Trailer hitch with a rotatable hitch hook and a motor for rotating the hitch hook

Abstract

The invention relates to a trailer coupling device comprising: • a base; • a hook pivotably attached to the base; • a motor which can be used to rotate the hook from a first position, preferably a working position in which a trailer can be attached to the hook, to a second position, preferably a parking position in which no trailer can be attached to the hook; • a control unit for controlling the motor, which is able to start the motor by means of a test pulse, in order to subject the hook, which is in the first position, to a force during the test pulse, which force has a direction opposite to the direction of movement of the hook from the first position to the second position; and • a current or voltage sensor for detecting the current received by the motor or the voltage applied to the motor during the test pulse, which current or voltage sensor is connected to the motor and: • which current or voltage sensor is connected to an input of the control unit; or • which current or voltage sensor is part of the control unit and establishes a connection with the motor via an input of the control unit.

Description

Technical Field

[0001] This invention relates to a trailer hitch assembly for motor vehicles, the trailer hitch assembly comprising:

[0002] • Base

[0003] • A hook that can be pivotally attached to the base,

[0004] • A motor, which can be used to rotate the hook from a first position (preferably a working position) to a second position (preferably a parking position), in the first position where a trailer can be attached to the hook, and in the second position where no trailer can be attached to the hook.

[0005] • A control unit for controlling the motor, the control unit being capable of activating the motor via a test pulse such that the hook in the first position is subjected to a force during the test pulse, the force having a direction opposite to the direction of movement that moves the hook from the first position to the second position, and

[0006] • A current or voltage sensor for detecting the current received by the motor or the voltage applied to the motor during the test pulse, wherein the current or voltage sensor is connected to the motor and: the current or voltage sensor is connected to an input terminal of the control unit; or the current or voltage sensor is part of the control unit and is connected to the motor via an input terminal of the control unit. Background Technology

[0007] A towing device with a pivoting tow hook is described in document EP 2 724 876 A1 and application number PCT / EP2018 / 082253 filed by the applicant. These documents also disclose that the hook has a motor for rotating the trailer hook from a parked position to a working position and from the working position to the parked position. It is also described that a current sensor can be provided to measure the motor current. The motor current measurement can be used to measure the load on the hook. By detecting the load on the trailer hook, it is possible to monitor whether the trailer is still connected to the towing vehicle's hook or whether the connection between the towing vehicle and the trailer has become loose. Optionally, an additional sensor for measuring the weight of the trailer can be mounted on the hook. The motor current measurement performed during a test pulse is also used to determine whether the hook is securely locked into the working position or whether the hook has become loose.

[0008] A sensor for the motor current used to rotate the hook can also be used to determine whether the hook is in a first position (e.g., the working position). For this purpose, a test pulse is applied to the motor, the magnitude of which is determined by the voltage of the onboard power supply system powering the motor and the level of the reaction force opposite to the force exerted by the motor. In the working position of the hook, the reaction force is generated by the motor pressing the hook against a stop defined by the structure of the base and the hook, the stop defining the end position. This reaction force is larger than the reaction force acting on the hooking device in the parked position or in a position between the parked and working positions. Since the current is proportional to the torque applied by the motor and therefore proportional to the applied force, the force applied by the motor and thus the current supplied to the motor are correspondingly high.

[0009] If a predetermined minimum motor current is detected during the test pulse for a predetermined time, this indicates that the trailer hitch is in the working position (i.e., the end position), because the predetermined level of motor current is only reached in the end position. On the other hand, if the motor current is not high enough, or is not high enough for a sufficiently long time, this is an indication of a potential malfunction.

[0010] The periodic test pulses increase the force used to press the trailer hitch to its end position via the motor. Additionally, the voltage in the towing vehicle's onboard power system increases, especially during longer journeys, particularly when all power storage devices connected to the onboard power system (such as batteries) are charging. This higher voltage from the onboard power system is then applied to the trailer hitch motor, driving a larger current through the motor during the test pulses compared to a lower voltage scenario. This higher motor current, caused by the higher voltage in the vehicle's electrical system, also results in a larger force exerted by the motor on the trailer hitch.

