Solenoid-valve control circuit

Abstract

A circuit (1) for controlling a solenoid valve (200) comprising an inductor coil (2) configured to be connected to / disconnected from a voltage source (+U) in order to be able to move a plunger of the solenoid valve (200) between a closed position and an open position, the inductor coil (2) being subjected to discharging upon disconnection from the voltage source; a first freewheel component (5) configured to, in a holding phase, allow slow discharging of the inductor coil (2); a second freewheel component (6) configured to, in a phase of closure, allow rapid discharging of the inductor coil (2), the first and second freewheel components (5) being mounted in series; a switch (7) configured to allow the second freewheel component (6) to be bypassed in the holding phase.

Description

Control circuit of a solenoid valve

[0001] The present invention relates to a control circuit for a solenoid valve, and a method for controlling a solenoid valve.

[0002] Patent application WO22245269 discloses a method for controlling the discharge of a solenoid valve of a vehicle, in particular the discharge of a coil injector for use as an injector in a vehicle. In this patent application, it is recommended to discharge the inductor at a slow discharge rate during an operating period during which a final part of a movement of the piston from the held position to the rest position takes place, and to discharge the inductor at a fast discharge rate during another period, the piston being stationary during a part of this other period, the fast discharge rate being faster than the slow discharge rate.

[0003] Generally speaking, when the power supply is connected to an inductor, the voltage across the inductor increases to match that of the power source. The rate at which the current can change in an inductor is limited by its time constant (which is a characteristic of the coil). Upon disconnection, the inductive load in the coil can generate a very large negative voltage that can damage the switching circuit. For this reason, it is necessary to implement a freewheeling system that protects the electrical circuit. For example, a freewheeling diode provides a conduction path for the excess energy from the inductor, thus protecting the rest of the circuit.

[0004] The invention aims to improve the control of the solenoid valve.

[0005] The invention thus relates to a control circuit for a solenoid valve (or electromagnetic valve), in particular to be mounted on a motor vehicle, comprising: an inductance coil configured to be connected / disconnected from a voltage source in order to be able to move a plunger (or piston) of the solenoid valve between a closed position and an open position, and the inductance coil being subjected to a discharge during a disconnection from the voltage source; a first freewheel component configured to, in a plunger holding phase, allow a slow discharge of the inductance coil; a second freewheel component configured to, in a plunger closing phase, allow a rapid discharge of the inductance coil, the first freewheel component and the second freewheel component being connected in series; a switch configured to allow short-circuiting of the second freewheel component in the holding phase.

[0006] The invention thus recommends selectively switching between freewheel components, one suitable for slow discharge and the other suitable for fast discharge. Thus, instead of seeking a balanced discharge value with a single freewheel component, the invention makes it possible to improve the performance of the solenoid valve (or electromagnetic valve) by reducing vibrations and reducing the closing time.

[0007] In summary, the invention makes it possible to minimize vibrations during the holding phase and to increase the responsiveness of the system when closing the plunger.

[0008] In the plunger hold phase, the plunger is held in the open position. In the plunger close phase, the plunger moves from the open position to the closed position.

[0009] The plunger allows, in the open position, to let a fluid pass and, in the closed position, to block the fluid path.

[0010] The inductor coil is configured to control the movement of the plunger when the inductor coil is charged or discharged.

[0011] In the present invention, the difference between slow discharge and fast discharge is that to discharge the same amount of energy from the inductance coil, slow discharge requires a longer time than fast discharge.

[0012] A pulse width modulation control is designated MLI in French, or PWM in English for “Pulse Width Modulation”.

[0013] According to one aspect of the invention, the control circuit is configured to generate PWM signals of frequency with a variable duty cycle in order to vary the voltage applied to the inductor coil, thereby controlling the solenoid valve. In this case, the inductive load is switched several times per PWM cycle.

[0014] According to one aspect of the invention, the switch is configured such that, in a closed state, the second freewheel component is short-circuited, and in the open state, the first freewheel component is in series with the second freewheel component on a single line.

