JP2009213267A - Vehicle driving unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle driving unit which can improve the operation efficiency of a motor after start of an internal combustion engine. <P>SOLUTION: The vehicle drive controller includes: a permanent magnet field type of motor, which has the first rotor and the second rotor provided concentrically around a rotating shaft; an internal combustion engine, which is coupled with the motor and generates motive power for a vehicle to run; and a control unit, which controls the relative displacement angle between the first rotor and the second rotor of the motor, according to the state of the internal combustion engine. The control unit controls the relative displacement angle so that it may lead an angle at which the induced voltage constant of the motor becomes max, after start of the internal combustion engine by the motor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle drive apparatus in which a permanent magnet field type electric motor including a first rotor and a second rotor provided concentrically around a rotating shaft is used for starting and generating electric power of an internal combustion engine.

  In the vehicle drive device disclosed in Patent Document 1, as shown in FIG. 10, a motor / generator (M / G) 3, an engine (E / G) 1, and an auxiliary machine (power steering pump 11, air conditioner compressor) 16) is connected by pulleys 9, 14, 22, 23 and a belt 8, and an electromagnetic clutch 26 for switching between transmission and non-transmission of power is provided between the motor / generator 3 and the engine 1. The motor / generator 3 is connected to a battery 5 via an inverter 4. In the state where the engine 1 is stopped when the vehicle in the eco-run mode is stopped, this vehicle drive device disengages the electromagnetic clutch 26 so that the pulley 22 and the engine 1 are not in the power transmission state. Power is supplied.

  In this way, when idling is stopped when the engine 1 is stopped when the vehicle is stopped, the driving force of the motor / generator 3 is not transmitted to the engine 1, so the power consumption of the motor / generator 3 for rotating the engine 1 is reduced. Can be reduced. Therefore, according to the vehicle drive device, it is possible to drive the auxiliary machine by the motor / generator 3 when the vehicle is stopped with low power. When the engine is started, the electromagnetic clutch 26 is in a connected state, and the engine 1 is started by power from the motor / generator 3. Further, after the engine is started, the motor / generator 3 functions as a generator that converts the regenerative energy of the vehicle into electricity, and can store the electric energy in the battery 5.

Japanese Patent Laid-Open No. 11-147424 JP 2002-204541 A JP 2007-159219 A

  In the vehicle drive device described above, the electromagnetic clutch 26 remains in the connected state even after the engine is started, so that the rotor 42 of the motor / generator 3 is rotated according to the rotation of the engine 1. However, since the motor / generator 3 does not have an output characteristic variable mechanism, an electromagnetic loss for rotating the rotor 42 occurs when the motor / generator 3 is neither driven nor regenerated after the engine is started. .

  Further, when the rotor 42 is rotated by the rotation of the engine 1, an induced voltage is generated in the motor / generator 3. However, when the rotational speed of the engine 1 is increased, the induced voltage is also increased. Since the induced voltage exceeding the withstand voltage of the inverter 4 causes a failure of the inverter 4, the motor / generator 3 needs to have field weakening control. The field weakening control is performed by supplying a field weakening current from the battery 5 to the motor / generator 3, but the supply of the field weakening current hinders reduction of power consumption.

For this reason, a method of using the permanent magnet rotating motor described in Patent Document 2 as the motor / generator 3 is conceivable. The permanent magnet rotating motor described in Patent Document 2 is provided concentrically with the rotor so as to surround the first and second rotors concentrically provided around the rotation shaft of the motor, and these rotors. And a field weakening control device for controlling the phase difference between the first and second rotors. However, since the field weakening control device controls the phase difference between the first and second rotors according to the rotational speed or centrifugal force of the electric motor, there is a high possibility that accurate control according to the state cannot be performed.

  The objective of this invention is providing the vehicle drive device which can improve the operating efficiency of the electric motor after an internal combustion engine starts.