[0011] Such a large force may cause the hook to be blocked in the working position and unable to move easily from the working position to the parking position. Summary of the Invention

[0012] The object of the present invention is to improve the above-described type of trailer hitch to prevent the hook from being blocked in the first position (e.g., the working position).

[0013] According to the present invention, this problem is solved by programming the control unit to control the current received by the motor or the voltage applied to the motor during a test pulse. By controlling the motor current or the voltage applied to the motor, the force exerted by the motor on the hook can be limited. This prevents the hook from being blocked in the first position (e.g., the working position) and ensures that the hook can be easily rotated from the first position (e.g., the working position) to the second position (e.g., the parking position) if necessary.

[0014] The trailer hitch can include a DC / DC converter with an input for connection to the vehicle's electrical system, an output for connection to the motor, and a control input for direct or indirect connection to the output of a control unit. Alternatively, the control unit can have an output for power supply to the motor.

[0015] The control unit of the trailer hitch according to the invention may have a controller for controlling the voltage applied to the motor (hereinafter referred to as a voltage controller) or a controller for controlling the motor current (hereinafter referred to as a current controller). The current controller may in particular be a PID (proportional-integral-derivative) controller. The control unit (ECU) includes a controller for controlling the current drawn by the motor by adjusting the load cycle of the PWM motor command during the retension pulse.

[0016] Current values ​​can be stored in the control unit, forming a reference variable for the current controller. Several different current values ​​can also be stored, and these values ​​can be selected as the reference variable 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.

[0017] The control unit can be programmed such that the stored maximum current value exceeds the minimum current value that must be reached during the test pulse motor current by approximately 15%. This ensures that the amount of current required to obtain positive results in the functional test of the trailer hitch according to the invention can be achieved. If the current is not reached, the trailer hitch is not in the operating position or there is other malfunction that could lead to a negative test result.

[0018] The control unit of the trailer hitch according to the invention can be programmed such that, during the generation of test pulses, a stored current quantity is successively selected as a reference variable until the highest stored current quantity is selected. In this way, so-called soft starting can be achieved, which results in a lower load on the vehicle's electrical system or better EMC. In addition to the lower load on the vehicle's electrical system, soft starting prevents inrush current, thereby ensuring a smoother increase in the current consumed by the hitch motor and thus a smoother increase in the torque applied to the hitch hook.

[0019] In the method according to the invention for testing whether the hook of the trailer hitch according to the invention is in a first position (e.g., working position), test pulses are generated periodically, and the test pulses are used to power the motor of the trailer hitch so that the motor applies a force to the hook, the force pressing the hook in a direction opposite to the direction of movement that moves the hook from the working position to the parking position, thereby controlling the voltage or current applied to the motor so that the force acting on the hook does not exceed a desired magnitude.

[0020] During the test pulse, the voltage controller can be used to control the voltage applied to the motor, or the current controller can be used to control the current received by the motor.

[0021] Using the method according to the invention, the test pulse can, for example, have a length or duration of approximately 400 ms. If the motor current is controlled, the reference variable can be increased incrementally. The length of each step between the start of the test pulse and the maximum motor current may each be approximately 50 ms.

[0022] Motor current can be controlled using pulse width modulation. The current level can be adjusted by setting a load cycle. Attached Figure Description

[0023] The invention will now be explained in more detail with reference to the accompanying drawings. Wherein:

[0024] Figure 1 A block diagram of a control circuit for a trailer hitch according to the present invention is shown;

[0025] Figure 2 The current-time graph shows the motor current controlled by regulation without soft start at an onboard voltage of 13V.

[0026] Figure 3 The current-time plot shows the reference variable and the motor current controlled by the soft starter at an on-board voltage of 13V.

[0027] Figure 4The current-time plot shows the reference variable and the motor current controlled by the soft starter at an onboard voltage of 15.8V; and

[0028] Figure 5 This is a current-time plot, which shows the reference variable and the motor current controlled by the soft starter at an onboard voltage of 10.5V. Detailed Implementation

[0029] The trailer hitch according to the invention has a base that can be attached to a towing vehicle. A hook is pivotally attached to the base via a rotary joint. The hook can rotate between a second position (e.g., a parking position behind the bumper) and a first position (e.g., a working position), in which a trailer can be attached. For rotation, the trailer hitch has an electric motor.

