Variable displacement reciprocating piston unit generating piston stroke speed and length signals
阅读说明：本技术 生成活塞冲程速度和长度信号的可变排量往复活塞单元 (Variable displacement reciprocating piston unit generating piston stroke speed and length signals ) 是由 郭正命 金镕熙 于 2020-02-27 设计创作，主要内容包括：本发明提供一种可变排量往复活塞单元,以改善活塞单元性能。可变排量往复活塞单元包括处理单元、传感器探头和目标。处理单元配置为：从传感器探头接收信号,当目标从在传感器探头处存在移动到在传感器探头处不存在时,信号允许测量第一时间戳,当目标从在传感器探头处不存在移动到在传感器探头处存在时,信号允许测量第二时间戳；通过将第一函数应用于所述第一时间戳中的至少两个时间戳或所述第二时间戳中的至少两个时间戳来确定活塞的周期性；通过将由第一时间戳和第二时间戳生成的目标脉冲持续时间与周期性进行比较,确定目标占空比；并且根据周期性和目标占空比生成指示冲程速度和冲程长度的信号。(The present invention provides a variable displacement reciprocating piston unit to improve the performance of the piston unit. The variable displacement reciprocating piston unit includes a processing unit, a sensor probe, and a target. The processing unit is configured to: receiving a signal from the sensor probe, the signal allowing a first timestamp to be measured when the target moves from being present at the sensor probe to being absent at the sensor probe, the signal allowing a second timestamp to be measured when the target moves from being absent at the sensor probe to being present at the sensor probe; determining a periodicity of the plunger by applying a first function to at least two of the first timestamps or at least two of the second timestamps; determining a target duty cycle by comparing a target pulse duration generated by the first timestamp and the second timestamp to the periodicity; and generating a signal indicative of the stroke speed and the stroke length in accordance with the periodicity and the target duty cycle.)
1. A variable displacement reciprocating piston unit (100) for generating signals (635) indicative of piston stroke speed and stroke length of at least one piston (110), the variable displacement reciprocating piston unit (100) comprising at least one processing unit (610), at least one sensor probe (130) and at least one target (140), the piston (110) having a top dead center position (TDC) and a bottom dead center position (BDC), the processing unit configured to:
receiving (310) a signal from the sensor probe (130), the sensor probe (130) indicating the presence (440) and/or absence (430) of the target (140) as the target (140) moves relative to the sensor probe (130), the signal allowing measurement of a first timestamp (410) when the target (140) moves from the presence (440) at the sensor probe (130) to the absence (430) at the sensor probe (130), and the signal allowing measurement of a second timestamp (420) when the target (140) moves from the absence (430) at the sensor probe (130) to the presence (440) at the sensor probe (130);
determining (320) a periodicity of the piston (110) by applying a first function to at least two of the first timestamps (410) or at least two of the second timestamps (420);
determining (330) a target duty cycle by comparing a target pulse duration generated by at least one of the first timestamps (410) and at least one of the second timestamps (420) to the periodicity; and
generating (340) a signal (635) indicative of the stroke speed and the stroke length as a function of the periodicity and the target duty cycle,
wherein the sensor probe (130), the target (140), and the piston (110) are positioned relative to each other such that when the piston (110) travels toward the top dead center position, the target (140) moves from being absent (430) at the sensor probe (130) to being present at the sensor probe (130), and when the piston (110) travels toward the bottom dead center position, the target (140) moves from being present (440) at the sensor probe (130) to being absent (430) at the sensor probe (130); and
wherein the target (140) may be a target area.
2. The variable displacement reciprocating piston unit of claim 1,
wherein the target (140) is indicated by a change in current carrying capacity and/or a change in piston topography in the location of the target, wherein the change in topography preferably comprises one or more of:
an air gap in the piston is provided,
a recess in the piston, the recess being formed in the piston,
a groove on the piston is arranged on the piston,
the slope or edge of said piston, or
A bore in or of the piston, and/or
The change in the current carrying capacity may be due to a target material for the target area having a different conductivity than the material of the piston, wherein the target material may be copper or hard potting, and/or
The change in the current carrying capacity may be due to a change in the piston topography.
3. A variable displacement reciprocating piston unit as claimed in claim 1 or 2,
wherein the target area has a convex topography, is arcuate, and/or is designed in an arcuate manner, and/or
The topography of the target area compensates for axial rotational movement of the piston, and/or
The air gap between the sensor probe and the target is substantially independent of certain piston axial rotations, such as small piston axial rotations, e.g., piston axial rotations within ± 3 ° of the initial piston position and/or non-rotation.
4. A variable displacement reciprocating piston unit as claimed in any one of the preceding claims,
wherein the sensor comprising the sensor probe (130) and the processing unit (610) is an eddy current sensor; and/or
Wherein the signal, e.g. voltage, current, frequency or phase shift, of the sensor probe (130) is directly measured (460) or derived from demodulation and/or signal processing (450).
5. The variable displacement reciprocating piston unit of claim 4,
wherein the sensor probe (130) comprises at least one sensor coil (135) and the sensor coil (135) is preferably a flat wound coil on a bobbin and/or one or more layers of flat coils on a PCB.