  In order to solve the above problems and achieve the object, the vehicle drive device according to the first aspect of the present invention is provided concentrically around the rotation shaft (for example, the rotation shaft 53 in the embodiment). Permanent magnet field motor (eg, in the embodiment) having a first rotor (eg, outer rotor 52 in the embodiment) and a second rotor (eg, inner rotor 51 in the embodiment). An electric motor 103), an internal combustion engine (for example, the internal combustion engine 101 in the embodiment) connected to the electric motor, which generates power for driving the vehicle, and the electric motor according to the state of the internal combustion engine. A control unit (for example, a controller 119 in the embodiment) for controlling a relative displacement angle (for example, a rotor phase difference in the embodiment) of the first rotor and the second rotor, and the control Part is the electric motor After the start of the combustion engine, the relative displacement angle induced voltage constant of the motor is characterized by controlling so as to advance than the angle of maximum.

  Furthermore, in the vehicle drive device of the invention according to claim 2, when the internal combustion engine stops idling, there is a drive request for an auxiliary machine mounted on the vehicle (for example, auxiliary machine 121 in the embodiment). The control unit controls the relative displacement angle to be advanced from an angle at which an induced voltage constant of the electric motor becomes maximum, and to supply current to the electric motor.

  Furthermore, in the vehicle drive device of the invention according to claim 3, the motor in which the relative displacement angle is advanced from an angle at which the induced voltage constant of the motor is maximized is requested to be mounted on the vehicle. It is characterized in that it generates more than the power required by the auxiliary equipment and supplies power to the auxiliary equipment.

  Further, in the vehicle drive device of the invention according to claim 4, when the internal combustion engine is not idling stopped, when there is no drive request for an auxiliary machine mounted on the vehicle, the control unit sets the relative displacement angle to the electric motor. Control is performed so that the induced voltage constant is set to an angle at which the constant is maximized.

  Furthermore, in the vehicle drive device of the invention according to claim 5, when the internal combustion engine is started by the electric motor, the control unit sets the relative displacement angle to an angle at which an induced voltage constant of the electric motor is maximized. It is characterized by control.

  Furthermore, in the vehicle drive device according to the sixth aspect of the present invention, the rotational speed detection unit (for example, the resolver 117 in the embodiment) that detects the rotational speed per unit time of the first rotor or the second rotor. And the controller 119), wherein the control unit is configured to output the electric motor based on an output torque of the electric motor that generates electric power or more required by the auxiliary machine requested to be driven and a rotational speed detected by the rotational speed detection unit. The relative displacement angle is controlled to be set to an angle at which the driving efficiency becomes the best.

  Furthermore, the vehicle drive apparatus according to the seventh aspect of the present invention includes a clutch (for example, the clutch 107 in the embodiment) that switches between transmission and non-transmission of power between the electric motor and the internal combustion engine, and the internal combustion engine. When idling is stopped, if there is a drive request for an auxiliary device mounted on the vehicle, the control unit controls to disengage the clutch.

  According to the vehicle drive device of the first to seventh aspects of the invention, since the relative displacement angle of the electric motor after the internal combustion engine is started is set to an angle with a small induced voltage constant, the electric motor operates efficiently. be able to. Therefore, the electric motor can efficiently generate the electric power supplied to the auxiliary machine for which driving is requested.

  According to the vehicle drive device of the invention described in claim 5, when starting the internal combustion engine, the relative displacement angle of the electric motor is set to an angle at which the induced voltage constant is maximized. Can be output.

  According to the seventh aspect of the present invention, since the clutch is disengaged when the internal combustion engine is idling, the internal combustion engine does not rotate due to the rotation of the electric motor. Therefore, the electric motor can be driven with low power.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a vehicle drive apparatus according to an embodiment of the present invention. 1 includes an internal combustion engine 101, an electric motor 103, an actuator 105, a clutch 107, a pulley 109, a belt 111, an inverter 113, a capacitor 115, a resolver 117, a controller 119, And an auxiliary machine 121 such as an air conditioner. The electric motor 103, the internal combustion engine 101, and the auxiliary machine are connected by a pulley 109 and a belt 111, and a clutch 107 that switches between transmission and non-transmission of power is provided between the electric motor 103 and the internal combustion engine 101. The motor 103 is connected to the battery 115 via the inverter 113. The controller 119 controls the clutch 107 and the actuator 105 according to the traveling state of the vehicle. The auxiliary machine 121 is driven by a low voltage of 12V, for example.

  Note that the idling of the internal combustion engine 101 is not performed when the vehicle on which the vehicle drive device of this embodiment is mounted stops. This is because fuel saving and exhaust gas reduction effects are expected by not performing idling of the internal combustion engine 101 when the vehicle is stopped.