[0030] To check if the trailer hitch is in the working position, the motor applies force to the hook in the direction of movement from the parking position to the working position, thus preventing the hook from moving from the working position back to the parking position. When the hook is in the working position, it is pressed against a stop during the test, which increases the motor current. The motor current is determined by the voltage applied to the motor and the motor's electrical characteristics. The motor current is proportional to the force applied by the motor, and the force applied by the motor when the trailer hitch is pressed against the stop always exceeds a specified value. If the specified value is reached within a specified time period, it indicates that the hook is in the working position. If it is not reached, an error exists.

[0031] In order to prevent the trailer hook from being obstructed by the force used to press the hook to its end position when it is to be rotated from the working position to the parking position, the present invention provides a limitation on the force.

[0032] The idea behind this invention is to prevent an increase in retension force during each pulse applied to the motor. This is achieved by limiting the voltage and / or current applied to the motor. Because the torque generated by a DC motor is proportional to the motor current, the best way to ensure a constant force for each pulse is to control the motor current to the desired setpoint or a reference motor current.

[0033] To control the motor current during the pulse, the best approach is to use a PID controller, where:

[0034] - The input will be the error between the reference variable and the measured motor current.

[0035] - The output will be the load cycle of the motor PWM command.

[0036] exist Figure 1 The diagram shows such motor current control. Figure 1 The electronic control unit (ECU) of the so-called trailer towing module (TTM) is shown.

[0037] exist Figure 1 In this context, Iref is the reference variable for the pulse, which must be higher than the minimum current threshold used for retensioning verification; I is the actual motor current of the hook motor measured on the feedback line MOT1_IS_AI; e = Iref - I is the error signal; PID is a proportional-integral-derivative controller; and DC is the load cycle of the motor driver calculated by the controller and set on the control line MOT1_PWM_PO.

[0038] PID feedback control is a control loop mechanism that provides feedback to the controlled motor in the presentation of a continuously calculated error signal e(t), which is the difference between the reference motor current Iref and the measured process variable I.

[0039]

[0040] in:

[0041] ·u(t) represents the output instruction of the PID algorithm, which in this case is a load cycle.

[0042] ·e(t)=Iref(t)-I(t) is the error signal,

[0043] ·K p For proportional gain,

[0044] ·K i For integral gain, and

[0045] ·K d This is the differential gain.

[0046] Because trailer traction modules (TTMs) are typically discrete systems, the discrete transfer function (Z-transform) of a PID controller can be used:

[0047]

[0048] Where Ts is the sampling time, which is 5ms in this case.

[0049] By adjusting the coefficient or gain K p K i and K d This is used to adjust the controller performance in order to obtain the smallest possible error for the controlled current.

[0050] An important aspect to consider is that the controller coefficients need to take into account the entire system, including the mechanical parts of the electrical coupling, not just the electrical characteristics of the coupling motor. Therefore, to determine them, the controller coefficients must also consider all possible tolerances in all areas (mechanical and electrical). An appropriate method for determining the gain is experimental.

[0051] After conducting some measurements using the tested mounting device, we observed the following optimal coefficients for the tested system:

[0052] K p =0.06, K i =0.013, K d =0.0002.

[0053] With an 8.5A reference variable and a 13V supply voltage, the controlled motor current stabilizes at approximately 8.3A, which is higher than the minimum current of 7.2A required for verification testing or retensioning pulses. Under these conditions, the error relative to the reference variable stabilizes at 0.2A, and the load cycle of the PWM motor command stabilizes at around 85%. This is... Figure 2 This was observed in the measurements shown.

[0054] A smoother motor current profile can be obtained by soft-starting with a reference variable within the first 100ms of the test or retension pulse:

[0055] ·t = 0 to 50 ms: Iref1 = 1 / 4 Irefmax

[0056] ·t = 50 to 100 ms: Iref = 1 / 2 Irefmax

[0057] ·t>100ms: Irefmax

[0058] Soft start can be adjusted based on the control application in each application.

