Control device for power transmission mechanism, control method for power transmission mechanism, and program for control device

Abstract

A first control unit (71) outputs a drive signal to a motor actuator (63) to move a motor clutch (61). A first position determination unit (73) determines the position of the motor clutch (61) on the basis of the output of a sleeve stroke sensor (52). A first disconnection determination unit (75) detects a disconnection of the sleeve stroke sensor (52) when the amount of change per predetermined time of the output of the sleeve stroke sensor (52) is equal to or greater than a threshold value. A first movement determination unit (77) determines whether or not the motor clutch (61) is moving. The first disconnection determination unit (75) changes the threshold value when the first movement determination unit (77) determines that the motor clutch (61) is moving and when the first movement determination unit (77) determines that the motor clutch (61) is not moving.

Description

Control device for power transmission mechanism, control method for power transmission mechanism, and program for control device

[0001] The present invention relates to a control device for a power transmission mechanism, a control method for a power transmission mechanism, and a program for a control device.

[0002] Conventionally, a transaxle control device has been proposed that detects the position of a clutch by providing a stroke sensor (position sensor) on the clutch sleeve (Patent Document 1).

[0003] Japanese Patent No. 6881598

[0004] In a conventional transaxle control device, the clutch position cannot be detected if the stroke sensor is disconnected. Although it has been considered to detect disconnection of the stroke sensor, there has been a problem that the disconnection cannot be detected with high accuracy.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for a power transmission mechanism, a control method for a power transmission mechanism, and a program for a control device that can detect disconnection with high accuracy.

[0006] In order to achieve the above object, a control device for a power transmission mechanism according to the present invention is characterized as follows. A control device for a power transmission mechanism, comprising: a clutch movable between a disconnected position where a drive source is disconnected from a drive shaft of a vehicle and a connected position where the drive source is connected to the drive shaft; a first position sensor that detects a position of a sleeve of the clutch; and an actuator that supplies a driving force for moving the clutch, the control device comprising: a control unit that outputs a drive signal to the actuator to move the clutch; a position determination unit that determines the position of the clutch based on an output from the first position sensor; a disconnection determination unit that detects disconnection of the first position sensor when an amount of change in the output of the first position sensor per predetermined time is equal to or greater than a threshold value; and a movement determination unit that determines whether the clutch is moving, wherein the disconnection determination unit changes the threshold value depending on whether the movement determination unit determines that the clutch is moving or determines that the clutch is not moving.

[0007] To achieve the above objective, the control device for a power transmission mechanism according to the present invention is characterized as follows: A control device for a power transmission mechanism having: a first clutch movable between a cutting position where the engine and the drive shaft of a vehicle are disconnected and a connection position where the engine and the drive shaft are connected; a position sensor for the first clutch that detects the position of the sleeve of the first clutch; a first actuator that supplies a driving force to move the first clutch; a second clutch movable between a cutting position where the motor and the drive shaft are disconnected and a connection position where the motor and the drive shaft are connected; a position sensor for the second clutch that detects the position of the sleeve of the second clutch; and a second actuator that supplies a driving force to move the second clutch, wherein the control device comprises: a first control unit that outputs a drive signal to the first actuator to move the first clutch; a second control unit that outputs a drive signal to the second actuator to move the second clutch; a first position determination unit that determines the position of the first clutch based on the output of the position sensor for the first clutch; and a second position determination unit that determines the position of the second clutch based on the output of the position sensor for the second clutch. A power transmission mechanism control device comprising: a first wire break detection unit that detects a wire break in the position sensor for the first clutch when the amount of change per predetermined time of the output of the position sensor for the first clutch is equal to or greater than a first threshold; a second wire break detection unit that detects a wire break in the position sensor for the second clutch when the amount of change per predetermined time of the output of the position sensor for the second clutch is equal to or greater than a second threshold; a first movement detection unit that determines whether the first clutch is moving or not; and a second movement detection unit that determines whether the second clutch is moving or not, wherein the first wire break detection unit changes the first threshold depending on whether the first movement detection unit determines that the first clutch is moving or not; and the second wire break detection unit changes the second threshold depending on whether the second movement detection unit determines that the second clutch is moving or not.

