Torque Converter

Torque converter coupling between two drive shafts

Libraries:
Simscape / Driveline / Couplings & Drives

Description

The Torque Converter block represents an automotive torque converter that comprises an impeller, a turbine, and a stator. The impeller and the turbine make up the fluid coupling, and the stator increases torque by redirecting the flow returning to the impeller. As the shaft turns the impeller, centrifugal force flings the fluid outward toward the turbine blades, which causes the turbine to spin as the fluid proceeds to the center and out toward the stator. Use the block to connect an engine to an automatic transmission. Connect port I to the engine and port T to the transmission.

By default, the block constrains ${\tau }_{T}$, the torque at port T, and ${\tau }_{I}$, the torque at port I, to one another for a given time step. You can optionally include the effect of torque transmission time lag that is caused by internal fluid flow and compressibility. To include transmission lag, set Model transmission lag to ```Specify time constant and initial value```. The block introduces the lag and finds the steady state torque at port I such that

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

The instantaneous function of the capacity factor K determines the steady-state value of τI. The block operates in drive mode when power flows from port I to port T. The block operates in coast mode when power flows in reverse. You can simulate the coast mode transition continuously or by using mode charts. The block uses the capacity factor for the torque converter to calculate torque from angular speed.

Two Mode Coast Transition

When you set Coast mode modeling to ```Two mode```, the block uses separate modes for coasting or driving. The block computes the torque from angular speed such that

`$\tau ={K}^{*}{\omega }^{2},$`

where K* is the Drive mode capacity factor vector parameter and ω is the angular speed for either port I or port T. The capacity factor is a function of the speed ratio. When in drive mode, the block defines the speed ratio as

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

where ωT and ωI represent the speeds at ports T and I, respectively. When in coast mode, the block defines the speed ratio as

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

Because of the different speed ratio definitions, the block also uses a separate capacity factor for the coast mode, ${\stackrel{^}{K}}^{*}$, which is the Coast mode capacity factor vector parameter. The Mode transition parameter determines the speed at which the block changes modes. The graphic illustrates the two modes.

Continuous Coast Transition

When you set Coast mode modeling to `Continuous`, the block smoothly transitions between drive and coast mode. You can also add dynamics. The block simulation is less accurate when operating near the transition region.

The block defines the speed ratio as ${R}_{\omega }={\omega }_{T}/{\omega }_{I}$ and the torque ratio as ${R}_{\tau }={\tau }_{T}/{\tau }_{I}$. The Capacity factor parameterization parameter controls how the block defines the capacity factor. When you select:

• `Ratio of speed to square root of impeller torque`, the block uses $K=\omega /\sqrt{{\tau }_{I}}$.

• `Ratio of impeller torque to square of speed`, the block uses ${K}^{*}={\tau }_{I}/{\omega }^{2}$.

To improve fidelity, you can include lag due to the transmission in your simulation. When you set Model transmission lag to `Specify time constant and initial value`, the block adds a constant time delay to the torque transfer.

When you set Coast mode modeling 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

Coast mode transition method. When you select `Continuous`, the block smoothly transitions between drive and coast mode but has reduced accuracy and robustness when modeling near the transition. When you select `Two-mode`, the block uses mode charts, which promote better robustness and accuracy when the mode transitions.

Speed ratios, ${R}_{\omega }$, of the drive mode. The vector elements must be in ascending order, start at 0, and end 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. The block defines the torque ratio of the drive mode as:

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

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. The block defines the capacity factory of the drive mode as:

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

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, start at 0, and end at 1. The block defines the speed ratio of the coast mode as:

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

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. The block defines the capacity factor of the coast mode as:

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

Dependencies

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

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

Dependencies

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

Mode transition threshold of the simulation. Setting a threshold for the mode transition can increase the simulation robustness by avoiding 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]. The block defines the speed ratio as ${R}_{\omega }={\omega }_{T}/{\omega }_{I}$.

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. The block defines the torque ratio as ${R}_{\tau }={\tau }_{T}/{\tau }_{I}$.

Dependencies

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

Definition of the capacity factor.

```Ratio of speed to square root of impeller torque``````Ratio of impeller torque to the square of the speed```
`$K=\omega /\sqrt{{\tau }_{I}}$`
`${K}^{*}={\tau }_{I}/{\omega }^{2}$`

When you select ```Ratio of impeller torque to square of 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`.

Dependencies

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

Whether to always use the impeller speed as the reference speed or to use the turbine speed when speed ratios are 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 torque converter. The block defines the capacity factor according to the table:

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 specified by the Interpolation method or Extrapolation method parameter, respectively.

Dependencies

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

Dynamics

To enable these parameters, set Coast mode modeling parameter to `Continuous`

Whether to include transmission lag in the simulation. When you select:

• `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`, the block transfers torque 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.

Torque transmission time. The time lag increases model fidelity and computational cost. 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.

Dependencies

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

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 in 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, see `tablelookup`.

References

[1] Society of Automotive Engineers. "Hydrodynamic Drive Test Code (Surface Vehicle Recommended Practice)." SAE J643. (December 2018) https://doi.org/10.4271/J643_201812

Version History

Introduced in R2011a

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