Brushless DC Motor Control With Integrated Water in Filter Circuitry

Abstract

A filter assembly combines the physical support, protection and electrical connections for a water in filter (WIF) circuit with the support, enclosure and electrical connections used for a motor control circuit that drives a BLDC motor in the filter assembly. Sharing space and electrical connections between what have been physically separate electronic circuits reduces the cost, materials and parts necessary to manufacture the filter assembly. In an assembly with a brushless motor-driven pump, the electrical connections from the host equipment to the motor can be shared with the WIF circuit, eliminating separate conductors and connectors.

Description

BACKGROUND

The disclosure relates to fuel filter systems, and particularly to fuel filter systems incorporating a brushless motor-driven pump and components for detecting accumulated water in the filter housing.

Fuel filtration systems are constructed to remove particulates and water from fuel delivered to systems such as internal combustion engines. Separated water accumulates in fuel filter assembly housings and must be periodically removed. A common method of detecting the amount of water is to employ electrodes positioned to sense the electrical resistance of fluid within the filter housing. The electrical resistance of water is far less than the electrical resistance of hydrocarbon fuels such as diesel fuel, so water contacting the electrodes produces a detectable change in current flow between the electrodes. This change in electrical resistance is used to generate a signal communicated to service personnel, automatic water drain systems, and/or the vehicle operator that accumulated water has reached a level that must be drained. The filter assembly incorporates a water in filter (WIF) circuit that receives power, electrically connects the sensor in a path where the changes in electrical resistance at the sensor can be detected at the WIF circuit, and provides an electrical signal compatible with vehicle systems that provide indicators for service or operators, or for use by automatic water drain apparatus.

Fuel filter assemblies frequently incorporate a motor driven pump to move fuel through the filter enclosure and filter media, providing a pre-determined flow of clean fuel at a defined pressure to downstream systems such as high pressure fuel injection pumps and fuel injection systems. The motor driving the pump may be of the brushed or brushless type, with either form of motor requiring at least one electrical connector to power the motor. Brushless direct current (BLDC) motors require a motor control circuit that is typically arranged within the motor/pump housing or on the filter assembly close to the BLDC motor. It is common for prior art filter assemblies to have two electrical connections to the equipment to which the filter assembly is connected, a first electrical connector for the WIF circuit and a separate electrical connector to the motor that drives the pump.

There is a need in the art for a filter assembly that reduces the part count and simplifies the electrical interface between the filter assembly and host equipment.

SUMMARY OF THE INVENTION

A filter assembly according to aspects of the disclosure combines the physical support, protection and electrical connections for a WIF circuit with the support, protection and electrical connections used for a motor control circuit that drives a BLDC motor in the filter assembly. Sharing space, electrical connections between what have been physically separate electronic circuits reduces the cost, materials and parts necessary to manufacture the filter assembly. In an assembly with a brushless motor-driven pump, the electrical connections from the host equipment to the motor can be shared with the WIF circuit, eliminating separate conductors and connectors.

In one embodiment, the WIF circuit shares electrical connections for a lift pump in a fuel filter assembly, resulting in a single electrical connector to the host equipment.

In one embodiment, the WIF circuit is mounted to the same printed circuit board as a motor control circuit for a pump included in the filter assembly.

In one embodiment, the filter assembly includes a pocket sealed from fluid flowing through the filter assembly, a motor control circuit is constructed on a printed circuit board mounted in said pocket and a WIF circuit is constructed on the same printed circuit board as the motor control circuit.

In one embodiment, the WIF and motor control circuit are constructed on the same printed circuit board, but operate independently of each other.

In one embodiment, the WIF and motor control circuit are constructed on the same printed circuit board, and the WIF transmits a water present signal to the motor control circuit.

Alternative embodiments of the disclosed filter assembly may incorporate one or more of the disclosed features and relationships included in the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view through a filter assembly illustrating separate circuit boards, electrical connections and locations for WIF and motor control circuits; and

FIG. 2 is an exterior view of a filter assembly where the WIF circuit and motor control circuit share the same space and electrical connections according to aspects of the disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a filter assembly 10 incorporating a water-in-filter (WIF) circuit 12 and related water sensor 14. The water sensor 14 is situated in a water bowl 16 suspended from the lower end of a filter cartridge 18.