  Hereinafter, the electric motor 103 with which the vehicle drive device of this embodiment is provided is demonstrated in detail with reference to drawings. The electric motor 103 is a permanent magnet field type electric motor that includes two rotors provided concentrically around the rotating shaft and performs field weakening control by changing the relative phase angle of the two rotors.

  FIG. 2 is a cross-sectional view of an electric motor included in the vehicle drive device shown in FIG. As shown in FIG. 2, the electric motor 103 includes an inner rotor 51 in which the fields of the permanent magnets 51a and 51b are arranged at equal intervals along the circumferential direction, and the fields of the permanent magnets 52a and 52b along the circumferential direction. And the stator 50 having an armature 50 a for generating a rotating magnetic field for the inner rotor 51 and the outer rotor 52.

  The inner rotor 51 and the outer rotor 52 are both arranged concentrically so that the rotating shaft is coaxial with the rotating shaft 53 of the electric motor 103. In the inner rotor 51, permanent magnets 51a having the N pole as the rotation shaft 53 side and permanent magnets 51b having the S pole as the rotation shaft 53 side are alternately arranged. Similarly, in the outer rotor 52, permanent magnets 52a having the N pole as the rotating shaft 53 side and permanent magnets 52b having the S pole as the rotating shaft 53 side are alternately arranged.

The phase difference between the outer rotor 52 and the inner rotor 51 (hereinafter referred to as “rotor phase difference”) can be changed to the advance side or the retard side at least within a range of 180 degrees in electrical angle. For this reason, the state of the electric motor 103 includes a field-enhanced state in which the permanent magnets 52 a and 52 b of the outer rotor 52 and the permanent magnets 51 a and 51 b of the inner rotor 51 are arranged opposite to each other, and a permanent state of the outer rotor 52. The magnets 52a and 52b and the permanent magnets 51a and 51b of the inner rotor 51 can be set as appropriate between the field weakening state in which the same poles are arranged to face each other.

  The rotor phase difference is changed by a rotor phase difference changing unit provided inside the electric motor 103. FIG. 3 is a diagram illustrating the internal structure of the rotor phase difference changing unit included in the electric motor 103. As shown in FIG. 3, the rotor phase difference changing unit 30 is a single pinion type planetary gear mechanism arranged in the hollow portion on the inner peripheral side of the inner rotor 51, and is formed coaxially and integrally with the outer rotor 52. The first ring gear R1, the second ring gear R2 that is coaxially and integrally formed with the inner rotor 51, the first planetary gear 31 that meshes with the first ring gear R1, and the second planetary gear 32 that meshes with the second ring gear R2. The first planetary gear 31 and the second planetary gear 32, the sun gear S that is an idle gear, and the first planetary carrier C 1 that rotatably supports the first planetary gear 31 and is rotatably supported by the rotation shaft 53. And a second planetary carrier C <b> 2 that rotatably supports the second planetary gear 32 and is fixed to the stator 50.

  The first ring gear R1 and the second ring gear R2 have substantially the same gear shape, and the first planetary gear 31 and the second planetary gear 32 also have substantially the same gear shape. The rotating shaft 33 of the sun gear S is arranged coaxially with the rotating shaft 53 of the electric motor 103 and is rotatably supported by a bearing 34. For this reason, the 1st planetary gear 31 and the 2nd planetary gear 32 mesh with the sun gear S, and the outer side rotor 52 and the inner side rotor 51 rotate in synchronization. Further, the rotation shaft 35 of the first planetary carrier C1 is disposed coaxially with the rotation shaft 53 of the electric motor 103 and is connected to the actuator 105, and the second planetary carrier C2 is fixed to the stator 50.

  In response to a control signal input from the controller 119, the actuator 105 rotates the first planetary carrier C1 in the forward rotation direction or the reverse rotation direction by hydraulic pressure, or restricts the rotation of the first planetary carrier C1 around the rotation shaft 53. . When the first planetary carrier C1 is rotated by the actuator 105, the relative positional relationship (phase difference) between the outer rotor 52 and the inner rotor 51 changes.

