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 2014 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:/www.sae.org/technical/standards/ARP4940AEROSPACERECOMMENDED PRACTICEARP4940 Issued 2014-07 Application Guide for
5、Aerospace Hydraulic Motors RATIONALE There is a need for a document to provide guidance to aerospace engineers for understanding and characterizing hydraulic motors for a variety of high speed/high performance aerospace applications. This document provides information that supplements and can be use
6、d with accepted industry specifications. TABLE OF CONTENTS 1. SCOPE 31.1 Purpose . 32. REFERENCES 32.1 Applicable Documents 32.1.1 SAE Publications . 32.2 Definitions . 33. MOTOR DESIGNS 43.1 Fixed Displacement Motors 43.1.1 Design . 43.1.2 Performance Characteristics . 43.2 Variable Displacement Mo
7、tors 43.2.1 Design . 43.2.2 Performance Characteristics . 54. OPERATIONAL CHARACTERISTICS . 64.1 System Architecture 64.2 System Integration Considerations . 74.2.1 Load Inertia . 74.2.2 Starting Conditions 74.2.3 Stopping Conditions 74.3 Motor Efficiency . 84.3.1 Mechanical Efficiency 84.3.2 Volume
8、tric Efficiency . 94.4 Overspeed . 94.5 Pumping Mode 94.6 Types of Controls 104.6.1 Capabilities Definition 104.6.2 Fixed Displacement . 104.6.3 Variable displacement control . 14SAE INTERNATIONAL ARP4940 Page 2 of 22 5. MOTOR APPLICATIONS 175.1 Secondary Flight Control Drives . 175.2 Hoist and Winc
9、h Drives . 175.3 Small turbine (APU) Starters . 185.4 Large Turbine Starters 185.5 Generator Drives . 185.6 Power Transfer Units 185.7 Fuel Pump Drives 185.8 Gatling Gun Drive Systems . 185.9 Turret Drive Systems 195.10 Utility Systems . 196. NOTES 19APPENDIX A GENERAL DESIGN CONSIDERATIONS . 20FIGU
10、RE 1 OVER-CENTER VARIABLE DISPLACEMENT MOTOR 5FIGURE 2 TORQUE (EXAMPLE) OUTPUT VERSUS DISPLACEMENT, CONTINUOUS ROTATION . 5FIGURE 3 TORQUE OUTPUT VERSUS DISPLACEMENT, STARTING (EXAMPLE) . 6FIGURE 4 EXAMPLES OF CLOSED AND OPEN LOOP HYDRAULIC SYSTEM ARCHITECTURES 7FIGURE 5 TORQUE LOSS VERSUS SPEED - T
11、YPICAL . 8FIGURE 6 BASIC ON-OFF CONTROL FOR UNIDIRECTIONAL FIXED DISPLACEMENT MOTOR 11FIGURE 7 FLOW CONTROL CONCEPTS FOR FIXED DISPLACEMENT MOTORS 12FIGURE 8 BASIC ON-OFF CONTROL WITH FLOW CONTROL AND ANTI-CAVITATION CHECK . 12FIGURE 9 TYPICAL FIXED DISPLACEMENT BI-DIRECTIONAL CONTROL 13FIGURE 10 SP
12、EED CONTROL USING HYDROSTAT 14FIGURE 11 FIXED DISPLACEMENT ELECTROHYDRAULIC SERVOMOTOR 14FIGURE 12 DUAL-DISPLACEMENT MOTOR CONTROL 15FIGURE 13 PRESSURE COMPENSATED VARIABLE MOTOR CONTROL (EXAMPLE) . 16FIGURE 14 VARIABLE DISPLACEMENT ELECTROHYDRAULIC SERVO CONTROL 17SAE INTERNATIONAL ARP4940 Page 3 o
13、f 22 1. SCOPE This SAE Aerospace Recommended Practice (ARP) is an application guide for fixed and variable displacement hydraulic motors. It provides details of the characteristics of fixed and variable displacement hydraulic motors, architectures, circuitdesigns, controls, and typical applications.