A connector 13 and wires bring power and ground to the WIF circuit 12 and send a “water present” signal from the WIF circuit 12 to other systems, where the water present signal may be used to light an indicator or activate an automated water drain mechanism. The filter assembly includes a filter head 20 that receives the filter cartridge and defines fluid flow paths into and away from the filter cartridge 18. The upper end of the filter head 20 mounts a brushless direct current (BLDC) motor 22 and pump 23 enclosed in a housing 24 mounted to the top of the filter head 20. The housing 24 cooperates with a cover 25 to define a sealed pocket 27 for a control board 28. The control board 28 includes a control circuit 30 that generates the rotating magnetic field to drive the BLDC motor 22 at a rotational speed sufficient to provide fuel flow to meet demand from downstream systems. A connector 32 delivers power and ground to the control board 28 for use by the control circuit 30.

The BLDC motor 22 drives the pump 23 to circulate fuel from a supply reservoir through the filter cartridge 18 and out of the filter assembly 10 to downstream systems such as high pressure fuel pumps or fuel injection systems. As fuel passes through the filter cartridge 18, water is separated from the fuel and falls to the bottom of the filter cartridge 18, where it passes through a drain opening 26 into the water bowl 16. The water sensor is arranged to detect a level of water accumulation in the water bowl 16, and the WIF circuit is constructed to monitor the condition of the water sensor 14 and generate the “water present” signal indicating a need to drain water from the water bowl 16.

The filter assembly shown in FIG. 1 requires two separate PC boards, two enclosures for the boards, two sets of conductors and connectors for the separate WIF circuit 12 and motor control board 28.

FIG. 2 illustrates an alternative filter assembly 100, which is similar in structure and function to the filter assembly 10 described above. A filter head 120 mounts a filter cartridge 118 and defines fluid flow paths from a fuel reservoir to the filter assembly 100, through the filter cartridge, and away from the filter assembly 100 to downstream systems. A water bowl 116 is suspended from the bottom of the filter cartridge 118 and in fluid communication with the interior of the cartridge 118. Water separated from the fuel flowing through the cartridge descends into the water bowl through a drain in the bottom of the cartridge housing, as shown in FIG. 1. A water sensor 114 is arranged in the water bowl 116 to detect a pre-determined quantity of accumulated water. The filter assembly 100 also employs a BLDC motor driven pump surrounded by a housing mounted to the top of the filter head 120 as shown in FIG. 1. The motor/pump housing cooperates with a cover 125 to secure a PC board 128 in a sealed enclosure, as shown in FIG. 1.

In the embodiment of FIG. 2, the WIF circuit 112 is arranged on the same PC board 128 as the motor control circuit 130. The circuits 112, 130 can share the power and ground from connector 132, but may otherwise be functionally separate circuits. It may be necessary to provide some buffering, shielding, and/or noise protection for the WIF circuit 112, given its close proximity to the active motor control circuit 130. Connector 132 may be a four conductor arrangement with room for power, ground, incoming signal from the water sensor 114 and an outgoing “water present” signal. This disclosed arrangement significantly reduces the part count and cost of connecting the filter assembly 100 to the host equipment (not shown).

It is possible to employ fluid pressure generated by the BLDC motor driven pump to evacuate water from the water bowl. In such an arrangement, the water present signal from the WIF circuit 112 could be easily transmitted to the motor control circuit 130 to initiate a water evacuation cycle. In the embodiments of FIGS. 1 and 2, the water present signal is transmitted to the host equipment. In an alternative embodiment that employs the filter assembly pump to evacuate water, the filter assembly may be effectively “self-contained”, where water detection and water evacuation are handled by the filter assembly itself. This would eliminate the need to transmit the water present signal to the host equipment and potentially simplify the interface between the filter assembly and the host equipment still further.

Claims

1. A fuel filter assembly comprising: an electric motor connected to drive a pump to circulate fuel through filter media contained in a filter enclosure;a water accumulation chamber in fluid communication with said filter enclosure and situated where water separated from said fuel passing through said filter media descends into said water accumulation chamber;a sensor in said water accumulation chamber and configured to detect the presence of a pre-determined quantity of water in said water accumulation chamber;a water in fuel circuit connected to monitor said sensor and generate a water present signal when said pre-determined quantity of water is detected;wherein said electric motor and said water in filter circuit are connected to a host equipment by the same electrical connector.

2. The fuel filter assembly of claim 1, wherein said electric motor is a BLDC motor and said filter assembly includes a motor control circuit to drive said BLDC motor, said motor control circuit and said water in filter circuit being mounted to a common PC board.

3. The fuel filter assembly of claim 2, wherein said PC board is located in a compartment defined by a housing that surrounds the electric motor and pump.

4. The fuel filter assembly of claim 2, wherein said motor control circuit and water in filter circuit share power and ground but are otherwise functionally separate.