Industrial truck with a holding brake and method for adjusting a holding torque on an industrial truck

Abstract

Industrial truck with a holding brake, a setpoint generator that generates a setpoint for the travel speed, and a travel control unit that controls a travel drive in response to the setpoint for the travel speed, characterized in that - the drive control system regulates a holding torque for the drive when the setpoint encoder is not actuated, whereby the unactuated setpoint encoder specifies a travel speed of zero as the setpoint, whereby the holding torque, which keeps the industrial truck stationary on an inclined surface, actuates the holding brake and deactivates the drive when the holding brake is actuated, and - that the driving control unit, upon renewed activation of the driving setpoint encoder, reactivates the drive unit to generate the regulated holding torque and releases the holding brake, wherein an inclination sensor is provided that detects an inclination of the ground and a steering control unit determines a relative angle between the direction of action of the steerable drive unit and the incline direction when the holding torque is regulated and when the holding brake is released, wherein the driving control unit corrects the stored control variables according to the determined relative angles.

Description

[0001] The present invention relates to an industrial truck with a holding brake, a travel setpoint generator that specifies a setpoint for the travel speed, and a drive control that controls a drive motor in response to the setpoint for the travel speed. The invention also relates to a method for adjusting a holding torque in an industrial truck equipped with a travel drive and a brake.

[0002] Electrically powered industrial trucks are also used for loading and unloading trucks, where the truck can approach the truck on a loading ramp. Loading ramps can have a gradient of up to 20%. To ensure the most comfortable and safe maneuvering on the loading ramp, it is desirable for the truck to actively maintain its incline when the speed setpoint sensor is not activated.

[0003] Actively holding the industrial truck on a loading ramp can be ensured by using a speed or torque control for the drive. However, for energy and thermal reasons, maintaining an active hold state for an extended period of time is not advisable, as this could lead to overloads, especially when the truck is loaded.

[0004] DE 197 52 022 A1 discloses an industrial truck with an electric drive and a parking brake. The parking brake is designed as a spring-loaded brake that can be connected to release the hydraulic pump's delivery line. The spring-loaded brake is automatically applied to the braking position when the operator dismounts and / or when the drive is not actuated.

[0005] From DE 10 2010 018 463 A1, a control method for an automated parking brake of an industrial truck that can be actuated by a control system has become known, the control system of which, when the industrial truck is stationary, detects a missing signal from a travel speed sensor after the expiry of a travel signal waiting time as a braking state.

[0006] The invention is based on the object of providing an industrial truck and a method for setting a holding torque for such a truck, which allows the vehicle to stand on a ramp using simple means without overheating or overloading the drive or the control system.

[0007] According to the invention, the object is achieved by an industrial truck having the features of claim 1. The object is also achieved by a method having the method steps according to claim 12. Advantageous embodiments form the subject matter of the subclaims.

[0008] The industrial truck according to the invention is equipped with a holding brake, a travel setpoint generator, and a travel controller. The travel setpoint generator generates a setpoint for the travel speed. The travel controller controls a travel drive according to the specified setpoint. According to the invention, the travel controller is designed such that, when the travel setpoint generator is not actuated, a holding torque for the travel drive is regulated, which holds the vehicle stationary on an inclined or sloping surface, even against a downhill force. The regulated holding torque for the travel drive ensures that the vehicle remains stationary. Furthermore, the travel controller is designed to actuate a holding brake and to deactivate the travel drive when the holding brake is actuated.In this way, the industrial truck according to the invention is actively held stationary by the drive control until a holding brake applies the necessary holding torque and the drive is deactivated with the holding brake applied. According to the invention, in order to avoid jerky movement of the vehicle when starting up again, the drive control, upon renewed actuation of the travel setpoint sensor, again activates the drive to generate the holding torque and releases the holding brake. The drive control according to the invention thus avoids jerky movement of the industrial truck by applying the regulated holding torque to the drive before the holding brake is released, and then, based on this holding torque, further control of the travel speed takes place according to the travel setpoint sensor.The holding brake is only released by the inventive drive control system when the holding torque set when the vehicle is stationary is applied to the drive. The inventive drive control system prevents overheating of the drive, since when the industrial truck is stationary, there is no active holding via the drive; instead, the holding brake takes over this function.

