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 theref
2、rom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2011 SAE International All rights reserved. No part of this publication ma
3、y 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: +1 724-776-4970 (outside US
4、A) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR5872AEROSPACEINFORMATIONREPORTAIR5872 Issued 2011-10Aerospace Hydraulic Pump Controls RATION
5、ALEThere is a need for a document that provides aerospace hydraulic system and pump designers the various options for controlling the operation of hydraulic pumps, thereby helping in the selection of the most suitable pump for their systems. This document satisfies this need.TABLE OF CONTENTS 1. SCO
6、PE 31.1 Purpose . 31.2 Field Of Application . 32. REFERENCES 32.1 Applicable Documents 32.1.1 SAE Publications . 32.1.2 ISO Publications 43. OVERVIEW OF PUMP CONTROLS 43.1 Definition . 43.1.1 Aerospace Type Controls . 43.1.2 Classifications . 44. DESCRIPTION OF CONTROLS 44.1 Fixed Versus Variable Di
7、splacement Pumps 44.1.1 Introduction . 44.1.2 Concept Description 54.1.3 Examples and Limitations of Usage . 74.2 Pressure Controls for Variable Displacement Pumps 84.2.1 Overview Of Pressure Controls 84.2.2 Flat Cut-Off Pressure Compensator Control . 94.2.3 Soft Pressure Cutoff Control . 114.2.4 Du
8、al Range Pressure Control . 134.3 Torque Limiting, Unloading and Blocking Controls . 154.3.1 Overview . 154.3.2 Electrical Depressurization Valve (EDV) Control 154.3.3 Torque (Power) Limiting 174.3.4 Starting Torque Reduction Control . 194.3.5 Clutches 225. NOTES 225.1 Revision Indicators 22Copyrigh
9、t SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5872 Page 2 of 22 FIGURE 1 FIXED DISPLACEMENT PUMP CHARACTERISTICS BELOW RATED FLOW . 5FIGURE 2 FIXED DISPLACEMENT PUMP CHARACTERISTICS BELOW RELIEF PRE
10、SSRE 6FIGURE 3 CHARACTERISTICS OF A VARIABLE DISPLACEMENT PUMP . 7FIGURE 4 TYPICAL PERFORMANCE CHARACTERISTIC FLAT CUT-OFF . 9FIGURE 5 TYPICAL CROSS-SECTION VIEW FLAT CUT-OFF 10FIGURE 6 SCHEMATIC FLAT CUT-OFF . 11FIGURE 7 TYPICAL PERFORMANCE CHARACTERISTIC SOFT CUT-OFF. 12FIGURE 8 SCHEMATIC SOFT CUT
11、-OFF 13FIGURE 9 TYPICAL PERFORMANCE CHARACTERISTIC DUAL RANGE PRESSURE CONTROL 14FIGURE 10 SCHEMATIC DUAL RANGE PRESSURE CONTROL 15FIGURE 11 TYPICAL PERFORMANCE - EDV PUMP CONTROL . 16FIGURE 12 SCHEMATIC - TYPICAL EDV CONTROL . 17FIGURE 13 TYPICAL PERFORMANCE - POWER LIMITING CONTROL 18FIGURE 14 SCH
12、EMATIC - POWER LIMITING CONTROL . 18FIGURE 15 ELECTRIC MOTOR TORQUE SPEED CHARACTERISTIC 20FIGURE 16 SCHEMATIC - START VALVE CONTROL 21Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5872 Page
13、 3 of 22 1. SCOPE This Aerospace Information Report presents an overview of the application and control of fixed and variable displacement pumps with the emphasis on the controls most commonly used on variable displacement pumps. It describes various options to control the operation of hydraulic pum
14、ps 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 herein is intended to provide application information to assist system integrators in selecting the most appropriate pump controls for a given application
15、. 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 on commercial and military aerospace applications.Additional details relating to design and performance characteristics of pumps in various aerospac
16、e applications are provided in the following documents:a. AS595 provides additional information on civilian aircraft pumps b. ISO8278 provides additional information on civilian and military aircraft pumps c. AS19692 and ARP560 provide additional information oriented toward general military and miss
17、ile pumps, respectively d. ISO22089 and ARP1280 provide additional information for controlling power transfer units e. AS5994 provides additional information on electric motor driven pumps 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent sp
18、ecified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date 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 precede
19、nce. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1.1 SAE Publications Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Telephone: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA
20、), Web address: http:/www.sae.org.AS595 Pump, Hydraulic, Civil Type Aircraft and Variable Delivery ARP560 Pumps, Missile Hydraulic ARP1280 Application guide for fixed displacement Aircraft Power Transfer Units. AS5994 Pump, Hydraulic, Electric-Motor-Driven, Variable Delivery AS19692 Pumps, Hydraulic
21、, Variable Delivery, General Specification forCopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5872 Page 4 of 22 2.1.2 ISO Publications Available from American National Standards Institute, 25
22、West 43rd Street, New York, NY 10036-8002, Tel: 212-642-4900, www.ansi.org.ISO8278 Hydraulic pressure compensated, variable delivery pumps-General requirements 3. OVERVIEW OF PUMP CONTROLS 3.1 Definition Hydraulic pump controls are devices used to dynamically control the displacement of variable dis
23、placement 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 fulfilled by combining two or more of these control schemes.3.1
24、.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 increase reliability and reduce weight and external leakage. Aeros
25、pace 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 making heat rejection more challenging. These factors make aerosp
26、ace 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 categories, although there are many overlapping combinations pos
27、sible to fit more demanding applications:x Pressure limiting controls x Torque Limiting, Unloading and Blocking controls x Thermal controls x Adaptive controls x Multi-function controls The control types listed above include both hydromechanical and electrical technology, and also touch on industria
28、l 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 proportional to its speed of rotation, the ratio being the displacem
29、ent 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 to achieve different control characteristics is the subject of
30、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. Copyright SAE International Provided by IHS under license with SAENot for R
31、esaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5872 Page 5 of 22 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
32、loads can use this amount of pump flow, then the operating point lies on 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
33、 depicted by the Load Flow line. Point 1 on the chart corresponds to such 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 al
34、l of the available pump flow, the pump is constrained to operate at point 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 pressu
35、re in the load and area C represents the power loss in the relief valve 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. FIGURE 1 - FIXED DI
36、SPLACEMENT 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 applications whe
37、re 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. Note that
38、as long as the operating point 1 is below point 2 onthe 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. Copyright SAE Internation
39、al Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5872 Page 6 of 22 FIGURE 2 - FIXED DISPLACEMENT PUMP CHARACTERISTICS BELOW RELIEF PRESSRE The scenario described above is illustrated by the following application exampl
40、es: 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 point is on the Pump Flow line below point 2, and may jump to point 2 momentarily if the loa
41、d 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 system, an unloading valve (also known as a “cut-in cut-out” valve) can be provided downst
42、ream 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 directed at low pressure back to the reservoir. A check valve integral with the unloading
43、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 to the accumulator charging position and the accumulator charging cycle repeats.In this t
44、ype 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 remain below point 2 at all times. The unloading valve can be actuated either hydraulically b
45、y 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 from maximum to a lower preset minimum level. c. For electric motor driven pumps where an el
46、ectric 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 motorpumps are used in the control of Electro Hydrostatic Actuators (EHA) and in system back up pump applications (for
47、 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 Pump Flow line dynamically, but is designed to always remain below point 2 so as not to all
48、ow 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 density, 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. Copyright SAE International Provided
