SOLENOID DEVICE

Abstract

 The invention relates to a solenoid device, in particular for a solenoid valve, with a solenoid coil (S) having a housing (10) and with a driving unit (12) for the solenoid coil (S), wherein the driving unit (12) is arranged within the housing (10) of the solenoid coil (S).

Description

[0001] The invention relates to a solenoid device, in particular for a solenoid valve.

[0002] Solenoid devices are used in a multitude of technical applications, for example to provide electromechanical control for valves in fluidic systems. A solenoid coil in such a valve generates a magnetic field which actuates a valve piston, diaphragm or the like, in order to switch the valve between an open and closed state.

[0003] In order to control the solenoid, a driving unit is necessary which provides the needed voltage and current to put the solenoid in a predefined state. Such driving units are usually placed external to the solenoid itself, which is usually housed in a separate housing. Generally, the driving unit is provided on a printed circuit board (PCB).

[0004] An example for a solenoid device according to the prior art is shown in Fig. 1. A solenoid S is arranged in a housing 10. Terminal contacts A, B of the solenoid S are connected to an external driving unit 12 in form of a PCB. The driving unit 12 comprises connectors 14 for a power supply and connectors 16 for a communication connection with further external controller components.

[0005] In more complex application containing multiple solenoids, any change in the solenoid layout during the design phase necessitates a redesign of the PCB of the driving unit 12 to accommodate changed, added or removed solenoids S. Moreover, such a PCB takes up considerable room, which can be problematic in many applications with restricted installation space, as it is the case for example in automotive applications.

[0006] It is thus the technical problem underlying the present invention to provide a solenoid device which is easily adaptable and particularly compact.

[0007] This problem is solved by the subject matter of claim 1.

[0008] According to the invention, a solenoid device, in particular for a solenoid valve, comprises a solenoid coil having a housing and a driving unit for the solenoid coil, wherein the driving unit is arranged within the housing of the solenoid coil.

[0009] By integrating the driving unit into the solenoid housing, the need for external circuits is reduced, allowing for a compact configuration. Moreover, since each solenoid device carries its own driving unit, the external circuitry, if present at all, does not have to be redesigned if any changes regarding the solenoid layout of a particular apparatus are made during the design phase or during later overhauls.

[0010] In a preferred embodiment of the invention, the driving unit comprises a high side switch driver circuit and a first transistor, in particular a MOSFET (metal-oxide-semiconductor field effect transistor), wherein the first transistor is adapted to apply a first potential to the solenoid when activated by the high side switch driver circuit.

[0011] High side switch is to be understood in that the first transistor is arranged between high potential, i.e. the power supply, and the solenoid. High side drivers are robust against faults to ground, which are the most common fault type in automotive applications.

[0012] In a further preferred embodiment, the driving unit comprises a free wheeling diode driver circuit and a second transistor, in particular a MOSFET, wherein the second transistor is adapted to apply a second potential to the solenoid when activated by the free wheeling diode driver circuit.

[0013] In other words, the second transistor acts like a protective diode eliminating fly back voltage spikes as caused by loss or disruption of the power supply for the inductive load of the solenoid. To this end, the second transistor is preferably arranged in parallel to the solenoid. Furthermore, the second transistor can be applied to maintain current flow through the solenoid.

[0014] In a further preferred embodiment of the invention, the driving unit comprises a low side switch driver circuit and a third transistor, in particular a MOSFET, wherein the third transistor is adapted to apply a third potential to the solenoid when activated by the low side switch driver circuit.

[0015] A low side switch driver comprises the switching transistor being arranged between the solenoid and ground. Low side drivers are generally easier to control but lack protection from faults to ground compared to high side drivers.

[0016] It is further preferred for the first, second and third transistor to be connected in series. In such an embodiment, the driving offers the option to select between the high side and low side driver to control the solenoid, while the second transistor provides power surge protection when switching the solenoid in both of these cases.

[0017] In a further embodiment, the first and/or second and/or third potential is a pulse-width modulated signal. Pulse-width modulation (PWM) is based on providing a rectangular signal switching between a HIGH potential state and a LOW potential state with varying pulse lengths. It allows for setting the magnetic field strength of the solenoid in an analog manner while providing a digital control signal. Due to the low-pass filtering characteristics of the solenoid, the resulting average magnetic field strength depends on the duty cycle of the PWM signal applied to the solenoid, i.e. the ratio between the times the PWM signal is in the HIGH state and the LOW state.

[0018] In a further preferred embodiment, the solenoid is connected in series to a measuring shunt and the driving unit comprises a measurement circuit to measure a potential drop over the measuring shunt. This allows for monitoring of the load applied to the solenoid.

[0019] It is further preferred if the solenoid and the measuring shunt are connected in parallel with the second transistor, in order to provide protection against fly back voltage spikes.

[0020] In another preferred embodiment, the driving unit comprises an interface for receiving command instructions for the solenoid device and/or sending status information about the solenoid device, in particular via a field bus, preferably a CAN-bus or FlexRay-bus. This allows for connecting the solenoid device to other controller devices, in particular for automotive applications, in a standardized way.

[0021] It is further preferred that driving unit in the solenoid's housing comprises a communication circuit providing the interface, said interface being in particular in form of a CAN-bus or FlexRay-bus socket. The communications circuit can translate external control commands to internal commands for the drivers and relate internal status information of the driving unit to external devices.

[0022] In a further preferred embodiment, the driving unit is constructed as an integrated circuit. This allows for a particularly compact form of the driving unit, and thus of the overall solenoid device.