[0009] In a preferred embodiment, the drive control stores the control variables for generating a regulated holding torque and, based on the control variables, generates the holding torque again when the drive setpoint generator is actuated again. Depending on the type of drive control, a torque value and / or a value for the torque-generating current are preferably provided as control variables. By reactivating the stored control variables for the regulated holding torque, the drive control can ensure that when the vehicle is driven off again by actuating the drive setpoint generator, the holding torque present at the drive drive is already sufficiently large to move the vehicle from a standstill.When the travel setpoint generator is actuated again, the holding torque is not adjusted again from an arbitrary starting value for the holding torque, but the travel control with the control of the travel drive begins at the already adjusted value for the holding torque.

[0010] In a preferred embodiment of the invention, the drive control activates the holding brake if the setpoint transmitter has not been activated for a predetermined period of time. Thus, during short downtimes of the industrial truck, the standstill is actively controlled. Only after the predetermined period of time has elapsed does the drive control save the values ​​for generating the controlled holding torque and activate the holding brake.

[0011] In a preferred embodiment, the industrial truck according to the invention is equipped with a load sensor that detects a change in the load while the holding brake is applied. For this purpose, the load is detected when the holding torque is set and when the travel setpoint sensor is reactivated. The travel control system corrects the stored control variables to the set holding torque when the load changes. Such a correction is based on the consideration that an industrial truck that is loaded while stationary requires a greater actively generated holding torque when the holding brake is released than the holding torque set for the unloaded industrial truck. Likewise, the required holding torque is lower if the set holding torque refers to the loaded industrial truck and the truck is fully or partially unloaded when the travel setpoint sensor is reactivated.Here, the stored control variables for generating the holding torque are preferably corrected such that the holding torque increases if the load has increased during standstill and decreases if the load has decreased while the vehicle is stationary. The correction of the stored control variables for generating the holding torque is preferably carried out using a load correction factor, which is calculated from the changed load and applied multiplicatively to the control variables.

[0012] In addition to situations in which the load picked up by the industrial truck changes during the standstill phase, the drive control according to the invention can also alternatively or additionally detect situations in which a steering angle on the industrial truck has changed during the standstill phase. This embodiment is intended in particular for industrial trucks with a steerable drive. In this development, a steering sensor detects a steering movement while the holding brake is applied. The drive control then corrects the stored control variables according to the change in the steering angle. Here, too, a steering angle correction factor is preferably used, which is determined from the changed steering angle and multiplied by the stored control variables to generate the holding torque.

[0013] In addition to the above correction due to a change in the steering angle, in a further preferred embodiment the position of the steering angle relative to a gradient angle can also be taken into account. This development is particularly relevant for industrial trucks equipped with an inclination sensor that can detect an inclination of the ground. The steering control determines a steering gradient correction factor based on a relative angle between the effective direction of the steerable drive and the gradient direction. The drive control corrects the stored control variables according to the relative angle when the holding torque is adjusted and when the holding brake is released. Unlike the steering correction factor, for which only a change in the steering angle had to be recorded, a relative angle with a adjusted holding torque and a relative angle when the holding brake is released must be taken into account to determine the steering gradient correction factor.

[0014] The object of the invention is also achieved by a method having the features of claim 12.

[0015] The method is used to set a holding torque on an industrial truck that has a travel drive and a holding brake. According to the invention, the holding torque on the travel drive is adjusted in such a way that when the travel setpoint sensor is not actuated, the truck is held stationary on inclined or sloping ground. The holding brake is also actuated and the travel drive is deactivated. When the travel setpoint sensor is actuated again, the adjusted holding torque is applied to the travel drive and the holding brake is released. The method according to the invention ensures that when the holding brake is released, the adjusted holding torque is immediately applied again to the travel drive of the industrial truck, so that the setpoint specified by the travel setpoint sensor can be implemented by the travel drive almost smoothly and without the truck starting to move on an incline.

