current feedback bias circuit 100 are determined as properties of transistor Trf. Furthermore, the supply voltage Vref of the low-voltage current source 80B is preset, for example, to 3.3 V. The ratio between the current flowing through the pull-up resistor Rfb1 and the current flowing through the base of transistor Trf, the resistance value of the emitter resistor Rfe, and the resistance value of the load resistor Rfc are determined according to the required specifications, such as the gain described above, during the design of the current feedback bias circuit 100. The resistance value of the pull-up resistor Rfb1 and the resistance value of the pull-down resistor Rfb2 can be determined based on the various constants obtained in this way.

[0042] Next, the voltage output circuit 102 is described. The coupling capacitor Co shifts the voltage level of the voltage Vfc at point P3 in the current feedback bias circuit 100. A voltage Vpb at point P4 in the voltage output circuit 102 is obtained corresponding to the voltage Vfc, whose voltage level has been shifted. The operating point of the transistor Trp, whose base is connected to point P4, corresponds to a voltage obtained by dividing the supply voltage Vref supplied by the low-voltage current source 80B by the pull-up resistor Rpb1 and the pull-down resistor Rpb2 of the voltage output circuit 102.

[0043] The voltage Vpb changes according to the voltage Vfc. Therefore, the voltage Vpb changes according to the voltage Vfb, which is the AC component of the first voltage V1. In the event that the voltage Vpb exceeds a voltage corresponding to the operating point of transistor Trp, transistor Trp is switched on. That is, the voltage corresponding to the operating point of transistor Trp acts as a predetermined threshold Vth for switching on transistor Trp. As described below, threshold control for changing the second voltage V2 can be implemented using the predetermined threshold Vth.

[0044] When transistor Trp is switched on, the second voltage V2 at point P5 in the voltage output circuit 102 becomes a ground potential VL. Therefore, if the voltage Vpb, which changes according to the voltage Vfb (the AC component of the first voltage V1), exceeds the predetermined threshold Vth, the collector of transistor Trp outputs the ground potential VL as the second voltage V2.

[0045] If the voltage Vpb is less than the predetermined threshold Vth, transistor Trp is switched off. When transistor Trp is in the off state, the second voltage V2 at point P5 in the voltage output circuit 102 becomes a predetermined voltage VH, which is higher than the ground potential VL. The predetermined voltage VH corresponds to the supply voltage Vref of the low-voltage current source 80B. Thus, if the voltage Vpb is below the predetermined threshold Vth, the collector of transistor Trp outputs the predetermined voltage VH as the second voltage V2.

[0046] As described above, the predetermined threshold Vth assumes a value corresponding to the supply voltage Vref of the low-voltage power source 80B and the resistance values ​​of the pull-up resistor Rpb1 and the pull-down resistor Rpb2 of transistor Trp. Therefore, the predetermined threshold Vth can be set in advance so that the on and off states of transistor Trp are switched appropriately according to the change in voltage Vpb at point P4. In this case, the resistance values ​​of the pull-up resistor Rpb1 and the pull-down resistor Rpb2 of transistor Trp are determined based on the set predetermined threshold Vth and the supply voltage Vref of the low-voltage power source 80B.

[0047] As described above, the second voltage V2, output by the collector of transistor Trp, is fed into the input terminal 40i of the processor of the drive / determination device 40. Therefore, the predetermined voltage VH can be determined according to the specifications of the processor or similar of the drive / determination device 40. The load resistor Rpc of the voltage output circuit 102 is chosen to have a resistance value sufficiently lower than the input impedance of input terminal 40i to ensure that the predetermined voltage VH is output by the collector of transistor Trp. However, it is preferable to use a design that prevents a large current from flowing through transistor Trp due to an excessively low resistance value of the load resistor Rpc.

[0048] The control / determination device 40 determines the communication between the input terminal 62 and the output terminal 64 of the solenoid valve 10 based on the second voltage V2, which is output by the voltage output circuit 102 and input to the input terminal 40i. When the second voltage V2 input to the input terminal 40i indicates the ground potential VL, it is determined that the movable iron core 54 has just reached the end of its moving section or that the movable iron core 54 will soon reach the end of its moving section. In this case, the point at which the input terminal 62 and the output terminal 64 of the solenoid valve 10 fully communicate with each other has arrived or is about to arrive.

[0049] If the second voltage V2, applied to the input terminal 40i, indicates the predetermined voltage VH, it is determined that the movable iron core 54 has not yet reached the end of the moving section, or that the movable iron core 54 has reached the end of the moving section and is no longer moving. In this case, the input terminal 62 and the output terminal 64 of the solenoid valve 10 are not fully connected, or a certain amount of time has passed since they were fully connected.

