# Simple Gear with Variable Efficiency

Gear set with parallel-axis rotation and variable meshing efficiency

**Library:**Simscape / Driveline / Gears

## Description

The block represents a simple gear train with variable meshing efficiency. The gear train transmits torque at a specified ratio between base and follower shafts arranged in a parallel configuration. Shaft rotation can occur in equal or opposite directions. Gear losses are optional. They include meshing and viscous bearing losses. To specify the variable meshing efficiency, the block contains a physical signal port that you can use to input a general time-varying signal. Inertia and compliance effects are ignored.

### Simple Gear Model

**Ideal Gear Constraint and Gear Ratio**

Simple Gear imposes one kinematic constraint on the two connected axes:

r_{F}ω_{F}
=
r_{B}ω_{B}
. | (1) |

The follower-base gear ratio
*g*_{FB} =
*r*_{F}/*r*_{B}
=
*N*_{F}/*N*_{B}.
*N* is the number of teeth on each
gear. The two degrees of freedom reduce to one independent
degree of freedom.

The torque transfer is:

g_{FB}τ_{B}
+ τ_{F} –
τ_{loss} =
0 , | (2) |

with *τ*_{loss}
= 0 in the ideal case.

### Nonideal Gear Constraint and Losses

In the nonideal case, *τ*_{loss}
≠ 0. For general considerations on nonideal gear
modeling, see Model Gears with Losses.

### Thermal Model

You can model
the effects of heat flow and temperature change by enabling the optional thermal port. To enable
the port, set **Friction model** to ```
Temperature-dependent
efficiency
```

.

### Variables

Use the **Variables** settings to set the priority and initial target
values for the block variables before simulating. For more information, see Set Priority and Initial Target for Block Variables.

## Limitations

Gear inertia is assumed to be negligible.

Gears are treated as rigid components.

Coulomb friction slows down simulation. For more information, see Adjust Model Fidelity.

## Ports

Port | Description |
---|---|

B | Rotational conserving port representing the base shaft |

F | Rotational conserving port representing the follower shaft |

H | Thermal conserving port for thermal modeling |

## Parameters

## Extended Capabilities

**Introduced in R2013a**