Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60D—VEHICLE CONNECTIONS
  • B60D1/00—Traction couplings; Hitches; Draw-gear; Towing devices
  • B60D1/58—Auxiliary devices
  • B60D1/62—Auxiliary devices involving supply lines, electric circuits, or the like
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60D—VEHICLE CONNECTIONS
  • B60D1/00—Traction couplings; Hitches; Draw-gear; Towing devices
  • B60D1/01—Traction couplings or hitches characterised by their type
  • B60D1/06—Ball-and-socket hitches, e.g. constructional details, auxiliary devices, their arrangement on the vehicle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60D—VEHICLE CONNECTIONS
  • B60D1/00—Traction couplings; Hitches; Draw-gear; Towing devices
  • B60D1/48—Traction couplings; Hitches; Draw-gear; Towing devices characterised by the mounting
  • B60D1/54—Traction couplings; Hitches; Draw-gear; Towing devices characterised by the mounting collapsible or retractable when not in use, e.g. hide-away hitches

Definitions

• the invention concerns a trailer hitch for a motor vehicle, said trailer hitch comprising
• a motor that can be used to swivel the hook from a first position, preferably a working position, in which a trailer can be attached to the hook, to a second po sition, preferably a parking position, in which no trailer can be attached to the hook,
• control unit for controlling the motor, said control unit being able to activate the motor by means of an test pulse in such a way that a hook located in the first position is subjected during the test pulse to a force which has a direction which is directed counter to the direction of movement for moving the hook from the first position into the second position, and
• a current or voltage sensor for detecting the current received by the motor or a voltage applied to the motor during the test pulse, wherein the current or volt age sensor is connected to the motor and is either connected to an input of the control unit or the current or voltage sensor is part of the control unit and the connection to the motor is established via an input of the control unit.
• a towing device with a pivoting tow hook is described in document EP 2724876 A1 and in the application filed by the applicant with the application number PCT/EP2018/082253. It is also disclosed in the document that the hitch hook has a motor for swivelling the trailer hook from a parked position to a working position and vice versa. It also described that a current sensor may be provided to measure the motor current. The motor current measurement can be used to measure the load on the hitch hook. By detecting the load on the trailer hooks, it is possible to monitor whether the trailer is still connected to the towing vehicle's hitch or whether the con nection between the towing vehicle and the trailer has become loose. An additional sensor can be optionally mounted for measuring the weight of the trailer on the hitch hook. The motor current measurement performed during the test pulse is also used to determine whether the hitch hook is securely locked into the working position or the hitch hook has become loose.
• a sensor for the motor current provided for swivelling the hook can also be used to de termine whether the hook is in a first position, for example a working position or not.
• a test pulse is applied to the motor, the magnitude of which is deter mined by the voltage of the on-board power supply system supplying the motor and by the level of the counterforce opposing the force of the motor.
• the counterforce is generated by the motor pressing the hook against a stop defined by the construction of the base and the hook, which defines an end position.
• This counterforce is large compared to the counterforce acting on the hitch in the park ing position or in a position between the parking position and the working position.
• the force applied by the motor and, as a result, the current supplied to the motor is corre spondingly high, as the current is proportional to the torque applied by the motor and, therefore, to the force applied.
• the cyclical test pulses increase the force with which the trailer hook is pressed into its end position by the motor.
• the voltage in the on-board power supply system of the towing vehicle increases, especially during longer journeys, especially when all power storage devices connected to the on-board power supply system, such as batteries, are charged.
• the higher voltage of the on-board power supply is then also applied to the motor of the trailer coupling, which during a test pulse drives a larger current through the motor of the trailer hitch than is the case when the voltage in the on-board power supply is lower.
• This higher motor current caused by the higher voltage in the vehicle electrical system, also results in a higher force with which the motor acts on the trailer hitch.
• the present invention is based on the objective of improving a trailer hitch of the type mentioned above in such a way that blocking of the hook in the first position (for ex ample a working position) is prevented.
• this problem is solved by programming the control unit in such a way that the current received by the motor or the voltage applied to the motor is controlled during the test pulse.
• the force exerted by the motor on the hook can be limited. This pre vents the hook from blocking in the first position (for example the working position) and ensures that the hook can easily be swivelled from the first position (for example the working position) to the second position (for example the parking position) if nec essary.
• the trailer hitch may have a DC/DC converter which has an input for connection to a vehicle electrical system, an output connected to the motor and a control input con nected directly or indirectly to an output of the control unit.
• the con trol unit may have an output for the power supply of the motor.
• the control unit of a trailer hitch in accordance with the invention may have a control ler for controlling the voltage applied to the motor, hereinafter referred to as voltage controller, or a controller of the motor current, hereinafter referred to as current con troller.
• the current controller in particular can be a PID (proportional-integral-deriva tive) controller.
• the controlling unit (ECU) comprises a controller for controlling the current absorbed by the motor by adjusting the duty cycle of the PWM motor com mand during the re-tension pulse.
• a current value can be stored in the control unit, which forms the reference variable for the current controller.
• Several different current values can also be stored which can be selected as reference variable s for the current controller. The same applies to the voltage controller, for which one or more voltage values can be stored in the control unit.
• the control unit can be programmed so that the highest stored current value is up to approx. 15% above a minimum current value that must be reached during the test pulse motor current. This ensures that the amount of current necessary for a positive result of the test of the function of the trailer hitch can be achieved with a trailer hitch according to the invention. If the current is not reached, the trailer hitch is not in the working position or there is some other fault which can lead to a negative test result.