[0008] To achieve the above objective, the control method for a power transmission mechanism according to the present invention is characterized as follows: A control method for a power transmission mechanism having a clutch movable between a cutting position where a drive source and the drive shaft of a drive wheel are disconnected and a connection position where the drive source and the drive shaft are connected, a first position sensor for detecting the position of the sleeve of the clutch, and an actuator for supplying driving force to move the clutch, comprising: a control step of outputting a drive signal to the actuator to move the clutch; a position determination step of determining the position of the clutch based on the output of the first position sensor; a disconnection determination step of detecting a disconnection of the first position sensor when the amount of change of the output of the first position sensor per predetermined time is greater than or equal to a threshold; and a movement determination step of determining whether the clutch is moving or not, wherein in the disconnection determination step, the threshold is changed depending on whether the movement determination step determines that the clutch is moving or not.

[0009] To achieve the above objective, the program for the control device according to the present invention is characterized as follows: A program for a control device for a power transmission mechanism having a clutch that is movable between a cutting position where a drive source and a vehicle's drive shaft are disconnected and a connection position where the drive source and the drive shaft are connected, a first position sensor for detecting the position of the clutch sleeve, and an actuator for supplying driving force to move the clutch, wherein the program causes the control device to function as: a control unit that outputs a drive signal to the actuator to move the clutch; a position determination unit that determines the position of the clutch based on the output of the first position sensor; a disconnection determination unit that detects a disconnection of the first position sensor when the amount of change in the output of the first position sensor per predetermined time is greater than or equal to a threshold; and a movement determination unit that determines whether or not the clutch is moving, wherein the disconnection determination unit changes the threshold depending on whether or not the clutch is moving as determined by the movement determination unit.

[0010] The power transmission mechanism control device, power transmission mechanism control method, and control device program of the present invention have the effect of being able to detect wire breaks with high accuracy.

[0011] The present invention has been briefly described above. Furthermore, the details of the present invention will be further clarified by referring to the accompanying drawings and reading through the embodiments for carrying out the invention described below (hereinafter referred to as "embodiments").

[0012] Figure 1 is a block diagram of an electric vehicle to which the control device of the power transmission mechanism of the present invention is applied. Figure 2 is a block diagram showing the power transmission mechanism shown in Figure 1 and one embodiment of the power transmission mechanism of the present invention. Figure 3 is a functional block diagram showing one embodiment of the controller 7 shown in Figures 1 and 2. Figure 4 is a time chart of the sensor voltage of the sleeve stroke sensor shown in Figure 2. Figure 5 is a flowchart showing the processing procedure of the controller shown in Figure 2. Figure 6 is a time chart of the actual gear position, shift signal, and control sensor voltage.

[0013] Specific embodiments of the present invention will be described below with reference to the figures.

[0014] Figure 1 is a block diagram of an electric vehicle to which the control device for the power transmission mechanism of the present invention is applied. The electric vehicle 1 is a plug-in hybrid vehicle (PHEV) or hybrid vehicle (HEV) that uses an engine 2 and a motor 3 as its drive sources. Note that PHEV refers to a hybrid vehicle that can be externally charged to a battery or receive external power from a battery. A PHEV has a charging port (inlet) for inserting a charging cable into which power is supplied from an external charging facility, and an outlet for external power supply.

[0015] The electric vehicle 1 is equipped with three driving modes: EV mode, series mode, and parallel mode. These driving modes are selectively selected by the HEV-ECU 8 (described later) according to the vehicle status, driving conditions, and the driver's requested output, and the engine 2, motor 3, and generator 4 are used accordingly.

