Documentation

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 Transmission (Detailed) subsystem in the model sdl_vehicle_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.

Modeling Thermal Effects

You can model the effects of heat flow and temperature change through an optional thermal conserving port. By default, the thermal port is hidden. To expose the thermal port, right-click the block in your model and, from the context menu, select Simscape > Block choices. Choose a variant that includes a thermal port. Specify the associated thermal parameters for the component.

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.

Ports

S

Conserving translational port that represents the shift linkage

R

Conserving rotational port that represents the ring shaft

H

Conserving rotational port that represents the hub shaft

X1

Physical signal output port that measures the magnitude of the dog clutch translation

X2

Physical signal output port that measures the magnitude of the cone clutch translation

T

Thermal conserving port. The thermal port is optional and is hidden by default. To expose the port, select a variant that includes a thermal port.

Parameters

Dog Clutch

The methods that are available for parameterizing the torque transmission depend on the variant of the block that you use. If you use the default variant, which has no thermal port, you parameterize the block using one of the options for the Torque Transmission Model parameter. If you select a variant that has a thermal port, you parameterize the block based on temperature.

Clutch teeth mean radius

Mean radius of the clutch teeth. The parameter must be greater than zero. The default value is 50 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.

 Additional Parameters for the Default Block Variant

 Additional Parameters for the Thermal Block Variant

Cone Clutch

Common parameters for the cone clutch are:

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 degrees. The default value is 12 deg.

Velocity tolerance

Relative velocity below which the two surfaces can lock. The surfaces lock if the torque across the B and F rotational ports is less 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

The normal force applied to the physical signal port N is applied to the contact only if the amount of force exceeds the value of the Threshold force parameter. Forces below the Threshold force are not applied, and there is consequently no transmitted frictional torque. The default value is 1 N.

Friction model

Select a parameterization method to model the kinetic friction coefficient. The options and default values for this parameter depend on the variant that you select for the block. The options are:

  • Fixed kinetic friction coefficient — Provide a fixed value for the kinetic friction coefficient. This option:

    • Is visible only if you use the default variant of the block

    • Is the default method for parameterizing the default variant of the block

    • Affects the visibility of other parameters

     Fixed kinetic friction coefficient

  • Table lookup kinetic friction coefficient — Define the kinetic friction coefficient by one-dimensional table lookup based on the relative angular velocity between disks. This option:

    • Is visible only if you use the default variant of the block

    • Affects the visibility of other parameters

     Table lookup kinetic friction coefficient

  • Temperature-dependent kinetic friction coefficient — Define the kinetic friction coefficient by table lookup based on the temperature. This option:

    • Is visible only if you use a thermal variant of the block

    • Is the default method for parameterizing the thermal variant of the block

    • Affects the visibility of other parameters

     Temperature-dependent kinetic friction coefficient

  • Temperature and speed-dependent kinetic friction coefficient — Define the kinetic friction coefficient by table lookup based on the temperature and the relative angular velocity between disks. This option:

    • Is visible only if you use the default variant of the block

    • Affects the visibility of other parameters

     Temperature and speed-dependent kinetic friction coefficient

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. 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.

This parameter is only visible if you select a block variant that does not include a thermal port and set Dog Clutch > Torque transmission model to Dynamic with backlash.

Thermal Port

These thermal parameters are visible only when you select a block variant that includes a thermal port.

Thermal mass

Thermal energy required to change the component temperature by a single degree. The greater the thermal mass, the more resistant the component is to temperature change. The default value is 50 kJ/K.

Initial temperature

Component temperature at the start of simulation. The initial temperature alters the component efficiency according to an efficiency vector that you specify, affecting the starting meshing or friction losses. The default value is 300 K.

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