SAE AIR 5872A-2017 Aerospace Hydraulic Pump Controls.pdf

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1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there

2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2017 SAE International All rights reserved. No part of this p

3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497

4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/AIR5872A AEROSPACE INFORMATION REPORT AIR5872 REV. A Issued 2011-10 Revised 2017-05 Superseding

5、 AIR5872 Aerospace Hydraulic Pump Controls RATIONALE The document has been revised to incorporate a new section describing an anti-stall speed control system, and clarifications to other sections. TABLE OF CONTENTS 1. SCOPE 3 1.1 Purpose . 3 1.2 Field of Application 3 2. REFERENCES 3 2.1 Applicable

6、Documents 3 2.1.1 SAE Publications . 3 2.1.2 ISO Publications 4 3. OVERVIEW OF PUMP CONTROLS 4 3.1 Definition . 4 3.1.1 Aerospace Type Controls 4 3.1.2 Classifications . 4 4. DESCRIPTION OF CONTROLS 4 4.1 Fixed Versus Variable Displacement Pumps 4 4.1.1 Introduction . 4 4.1.2 Concept Description 5 4

7、.1.3 Examples and Limitations of Usage 7 4.2 Pressure Controls for Variable Displacement Pumps . 8 4.2.1 Overview of Pressure Controls . 8 4.2.2 Flat Cut-Off Pressure Compensator Control . 9 4.2.3 Soft Pressure Cutoff Control . 12 4.2.4 Dual Range Pressure Control . 14 4.3 Torque Limiting, Unloading

8、 and Blocking Controls . 16 4.3.1 Overview . 16 4.3.2 Electrical Depressurization Valve (EDV) Control 16 4.3.3 Torque (Power) Limiting 18 4.3.4 Starting Torque Reduction Control . 20 4.3.5 Clutches 23 4.3.6 Anti-Stall Speed Control System . 23 SAE INTERNATIONAL AIR5872A Page 2 of 25 5. NOTES 25 5.1

9、Revision Indicator 25 Figure 1 Fixed Displacement Pump Characteristics Below Rated Flow . 5 Figure 2 Fixed Displacement Pump Characteristics Below Relief Pressure 6 Figure 3 Characteristics of a Variable Displacement Pump 7 Figure 4 Typical Performance Characteristic - Flat Cut-Off 10 Figure 5 Typic

10、al Cross-Section View Flat Cut-Off 11 Figure 6 Schematic - Flat Cut-Off 11 Figure 7 Typical Performance Characteristic Soft Cut-Off . 13 Figure 8 Schematic - Soft Cut-Off . 13 Figure 9 Typical Performance Characteristic - Dual Range Pressure Control . 14 Figure 10 Schematic - Dual Range Pressure Con

11、trol . 15 Figure 11 Typical Performance - EDV Pump Control . 16 Figure 12 Schematic - Typical EDV Control 18 Figure 13 Typical Performance - Power Limiting Control 19 Figure 14 Schematic - Power Limiting Control 19 Figure 15 Electric Motor Torque - Speed Characteristic . 21 Figure 16 Schematic - Sta

12、rt Valve Control 22 Figure 17 Anti-Stall Speed Control Performance 23 Figure 18 Anti-Stall Speed Control 24 SAE INTERNATIONAL AIR5872A Page 3 of 25 1. SCOPE This SAE Aerospace Information Report (AIR) presents an overview of the application and control of fixed and variable displacement pumps with t

13、he emphasis on the controls most commonly used on variable displacement pumps. It describes various options to control the operation of hydraulic pumps in terms of controlling the pump output pressure and/or flow and assisting in the selection of the pump. 1.1 Purpose The information contained herei

14、n is intended to provide application information to assist system integrators in selecting the most appropriate pump controls for a given application. It can also be used as an introduction to pump designers. 1.2 Field of Application The controls described are applicable to hydraulic pumps installed

15、 on commercial and military aerospace applications. Additional details relating to design and performance characteristics of pumps in various aerospace applications are provided in the following documents: a. AS595 provides additional information on civilian aircraft pumps b. ISO8278 provides additi

