DE102011076816A1 - Method for controlling and regulating electric traction drive of industrial truck e.g. forklift, involves controlling vehicle speed based on vehicle reference speed in dependence on comparison of rotational speeds of vehicle wheels - Google Patents

Abstract

The method involves generating a torque for acceleration or deceleration of an industrial truck using the driving current for an electric traction drive (2). The radius (r) of a non-driven vehicle wheel (5) and a driven vehicle wheel (6) is determined and the vehicle speed is controlled with respect to the vehicle reference speed in dependence on a comparison of the rotational speeds of the non-driven vehicle wheel and driven vehicle wheel. An independent claim is included for industrial truck.

Description

The present invention relates to a truck and a method for controlling and / or regulating an electric traction drive of a truck according to the closer defined in the preamble of claim 1 and 7, respectively.

For example, in the not yet published application DE 10 2011 004 813.8 The applicant describes a brake actuation unit and a method for adjusting a brake force by means of the brake actuation unit in an industrial truck. The brake operating unit described serves as a holding and emergency stop brake for the truck, in which a continuous adjustment of the maximum braking torque is possible.

In electrically driven industrial trucks, the driver of the vehicle gives a central control by means of the accelerator pedal an input signal for driving the traction drive. This input signal is processed by the controller and provides a corresponding traction current for the traction drive comprising a drive motor. The drive torque generated by the drive motors or by the traction drive increases with the traction current provided by the control. However, the maximum torque which can be transmitted to the ground by the impeller or drive wheel is dependent on the wheel load and the coefficient of friction between the drive wheel and the ground. If the generated drive or deceleration torque provided by the traction drive is greater than the torque transmittable between the drive wheel and the ground, a slip occurs between the drive wheel and the ground, which can lead to critical driving conditions. In addition, the wear on the drive wheels increases, which is costly.

Accordingly, the present invention is based on the object to propose an industrial truck and a method for driving a traction drive of a truck of the type described above, in which the control of the truck is improved so that a reduced to a minimum slip on the drive wheels due to the generated Torque to accelerate or decelerate occurs on the truck.

This object is achieved by the features of claim 1 and 7 respectively. Further advantageous embodiments will become apparent in particular from the respective dependent claims and the drawings and the associated description.

The object of the invention is on the one hand procedurally achieved in that at least the traction current or drive power of the power electronics for example, at least one electric motor drive for generating a corresponding acceleration or deceleration torque of the truck depending on a comparison of at least one non-driven vehicle wheel detected actual vehicle speed and the determined at least one driven vehicle wheel theoretical vehicle target speed is controlled. The object underlying the invention is achieved in terms of apparatus in that a truck is proposed that for detecting the respective speed at least one non-driven vehicle wheel and at least one driven vehicle wheel at least one speed sensor or the like is coupled to the central control, wherein the Central control by means of other input signals or input variables, for example, the respective radius of the vehicle wheel or the like, a difference between the actual vehicle speed and a theoretical target vehicle speed can determine to allow a skip detection.

In particular, in industrial trucks, such as forklifts or the like, not only load-dependent or payload dependent significantly fluctuating wheel loads on the vehicle wheels but it also results Reibwertschwankungen between the driven vehicle and the ground. As a result, the maximum transmissible torque between the drive wheel and the ground changes. Due to the speed measurement on the drive wheels and the non-driven wheels, any friction coefficient fluctuations that may occur when controlling the travel drive can be taken into account. Upon reaching a predetermined speed difference or speed difference between the driven wheels and the non-driven wheels of the traction current of the traction drive to prevent or reduce slip on the vehicle wheels can be lowered accordingly. As a result, a change in the coefficient of friction between each driven vehicle wheel and the ground in the control of each traction drive of the truck is taken into account in an advantageous manner according to the invention.

When calculating the actual speed of the vehicle by means of the speed at non-driven vehicle wheels and the vehicle target speed with the aid of the speed at driven vehicle wheels, different input variables can be taken into account. For example, the measurement of the steering angle and / or a payload-dependent deformation at the vehicle wheels are taken into account. As a result, the flattening of the vehicle wheels caused by the payload can be taken into account, as the effective radius of the vehicle wheel is changed by this flattening.

The present invention will be further explained with reference to the drawings, in which various possible embodiments of a material handling vehicle are shown by way of example. Show it:

1 a schematic view of a designed as a front-wheel drive forklift truck in the loaded state with speed sensors for detecting the rotational speeds of the vehicle wheels;

2 a schematic view of an unloaded forklift with a rear side arranged counterweight;

3 a schematic view of the forklift according to 2 in the loaded condition; and

4 a schematic view of the forklift according to 1 with an additional pressure sensing on the lifting cylinder of the payload carrying mast.