[0016] In a preferred embodiment of the method according to the invention, after adjusting the holding torque, control variables for generating the holding torque are stored, and upon renewed actuation of the travel setpoint generator, control variables based on the stored control variables are applied to the travel control system. To prevent activation of the holding brake during short-term stops, a preferred embodiment of the method provides that, when the setpoint generator is not actuated, the holding brake is actuated and the travel drive is deactivated only after a predetermined period of time. This ensures that only short-term stops are actively controlled, and the holding brake is only actuated during longer stops.

[0017] In a preferred development of the method according to the invention, a change in a picked-up load is detected while the travel setpoint sensor is not actuated. The value of the holding torque to be applied upon renewed actuation of the travel setpoint sensor is increased if the picked-up load has increased. Likewise, the value of the holding torque to be applied upon renewed actuation of the travel setpoint sensor is decreased if the load picked up by the industrial truck has decreased.

[0018] A preferred development of the method according to the invention provides for industrial trucks with a steerable drive to detect a steering movement while the travel setpoint transmitter is not actuated and the holding brake is activated, and to correct the value of the holding torque upon re-actuation of the travel setpoint transmitter, depending on the angle of change for the steering movement. In this development of the method, the stored holding torque is corrected accordingly in accordance with a change in the steering angle.

[0019] A further preferred embodiment of the method according to the invention is used in an industrial truck with a steerable drive system, which also has an inclination sensor that can detect the inclination of the ground. In this further development of the method, a relative angle between an incline and an effective direction of the steerable drive system is determined. The relative angle is recorded when the holding torque is adjusted and when the holding brake is released. The value of the holding torque to be applied when the travel setpoint sensor is actuated again is recorded as a function of the two values ​​of the relative angle, with a first relative angle being recorded when the holding torque is adjusted and a second relative angle being recorded when the travel setpoint sensor is actuated again.

[0020] The invention is explained in more detail below using an exemplary embodiment. It shows: Fig. 1 a flowchart describing step by step the procedure for reactivating a holding torque on an industrial truck, Fig. 2 a perspective view of an industrial truck and Fig. 3 a schematic view of the steering angle.

[0021] The method according to the invention proceeds according to Fig. 1 from a process step 10 in which the speed setpoint generator is not activated. In the schematic representation, this means that the specified setpoint for the speed is 0 (v soll = 0).

[0022] In a subsequent step 12, the drive control regulates an active holding torque M halt in such a way that the vehicle is stationary (v 1st = 0). If this is the case (query 13), a counter t is started in a subsequent step 14.

[0023] A query 15 checks, based on the started counter t, whether a predetermined time period T has already been exceeded. If the time period T has not been exceeded, the process returns to active control in step 12. If the time period T has been exceeded, the currently applied holding torque M halt stored (step 16), a holding brake on the industrial truck is activated (step 17) and the holding torque M generated by the drive control halt deactivated (step 18).

[0024] The following query 19 checks whether the speed setpoint generator is still not activated. In the event that the speed setpoint generator is activated (v soll ≠ 0), in a subsequent step 22 the holding torque M stored in step 16 is halt applied to the drive again. When holding torque M haltThe holding brake is then released in step 23. The vehicle is now ready to drive according to the specifications of the drive setpoint generator and to control the drive accordingly.

[0025] If it is determined in query 19 that the travel setpoint generator has still not been activated, the process remains in the state of inactive travel control and activated holding brake.

[0026] The holding torque M determined in step 12 halt is stored in the method according to the invention so that the value of the holding torque can be reactivated in step 22.

