# Torque Converter

Viscous fluid coupling between rotating driveline shafts

**Libraries:**

Simscape /
Driveline /
Couplings & Drives

## Description

The Torque Converter block models a torque converter. The
Torque Converter block has two mechanical rotational
conserving ports that are associated with the impeller and turbine, respectively. The block
transfers torque and angular velocity between the impeller port **I** and
turbine port **T** by acting as a lookup table. The block can simulate drive
(power flows from **I** port to **T** port) and coast (power
flows from **T** port to **I** port) modes.

## Examples

## Limitations

When **Coast mode modeling** is set to
`Continuous`

:

The impeller shaft must always rotate in a positive direction. Simulation is not valid for $${\omega}_{I}$$ < 0.

If you drive the Torque Converter block by using a torque source, such as the Generic Engine block, you must include an inertia in the source to represent the engine, shaft inertia, or other source components. To ensure that the impeller starts by rotating in a positive direction, set the initial speed for this inertia to a positive value.

## Ports

### Conserving

**I** — Impeller

mechanical rotational

Mechanical rotational conserving port associated with the impeller.

**T** — Turbine

mechanical rotational

Mechanical rotational conserving port associated with turbine.

## Parameters

### Torque Characteristics

**Coast mode modeling** — Modeling type of torque converter

`Two-mode`

(default) | `Continuous`

Modeling type of the torque converter specified as either
`Two-mode`

or `Continuous`

. The
`Continuous`

modeling type supports both drive and coast
modes but has reduced accuracy and robustness when modeling near the transition
between coasting and driving modes. Therefore, if the simulation involves a coast
mode, use the `Two-mode`

modeling type due to its better
robustness and accuracy when modeling the coast mode.

**Drive mode speed ratio vector** — Turbine speed to impeller speed ratios

[0, .5, .6, .7, .8, .87, .92, .94, .96, .97, 1] (default) | vector

Speed ratios, $${R}_{\omega}$$, of the drive mode. The vector elements must be in ascending order starting at 0 and ending at 1.

$${R}_{\omega}={\omega}_{T}/{\omega}_{I}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Two-mode`

.

**Drive mode torque ratio vector** — Turbine torque to impeller torque ratios

[2.232, 1.5462, 1.4058, 1.2746, 1.1528, 1.0732, 1.0192, 1, 1, 1,
1] (default) | vector

Torque ratios, $${R}_{\tau}$$, of the drive mode. Each element of the vector must be greater than or equal to 1, and the last element must be 1.

$${R}_{\tau}={\tau}_{T}/{\tau}_{I}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Two-mode`

.

**Drive mode capacity factor vector** — Capacity factors of drive mode

1e-4 * [.72558, .66322, .63463, .59042, .51331, .4144, .29287,
.22444, .12186, .04386, 0] `m*N/rpm^2 `

(default) | vector

Capacity factors,$${K}^{*}$$, of the drive mode. Each element of the vector must be nonnegative, and the last element must be 0.

$${K}^{*}={\tau}_{I}/{\omega}_{I}^{2}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Two-mode`

.

**Coast mode speed ratio vector** — Impeller speed to turbine speed ratios

[0, .5, .6, .7, .8, .87, .92, .94, .96, .97, 1] (default) | vector

Speed ratios, $${\widehat{R}}_{\omega}$$, of the coast mode. The vector elements must be in ascending order starting at 0 and ending at 1.

$${\widehat{R}}_{\omega}={\omega}_{I}/{\omega}_{T}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Two-mode`

.

**Coast mode capacity factor vector** — Capacity factors of coast mode

1e-4 * [.5079, .4643, .4442, .4133, .3593, .2901, .205, .1571,
.0853, .0307, 0] `m*N/rpm^2 `

(default) | vector

Capacity factors, $${\widehat{K}}^{*}$$, of the coast mode. Each element of the vector must be nonnegative, and the last element must be 0.

$${\widehat{K}}^{*}={\tau}_{T}/{\omega}_{T}^{2}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Two-mode`

.

**Interpolation method** — Interpolation method of lookup function

`Linear`

(default) | `Smooth`

Interpolation method of the lookup function, specified as either
`Linear`

or `Smooth`

. The method
interpolates torque ratio and capacity factor functions between the discrete relative
velocity values within the definition range. For more information about
`Linear`

and `Smooth`

, see `tablelookup`

.

**Extrapolation method** — Extrapolation method of lookup function

`Linear`

(default) | `Nearest`

| `Error`

Extrapolation method of the lookup function, specified as
`Linear`

, `Smooth`

, or
`Error`

. The method extrapolates torque ratio and capacity
factor functions. For more information about `Linear`

,
`Smooth`

, and `Error`

, see `tablelookup`

.

**Initial mode** — Initial mode of simulation

`Drive mode`

(default) | `Coast mode`

Initial mode of the simulation, specified as either ```
Drive
mode
```

or `Coast mode`

.

**Mode transition threshold** — Threshold of mode transition

1 `rpm`

(default) | positive scalar

Mode transition threshold of the simulation. Setting a threshold for the mode transition can increase the simulation robustness by avoiding the high frequency mode switching.

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Two-mode`

.

**Speed ratio vector** — Turbine speed to impeller speed ratios

[0, .5, .6, .7, .8, .87, .92, .94, .96, .97] (default) | vector

Speed ratios, $${R}_{\omega}$$, of the torque converter. Each element of the vector must be in ascending order and in the range [0,1].

$${R}_{\omega}={\omega}_{T}/{\omega}_{I}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Continuous`

.

**Torque ratio vector** — Turbine torque to impeller torque ratios

[2.232, 1.5462, 1.4058, 1.2746, 1.1528, 1.0732, 1.0192, .9983,
.9983, .9983, .9983] (default) | vector

Torque ratios, $${R}_{\tau}$$, of the torque converter. Each element of the vector must be positive.

$${R}_{\tau}={\tau}_{T}/{\tau}_{I}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Continuous`

.

**Capacity factor parameterization** — Definition of capacity factor

