Danfoss Selection of Driveline Components User guide
Applications Manual
Selection of Driveline Components
powersolutions.danfoss.com
Applications Manual
Selection of Driveline Components
Revision history Table of revisions
Date Changed Rev
July 2015 Minor edits 0304
April 2015 Minor edits CC
December 2014 Corrections to the equations CB
November 2013 Major rewrite - Danfoss layout CA
July 1997 Second edition B
2 | © Danfoss | July 2015 BLN-9885 | BC00000245en-US0304
Applications Manual
Selection of Driveline Components
Contents
Introduction
Applications Manuals......................................................................................................................................................................4
Selection of Driveline Components
Introduction........................................................................................................................................................................................5
Design Goal.........................................................................................................................................................................................5
Sizing Procedure...............................................................................................................................................................................5
Machine Corner Power (CP)..........................................................................................................................................................6
Variable or Fixed Motor..................................................................................................................................................................8
Motor Selection.................................................................................................................................................................................9
Final Drive Selection..................................................................................................................................................................... 11
Input Gearing...................................................................................................................................................................................13
Pump Selection...............................................................................................................................................................................14
Continuous Pressure.....................................................................................................................................................................16
System Sizing Flow Chart............................................................................................................................................................17
Sizing Flow Chart...................................................................................................................................................................... 19
Equations.......................................................................................................................................................................................... 23
Definition of Terms........................................................................................................................................................................25
Tractive Effort
Tractive Effort.................................................................................................................................................................................. 26
Acceleration
Acceleration.....................................................................................................................................................................................30
Charge Pump Sizing
Introduction.....................................................................................................................................................................................33
Charge Pump Considerations....................................................................................................................................................33
Charge Pump Sizing Worksheet...............................................................................................................................................36
©
Danfoss | July 2015 BLN-9885 | BC00000245en-US0304 | 3
Applications Manual
Selection of Driveline Components
Introduction
Applications Manuals
Content included in these manuals
These applications manuals provide design theory and detailed calculations for building hydraulically
powered machines.
The original document was written as one manual with four sections.
The current set of manuals includes the four documents listed below. The section numbers from the
original document are listed in parenthesis after the current document title.
•
Selection of Driveline Components BLN-9885 (originally Section 1)
•
Pressure and Speed Limits for Hydrostatic Units BLN-9884 (originally Section 2)
•
Transmission Circuit Recommendations BLN-9886 (originally Section 4)
•
Fluids and Lubricants 520L0463 (originally Section 3)
Other Reference Manuals
•
Hydraulic Fan Drive Systems Technical Information 520L0824
•
Hydraulic Fan Drive Systems Design Guidelines 520L0926
4 | © Danfoss | July 2015 BLN-9885 | BC00000245en-US0304
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Introduction
This section presents a method of sizing driveline components for typical closed loop hydrostatic
transmissions. Although the method was developed for propel systems, it may be used for winch, or reel,
applications, or other circuits with very slight modifications. The terminology used in this procedure also
tends to reflect off-highway mobile applications.
It is assumed that the specific functional requirements of the application have been defined, and that the
fundamental design parameters have been established for each mode of operation. These typically
include vehicle speed, gradability, useful life, vehicle weight, and drive configuration. It is also assumed
that required engine power has been established.
Design Goal
The goal of this design method is to optimize the performance and cost of the driveline system by
selecting appropriate driveline components. Smaller hydraulic components cost less than larger
components, but they have lower torque capability.
Hydraulic unit life is highly dependent on system pressure. Establish maximum and continuous pressure
based on the required life of the driveline. Danfoss document Pressure and Speed Limits for Hydrostatic
Units BLN-9884 covers this subject in detail.
The figure below Driveline Element Selection shows the components typically found in a closed loop
hydrostatic drive system as well as the design parameters and degree of design flexibility associated with
each component. Because driveline design includes so many variables (each dependent on the others),
and because final component selection is ultimately limited by product availability, several iterations of
this procedure may be required before arriving at the optimum system.