[0016] EV mode is a driving mode in which the electric vehicle 1 is driven only by the motor 3 using the charge power from a drive battery (not shown) while the engine 2 and generator 4 are stopped. EV mode is selected when the driving load and vehicle speed are low or when the battery charge level is high. Series mode is a driving mode in which the engine 2 drives the generator 4 to generate electricity, and that electricity is used to drive the electric vehicle 1 with the motor 3. Series mode is selected when the driving load and vehicle speed are moderate or when the battery charge level is low. Parallel mode is a driving mode in which the vehicle 10 is mainly driven by the engine 2, and the motor 3 assists in driving the vehicle 10 as needed, and is selected when the driving load and vehicle speed are high.

[0017] The electric vehicle 1 described above comprises an engine 2, a motor 3, a generator 4, a first power transmission mechanism 5, a second power transmission mechanism 6, a controller 7 as a "control device for the power transmission mechanism", and an HEV-ECU 8.

[0018] Engine 2 constitutes the power source in the electric vehicle 1 and generates power by burning fuel. Engine 2 drives the drive shaft 9 attached to the drive wheels.

[0019] Motor 3 drives the drive shaft 9 by receiving power from the battery. Motor 3 also has a regenerative function, recovering deceleration energy as electricity by being driven along with the rotation of the drive shaft 9 during deceleration. Motor 3 constitutes the power source in the electric vehicle 1.

[0020] The generator 4 generates electricity using the power of the engine 2 and also drives the drive shaft 9 by receiving power from the battery. The generator 4 constitutes the power source of the electric vehicle 1.

[0021] The first power transmission mechanism 5 transmits the driving force of the engine 2 and the generator 4 to the drive shaft 9. As shown in Figure 2, the first power transmission mechanism 5 includes an engine clutch 51 (= clutch, first clutch), a sleeve stroke sensor 52 (= first position sensor, position sensor for the first clutch), and an engine actuator 53 (= actuator, first actuator). The engine clutch 51 is provided to be movable in the axial direction of the sleeve. By moving in the axial direction of the sleeve, the engine clutch 51 is provided to be movable to a neutral position, a low position, and a high position. The neutral position is the position where the engine 2 and the generator 4 are disconnected from the drive shaft 9. The low position is the position where the engine 2 and the generator 4 are connected to the drive shaft 9 via a low-speed gear. The high position is the position where the engine 2 and the generator 4 are connected via a high-speed gear.

[0022] The sleeve stroke sensor 52 detects the amount of movement (stroke) of the sleeve of the engine clutch 51 and outputs a sensor voltage. The engine actuator 53 supplies the driving force for the engine clutch 51 to move the sleeve in the axial direction. The engine actuator 53 has an actuator stroke sensor 54 (= second position sensor) that detects the amount of drive (stroke) of the engine actuator 53 and outputs a sensor voltage.

[0023] The second power transmission mechanism 6 transmits the driving force of the motor 3 to the drive shaft 9. As shown in Figure 2, the second power transmission mechanism 6 includes a motor clutch 61 (= clutch, second clutch), a sleeve stroke sensor 62 (= first position sensor, position sensor for the second clutch), and a motor actuator 63 (= actuator, second actuator). The motor clutch 61 is provided to be movable in the axial direction of the sleeve. The motor clutch 61 is provided to be movable to an ON position and an OFF position by moving in the axial direction of the sleeve. The ON position is the position where the motor 3 and the drive shaft 9 are disconnected. The OFF position is the position where the motor 3 and the drive shaft 9 are connected.

[0024] The sleeve stroke sensor 62 detects the amount of movement (stroke) of the sleeve of the motor clutch 61 and outputs a sensor voltage. The motor actuator 63 supplies the driving force for the motor clutch 61 to move the sleeve in the axial direction. The motor actuator 63 has an actuator stroke sensor 64 that detects the amount of drive (stroke) of the motor actuator 63 and outputs a sensor voltage.

[0025] The controller 7 consists of a storage unit that stores programs and the like, and a computer that operates according to the programs. As shown in Figure 3, the controller 7 has a first control unit 71 (control unit), a second control unit 72 (control unit), a first position determination unit 73 (position determination unit), a second position determination unit 74 (position determination unit), a first disconnection determination unit 75 (disconnection determination unit), a second disconnection determination unit 76 (disconnection determination unit), a first movement determination unit 77 (movement determination unit), and a second movement determination unit 78 (movement determination unit).

