Variable displacement compressors which estimate an inclination angle of a plate of the compressor

1. A variable displacement compressor comprising:

a plate having a variable inclination angle;

a piston engaging the plate, wherein the piston reciprocates within a bore of the compressor in accordance with a rotation of the plate, and the piston has a stroke length which is determined by the inclination angle of the plate;

a sensor positioned adjacent to the piston, wherein the sensor generates an output signal when at least one predetermined portion of the piston is aligned with the sensor; and

a processing unit operationally coupled to the sensor, wherein the processing unit estimates the inclination angle of the plate based on at least the output signal from the sensor.

2. The compressor of claim 1 , wherein the piston comprises:

a piston head; and

a piston tail connected to the piston head, wherein the piston tail engages the plate.

3. The compressor of claim 2 , wherein the piston head or the piston tail comprises at least one recess formed therein, and the at least one predetermined portion of the piston comprises the at least one recess.

4. The compressor of claim 2 , wherein the piston head or the piston tail comprises at least one recess formed therein, and at least one piston surface positioned outside the recess, wherein the at least one predetermined portion of the piston comprises the at least one piston surface.

5. The compressor of claim 1 , wherein the piston comprises:

a first portion;

a second portion; and

a third portion, wherein the second portion is positioned between the first portion and the third portion, and the at least one predetermined portion of the piston comprises the first portion and the third portion, such that the output signal is a pulsed output signal.

6. The compressor of claim 5 , wherein the processing unit comprises:

a counter circuit for generating a pulse count of the output signal, wherein the counter circuit is operationally coupled to the sensor;

a voltage smoothing circuit for averaging a voltage of the output signal to generate an average voltage of the output signal, wherein the voltage smoothing circuit is operationally coupled to the sensor; and

an inclination angle estimating circuit for estimating the inclination angle of the plate based on at least the average voltage and the pulse count, wherein the inclination angle estimating circuit is operationally coupled to each of the counter circuit and the voltage smoothing circuit.

7. The compressor of claim 6 , further comprising a rotational speed detection circuit for directly or indirectly detecting a rotational speed of the plate, wherein the processing unit further comprises a cycle calculating circuit for calculating a rotational cycle of the plate, wherein the cycle calculating circuit is operationally coupled to the rotational speed detection circuit and the counter circuit.

8. The compressor of claim 7 , wherein the processing unit further comprises a memory unit for storing data associated with a predetermined relationship between the inclination angle, the pulse count, and the average voltage, wherein the memory unit is operationally coupled to the inclination angle estimating circuit, and the inclination angle estimating circuit estimates the inclination angle based on the average voltage, the pulse count, and the data associated with the predetermined relationship.

9. The compressor of claim 1 , further comprising:

a volume calculating circuit for calculating a discharge volume of the compressor, wherein the volume calculating circuit is operationally coupled to the processing unit.