Sizing Procedure
The sizing procedure starts with values for the machine maximum torque and required speed. From
these values, a hydraulic motor size can be selected. This motor selection is then made compatible with
ratings of available output gear drives. From a motor size, a pump size can be established. The pump
must be capable of accepting the required input power, and it must be compatible with the pump drive
mechanisms. It must also be large enough to provide sufficient flow to the drive motor to attain the
required speed.
©
Danfoss | July 2015 BLN-9885 | BC00000245en-US0304 | 5
Driving
Element
Design
Parameter
Design
Flexibility
Power
Speed
No
Engine
SometimesRatio
Gearing
Yes
Size
Pressure
Speed
Pump
Size
Pressure
Speed
Yes
Motor
Rati
o U
suallyGearing
Speed
Weight
No
Load
Driveline Element Selection
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Machine Corner Power (CP)
Optimizing the size of the hydraulic units depends on selecting the correct gear ratios. By matching machine
corner power with motor corner power, the required unit sizes can be quickly determined. The gear ratios can
usually be adjusted to provide some optimization of hydraulic unit component size.
Along with the equations presented throughout this document, a sizing flowchart is included to assist
with sizing. The flowchart details the sizing procedure and includes numerous design check steps to
validate the calculated sizing values.
Design limits for associated mechanical components are not identified.
Machine designers should verify that the design parameters are met for all driveline components.
The steps outlined in this manual are designed to guide you in component selection. For further
assistance, contact your Danfoss representative for help interpreting and verifying your results.
The first step in the sizing process is to determine the value referred to as Machine Corner Power (CP).
The concept of Corner Power is abstract and is normally not an attainable value of transmission power. It
is useful in the design process because it provides an indication of transmission component size and ratio
requirements. Corner Power is representative of the maximum torque and the maximum speed (at full
load) that the machine is required to have. These two values of maximum speed and maximum torque
(or Tractive Effort) never happen at the same time, but the purpose of Corner Power is to capture both
values to define an operating envelope for the machine and to aid in the selection of the hydraulic motor.
Refer to the Machine Corner Power graph below for an illustration of the concept.
The concept of Corner Power also applies to hydraulic motors. As demonstrated in the topic Motor
Selection on page 9, the maximum corner power of a hydraulic motor represents the maximum torque
and maximum continuous speed capabilities of that product. Equations are provided in the Motor
Selection topic that allow you to select the appropriate motor based on the machine’s corner power.
The equations for calculating Corner Power are provided below. For rotary drives (work function), the
input values to the equation are the required maximum output torque and the maximum output speed
6 | © Danfoss | July 2015 BLN-9885 | BC00000245en-US0304
CP
Max System Pressure
HP Out
(Approx. 0.70 HP In)
Output
Torque
Output Speed
Rated Speed
Part Load Speed
No Load, High
Idle Speed (NLHI)
Full Load Speed
BLN-9885-4
W
W
CP = machine corner power kW (hp)
TQ = maximum drive output torque Nm (in lbf)
ND = maximum drive output design speed rpm
SI System US System Description
1)
Rotary Drives
TE = maximum vehicle tractive effort N (lbf)
S = maximum vehicle design speed kph (mph)
Propel Drives
Machine CP =
TQ • ND
63 025
Machine CP =
TQ • ND
9549
Machine CP =
TE • S
375
Machine CP =
3600
TE • S
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
(at full load) of the machine. For propel drives, the input values are maximum tractive effort and
maximum vehicle speed (at full load).
For multi-speed drives (e.g. work mode and travel mode), corner power must be calculated for all ranges.
Tractive Effort
Tractive Effort refers to the amount of force available at the wheel or wheels of the vehicle and represents
the maximum possible pull a vehicle could exert, if it had no resistance to movement.
Ideally, tractive effort or output torque requirements should be derived from actual tests of the machine.
However, for establishing tractive effort design values, an analytical approach based on machine
parameters and functional modes of operation has been used successfully.
The topic Tractive Effort on page 26 describes tractive effort in more detail.
Machine Corner Power
Machine Corner Power (CP) is determined by estimating the maximum torque and maximum output
speed required. It is normally greater than actual transmission output power. Maximum output speed is
assumed to be at engine rated speed. However, under part load conditions slightly higher speed may be
obtained.
Warning
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.
