# Torque Converter

Viscous fluid coupling between rotating driveline shafts

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• 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.

## 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

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Mechanical rotational conserving port associated with the impeller.

Mechanical rotational conserving port associated with turbine.

## Parameters

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### Torque Characteristics

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.

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`.

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`.

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`.

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

`${\stackrel{^}{R}}_{\omega }={\omega }_{I}/{\omega }_{T}$`

#### Dependencies

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

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

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

#### Dependencies

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

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 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 of the simulation, specified as either ```Drive mode``` or `Coast mode`.

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 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 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`.

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`.

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 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*KMax, where KMax 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`.

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:

`${\tau }_{I}=\mathrm{sgn}\left(1-{\omega }_{T}/{\omega }_{I}\right){\left({\omega }_{I}/K\right)}^{2}$`
`${\tau }_{T}={\tau }_{T}{R}_{\tau }$`
• `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. 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 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:

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

The preceding instantaneous function of the capacity factor K determines the steady-state value of τI.

#### 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.

## Version History

Introduced in R2011a