[0050] As from Fig. As can be seen in Figure 3, the current feedback bias circuit 100 comprises only one transistor. The voltage output circuit 102 also comprises only one transistor. Therefore, the control circuit 20 comprises only two transistors, which allows the size of the control circuit 20 to be kept small. The control circuit 20 is smaller than a circuit with many transistors, such as an operational amplifier or a comparator, and therefore does not require much installation space. Since the control circuit 20 comprises only two transistors, the second voltage V2 can also be output with low latency.

[0051] Furthermore, the coupling capacitor Ci isolates the control circuit 20 from the solenoid valve 10. Therefore, the supply voltage Vref supplied to the control circuit 20 by the low-voltage power source 80B can be lower than the supply voltage Vsup supplied to the solenoid valve 10 by the drive power source 80A. Since the control circuit 20 can consist of circuit elements that operate at a low voltage, the control circuit 20 can be implemented cost-effectively.

[0052] Fig. Figure 4 is a diagram illustrating a change in voltage. The diagram in Fig. 4 shown change of the first voltage V1 at point P1 (see Fig. 3) resembles the one in Fig. The change in the first voltage V1 shown in Figure 2 indicates that at time T0, current begins to flow through the solenoid coil 58 of the solenoid valve 10, which is in the closed state. At time TA, the movable iron core 54 begins to move. After time TA, the movable iron core 54 moves within the solenoid coil 58. At time TB, the movable iron core 54, having reached the end of its moving section, stops moving. After time TB, the movable iron core 54 remains stationary at the end of its moving section and no longer moves.

[0053] As above with reference to Fig. As described in section 2, the first voltage V1 rises in Fig. 4 from time T0 to time TA. At time TA, the movable iron core 54 begins to move. The first voltage V1 decreases from time TA to time TB while the movable iron core 54 moves within the solenoid coil 58. At time TB, the movable iron core 54 reaches the end of its moving section and stops. The first voltage V1 increases after time TB.

[0054] As described above, the voltage Vfb at point P2 (see Fig. 3) in the current feedback bias circuit 100, the AC component of the first voltage V1. As in Fig. As shown in Figure 4, the voltage Vfb changes from decreasing to increasing at time TB. As described above, the waveform of the voltage Vfc at point P3 (see Figure 4) is... Fig. 3) in the current feedback bias circuit 100 with respect to the waveform of the voltage Vfb at point P2, the voltage Vfc changes as shown in Fig. 4 shown, at time TB from rising to falling.

[0055] As described above, the voltage Vpb at point P4 (see Fig. 3) in the voltage output circuit 102, corresponding to the value obtained by shifting the voltage level of voltage Vfc at point P3. The time at which the voltage Vpb exceeds the predetermined threshold Vth is defined as time T1. Time T1 is a time between time TA and time TB. As in Fig. As shown in Figure 4, the transistor Trp switches from the off state to the on state at time T1.

[0056] The time at which the voltage Vpb falls below the specified threshold Vth is then defined as time T2. Time T2 is a time that essentially coincides with or is slightly after time TB. As in Fig. As shown in Figure 4, transistor Trp switches from the on state to the off state at time T2. Therefore, the second voltage V2 output by voltage output circuit 102 (the second voltage V2 at point P5 in voltage output circuit 102, see Figure 4) is... Fig. 3), a pulsating voltage.

[0057] As in Fig. As shown in Figure 4, the second voltage V2 becomes the predetermined voltage VH during the period from time T0 to time T1. Only during the period from time T1 to time T2 does the second voltage V2 become ground potential VL. After time T2, the second voltage V2 reverts to the predetermined voltage VH. This means that the voltage output circuit 102 is a pulse generation circuit containing only one transistor Trp.

[0058] The control / determination device 40 can determine the communication between the input terminal 62 and the output terminal 64 of the solenoid valve 10 based on the second voltage V2. The main control device 30 can easily detect the communication status between the terminals based on the determination result of the control / determination device 40. If the second voltage V2 changes from the preset voltage VH to ground potential VL at time T1, the control / determination device 40 determines that the input terminal 62 and the output terminal 64 have fully communicated with each other.

[0059] The drive / control device 40 can determine that input port 62 and output port 64 have fully communicated with each other when the second voltage V2 changes from ground potential VL to the predetermined voltage VH at time T2. The control / control device 40 can determine that input port 62 and output port 64 have fully communicated with each other when the second voltage V2 changes and becomes a pulsating voltage at times T1 and T2.