[0026] The first control unit 71 outputs a drive signal to the engine actuator 53 in accordance with the shift signal from the HEV-ECU 8, causing the engine clutch 51 to move to the target position. The first position determination unit 73 acquires the sensor voltage of the sleeve stroke sensor 52 at sampling time intervals. The first position determination unit 73 obtains a control sensor voltage from the acquired sensor voltage and determines the position of the engine clutch 51 based on the obtained control sensor voltage. The first control unit 71 outputs a drive signal to the engine actuator 53 so that the position of the engine clutch 51 determined by the first position determination unit 73 becomes the target position.

[0027] The first wire break detection unit 75 determines whether or not a wire break has occurred in the wire connecting the sleeve stroke sensor 52 and the controller 7. The wire break detection performed by the first wire break detection unit 75 will be described below with reference to Figure 4. In Figure 4, the solid line shows the sensor voltage output from the sleeve stroke sensor 52. In Figure 4, the dotted line shows the sensor voltage after filtering to remove noise components. The first position determination unit 73 determines the control sensor voltage from the filtered sensor voltage.

[0028] When a wire break occurs, the sensor voltage will stick at a high level as shown by the solid line, and if it was at a low level, it will change rapidly from a low level to a high level. As shown by the dashed line, the sensor voltage after filtering will also change rapidly from a low level to a high level. The first wire break detection unit 75 detects a wire break in the sleeve stroke sensor 52 when the amount of change in the sensor voltage after filtering per sampling time (= predetermined time) is greater than or equal to a threshold.

[0029] As shown by the dashed line in Figure 4, the first position determination unit 73, when the first disconnection determination unit 75 determines that there is a disconnection, retains the sensor voltage sampled previously and uses the retained sensor voltage as the control sensor voltage. The first disconnection determination unit 75 confirms a disconnection when the sensor voltage of the sleeve stroke sensor 52 exceeds a certain value and a certain period of time has elapsed.

[0030] When the first position determination unit 73 determines that a wire has been broken by the first wire break determination unit 75, it uses the sensor voltage from the actuator stroke sensor 54 as a substitute value for the sensor voltage from the sleeve stroke sensor 52, as shown by the dashed line in Figure 4. The first position determination unit 73 then uses the substitute value, the sensor voltage of the actuator stroke sensor 54, as the control sensor voltage.

[0031] Incidentally, the sensor voltage of the sleeve stroke sensor 52 fluctuates not only when there is a break in the wire, but also when the gear changes, that is, when the sleeve of the engine clutch 51 moves. For this reason, if the threshold used for wire break detection is kept constant, the first wire break detection unit 75 may mistakenly determine that the movement of the sleeve of the engine clutch 51 during gear changes is a wire break. Therefore, the first wire break detection unit 75 changes the threshold depending on whether it is determined that the engine clutch 51 is moving or not.

[0032] The first movement determination unit 77 determines whether or not the engine clutch 51 is moving and supplies the result to the first wire break determination unit 75. The first movement determination unit 77 determines that the clutch is moving if the first control unit 71 receives a shift signal from the HEV-ECU 8 and outputs a drive signal. The first movement determination unit 77 determines that the clutch is not moving if the first control unit 71 does not output a drive signal.

[0033] The second control unit 72 outputs a drive signal to the motor actuator 63 in accordance with the shift signal from the HEV-ECU 8, causing the motor clutch 61 to move to the target position. The second position determination unit 74 acquires the sensor voltage of the sleeve stroke sensor 62 at sampling time intervals. The second position determination unit 74 obtains a control sensor voltage from the acquired sensor voltage and determines the position of the motor clutch 61 based on the obtained control sensor voltage. The second control unit 72 outputs a drive signal to the motor actuator 63 so that the position of the motor clutch 61 determined by the second position determination unit 74 becomes the target position.