[0027] If there is a delay between the storage of the adjusted holding torque M halt in step 16 and the reactivation of the controlled holding torque M halt If the total weight of the vehicle has changed in step 22, the load change is recorded for vehicles with a load sensor and a load correction factor k is calculated in step 20.last This correction factor is then calculated in step 21 to the holding torque M stored in step 16. halt applied to determine a corrected holding torque for reactivating the vehicle control in step 22. A possible load correction value could be, for example: klast=mVzg+mneumVzg+malt, where m Fzg a known vehicle unladen mass, m alt the load when adjusting the holding torque and m neu the load at the time of drive reactivation.

[0028] As an alternative to the above load correction factor, a load change Δm = m alt - m neu when determining the load correction factor.

[0029] If no load sensing is available for correcting the holding torque, or if the correction is inaccurate, an increase in load will result in the vehicle moving downhill, but this will be significantly less than without the activation of the stored holding torque, since only the difference absorbed by the additional load needs to be adjusted. A reduction in load, with low setpoint values ​​for the travel speed, may lead to acceleration beyond the setpoint. Such an excessive travel speed can be detected and adjusted early on in an industrial truck, allowing for a virtually smooth transition to travel mode.

[0030] Another special feature of the method according to the invention occurs especially with steerable drive systems. Due to steering movements between the time at which the holding torque was stored (step 16) and the time at which the stored holding torque is to be reactivated (step 22), the effective direction of the drive motor can change during a steering movement and thus no longer corresponds to the direction of the load torque caused by the downhill force on the industrial truck. The consequences of this mismatch can be illustrated by two extreme cases: - The industrial truck stopped on an uphill section in such a way that the downhill force acts along the vehicle's longitudinal axis toward the rear. Rotating the drive by 90° would place the drive wheel perpendicular to the slope, and the reactivated holding torque would no longer counteract the downhill force, but would instead lead to an unintentional lateral movement of the truck on the uphill section. - The industrial truck stopped on an uphill section in such a way that the downhill force acts along the vehicle's axle toward the rear. By rotating the drive system by 180°, the alignment of the drive axle to the downhill slope is identical to the alignment when adjusting the holding torque, but the sign has changed, and reactivating the original holding torque would incorrectly accelerate the truck downhill when starting off, instead of actively holding it on the incline.

[0031] These effects can be prevented by adjusting the change in the steering angle Δα between storing the holding torque (step 16) and reactivating the holding torque (step 22) by a correction factor k lenk according to k lenk = cos (Δa). The factor thus determined ensures that the holding torque corrected in step 21 is always less than or equal to the stored holding torque. The following correction factors result for the described cases: klenk=cos(± 90°)=0 and klenk=cos(± 180°)=−1.

[0032] These cases result in the corrected holding torque value being 0 for the transversely positioned drive wheel (Δα = ± 90°), preventing the vehicle from moving sideways. The other case, with Δα = ± 180°, also reverses the holding torque, so that the generated holding torque acts in the correct direction.

[0033] Fig. 3 shows a steered drive wheel 26 on an industrial truck 28 ( Fig. 2), which forms an angle α with a central longitudinal axis 29. The vehicle is supported by a pair of load wheels 30, which are aligned in the direction of the central longitudinal axis 29.

[0034] In a further development of the method, the industrial truck is equipped with an incline sensor that determines the angle at which the incline was traveled and the angle of the drive wheel to it. This allows for the situation where the drive wheel is rotated from a position at an angle to the incline into or out of the incline while stationary between steps 16 and 22, whereby the required holding torque increases or decreases during correction. A possible steering incline correction factor k LS is for example: kLS=cos(αnew)cos(αold), where α neuthe relative angle between the effective direction of the drive wheel and the gradient direction when the travel setpoint generator is reactivated and α alt the corresponding relative angle when adjusting the holding torque.

[0035] In the formula provided, the case of cos(α alt ) approximately = 0. In this case, the desired correction factor k can be determined based on an approximation LS can be determined by removing the pole point.