  FIG. 4 is a diagram showing a field strengthening state (a) and a field weakening state (b) of the electric motor 103. In the field-strengthened state shown in FIG. 4A, the direction of the magnetic flux Q2 of the permanent magnets 52a and 52b of the outer rotor 52 and the direction of the magnetic flux Q1 of the permanent magnets 51a and 51b of the inner rotor 51 are the same. Q3 is large. On the other hand, in the field weakening state shown in FIG. 4B, the directions of the magnetic flux Q2 of the permanent magnets 52a and 52b of the outer rotor 52 and the magnetic flux Q1 of the permanent magnets 51a and 51b of the inner rotor 51 are reversed. The magnetic flux Q3 is small.

  Thus, in the electric motor 103 having the double rotor, the induced voltage constant Ke can be changed by changing the rotor phase difference to increase or decrease the field magnetic flux. FIG. 5 is a diagram showing an operable region according to the rotation speed and torque of the electric motor 103 that changes according to the induced voltage constant Ke. As shown in FIG. 5, when the rotor phase difference is small and the induced voltage constant Ke is large (field strong state), the operable speed of the electric motor 103 decreases, but a large torque can be output. On the other hand, when the rotor phase difference is large and the induced voltage constant Ke is small (field weakening state), the torque that can be output from the electric motor 103 is reduced, but operation is possible up to a high rotational speed. As described above, the operable region of the electric motor 103 with respect to the rotation speed and torque changes according to the induced voltage constant Ke.

Note that the power generation characteristics of the electric motor 103 may include the power generation characteristics of a conventional ACG starter when the electric motor 103 is in a field weakened state. That is, the electric motor 103 is designed such that the output torque in the field weakened state is equal to or greater than the maximum torque of the ACG starter.

  In the present embodiment, the electric motor 103 described above has a role as a starter for starting the internal combustion engine 101 and a role as an AC generator (ACG) that generates electric power supplied to the auxiliary machine 121. The role as a starter is required when starting the internal combustion engine 101 from an idling stop state when the vehicle is stopped. At this time, the controller 119 places the clutch 107 in the connected state, and the output torque of the electric motor 103 rotates the internal combustion engine 101. In order to rotate the internal combustion engine 101, a relatively large torque is required.

  On the other hand, the role of ACG is required when there is a drive request for the auxiliary machine 121 regardless of whether the internal combustion engine 101 is driven. At this time, the controller 119 places the clutch 107 in the engaged state during the period from the start to the stop of the internal combustion engine 101 and when there is no auxiliary machine drive request when idling is stopped. When the clutch 107 is connected, the inner rotor 51 and the outer rotor 52 of the electric motor 103 are rotated with respect to the stator 50 by the rotation of the internal combustion engine 101, and thus generate electric power. The electric power generated by the electric motor 103 is supplied to the auxiliary machine requested to be driven when there is an auxiliary machine drive request, and charged to the capacitor 115 when there is no auxiliary machine drive request. Further, the controller 119 disengages the clutch 107 when there is an accessory drive request when idling is stopped. At this time, the electric motor 103 generates power by supplying power from the battery 115. The electric power generated by the electric motor 103 is supplied to the auxiliary machine for which driving is requested. The output torque of the electric motor 103 is set according to the sum of the input voltages of the auxiliary machines that are requested to be driven. However, since the input voltage of the auxiliary machine 121 is a relatively low voltage of 12 V, the output torque of the electric motor 103 may be small when the number of auxiliary machines requested to be driven is small.

  Thus, the output torque required for the electric motor 103 is different when the electric motor 103 operates as a starter and when it operates as an ACG. FIG. 6 is a diagram illustrating a rotor phase difference at which the operating range of the electric motor 103 and the operating efficiency of the electric motor 103 are optimized. As described above, when the electric motor 103 operates as a starter, a relatively large output torque is required. Therefore, the electric motor 103 is driven at a high torque and a low rotation speed by supplying current from the capacitor 115, and the rotor phase difference. Is set to 0 degrees by adjusting the actuator 105 by the controller 119. That is, the electric motor 103 is set to the field strongest state having the largest induced voltage constant Ke. On the other hand, since the output torque when the electric motor 103 operates as ACG may be small, the electric motor 103 is driven with a low torque, and the rotor phase difference is adjusted to 100 to 180 by adjusting the actuator 105 by the controller 119 according to the rotational speed. Set to an optimal value between degrees. That is, the electric motor 103 is set to a field weakening state in which the induced voltage constant Ke is small. The rotation speed of the electric motor 103 is obtained from the mechanical angle of the outer rotor 12 detected by the resolver 117.

