DE10304658A1 - Industrial truck - Google Patents

Abstract

Disclosed is a device for controlling the driving stability of an industrial truck and a method for controlling an industrial truck in which the load, the inclination of a mast and a mast, the lifting height of the load, the tipping forces acting on the mast and the longitudinal forces and transverse direction accelerations acting on the vehicle are detected and compared with predetermined limit values. These limit values, which depend on the driving state, cannot be exceeded by the driver at will, so that the tipping stability of the vehicle generally remains in a stable range regardless of the driving state (cornering, driving straight ahead, downhill ...).

Description

The invention relates to a device to ensure driving stability of an industrial truck and a method for controlling an industrial truck.

There is a problem with forklifts in that these are due to their short wheelbase, the small Track width and especially when the load is raised can tilt high center of gravity. In particular, the lateral overturning, caused for example by too high cornering speeds or due to one-sided driving over bumps is one of the most common causes of accidents and demands yearly a large number of injuries and fatalities. On the part of the legislator and the employer is trying to counter this trend with better ones Qualification of the operators and through additional safety systems counteract. So-called are currently on the market passive systems, where using seat belts, side Guard, Side airbags etc. prevents the driver from tipping over of the forklift are thrown out of it and injured. However, these passive systems are only used by the operators accepted unwillingly, as these are in practical use, for example with frequent Get on and off of the operators only very cumbersome are to be handled.

In the EP 916 527 A2 discloses an active system for tipping stabilization of industrial trucks. According to the known solution, these are designed with a rear steerable pendulum axle, which can be locked in critical driving conditions by means of a hydraulic locking device and can thus be made practically a rigid axle. In the known solution, this hydraulic locking device is controlled as a function of the transported load, the signals from a speed sensor and a sensor for detecting the yaw angle and as a function of the approximate height position of the load.

The disadvantage of this solution is that the system can only be used on industrial trucks with four wheels is. Furthermore, there is a considerable outlay in terms of device technology required to the hydraulic locking device for the pendulum axis to integrate. Another disadvantage is that this known system very early intervenes and in certain driving conditions the pendulum axis locks or gives signals to the driver if it is actually still sufficient stability is present, so that the efficiency of the vehicle is reduced.

In contrast, the invention is the Task based on a device for controlling the driving stability of a Industrial vehicle and to create a method for controlling an industrial truck, where the tipping safety with minimal device technology Effort can be improved.

This task is done with regard to Device for controlling the driving stability by the features of the claim 1 and with regard to the method for controlling an industrial truck solved by the combination of features of claim 8.

According to the industrial truck with a variety of sensors, such as an angle sensor for detection the mast inclination, a lifting height sensor for exact detection of a fork position, a force sensor for Detection of tipping forces acting on a mast, a load sensor for Detection of the load of the industrial truck and acceleration sensors for recording vehicle accelerations in longitudinal and executed in the transverse direction. Dependent on from the over the data recorded by the sensors and the previously known vehicle parameters (dimensions, Vehicle, weight (without load), center of gravity) then becomes the actual vehicle condition recorded (center of gravity, accelerations) and with the control system Limit values compared and intervened by the vehicle control system in such a way that these limits are arbitrary, d. H. cannot be exceeded by driver control commands. The driving according to the invention assumes that the center of gravity of the vehicle and the load height and also their state change rates so precisely that over the vehicle control parameters of the vehicle are limited, so that it does not get into a critical state (tilting).

According to the invention, limit values can be set depending on the driving state for the Lifting height, the vehicle speed, the maximum acceleration, the maximum Steering angle, the maximum inclination must be specified.

With very fast changes in driving conditions can still do it be that the specified limit values are exceeded. In this Case will then over the control device intervened directly in the vehicle control and countermeasures initiated to prevent tipping. This however, direct intervention only takes place in the critical case, usually the driving state is over the previously described limit values were kept in a stable range.

The driving safety of the industrial truck can be further improved if the center of gravity in the transverse direction is recorded as precisely as possible. In the case of industrial trucks with a tilting device for the mast that is actuated via two tilt cylinders, it is preferred according to the invention if a force sensor is assigned to each of these tilt cylinders, so that eccentric loads are recorded and are correspondingly incorporated into the control. The respective force sensor does not have to sit directly on the inclination cylinder. It can also be located on the swivel joint between the mast and the chassis or on the mast suspension on the chassis.

According to the invention, the sensors mentioned the center of gravity in the longitudinal axis, the Transverse axis and the vertical axis determined with the formulas according to subclaim 5.