Warning
Check to ensure that maximum motor speed is NOT exceeded under dynamic braking conditions, when
engine speed can exceed No Load High Idle (NLHI) ratings.
©
Danfoss | July 2015 BLN-9885 | BC00000245en-US0304 | 7
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Variable or Fixed Motor
Because the machine corner power is an expression of maximum torque (tractive effort) and maximum
vehicle speed, it can be used to establish the effective Transmission Ratio (TR) required to satisfy system
demands.
The effective Transmission Ratio (TR) is the ratio of the required vehicle corner power divided by the
available power from the machine’s prime mover (engine). This ratio is similar to the ratio spread of a
similarly sized mechanical transmission and indicates the amount of hydrostatic ratio which is required.
Systems with high transmission ratios normally benefit from variable, or two-position, drive motors.
For drives with variable load cycles, determine the normal input power (available power) to the
transmission by deducting the average power dedicated to other functions from the maximum engine
power available to the drive.
A Transmission Ratio (TR) greater than 1.0 means that there is not enough engine power available to
meet all of the operating requirements at the same time.
•
Typically, machines with high transmission ratios have high torque (Tractive Effort) requirements at
low speed and high speed requirements at low torque (Tractive Effort). In this case, a large fixed
motor would satisfy the high torque requirements, but operating the same motor to meet the
maximum speed requirement could exceed the speed limit of the motor and require a large
displacement pump. For high transmission ratios, use a variable displacement motor; it can be used
at high displacement to satisfy the maximum torque requirement and then shifted to a smaller
displacement to satisfy the machine’s maximum speed requirement. A fixed motor could be used
with a multi-ratio gearbox for machines with a high transmission ratio, but usually a variable motor
will be the most cost effective solution.
•
If the transmission ratio is low, that means that there is probably enough engine power available to
achieve the maximum torque and speed requirements simultaneously. In those cases, a fixed motor is
suitable for the task.
•
In cases of extremely high transmission ratio, a variable motor may not satisfy the need. In these
cases, a multi-speed gearbox may also be required. Some applications use 2-speed, 3-speed, or 4speed gearboxes to meet the vehicle requirements; but a 2-speed gearbox is most common.
The rule for selecting a fixed or variable drive motor is as follows:
•
If TR is greater than 4, use a variable motor,
•
If TR is less than 2, use a fixed motor,
•
If TR is between 2 and 4, evaluate both variable and fixed motors for suitability,
•
If TR is greater than 14, use a multi-ratio gear box between the motor and the final drive.
There is no direct relationship between transmission ratio and final drive ratio. The final drive ratio is
calculated based on the displacement of the motor that has been chosen, the maximum pressure, the
loaded radius of the wheels, and the required maximum tractive effort.
The transmission ratio is only used to help determine the motor type, not the motor size. Refer to the
topic Final Drive Selection on page 11 to calculate the Final Drive Ratio (FD).]
8 | © Danfoss | July 2015 BLN-9885 | BC00000245en-US0304
TR < 2, use fixed displacement motor
TR > 4, use variable displacement motor
SI / US System Description
TR = effective transmission ratio
HP = normal input power kW (hp)
2) TR =
Machine CP
HP
TR > 14, use multi-ratio gearbox
HP = 0.7
*
Available prime mover power
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Motor Selection
Calculate the required motor corner power from machine corner power and driveline efficiency using
equation (3) Required Motor CP. This establishes the minimum motor size capable of meeting the power
requirement of the machine. For multi-speed drives, use the largest corner power for each of the
operating ranges.
For transmission circuits using multiple drive motors, the required motor corner power should be
interpreted as the required corner power at each motor.
Use equation (4) Maximum Motor CP to calculate the maximum motor corner power based on the design
maximum pressure and the design maximum speed and the desired life of the motor.
Design maximum pressure is the maximum pressure at which the motor is intended to operate to meet
the required life. The design maximum pressure may or may not be the same as the maximum pressure
rating published in the product literature. Published ratings for maximum pressure assume the pressure
will occur for only a small percentage of the operating time, usually less than 2% of the total, and will
result in “normal” life. For applications in which the maximum pressure will occur over a significant
portion of the duty cycle, or applications in which additional life is required, the design maximum
pressure should be assigned a value less than the published rating for maximum pressure.