6. The variable displacement reciprocating piston unit of claim 5,
wherein the sensor coil (135) has a transmitting coil and a receiving coil, which are wound coils or preferably PCB coils on different layers, and/or
Wherein the sensor signal (460) is induced in the receiving coil and a voltage, current, frequency or phase shift is processed to generate the signal (450).
7. A variable displacement reciprocating piston unit as claimed in any one of the preceding claims,
wherein the sensor probe (130) is positioned such that the sensor indicates that the target is present in a top dead center position, and
the sensor probe (130) is preferably positioned such that the sensor indicates that the target is not present in a bottom dead center position.
8. A variable displacement reciprocating piston unit as claimed in any one of the preceding claims,
wherein a mapping that converts and/or linearizes a target duty cycle to a stroke length is used to derive the stroke length from the target duty cycle;
wherein the mapping preferably comprises at least one functional relationship, for example a relationship comprising at least one polynomial function, and/or at least one trigonometric function, and/or a look-up table; and is
Wherein the at least one functional relationship is preferably stored in a look-up table.
9. A variable displacement reciprocating piston unit as claimed in any one of the preceding claims,
wherein the variable displacement reciprocating piston unit (100) further comprises a calibration target (150), the sensor probe (130) indicating the presence and absence of the calibration target (150) when the calibration target (150) moves relative to the sensor probe (130); and is
Wherein the processing unit is further configured to calibrate the generated stroke length of the piston using the indication of the presence of the calibration target (150); and
wherein the calibration target (150) is preferably located on the piston.
10. The variable displacement reciprocating piston unit of claim 9,
wherein the step of calibrating the generated stroke length comprises generating a calibration duty cycle from a calibration time stamp measured when the calibration target (150) is moved from being absent from the sensor probe (130) to being present at the sensor probe (130), or when the calibration target (150) is moved from being present at the sensor probe (130) to being absent from the sensor probe (130), and
wherein the calibration time stamp is preferably compared with the first and/or second time stamp to derive a calibration duty, preferably using the following relation:
wherein, DCcalIs the calibration duty, t1And t4Are two rising or falling edges of the target signal, and t2Is the rising or falling edge of the calibration target.
11. The variable displacement reciprocating piston unit of claim 10,
wherein the step of calibrating the generated stroke length further comprises correcting the target duty cycle with a correction factor or a correction function derived from a pre-stored accurate correlation between the calibration duty cycle and the target duty cycle and between the calibration duty cycle and the target duty cycle, and
wherein the correction factor or the correction function is preferably applied to a map converting from a target duty cycle to a stroke length.
12. The variable displacement reciprocating piston unit of any one of claims 9 to 11,
wherein the step of calibrating the generated stroke length is performed when the piston stroke length is higher than a minimum stroke length required by the sensor probe to indicate the presence of the calibration target (150), preferably during compressor and/or vehicle end-of-line testing or normal operation, e.g. at certain time intervals or at vehicle start-up.
13. The variable displacement reciprocating piston unit of claim 12,
wherein the minimum stroke length required by the sensor to indicate the presence of the calibration target (150) is preferably higher than 2/3 of a maximum stroke length.
14. The variable displacement reciprocating piston unit of any one of claims 9 to 13,
wherein the calibration target (150) is indicated by a change in ampacity and/or a change in piston topography in the target location, and the change in ampacity may be due to the change in topography;
and
wherein the change in topography preferably comprises one or more of:
an air gap in the piston is provided,
a recess in the piston, the recess being formed in the piston,
a recess in the piston (100) and,
the slope or edge of the piston is such that,
a bore of the piston;
wherein the calibration target (150) is preferably a recess in the piston, preferably an oil groove.
15. A variable displacement reciprocating piston unit as claimed in any one of claims 9 to 14,
wherein the presence of the calibration target (150) is distinguishable from the presence of the target (140),
preferably using an uncalibrated piston stroke length signal, or
By using the difference in time between two calibration target frequency changes compared to the time between the main target frequency change and the calibration frequency change, or
By using the difference in frequency and/or phase shift variation between the target and the calibration target, which is preferably generated by the difference in topography and/or material that results in different induced eddy currents when the target and the calibration target are moved relative to the sensor probe.
16. A variable displacement reciprocating piston unit as claimed in any one of the preceding claims,
wherein the step of generating the signal (635) indicative of the stroke speed and the stroke length comprises a linearization of the target duty cycle, and the target duty cycle is given by the equation:
wherein pulse width ON _ time is a duration of time that the sensor probe (130) indicates the presence of the target, OFF _ time is a duration of time that the sensor probe (130) indicates the absence of the target.
Technical Field
The present application relates to an improved variable displacement reciprocating piston unit that generates signals indicative of the current piston stroke speed and piston stroke length with low latency.
Background
Hereinafter, a variable displacement reciprocating piston unit will be described in the context of a variable displacement compressor. However, this is only an example of the background of the invention. It will be apparent to those skilled in the art that the present invention may be applied to any variable displacement reciprocating piston unit, machine and/or aggregate, such as a variable displacement compressor or pump.
US patent publication US 6,991,435B2 relates to a variable displacement compressor comprising a processing unit that estimates the inclination angle of a swash plate based on the output signal of a sensor.