With the help of this very precisely recorded Center of gravity can then, for example, with the in claim 6 specified formulas the current, maximum acceleration when driving straight ahead (Braking, accelerating) or when cornering (acceleration longitudinal and in the transverse direction) and with the measured acceleration values be compared.

In the case where the control unit in critical driving conditions intervenes directly in the vehicle control, this can be done after the in Subclaim 7 table of measures presented in tabular form.

Other advantageous further training the invention are the subject of further dependent claims.

The invention is described below schematic drawings closer explained. Show it:

1 a schematic representation of a counterbalance truck with plotted sizes for calculating the center of gravity;

2 a schematic diagram to explain the tilt stability in the longitudinal and transverse directions;

3 is a schematic representation of the counterbalance truck with sizes for calculating the accelerations in the longitudinal and transverse directions and

4 a stability triangle to explain the tilt stability.

1 shows a highly schematic representation of a counterbalance truck 1 with a driver's cabin 2 , a chassis with a front axle 4 , a steerable rear axle 6 , for example a swing axle and one in the area of the rear axle 6 arranged counterweight 8th ,

There is a mast on the front of the truck 10 with one around an inclination axis 12 tiltable mast 14 stored. The adjustment of the angle of inclination α of the mast 14 takes place via an inclination device with, for example, two inclination cylinders 16 articulated on the vehicle frame and on the mast 14 are attached. There is a fork on the frame-shaped mast 17 slidably guided, the lifting height h _G by means of a schematically indicated lifting cylinder 18 is adjustable.

The stacker is in the illustrated embodiment with a lifting height sensor for detecting the lifting height h _G , an angle sensor for detecting the mast inclination α, force sensors for detecting the tilt cylinder 16 on the mast 14 acting support forces, acceleration sensors for detecting the vehicle acceleration in the longitudinal and transverse axes and a pressure sensor for detecting the from the lifting cylinder 18 applied force equivalent to that on the fork 17 attacking load F _GL is. With these sensors, practically all the variable parameters of the fork lifter required for the control according to the invention can be achieved. record and determine the exact center of gravity and maximum accelerations.

The truck 1 also has a control unit 20 , which can be integrated in the vehicle control system or can be designed as an external module. The signals emitted by the aforementioned sensors are processed in the control unit and are also stored in the memory of the control unit 20 stored limit values and, depending on the result of this comparison, control signals are sent to the hydraulic circuit of the truck or to the engine management.

The effects of mast deflection, tire deflection, fork deflection, etc. were neglected in the calculations explained below. As a result, the tilt limit around the front axle 4 with an inclined mast 14 is actually lower than the calculated value and that the effective lever arm of the load with respect to the inclination axis 12 due to the above-mentioned influencing factors (mast deflection ...) is greater than in the ideal case shown. This error increases with increasing load, lifting height and forward tilt of the mast. With the tipping stability in the transverse direction, the actual tipping stability is higher than the calculated value, because due to the influences mentioned (mast deflection ...) the center of gravity of the load is lower than calculated. However, the influences mentioned are so small that they can be disregarded without significantly influencing the effectiveness of the control system described below.

determination of focus

The center of gravity r _SF and the weight G _{Fz of} the empty truck 1 without mast 14 and fork 17 should be assumed to be known. These sizes are calculated from: G FZ - m FZ ·G With:
M _FZ = mass of the empty vehicle
g = gravitational acceleration
r _SF = (x _SF , y _SF , z _SF ) with
x _SF , y _SF , z _SF center of gravity coordinates.

The center of gravity and the weight of the load plus mast 14 and fork 17 must be determined based on the variable load and is calculated according to: G L = m L ·G With:
m _L : mass of load + mass (fork + mast)
r _SL - (x _SL , y _SL , z _SL ) with
x _SL, y _SL, z _SL center of gravity coordinates of the load plus mast fork).

The mass of the mast is a known parameter of the truck 1 , the load and fork mass can be determined from the signal from the pressure sensor in the lifting cylinder 18 determine. In principle, the mass of the fork is also known, so that the weight of the load can be calculated from the pressure signal.

The total mass of the system and the overall center of gravity are then calculated according to: m = m FZ + m L and r S = 1 / m · (m FZ + r SF + m L · r SL ).

Location of the center of gravity in the longitudinal direction (X axis)

As mentioned above, the center of gravity is the common center of gravity of the load m _L , the fork 17 and the mast 14 , In the longitudinal direction (x-axis), the following applies: 1 the moment balance: F GL .x L = F N · l FN · Sin β With:
F _GL = weight of the load, fork and mast
x _L = lever arm of the center of gravity
F _N via the force sensors of the tilt cylinders 16 detected force (F _N = F _NL + F _NR (R: right tilt cylinder, L: left tilt cylinder))
l _FN : distance of inclination axis 12 , Point of inclination cylinder 16 on the mast 14 β = 90 ° - α + arctan [e.g. AC - l FN · Cos) / (x AC + l FN · Sin α)] With:
z _AC : vertical distance of the vehicle joint from the inclination axis 12 .
x _AC : horizontal distance between the inclination axis 12 and vehicle joint and
l _FN : distance between the inclination axis 12 and mast-side joint of the tilt cylinder 16 (S. 1 ).