14、 The applications include airborne and defense vehicles with emphasis on high performance applications. 1.1 Purpose The purpose of this document is to apprise the system designer of the available options in the control and application of hydraulic motors and it provides guidance in how to integrate
15、them in a control system. 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 of the purcha
16、se 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 Publications Available
17、from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.AS595 Aerospace - Civil Type Variable Delivery, Pressure Compensated, Hydraulic Pump ARP1280 Aerospace - Application Guide for Hydraulic Pow
18、er Transfer Units ARP1383 Aerospace - Impulse Testing of Hydraulic Components AIR1899 Aerospace Military Aircraft Hydraulic System Characteristics ARP4386 Terminology and Definitions for Aerospace Fluid Power, Actuation and Control Technologies AIR5005 Aerospace - Commercial Aircraft Hydraulic Syste
19、ms AS7997 Motors, Aircraft Hydraulic, Constant Displacement - General Specification For AS19692 Pumps, Hydraulic, Variable Flow, General Specification For 2.2 Definitions Refer to ARP4386 for terms that are generally used in this document. High speed applications, in the context of hydraulic motors
20、as discussed in this document, are those where speeds are approaching or exceeding the typical rated speeds for pumps of similar displacements as defined in AS595 and AS19692. High performance applications, in the context of hydraulic motors as discussed in this document, are those where rapid chang
21、es of speed occur in a cyclic manner during the life of the motor. Windage is defined as the mechanical torque required to overcome the resistance of the rotating group of a hydraulic pump or motor due to the hydraulic fluid surrounding the rotating group. The torque is a function of rotational spee
22、d. SAE INTERNATIONAL ARP4940 Page 4 of 22 3. MOTOR DESIGNS Refer to Appendix A for design parameters and specification guidelines for hydraulic motors. 3.1 Fixed Displacement Motors 3.1.1 Design Fixed displacement motors designs include diverse technologies such as piston, vane and gear types. For h
23、igh pressure applications, piston motors are generally used. The common piston motor designs are axial piston inline and bent axis types. Inline designs are simpler, lighter and typically are lower cost. The bent axis designs have lower mechanical and volumetric losses, and have better break-out and
24、 low speed characteristics 3.1.2 Performance Characteristics The displacement of a fixed displacement motor is selected to provide the necessary torque required by the application, by considering that the theoretical torque is the product of displacement and differential (inlet - outlet) pressure. O
25、nce the displacement is selected, the theoretical flow required to operate the motor at the required speed is the product of displacement and speed. Output speed is a function of input flow less volumetric losses, which are typically pressure dependent. The losses include internal leakage around the
26、 pistons and under the cylinder block/barrel and piston shoes or other piston linkages. Since the losses are pressure, not speed dependent, the volumetric efficiency increases with speed. Output torque losses result from friction and windage, and are speed and pressure dependent. At higher speeds, w
27、indage is a dominant factor. At break-out, torque efficiency is usually lower than at moderate speeds, then decrease at higher speeds. 3.2 Variable Displacement Motors 3.2.1 Design Refer to Figure 1. Variable displacement motors are controlled by a swash plate, whose angle is controlled to vary the
28、displacement of the motor. Displacement is generally a function of the tangent of the swash plate angle. They lend themselves most readily to variable displacement adaptation for both uni-directional and bi-directional application. For uni-directional applications, such as a generator drive, the swa
29、sh angle varies from zero to maximum in one direction only. For bi-directional applications the displacement varies from positive to negative passing through the zero displacement position. These implementations are called “overcenter”, because the swash angle crosses the center on zero-displacement
30、 point. It is important to note that in overcenter motors, the Inlet (high pressure) and Return (low pressure) ports always remain unchanged regardless of direction of rotation - the direction is determined by the swash plate position on either side of center. SAE INTERNATIONAL ARP4940 Page 5 of 22
31、FIGURE 1 - OVER-CENTER VARIABLE DISPLACEMENT MOTOR 3.2.2 Performance Characteristics 3.2.2.1 Torque Output - Continuous rotation Refer to Figure 2 for a typical example. When the motor is running, the torque output is directly proportional to displacement with an offset to balance losses. This offse
32、t increases with speed. The torque characteristic is continuous through null as long as the direction of rotation does not change. FIGURE 2 - TORQUE (EXAMPLE) OUTPUT VERSUS DISPLACEMENT, CONTINUOUS ROTATION r15r10r50510r100 r50 0 50 100TORQUEDISPLACEMENTTORQUEOUTPUTr CONTINUOUSROTATIONREVERSEFLOWSAE