Disclosure of Invention
The object of the invention is to improve efficiency, reduce fuel consumption and reduce exhaust emissions in vehicle operation. Another object of the present invention includes improving the safety of the air conditioning operation of the vehicle and improving the operational reliability of the air conditioning compressor. Another object is to improve accuracy and reduce the latency of compressor torque calculations. Another object is to provide additional monitoring capability of compressor operation. Another object is to improve accuracy and reduce delay in compressor piston stroke length feedback and improve feedback of compressor piston reciprocation frequency.
The object of the invention is solved by the subject matter of
In particular, these objects are solved by a variable displacement reciprocating piston unit, such as a compressor or a pump, for generating signals indicative of piston stroke speed (reciprocation frequency) and piston stroke length, comprising at least one processing unit, at least one sensor probe, at least one target, the piston having a Top Dead Center (TDC) and a Bottom Dead Center (BDC), and the at least one processing unit being configured to receive the signals from the sensor probe, the sensor probe indicating the presence and/or absence of the target when the target moves relative to the sensor probe, the signals allowing a first time stamp to be measured when the target moves from being present at the sensor probe to being absent at the sensor probe (the time may be measured at an edge or side of the signal), and when the target moves from being absent at the sensor probe to being present at the sensor probe, the signal allows measurement of a second timestamp; determining a periodicity (i.e., between two edges and/or two sides) by applying a first function to at least two of the first timestamps or at least two of the second timestamps; the periodicity may be related to the time period or reciprocating frequency of the piston. The first timestamp may correspond to a rising edge of the signal and the second timestamp may correspond to a falling edge (side) of the signal. The first timestamp may correspond to a falling edge (side) of the signal and the second timestamp may correspond to a rising edge of the signal, the target duty cycle being determined by comparing a target pulse duration generated by at least one of the first timestamps and at least one of the second timestamps to a time period; and generating signals indicative of stroke speed (or stroke frequency) and stroke length as a function of the time period and the target duty cycle, wherein the sensor probe, the target and the piston are positioned relative to each other such that the target moves from being absent at the sensor probe to being present at the sensor probe when the piston travels towards a Top Dead Centre (TDC) position and such that the target moves from being present at the sensor probe to being absent at the sensor probe when the piston travels towards a Bottom Dead Centre (BDC) position;
advantages of the present invention include faster and significantly more accurate piston motion feedback. Faster, more accurate piston motion feedback can improve vehicle efficiency and reduce fuel consumption and exhaust emissions by increasing the speed of swash plate angle control (especially by enabling new compressor controls). The swash plate angle, and therefore the piston stroke length, is typically controlled by adjusting the pressure differential across the compressor. Previous compressor designs included "bleed holes". The bleed holes cause compressed refrigerant to flow from the crankcase chamber of the compressor back into the suction chamber, thereby increasing power consumption and temperature. The invention allows reducing or closing the bleed holes. Closing or reducing the bleed holes results in more stringent requirements for swashplate control. Without the bleed holes, it is important to react very quickly to the swash plate movement. Using the signal of the invention, an unstable swash plate can be stabilized in the control circuit, in particular the piston stroke length which can be calculated directly from the signal or derived from the signal, so that a more precise control is possible.
The invention also allows for improved compressor control using piston speed or compressor speed, respectively, which can be calculated directly from the sensor signal to react very quickly to any compressor speed change.
In addition, the present invention allows the mass flow rate of the compressor to be directly calculated from the direct piston velocity and stroke length using a signal (e.g., from a suction chamber pressure sensor).
The invention can also be used to calculate additional physical values besides piston stroke speed and piston stroke length. These may include displacement rate, clearance volumetric efficiency, work of the compressor, coefficient of friction (piston to cylinder), refrigerant mass flow, and the like. These calculations may require other sensor information.
To obtain the highest accuracy of the mass flow calculation, values indicating the discharge pressure, the suction temperature and the discharge temperature figure may be included in addition to the piston velocity, the piston stroke and the suction pressure. In the case where more sensor values are input, the accuracy of the mass flow rate calculation is further improved.
Thus, the desired mass flow of the compressor can be achieved by adjusting the swash plate angle until the desired mass flow is achieved. The actual compressor torque can be calculated more quickly and accurately by using the method. A faster and more accurate calculation of the actual compressor torque can be input to the engine control unit to make vehicle operation more efficient and smoother.
The present invention improves the safety of vehicle air conditioning operation and the operational reliability of the air conditioning compressor by allowing additional and direct monitoring of the compressor operation. If the speed and/or load of the compressor is exceeded, appropriate action may be taken (e.g., sending a warning signal to a user and/or reducing the load of the compressor and/or shutting down the compressor). The additional signal of piston speed can be compared to an independent signal of engine speed and/or compressor rotor angular speed to directly monitor compressor faults such as compressor lock-up, compressor or liquid retention (liquid compression in the cylinder bore). Belt slip can be detected using the present invention.
The invention also allows to accurately measure the material thickness of, for example, the piston skirt, so that piston wear can be detected early, thereby increasing the operational reliability of the air conditioning compressor.