[0059] exist Figure 3 The example illustrates the motor current, which is the result of soft-start control using a 13V power supply voltage, and Irefmax = 8.5A. The motor current has a smoother ramp and stabilizes at around 8.4A. In this case, the static error is 0.1A and the load cycle stabilizes at around 86%.

[0060] By performing the same test using different power supply voltages, it can be observed that regardless of the power supply voltage value, the motor current always remains close to the reference variable.

[0061] • 15.8V power supply voltage (vehicle voltage overvoltage limit): error ≈ 0.2A, load cycle ≈ 78% Figure 4 ),

[0062] • 10.5V power supply voltage (undervoltage limit for vehicle voltage): error ≈ 0.7A, load cycle ≈ 97% Figure 5 ).

[0063] Figure Labels

[0064] The reference variable of the Iref pulse

[0065] I Actual motor current

[0066] e Error signal

[0067] u PID output command

[0068] K p proportional gain

[0069] K i Integral gain

[0070] K d Differential gain

[0071] T s Sampling time

[0072] TTM trailer towing module

[0073] ECU (Electronic Control Unit)

[0074] MOT1_IS_AI Feedback Line

[0075] PID Proportional-Integral-Derivative Controller

[0076] MOT1_PWM_PO control line

Claims

1. A trailer hitch for a motor vehicle, comprising: -Base - A hook that can be pivotally attached to the base. - A motor that enables the hook to rotate from a first position to a second position, the first position being a working position in which a trailer can be attached to the hook, and the second position being a parking position in which no trailer can be attached to the hook; - A control unit for controlling the motor, the control unit being able to start the motor via a test pulse such that when the hook is in the first position, a force is applied to the hook having a direction opposite to the direction of movement that moves the hook from the first position to the second position, for testing whether the hook of the trailer hitch is in the first position, and - A current sensor for detecting the current received by the motor during a test pulse, wherein the current sensor is connected to the motor and: the current sensor is connected to an input terminal of the control unit; or the current sensor is part of the control unit and is connected to the motor via a terminal of the control unit. Accordingly, the control unit is programmed to control the current received by the motor during the test pulse, and Accordingly, the control unit includes a controller for controlling the current received by the motor, hereinafter referred to as a current controller, to control the motor current to a desired setpoint or reference motor current. Its features are: Several different current quantities that can be selected as reference variables for the current controller are stored in the control unit. The control unit is programmed such that the stored maximum current exceeds 15% of the minimum amount predetermined as the motor current during the test pulse. The control unit is programmed such that, in order to generate a test pulse, the stored current values ​​are successively selected as reference variables until the highest stored current value is selected. By controlling the motor current, the force applied by the motor to the hook can be limited, which prevents the hook from being blocked in the first position and ensures that the hook can be easily rotated from the first position to the second position if necessary.

2. The trailer hitch-on device according to claim 1, characterized in that, The trailer hitch further includes a DC / DC voltage converter having an input terminal for connection to the vehicle's onboard power system, an output terminal for connection to the motor of the trailer hitch, and a control input terminal for indirect or direct connection to the output of the control unit.

3. The trailer coupling device according to claim 1, characterized in that, The control unit includes an output terminal for the power supply of the motor.

4. The trailer hitch-on device according to claim 1, characterized in that, The current controller is a PID controller.

5. A method for testing whether the trailer hook of the trailer hitch according to any one of claims 1 to 4 is in a first position, characterized in that, Test pulses are generated periodically, which control the motor of the trailer hitch to apply a force to the hook, the force pressing the hook in a direction opposite to the direction of movement that moves the hook from the first position to the second position, wherein the current applied to the motor is controlled during the test pulses.

6. The method according to claim 5, characterized in that, During the test pulse, the current received by the motor is controlled by the current controller.

7. The method according to claim 5, characterized in that, The test pulse has a duration of 400 ms, and the reference variable is gradually increased while controlling the motor current, with each step between the start of the test pulse and the maximum amount of the motor current having a length of 50 ms.

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