[0060] The pulse width of the voltage pulse obtained by changing the second voltage V2 at times T1 and T2 is determined according to the capacitance of the coupling capacitor Ci, the resistance values ​​of the pull-up resistor Rfb1 and the pull-down resistor Rfb2 in the current feedback bias circuit 100, and the capacitance of the coupling capacitor Co and the resistance values ​​of the pull-up resistor Rpb1 and the pull-down resistor Rpb2 in the voltage output circuit 102. Therefore, the capacitance of each coupling capacitor and the resistance value of each resistor are determined according to the required pulse width specification.

[0061] Fig. 5A and Fig. 5B are diagrams illustrating changes in voltage with temperature. Fig. 5A shows the changes in the first voltage V1 and the second voltage V2 over time at a temperature E1. Fig. Figure 5B shows the changes in the first voltage V1 and the second voltage V2 over time at a temperature E2. The temperature E2 is higher than the temperature E1. It should be noted that although the scale of the vertical axis is different between the first voltage V1 and the second voltage V2, both are Fig. 5A as well as in Fig. 5B uses a common vertical axis for better understanding of the description.

[0062] As in Fig. As shown in Figure 5A, the first voltage V1 at temperature E1 at time TA, when the movable iron core 54 begins to move within the solenoid coil 58, is Vm1. After time TB, when the movable iron core 54 reaches the end of its moving section, the first voltage V1 increases again. At time TC, when the increase of the first voltage V1 ends, the first voltage V1 is Vn1. Time T1, when the second voltage V2 changes from the predetermined voltage VH to ground potential VL, lies between time TA and time TB. Time T2, when the second voltage V2 changes from ground potential VL to the predetermined voltage VH, is a time that is essentially the same as or slightly after time TB.

[0063] As the temperature rises, the resistance of the solenoid 58 increases, and therefore the current flowing through the solenoid 58 decreases. Accordingly, the first voltage V1 decreases with increasing temperature. As in Fig. As shown in Figure 5B, in the case of temperature E2, which is higher than temperature E1, the first voltage V1 at time TA is Vm2. The value Vm2 of the first voltage V1 at time TA in the case of temperature E2 is lower than the value Vm1 of the first voltage V1 at time TA in the case of temperature E1.

[0064] As in Fig. As shown in Figure 5B, in the case of temperature E2, the first voltage V1 at time TC is equal to Vn2. The value Vn2 of the first voltage V1 at time TC in the case of temperature E2 is lower than the value Vn1 of the first voltage V1 at time TC in the case of temperature E1. However, the control circuit 20 outputs the second voltage V2 by using the voltage Vfc, which is obtained by amplifying the voltage Vfb, the AC component of the first voltage V1, instead of the first voltage V1 itself.

[0065] The current feedback bias circuit 100, which amplifies the voltage Vfb to the voltage Vfc, is less susceptible to temperature changes. Therefore, as shown in Fig.As shown in Figure 5B, even in the case of temperature E2, time T1 is a time between time TA and time TB, and time T2 is a time that is essentially equal to or slightly after time TB, as in the case of temperature E1. That is, the control circuit 20 outputs the pulsating second voltage V2 stably even when a temperature change occurs. Therefore, the actuator / determiner 40 can stably determine the communication between the input terminal 62 and the output terminal 64 of the solenoid valve 10.

[0066] The following supplementary remarks are further revealed in relation to the above revelation. (Supplementary Note 1)

[0067] The control circuit (20) for the solenoid valve (10) with the solenoid coil (58) comprises: the current feedback bias circuit (100), which includes the transistor (Trf) with base, emitter and collector, wherein the base is connected to the pull-up resistor (Rfb1) and the pull-down resistor (Rfb2), which are configured to share the supply voltage (Vref) supplied by the current source (80), wherein the emitter is connected to the emitter resistor (Rfe) connected to ground, and the collector is connected to the load resistor (Rfc) connected to the current source, wherein the current feedback bias circuit is configured to amplify the AC component of the first voltage (V1), which corresponds to the current flowing through the solenoid coil, with the AC component being applied to the base;and the voltage output circuit (102) is configured to output the second voltage (V2), which changes according to the AC component amplified by the current feedback bias circuit, to the determining device (40), the determining device being configured to determine the communication between the input terminal (62) and the output terminal (64) of the solenoid valve based on the second voltage. According to such a configuration, the scope of the control circuit for the solenoid valve can be reduced. (Supplementary Note 2)

[0068] The control circuit for the solenoid valve according to Supplementary Note 1 may further include the coupling capacitor (Co) configured to shift the voltage level of the AC component amplified by the current feedback bias circuit, whereby the voltage output circuit can output the second voltage, which changes according to the AC component whose voltage level was shifted by the coupling capacitor. According to such a configuration, the circuit constants for the voltage output circuit can be determined independently of the current feedback bias circuit. (Supplementary Note 3)