In the figures, various embodiments of an industrial truck according to the invention as a forklift 1 . 1A . 1B exemplified. At the forklift 1 . 1A . 1B can be a payload 2 with a mast 3 be recorded. The total vehicle mass and also the load on the vehicle wheels 4 . 5 can vary considerably depending on the load condition. The forklift 1 . 1A . 1B includes at least one electric traction drive 6 that with at least one driven vehicle wheel 4 coupled to the forklift 1 . 1A . 1B at least one non-driven vehicle wheel 5 is provided. With the electric drive 6 becomes a desired torque for accelerating or decelerating the forklift 1 . 1A . 1B generated.

The size of the electric drive 6 provided acceleration or deceleration torque is by a predetermined traction current of a central controller or a central controller 7 set. The driver of the electrically driven forklift 1 . 1A . 1B transmitted to the controller 7 using the accelerator pedal 15 an input signal. The central control 7 processes this and other input signals and determines the appropriate traction current for the electric traction drives or 6 of the forklift 1 . 1A . 1B , The electric drive 6 converts the electrical energy into mechanical energy. Depending on the respective wheel load and the coefficient of friction on the driven vehicle wheels 4 can use the mechanical energy to accelerate or decelerate the forklift 1 . 1A . 1B be used.

At the in 1 illustrated forklift 1 is a steering drive 8th provided, which in the illustrated embodiment z. B. the rear, non-driven vehicle wheels 5 directs. The steering drive 8th is with a steering angle sensor 9 equipped, the the respective steering angle of the vehicle wheels 5 detected. In addition, the respective speeds of all vehicle wheels 4 . 5 with correspondingly assigned speed sensors 10 . 10A be recorded. The measured speeds of the non-driven vehicle wheels 5 and the powered vehicle wheels 4 and the detected steering angle of the steering angle sensor 9 serve as additional input variables for the controller 7 ,

In the context of the method according to the invention, the controller performs 7 a plausibility check by assuming that at the non-driven vehicle wheels 5 no slip occurs, as well as no acceleration or deceleration of the electric traction drive 6 is transmitted. The speeds of the non-driven vehicle wheels 5 can thus be quasi set as the actual value, from which the controller 7 the actual vehicle speed is determined. Further, using the speeds of the driven vehicle wheels 4 a vehicle target speed can be calculated.

If the calculated actual vehicle speed deviates from the theoretical vehicle target speed, it can be assumed that the driven vehicle wheels 4 spin and thus slip between the driven vehicle wheels 4 and the floor 11 occurs. The central control 7 then regulates the maximum traction current for the electric traction drive 6 such that slip on the powered vehicle wheels 4 is avoided. Instead of comparing the vehicle speeds, the measured speeds of the driven vehicle wheels 4 and the non-driven vehicle wheels 5 are compared when the radius r and the steering angle in the vehicle wheels to be compared 4 . 5 is known. The speed ratio of the driven vehicle wheels 4 and the non-driven vehicle wheels 5 depends, among other things, on the steering angle, the state of wear and the change in the effective radius r due to different loading conditions.

In 2 is an unloaded forklift 1A shown. Due to the counterweight 12 located at the rear of the forklift 1A is the focus 13 of the unloaded forklift 1A moved accordingly in the stern direction. The wheel load on the front vehicle wheel 4 As a result, it is low. That's why the front vehicle wheel is on 4 also the flattening low. The radius r of the front vehicle wheel 4 is accordingly large. At the rear vehicle wheel 5 gets through the far back center of gravity 13 unloaded forklift truck 1A realized a larger flattening, so that the effective radius r of the rear vehicle wheel 5 therefore smaller.

3 shows the in 2 illustrated forklift 1A in the loaded state, as a corresponding payload 2 on the mast 3 is provided. The payload 2 leads to a forward shifted center of gravity 13 , As a result, the front vehicle wheel is 4 flattened due to the high wheel load. The effective radius r of the front vehicle wheel 4 of the loaded forklift 1A is lower than compared to the unloaded forklift 1A in 2 , The rear vehicle wheel 5 of the loaded forklift 1A according to 3 becomes due to the forward shifted center of gravity 13 relieved. Thus, the flattening of the rear vehicle wheel 5 of the loaded forklift 1A in 3 less than the flattening of the rear vehicle wheel 5 at the unloaded forklift 1A according to 2 , The effective radius r of the rear vehicle wheel 5 of the loaded forklift 1A is greater than the radius r of the rear vehicle wheel 5 unloaded forklift truck 1A according to 2 , As a result, the speed ratios between the vehicle wheels change 4 . 5 depending on the payload 2 , Because the method according to the invention takes this change into account, the tolerance threshold for the slip detection can be set low.