[0034] The second wire break detection unit 76 determines whether or not a break has occurred in the wire connecting the sleeve stroke sensor 62 and the controller 7. Similar to the first wire break detection unit 75, the second wire break detection unit 76 detects a break in the sleeve stroke sensor 62 if the amount of change per sampling time of the sensor voltage after filtering is greater than or equal to a threshold.

[0035] As shown by the dashed line in Figure 4, the second position determination unit 74, when the second wire break detection unit 76 determines that there is a wire break, retains the sensor voltage sampled previously and uses the retained sensor voltage as the control sensor voltage. The second wire break detection unit 76 confirms a wire break when the sensor voltage of the sleeve stroke sensor 62 exceeds a certain value and a certain period of time has elapsed.

[0036] When the second position determination unit 74 determines that a wire has been broken by the second wire break determination unit 76, it uses the sensor voltage from the actuator stroke sensor 64 as a substitute value for the sensor voltage from the sleeve stroke sensor 62. The second position determination unit 74 then uses the substitute value, the sensor voltage of the actuator stroke sensor 64, as the control sensor voltage.

[0037] The second wire break detection unit 76 changes the threshold value depending on whether the motor clutch 61 is moving or not, for the same reasons as the first wire break detection unit 75.

[0038] Next, the operation of the controller 7, as outlined above, will be described in detail below with reference to the flowchart in Figure 5. The controller 7 starts processing in response to the ignition being turned on (IG-ON). The controller 7 calculates the difference between the sensor voltage (n) sampled this time and the sensor voltage (n-1) sampled last time from the sleeve stroke sensor 52 as the amount of change (S1). Next, the controller 7 determines whether a predetermined time has elapsed since the IG-ON was turned on for the controller 7 itself to fully start up (S2).

[0039] If the predetermined time has not elapsed (N in S2), the controller 7 does not perform wire break detection and uses the sensor voltage (n) sampled this time as the control sensor voltage (S3). The controller 7 detects the stroke amount of the engine clutch 51 from the control sensor voltage (S4). If a wire break is confirmed, the controller 7 uses the sensor voltage of the actuator stroke sensor 54 as a substitute to determine the stroke amount (S5) and terminates the process.

[0040] In response to this, if a predetermined time has elapsed (Y in S2), the controller 7 determines whether the fault flag of the sleeve stroke sensor 52 has changed from 1 to 0 (S6). If the fault flag has changed from 1 to 0 (Y in S6) and it is immediately after recovery from a fault, the controller 7 uses the sensor voltage (n) sampled this time as the control sensor voltage (S7) and then proceeds to S4.

[0041] In contrast, if the fault flag is not 1 or 0 (N in S6), the controller 7 determines whether the engine clutch 51 is moving or not (S8). If the HEV-ECU 8 has not output a shift signal and the engine clutch 51 is not moving, i.e., stopped (Y in S8), the controller 7 determines whether the amount of change obtained in S1 is less than the threshold Th1 (S9). If the amount of change is less than the threshold Th1 (Y in S9), the controller 7 does not determine that there is a break in the wire, and after using the sensor voltage (n) sampled this time as the control sensor voltage (S10), proceeds to S4.

[0042] On the other hand, when the amount of change is equal to or greater than the threshold Th1 (N in S9), controller 7 determines that there is a high possibility of disconnection, sets the previously sampled sensor voltage (n-1) as the sensor voltage for control (S11), and then proceeds to S4.

[0043] On the other hand, if controller 7 receives a shift signal output from HEV-ECU 8 and engine clutch 51 is in the process of moving (N in S8), controller 7 determines whether the amount of change obtained in S1 is less than threshold Th2 (S12). Threshold Th2 is set to a larger value than threshold Th1. When the amount of change is less than threshold Th2 (Y in S12), controller 7 does not determine that a disconnection has occurred, sets the currently sampled sensor voltage (n) as the sensor voltage for control (S13), and then proceeds to S4.