The x coordinate of the load center then results from this: x L = (F N · l FN · Sin β) / F GL ,

Location of the center of gravity in the transverse axis (y-axis)

The following applies to the y coordinate of the center of gravity: y S = (F NL / (F NL + F NO )) · A - a / 2 With:
a: Distance between the two force sensors on the tilt cylinders 16 (attached symmetrically to the vehicle)
F _NL : force on the left or right inclination cylinder 16 ,

Location of the center of gravity in the vertical axis (z-axis)

Calculating the z coordinate of the The center of gravity is somewhat more difficult than the ones described above Calculations. This component leaves can only be calculated if the values are at least two different Combined mast inclinations.

In principle, the following applies: z LS = z A + z G + z SG With:
z _A : Height of the inclination axis 12 (Point A) above the ground ( 1 ).
z _G : h _G (see 1 ) · Cos α - tan α · (x _L - h _G + sin α) and
z _SG = h _SG / cos α,
h _G , h _SG s. 1 ,

Neglecting the prescribed load influences, z _{A is known} as a vehicle parameter. The angle of inclination α of the mast 14 is detected via the angle sensor, the lifting height h _G can be detected with the lifting height sensor.

The size h _SG (see 1 ) can be determined by knowing the otherwise tangible values for two different mast inclinations. The fork height h _{G can be} retained, but the calculation also works with different fork heights h _G. The two fork positions should be with the indices 1 and 2 to be marked. Accordingly, the size h _{SG is} calculated according to: H SG = (x L2 - H G2 · Sin α 2 ) / cos α 2 - (x ll - H gl · Sin α 1 ) / cos α 1 tan α 2 - tan α 1

According to the above, the tilt sensor can be determined from the signals from the lifting height sensor, the angle sensor and the force sensors 16 and the known, unchangeable vehicle parameters determine the x, y and z coordinates of the overall center of gravity (vehicle + load) with high accuracy and with minimal effort.

Before calculating the tilt stability in longitudinal and transverse direction explained will, initially on the so-called stability triangle be entered into in

2 for a forklift 1 is shown with load and without load.

The stacker is shown schematically 1 , with its front axle 4 and the steerable rear swing axle 6 , In the event that the truck 1 transported a load, this weight of the load G _{L is} in the direction of travel in front of the front axle 4 , The rear axle 6 is loaded with the counterweight, not shown. The truck 1 with a pendulum axis 6 is in a stable state as long as the center of gravity is statically and dynamically within the dashed triangle of stability, which is characterized by the center distance of the front wheels V _L , V _R and the pivot point of the rear axle H. As long as the center of gravity S calculated according to the above statements is within this stability triangle V _L , V _R , H, there is no danger. From the representation in 2 one recognizes that the danger of tipping in the longitudinal direction is greater with a load G _L than without a load. The tipping stability of the truck carrying a load 1 is however larger than that of the unloaded truck. This can be seen from the distance between the center of gravity S and the adjacent side edge of the stability triangle.

The risk of tipping is next to the static conditions such as the location of the center of gravity and the vehicle inclination also largely determined by the dynamic forces. So decrease braking when driving forward and, conversely, accelerating when reversing the tipping stability. In the Cornering is the component effective in the vehicle's longitudinal direction the centrifugal force backwards towards the rear axle and thus acts over a tipping the front axle opposite.

From the pre-calculated centers of gravity then the accelerations effective at predetermined driving conditions in longitudinal and calculate the transverse direction and use it to determine limit values.

Tilt stability in the longitudinal direction

From the presentation according to 3 can do the torque equation for the front axle 4 be derived. The following applies: F B = ma x = [(F RV + F RH ) R + F G .x SB * z SB With:
F _RV and F _RH : For braking, accelerating to the front axle 4 and the rear axle 6 transferred forces
r: distance of the inclination axis 16 from the ground
x _SB , z _SB see 3
m: total mass of the vehicle
a _x : acceleration in the longitudinal direction.

With the help of the aforementioned equation, a permissible maximum acceleration in the longitudinal direction can then be defined, which essentially depends on the previously calculated center of gravity. A possible vehicle inclination can be determined with those acceleration sensors with which a _{x is} measured. According to the invention, the stacker 1 then controlled in such a way that the actually measured acceleration a _{x is} smaller or at most as large as the maximum value calculated using the above equation.