Design maximum speed is the maximum speed at which the motor is intended to operate to meet the
required life. Although speed has less effect on life than pressure, lower operating speeds will have the
effect of increasing life. The value for the design maximum speed must never exceed the maximum
speed rating published in the product literature; and will usually be less, to allow for motor speed
increases as a result of reduced-load, or no-load, conditions (see Machine Corner Power graph).
Danfoss document Pressure and Speed Limits for Hydrostatic Units BLN-9884, provides additional
information concerning pressure and speed limits with respect to component life.
Ideally, values for the design maximum pressure and design maximum speed would be used in Equation
(4) Maximum Motor CP to determine motor CP capability. However, this is difficult at this stage of the
sizing process because both the motor displacement and final drive ratio are unknown. Despite this
limitation, the next step is to choose a logical motor displacement based on the required motor CP. The
table Hydrostatic Motor Corner Power Chart can be used as an aid in preliminary motor selection. You
©
Danfoss | July 2015 BLN-9885 | BC00000245en-US0304 | 9
should choose a motor with a motor CP at least as large as the required motor CP calculated using
Equation (3) Required Motor CP.
Equation (A) Design Check serves as a design check to ensure that a motor with sufficient corner power
capability is selected. Motor selection based on corner power results in the smallest motor capable of
transmitting the required machine power while achieving system life requirements.
Design Check: Maximum Motor CP ≥ Required Motor CP
3)
4)
A
)
Required Motor CP =
Machine CP
E • #
Required Motor CP =
Machine CP
E • #
Maximum Motor CP =
DM • NM • PM
396 000
Maximum Motor CP =
DM • NM • PM
600 000
SI System
US System Description
# = number of motors
CP = corner power
E = final drive efficiency
DM = maximum motor displacement
NM = design maximum speed
PM = design maximum pressure
3
cc [in
]/rev
rpm
bar [psi]
kW [hp]
(%/100)
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
For variable motor systems, the transmission CP is determined only by the motor. For various pump sizes,
actual applied motor CP may be varied by adjusting the minimum motor angle.
For fixed motor systems, the transmission CP is ultimately determined by the pump speed and
displacement. Although the fixed motor CP must be large enough to accommodate the maximum load
and speed, the pump must be large enough to drive the motor at the required design speed.
An additional sizing exercise may be required for fixed motor systems after pump selection has been
made.
For either variable or fixed motor systems, it may be necessary to increase the motor size if proper output
gearing is not available. Gearing must accommodate both the desired transmission ratio and maximum
motor speed, in addition to meeting the torque requirements.
10 | © Danfoss | July 2015 BLN-9885 | BC00000245en-US0304
Series 15 4500 4350 ---- 4000 --- - --- - 42 31 ---- ----
Series 40 - M25 5000 4350 ---- 4000 ---- ---- 77 57 ---- ---Series 40 - M35 5000 4350 ---- 3600 5300 4200 97 72 113 84
Series 40 - M44 5000 4350 ---- 3300 4850 3900 112 83 132 99
Series 40 - M46 5000 4350 ---- 3600 5000 4500 128 95 160 119
LV/LC25 6000 ---- ---- 5000 4400 --- - --- - 102 76
LV/LC30 5000 ---- ---- 5150 4450 --- - --- - 103 77
LV/LC35 4350 ---- ---- 5300 4500 --- - --- - 106 79
KV/KC38 6000 ---- --- - 5200 4650 --- - --- - 163 122
KV/KC45 5000 ---- --- - 5050 4500 --- - --- - 156 116
Series 90 - 55cc 7000 4250 3900 5100 4600 231 173 273 204
Series 90 - 75cc 7000 3950 3600 4700 4250 291 217 344 256
Series 90 - 100cc 7000 3650 3300 356 266 --- - --- Series 90 - 130cc 7000 3400 3100 435 324 --- - --- -
H1B060 7000 6525 ---- 7250 5900 --- - --- - 382 285
H1B080 7000 6525 ---- 6600 5300 --- - --- - 457 341
H1B110 7000 6525 ---- 5950 4800 --- - --- - 570 425
H1B160 7000 6525 ---- 5250 4250 --- - --- - 734 547
H1B250 7000 6525 ---- 4500 3650 --- - --- - 985 734
51V060 7000 7000 5600 --- - --- - 363 270
51V080 7000 6250 5000 --- - --- - 432 322
51V110 7000 5600 4500 --- - --- - 534 398
51V160 7000 5000 4000 --- - --- - 691 515
51V250 7000 4250 3400 --- - --- - 917 684
Hydrostatic Motor Corner Power Chart
Fixed Variable
Motor
Max
Pressure
(psid)
Max
Working
Pressure
(psid)
Max
Speed
at Max
Angle
(rpm)
Cont Speed at
Max Angle
(rpm)
Max Speed at
Min Ang le
(rpm)
Cont Speed
at Min Angle
(rpm)
Corner
Power
(HP)
Corner
Power
(kW)
Corner
Power
(HP)
Corner
Power
(kW)
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
These values for corner power capability are based on maximum pressure and maximum speed ratings.