16、onal information on civilian and military aircraft pumps c. AS19692 and AIR560 provide additional information oriented toward general military and missile pumps, respectively d. ISO22089 and ARP1280 provide additional information for controlling power transfer units e. AS5994 provides additional inf

17、ormation on electric motor driven pumps 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date

18、 of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 SAE Publicati

19、ons Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org. AIR560 Missile Hydraulic Pumps ARP1280 Aerospace - Application Guide for Hydraulic Power Transfer Units AS595 Aerospace Ci

20、vil Type Variable Delivery, Pressure Compensated, Hydraulic Pump AS5994 Pump Units, Hydraulic, Electric Motor Driven, Variable Delivery AS19692 Aerospace Military Type Variable Delivery, Pressure Compensated Hydraulic Pump SAE INTERNATIONAL AIR5872A Page 4 of 25 2.1.2 ISO Publications Copies of thes

21、e documents are available online at http:/webstore.ansi.org/ ISO8278 Hydraulic pressure compensated, variable delivery pumps-General requirements ISO22089 Aerospace - Hydraulic power transfer units - General specifications 3. OVERVIEW OF PUMP CONTROLS 3.1 Definition Hydraulic pump controls are devic

22、es used to dynamically control the displacement of variable displacement pumps in a predictable and repeatable way. Typically, the intent is to control parameters such as pressure, flow, input starting or running torque and any combination thereof, since in some cases the system requirements may be

23、fulfilled by combining two or more of these control schemes. 3.1.1 Aerospace Type Controls These controls differ from Industrial and Mobile controls due to the particularities of aerospace applications that demand fast response and light weight. They are usually integrated within the pump body to in

24、crease reliability and reduce weight and external leakage. Aerospace hydraulic systems differ from industrial and mobile systems in that they are more compact, have less volume and utilize smaller line sizes thereby experiencing greater pressure drops and surges, and have smaller reservoir volumes m

25、aking heat rejection more challenging. These factors make aerospace type controls somewhat different in implementation from their industrial and mobile counterparts, although in principle they are similar. 3.1.2 Classifications Generally, aerospace pump controls can be classified into the following

26、categories, although there are many overlapping combinations possible to fit more demanding applications: Pressure limiting controls Torque (power) limiting, unloading and blocking controls Thermal controls Adaptive controls Multi-function controls The control types listed above include both hydrome

27、chanical and electrical technology, and also touch on industrial controls that may, in some instances, find application in an aerospace environment. 4. DESCRIPTION OF CONTROLS 4.1 Fixed Versus Variable Displacement Pumps 4.1.1 Introduction Fixed displacement pumps provide flow that is directly propo

28、rtional to its speed of rotation, the ratio being the displacement of the pump expressed as a volume per revolution. Variable displacement pumps are capable of varying their displacements in response to some control mechanism. Applying various control schemes to this variable displacement mechanism

29、to achieve different control characteristics is the subject of this report. A brief introduction to fixed displacement pumps is offered to illustrate some factors that may make a fixed displacement pump more suited to a particular application as opposed to a variable displacement model. SAE INTERNAT

30、IONAL AIR5872A Page 5 of 25 4.1.2 Concept Description 4.1.2.1 Fixed Displacement Pump For a given input speed, a fixed displacement pump delivers a fixed flow, as depicted by the Pump Flow line in Figure 1. As long as the system loads can use this amount of pump flow, then the operating point lies o

31、n this line, at a point corresponding to the pressure demanded by the loads. In many instances, however, the loads attached to the pump are controlled by valving that limit their flow demand to a value less than the pump flow, as depicted by the Load Flow line. Point 1 on the chart corresponds to su

32、ch a condition, where the Required Pressure includes the pressure demanded by the load plus the total pressure drop in the pressure and return lines between the pump to the load control valve. Because the load is not demanding all of the available pump flow, the pump is constrained to operate at poi

33、nt 2, passing the Relief Valve Flow across the relief valve at the pressure determined by the Relief Valve Setting. Consequently, area B represents the power loss in the load control valve to maintain the required flow and pressure in the load and area C represents the power loss in the relief valve