More accurate and faster piston data runs faster back to the climate control system, thereby enabling more precise climate control, further reducing energy consumption and improving passenger comfort, for example in the case of measuring high peak torque. In this case, the present invention allows the compressor torque to be reduced.
One feature that contributes to the object of the invention is a sensor and a target that allow the processing unit to measure a time stamp during which the piston is located at a predetermined distance in a part of the stroke. The piston velocity and piston stroke length can be derived by extracting the time stamp of when the edge of the target moves past the sensor probe.
The periodicity of the plungers may be derived from the time difference of at least two of the first time stamps (the time difference between the two "falling" sides) or the time difference of at least two of the second time stamps (the time difference between the two "rising" edges). The periodicity may also be derived by measuring every nth timestamp (e.g. every third timestamp) of the first and/or second timestamp indicator. The time difference is then suitably divided by the number of intervals to arrive at a periodicity within the measured time interval. The periodicity is preferably expressed in units of time, but may also be expressed in units of time (frequency) with corresponding computational correction.
In this way, the periodicity (i.e., the reciprocation/rotation time of the piston/swash plate/compressor) may be calculated from the time difference between the first rising edge and the second rising edge or the first falling edge and the second falling edge of the signal to indicate the presence or absence of the target.
The target duty cycle may be derived by comparing a target pulse duration with a periodicity, preferably dividing the target pulse duration by the periodicity, the target pulse duration typically being derived by measuring the time between one or more of the first timestamps and one or more of the second timestamps (the time between "up" and "down", or the time between "down" and "up"). By dividing the pulse duration by the periodicity, a target duty cycle independent of stroke speed can be derived.
The target duty cycle corresponds to the amount of time that the target appears at the sensor probe during the entire piston stroke. Since the time that the target is present at the sensor probe plus the time that the target is absent from the sensor probe is equal to the time of the full stroke, the target duty cycle may also be defined as the time that the target is absent from the sensor probe during the time of the full piston stroke with a corresponding computational adjustment.
The piston stroke reciprocation time may be expressed as a frequency.
Wherein T isrecIs the piston reciprocation time, frecIs the piston stroke reciprocation frequency.
The piston stroke length may be expressed as a target duty cycle or may be derived from the target duty cycle by converting the duty cycle to a stroke length.
The piston stroke length may be adjusted for non-sinusoidal piston motion (for stroke lengths, or for certain stroke lengths, e.g. for longer stroke lengths). The piston stroke length may also be adjusted for a particular swash plate piston connection design and hysteresis in piston motion.
In one embodiment, the calibration target is indicated by a change in ampacity in the target location and/or a change in piston topography, and the change in ampacity may be due to the change in topography. And the change in topography may be one or more of: an air gap in the piston, a recess in the piston, a groove on the piston, a ramp or edge of the piston, or a hole in or of the piston. The change in the current carrying capacity may be due to a particular material in the target area of the piston. The particular material may be copper, aluminum, and/or hard potting or any other suitable material. The sensor probe is further preferably attached to the housing of the compressor. Advantages include a design that reduces manufacturing costs.
In one embodiment, the target area has a convex topography, is arcuate, and/or is designed in an arcuate manner, and/or the topography of the target area compensates for axial rotational movement of the piston, and/or the air gap between the sensor probe and the target is substantially independent of certain piston axial rotations, such as small piston axial rotations, e.g., no rotation and/or piston axial rotations within ± 3 ° of the initial piston position.
The rotation may be a slight initial rotational misalignment of the piston, a rotational change during operation, and/or an axial rotational drift over time, or any other rotational movement of the piston.
Another advantage of this embodiment is that the air gap between the sensor probe and the target is less dependent on (or substantially independent of) some or all of the piston axial rotational movement, which may allow for variation in piston rotation without substantially affecting the sensor signal received from the sensor probe. Another advantage of this embodiment may be to increase the robustness of the piston stroke speed and stroke length indication (robustness), and/or to increase tolerances during part manufacturing and/or assembly.
The piston may also be used without modification. For example, a ramp near the piston edge may be used, or the edge itself or other piston geometry may be used. The end of the piston skirt and/or the bottom of the piston may be used as targets. In this case, it may be necessary to adjust the sensor probe position. The sensor probe is preferably positioned such that it is on or near the target at a top dead center piston position and not on the target at a bottom dead center piston position.
In one embodiment, the sensor may include a sensor probe and a processing unit. The sensor may be an eddy current sensor. The signal indicative of the presence or absence of the target may be measured directly, for example by measuring the impedance or current of the sensor coil, or the voltage or frequency value of the signal, or may be derived/generated by demodulating the resonant frequency in a resonant circuit, or by measuring the phase shift between the transmitted and received signals affected by the induced eddy currents.
The sensor may also be a hall effect sensor. The hall effect sensor may be biased with a magnet or the target may be ferromagnetic to determine the presence and absence of the target from the sensor probe.
Advantages of sensors as eddy current sensors include contactless proximity measurements, which are substantially insensitive to material (non-conductive) in the gap between the sensor and the target. Advantages of relying on frequency modulation include improved temperature independence of target detection. To improve the accuracy of the measurement, digital and/or analog filters may be applied to the signal. The target may be a location on the piston and increase and/or suppress eddy currents compared to other portions of the piston, thereby allowing the presence/absence of the target to be detected.