Tilting stability in the transverse direction

The calculation of the tilting stability in the transverse direction (perpendicular to the plane of the drawing in 3 ) is done with the help of the stability triangle according to 4 ,

As already related to 2 mentioned, are the parameters of the stability triangle of the truck 1 , the wheelbase 1 , the track width b, the angle γ between the leg HV _r (or HV _l ) and the longitudinal axis x of the vehicle and the position of the center of gravity S. For the calculation of the tipping moment in the transverse direction, the distance d of the center of gravity S is accordingly from the respective effective tilting axis - ie when driving left from the HV _r axis - is decisive. This distance d depends on the center of gravity S and the parameters mentioned 1 and b.

The angle γ is then calculated according to: γ = arctan [(b / 2) / 1] , the distance d is calculated according to: d = x S Sin γ.

Neglecting the frictional forces on the tires, the following applies to the moments with respect to the tilt axis HV _r : F G · D = F B * z S With:
z _S see 3
F _G : total weight of the vehicle including load
F _B : Force due to centrifugal acceleration.

With F _B = m · a the centrifugal acceleration can then be calculated according to: a = (F G · D) / (m · z S ).

The components of the centrifugal acceleration effective in the longitudinal and transverse directions can then be calculated from this centrifugal acceleration: a x = a · sin γ. a y = a · cos γ.

Thus, depending on the total weight of the truck, lever arm d and the center of gravity and the angle γ for cornering authoritative Specify maximum accelerations in the transverse and longitudinal directions that from Forklift arbitrarily not exceeded can be.

The stacker sets the limit values for the center of gravity and for the accelerations 1 usually keep in a driving state in which the risk of tipping is minimal. The sensor system described above makes it possible to record these actual values very quickly and precisely, so that continuous monitoring of the driving condition is made possible. Despite these sophisticated sensors, there may be situations where the truck tilts 1 cannot be prevented. Such situations can occur, for example, when driving over a curb. In these cases, the speed of the driving state change is so great that the strategy described above can no longer be used to intervene in good time to drive to keep the state within the specified limit values. In these cases, the vehicle's driving condition must be actively intervened. However, such a direct intervention in the steering or in the driving speed is associated with certain risks, since this intervention can possibly prevent the vehicle from tipping over, but the acceleration or change in the steering angle which the driver does not want can cause other damage. Some intervention options in the critical case, ie when the strategy according to the invention is no longer sufficient to ensure the stability against tipping, are summarized in the following table. This table is not exhaustive, and it is quite possible that, depending on the design of the truck and the requirements of the manufacturer, other strategies or at least only some of the measures summarized in the table are taken to react in the critical case.

As can be seen from the above, certain parameters of the vehicle are limited by the strategy according to the invention for avoiding critical driving states, so that the latter does not get into the critical state at all. The sizes to be restricted are, for example, the lifting height, the vehicle speed, the maximum acceleration, the maximum steering angle, the steering speed and the mast inclination. These parameters are dependent on the driving state via the control unit 20 limited, so that, for example, a further lifting or tilting of the load or an increase in the driving speed is prevented by the control in order to keep the vehicle in the stable range. Depending on the application, other sizes to be restricted can be added.

Disclosed is a device for controlling the driving stability of an industrial truck and a method for controlling an industrial truck, in which the load, the inclination of a sensor system Mast of a mast, the lifting height of the load, the tipping forces acting on the mast as well as the accelerations acting in the longitudinal and transverse directions on the vehicle are recorded and compared with predetermined limit values. The driver cannot arbitrarily exceed these limit values, which depend on the driving state, so that the tipping stability of the vehicle generally remains in a stable range regardless of the driving state (cornering, straight-ahead driving, downhill driving ...).

1

Counterbalanced trucks

2

cab

4

Front

6

rear axle

8th

counterweight

10

mast

12

tilt axis

14

mast

16

tilt cylinder

17

fork

18

lifting cylinder

20

control unit

Claims (8)

