Hidraulica Proporcional Festo

Proportional hydraulics Collection of Transparencies

095061 GB

Order no.: Designation: Description: Edition: Author: Graphics: Layout:

095061 PROP.H.FOLIEN D:OT-TP701-GB 10/2002 Dr. Frank Ebel Thomas Ocker, Bärbel Böhland 09.10.2002, Petra Schwarz, Wolfgang Schreiner

© Festo Didactic GmbH & Co., 73770 Denkendorf/Germany, 2002 Internet: www.festo.com/didactic e-mail: [email protected] The copying, distribution and utilization of this document as well as the communication of its contents to others without expressed authorization is prohibited. Offenders will be held liable for the payment of damages. All rights reserved, in particular the right to carry out patent, utility model or ornamental design registration.

Foreword

This set of overhead transparencies has been designed for the basic level technology package TP700. The set of overhead transparencies and the technology package form part of the Learning System for Automation and Technology from Festo Didactic GmbH & Co. The 28 overhead transparencies which comprise this set have been designed in accordance with dictactic and methodological principles. Each transparency is accompanied by a short explanatory text, which gives the instructor a brief overview of of the training content covered by the transparency. Training contents

• • • •

Fundamentals of proportional hydraulics Function and use of proportional hydraulic components Electronic components for the actuation of proportional valves Comparison with electro-hydraulic control systems

The text sheet includes a full illustration of the transparency, partly supplemented by additional explanations and designations, which can be added to the transparency by the instructor in the course of training. The advantages of this concept are: • The instructor can expand the transparencies step by step in the course of training • Lessons become more interesting • The available explanatory texts reduce the amount of preparation required by the instructor New! Electronic presentation

The enclosed CD-ROM contains the entire overhead transparencies and accompanying text of this edition in an electronically presentable form in the files „Prophydraulics_transparencies.pdf“ and „Prophydraulics_text.pdf“. In addition to the screen presentation, which can be made in any order, the contents can be printed out and text and graphics can be used for your own training preparations, insofar as the functionality of the required Adobe® Acrobat® Reader permits this. This freely distributable software is available on the CD-ROM in the currently valid English Windows version for installation in the directory „Acrobat_Reader“. Please start the file „*.exe“ and follow the subsequent dialogue.

© Festo Didactic GmbH & Co. • Proportional hydraulics

Contents

Proportional hydraulic system ________________________________Transparency 1 Mobile hydraulics __________________________________________Transparency 2 Proportional valve activation _________________________________Transparency 3 Honing machine ___________________________________________Transparency 4 Electro-hydraulics __________________________________________Transparency 5 Proportional hydraulics______________________________________Transparency 6 Electro-mechanical transducers _______________________________Transparency 7 D.C. switching solenoid______________________________________Transparency 8 Proportional solenoid with intermediate ring ____________________Transparency 9 Proportional solenoid, stroke-controlled_______________________Transparency 10 Proportional solenoid, force-controlled ________________________Transparency 11 Proportional solenoid, components___________________________Transparency 12 Electronic activation _______________________________________Transparency 13 Proportional amplifier ______________________________________Transparency 14 Ramp shaper _____________________________________________Transparency 15 Minimum current – Maximum current _________________________Transparency 16 Output stage (V/I converter) ________________________________Transparency 17 Pulse duration modulation __________________________________Transparency 18 Hysteresis _______________________________________________Transparency 19 Flow characteristic curves___________________________________Transparency 20 Control edge patterns ______________________________________Transparency 21 Piston opening ratio _______________________________________Transparency 22 Piston overlap ____________________________________________Transparency 23 Pressure relief valve, piloted ________________________________Transparency 24 Pressure regulating valve, piloted ____________________________Transparency 25 Flow control valve _________________________________________Transparency 26 4/3-way valve ____________________________________________Transparency 27 4/3-way valve, piloted _____________________________________Transparency 28

© Festo Didactic GmbH & Co. • Proportional hydraulics

1

Proportional hydraulics

Title

Proportional hydraulic system

Guide

• • • •

Signal input

Festo Didactic

Classification into signal control section and power section. Signal processing has been further enhanced by the provision of setpoint value and current signal conversion. The multiple function of proportional valves reduces the number of hydraulic components to a minimum. Proportional solenoids form the interface between the signal control section and the power section.

