Torque Converter

R2026b

Torque converter coupling between two drive shafts

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Torque Converter block

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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.

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 the torque from the angular speed.

Use modal coast mode modeling

When you set Coast mode modeling to Two mode, the block uses separate modes for coasting and driving. The block computes the torque from the 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 ω_T and ω_I represent the speeds at ports T and I, respectively. When in coast mode, the block defines the speed ratio as

$${\widehat{R}}_{\omega }={\omega }_I/{\omega }_T.$$

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

You can optionally include dampers,inertias, and lock-up clutch behavior.

Dampers and Inertias

When you select Enable dampers and inertias, the block uses a subcomponent implementation of Damper and Inertia blocks for both the impeller and turbine sides of the torque converter. The figure illustrates the implementation.

You can use the parameters in the Dampers and Inertias section to modify the damper and inertia for the two sides of the torque converter.

Lock-Up Clutch

When you select Enable lock-up clutch, the block uses a subcomponent implementation of the Disc Friction Clutch block to simulate lock-up clutch behavior. The figure illustrates the implementation.

The block introduces a first-order delay to the lock-up clutch pressure port. This delay represents the clutch pressure dynamics. The block uses the input pressure, P_in, to find the clutch torque, such that

$${\tau }_{clutch}=(P_{in}-P_{min})AR,$$

where,

• P_min is the minimum pressure at which the clutch engages, specified by the Engagement threshold pressure parameter.

• A is the effective piston engagement area, specified by the Engagement piston area parameter.

• R is the effective torque radius, specified by the Effective torque radius parameter.

You can use port L to provide P_in as a physical signal. To parameterize the clutch and pressure dynamics, use the parameters associated with the subcomponent implementation under the Lock-up Clutch and Lock-up Clutch Pressure Dynamics sections in the block dialog box.

Use Continuous Coast Mode Modeling

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 $$K^{*}={\tau }_I/{\omega }^2$$.

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. The block introduces the lag and finds the steady state torque at port I such that

$$t_c(d{\tau }_I/dt)+{\tau }_I={\tau }_I(steadystate).$$

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

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.

Examples

Torque Converter in Two-Mode Modeling

Basic operations of a torque converter including lock-up clutch mechanism. You can select three different simulation cases - Basic Lock-up, Drive Mode Test, and Coast Mode Test.

• Open Model

Vehicle with Four-Speed Transmission

A complete vehicle with Simscape™ Driveline™ components, including the engine, drivetrain, four-speed transmission, tires, and longitudinal vehicle dynamics. The transmission controller is implemented as a state machine in Stateflow®, selecting the gear based on throttle and vehicle speed.

• Open Model

Vehicle with Four-Wheel Drive

A four-wheel drive vehicle starting from rest and ascending a 15 degree incline. Initially the vehicle rolls backward until the engine develops sufficient torque to counter the slope. The tire compliance dynamics can be seen as the vehicle starts to accelerate. The model variant chosen for all of the tires can be set to the Simple, Friction Parameterized, or Magic Formula tire model using the hyperlinks in the model.

• Open Model

Ports

Input

L — Lock-up clutch pressure, Pa

physical signal input

Physical signal input port associated with the lock-up clutch pressure, in Pa.

Dependencies

To enable this port, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Conserving

I — Impeller

mechanical rotational

Mechanical rotational conserving port associated with the impeller.

Programmatic Use

Port: I

T — Turbine

mechanical rotational

Mechanical rotational conserving port associated with turbine.

Programmatic Use

Port: T

Parameters

Torque Characteristics

Coast mode modeling — Coast transition simulation option

Two-mode (default) | Continuous

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.

Programmatic Use

Parameter:	coast_mode_modeling
Values:	"sdl.enum.torqueConverterContinuousTwomode.twomode" | "sdl.enum.torqueConverterContinuousTwomode.continuous"

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, 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.

Programmatic Use

Parameter: SR_drive_tlu

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. 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.