[0044] In contrast, when the amount of change is equal to or greater than threshold Th2 (N in S12), controller 7 determines that there is a high possibility of disconnection, sets the previously sampled sensor voltage (n-1) as the sensor voltage for control (S14), and then proceeds to S4.

[0045] The above description is given for engine clutch 51, but controller 7 operates in the same way for motor clutch 61. In this case, in the description of Fig. 6, the description can be read by replacing "engine clutch 51" with "motor clutch 61", "sleeve stroke sensor 52" with "sleeve stroke sensor 62", and "actuator stroke sensor 54" with "actuator stroke sensor 64".

[0046] According to the above-described embodiment, controller 7 changes thresholds Th1 and Th2 between when engine clutch 51 and motor clutch 61 are moving and when engine clutch 51 and motor clutch 61 are not moving. As shown in Fig. 6, during shifting (when the clutch is moving) where a shift signal is output, controller 7 detects disconnection based on threshold Th2. With this configuration, even if the sensor voltage fluctuates due to shifting as shown in part A of Fig. 4, controller 7 does not detect a disconnection. Therefore, as shown in part B of Fig. 4, the sensor voltage for control is not maintained at the previously sampled sensor voltage.

[0047] In contrast, when no shift signal is output and no shifting is performed, disconnection is detected based on threshold Th1 which is smaller than threshold Th2. When no shifting is in progress, as shown in section C in FIG. 4, if disconnection occurs and the sensor voltage fluctuates, the disconnection is immediately detected by the controller 7. Therefore, as shown in section D in FIG. 4, the control sensor voltage is held at the sensor voltage sampled in the previous cycle. This enables disconnection to be detected with high accuracy.

[0048] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the present invention.

[0049] In the above-described embodiment, an example in which the present invention is applied to a PHEV and an HEV provided with two clutches, that is, the engine clutch 51 and the motor clutch 61, is described, but the present invention is not limited thereto. The present invention may also be applied to an engine vehicle provided with only the engine clutch 51, or an electric vehicle (EV) provided with only the motor clutch 61.

[0050] According to the present invention, it is possible to provide a control device for a power transmission mechanism, a control method for a power transmission mechanism, and a program for a control device, which can detect disconnection with high accuracy. The present invention, which achieves this effect, is useful in the fields of control devices for power transmission mechanisms, control methods for power transmission mechanisms, and programs for control devices.

[0051] 2 Engine (power source) 3 Motor (power source) 7 Controller (control device for power transmission mechanism) 9 Drive shaft 51 Engine clutch (clutch, first clutch) 52 Sleeve stroke sensor (first position sensor, position sensor for first clutch) 53 Engine actuator (actuator, first actuator) 54 Actuator stroke sensor (second position sensor) 61 Motor clutch (clutch, second clutch) 62 Sleeve stroke sensor (first position sensor, position sensor for second clutch) 63 Motor actuator (actuator, second actuator) 71 First control unit (control unit) 72 Second control unit (control unit) 73 First position determination unit (position determination unit) 74 Second position determination unit (position determination unit) 75 First wire breakage determination unit (wire breakage determination unit) 76 Second wire breakage determination unit (wire breakage determination unit) 77 First movement determination unit (movement determination unit) 78 Second movement determination unit (movement determination unit)

Claims

1. A control device for a power transmission mechanism having a clutch that is movable between a cutting position where a drive source and a vehicle's drive shaft are disconnected and a connection position where the drive source and the drive shaft are connected, a first position sensor for detecting the position of the clutch sleeve, and an actuator for supplying driving force to move the clutch, comprising: a control unit that outputs a drive signal to the actuator to move the clutch; a position determination unit that determines the position of the clutch based on the output of the first position sensor; a disconnection determination unit that detects a disconnection of the first position sensor when the amount of change of the output of the first position sensor per predetermined time is greater than or equal to a threshold; and a movement determination unit that determines whether or not the clutch is moving, wherein the disconnection determination unit changes the threshold depending on whether or not the clutch is moving as determined by the movement determination unit.