• the control unit of a trailer hitch can be programmed in such a way that during the generation of a test pulse, the stored current amounts are successively selected as reference variable until the highest stored current amount is selected. In this way a so-called soft start can be achieved, which leads to a lower load on the vehicle electrical system or to better EMC. In addition to a lower load on the vehicle electrical system, the soft start will prevent the appearance of the inrush current assuring thus a smoother increase of the current consumed by the hitch motor and therefore a smoother increase of the torque applied to the hitch hook.
• an test pulse is cyclically generated with which the motor of the trailer hitch is supplied in order to exert a force on the hook with the motor, which presses the hook in a direc- tion opposite to the direction of movement for moving the hook from the working posi tion to the parking position, thereby controlling the voltage or current applied to the motor so that a desired amount of the force acting on the hook is not exceeded.
• the voltage controller can be used to control the voltage applied to the motor or the current received by the motor can be controlled with the current controller.
• the test pulse can have a length or duration of approx. 400 ms, for example. If the motor current is controlled, the reference varia ble can be increased in steps. It is possible that the steps between the start of the test pulse and a maximum motor current have a length of approx. 50 ms each.
• the motor current can be controlled by pulse width modulation.
• the current level can be adjusted by setting the duty cycle.
• Fig. 1 shows a block diagram of a control circuit for a trailer hitch according to the invention
• Fig. 2 is a current-time diagram showing the motor current controlled with a regu lation without soft start at an on-board voltage of 13 V,
• Fig. 3 is a current-time diagram showing the motor current controlled by a soft- start control at an on-board voltage of 13 V and a reference variable ,
• Fig. 4 is a current-time diagram showing the motor current controlled by a soft- start control at an on-board voltage of 15.8 V and the reference variable , and
• FIG. 5 is a current-time diagram showing the motor current controlled by a soft- start control at an on-board voltage of 10.5 V and the reference variable .
• a trailer hitch according to the invention has a base which can be attached to a towing vehicle.
• a hook is pivotably attached to the base via a swivel joint. The hook can be swivelled between a second position (for example a parking position behind a bumper), and a first position (for example a working position) in which a trailer can be attached.
• the trailer hitch has an electric motor.
• the motor can apply a force to the hook in the direction of movement from the parking position to the work ing position and thus against movement of the hook from the working position to the parking position.
• the motor current is determined by the voltage applied to the motor and the electrical properties of the motor.
• the motor current is proportional to the force applied by the motor, which always exceeds a specified value when the trailer hook is pressed against the stop. If the specified value is reached for a specified period of time, this is an indication that the hook is in the working position. If it is not reached, there is an error.
• the idea of the invention is preventing an increase of the re-tension force during every pulse applied to the motor. This is done by limitation of the voltage and/or the current applied to the motor. Because the torque generated by a DC motor is proportional to the motor current, the best approach for assuring a constant force for each pulse is to control the motor current to a desired set point or reference motor current.
• the input will be error between the reference variable and the measured motor cur rent - the output will be the duty cycle of the motor PWM command
• Such a motor current control is represented in fig. 1 , which shows an electronic control unit ECU of a so called trailer tow module TTM.
• Iref is the reference variable for the pulse, which must be above a minimum current threshold for re-tension validation
• I is the actual motor current of a hitch hook motor measured on a feedback line MOT1_IS_AI
• e Iref - 1 is an error signal
• PID is a proportional-integral-derivative controller
• DC is a duty cycle for the motor driver computed by the controller and provided on a control line MOT1_PWM_PO.
• the PID feedback control is a control loop mechanism providing feedback of the con trolled motor in the presentation of the continuously calculated error signal e(t), which is the difference between the reference motor current Iref and a measured process variable I.
• trailer tow module TTM usually is a discrete system
• a discrete transfer function of PID Z transform
• T s is the sampling time, in this case 5 ms.
• the controller performance is adjusted through adjusting the coefficients or gains K p , K j and K d to obtain an error as small as possible for the controlled current.
• controllers coefficients need to take into account the entire system, including also the mechanical part of the electrical hitch and not only the electrical characteristics of the hitch motor. Therefore, for deter mining the controller’s coefficients also take into consideration all the tolerances that can occur in all domains (mechanical, electrical). An appropriate way to determine the gains is the experimental way.
• the controlled motor current is stabilized at approximately 8.3 A, which is above the minimum current of 7.2 A required to validate the test or re-tension pulse.
• the error from the refer ence variable has stabilized at 0.2 A and the duty cycle of the PWM motor command stabilizes at around 85%. This can be observed in the measurement shown in fig. 2.
• a smoother curve of the motor current can be obtained by adding a soft start of the reference variable in the first 100 ms of the test or re-tension pulse:
• the soft-start can be adjusted based on the controlling application in each application.
• the motor current has a smoother ramp and stabilizes around 8.4 A.
• the stationary error is 0.1 A and the duty cycle stabilizes around 86%.

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• Engineering & Computer Science (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Control Of Direct Current Motors (AREA)
• Electric Propulsion And Braking For Vehicles (AREA)

Priority Applications (3)

Applications Claiming Priority (1)

Publications (1)

Family

ID=70482630

Family Applications (1)

Country Status (3)

Citations (6)

• 2020
  • 2020-04-29 EP EP20723333.9A patent/EP4143039A1/en active Pending
  • 2020-04-29 CN CN202080099733.9A patent/CN115397680A/zh active Pending
  • 2020-04-29 WO PCT/EP2020/061837 patent/WO2021219209A1/en unknown

Patent Citations (6)

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