[0015] In the closed state, the switch defines a bypass to short-circuit the second freewheel component. The switch is, for example, connected in parallel with this second freewheel component.

[0016] According to one aspect of the invention, the first freewheeling component is a simple freewheeling diode.

[0017] This simple diode allows a slow discharge of the coil current.

[0018] Thus, during the holding phase, it is possible to have a slow discharge of the current in the coil. This allows a reduction of vibration at the solenoid valve.

[0019] According to one aspect of the invention, the second freewheeling component is a Zener diode configured to allow rapid discharge of the inductor coil.

[0020] The Zener diode allows for faster and more controlled discharge of the inductor coil current.

[0021] As a reminder, a simple diode is configured to allow current to flow only in the forward direction, while the Zener diode is configured to also allow a reverse current. This is well known in the state of the art.

[0022] According to one aspect of the invention, in the holding phase, the switch is in the closed state so that the second freewheel component is short-circuited.

[0023] In the closing phase, the aim is to have a rapid discharge of current in the coil, in order to obtain a rapid closing of the solenoid valve. In this case, the switch goes to the closed state so that the circuit "sees" both the simple diode and the Zener diode.

[0024] According to one aspect of the invention, the control circuit is configured to switch the second freewheeling component, in particular the Zener diode, preferably in a synchronized manner with the control of the solenoid valve, in particular the voltage control of the solenoid valve. The switching frequency is for example 2 ms.

[0025] This solution minimizes vibrations during the holding phase and increases the system's responsiveness when closing.

[0026] According to one aspect of the invention, the solenoid valve is of the normally closed type.

[0027] The invention also relates to a system comprising a solenoid valve and a solenoid valve control circuit as described above.

[0028] According to one aspect of the invention, the solenoid valve is configured to be integrated into a fluid loop to control the flow of a fluid, for example a liquid, within the loop.

[0029] For example, the solenoid valve may be used to control a system for cleaning the external sensors of a motor vehicle. In such a system, a pump supplies one or more spray nozzles each associated with a sensor, the spraying being controlled by at least one solenoid valve. The liquid could be any liquid or mixture of liquids suitable for use in cleaning, such as water, alcohol (methanol, ethanol, etc.) and / or a mixture of a liquid and a cleaning additive such as a detergent.

[0030] The invention also relates to a method for controlling a solenoid valve, in particular on board a motor vehicle, using a first freewheel component and a second freewheel component, the solenoid valve being provided with an inductance coil configured to be connected / disconnected from a voltage source in order to be able to move a plunger of the solenoid valve between a closed position and an open position, and the inductance coil being subjected to a discharge upon disconnection from the voltage source, the method comprising the following steps: using the first freewheel component and without the second freewheel component which is short-circuited, triggering a slow discharge of the inductance coil in a plunger holding phase; using the second freewheel component connected in series with the first freewheel component, triggering a fast discharge of the inductance coil in a plunger closing phase.

[0031] Other characteristics, details and advantages of the invention will emerge more clearly on reading the description which follows on the one hand, and several examples of embodiment given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0032] This is a schematic representation of a solenoid valve system according to an exemplary embodiment of the invention, in a holding phase;

[0033] This is a schematic representation of the solenoid valve system of the, in a closing phase;

[0034] Illustrates, for the holding phase, the current ripples for the case where Zener diode 6 is short-circuited (curve C1) and the case where the Zener diode is not short-circuited (curve C2);

[0035] Illustrates discharge curves, in the closing phase;

[0036] Shows curve C5 of the voltage control of the solenoid valve and curve C6 shows the switching control on the switch to control the Zener diode.

[0037] The features, variants and different embodiments of the invention may be combined with each other in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0038] Figures 1 and 2 show a system 100 comprising a solenoid valve 200 (shown in dotted lines on the) and a control circuit 1 for the solenoid valve 200 according to one exemplary embodiment of the invention.

