# Double-Sided Synchronizer

Mechanical double-sided synchronizer

**Libraries:**

Simscape /
Driveline /
Clutches

## Description

The Double-Sided Synchronizer block represents a double-sided synchronizer that contains two back-to-back dog clutches, two back-to-back cone clutches, and one translational detent. In contrast to regular synchronizers, double-sided synchronizers synchronize and mesh gears on both the input and output sides of a transmission. Double-sided synchronizers can engage and disengage gears on two shafts simultaneously, which allows for more complex gear engagement patterns. Heavy-duty commercial vehicles, off-highway equipment, and some high-performance automotive transmissions commonly use these synchronizers.

Shift linkage translation along the negative direction causes the clutches to engage
the ring with hub *A*. Shift linkage translation along the positive
direction causes the clutches to engage the ring with hub *B*. When the
magnitude of the shift linkage translation is smaller than the cone clutch ring-hub gap,
the synchronizer is in neutral mode and does not transmit torque.

The schematic illustrates a double-sided synchronizer in the disengaged state. In this
state, the ring, **R**, and hub,
**H _{A}** and

**H**, shafts can spin independently at different speeds. As the shift linkage,

_{B}**S**, translates in the negative direction, the faces of cone clutch

*A*(

**CC**) come into contact. The friction in the cone clutch decreases the difference in rotational speed between the shafts. When the force on the shift linkage exceeds the peak force of detent,

_{A}**D**, the dog clutch teeth,

**T**, can engage. The detent peak force should be such that the cone clutch has enough time and normal force to bring the shafts to sufficiently similar speeds to allow engagement of the dog clutch. Similarly, translating the shift linkage along the positive direction allows the faces of cone clutch

*B*(

**CC**) to come into contact, and can allow the shaft of the ring to engage with the shaft of the hub

_{B}*B*

**(H**.

_{B})The model implements two Dog Clutch blocks, two Cone Clutch blocks, and one Translational Detent block. Refer to each block reference page for more information on the corresponding block function.

Connections **R**, **H _{A}**,
and

**H**are mechanical rotational conserving ports that represent the ring,

_{B}**R**, hub

*A*(

**H**), and hub

_{A}*B*(

**H**), respectively. Connection

_{B}**S**is a mechanical translational conserving port that represents the ring shifter handle.

Connections **X1** and **X2** are physical signal
ports that output the shift linkage positions of the dog clutches and cone clutches,
respectively. The tables provide the values of *X1* and
*X2* in common clutch engagement cases.

Dog Clutch State | X1 |
---|---|

Disengaged | 0 |

Fully engaged with hub A | Negative sum of ring-hub gap and tooth height |

Fully engaged with hub B | Positive sum of ring-hub gap and tooth height |

Cone Clutch State | X2 |
---|---|

Disengaged | 0 |

Fully engaged with hub A | Negative value of ring-hub gap |

Fully engaged with hub B | Positive value of ring-hub gap |

The values of *X1* and *X2* are zero when the
synchronizer is fully disengaged. When the dog clutch is fully engaged with hub
*A*, *X1* is equal to the negative sum of its
ring-hub gap and tooth height. When the dog clutch is fully engaged with hub
*B*, *X1* is equal to the positive sum of its
ring-hub gap and tooth height. When the cone clutch is fully engaged with hub
*A*, *X2* is equal to the negative of its ring-hub
gap. When the cone clutch is fully engaged with hub *B*,
*X2* is equal to its ring-hub gap.

### Dog Clutch Torque Transmission Models

You can choose from these torque transmission models.

**Friction Clutch Approximate Model**

When you set **Torque transmission model** to
```
Friction clutch approximation - Suitable for HIL
and
```

, the block treats the clutch engagement as a friction
phenomenon between the ring and the hub. This setting is better suited for
linearization, fixed-step simulation, and hardware-in-loop (HIL) simulation. The
block uses a composite implementation of the Fundamental Friction Clutch
block.

When you use this setting, the clutch has three possible configurations: disengaged, engaged, and locked. When disengaged, the contact force between the ring and the hub is zero. This force remains zero until the shift linkage reaches the minimum position for engagement.

When the ring-hub tooth overlap, *h*, exceeds the minimum
value for engagement, the contact force between the two components begins to
increase linearly with the shift linkage position, *z*.

At full engagement, the contact force reaches its maximum value and the clutch
state switches to locked. In this state, the ring and the hub spin as a unit
without slip. To unlock the clutch, the transmitted torque must exceed the value
of the **Maximum transmitted torque** parameter.

**Dynamic with Backlash**

When you set **Torque transmission model** to
`Dynamic with backlash`

, the block simulates clutch
phenomena such as backlash, torsional compliance, and contact forces between
ring and hub teeth. This model provides greater accuracy than the friction
clutch approximation.