Any piston topography that causes a change in air gap and/or material thickness and/or material type between the sensor probe and the piston as the piston moves to indicate the presence or absence of an object may be used.
For the use of eddy current sensors, not only the air gap but also the material thickness is important, depending on the penetration depth of the electromagnetic field in the piston material. For example, a thin plunger housing may be detected with a current sample, and any sufficient material thickness change may be used as a trigger for the target. The electrical conductivity of the piston may also be locally altered to reduce the vortex intensity or prevent vortex flow. Adding a groove or changing the thickness of the piston changes the current carrying capacity and can be used as a target and indicated by an eddy current sensor. The use of grooves as local vortex blockages may result in significant sensitivity of the sensor probe, but may also impair the mechanical stability of the piston.
The recess may be filled with a material of lesser or higher conductivity than the non-target portion of the piston. If the piston is made of aluminum, the target may be copper or a "hard" potting. Any combination of materials or different carrier capacities may be used.
To prevent vortex flow, small grooves or holes may be formed in the piston, such as by machine-defined small grooves or by drilling small holes in the target area of the piston. By machining lines in the piston or drilling small holes in the piston, the mechanical strength of the piston is significantly improved compared to a piston with one large groove. Any modification on the target area of the piston that changes the strength of the vortex compared to the rest of the piston can be used.
In one embodiment, the sensor probe comprises one or more sensor coils, preferably at least one flat wound coil on the bobbin and/or at least one flat coil of one or more layers on the bobbin. Advantages include a good compromise between accuracy and manufacturing costs.
In one embodiment, the sensor coil has a transmit coil and a receive coil, which are wound coils or preferably PCB coils on different layers, and the sensor signal is induced in the receive coil and a voltage, current, frequency or phase shift is processed to form a processed signal.
In one embodiment, the sensors are positioned such that the sensor probe indicates the presence of the target near Top Dead Center (TDC) position, and the sensors are preferably simultaneously positioned such that the sensor probe indicates the absence of the target at Bottom Dead Center (BDC) position.
The position allows to derive the target duty cycle independently of the piston stroke length, so that the stroke length can be calculated from the duty cycle in all stroke length operations.
The stroke length may be calculated independently of the piston (and compressor) speed.
In one embodiment, the stroke length is derived from the target duty cycle using a map that converts and/or linearizes the target duty cycle to the stroke length. The mapping preferably comprises one or more functional relationships, for example relationships comprising one or more polynomial functions, one or more trigonometric functions or one or more look-up tables. The functional relationships may be stored in one or more look-up tables.
The piston stroke length may be derived by interpolating between target duty cycle values (e.g., two or more consecutive target duty cycle values) to calculate a corresponding piston stroke length. The target duty cycle value may be retrieved from a look-up table. The interpolation may have an order (e.g., an nth order), such as a first order, preferably a second order, or more preferably a third order.
In one embodiment, the variable displacement reciprocating piston unit, preferably a piston, comprises a calibration target, which is preferably different from the target, and preferably coincides with the target. As the piston (and calibration target) moves past the sensor probe, the sensor probe can indicate the presence and absence of the calibration target, preferably generating a calibration duty cycle.
The problem addressed includes that the tolerance between the target position and the sensor probe position in the direction of piston movement (x-direction) affects the accuracy of calculating the piston stroke length from the duty cycle.
The processing unit may be further configured to calibrate a stroke length generated from the target duty cycle using the signal indicative of the presence of the calibration target.
The calibration may include applying a calibration factor to a map that converts the target duty cycle to the stroke length.
Such improvements may eliminate or reduce production variations and/or usage effects on piston stroke. Such improvements may also reduce manufacturing costs by reducing manufacturing tolerance requirements, thereby reducing production costs. This further improves the accuracy of the indication of the piston stroke length detection, in particular over time, since the detection can be calibrated automatically during operation.
Furthermore, for design reasons, the calculation of the stroke length is more sensitive to duty cycle variations in the lower region. This embodiment may be used to increase accuracy in the high stroke length region.
In one embodiment, the step of calibrating the generated stroke length comprises generating a calibration duty cycle from a calibration time stamp measured when the calibration target moves from absent to present on the sensor probe (falling edge) and/or when the calibration target moves from present to absent from the sensor probe (rising edge). The calibration time stamp may be compared to the first and/or second time stamp to derive a calibration duty cycle, preferably using the following relationship:
wherein, DCcalIs the calibration duty cycle, t1And t4Are two rising or falling edges of the target signal, and t2Is the rising or falling edge of the calibration target.
In one embodiment, the step of calibrating the generated stroke length comprises correcting the target duty cycle with a correction factor or function derived from a pre-stored accurate correlation between the current calibration duty cycle and the current target duty cycle, and the calibration duty cycle and the target duty cycle. The correction factor may be applied to a map that converts the target duty cycle to a stroke length.
In one embodiment, the step of 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, for example during compressor and/or vehicle end of line testing or normal operation, for example at certain time intervals, at vehicle start-up, or when the stroke length is above the minimum calibration stroke length.