[0069] In the control circuit for the solenoid valve according to supplementary note 1 or 2, the voltage output circuit can include the transistor (Trp) configured to provide an open-collector output, and the second voltage can decrease when the AC component exceeds the predetermined threshold (Vth). With such a configuration, threshold control can be implemented to change the second voltage using the predetermined threshold. (Supplementary Note 4)

[0070] In the control circuit for the solenoid valve according to Supplementary Note 3, the base of the transistor in the voltage output circuit can be connected to the pull-up resistor (Rpb1) and the pull-down resistor (Rpb2), which are configured to divide the supply voltage provided by the power source. The predetermined threshold can be determined according to the resistance values ​​of the pull-up and pull-down resistors to which the base of the transistor in the voltage output circuit is connected and the supply voltage provided by the power source. According to such a configuration, the voltage corresponding to the operating point of the transistor in the voltage output circuit can act as the predetermined threshold. (Supplementary Note 5)

[0071] In the control circuit for the solenoid valve, according to supplementary note 3 or 4, the emitter of the transistor in the voltage output circuit can be connected to ground, the collector of the transistor in the voltage output circuit can be connected to the load resistor (Rpc) connected to the power source, and if the AC component exceeds the predetermined threshold, the collector of the transistor in the voltage output circuit can output the ground potential (VL) as a second voltage. With this configuration, the communication status of the solenoid valve can be easily determined. (Supplementary Note 6)

[0072] In the control circuit for the solenoid valve according to one of the supplementary notes 1 to 5, the base of the transistor included in the current feedback bias circuit can be connected to the coupling capacitor (Ci), which is configured to remove the DC component of the first voltage. According to such a configuration, the control circuit can be implemented cost-effectively.

[0073] The present invention is not limited to the above disclosure, and various modifications are possible without deviating from the essence and core of the present invention. LIST OF REFERENCE TERMS 10 solenoid valve 20 Control circuit 30 Main control device 40 Drive / determination device (determination device) 50 cases 52 solid iron core 54 movable iron core 56 spring 58 Magnetic coil 60 Valve seat 62 Input connection 64 Output port 80 Power source 100 Current feedback bias circuit 102 Voltage output circuit

Claims

[1] Control circuit (20) for a solenoid valve (10) with a solenoid coil (58), wherein the control circuit comprises: a current feedback bias circuit (100) comprising a transistor (Trf) having a base, an emitter, and a collector, wherein the base is connected to a pull-up resistor (Rfb1) and a pull-down resistor (Rfb2) configured to share a supply voltage (Vref) provided by a current source (80), wherein the emitter is connected to an emitter resistor (Rfe) connected to ground, and wherein the collector is connected to a load resistor (Rfc) connected to the current source, the current feedback bias circuit being configured to amplify an AC component of a first voltage (V1) corresponding to a current flowing through the magnet coil, the AC component being applied to the base; and a voltage output circuit (102) configured to output a second voltage (V2) to a determining device (40), which changes according to the AC component amplified by the current feedback bias circuit, wherein the determining device is configured to determine the communication between an input terminal (62) and an output terminal (64) of the solenoid valve on the basis of the second voltage. [2] The control circuit for the solenoid valve according to claim 1, further comprising a coupling capacitor (Co) configured to shift a voltage level of the AC component amplified by the current feedback bias circuit, wherein the voltage output circuit outputs the second voltage which changes according to the AC component whose voltage level has been shifted by the coupling capacitor. [3] The control circuit for the solenoid valve according to claim 1, wherein the voltage output circuit comprises a transistor (Trp) configured to provide an open-collector output and the second voltage decreases in a case where the AC component exceeds a predetermined threshold (Vth). [4] The control circuit for the solenoid valve according to claim 3, wherein a base of the transistor included in the voltage output circuit is connected to a pull-up resistor (Rpb1) and a pull-down resistor (Rpb2) configured to share the supply voltage provided by the power source, and the predetermined threshold is determined according to the resistance values ​​of the pull-up resistor and the pull-down resistor to which the base of the transistor included in the voltage output circuit is connected, and the supply voltage supplied by the current source. [5] Control circuit for the solenoid valve according to claim 3, wherein an emitter of the transistor contained in the voltage output circuit is connected to ground, a collector of the transistor contained in the voltage output circuit is connected to a load resistor (Rpc) connected to the current source, and In the event that the alternating current component exceeds the predetermined threshold, the collector of the transistor contained in the voltage output circuit outputs a ground potential (VL) as a second voltage. [6] Control circuit for the solenoid valve according to any one of claims 1 to 5, wherein the base of the transistor included in the current feedback bias circuit is connected to a coupling capacitor (Ci) configured to remove a DC component of the first voltage.

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