  Next, control of the engine 103 and the clutch 107 according to the running state of the vehicle will be described. FIG. 7 is a diagram showing an induced voltage constant and a rotor phase difference set in the electric motor 103 according to the traveling state of the vehicle, and the state of the clutch 107. As shown in FIG. 7, the controller 119 provided in the vehicle drive device of the present embodiment includes three controllers, that is, when the internal combustion engine 101 is started, when the vehicle is accelerated, cruised, decelerated, the internal combustion engine 101 is stopped, and when idling is stopped. The rotor phase difference of the electric motor 103 and the clutch 107 are controlled according to the state.

FIG. 8 is a flowchart showing an operation performed by the controller 119 when the internal combustion engine 101 is started. As shown in FIG. 8, the controller 119 determines whether or not there is a request for starting the internal combustion engine 101 (step S101). If there is a start request for the internal combustion engine 101, the process proceeds to step S103. The controller 119 outputs a command for setting the clutch 107 in a connected state (step S103), and outputs a command for setting the rotor phase difference of the electric motor 103 to the most retarded angle (0 degree) (step S105). Next, a current is supplied from the capacitor 115 to the electric motor 103 so that the electric motor 10
The internal combustion engine is started by driving 3 (step S107). The controller 119 determines whether the internal combustion engine 101 has been started (step S109), and advances the rotor phase difference of the electric motor 103.

  FIG. 9 is a flowchart showing an operation performed by the controller 119 when the idling of the internal combustion engine 101 is stopped. As shown in FIG. 9, the controller 119 determines whether the internal combustion engine 101 has stopped idling (step S201). If the idling is stopped, the controller 119 proceeds to step S203. The controller 119 determines whether or not there is an auxiliary machine drive request (step S203). If there is no auxiliary machine drive request, the process proceeds to step S205, and if there is an auxiliary machine drive request, the process proceeds to step S209. When there is no auxiliary machine drive request, the controller 119 outputs a command to set the clutch 107 in a connected state (step S205), and outputs a command to set the rotor phase difference of the electric motor 103 to the most retarded angle (0 degree) ( Step S207). After step S207, the electric motor 103 stands by until the internal combustion engine 101 is started in a state where no current is supplied.

  On the other hand, when there is an auxiliary machine drive request, the controller 119 outputs a command to disengage the clutch 107 (step S209), and outputs a command to set the rotor phase difference of the electric motor 103 to an advance angle (100 to 180 degrees) ( Step S211). Next, electric power obtained by driving the electric motor 103 by supplying a current from the battery 115 to the electric motor 103 is supplied to the auxiliary machine requested to be driven (step S213).

  As described above, according to the vehicle drive device of the present embodiment, the rotor phase difference is set to the most retarded angle (0 degree) so that the electric motor 103 can output a large torque when the internal combustion engine 101 is started. Since a large torque is not required in the state where there is a drive request, the rotor phase difference is advanced in accordance with the torque required for driving the accessory and the rotational speed. As described above, the electric motor 103 used in the present embodiment has a double rotor, and based on the graph shown in FIG. 6, by changing the relative phase angle of the double rotor according to the torque and the rotational speed, There is no need to supply field weakening current to the motor 103. Therefore, the electric motor 103 outputs a high torque when the engine is started, and the rotor phase difference is advanced after the engine is started, so that the motor 103 can be operated efficiently.

  In the above embodiment, the internal combustion engine 101 and the electric motor 103 are connected via the clutch 107, but the internal combustion engine 101 and the electric motor 103 may be always connected without providing the clutch 107. However, in this configuration, when there is an auxiliary machine drive request when idling of the internal combustion engine 101 is stopped, the electric motor 103 is rotated by supplying current from the capacitor 115 to supply electric power to the auxiliary machine 121, but by the rotation of the electric motor 103 The internal combustion engine 101 is also rotated. Therefore, the electric motor 103 needs to output torque for rotating the internal combustion engine 101 in addition to torque necessary for generating electric power supplied to the auxiliary machine 121. As a result, the electric motor 103 cannot be driven with low power.

