Variable displacement reciprocating piston unit generating piston stroke speed and piston stroke length signal

Patent metadata

Field	Value
Publication number	US-11035358-B2
Application number	US-202016803138-A
Country	US
Kind code	B2
Filing date	Feb 27, 2020
Priority date	Feb 28, 2019
Publication date	Jun 15, 2021
Grant date	Jun 15, 2021

Abstract

A variable displacement reciprocating piston unit includes a sensor probe, a target, a piston having a top dead center position and a bottom dead center position, and a signal processing unit. The sensor probe, the target, and the piston are located in relation to each other so that the target is moved from being absent from the sensor probe to being present at the sensor probe when the piston travels towards the top dead center position, and the target is moved from being present at the sensor probe to being absent from the sensor probe when the piston travels towards the bottom dead center position. The signal processing unit generates a signal indicating a stroke speed and a stroke length of the piston from a signal from the sensor probe indicating a presence and/or an absence of the target as the target moves relative to the sensor probe.

First claim

What is claimed is:

1. A variable displacement reciprocating piston unit, comprising:
a sensor probe;
a target that is a target area;
a piston having a top dead center position and a bottom dead center position, the sensor probe, the target, and the piston are located in relation to each other so that the target is moved from being absent from the sensor probe to being present at the sensor probe when the piston travels towards the top dead center position, and the target is moved from being present at the sensor probe to being absent from the sensor probe when the piston travels towards the bottom dead center position; and
a signal processing unit configured to:
receive a signal from the sensor probe indicating a presence and/or an absence of the target as the target moves relative to the sensor probe, the signal allows a plurality of first timestamps to be measured when the target moves from being present at the sensor probe to being absent from the sensor probe, and the signal allows a plurality of second timestamps to be measured when the target moves from being absent from the sensor probe to being present at the sensor probe;
determine a periodicity of the piston by applying a first function to at least two timestamps of the first timestamps or at least two timestamps of the second timestamps;
determine a target duty cycle ratio by comparing a target pulse duration generated from at least one timestamp of the first timestamps and at least one timestamp of the second timestamps with the periodicity; and
generate a signal indicating a stroke speed and a stroke length of the piston from the periodicity and the target duty cycle ratio.

2. The variable displacement reciprocating piston unit of claim 1 , wherein:
the target is indicated by a change of current carrying capacity and/or a change of a piston topography in a location of the target;
the change of the piston topography is one or more of: an air gap in the piston, a recess in the piston, a groove on the piston, a slope or edge of the piston, or a hole in or of the piston;
the change of current carrying capacity is a result of a target material with an electrical conductivity different from a material of the piston, the target material is a copper or a hard potting; and/or
the change of current carrying capacity is a result of the change of the piston topography.

3. The variable displacement reciprocating piston unit of claim 1 , wherein
the target area has a convex topography, is bow shaped, and/or is designed in an arched manner;
a topography of the target area compensates for an axial rotation movement of the piston; and/or
an air gap between the sensor probe and the target is substantially independent of piston axial rotation within ±3° of an un-rotated and/or initial piston position.

4. The variable displacement reciprocating piston unit of claim 1 , wherein:
a sensor including the sensor probe and the processing unit is an eddy current sensor; and/or
the signal of the sensor probe is directly measured or derived from a demodulation and/or a signal processing.

5. The variable displacement reciprocating piston unit of claim 4 , wherein the sensor probe includes a sensor coil, the sensor coil is a flat wound coil on a bobbin and/or a flat coil on a PCB in one or more layers.

6. The variable displacement reciprocating piston unit of claim 5 , wherein the sensor coil has a transmitting coil and a receiving coil that are either wound coils or PCB coils on different layers, and/or a resonance signal of the sensor probe is induced in the receiving coil and either a voltage, a current, a frequency, or a phase shift is processed in order to create a demodulated signal.

7. The variable displacement reciprocating piston unit of claim 1 , wherein the sensor probe is located to indicate the presence of the target in top dead center position, and to indicate the absence of the target in the bottom dead center position.

8. The variable displacement reciprocating piston unit of claim 1 , wherein:
a map translating and/or linearizing from the target duty cycle ratio to the stroke length is used to derive the stroke length from the target duty cycle ratio;
the map includes at least one functional relationship including at least one polynomial function, at least one trigonometric function, and/or a look-up table; and
at least one functional relationship is stored in the look-up table.

9. The variable displacement reciprocating piston unit of claim 1 , further comprising a calibration target, the sensor probe indicating a presence and an absence of the calibration target as the calibration target moves relative to the sensor probe, the processing unit is configured to calibrate the stroke length of the piston using the indication of the presence of the calibration target, the calibration target is located on the piston.

10. The variable displacement reciprocating piston unit of claim 9 , wherein calibrating the stroke length includes generating a calibration duty cycle ratio from a calibration timestamp measured when the calibration target moves from being absent from the sensor probe to being present at the sensor probe, or when the calibration target moves from being present at the sensor probe to being absent from the sensor probe, the calibration timestamp is compared with the first and/or second timestamps to derive a calibration duty cycle using the relationship:

D
⁢

C
cal

=

t
2

-

t
1

t
4

-

t
1

where DC cal is the calibration duty cycle, t 1 and t 4 are a pair of raising or falling edges of the signal from the sensor probe, and t 2 is a raising or falling edge of the calibration target.

11. The variable displacement reciprocating piston unit of claim 10 , wherein calibrating the stroke length further includes correcting the target duty cycle ratio with a correcting factor or a correction function, the correcting factor or the correction function derived from the calibration duty cycle ratio and the target duty cycle, and a pre-stored accurate correlation between calibration duty cycle ratio and target duty cycle, the correcting factor or the correction function is applied to a map translating from target duty cycle ratio to stroke length.

12. The variable displacement reciprocating piston unit of claim 9 , wherein calibrating the generated stroke length is performed when the piston stroke length is above a minimum stroke length required for the sensor probe to indicate the presence of the calibration target, during compressor and/or vehicle end-of-line test or during normal operations and with a certain time interval or at vehicle start-up.

13. The variable displacement reciprocating piston unit of claim 12 , wherein the minimum stroke length required for the sensor to indicate the presence of the calibration target is greater than ⅔ of maximum stroke length.

14. The variable displacement reciprocating piston of claim 9 , wherein the calibration

Assignees

• Te Connectivity Germany Gmbh
• Hanon Systems

Inventors

• Kwak Jung Myung
• Kim Yong-Hee

Classifications

• F04B2207/046

  of length of piston stroke · CPC title

• F04B2201/0201

  Position of the piston · CPC title

• F04B49/12

  by varying the length of stroke of the working members · CPC title

• F04B49/06 Primary

  Control using electricity (regulating by means of floats actuating electric switches F04B49/04) · CPC title

• F04B2201/0207

  Number of pumping strokes in unit time · CPC title