33、 INTERNATIONAL ARP4940 Page 6 of 22 3.2.2.2 Torque Output - Starting Refer to Figure 3 for a typical example. When starting the motor, there is a discontinuity as the motor requires approximately 30% displacement to start even against low loads. This should be considered in the control system design
34、. FIGURE 3 - TORQUE OUTPUT VERSUS DISPLACEMENT, STARTING (EXAMPLE) 3.2.2.3 Reverse Flow When rotating in one direction and braking is required, displacement in the opposite direction is commanded. This will reverse the flow direction. This means the unit will operate as a pump drawing flow from the
35、low pressure port and discharging it into the high pressure port, creating the braking torque. The hydraulic system should be designed to accommodate this, i.e., the main system should allow this or provisions around the motor should allow it. If the braking energy is small this can be done with cro
36、ss port relief valves. In the case of a hoist, which could have longer periods of operation with negative loads, this may not be possible. 4. OPERATIONAL CHARACTERISTICS 4.1 System Architecture Refer to Figures 4 (i) and 4(ii). Hydraulic motors and the loads that they drive can be integrated in eith
37、er open loop or closed loop architectures. This refers to the method the motors are connected to the hydraulic sources, not the scheme that is used to control the motors and their loads. In conventional “open loop” or “central” hydraulic systems, as shown in Figure 4 (i), one or more pumps pressuriz
38、e a common hydraulic trunk line, to which multiple consumers are connected. In this manner, consumers can be linear actuators and/or motor driven actuators, with each consumer extracting power from the central system independently, but not to exceed the total power available. Such a system architect
39、ure is used for powering flight controls, landing gear, brakes and utility systems such as winches, hoists, doors, and special mission related equipment. An alternate architecture is the “closed loop” system, as shown in Figure 4 (ii), where a pump is directly connected to, and dedicated to a single
40、 consumer, and the pump and consumer are controlled simultaneously to achieve the desired torque and speed output. These systems are rare on aircraft applications, but may be found on afterburner exhaust nozzle controls, propeller pitch controls and remotely located doors and winches. 02468101234567
41、89101TORQUEDISPLACEMENTTORQUEATSTARTSAE INTERNATIONAL ARP4940 Page 7 of 22 FIGURE 4 - EXAMPLES OF CLOSED AND OPEN LOOP HYDRAULIC SYSTEM ARCHITECTURES 4.2 System Integration Considerations The integration of the motor into the actuation and hydraulic systems should take into account the nature of the
42、 load, the type of control desired, and the characteristics of the hydraulic system which provides power to the actuator. In particular, the following system parameters should be considered: 4.2.1 Load Inertia The total load inertia, including that of the motor itself, and acceleration rates have a
43、significant influence on system design. 4.2.2 Starting Conditions The following are the important considerations during the start phase of motor operation: x The rate of opening of the supply control valve x The load inertia and drive train stiffness If the control valve opens rapidly and the load i
44、nertia is high in relation to the drivetrain stiffness it is possible that an oscillation of the drivetrain will ensue. The analysis of this potential problem would normally be the responsibility of the system designer but the motor supplier should be aware of the problem as it could cause load reve
45、rsals inside the motor which could be damaging to the motor. Another effect which could be damaging is cavitation in the inlet line as a result of the preceding shut down. If the inlet lineis essentially empty at the time of start valve opening the resulting rush of fluid to fill the void could caus
46、e a water hammer effect potentially causing damage to the motor or drivetrain. 4.2.3 Stopping Conditions Stopping a motor requires careful consideration. Due to the inertia of the motor (and load), closing a valve while the motor is running may impose high pressure requiring installation of cross po
47、rt relief valves or special anti-cavitation valves. Thisis to prevent water hammer effects occurring due to a rapid stop, which could cause a pressure spike in either the supply line, the motor outlet port or both. When the motor decelerates over a relief valve, a bypass is required to provide inlet
48、 to the motor from a low pressure source. If a high inertia load is controlled, recirculating the fluid in a relief/inlet loop will cause local heating of the fluid, with the possibility of damage to the motor and fluid; in this case, a replenishing system is required to provide fresh oil to the motor inlet during deceleration. SAE INTERNATIONAL ARP4940 Page 8 of 22 If the motor is brought to a stop by restricting the inlet and outlet flow, cavitation could be caused at the inlet port which will reduce or eliminate the braking effe