In one embodiment, the minimum stroke length required for the sensor probe to indicate the presence of the calibration target may be 2/3 of the maximum stroke length, depending on the position of the sensor probe and the calibration target.
In one embodiment, the calibration target is indicated by a change in ampacity in the target location and/or a change in piston topography, and the change in ampacity may be due to the change in topography. The variations in topography may include: an air gap in the piston, a recess in the piston, a hole in or of the piston, a groove on the piston, a ramp or an edge of the piston. Oil grooves on the piston skirt may be used as calibration targets. This improvement allows the eddy current sensor to be used to indicate the presence or absence of a target. By using the oil groove as a calibration target, no additional adjustment of the piston is required, thereby avoiding additional piston machining.
In one embodiment, the signal indicative of the presence of the calibration target is distinguishable from the signal indicative of the presence of the primary target, despite the use of the same sensor probe. Uncalibrated piston stroke information may be used to distinguish between signals such as piston velocity and/or piston stroke length and/or differences in calibration and target presence durations.
That is, if the maximum possible error of an uncalibrated sensor is known, different grooves can be identified by their position on the piston by uncalibrated default piston stroke information. For example, if the maximum error is e.g. ± 5mm, then a frequency variation at the piston position higher than e.g. 15mm must belong to the calibration target.
The differentiation may also be based on the difference in time between two calibration target frequency changes (dips) compared to the time between the main target frequency dip and the calibration frequency dip.
The difference may also be based on the difference in frequency change (dip) between the target and the calibration target. The difference may be due to differences in topography and/or materials that result in different induced eddy currents as the target and calibration target move relative to the sensor probe.
The distinction between the main groove and the calibration groove ensures that the normal operation mode is not affected by the calibration groove.
In one embodiment, the step of generating a signal indicative of the stroke speed and the stroke length comprises a linearization of the target duty cycle. To improve linearization accuracy, the target duty cycle may be derived from the following equation:
the equation may correspond to a comparison between detection of the pulse width ON time (420 to 410) and the pulse width OFF time (410 to 420), where the pulse width ON time is a duration of time that the sensor probe (130) indicates the presence of the target, the OFF time is a duration of time that the sensor probe (130) indicates the absence of the target, and the Period is a sum of the ON time and the OFF time. This equation allows for better linearity and therefore better fitting of the function.
Drawings
Embodiments of the present invention are described hereinafter with reference to the accompanying drawings, in which
Fig. 1 shows a variable displacement compressor according to an embodiment of the present invention in a short stroke length operation.
FIG. 2 illustrates a variable displacement compressor according to an embodiment of the present invention in long stroke length operation.
FIG. 3 is a block diagram showing the sensor probe, processing unit and signal output.
Fig. 4 schematically shows signals that allow the extraction of the absence and presence of an object from the frequency demodulation of the resonance signal.
Fig. 5 shows steps of a method for generating a signal according to an embodiment of the invention.
Fig. 6 shows the resonant frequency signal as a function of piston distance from Top Dead Center (TDC).
Fig. 7 shows a graph depicting piston movement in three different stroke length operations.
Fig. 8 shows the same information as fig. 7 as the piston speed increases.
Fig. 9 shows the ideal position and the position of the sensor coil shifted due to tolerances.
FIG. 10 illustrates a minimum stroke length of a sensor probe to detect a calibration target.
FIG. 11 shows the resonant frequency as a function of time during two revolutions of the swash plate at 3000 RPM.
Fig. 12 shows the same arrangement as fig. 11, where tolerances have been introduced in terms of errors in the form of time offsets.
FIG. 13 illustrates an exemplary system for controlling temperature in an automobile according to one embodiment of the invention.
Detailed Description
FIG. 1 depicts the
Fig. 2 depicts the
Fig. 3 depicts a block diagram showing an overview of one embodiment of the invention. The resonant circuit 210, including the sensor coil 135, generates a signal indicative of the presence and absence of the target 140 (and optionally the calibration target 150). The indication may be by means of a frequency change in the signal, which depends on whether the object is present or not. FM demodulation 220, located in demodulation circuit 230, may demodulate the resonating signal to generate a signal indicating the presence and absence of
The
The speed and stroke sensor output signal 635 is preferably, but not limited to, a PWM, SENT, LIN, PSI5, or CAN output.
Fig. 4 depicts a demodulated signal 450 and a resonating signal 460. The demodulated signal 450 can be used to indicate the presence and absence of a target. Where the sensor is an eddy current sensor, demodulated signal 450 may be generated from FM demodulation of a frequency (such as the frequency of resonant signal 460), where the frequency of resonant signal 460 may be sensitive to changes in the impedance of eddy current sensor coil 135 due to the absence or presence of a target. The first signal 450 may also be generated in other ways, such as by decoding the signal from the
The increase in frequency shown in section 430 of figure 4 may be the result of a decrease in inductance in the resonant circuit due to the opposing magnetic fields generated by the eddy currents in the piston. The lower frequency portion 440 may be due to an increase in inductance created by a target, such as a gap in a piston.