When you use this setting, the clutch has two possible configurations: disengaged and engaged. When disengaged, the contact force between the ring and the hub is zero. This force remains zero until the shift linkage reaches the minimum position for engagement.

When the ring-hub tooth overlap, *h*, exceeds the engagement
threshold value, the clutch transmits torque. This torque is the sum of
torsional spring and damper components, including backlash between the ring and
hub teeth, such that$${T}_{C}=\{\begin{array}{cc}-{k}_{RH}\left(\varphi -\frac{\delta}{2}\right)-{\mu}_{R}\xb7\text{\hspace{0.17em}}\omega & \varphi >\frac{\delta}{2}\\ 0& -\frac{\delta}{2}<\varphi <\frac{\delta}{2}\\ -{k}_{RH}\left(\varphi +\frac{\delta}{2}\right)-{\mu}_{R}\omega & \varphi <-\frac{\delta}{2}\end{array},$$where:

*k*is the torsional stiffness of the ring-hub coupling._{RH}*ϕ*is the relative angle, about the common rotation axis, between the ring and the hub.*δ*is the backlash between ring and hub teeth.*ω*is the relative angular velocity between the ring and the hub. This variable describes how fast the two components slip past each other.

Compliant end stops limit the translational motion of the clutch shift linkage and the ring. The compliance model treats the end stops as linear spring-damper sets. The location of the end stops depends on the relative angle and angular velocity between the ring and hub teeth:

If the teeth align and the relative angular velocity is smaller than the maximum value for clutch engagement, the end stop location is the sum of the ring-hub clearance when fully disengaged and the tooth height. The clutch can engage in this end stop position.

If the teeth do not align or the relative angular velocity exceeds the maximum value for clutch engagement, the end-stop location is set to prevent the ring from engaging the hub. The clutch does not engage in this end stop position.

Translational friction opposes shift linkage and ring motion. This friction is the sum of Coulomb and viscous components, such that$${F}_{Z}=-{k}_{K}\xb7{F}_{N}\xb7\mathrm{tanh}\left(\frac{4v}{{v}_{th}}\right)-{\mu}_{T}v,$$where:

*F*is the net translational friction force acting on the shift linkage and ring._{Z}*k*is the kinetic friction coefficient between ring and hub teeth._{K}*F*is the normal force between ring and hub teeth, where_{N}*F*=_{N}*T*/_{C}*R*._{m}*v*is the translational velocity of the shift linkage and the ring.*v*is the translational velocity threshold. Below this threshold, a hyperbolic tangent function smooths the Coulomb friction force to zero as the shift linkage and ring velocity tends to zero._{th}*μ*is the viscous damping coefficient acting on the shift linkage and the ring._{T}

**Dynamic Modal**

When you set **Torque transmission model** to
`Dynamic modal`

, the block determines the discrete
clutch modal behavior by taking the shift linkage position from the mechanical
translational conserving port **S**. This setting captures more complex
clutch dynamics than the `Two-mode`

parameterization
and is faster than the `Friction clutch approximation`

and `Dynamic with backlash`

settings.

You can use the `Dynamic modal`

setting to simulate
engagement blocking when the speed difference is too large for the clutch plates
to engage. The block represents engagement blocking as a spring-damper system
where you can parameterize the spring and damping coefficients. The engagement
modes overlap, which prevents the mode from changing until the shift linkage
position is beyond the engagement overlap region. You define the engagement
overlap region using the **Tooth overlap to engage** parameter.

The linkage position constrains are:

*z*is the shift linkage position at port**S**.*h*is the**Tooth height**parameter.*z*is the_{Gap}**Ring hub clearance when disengaged**parameter.*z*is the_{Overlap}**Tooth overlap to engage**parameter.*ω*is the_{thr}**Engagement speed threshold**parameter.

The engagement mode positions are:

*z*= 0 — The clutch is fully disengaged.0 <

*z*<*z*— The clutch is disengaged when the shift linkage position is in the region defined by_{Gap}*z*. The clutch can transition from disengaged to engaged at_{Gap}*x*=*z*+_{Gap}*z*._{Overlap}*z*<_{Gap}*z*<*h*— The clutch is engaged when*z*is in the region defined by*h*. The clutch can transition from engaged to disengaged when*z*=*z*._{Gap}*z*=*z*+_{Gap}*h*— The clutch is fully engaged.*z*=*z*+_{Gap}*z*— When_{Overlap}*z*is in the engagement overlap region, the clutch engages only when the speed difference is less than the value of the*ω*parameter._{thr}

### Thermal Modeling

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, in the **Clutch** settings, select a
temperature-dependent setting tor the **Friction model** parameter.
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

### Output

### Conserving

## Parameters

## More About

## Extended Capabilities

## Version History

**Introduced in R2012b**