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Synchronizer

Cone clutch, dog clutch, and translational detent assembled to provide smooth gear engagement

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Clutches

Description

The block represents a synchronizer that contains a dog clutch, a cone clutch, and a translational detent. The shift linkage first translates to engage the cone clutch. Frictional torque causes the shift linkage and cone clutch shaft to rotate at equal speed. When the force acting on the shift linkage exceeds the detent force, the dog clutch can engage.

The schematic illustrates a synchronizer in the disengaged state. In this state, the ring (R) and hub (H) shafts can spin independently at different speeds. To synchronize ring and hub shaft speeds, the shift linkage (S) translates toward the hub shaft to engage the cone clutch. The friction surfaces of the cone clutch produce a frictional torque that equalizes the rotational speeds of the ring and hub shafts. The dog clutch teeth (T) can engage when the translational force acting on the shift linkage exceeds the peak detent force. The peak detent force should allow sufficient time and normal force to equalize ring and hub shaft speeds so that the dog clutch can engage.

The model implements Dog Clutch, Translational Detent and a modified version of Cone Clutch blocks. Refer to each block reference page for more information on the corresponding block function. You can use a similar approach to model customized versions of the synchronizer. One example is the Gearbox (Detailed) subsystem in the model sdl_manual_transmissionsdl_manual_transmission.

Connections R and H are mechanical rotational conserving ports that represent the ring (R) and hub (H), respectively. Connection S is a mechanical translational conserving port that represents the ring shifter handle.

Connections X1 and X2 are physical signal outputs that report the shift linkage positions of the dog clutch and cone clutch, respectively. The shift linkage positions are zero when the clutch is fully disengaged. When the dog clutch is fully engaged, the dog clutch shift linkage position has a magnitude equal to the sum of the dog clutch ring-hub gap and the tooth height. When cone clutch is fully engaged, the cone clutch shift linkage position has a magnitude equal to the cone clutch ring-hub gap.

Assumptions and Limitations

  • The model does not account for inertia effects. You can add a Simscape™ Inertia block at each port to add inertia to the synchronizer model.

Dialog Box and Parameters

Dog Clutch

Torque Transmission Model

Model used to represent torque transmission. The default setting is Friction clutch approximation - Suitable for HIL and linearization.

Each model provides the following common parameters:

Clutch teeth mean radius

Mean radius of the clutch teeth. The parameter must be greater than zero. The default value is 200 mm.

Maximum engagement speed

The relative angular speed between the ring and hub shafts above which the dog clutch cannot engage. The value is specific to the specific gearbox or transmission and must be minimized to avoid high dynamic impact during engagement. The default value is inf rad/s

 Friction clutch approximation - Suitable for HIL and linearization

 Dynamic with Backlash

Cone Clutch

Contact surface maximum diameter

Outer diameter of the friction material linen that lines the cone clutch disks. The parameter must be greater than zero. The default value is 150 mm.

Contact surface minimum diameter

Inner diameter of the friction material linen that lines the cone clutch disks. The parameter must be greater than zero, but smaller than the value of Contact surface maximum diameter.

Cone half angle

Half angle of the clutch cone. The parameter must be greater than zero and less than or equal to 90°. The default value is 12 deg.

Friction model

Specification method for the kinetic friction coefficient between cone clutch disks in slipping conditions. Options include:

  • Fixed kinetic friction coefficient — Specify a single value for the kinetic friction coefficient. This value is constant across all clutch relative velocities. Selecting this option exposes an additional parameter, Kinetic friction coefficient.

  • Table lookup kinetic friction coefficient — Specify a lookup table with the kinetic friction coefficient values as a function of the clutch slip velocity. Selecting this option exposes additional parameters for the lookup table values and interpolation/extrapolation methods.

Kinetic friction coefficient

Kinetic friction coefficient between the friction surfaces of the cone clutch disks. The parameter must be greater than zero. The default value is 0.3.

Kinetic friction coefficient relative velocity vector

Vector with the clutch slip velocities at which to define the kinetic friction coefficient.

Kinetic friction coefficient vector

Vector with the kinetic friction coefficient values corresponding to the clutch slip velocities in Kinetic friction coefficient relative velocity vector.

Friction coefficient interpolation method

Method for calculating kinetic friction coefficients between lookup-table data points. Options include Linear, Cubic, and Spline.

Friction coefficient extrapolation method

Method for calculating kinetic friction coefficient values outside of the lookup-table data range. Options include From last 2 points and From last point.

Static friction coefficient

Static friction coefficient between the friction surfaces of the cone clutch disks. The parameter must be greater than the kinetic friction coefficient. The default value is 0.35.

Velocity tolerance

Relative velocity between the cone clutch disks below which the disk friction surfaces lock. Surface locking requires that the torque across the R and H rotational ports be smaller than the product of the effective radius, the static friction coefficient, and the applied normal force. The default value is 0.001 rad/s.

Threshold force

Minimum value of the applied normal force for frictional torque transmittal to occur. If the value of the parameter exceeds the value of the applied normal force, no frictional torque is transmitted.

Detent

Peak force

Peak shear force of the detent. The default value is 500 N.

Notch width

Width of the region where the detent exhibits shear force. The default value is 3 mm.

Viscous friction coefficient

Viscous friction coefficient at the contact surface of the detent. The parameter must be greater than or equal to zero. The default value is 0.1 N/(m/s).

Friction to peak force ratio

Ratio of the kinetic friction to the peak shear force of the detent. The parameter is used to set the value of the kinetic friction. The parameter must be greater than or equal to zero. The default value is 0.01.