  In the above embodiment, the rotor phase difference in the strongest field state having the largest induced voltage constant Ke has been described as 0 degree. However, in consideration of manufacturing variations of the motor 103, the rotor phase difference is −10 to +10. The range of degrees may be regarded as the field strongest state.

The block diagram which shows the vehicle drive device of one Embodiment which concerns on this invention. Sectional drawing of the electric motor with which the vehicle drive device shown in FIG. The figure which shows the internal structure of the rotor phase difference change part which the electric motor 103 has The figure which shows the field strengthening state (a) and field weakening state (b) of the electric motor 103 The figure which shows the driveable area | region according to the rotation speed and torque of the electric motor 103 which changes according to the induced voltage constant Ke. The figure which shows the rotor phase difference from which the driving | operation possible area | region of the electric motor 103 and the operating efficiency of the electric motor 103 become optimal. The figure which shows the induced voltage constant and rotor phase difference which are set to the electric motor 103 according to the driving | running | working state of a vehicle, and the state of the internal combustion engine 101. A flowchart showing an operation performed by the controller 119 when the internal combustion engine 101 is started. A flowchart showing an operation performed by the controller 119 when the internal combustion engine 101 is idling stopped. Block diagram showing a vehicle driving device disclosed in Japanese Patent Laid-Open No. 11-147424

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Internal combustion engine 103 Electric motor 105 Actuator 107 Clutch 109 Pulley 111 Belt 113 Inverter 115 Accumulator 117 Resolver 119 Controller 121 Auxiliary machine 50 Stator 50a Armature 51 Inner rotor 52 Outer rotor 53 Rotating shaft 30 Rotor phase difference change part 31 1st planetary gear 32 Second planetary gears 33, 35 Rotating shaft 34 Bearing C1 First planetary carrier C2 Second planetary carrier R1 First ring gear R2 Second ring gear S Sun gear

Claims (7)

A permanent magnet field-type electric motor having a first rotor and a second rotor provided concentrically around a rotating shaft;
An internal combustion engine coupled to the electric motor that generates power for the vehicle to travel;
A control unit for controlling a relative displacement angle of the first rotor and the second rotor of the electric motor according to a state of the internal combustion engine,
The control unit controls the relative displacement angle to be advanced from an angle at which an induced voltage constant of the electric motor becomes maximum after the internal combustion engine is started by the electric motor. The vehicle drive device according to claim 1,
When the internal combustion engine is idling stopped, when there is a drive request for an auxiliary machine mounted on the vehicle, the control unit advances the relative displacement angle from an angle at which the induced voltage constant of the electric motor becomes maximum, A vehicle drive device that controls to supply current to the electric motor. The vehicle drive device according to claim 1 or 2,
The electric motor in which the relative displacement angle is advanced from an angle at which the induced voltage constant of the electric motor is maximized generates electric power more than an electric power required for an auxiliary device mounted on the vehicle, and the auxiliary device A vehicle drive device that supplies power to the vehicle. The vehicle drive device according to claim 1,
When the internal combustion engine stops idling and there is no request for driving an auxiliary machine mounted on the vehicle, the control unit controls the relative displacement angle to be set to an angle at which the induced voltage constant of the electric motor is maximized. The vehicle drive device characterized by the above-mentioned. The vehicle drive device according to any one of claims 1 to 4,
The control unit controls the relative displacement angle so that the induced voltage constant of the electric motor is maximized when the internal combustion engine is started by the electric motor. The vehicle drive device according to claim 3,
A rotation speed detection unit for detecting the rotation speed per unit time of the first rotor or the second rotor;
The control unit has the best driving efficiency of the electric motor based on the output torque of the electric motor that generates more than the electric power required for the auxiliary machine that is requested to drive and the rotational speed detected by the rotational speed detection unit. A vehicle drive device that controls to set the relative displacement angle to an angle. The vehicle drive device according to claim 2,
A clutch that switches between transmission and non-transmission of power between the electric motor and the internal combustion engine;
When the internal combustion engine stops idling, if there is a drive request for an auxiliary device mounted on the vehicle, the control unit controls to disengage the clutch.

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