Device for ensuring the driving stability of an industrial truck, which is moved by means of a tilting device ( 16 ) tiltable mast ( 14 ) along which a fork ( 17 ) is adjustable in height, and with sensors for detecting operating parameters of the industrial truck, in particular with a load sensor for detecting the load transported by the industrial truck, an angle sensor for detecting the mast inclination, a lifting height sensor for detecting the fork position, a force or pressure sensor for detecting the tilting forces acting on the mast and acceleration sensors for recording vehicle accelerations in the longitudinal and transverse directions and with a control unit ( 20 ), which, depending on known vehicle parameters such as dimensions, weight and center of gravity of the empty vehicle and the variables detected by the sensors, record an actual vehicle state and, depending on the driving state, limit values can be determined which cannot be arbitrarily exceeded when the system is active. Device according to claim 1, wherein the limit values the lifting height, the vehicle speed, the maximum acceleration, the maximum Steering angle or the maximum mast inclination. Device according to claim 1 or 2, wherein the control unit ( 20 ) intervenes directly in the vehicle control in the event of fast, unpredictable changes in driving conditions. Device according to one of the preceding claims, wherein the tilting device two tilt cylinders ( 16 ), to which a sensor is assigned. Device according to one of the preceding claims, wherein the control unit ( 20 ) The center of gravity in the longitudinal and transverse directions (x _L , y _S ) is calculated according to the following equations: x L = (F N · l FN + sin β) / F GL y S = (F NL / (F NL + F NO )) · A - a / 2 with: F _N = support force on the tilt cylinders l _FN = distance of the axis of inclination of the mast from the articulation of the tilt cylinder ( 1 ) β = 90 ° - α + arctan [(e.g. AC - l FN · Cos α) / (x AC + l FN · Sin α)] with: z _AC : vertical distance between the inclination axis ( 12 ) and the vehicle-side pivot point of the inclination cylinder ( 16 ), x _AC : Horizontal distance between the inclination axis ( 12 ) and vehicle-side articulation point of the tilt cylinder ( 16 ). α: angle of inclination of the mast ( 14 ); the center of gravity in the vertical direction (z _SG ) is calculated according to: z S G = h SG / cos α and: H SG = (x LS - H G2 · Sin α 2 ) / cos α 2 - (x L1 - H gl · Sin α 1 ) / cos α 1 tan α 2 - tan α 1 with: indices 1 . 2 : two different fork positions. Device according to one of the preceding claims, wherein the maximum accelerations are calculated as follows: a x = [(F RV + F RH ) R + F G .x SB ] / (e.g. SB · M) with: F _RV and F _RH : acceleration forces transmitted to the vehicle ( 3 ), r: vertical distance of the inclination axis ( 12 ) from the ground, F _G : total weight of the vehicle (load + vehicle empty weight), x _SB : distance of the total center of gravity from the front axle, z _SB : vertical distance of the total center of gravity from the ground and m: total mass of the vehicle (including load). Cornering: a x = (F G + d) sin γ / (mz S ) a y = (F G D) cos γ (mz S ) With d = x S + sinγ x _S = center of gravity in the longitudinal direction γ = angle between the tilt axis (HV _R , V _L ) and the longitudinal axis x. Device according to one of the preceding claims, wherein the control unit ( 20 ) is designed in such a way that in certain driving conditions in which the driving condition-dependent limit values are exceeded, the vehicle control can be intervened as follows to prevent tipping:

Method for controlling an industrial truck, which uses a tilting device ( 16 ) tiltable mast ( 14 ) along which a fork ( 17 ) is adjustable in height, and with sensors for detecting operating parameters of the industrial truck, in particular with a load sensor for detecting the load transported by the industrial truck, an angle sensor for detecting the mast inclination, a lifting height sensor for detecting the fork position, a force or pressure sensor for detecting the tilting forces acting on the mast and acceleration sensors for recording the vehicle acceleration in the longitudinal and transverse directions, and with a control device by means of which the following parameters are recorded and limit values are determined: a) recording the load, the mast inclination, the lifting height, the tilting forces acting on the mast and acceleration in the x and y directions. b) Calculating the center of gravity in the longitudinal and transverse directions of the vehicle as a function of the values recorded via the sensors and of known vehicle characteristics. c) Calculating maximum accelerations in the longitudinal and transverse directions when driving straight ahead: a x - [(F RV + F RH ) R + F G .x SB ] / (e.g. SB · M) with: F _RV and F _RH : acceleration forces transmitted to the vehicle ( 3 ), r: vertical distance of the inclination axis ( 12 ) from the ground, F _G : total weight of the vehicle (load + vehicle empty weight), x _SB : distance of the total center of gravity from the front axle, z _SB : vertical distance of the total center of gravity from the ground and m: total mass of the vehicle (including load); Cornering: a x = (FG + d) · sin γ / (m · z S ) a y = (FGd) cos γ (mz S ) with: d = x _S + sin γ x _S = center of gravity in the longitudinal direction γ = angle between the tilt axis (H-VR, VL) and the longitudinal axis (x) and d) adjustment of the changeable driving state parameters such that the in ( 3 ) calculated limit values are not exceeded.