Fig. 5 depicts steps for generating signals indicative of stroke speed and stroke length of the piston. The processing unit provides a resonant frequency circuit and receives a resonant frequency signal 460 from the resonant circuit. In
In
Fig. 6 depicts the resonant frequency in the resonant tank at different piston positions relative to Top Dead Center (TDC)710 during maximum stroke length operation. Near TDC, the resonant frequency is low, indicating the presence of the
FIG. 7 depicts a graph showing the position of a piston from Top Dead Center (TDC) as a function of time operating at 3000 RPM. The
FIG. 7 also depicts the
FIG. 8 depicts a graph showing the position of the piston from top dead center as a function of time operating at 6000 RPM. As can be seen from the figure, the corresponding calculation of the duty cycle and the piston stroke length is not affected by the variation of the compressor speed.
The piston position as a function of time is depicted as substantially sinusoidal in fig. 7 and 8. The actual position of the piston may not be approximately sinusoidal, as long as the duty cycle for the target time can be mapped to the stroke length. The mapping may be analytical and/or experimental. The mapping may also be analytical and have correction factors derived experimentally.
FIG. 9 depicts an ideal position S0，S1(case a) and offset sensor position S0’，S1' (case b). The sensor position may shift due to tolerances. The accuracy of the stroke length calculation from the duty cycle is affected by the piston movement direction (x-direction) tolerance between the target recess and the sensor position. Tolerances may be caused by the manufacture of sensor parts, the assembly of the sensor with the compressor, positional tolerances of the compressor mounting holes, and the like.
Case a) shows an example where the piston is moved from s0 to s1, i.e. the minimum stroke length in this configuration is 0.7 mm. Case a) depicts an ideal position. In this case, the resulting duty cycle is about 50%.
In case b), the position of the center of the sensor coil relative to the main groove is shifted due to tolerances. This results in a much lower duty cycle, in this example about 20%. If the stroke length is calculated using an incorrect (offset) duty cycle of 20%, the result will be an incorrect stroke length.
Thus, a calibration procedure is described which can be applied without any expensive reference piston stroke sensor, i.e. by using a second target (calibration target) on the piston. The target may be a second recess, such as an oil groove already located on the piston, without further modification of the piston.
FIG. 10 depicts a minimum stroke length of a sensor probe to detect a calibration target. The piston stroke needs to be large enough to enable the sensor probe to detect the first edge of the
As shown in fig. 10, calibration can be performed at any time when the piston stroke is large enough for the sensor probe to indicate a calibration target. Suitable times for performing the calibration include during compressor end-of-line testing or during vehicle end-of-line testing. Calibration may also be performed during vehicle operation (e.g., at intervals) or at vehicle or compressor start-up.
FIG. 11 shows the resonant frequency as a function of time during two revolutions of a swash plate rotating at 3000 RPM. FIG. 11 also shows the time (Δ t) between two calibration frequency drops1) And the time (Δ t) between the main target frequency drop and the calibration frequency drop2)。
For example, if it is known to perform calibration at the maximum stroke length, this information can be used to distinguish between a dip indicating a calibration target and a primary target. The signal will indicate four dips per revolution. Since the time (Δ t) between two calibration frequency drops is known1) Shorter than the time (at) between the main target frequency drop and the calibration frequency drop2) This can be used to distinguish between a main target drop and a calibration target drop.
Identifying the main target drop from the calibration drop may be accomplished, for example, by identifying that the groove depth (and thus the frequency drop) of the calibration groove is less than the depth of the sensor groove. The frequency drop may be due to different shapes or materials of the calibration target. Differences in the frequency drop may be detected to identify whether the frequency drop is from a primary target or a calibration target.
FIG. 12 shows the same configuration as FIG. 11, where the tolerance has been shifted in time (Δ t)error) Errors of the form are introduced as described under fig. 9 with respect to case b). The situation b) depicted in fig. 9 results in a correct frequency signal (solid line, fig. 12) which is modified to a tolerance-affected frequency signal (dash-dotted line) and results in a calculated incorrect target duty cycle.
The stroke reciprocation time (T-T4-T1) is unchanged, but the pulse width time (ON time) is reduced (T3-T1), resulting in an incorrect duty cycle and thus an incorrect stroke length calculation.
The target duty cycle for tolerance effects may be calculated as follows:
by using a signal indicative of a calibration target, incorrect duty cycles can be corrected.
The signal indicative of the calibration target may be used to calculate the calibration duty cycle. The calibration duty cycle may be independent of the axis tolerance (the time difference between the rising edge of the sensor groove (t1) and the falling edge of the calibration groove (t2) is independent of the axis tolerance). The calibration duty cycle may be defined as:
as can be seen from the equation, the time offsets of the signals can cancel each other out and the calibration duty cycle is independent of the tolerance in the piston motion detection. Similar to the target duty cycle, the calibration duty cycle is also independent of the compressor RPM.
The correction target duty cycles for one or more given calibration duty cycles are predetermined. This relationship can be stored as an algorithm or look-up table, can be calculated from the geometry of the piston, can also be measured using a reference stroke sensor, is automatically stored and can be used for all compressors of the same type. One or more point corrections may be performed using one or more known correlations between the calibration duty cycle and the target duty cycle.
