PXE compressor

Anonymous on Mon May 10, 2004 2:53 AM

Help!!! Any idea what is Sanden PXE compressor? Is it the latest model? How reliable is it? Anyone has any details?

Mamamia on Mon May 10, 2004 11:15 PM

me too! I have come across an enquiry for PXE sanden compressor recently but still have no idea what or how this compressor looks like or how well it performs. Anyone any idea? Will be greatful for that.

DetroitAC on Tue May 11, 2004 7:12 PM

It's a variable displacement piston/swashplate compressor. Clutchless and externally controlled (displacement controlled via an electrical signal). I think to date it is only in production on some high end Audi cars like the A8. It performs...just like a fixed piston pump when it's in full displacement. Reliability information, as with any new equipment will be many years in the future.

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Mamamia on Wed May 12, 2004 1:27 AM

cool!!! thanks a million! That information is really useful.

Mamamia on Wed May 12, 2004 1:52 AM

Sorry, two more questions. Would you have any idea if the seal and control valve is the same as PXV compressor? Where can I get the seal and control valve?

ice-n-tropics on Thu May 13, 2004 4:49 PM

European OEMs place a high priority on drive ability for small cars. The PXE's improved drive ability features are AC decrease (but not off) during rapid acceleration, "soft start" for low AC load during starting and elimination of the following: cycling, refrigerator defrost smell, unnecessary louver temperature swings, engagement torque spikes that result in car rock and jerk and clutch armature engagement clap noise.

In early 2003 Sanden launched the PXE (E for external control) for the VW Golf V, and VW Polo. The PXE uses a variable angle swash plate which functions as a cam to convert rotary shaft motion into the axial motion of the pistons located on one side of the swash plate. The swash plate inclination angle or stroke and subsequent AC performance is controlled by an electrical signal from an analysis of ambient, interior temp, engine rpm ect.

A control device in the PXE regulates the flow of gas from the discharge pressure side (Pd) to the crankcase pressure (Pc) in response to a pulse width modulated (PWM) electrical current. The control device consists of a valve who's position is a result of the force relationship of a variable solenoid acting against a suction pressure bellows or release spring.

Maximum stroke:
A higher control current to the PXE's control valve solenoid causes the valve to close the passage of Pd into the crankcase. A variable orifice allows blow-by gas past the piston rings to flow into the suction chamber. Pc approaches the same psi as the suction pressure (Ps). As the Ps and Pc come closer to the same value, the average gas pressure forces on the top and bottom of the pistons approach the same value and the swash plate inclination angle increases to the maximum setting. Optimum temperatere pulldown is the target. The result of high current is the longest stroke and maximum swept volume, higher horsepower requirement and increase of refrigerant mass flow and KWs or BTUs of cooling capacity.

Modulated stroke control:
The control valve has a bellows which senses suction pressure. The change in capacity is achieved by the bellows adjusting the flow of Pd gas into the crankcase. A change in the PWM value of current to the solenoid varies the force on the plunger in the valve. This modifies the set point controlled by the bellows. A wide range of inclination angles can thus be achieved to control AC performance. Comfortable interior temperatures are achieved based on operator settings and evaporator freeze up is avoided.

Minimum stroke or near off:
With the solenoid current off, the release spring force (opposed to the solenoid force) opens the valve and the correct amount of Pd flows into the crankcase. Regardless of Ps, the inclination angle is forced to minimum. Hence, safe acceleration becomes a higher priority than the cooling need as indicated by the Ps.This allows "soft start", optimum power for car acceleration and prevention of evaporator freezing.

The compressor shaft turns whenever the engine is running either summer or winter so no electromagnetic clutch is required. Clutch failure becomes a non issue. The compressor pulley has a built in torque limiter mechanism to prevent drive belt loss if the compressor has internal seizure. After the torque limiter slips there is only low torque drag and low noise.

The 100% continuous movement of internal compressor components even at low refrigerant mass flow presents special AC system design considerations. It becomes necessary to always return oil to the compressor for lubrication of continuously moving parts. This is normally accomplished by the use of a cross charged thermal expansion valve (TXV). The cross charge consists of two types of refrigerant in the sensing element of the TXV that are formulated to provide conventional superheat control at normal conditions. When the TXV modulates near the closed position and refrigerant mass flow is small, the superheat switches from positive (e.g., 8 deg.) to negative. Thereby, return of refrigerant with entrapped oil to the compressor is assured.

The PXE capacity control valve is different from the Sanden clutch equipped model SDV (variable stroke nutating wobble plate compressor). The SDV control valve called Mass Flow Control Valve (MFCV) operates only on internal pressure signals from Ps and Pd and not an external electrical signal. Basically the SDV utilizes Ps as a indicator of cooling need with some Pd influence. The use of a Pd signal is based on the logic that if Pd is high the occupants are not yet cooled sufficiently and destroking should be counteracted.

Also, the PXE features a longer life double lip shaft seal. The seal incorporates a shallow spiral slit for several revolutions on the inner surface of the PTFE (outer lip) which extends the hours of running time before the shaft seal leaks.

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Mamamia on Mon May 17, 2004 2:33 AM

Thanks Mr Davis. Any idea where I can get a sample or 1pce PXE compressor? Need this compressor urgently.

ice-n-tropics on Wed May 19, 2004 9:40 AM

What is your application for PXE?
The PXE is not on the road yet in the USA, but should be available in VW service in Germany. The PQ24 Polo platform uses mostly Denso and fewer Sanden PXE 13 127 cc). The PQ35 Golf Platform uses PXE 16 (162 cc).

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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
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Mamamia on Wed May 19, 2004 11:12 PM

Thanks for everyone's help and tips. they are all very useful Dont you think so Anonymous? I managed to solve my problems with their help. How bout you?

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