[0039] The solenoid valve 200 comprises a plunger 201 (or piston) movable between a closed position and an open position. The plunger 201, in the open position, allows a fluid to pass through and, in the closed position, blocks the fluid path.

[0040] The solenoid valve 200 is configured to be integrated into a fluid loop to control the flow of a fluid, for example a liquid, within the loop.

[0041] The control circuit 1 comprises an inductance coil 2 (solenoid type) configured to be connected / disconnected from a voltage source +U to be able to move the plunger 201 of the solenoid valve 200 between the closed position and the open position.

[0042] The inductance coil 2 is subjected to a discharge when disconnected from the voltage source +U.

[0043] The control circuit 1 further comprises a first freewheel component 5 configured to, in a plunger holding phase, allow a slow discharge of the inductance coil 2, and a second freewheel component 6 configured to, in a plunger closing phase, allow a rapid discharge of the inductance coil 2.

[0044] The first freewheel component 5 and the second freewheel component 6 are connected in series.

[0045] In the holding phase of the plunger 201, the plunger 201 is held in the open position. In the closing phase of the plunger, the plunger 201 moves from the open position to the closed position.

[0046] The inductor coil 1 is configured to control the movement of the plunger 201 when the inductor coil 2 is charged or discharged.

[0047] In the present invention, the difference between slow discharge and fast discharge is that to discharge the same amount of energy from the inductance coil, slow discharge requires a longer time than fast discharge.

[0048] It should be noted that the exact definition of "slow" and "fast" are a consequence of the electrical parameters of the system. In particular, the slow discharge will be at least partly a function of the inductance of the solenoid coil, and the fast discharge will be at least partly a function of the value of the Zener voltage (V z ) of the Zener diode.

[0049] In the example described, the first freewheeling component 5 is a simple freewheeling diode. This simple diode allows a slow discharge of the coil current.

[0050] The second freewheeling component 6 is a Zener diode configured to allow rapid discharge of the inductor coil 2.

[0051] The control circuit 1 further comprises a switch 7 configured to allow short-circuiting of the second freewheel component 6 in the holding phase.

[0052] A power transistor 8 (e.g. NPN type) is provided in the control circuit 1 to activate or deactivate the power supply to the solenoid 2, in a manner known per se.

[0053] The control circuit 1 is configured to generate PWM signals with a variable duty cycle in order to vary, via the transistor 8, the voltage applied to the inductance coil 2, thereby controlling the solenoid valve 200. In this case, the inductive load is switched several times per PWM cycle.

[0054] The switch 7 is configured so that, in a closed state, the second freewheel component 6 is short-circuited (see), and in the open state of the switch 7, the first freewheel component 5 is in series with the second freewheel component 6 on a single line 9 (see).

[0055] In the closed state, the switch 7 defines a bypass for short-circuiting the second freewheel component 6. The switch 7 is, for example, connected in parallel with this second freewheel component 6.

[0056] Zener diode 6 allows for faster and controlled discharge of current from inductor coil 2.

[0057] As a reminder, a simple diode is configured to allow current to flow only in the forward direction, while the Zener diode is configured to also allow a reverse current. This is well known in the state of the art.

[0058] Illustrates, for the holding phase, the current ripples for the case where Zener diode 6 is short-circuited (curve C1) and the case where the Zener diode is not short-circuited (curve C2).

[0059] The ripple rate in curve C1 (Zener diode 6 is short-circuited) is less than curve C2 (Zener diode is not short-circuited).

[0060] We thus see the advantage of short-circuiting the Zener diode 6, in that it allows, in the holding phase, to reduce the vibrations at the level of the solenoid valve 200.

[0061] It is thus recalled that in the holding phase, the switch 7 is in the closed state so that the second freewheel component 6 is short-circuited.

[0062] In the closing phase, it is desired to have a rapid discharge of the current in coil 2, in order to obtain a rapid closing of the solenoid valve. In this case, switch 7 goes to the closed state so that the circuit "sees" both the simple diode 5 and the Zener diode 6 to obtain a faster discharge (see curve C3 of the) than the case where the Zener diode 6 would be short-circuited (see curve C4 of the).