Examples of the invention
From the reference measurement(s), it is known that a calibration duty cycle of 75% corresponds to a piston stroke length of 26mm, and at this stroke, the target duty cycle should be 70%.
However, due to axial tolerances, the measured target duty cycle is only 68%, meaning a 2% error. With this knowledge, a single point calibration can be performed by applying a correction factor to the target duty cycle (e.g., calibrating a complete look-up table and/or mapping) to adjust the calculation to a 70% correct output value. Alternatively, a single point calibration may be done after linearization of the sensor output.
FIG. 13 depicts a system for adjusting the cooling (or heating) capacity of a variable displacement compressor. The system may include a compressor 605, a signal processing unit 610, a compressor controller 615, and a heating ventilation and air conditioning unit (HVAC unit) 620. The system may also include a sensor signal 630, a speed and stroke signal 635, an additional sensor signal 640 (e.g., pressure in the suction portion of the compressor or pressure in the crankcase of the compressor), a swash plate angle adjustment signal 650, a compressor control signal 660, and an HVAC input signal 670. The compressor 605 may be driven by a compressor rotor angular velocity 680.
The compressor controller 615 may receive a compressor control signal 660 having a desired compressor performance (e.g., a desired piston stroke length, a desired swash plate angle, a desired refrigerant mass flow, a desired suction pressure and/or a desired evaporator outlet air temperature, and/or a desired compressor torque).
To efficiently and accurately achieve the desired compressor performance, the controller reads the speed and stroke signal 635 from the signal processing unit 610, wherein the piston stroke length and speed are calculated or derived with high accuracy and low latency based on the sensor signal 630 as described herein. Using the speed and stroke signal 635, the compressor controller 615 can affect the swash plate angle adjustment signal 650 to increase or decrease the swash plate angle to achieve the desired compressor performance.
In the case where the external control signal 670 indicates a desired piston stroke length, the swash plate angle adjustment signal 650 is affected until the read piston stroke length corresponds to the requested piston stroke length. Where the external control signal 670 indicates a desired swash plate angle, the desired swash plate angle may be converted to a corresponding piston stroke length (or piston stroke length signal to swash plate angle) before comparing the actual and desired values.
In the case where the external control signal 670 indicates suction pressure or evaporator outlet air temperature, the compressor controller 615 may use the additional sensor signal 640 to generate the appropriate swash plate angle adjustment signal 650. The compressor controller may read additional sensor signals 640 including, for example, compressor and/or refrigeration cycle suction pressure and crankcase pressure, and compressor speed.
In the event that the external control signal 67 indicates a desired compressor mass flow, then an adjustment to the current compressor mass flow may be calculated from the piston speed, the piston stroke length, and/or additional sensor signals 640 (e.g., the suction pressure signal and/or the evaporator pressure signal).
The HVAC unit 620 may receive an HVAC input signal 670 (such as an indication of a current suction pressure, an evaporator outlet air temperature, a compressor torque, a compressor speed, and/or a cabin air temperature) to generate a compressor control signal 660. The signal values may be measured directly or calculated and/or estimated from the signal values. The HVAC may be a separate processing unit (e.g., an HVAC ECU), may be part of an engine processing unit (e.g., an engine ECU), or may be part of another vehicle processor unit.
The compressor controller 615 may be located with the HVAC unit 620, as a module of the HVAC unit 620, or in any other suitable location. The compressor controller 615 may be physically part of the compressor 605 or separate but operatively connected to the compressor.
The signal processing unit 610 may be located on the compressor 605, where the compressor controller 615 (e.g., integrated in the compressor controller 615) is a module of the compressor controller 615, or separate but operatively connected to the compressor and/or the compressor controller 615 and/or the HVAC unit 620. The signal processing unit 610 may be part of (e.g., integrated in) the sensor housing. The processing unit may also be integrated into the HVAC unit.
Reference numerals
100 variable displacement compressor
110 piston
120 swash plate
125 swash plate angle
130 transducer probe
135 sensor coil
140 primary target
150 calibration target
160 compressor shell
170 reduced stroke length
180 increased stroke length
210 resonant current
220 FM demodulation
230 signal evaluation and/or conversion circuit
240 piston stroke length
250 piston stroke speed
260 piston stroke length linearization
270 linearization of piston stroke velocity
305 optional demodulation step
310 receive a first signal
320 determine periodicity
330 determining the duty cycle
340 generate speed and stroke signals
410 first time stamp
420 second time stamp
430 target does not exist
440 target present
450 processed sensor signal
460 resonant signal
510 solid lines; low stroke length
520 dot-dash line; length of middle stroke
530 dashed lines; high stroke length
540 target position
570 calibration target position
605 compressor
610 signal processing unit
615 compressor controller
620 Heating Ventilation and Air Conditioning (HVAC) system
630 sensor signal
635 speed and Stroke Signal
640 additional sensor signal
650 swash plate angle adjusting signal
660 compressor control signal
670 HVAC input signal
680 angular speed of rotor
710 frequency at Top Dead Center (TDC)
720 piston pass calibration target
730 frequency at Bottom Dead Center (BDC)
- 上一篇：一种医用注射器针头装配设备
- 下一篇：混凝土泵送系统、混凝土泵送设备和控制方法