2. A control device for a power transmission mechanism according to claim 1, wherein the threshold value when it is determined that the clutch is moving is set to be greater than the threshold value when it is determined that the clutch is not moving.

3. A control device for a power transmission mechanism according to claim 1, wherein the position determination unit, when determined to be disconnected by the disconnection determination unit, holds the previous output of the first position sensor and determines the position of the clutch based on the held output of the first position sensor.

4. A control device for a power transmission mechanism according to claim 3, wherein the power transmission mechanism further comprises a second position sensor for detecting the drive position of the actuator, and the position determination unit holds the output of the first position sensor and then determines the position of the clutch based on the output of the second position sensor.

5. A control device for a power transmission mechanism according to claim 1, wherein the wire break detection unit does not perform a wire break detection until a predetermined time has elapsed since the ignition was turned on.

6. A control device for a power transmission mechanism having: a first clutch movable between a cutting position where the engine and the drive shaft of a vehicle are disconnected and a connection position where the engine and the drive shaft are connected; a position sensor for the first clutch that detects the position of the sleeve of the first clutch; a first actuator that supplies driving force to move the first clutch; a second clutch movable between a cutting position where the motor and the drive shaft are disconnected and a connection position where the motor and the drive shaft are connected; a position sensor for the second clutch that detects the position of the sleeve of the second clutch; and a second actuator that supplies driving force to move the second clutch, the control device comprising: a first control unit that outputs a drive signal to the first actuator to move the first clutch; a second control unit that outputs a drive signal to the second actuator to move the second clutch; a first position determination unit that determines the position of the first clutch based on the output of the position sensor for the first clutch; and a second position determination unit that determines the position of the second clutch based on the output of the position sensor for the second clutch. A control device for a power transmission mechanism, comprising: a first wire break detection unit that detects a wire break in the position sensor for the first clutch when the amount of change per predetermined time of the output of the position sensor for the first clutch is greater than or equal to a first threshold; a second wire break detection unit that detects a wire break in the position sensor for the second clutch when the amount of change per predetermined time of the output of the position sensor for the second clutch is greater than or equal to a second threshold; a first movement detection unit that determines whether the first clutch is moving or not; and a second movement detection unit that determines whether the second clutch is moving or not, wherein the first wire break detection unit changes the first threshold depending on whether the first movement detection unit determines that the first clutch is moving or not; and the second wire break detection unit changes the second threshold depending on whether the second movement detection unit determines that the second clutch is moving or not.

7. A control method for a power transmission mechanism having a clutch movable between a cutting position where a drive source and the drive shaft of a drive wheel are disconnected and a connection position where the drive source and the drive shaft are connected, a first position sensor for detecting the position of the sleeve of the clutch, and an actuator for supplying driving force to move the clutch, the control method comprising: a control step of outputting a drive signal to the actuator to move the clutch; a position determination step of determining the position of the clutch based on the output of the first position sensor; a disconnection determination step of detecting a disconnection of the first position sensor when the amount of change of the output of the first position sensor per predetermined time is greater than or equal to a threshold; and a movement determination step of determining whether the clutch is moving or not, wherein in the disconnection determination step, the threshold is changed depending on whether the movement determination step determines that the clutch is moving or not.

8. A program for a control device for a power transmission mechanism having a clutch that is movable between a cutting position where a drive source and a vehicle's drive shaft are disconnected and a connection position where the drive source and the drive shaft are connected, a first position sensor for detecting the position of the clutch sleeve, and an actuator for supplying driving force to move the clutch, wherein the control device comprises: a control unit that outputs a drive signal to the actuator to move the clutch; a position determination unit that determines the position of the clutch based on the output of the first position sensor; a disconnection determination unit that detects a disconnection of the first position sensor when the amount of change in the output of the first position sensor per predetermined time is greater than or equal to a threshold; and a movement determination unit that determines whether or not the clutch is moving, wherein the disconnection determination unit changes the threshold depending on whether or not the movement determination unit determines that the clutch is moving.

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