[0063] The curves in Figures 3 and 4 are schematic to illustrate the advantages of the invention.

[0064] In the example described, the control circuit 1 is configured to switch the second freewheeling component, here the Zener diode 6, in a synchronized manner with the voltage control of the solenoid valve 200. This aspect is illustrated in the where curve C5 shows the voltage control of the solenoid valve 20 and curve C6 shows the switching control on the switch 7 to control the Zener diode 6. The synchronization is seen, here with a switching frequency of, for example, 2 ms.

[0065] The invention makes it possible to minimize vibrations during the holding phase and to increase the responsiveness of the system when closing.

[0066] The method for controlling the solenoid valve 200 is thus carried out using the first freewheel component 5 and the second freewheel component 6, the method comprising the following steps: using the first freewheel component 5 and without the second freewheel component which is short-circuited, triggering a slow discharge of the inductance coil in a holding phase of the plunger 201; using the second freewheel component 6 connected in series with the first freewheel component 5, triggering a rapid discharge of the inductance coil in a closing phase of the plunger 201.

[0067] The above two steps follow one another sequentially.

Claims

Control circuit (1) of a solenoid valve (200), in particular to be mounted on a motor vehicle, comprising: an inductance coil (2) configured to be connected / disconnected from a voltage source (+U) to be able to move a plunger of the solenoid valve (200) between a closed position and an open position, and the inductance coil (2) being subjected to a discharge during a disconnection from the voltage source; a first freewheel component (5) configured to, in a plunger holding phase, allow a slow discharge of the inductance coil (2); a second freewheel component (6) configured to, in a plunger closing phase, allow a rapid discharge of the inductance coil (2), the first freewheel component (5) and the second freewheel component (6) being mounted in series; a switch (7) configured to allow a short-circuiting of the second freewheel component (6) in the holding phase. Control circuit (1) according to the preceding claim, wherein the control circuit (1) is configured to generate PWM signals with a variable duty cycle in order to vary the voltage applied to the inductance coil (2). Control circuit (1) according to one of the preceding claims, wherein the switch (7) is configured so that, in a closed state, the second freewheel component (6) is short-circuited, and in the open state, the first freewheel component (5) is in series with the second freewheel component (6) on a single line. Control circuit (1) according to one of the preceding claims, wherein the first freewheeling component (5) is a simple freewheeling diode. Control circuit (1) according to one of the preceding claims, wherein the second freewheeling component (6) is a Zener diode configured to allow rapid discharge of the inductance coil (2). Control circuit (1) according to one of the preceding claims, wherein the control circuit (1) is configured to switch the second freewheeling component (6), in particular the Zener diode, preferably in a synchronized manner with the control of the solenoid valve (200), in particular the voltage control of the solenoid valve (200). Control circuit (1) according to one of the preceding claims, in which the solenoid valve (200) is of the normally closed type. System comprising a solenoid valve (200) and a control circuit (1) of the solenoid valve (200) according to one of the preceding claims. System according to the preceding claim, wherein the solenoid valve (200) is configured to be integrated into a fluid loop to control the flow of a fluid, for example a liquid, within the loop. Method for controlling a solenoid valve (200), in particular on board a motor vehicle, using a first freewheel component (5) and a second freewheel component (6), the solenoid valve (200) being provided with an inductance coil (2) configured to be connected / disconnected from a voltage source in order to be able to move a plunger of the solenoid valve (200) between a closed position and an open position, and the inductance coil (2) being subjected to a discharge upon disconnection from the voltage source, the method comprising the following steps: using the first freewheel component (5) and without the second freewheel component (6) which is short-circuited, triggering a slow discharge of the inductance coil (2) in a plunger holding phase;using the second freewheel component (6) connected in series with the first freewheel component (5), triggering a rapid discharge of the inductance coil (2) in a closing phase of the plunger.;

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