Actuators

Signal processing, control

Setpoint generator

Signal amplification

A

B Proportional valves

p

PLC

P

P

Power supply

701-01-GB

~

Power section

T

M

Power supply Power section


p

Festo Didactic

PLC

P Energieversorgung

~

Steuerteil

Proportional hydraulic system 701-01-GB

A

B

P

T

M

2


Title

Mobile hydraulics

Guide

• • • •

A

Festo Didactic

Origins of mobile hydraulics. Long hose connections between control valves and hydraulic drive components. Ratio of hand lever movement to piston deflection is approximately proportional. Control pattern: High-precision controllability at start of hand lever displacement, large flow rate change during hand lever movements at end deflection. In this instance, flow is not released until end deflection due to the positive piston overlap.

B

High-precision controllability

Piston B deflection

Flow rate [Q]

A

B Hand lever movement

Piston overlap A T

701-02-GB

B

P

A


Festo Didactic

High-precision controllability Piston B deflection

Flow rate [Q]

A

B Hand lever movement Piston overlap A

Mobile hydraulics 701-02-GB

3


Title

Proportional valve activation

Guide

• • •

Festo Didactic

Setpoint values are converted into magnetic flux and amplified. By means of the proportional solenoid, magnetic flux is converted into piston deflection within the hydraulic valve. Actuation of proportional directional, pressure and flow control valves.

Directional valves

Pressure valves

Proportional amplifier

Proportional solenoid

Flow control

701-03-GB


Festo Didactic

Proportional valve activation 701-03-GB

4


Title

Honing machine

Guide

• • •

Festo Didactic

Typical machine tool employing a proportional hydraulic control system. Continuous path control on machine tools: Controlling of path, speed and acceleration. Smooth transition of upward and downward stroke of honing machine in accordance with time function.

Cyl. stroke advanced 1

retracted 0

701-04-GB

Time


Festo Didactic

Cyl. stroke advanced 1

retracted 0

Time

Honing machine 701-04-GB

5


Title

Electro-hydraulics

Guide

• • • •

Festo Didactic

Example for conventional electro-hydraulics: Control of velocity stages. Use of parallel switching flow control valve for control of velocity stages. Digital switching characteristics: only preset flow rates can be invoked (example: flow control valve). Extensive hydraulic circuit requirement.

01

23

Cylinder stroke

3 2 Y4

Y3

1 0 Time [t] Y1

P

701-05-GB

Y2

M

Y1

1

1

1

0

0

0

0

Y2

0

0

0

0

1

1

0

Y3

0

1

0

0

1

0

0

Y4

0

0

1

0

0

0

0


Festo Didactic 01

23

3 Cylinder stroke

2 Y4

Y3

1 0 Time [t] Y1

P

Y2

Y1

1

1

1

0

0

0

0

Y2

0

0

0

0

1

1

0

Y3

0

1

0

0

1

0

0

Y4

0

0

1

0

0

0

0

M

Electro-hydraulics 701-05-GB

6


Title


Guide

• • • • •

Festo Didactic

Example for proportional hydraulics: Control of velocity stages. Hydraulic circuit requirement considerably reduced, electrical signal control section extended. Additional requirements for commissioning: Setting of setpoint values and ramp functions. Analogue valve cross section openings according to setpoint values and thus different flow range, i.e. actuator speeds. Flexibility thanks to electrical control, e. g: an additional velocity stage requires only one additional setpoint value.