Refer to Pressure and Speed Limits for Hydrostatic Units BLN-9884 for detailed information on ratings of
units and expected life.
Final Drive Selection
©
Danfoss | July 2015 BLN-9885 | BC00000245en-US0304 | 11
After the motor is initially sized, calculate the required final drive ratio. One of two approaches can be
taken to determine this ratio. Both take into account the design maximum and continuous pressures
allowed to meet the life requirements of the machine (see Pressure and Speed Limits for Hydrostatic Units
BLN-9884).
The two methods are as follows:
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
1. Using the Sizing Flow Chart on page 19, size the final drive ratio using the design maximum pressure
and the maximum torque requirement. Use equation (5) Required FD on the following page for this
calculation. After the pump is sized and all speed conditions have been met, estimate the continuous
pressure, using the Sizing Flow Chart on page 19, and compare it with the maximum design
continuous pressure.
2. As an alternate method, calculate the final drive ratio required for all modes of operation (travel
mode, work mode, etc.). Calculate the final drive ratio from the assumed pressure and torque
requirements for each operating mode. For worst case or intermittent modes of operation, use the
design maximum pressure along with the tractive effort or torque requirement to obtain a value for
the final drive ratio. Use the design continuous pressure for typical or continuous modes of operation,
and calculate required final drive ratios for these modes as well. Select the largest final drive ratio
from the values calculated for the various operating modes.
For variable or two-position motors, only final drive ratios from those modes utilizing maximum motor
displacement can be calculated, since the motor minimum displacement is not yet known.
The next step is to check motor speed limits using the limits obtained from Pressure and Speed Limits for
Hydrostatic Units BLN-9884, or the respective Technical Information manual.
Motor speed will usually be satisfactory unless the final drive ratio is significantly higher than required
(Gearbox limits must also be met). Equation (6) NMR=FD•NMD is used to determine the required motor
speed at maximum motor displacement based on the final drive ratio calculated in equation (5) Required
FD. For fixed displacement motors, the maximum motor displacement referred to in the equation is
simply the displacement of the motor. For variable motors, use the displacement at the maximum
swashplate angle. Use design check (C) NMR ≤ NML to ensure that the speed limit of the motor is not
exceeded. If a variable motor is specified, use equation (7) NVR=FD•NMD and design check (D) NVR ≤ NVL
to determine if the speed required at the minimum motor displacement exceeds the maximum reduced
angle speed limit. As explained in Pressure and Speed Limits for Hydrostatic Units BLN-9884, the maximum
speed limit of a variable motor increases with decreasing angle, up to a certain value (the maximum
reduced angle speed limit or cutoff point on the speed/angle curve). At low swashplate angles (i.e., below
the angle cutoff point), a decrease in angle does not result in a greater maximum speed limit.
Note that reduced angle speed limits cannot be checked until the pump displacement and minimum
motor displacement have been established. (This will be done in subsequent steps of this procedure.)
However, if the speed exceeds the limit associated with the smallest possible swashplate angle (i.e., at the
cutoff point of the speed/angle curve), then increase the motor’s maximum displacement and recalculate
the final drive ratio.
Refer to Pressure and Speed Limits for Hydrostatic Units BLN-9884 for more information concerning speed
limits.