Friction velocity threshold

Velocity required for peak kinetic friction at the contact surface of the detent. The parameter ensures the force is continuous when the travel direction changes, increasing the numerical stability of the simulation. The parameter must be greater than zero. The default value is 0.05 m/s.

Shift Linkages

Linkage travel direction

Direction the shift linkage must translate along in order to engage the clutch. The default setting is Positive shift linkage displacement engages clutch

Ring-hub clearance when dog clutch disengaged

Distance between ring and dog clutch hub with the ring fully retracted. The parameter specifies the maximum travel distance if engagement requirements are not met. The parameter must be greater than the value of Ring-hub clearance when cone clutch disengaged. The default value is 5 mm.

Tooth overlap to engage

Minimum value of the tooth overlap beyond which the dog clutch is considered engaged. The parameter must be greater than zero. The default value is 3 mm.

Tooth height

Height of dog clutch teeth. The parameter must be greater than zero. The default value is 10 mm.

Ring-hub clearance when cone clutch disengaged

Distance between the ring and cone clutch hub when the ring is fully retracted. The cone clutch can begin to engage once the slider has translated this distance. The ring can travel only this distance if the engagement requirements are not satisfied. The parameter must be greater than zero. The default value is 3 mm.

Hard stop at back of shift linkage

Hard stop that prevents the shift linkage from traveling beyond the fully disengaged position. Choices include:

  • No hard stop when fully disengaged

  • Hard stop when fully disengaged

The default setting is Hard stop when fully disengaged.

Dog clutch ring stop stiffness

Stiffness of the hard stops on both sides of the dog clutch ring. The model assumes the ring and stops behave elastically. Contact deformation is proportional to the applied force and the reciprocal of the contact stiffness. The value of the stiffness must be assigned with reference to the parameter Tooth overlap to engage. Too low a stiffness could cause the deformation to exceed the required overlap and initiate a false engagement. The parameter must be greater than zero. The default value is 1e+6 N/m.

Cone clutch ring stop stiffness

Stiffness of the hard stops on both sides of the cone clutch ring. The model assumes the ring and stops behave elastically. Contact deformation is proportional to the applied force and the reciprocal of the contact stiffness. The parameter must be greater than zero. The default value is 1e+6 N/m.

Dog clutch ring stop damping

Translational contact damping between the dog clutch ring and the hub. The value of the damping is inversely proportional to the number of oscillations that occur after impact. The parameter must be greater than zero. The default value is 1e+3 N/(m/s).

Cone clutch ring stop damping

Translational contact damping between the cone clutch ring and the hub. The value of damping is inversely proportional to the number of oscillations that occur after impact. The parameter must be greater than zero. The default value is 1e+3 N/(m/s).

Viscous friction coefficient

Viscous friction coefficient for the relative translational motion between the hub and the ring. The value of the parameter depends on lubrication state and quality of contacting surfaces. The coefficient must be greater than or equal to zero. The default value is 100 N/(m/s).

Initial Conditions

Initial state

Beginning configuration of cone and dog clutches. Choices include:

  • Both clutches unlocked—Cone and dog clutches transmit zero torque between the ring and hub shafts.

  • Cone clutch locked—Cone clutch transmits torque between the ring and hub shafts.

  • Both clutches locked—Cone and dog clutches transmit torque between the ring and hub shafts.

The default value is Both clutches unlocked.

Dog clutch initial shift linkage position

Initial position of the shift linkage section that attaches to the dog clutch. The value of the parameter has the following restrictions:

Linkage Travel Direction Dog Clutch StateParameter Restriction
Positive shift linkage displacement engages clutchInitially engagedParameter must be greater than the sum of parameters Ring-hub clearance when dog clutch disengaged and Tooth overlap to engage
Initially disengagedParameter must be smaller than the sum of parameters Ring-hub clearance when dog clutch disengaged and Tooth overlap to engage
Negative shift linkage displacement engages clutchInitially engagedNegative of the parameter must be greater than the sum of parameters Ring-hub clearance when dog clutch disengaged and Tooth overlap to engage
Initially disengagedNegative of the parameter must be smaller than the sum of parameters Ring-hub clearance when dog clutch disengaged and Tooth overlap to engage

The default value is 0 mm.

Cone clutch initial shift linkage position

Initial position of the shift linkage section that attaches to the cone clutch. The value of the parameter has the following restrictions:

Linkage Travel Direction Dog Clutch StateParameter Restriction
Positive shift linkage displacement engages clutchInitially engagedParameter must be greater than the value of Ring-hub clearance when cone clutch disengaged
Initially disengagedParameter must be smaller than the value of Ring-hub clearance when cone clutch disengaged
Negative shift linkage displacement engages clutchInitially engagedNegative of the parameter must be greater than the value of Ring-hub clearance when dog cone disengaged
Initially disengagedNegative of the parameter must be smaller than the value of Ring-hub clearance when dog cone disengaged

The default value is 0 mm.

Initial dog clutch ring-hub offset angle

Initial angle between the ring and hub portions of the dog clutch. To edit the parameter, you must set Dog Clutch > Torque transmission model to Dynamic with backlash. If the clutch is disengaged, the initial angle must lie in the range -π/N ≤ θ ≤ +π/N, where N denotes the number of teeth in the dog clutch. If the clutch is engaged, the initial angle must be in the range -δ/2 ≤ θ ≤ +δ/2, where δ is the backlash angle. The default value is 0 deg.

Ports

PortDescription
SConserving translational port that represents the shift linkage
RConserving rotational port that represents the ring shaft
HConserving rotational port that represents the hub shaft
X1Physical signal output port that measures the magnitude of the dog clutch translation
X2Physical signal output port that measures the magnitude of the cone clutch translation

See Also

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