[0023] Embodiments of the invention are now described in further detail with reference to the drawings, wherein:

Fig. 1

shows a solenoid device according to the prior art;

Fig. 2

shows a schematic depiction of a solenoid device according to an embodiment of the invention; and

Fig. 3

shows a schematic circuit diagram of a solenoid device according to an embodiment of the invention.

[0024] The solenoid device shown in Fig. 2 comprises a solenoid S, which is arranged in a housing 10. A driving unit 12 is connected to terminal connectors A, B of the solenoid S and arranged in the housing 10 together with the solenoid S. The driving unit 12 is connected to an external printed circuit board, PCB, 18, which provides connectors 14 for a power supply and connectors 16 for control signals. Since the driving unit 12 is integrated with the solenoid housing 10, the external circuit board 18 can be smaller than in case of the prior art shown in Fig. 1 and can be independent from the type of solenoid S.

[0025] As shown in Fig. 3, the driving unit 12 comprises a high side switch driver 20 connected to a MOSFET T1. When the high side switch driver 20 activates the MOSFET T1, the terminal connector A of the solenoid S is connected to the high potential level of the power supply (usually between 10 V and 15 V), while the terminal connector B is connected to ground via a measuring shunt R_S.

[0026] A further MOSFET T2 can be activated via a free wheeling diode driver 22. The MOSFET T2 is connected in parallel to the solenoid S and the measuring shunt R_S and acts as a flyback diode preventing flyback voltage spikes upon deactivation of the solenoid S. It can further be utilized to maintain current flow through the solenoid S.

[0027] A low side switch driver 24 controls a third MOSFET T3. When activated, the MOSFET T3 connects the terminal connector B of the solenoid to ground via the measuring shunt R_S, while the terminal connector A of the solenoid is connected to the high potential level of the power supply.

[0028] This arrangement allows driving the solenoid S either in high side mode or in low side mode. Which mode is chosen depends on the particular application of the solenoid S. A connector pin 19 of the driving unit 20 can receive an external signal to control the driving mode or can be hardwired to either ground or high potential to set a fixed driving mode for the solenoid S.

[0029] When in high side mode, the first MOSFET T1 provides control for the solenoid S. The MOSFET T3 is not used for control purposes in this arrangement, but rather provides a protective function by disconnecting the solenoid from ground in case of a malfunction, like an overcurrent, a short circuit on the solenoid or a defect of the low side switch driver 24.

[0030] The drivers 20, 22, 24 provide pulse-width modulated (PWM) signals to the respective gates of MOSFETS T1, T2, T3 in order to activate or deactivate them. Since the MOSFETS are activated and deactivated in synchronization with the PWM signal, the resulting potential to the solenoid S also follows the PWM signal. Due to the inductivity of the solenoid S, the signal is smoothed, so that the resulting magnetic field is largely constant. The resulting field strength can be modulated by changing the duty cycle of the PWM signal.

[0031] A current measurement block 26 can monitor the voltage drop over the measuring shunt R_S in order to determine the load applied to the solenoid S.

[0032] Control signals for the drivers 20, 22, 24 can be received via a communication circuit 28, which also can relay back internal information of the driving unit 12 to external devices. The communication circuit 28 is coupled to the connectors 16, which preferably provide a CAN- or FlexRay-bus interface for automotive applications.

Claims

1. Solenoid device, in particular for a solenoid valve, with a solenoid coil (S) having a housing (10) and with a driving unit (12) for the solenoid coil (S), wherein the driving unit (12) is arranged within the housing (10) of the solenoid coil (S).

2. Solenoid device according to claim 1,
characterized in that
the driving unit (12) comprises a high side switch driver circuit (20) and a first transistor (T1), in particular a MOSFET, wherein the first transistor (T1) is adapted to apply a first potential to the solenoid (S) when activated by the high side switch driver circuit (20).

3. Solenoid device according to claim 1 or 2,
characterized in that
the driving unit (12) comprises a free wheeling diode driver circuit (22) and a second transistor (T2), in particular a MOSFET, wherein the second transistor (T2) is adapted to apply a second potential to the solenoid (S) when activated by the free wheeling diode driver circuit (22).

4. Solenoid device according to any of claims 1 to 3,
characterized in that
the driving unit (12) comprises a low side switch driver circuit (24) and a third transistor (T3), in particular a MOSFET, wherein the third transistor (T3) is adapted to apply a third potential to the solenoid (S) when activated by the low side switch driver circuit (24).

5. Solenoid device according to claims 2 to 4,
characterized in that
the first (T1), second (T2) and third transistor (T3) are connected in series.

6. Solenoid device according to any of claims 2 to 5,
characterized in that
the first and/or second and/or third potential is a pulse-width modulated signal.

7. Solenoid device according to any of claims 1 to 6,
characterized in that
the solenoid (S) is connected in series to a measuring shunt (R_S) and the driving unit (12) comprises a measurement circuit (26) to measure a potential drop over the measuring shunt (R_S).

8. Solenoid device according to claim 7,
characterized in that
the solenoid (S) and the measuring shunt (R_S) are connected in parallel with the second transistor (T2).

9. Solenoid device according to any of claims 1 to 8,
characterized in that
the driving unit (12) comprises an interface (16) for receiving command instructions for the solenoid device and/or sending status information about the solenoid device, in particular via a field bus, preferably a CAN-bus or FlexRay-bus.

10. Solenoid device according to claim 9,
characterized in that
the driving unit (12) comprises a communication circuit (28) providing the interface, said interface being in particular in form of a CAN-bus or FlexRay-bus socket.

11. Solenoid device according to any of claims 1 to 10,
characterized in that
the driving unit (12) is constructed as an integrated circuit.

Drawing