Claims

[1] Industrial truck with a holding brake, a travel setpoint generator that generates a setpoint for the travel speed, and a travel control that controls a travel drive in response to the setpoint for the travel speed, characterized by , that - the drive control sets a holding torque for the drive when the drive setpoint generator is not actuated, whereby the drive setpoint generator when not actuated specifies a travel speed of zero as the setpoint, whereby the holding torque that keeps the industrial truck stationary on an inclined surface actuates the holding brake and deactivates the drive when the holding brake is actuated, and - that when the travel setpoint generator is actuated again, the travel control again controls the travel drive to generate the adjusted holding torque and releases the holding brake, wherein an inclination sensor is provided which detects an inclination of the ground and a steering control determines a relative angle between the effective direction of the steerable travel drive and the direction of the gradient when the holding torque is adjusted and when the holding brake is released, wherein the travel control corrects the stored control variables in accordance with the determined relative angles. [2] Industrial truck according to claim 1, characterized by that the drive control stores the control variables for generating the regulated holding torque and generates the holding torque again based on the stored control variables. [3] Industrial truck according to claim 1, characterized bythat the drive control stores a value of the torque and / or a value for the torque-generating current for the regulated holding torque as a control variable. [4] Industrial truck according to one of claims 1 to 3, characterized by that the drive control activates the holding brake if the drive setpoint generator has not been operated for a predetermined period of time. [5] Industrial truck according to one of claims 2 to 4, characterized by that a load sensor detects a change in the load while the holding brake is actuated and the drive control corrects the stored control variables according to a recorded load when adjusting the holding torque and when the drive setpoint generator is actuated again. [6] Industrial truck according to claim 5, characterized bythat the stored control variables for generating the holding torque are corrected in such a way that the holding torque is increased when the load is increased and the holding torque is reduced when the load is reduced. [7] Industrial truck according to claim 6, characterized by that the drive control determines a load correction factor from the changed load, which is multiplied by the stored control variables to generate the holding torque. [8] Industrial truck according to one of claims 1 to 7, characterized by that a steerable drive is provided and a steering sensor detects a steering movement while the holding brake is applied, whereby the drive control corrects the stored control variables according to the change in the steering angle. [9] Industrial truck according to claim 8, characterized bythat the drive control determines a steering angle correction factor from the changed steering angle, which is multiplied by the stored control variables to generate the holding torque. [10] Industrial truck according to claim 1, characterized by that the steering control determines a steering pitch correction factor from the relative angles when the holding torque is adjusted and when the holding brake is released, which is multiplied by the stored control variables to generate the holding torque. [11] Method for setting a holding torque in an industrial truck having a drive and a holding brake, comprising the following method steps: - Adjusting a holding torque on the travel drive in such a way that, when the travel setpoint sensor is not actuated, the industrial truck is held at a standstill on an inclined surface, whereby the travel setpoint sensor, when not actuated, specifies a travel speed of zero as the setpoint, - Applying the holding brake and deactivating the drive, - Applying the controlled holding torque to the travel drive and releasing the holding brake when the travel setpoint transmitter is actuated again, whereby the industrial truck has a steerable travel drive and an inclination sensor and the method has the following further steps: - Determining a relative angle between gradient and direction of action of the steerable drive, - Detection of a relative angle with controlled holding torque and when the holding brake is released and - Correcting the value of the holding torque to be applied depending on the two values ​​of the relative angle. [12] Method according to claim 11, characterized by that after adjusting the holding torque, control variables for generating the holding torque are stored and when the travel setpoint generator is actuated again, the holding torque is generated again based on the stored control variables. [13] Method according to claim 11 or 12, characterized by that when the travel setpoint generator is not actuated, the holding brake is actuated and the travel drive is deactivated after a predetermined period of time. [14] Method according to one of claims 11 to 13, characterized by Detecting a change in an absorbed load while the travel setpoint generator is not actuated and increasing the value of the holding torque to be applied if the absorbed load has increased and decreasing the value of the holding torque to be applied if the absorbed load has decreased. [15] Method according to one of claims 11 to 14 for an industrial truck with a steerable drive, characterized by Detecting a change in the steering angle while the drive setpoint transmitter is not actuated and correcting the value of the holding torque to be applied depending on a change in the steering angle.

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