Programmatic Use

Parameter: TR_drive_tlu

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. 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.

Programmatic Use

Parameter: CF_drive_tlu

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

$${\widehat{R}}_{\omega }={\omega }_I/{\omega }_T$$

Dependencies

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

Programmatic Use

Parameter: SR_coast_tlu

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

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

Dependencies

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

Programmatic Use

Parameter: CF_coast_tlu

Initial mode — Initial mode of simulation

Drive mode (default) | Coast 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.

Programmatic Use

Parameter:	iniMode
Values:	"sdl.enum.torqueConverterInitialMode.drive" | "sdl.enum.torqueConverterInitialMode.coast"

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 high-frequency mode switching.

Dependencies

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

Programmatic Use

Parameter: delta_w

Speed ratio vector — Turbine speed to impeller speed ratios

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

Speed ratios, $$R_{\omega }$$, of the torque converter. Each element of the vector must be in ascending order and nonnegative. The block defines the speed ratio as $$R_{\omega }={\omega }_T/{\omega }_I$$. If R_ω exceeds the last element, the block extrapolates according to the Extrapolation method parameter.

Dependencies

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

Programmatic Use

Parameter: n_vector

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 of ascending positive elements

Torque ratios, $$R_{\tau }$$, of the torque converter. Each element of the vector must be positive. The block defines the torque ratio as $$R_{\tau }={\tau }_T/{\tau }_I$$. If R_ω exceeds the last element of the Speed ratio vector parameter, the block extrapolates according to the Extrapolation method parameter.

Dependencies

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

Programmatic Use

Parameter: trq_vector

Capacity factor parameterization — Capacity factor definition

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

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.

Programmatic Use

Parameter:	cf_vector_parameterization
Values:	"sdl.enum.torqueConverterCFParameterization.SpeedToSqrtTorque" | "sdl.enum.torqueConverterCFParameterization.TorqueToSqrSpeed"

Capacity factor reference speed — Capacity factor reference speed option

Always impeller speed (default) | Turbine speed for speed ratios greater than one

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.

Programmatic Use

Parameter:	cf_vector_reference_speed
Values:	"sdl.enum.torqueConverterCFReferenceSpeed.ImpellerSpeedAlways" | "sdl.enum.torqueConverterCFReferenceSpeed.ImpellerSpeedLessThanOne"

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/(N^(1/2)*m^(1/2)*s) (default) | vector

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

Dependencies

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

Programmatic Use

Parameter: cf_vector

Parameter: cf_vector_sq

Dampers and Inertias

Enable dampers and inertias — Option to enable dampers and inertias

off (default) | on

Option to include the effect of damping and inertia in the block.

Dependencies

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

Programmatic Use

Parameter:	use_dampers_inertias
Values:	"true" | "false"

Impeller inertia — Impeller inertia

0.001 kg*m^2 (default) | positive scalar

Inertia of the impeller.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable dampers and inertias.

Programmatic Use

Parameter: J_imp

Initial impeller speed — Initial impeller speed

0 rad/s (default) | nonnegative scalar

Speed of the impeller at the start of the simulation.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable dampers and inertias.

Programmatic Use

Parameter: w0_imp

Impeller damping coefficient — Impeller damping coefficient

0.001 N*m/rpm (default) | positive scalar

Damping coefficient of the impeller.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable dampers and inertias.

Programmatic Use

Parameter: D_imp

Turbine inertia — Turbine inertia

0.001 kg*m^2 (default) | positive scalar

Inertia of the turbine.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable dampers and inertias.

Programmatic Use

Parameter: J_tur

Initial turbine speed — Initial turbine speed

0 rad/s (default) | nonnegative scalar

Speed of the turbine at the start of the simulation.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable dampers and inertias.

Programmatic Use

Parameter: w0_tur

Turbine damping coefficient — Turbine damping coefficient

0.001 N*m/rpm (default) | positive scalar

Damping coefficient of the turbine.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable dampers and inertias.