01 2

3 4

IY1 Current Time [t]

IY2 Cylinder stroke 4

IY1

IY2 Y1

3

Y2 2

P

1 0

M

Time [t]

Y1

701-06-GB

Y2


Festo Didactic 01 2

3 4

IY1 Current Time [t] IY2 Cylinder stroke 4

IY1

IY2 Y1

3

Y2 2

P

1 0 M

Time [t] Y1

Proportional hydraulics 701-06-GB

Y2

7


Festo Didactic

Title

Electro-mechanical transducers

Guide

•

• • • •

Proportional solenoid: Further development of switching solenoid. The magnetic flux causes a force which remains constant throughout the stroke. The force acts only in one direction. The extent of the magnetic force is proportional to the magnetic flux. Due to its force, the servo drive of the proportional solenoid is particularly suitable for the direct actuation of standard proportional valves. Plunger coil: Also an electro-dynamic principle, whereby a force acts on a current carrying conductor in the magnetic field. Depending on the direction of current the plunger coil is deflected up or down. Torque motor: The effects of the permanent and electro magnets are superimposed. The magnetic force causes a torque to the right or the left. The servo drive, plunger coil and torque motor have a high natural frequency, which makes them suitable for the indirect actuation of highly dynamic proportional and servo valves.

F

Power consumption

701-07-GB

[W]

x

N

N

S

S

x

Proportional soleonid

Plunger coil

Torque motor

5 - 40

0.2 - 5

0.02 - 4

20 - 1000

8 - 80

2 - 40

Working stroke

[Nmm]

Linear deviation

(%)

0.5 - 6

1-7

1-2

Critical frequency

[Hz]

10 - 150

100 - 200

100 - 300


Festo Didactic

F Proportional solenoid Power consumption

x Plunger coil

[W]

Working stroke [Nmm] Linear deviation

(%)

Critical frequency

[Hz]

Electro-mechanical transducers 701-07-GB

N

N

S

S

x Torque motor

8


Title

D.C. switching solenoid

Guide

• • • •

Festo Didactic

Magnetic field lines of a coil. Existence of a homogenous magnetic field within a coil without magnet core or armature. Radial air gap and axial air gap form different “resistances” in the magnetic field. The magnetic force acts on the armature mainly via the radial air gap, since in this case the gap between the core and armature remains small.

Radial air gap

Homogenous magnetic field

Magnetic field lines

701-08-GB

Axial air gap


Festo Didactic

D.C. switching solenoid 701-08-GB

9


Festo Didactic

Title

Proportional solenoid with intermediate ring

Guide

• • • •

Different magnetic forces act on the armature via the axial air gap. Reducing the magnetic field lines via the radial air gap by means of installing a non-magnetisable intermediate ring. The new distribution of the magnetic field line leads to a virtually constant magnetic force pattern within the working stroke range. 1 = Magnetic force characteristic in the axial air gap 2 = Magnetic force characteristic in the radial air gap 3 = Summation characteristic curve

Radial air gap Axial air gap a

Magnetic force [N]

b

6

c

3

3 2

1 = Magnetic force characteristic in the axial 0 air gap 2 = Magnetic force characteristic in the radial air gap 3 = Summation characteristic curve

1

701-09-GB

a

Working stroke b ≈ 1mm

c

Piston position


Festo Didactic

Magnetic force [N] 60

a b c

30

0 Piston position

Proportional solenoid with intermediate ring 701-09-GB

10


Festo Didactic

Title

Proportional solenoid, stroke controlled

Guide

• •

• •

The solenoid force is proportional to the electrical input signal. Poppet principle: The valve cone is pressed against the valve seat via a spring; the valve opens as soon as the hydraulic force on the valve cone exceeds the pilot force, whereby the entire spring/ plunger system is moved back. Spool principle: the valve piston is pushed against the spring, the stroke movement ceases when the magnetic force and the spring force are in equilibrium. Force/stroke characteristic curves: Magnetic force with specified current values in relation to plunger position; characteristic curve of a pressure loaded spring.

Poppet principle Characteristic force/stroke curves Magnetic force [N]

Characteristic spring curve

6

Spool principle 3

0 Piston Working stroke Idle stroke position

701-10-GB


Festo Didactic

Characteristic force/stroke curves Magnetic force [N] 60

30

0 Piston position

Proportional solenoid, stroke controlled 701-10-GB

11


Festo Didactic

Title

Proportional solenoid, force controlled

Guide

• • •

The solenoid force is proportional to the electrical input signal. Only poppet type valves can be operated via force controlled solenoids. This valve is used as a pilot pressure valve for directional or pressure control valves because of the reduced flow rates.