In order to realize a Nutzlasterkennung in the truck, the in 4 illustrated forklift 1B in addition to the speed measurement on the driven vehicle wheels 4 and the non-powered vehicle wheels 5 equipped with a payload detection. This is due to the payload 2 generated pressure in a lift cylinder 14 of the mast 3 measured. The detected pressure in the lifting cylinder 14 is approximately proportional to the intended payload 2 , When the measured pressure in the form of an input signal of the central control 7 is provided, the effective radii r on the vehicle wheels 4 . 5 be calculated at least approximately. In this way, the effective radii r in the vehicle speed calculation or the rotational speed measurement of the driven vehicle wheels 4 and the non-driven vehicle wheels 5 be taken into account. Thus, the maximum possible slip between the driven vehicle wheels 4 and the floor 11 be further reduced.

The respective flattening of a vehicle wheel 4 . 5 For example, via a sensor for detecting a distance between a vehicle frame fixed point of the forklift 1 . 1A . 1B and the wheel contact surface or the floor 11 at the respective vehicle wheel 4 . 5 be determined, the sensor z. B. with the central controller 7 is coupled to transmit the corresponding input signals. As a sensor, optical, ultrasound-based or the like sensors can be used.

Overall, with the invention due to the minimization of slippage between the driven vehicle wheels 4 and the floor 11 An unnecessary wheel wear prevented and driving safety can be increased. In addition, there is always an optimal acceleration or deceleration torque on the electric traction drive 6 to disposal. As the speeds of the driven vehicle wheels 4 and the non-driven vehicle wheels 5 can be measured and calculated from the measured values of the slip can be prevented in the truck according to the invention, the charge-dependent and / or Reibwertabhängig occurring slip.

LIST OF REFERENCE NUMBERS

1, 1A, 1B

fork-lift truck

2

payload

3

Lifting

4

driven vehicle wheel

5

non-driven vehicle wheel

6

electric traction drive

7

central control or controller

8th

steering drive

9

Steering angle sensor

10, 10A

Speed sensor

11

ground

12

counterweight

13

main emphasis

14

lifting cylinder

15

accelerator

r

effective, effective radius

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011004813 [0002]

Claims (10)

Method for controlling and / or regulating at least one electric traction drive ( 2 ) of an industrial truck, characterized in that the traction current for the traction drive ( 2 ) for generating a torque for accelerating or decelerating the truck at least as a function of a comparison of the rotational speed and the radius (r) of at least one non-driven vehicle wheel ( 5 ) determined from the speed and the radius (r) of at least one driven vehicle wheel ( 6 ) determined vehicle target speed is controlled. A method according to claim 1, characterized in that the traction current of the traction drive ( 6 upon reaching a predetermined difference between the actual vehicle speed and the vehicle target speed for preventing slip on at least one driven vehicle wheel ( 4 ) is lowered. A method according to claim 1 or 2, characterized in that when driving the traction current on at least one steerable vehicle wheel ( 5 ) is taken into account. Method according to one of the preceding claims, characterized in that in the control of the traction current, a payload-dependent deformation of at least one vehicle wheel ( 4 . 5 ) is taken into account. Method according to Claim 4, characterized in that an effective radius (r) of each vehicle wheel resulting from the payload-dependent deformation (r) ( 4 . 5 ) is calculated. Method according to claim 5, characterized in that the payload ( 2 ) from one to a lifting cylinder ( 14 ) of the truck acting pressure is determined. Industrial truck with at least one electric drive ( 6 ) for generating a torque for accelerating or decelerating at least one driven vehicle wheel ( 4 ), whereby the traction drive ( 6 ) via a central controller ( 7 ) is coupled for setting a traction current, characterized in that the central controller ( 7 ) with at least one rotational speed sensor ( 10 . 10A ) for detecting the respective rotational speed on at least one non-driven vehicle wheel ( 4 ) and at least one driven vehicle wheel ( 5 ) is coupled. Truck according to claim 7, characterized in that the central control ( 7 ) with at least one steering angle sensor ( 9 ) for detecting a steering angle of an associated vehicle wheel ( 5 ) is coupled. Truck according to claim 7 or 8, characterized in that the central control ( 7 ) with at least one lifting cylinder ( 14 ) for detecting by the payload ( 2 ) Acting pressure is coupled. Truck according to one of claims 7 to 9, characterized in that the central control ( 7 ) with at least one sensor for detecting a distance between a vehicle frame fixed point and the wheel contact surface of the associated vehicle wheel ( 4 . 5 ) is coupled.

Images