Variable displacement piezo-electric pumps

A variable displacement piezo-electric pump which includes a pump housing having a side housing wall defining a pump chamber, an inlet line and an outlet line communicating with the pump chamber, a flexible pump diaphragm spanning the side housing wall in the pump chamber, a diaphragm-stroking mechanism such as a piezo-electric stack engaging the pump diaphragm and a diaphragm support provided between the diaphragm-stroking mechanism and the side housing wall of the pump housing.

TECHNICAL FIELD

The present disclosure relates to pumps. More particularly, the present disclosure relates to variable displacement piezo-electric pumps which are characterized by optimum flow capabilities under high and low pressures.

BACKGROUND

A typical hydraulic actuator has two distinct types of flow demand: high flow to stroke the clutch at relatively low pressures and low flow at high pressure to control the capacity of the clutch. A single piezo-electric pump having a traditional design cannot be optimized for both flow conditions. Such a pump has either a low flow and high pressure capability or a high flow and limited pressure capability. The pressure is dictated by the maximum force that the piezo-electric stack can generate and by the area of the pump piston.

SUMMARY

The present disclosure is generally directed to a variable displacement piezo-electric pump. An illustrative embodiment of the pump includes a pump housing having a side housing wall defining a pump chamber, an inlet line and an outlet line communicating with the pump chamber, a flexible pump diaphragm spanning the side housing wall in the pump chamber, a piezo-electric stack engaging the pump diaphragm and a diaphragm support provided between the piezo-electric stack and the side housing wall of the pump housing.

DETAILED DESCRIPTION

Referring initially toFIGS. 1-3of the drawings, an illustrative embodiment of a continuous diaphragm piezo-electric variable displacement pump, hereinafter pump, is generally indicated by reference numeral1. As shown inFIG. 1, the pump1includes a pump housing2which may include a first housing wall2a, a second housing wall2band a side housing wall2cwhich extends between the first housing wall2aand the second housing wall2b. The pump housing2may be generally cylindrical or may have any other suitable alternative shape and has a pump housing interior3.

A flexible or elastomeric pump diaphragm4spans the side housing wall2cand divides the pump housing interior3into a first pump chamber3aand a second pump chamber3b. The pump diaphragm4may be circular and includes an outer diaphragm portion4aand an inner diaphragm portion4b. A diaphragm stiffener/retainer5, which may be disc-shaped, may be provided on the inner diaphragm portion4bin the first pump chamber3aof the pump housing interior3. In some embodiments, the pump diaphragm4may have a tapered thickness to promote the change in displacement of the working fluid32in the first pump chamber3a. This may allow for removal of the support18from the second pump chamber3b.

An inlet valve9, which may be a suction check valve, for example, communicates with the first pump chamber3a. The inlet valve9may extend through the first housing wall2a, for example, as shown; alternatively, the inlet valve9may extend through the side housing wall2c. An inlet suction line8communicates with the inlet valve9and extends from the pump housing2. An outlet check valve13communicates with the first pump chamber3aand may extend through the first housing wall2a, as shown, or through the side housing wall2c. A high-pressure outlet line12communicates with the outlet check valve13and extends from the pump housing2.

A piezo-electric stack16or other diaphragm-stroking mechanism is provided in the second pump chamber3bof the pump housing interior3. The piezo-electric stack16extends from the second housing wall2band engages the inner diaphragm portion4bof the pump diaphragm4. A diaphragm support18extends from the second housing wall2bbetween the piezo-electric stack16and the side housing wall2c. The diaphragm support18may be annular and may encircle the piezo-electric stack16. A vent6is provided in the second housing wall2bas shown, or alternatively, in the side housing wall2c. The vent6establishes pneumatic communication between the second pump chamber3band the ambient air outside the pump housing2. A vent19may extend through the diaphragm support18to establish pneumatic communication between the inner and outer portions of the second pump chamber3b. Multiple support diaphragms, pistons and intermediate supports can be used in conjunction with the pump diaphragm4according to the knowledge of those skilled in the art.

In typical application, the pump1can be operated under low-pressure conditions and high-pressure conditions. Working fluid32flows into the first pump chamber3aof the pump housing interior3through the inlet suction line8and inlet valve9, respectively. As shown inFIG. 2, under low-pressure conditions of the working fluid32in the first pump chamber3a, the piezo-electric stack16expands and contracts, stroking both the inner diaphragm portion4band the outer diaphragm portion4aof the pump diaphragm4, as indicated by the arrow20. Simultaneously, an external fluid33, which may be gas or liquid, either at ambient or a controlled pressure, flows into and out of the second pump chamber3bof the pump housing interior3through the vent6. External fluid33may also flow between the outer and inner portions of the second pump chamber3bthrough the vent19extending through the diaphragm support18. The substantially full diameter of the pump diaphragm4provides displacement of a large volume of working fluid32in the first pump chamber3a. This results in flow of a large volume of the working fluid32from the first pump chamber3a, through the outlet check valve13and the high-pressure outlet line12, respectively.