Force/current characteristic curve

P

Magnetic force F [N]

T Poppet principle (only) F~I P

Magnetic flux I [A]

701-11-GB

T


Festo Didactic

P Magnetic force F [N]

T

Magnetic flux I [A]

Proportional solenoid, force controlled 701-11-GB

12


Festo Didactic

Title

Proportional solenoid, components

Guide

•

Construction of proportional solenoids.

•

D.C. solenoid group.

• •

Representation of the most important components of a proportional solenoid. Electro-mechanical transducer: the electrical input signal is converted into a mechanical output signal.

Electrical connection

Venting screw

Non-magnetisable inner ring Control cone

Compensating spring

Core magnet

Plain bearing Guide rod (stem) Housing Stop/Guide disc Barrel magnet Exciting coil

701-12-GB

Armature


Festo Didactic

Proportional solenoid, components 701-12-GB


13

Title

Electronic activation

Guide

• • • •

Festo Didactic

Control stages of a proportional amplifier for magnetic flux generation. The input signal is set by means of ramp time, minimum or maximum current and pulse duration modulation. Both the amplification of the signal and the conversion by means of a V/I converter take place during the output stage. Proportional solenoid valves are to be actuated via an adjustable D.C. current of 0 to 800 mA.

A

B

P

T

V I

Y1

Y2

V I

Setpoint specification

701-13-GB

Ramp setting

Setting of amplifier characteristic

Pulse-duration modulation

V/I-converter

Proportional valve


Festo Didactic

A

B

P

T

V I

V I

Electronic activation 701-13-GB

Y1

Y2

14


Festo Didactic

Title

Proportional amplifier

Guide

•

Control panel of a setpoint and amplifier card.

•

W1 - W8: Input of up to 8 setpoint values.

•

R1 - R4: Setting of ramps. TIME = Ramp time.

•

IA - IB: Setting of initial, jump and maximum current.

•

24V, 0V: Supply voltage.

•

Liquid crystal display for representation of all parameters.

+24V

+24V

+24V

+24V

W1

A

I1

I2 R1

I3

OUT

W1 W2

R2 R3

W2

W3 W4

R4

IB W1 W2

W5 TIME

INT W1

W6 W7

FUNCTION

INT W2

D/E OUT W8 CONTRAST

0V

701-14-GB

0V

0V

B

FUNCTION IA IA BASIC IB BASIC IA JUMP IB JUMP

INT W1 IA MAX INT W2 IB MAX D/E DITHERFREQ. CONTRAST

OE A OE B

0V


Festo Didactic

+24V

+24V

+24V

+24V

W1

A

I1

I2 R1 R2 R3

I3

OUT

W1 W2

W2

W3 W4

R4

W2

W5 TIME

INT W1

W6 W7

FUNCTION

INT W2

D/E OUT W8 CONTRAST

0V

0V

0V

Proportional amplifier 701-14-GB

B

FUNCTION IA IA BASIC IB IB BASIC W1 IA JUMP IB JUMP

INT W1 IA MAX INT W2 IB MAX D/E DITHERFREQ. CONTRAST

OE A OE B

0V


15

Title

Ramp shaper

Guide

• • • • •

Left: Signal transmission in switching hydraulics. Right: Signal transmission in proportional hydraulics with ramp shaper. Use of ramps for adjustable acceleration or delay of hydraulic drive components. Angular setting: The ramp angle determines the adjustable speed of the valve piston. Elimination of pressure peaks and switching impacts in the hydraulic system. Displacement positions: 0: Retracted end position 1: Acceleration completed 2: Delay initiated (signal generator) 3: Forward end position

Displacement

Displacement Signal generator

3 2

3 0

Festo Didactic

3

0 1

23

Cylinder

1 0

0 t0

t 3 Time [t]

t0

t1

t2 t3

Time [t]

Y1 100% Control signal

Y1

0% t0

t1

t2 t3

Time [t]

Y1 1 Y1

1 Input signal

Y2 0

0 t0

701-15-GB

Signal generator

Time [t]

t0

t2

Time [t]

Y2


Festo Didactic

Displacement

Displacement 3 2

3 0

3

0 1

23

1 0

0 t0

t 3 Time [t]

t0

t1

t2 t3

Time [t]

Y1 100% Y1 0% t0

t1

t2 t3

Time [t]

t2

Time [t]

Y1 1 Y1

1

Y2 0

0 t0

Time [t]

t0

Ramp shaper 701-15-GB

Y2

16


Festo Didactic

Title

Minimum current – Maximum current

Guide

• • • •

Setting of minimum and maximum current for adjustment of proportional directional control valve to flow rate of hydraulic pump. Minimum current for adjustment of jump current to control edge. Maximum current or adjustment of maximum cross section of the opening in relation to flow rate QPump. A linear characteristic curve runs between minimum and maximum current.