Programmatic Use

Parameter: D_tur

Lock-up Clutch

Enable lock-up clutch — Option to enable lock-up clutch behavior

off (default) | on

Option to enable lock-up clutch behavior in the block.

Dependencies

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

Programmatic Use

Parameter:	use_lockup
Values:	"true" | "false"

Effective torque radius — Effective torque radius

130 mm (default) | positive scalar

Effective moment arm radius, R, that determines the kinetic friction torque inside the clutch.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: r_eff

Engagement piston area — Piston effective area

0.001 m^2 (default) | positive scalar

Effective area of the clutch piston when the piston applies pressure across the clutch, A.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: piston_area

Static friction coefficient — Static friction coefficient

0.35 (default) | positive scalar

Friction coefficient of the clutch when not in motion.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: mu_static

Kinetic friction coefficient — Kinetic friction coefficient

0.3 (default) | positive scalar

Friction coefficient of the clutch when in motion.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: mu_coulomb

Clutch velocity tolerance — Threshold velocity for clutch friction

0.001 rad/s (default) | positive scalar

Maximum slip velocity at which the clutch can lock. The slip velocity is the signed difference between the base and follower shaft angular velocities of the clutch. If the kinetic friction torque is nonzero and the transferred torque is within the static friction torque limits, then the clutch locks if the slip velocity falls below the velocity tolerance.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: w_tol

Engagement threshold pressure — Normal contact force threshold

100 Pa (default) | positive scalar

Minimum pressure at which the clutch engages, P_min. If the pressure input signal falls below this threshold, the clutch disengages.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: pressure_min

Initial lock-up state — Initial clutch state

Unlocked (default) | Locked

Clutch state at the start of the simulation.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter:	initial_state_locked
Values:	"sdl.enum.initial_lock.unlocked" | "sdl.enum.initial_lock.locked"

Lock-up Clutch Pressure Dynamics

Lag time constant — Clutch lag

0.1 s (default) | positive scalar

Time constant for the clutch lag.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: T_clutch

Initial lock-up clutch pressure — Initial lock-up pressure

0 kPa (default) | nonnegative scalar

Lock-up clutch pressure at the start of the simulation.

Dependencies

To enable this parameter, set Coast mode modeling to Two-mode and select Enable lock-up clutch.

Programmatic Use

Parameter: P0_lockup

Dynamics

Model transmission lag — Transmission lag setting

No lag – Suitable for HIL simulation (default) | Specify time constant and initial value

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:

  $${\tau }_I=\mathrm{sgn}(1-{\omega }_T/{\omega }_I){({\omega }_I/K)}^2$$

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

• 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.

Dependencies

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

Programmatic Use

Parameter:	model_lag
Values:	"sdl.enum.torqueConverterLagOnOff.LagOn" | "sdl.enum.torqueConverterLagOnOff.LagOff"

Torque transmission time constant — Time constant of torque transmission

.02 s (default) | positive scalar

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.

Programmatic Use

Parameter: tau

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

0 (default) | nonnegative scalar

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.

Programmatic Use

Parameter: initial_trq_ratio

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 in the definition range. For more information about Linear and Smooth, see tablelookup.

Programmatic Use

Parameter:	interp_method
Values:	"simscape.enum.interpolation.linear" | "simscape.enum.interpolation.smooth"

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, see tablelookup.

Programmatic Use

Parameter:	extrap_method
Values:	"simscape.enum.extrapolation.linear" | "simscape.enum.extrapolation.nearest" | "simscape.enum.extrapolation.error"

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

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Version History

Introduced in R2011a

R2026b: Model damping and inertia

To model damping and inertia, select the Enable dampers and inertias parameter.

R2026b: Model lock-up clutch behavior

To model lock-up clutch behavior, select the Enable lock-up clutch parameter.

R2020b: Simulate coast mode with mode charts

To use mode charts to improve simulation robustness during mode transitions, set Coast mode modeling to Two-mode.