Both SM (vehicle speed required at max angle) and SV (vehicle speed required at min angle) are customer
defined conditions
12 | © Danfoss | July 2015 BLN-9885 | BC00000245en-US0304
SI System US System Description
Rotary Drives
DM = max motor displacement cc (in
3
)/rev
E = final drive efficiency (%)/100
FD = final drive ratio
LR = wheel loaded radius mm (in)
NMD
NML = motor speed limit at max angle rpm
NMR = req'd motor speed at max angle rpm
NVD = non-propel design speed at min angle rpm
NVR = req'd motor speed at min angle rpm
NVL = motor speed limit at min angle rpm
PM = maximum pressure bar (psid)
SM = vehicle speed req'd at max angle kph (mph)
SV = vehicle speed req'd at min angle kph (mph)
TE = vehicle tractive effort N (lbf)
TQ = max drive output torque Nm (in•lbf)
# = number of motors
Propel Drives
5)
Design Check: FD ≥ Required FD
B)
Propel Drives
Rotary Drives
6)
Design Check: NMR ≤ NML
C)
Propel Drives
Rotary Drives
7)
Design Check: NVR ≤ NVL
D)
NMR = FD • NMDNMR = FD • NMD
NVR = FD • NVDNVR = FD • NVD
Required FD =
DM • PM • E • EM
Torque • 20
π
Required FD =
Required FD =
DM • PM • E • EM • #
TE • LR • 20
π
Required FD =
Torque • 2
π
FD • SM • 2650
LR
NMR =
FD • SM • 168
LR
NMR =
FD • SV • 2650
LR
NVR =
FD • SV • 168
LR
NVR =
DM • PM • E • EM
Torque • 2
π
d’less
E = motor mechanical efficiencyM (%)/100
= non-propel design speed at max angle rpm
DM • PM • E • EM • #
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Input Gearing
The use of input gearing is usually customer defined and determined by the machine configuration. For
vehicles with multiple hydraulic systems, use of an input splitter box is common. Splitter boxes are
usually available with various ratios to accommodate pump speed requirements. For machines with only
a single hydrostatic system (or machines utilizing tandem pumps) a direct drive pump may be
appropriate, in which case the pump speed is the same as the prime mover speed.
Use equation (8) NP = NE•IR to determine the relationship between the prime mover speed, pump speed,
and input gear ratio.
©
Danfoss | July 2015 BLN-9885 | BC00000245en-US0304 | 13
NP = NE • IR8)
SI / US System Description
NP = maximum pump design speed rpm
NE = prime mover design speed rpm
IR = pump input ratio
Applications Manual
Selection of Driveline Components
Selection of Driveline Components
Pump Selection
Pump sizing consists of selecting a pump that will meet the flow (speed) requirements of the motor, or
motors, in the system.
Use equation (9) to determine the required pump displacement. This calculation is based on an assumed
pump input speed. Select a pump displacement at least as large as the calculated displacement. Also,
check that the desired pump speed does not exceed the rated maximum speed for the pump. If the rated
speed limit is exceeded, choose a different pump and calculate the input speed required and the
corresponding input ratio using equations (10) and (11).
With a pump displacement selected, calculate the actual motor speed. The actual speed will usually be
slightly higher than the required motor speed because the pump that is selected will usually have a
displacement slightly greater than the calculated displacement.
Fixed Motor
For a fixed motor, determine the actual motor speed and compare with its rated maximum speed using
equation (12) and design check (G). Note that equation (12) includes a calculation for an overrunning
condition. An overrunning condition is characterized by a speed increase at the pump (and consequently
the motors), typically by as much as 15%. The condition is especially common during downhill operation.
Not only is there an increase in pump speed, but during either downhill operation or vehicle deceleration
using hydrostatic braking; the motor becomes the pump and the pump becomes the motor. The net
result is that the motor will turn faster for any given pump speed than what would be experienced during
normal propel operation.
A 15% increase in engine speed is just an estimate; check with the engine manufacturer for specific
details concerning the engine’s ability to provide dynamic braking and its maximum, or [not-to-exceed]
operating speed.
14 | © Danfoss | July 2015 BLN-9885 | BC00000245en-US0304
Loading...