[mA]I 80 0

Imax Setting

Amplifier characteristic

Setting I min

0 Setpoint value 10 Volt

∆Q ≈ 0

∆s = min.

701-16-GB

∆Q ≈ max.

∆s = max.


Festo Didactic

I [mA] 800

0

Setpoint value 10 Volt

Minimum current – Maximum current 701-16-GB

17


Title

Output stage (V/I converter)

Guide

• • • • •

Festo Didactic

The setpoint voltage is converted into a magnetic flux in the output stage. Closed-loop control of magnetic flux through comparison of setpoint value and actual value on the measuring shunt RM. The closed control loop is created by means of connecting the actual value via the feedback resistor RR. The closed control loop eliminates the effects resulting from operating voltage fluctuations and/or the effects resulting from proportional solenoid heating. The solenoid coil has an ohmic resistor RS and an inductive resistor LS.

VI Input signal R I Input resistance

VV Power supply voltage RS Coil: Ohmic resistor LS Coil: Inductive resistor Solenoid coil

RR Feedback resistor

RS LS

RM Measuring shunt

701-17-GB


VI

Festo Didactic

VV

RI

RS

RR

LS

RM

Output stage (V/I converter) 701-17-GB


18

Title

Pulse duration modulation

Guide

• • • •

Solenoid voltage

Festo Didactic

Recording of pulsed voltage signals and the associated magnetic flux. The output voltage is maintained at a constant level. The switch-on/ switch-off ratio (pulse duration) within a time period T influences the size of the effective magnetic flux. Clean-switching operations prevent excessive heating of the output stage and power dissipation is kept to a minimum. An oscillating output current is obtained thanks to pulse duration modulation. Sliding friction prevails at the plunger thanks to this dither effect and the hysteresis is improved.

V 24 V

T = Duty cycle

I eff = Effective magnetising current 0 Time V 24 V

T

I eff 0 Time V 24 V

T I eff

0 Time

701-18-GB


Festo Didactic

V

T = Periodendauer

24 V I eff 0Time V

T

24 V I eff 0Time V

T

24 V I eff

0Time

Pulse duration modulation 701-18-GB

19


Title

Hysteresis

Guide

• • • •

Festo Didactic

The friction of the valve piston spool causes a resistance to directional movement. Hysteresis: Differential current during approach of a pressure or flow rate value from different directions. Pulse duration modulation: Reduction of hysteresis by means of continuous slight oscillating movement of the piston spool (sliding friction). Avoidance of pressure peaks in the hydraulic system.

p [bar]

∆I

50 40 30 20 Pulse duration modulation

10

0

701-19-GB

100 200 300 400 500 600 700 800

I [mA]


Festo Didactic

p [bar] 50 40 30 20 Pulse duration modulation

10

0

100 200 300 400 500 600 700 800 I [mA]

Hysteresis 701-19-GB

20


Title

Flow characteristic curves

Guide

• • •

Festo Didactic

Representation of control piston with different control notches; Representation of the corresponding flow characteristic curves. Delta control edge pattern: Precision controllability for small volumetric flow rates, clear changes within the range of large volumetric flow rates. The stroke travel of a piston with control notches corresponds to the maximum length of the notch opening.

Q [l/min] 8 6 4 2 0 100

400

700 I [mA]

100

400

700 I [mA]

Q [l/min] 8 6 4 2 0

701-20-GB


Festo Didactic

Q [l/min] 8 6 4 2 0 100

400

700 I [mA]

100

400

700 I [mA]

Q [l/min] 8 6 4 2 0

Flow characteristic curves 701-20-GB

21


Title

Control edge patterns

Guide

• • • •

701-21-GB

Festo Didactic

Control edge pattern for the purpose of determining the flow behaviour of the valve. The adjustment of flow behaviour is linear, progressive, degressive or generally according to the task. Number of precision control openings on the periphery of the control piston depending on valve function. The sleeve system is easier to produce in terms of production technology.