As shown inFIG. 3, under high-pressure conditions of the working fluid32in the first pump chamber3a, the working fluid32presses against the pump diaphragm4, which is forced and seated against the diaphragm support18. The piezo-electric stack16expands and contracts, stroking only the inner diaphragm portion4bof the pump diaphragm4as indicated by the arrow20, as the high pressure of the working fluid32in the first pump chamber3acontinues to press the outer diaphragm portion4aof the pump diaphragm4against the diaphragm support18. The displaced inner diaphragm portion4bof the pump diaphragm4provides displacement of a small volume of working fluid32in the first pump chamber3a. This results in flow of a small volume of the working fluid32from the first pump chamber3a, through the outlet check valve13and the high-pressure outlet line12, respectively.

Referring next toFIGS. 4-6of the drawings, an illustrative embodiment of a variable displacement piezo-electric diaphragm pump, hereinafter pump, is generally indicated by reference numeral1a. The pump1aincludes a pump housing2which may have the same design and shape as that of the pump1heretofore described with respect toFIGS. 1-3. In the pump1a, a pump diaphragm, which may be a diaphragm and piston assembly24, spans the side housing wall2cof the pump housing2and divides the pump housing interior3into the first pump chamber3aand the second pump chamber3b. The diaphragm and piston assembly24may include, for example, a flexible outer low-pressure diaphragm28which may be annular and extends from the side housing wall2cinto the pump housing interior3. An outer low-pressure piston27, which may be annular, extends inwardly from the outer low-pressure diaphragm28. A high-pressure diaphragm26, which may be circular, is provided at the center of the outer low-pressure piston27. An inner high-pressure piston25is provided on the high-pressure diaphragm26. The piezo-electric stack16in the second pump chamber3bengages the high-pressure diaphragm26. In some embodiments, the stiffness of the outer low-pressure diaphragm28may be selected such that as the pressure of working fluid32in the first pump chamber3arises, the outer low-pressure piston27is held in place by the increasing pressure of the working fluid32. This may render unnecessary the presence of the diaphragm support18in the second pump chamber3b. Multiple support diaphragms, pistons and intermediate supports can be used in conjunction with the diaphragm and piston assembly24according to the knowledge of those skilled in the art.

In typical application, the pump1acan be operated under low-pressure conditions and high-pressure conditions. Working fluid32flows into the first pump chamber3aof the pump housing interior3through the inlet suction line8and inlet valve9, respectively. As shown inFIG. 5, under low-pressure conditions of the working fluid32in the first pump chamber3a, the piezo-electric stack16expands and contracts and strokes the inner high-pressure piston25, as indicated by the arrow20. Due to the stiffness of the high-pressure diaphragm26, the outer low-pressure piston27is stroked with the inner high-pressure piston25. Simultaneously, external fluid33, which may be gas or liquid, either at ambient or a controlled pressure, is drawn into and out of the second pump chamber3bof the pump housing interior3through the vent6. Stroking of substantially the full diameter of the diaphragm and piston assembly24provides displacement of a large volume of working fluid32in the first pump chamber3a. This results in flow of a large volume of the working fluid32from the first pump chamber3a, through the outlet check valve13and the high-pressure outlet line12, respectively.

As shown inFIG. 6, under high-pressure conditions of the working fluid32in the first pump chamber3a, the working fluid32presses against the diaphragm and piston assembly24. Therefore, the outer low-pressure piston27is forced and seated against the diaphragm support18and the outer low-pressure diaphragm28is deflected into the second pump chamber3b. The piezo-electric stack16expands and contracts in the direction indicated by the arrow20, stroking only the inner high-pressure piston25and the high-pressure diaphragm26, as the high pressure of the working fluid32in the first pump chamber3acontinues to press the outer low-pressure piston27of the diaphragm and piston assembly24against the diaphragm support18. The stroking action of the inner high-pressure piston25of the diaphragm and piston assembly24provides displacement of a small volume of working fluid32in the first pump chamber3a. This results in flow of a small volume of the working fluid32from the first pump chamber3a, through the outlet check valve13and the high-pressure outlet line12, respectively.

While the preferred embodiments of the disclosure have been described above, it will be recognized and understood that various modifications can be made in the disclosure and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the disclosure.