```
Ratio of speed to square root of impeller
torque
```

(default) | `Ratio of impeller torque to square of speed`

Definition of the capacity factor of the converter, defined as either
`Ratio of speed to square root of impeller torque`

or
`Ratio of impeller torque to square of speed`

. The setting
of this parameter affects the **Capacity factor vector**.

For

`Ratio of speed to square root of impeller torque`

parameter:$$K=\omega /\sqrt{{\tau}_{I}}$$

For

`Ratio of impeller torque to square of speed`

parameter:$${K}^{*}={\tau}_{I}/{\omega}^{2}$$

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Continuous`

.

**Capacity factor reference speed** — Choice of speed for capacity factor definition

`Always impeller speed`

(default) | ```
Turbine speed for speed ratios greater than
one
```

Choice of speed for the capacity factor definition, specified as either
`Always impeller speed`

or ```
Turbine speed for
speed ratios greater than one
```

.

`Always impeller speed`

: Use impeller speed $${\omega}_{I}$$ for all values of $${R}_{\omega}$$.`Turbine speed for speed ratios greater than one`

: Use impeller speed $${\omega}_{I}$$ for all values of $${R}_{\omega}$$ < 1, and use turbine speed $${\omega}_{T}$$ when $${R}_{\omega}$$ > 1.

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Continuous`

.

**Capacity factor vector** — Capacity factors

[12.2938, 12.8588, 13.1452, 13.6285, 14.6163, 16.2675, 19.3503,
22.1046, 29.9986, 50] `(rad/s)/(N*m)^0.5`

(default) | vector

Capacity factors of the converter. You can define the capacity factor as:

**Capacity factor**

$$K=\omega /\sqrt{{\tau}_{I}}$$ | Set Capacity factor parameterization parameter to
```
Ratio of speed to square root of impeller
torque
``` . |

$${K}^{*}={\tau}_{I}/{\omega}^{2}$$ | Set Capacity factor parameterization parameter to
```
Ratio of impeller torque to the square of the
speed
``` . The default value is 1e-3 * [6.616, 6.048, 5.787,
5.384, 4.681, 3.779, 2.671, 2.047, 1.111, .4]
`N*m/(rad/s)^2` . |

**Note**

If you do not specify capacity factor data for a speed ratio of 1, the block
uses a capacity factor value of 10**K*_{Max}, where *K*_{Max} is the
maximum value in the specified capacity factor vector. The corresponding torque
ratio is assumed to be 0. For all other speed ratio values not explicitly
specified in the lookup table data, the block uses the interpolation or
extrapolation method selected in the block property inspector.

#### Dependencies

To enable this parameter, set **Coast mode modeling** to
`Continuous`

.

### Dynamics

To enable the **Dynamics**, set the **Coast mode
modeling** parameter to `Continuous`

.

**Model transmission lag** — Transmission lag setting

```
No lag – Suitable for HIL
simulation
```

(default) | `Specify time constant and initial value`

Transmission lag setting, specified as either ```
No lag – Suitable for
HIL simulation
```

or ```
Specify time constant and initial
value
```

.

`No lag – Suitable for HIL simulation`

: Torque transfer is instantaneous.When there is no time lag, the input impeller torque, $${\tau}_{I}$$, and output turbine torque, $${\tau}_{T}$$, are:

$${\tau}_{I}=\mathrm{sgn}(1-{\omega}_{T}/{\omega}_{I}){({\omega}_{I}/K)}^{2}$$

$${\tau}_{T}={\tau}_{T}{R}_{\tau}$$

`Specify time constant and initial value`

: Torque is transferred with a time lag. If you select this option, you can specify the**Torque transmission time constant**and**Initial turbine-to-impeller torque ratio**parameters.**Note**For optimal simulation performance, select

`No lag - Suitable for HIL simulation`

.

**Torque transmission time constant** — Time constant of torque transmission

.02 `s`

(default) | positive scalar

Torque transmission time. The time lag increases model fidelity but reduces simulation performance. See Adjust Model Fidelity for more information.

#### Dependencies

To enable this parameter, set **Model transmission lag** to
`Specify time constant and initial value`

.

**Initial turbine-to-impeller torque ratio** — Initial torque ratio of turbine to impeller

0 (default) | positive scalar

Initial torque ratio of the turbine to the impeller.

You can optionally include the effect of torque transmission time lag that is caused by internal fluid flow and compressibility. Instead of $${\tau}_{T}$$ and $${\tau}_{I}$$ being instantaneously constrained to one another, a first-order time lag introduces a delayed response in the impeller torque:

$${t}_{c}(d{\tau}_{I}/dt)+{\tau}_{I}={\tau}_{I}(steadystate)$$

The preceding instantaneous function of the capacity factor *K*
determines the steady-state value of
*τ*_{I}.

#### Dependencies

To enable this parameter, set **Model transmission lag** to
`Specify time constant and initial value`

.

## References

[1] Society of Automotive Engineers, *Hydrodynamic Drive
Test Code (Surface Vehicle Recommended Practice),* SAE J643, Dec
2018.

## Extended Capabilities

### C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

## Version History

**Introduced in R2011a**

## See Also

### Simscape Blocks

### Topics

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