Festo Didactic

Control edge patterns 701-21-GB

22


Title

Piston opening ratio

Guide

• •

Festo Didactic

Example: Actuation of a 2:1 cylinder. The ratio of the valve flow cross sections is adjusted to the cylinder inlet and outlet by means of control edge pattern.

Cylinder 2:1

A

T

701-22-GB

B

P

T


Festo Didactic

Piston opening ratio 701-22-GB

23


Festo Didactic

Title

Piston overlap

Guide

•

Representation of positive, negative and zero overlap.

•

Alternative designations: Overlap, underlap and zero intersection.

• •

The opening of the valve port is dependent on the notched opening in relation to the control edge. The flow rate is also adjusted by means of the throttle opening ratio of the control piston. The number of radially configured notches on the control piston.

QL

QA positive

X >0

X

QB QA

zero

QL

X =0

QB

X QL

QA negative

X <0

701-23-GB

QB

X


Festo Didactic

QL

QA

X

X

QB QA

QL

X QB

X QL

QA

X QB

Piston overlap 701-23-GB

X

24


Title

Pressure relief valve, piloted

Guide

• • • •

Festo Didactic

Sectional view of a pressure relief valve. The mode of operation corresponds to that of a conventional, piloted pressure relief valve. Piloted stage: the force set for the proportional solenoid is transferred to the pilot poppet via the spring. As soon as the pressure acting on the pilot valve exceeds the value set, the poppet valve opens. The venting control flow generates a pressure drop at the main stage, whereby this opens.

Y

p [bar] 5 4 3 T

2

P

1 TY

P 0

701-24-GB

20

40 I [mA]


Festo Didactic

Y

p [bar] 50 40 30 T

20

P

10 TY P 0

200

400 I [mA]

Pressure relief valve, piloted 701-24-GB

25


Festo Didactic

Title

Pressure regulating valve, piloted

Guide

•

Sectional view of a piloted pressure regulating valve.

•

Reduction of system pressure to a specific value.

•

Application for subranges within a hydraulic system.

Y

A

P A

701-25-GB

PY


Festo Didactic

A PY

Pressure regulating valve, piloted 701-25-GB

26


Festo Didactic

Title

Flow control valve

Guide

•

Sectional view of a flow control valve.

•

Normal position: all ports are closed.

•

Depending on the piston deflection, control cross sections (holes in the piston, control sleeve) and thus the flow are changed.

AB

PT

A

B

Q l [ ] min 8

Flow characteristic curve

6 4 2 P

701-26-GB

T

0

100 200 300 400 500 600 I [mA]


Festo Didactic

AB

PT Q [

l ] min 8 6 4 2 0

Flow control valve 701-26-GB

100 200 300 400 500 600 I [mA]

27


Title

4/3-way valve

Guide

• •

Festo Didactic

Essential functional components: Proportional solenoids, main spool, reset spring. Multiple functions: Directional control, speed control, hydraulic clamping of power components (throttle opening ratio).

AB

PT

T B P A

701-27-GB


Festo Didactic

AB

PT

4/3-way valve 701-27-GB

28


Title

4/3-way valve, piloted

Guide

• • • • •

Festo Didactic

Pressure relief valves for pilot control of a 4/3 proportional directional control valve. Electrical signal to one of the two proportional solenoids increases the pressure inside the control chamber of the main spool to a specified value (relief pressure). The control piston is moved up to the equilibrium position with the opposing spring action. High control force due to minimum control pressure of 25 bar eliminates sensitivity to disturbance factors. This is however associated with continuous control oil consumption. Without an electrical signal, the control piston is centred by means of the springs.

AB

PT

P

P

T

T

Actuation B

Actuation A

T

701-28-GB

A

P

B


Festo Didactic

AB

PT

P

P

T

T

T

A

P

B

4/3-way valve, piloted 701-28-GB

Hidraulica Proporcional Festo

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