34、 to bypass the flow not needed by the load but supplied by the pump. The sum of areas B and C represent the total power loss in the system that is converted to heat, as depicted by the shaded area in Figure 1. The schematic at the right of Figure 1 illustrates the flow path described above. Figure 1

35、 - Fixed displacement pump characteristics below rated flow Fixed displacement pumps were used years before variable pumps were invented and were used successfully in specific applications. It is still possible to take advantage of the simple design of fixed displacement pumps by using them in appli

36、cations where they can operate on the Pump Flow line below point 2, thereby not wasting power as described above. In such a case, the operating point 1 is located on the Pump Flow line as depicted in Figure 2 and the required pressure in the load is less than the relief setting, depicted as point 2.

37、 Note that as long as the operating point 1 is below point 2 on the Pump Flow line, all of the pump flow is passing through the load at the required load pressure and none of the flow is passing through the relief valve; consequently, the power loss described in Figure 1 is not present. PRESSUREF L

38、O WR E L I E F V A L V E S E T T I N GREQUIREDPRESSUREL O A D F L O WPUMPFLOWU S E F U L P O W E R R E L I E F V A L V E F L O WCONTROLVALVEPRESSUREDROPACB12L I N E S O F C O N S T A N T P O W E RSAE INTERNATIONAL AIR5872A Page 6 of 25 Figure 2 - Fixed displacement pump characteristics below relief

39、pressure The scenario described above is illustrated by the following application examples: a. For systems that only require moving an actuator intermittently at maximum speed, the pump can be coupled to an electric motor which can be started and stopped as required. In this case, the operating poin

40、t is on the Pump Flow line below point 2, and may jump to point 2 momentarily if the load actuator bottoms, at which time an external pressure signal stops the motor. b. For systems where the function of the pump is to charge an accumulator and hence the accumulator provides flow as needed to the sy

41、stem, an unloading valve (also known as a “cut-in cut-out” valve) can be provided downstream of the pump. This valve allows the pump to fill the accumulator at the pumps full flow until the preset pressure is reached, at which time the valve shifts to a bypass position where the full pump flow is di

42、rected at low pressure back to the reservoir. A check valve integral with the unloading valve maintains pressure in the accumulator and the system downstream. As the system consumes the high pressure fluid from the accumulator, the low pressure preset is reached and the unloading valve shifts back t

43、o the accumulator charging position and the accumulator charging cycle repeats. In this type of application, the operating point is near the bottom of the Pump Flow line (near zero pressure) when the valve is bypassing, and higher up the line when the accumulator is charging, but is designed to rema

44、in below point 2 at all times. The unloading valve can be actuated either hydraulically by pilot pressure from the system or electrically by a signal from a pressure switch. This implementation is common in systems where precise regulation of system pressure is not needed, but is allowed to vary fro

45、m maximum to a lower preset minimum level. c. For electric motor driven pumps where an electric motor with sufficient dynamic bandwidth is used to vary pump speed using digital controls so as to achieve the desired pressure / flow characteristic. These types of electric motor pumps are used in the c

46、ontrol of Electro Hydrostatic Actuators (EHA) and in system back up pump applications (for example, A380 braking and steering systems). The variable speed motor controls used in these applications are not covered in this report. In this type of application, the operating point moves up and down the

47、Pump Flow line dynamically, but is designed to always remain below point 2 so as not to allow flow through the relief valve. Fixed displacement pumps are very compact, have in fact no internal control, since all controls for the system are done outside the pump. They can achieve very high power dens

48、ity, power to weight ratio. They can also be integrated at higher sub-assembly level by the next level integrator; they can be located at the point of usage when driven by electric motors at variable speed. PRESSUREF L O WR E L I E F V A L V E S E T T I N GREQUIREDPRESSUREL O A D F L O WPUMPFLOWU S

49、E F U L P O W E R A21L I N E S O F C O N S T A N T P O W E RSAE INTERNATIONAL AIR5872A Page 7 of 25 4.1.2.2 Variable Displacement Pump The advantage of the variable displacement pump is that it can operate at any flow, from zero to its maximum capacity. Assuming the conditions from the fixed pump example of Figure 1, the operating point 1 is again shown in Figure 3. Since the variable pump can match its output flow to