EP1985576B1 - Method and device for preventing a counterweight forklift tipping over - Google Patents

Description

The invention relates to a method for tilting prevention of a counterbalance truck with an internal combustion engine as a drive machine according to claim 1.

Counterbalance trucks have a front drive axle with two driven wheels. The rear axle is the steering axle and has at least one steered wheel. Especially when cornering there is a risk of tipping over of the vehicle, especially when a load is absorbed and this has a certain height, whereby the overturning moment is amplified. Various devices and methods for preventing tilting of road vehicles or forklifts have become known. In DE 29 09 667 C3 a device for a tilt prevention for a electric counterbalanced forklift with two-wheeled front-wheel drive is described. The steering angle determines the degree of permissible driving speed. This limits the maximum specifications of the two drive speed controllers. Exceeding leads to a significant regenerative deceleration.

In DE 100 35 180 B4 the steering angle and the steering speed and the vehicle speed are measured and intervened in the distribution of the drive power, that the rotation rate (angular velocity about the lifting axis) of the vehicle is reduced.

In DE 200 23 781 U1 Steering angle or steering wheel angle and driving speed are measured and a clutch actuated when a critical value is exceeded. Actuation reduces drive power, but not slowed down. This is not enough for fast steering maneuvers. In DE 10 2004 028 053 A1 The risk of tipping is reduced in a vehicle by the inclination of the vehicle body is changed. However, a so-called active chassis is relatively expensive. Such a method is in DE 102005012004 A1 disclosed.

In DE 10 2004 046 890 A1 . DE 10 2005 015 673 A1 . DE 10 2004 035 888 A1 or DE 199 18 597 A1 If a risk of tipping a steering intervention is made. The safety considerations and the technical effort to prevent tilting are expensive.

In EP 1 475 297 A1 A safety function is described which becomes active when the driver has left the vehicle. In DE 199 19 655 A1 is a tilt protection described that evaluates the course of the wheel loads.

also zu Gunsten der rechten Seite der Formel überschritten wird. Auf der linken Seite ist der durch die Gewichtskraft gebildete Term mit der Fahrzeugmasse und der Erdbeschleunigung. Auf der rechten Seite ist der durch die Querbeschleunigung a, durch Schwerpunkthöhe h und durch cos ε auf die Kippkante projizierte Term.In Fig. 5 the conditions are shown in a four-wheel counterbalance truck. The steering axle is pendulum suspended in P. The wheelbase is y and the track b. The center of gravity S is located on the vehicle longitudinal axis at the height h and at a distance y _F from the drive axle. The vehicle speed v is defined as the speed of the drive axle center M. The steered wheels of the rear axle are turned so that the vehicle turns around a point R. It lies at a distance r from the drive axle center point M. In the case of lateral tilting, the stacker initially tilts over a tilting edge, which is formed by a connecting line between front wheel L and pendulum point P. With even stronger cornering formed by the pendulum axle stop another tilting edge, which should be disregarded here. The stacker starts to tilt when the torque about the tilt axis caused by the lateral acceleration a is greater than the torque generated by the weight mg, the steady state $$\mathrm{mgd}=\mathrm{mah\; cos\; \epsilon }$$

So in favor of the right side of the formula is exceeded. On the left side is the term formed by the weight force with the vehicle mass and the gravitational acceleration. On the right side, the term projected by the lateral acceleration a, by the center of gravity height h and by cos ε is projected onto the tilting edge.

$$\mathrm{tan\beta }=\frac{Y_F}{r}$$

$$\mathrm{tan\gamma }=\frac{y}{r}$$

$$d=y_F\mathrm{sin\alpha }$$

$$\rho =\frac{r}{\mathrm{cos\beta }}$$

$$v_s=\frac{\rho }{r}v$$

$$a=\frac{v_s^2}{\rho }$$

$$\epsilon =\beta -\alpha$$

$$\mathit{mgd}=\mathit{mah}\cos \epsilon$$

With the following intermediate sizes, the torque balance can be set up: $$\mathrm{tan\alpha }=\frac{b}{2y}$$

$$\mathrm{tan\beta }=\frac{Y_F}{r}$$

$$\mathrm{tan\gamma }=\frac{y}{r}$$

$$d=y_F\mathrm{sin\; .alpha}$$

$$\rho =\frac{r}{\mathrm{cos\beta }}$$

$$v_s=\frac{\rho }{r}v$$

$$a=\frac{v_s^2}{\rho }$$

$$\epsilon =\beta -\alpha$$

$$\mathit{mgd}=\mathit{mah}\cos \epsilon$$

The known in electric counterbalance trucks tilt prevention, in which the vehicle speed is limited so that at the measured steering angle, the lateral acceleration remains below a predetermined value, is not readily applicable to counterbalanced forklift with an internal combustion engine with a hydrodynamic torque converter. In such vehicles, the driver operates the driving function either via a Bowden cable or an electronic control. It lacks an actuator that limits the power output of the internal combustion engine, so as to limit the driving speed. The torque converter has a freewheeling function, so that no significant braking torque can be applied via the internal combustion engine.

Another problem is the choice of a suitable sensor for determining the permissible driving speed. In regulated electric motor drives, as currently used, a speed sensor is already present. About the gear ratio and the wheel radius of the drive wheel, the driving speed can be determined. In a torque converter, the relationship between engine speed and vehicle speed is heavily load dependent. Older vehicles lack a speed sensor.

The invention has for its object to provide a method and apparatus for tilting prevention of a counterbalance truck with an internal combustion engine, which can be effectively used by simple means.

This object is solved by the features of claims 1, 2 and 10.

In a control device, a characteristic for a tilt prevention is stored as a function of the driving speed from the steering angle. If the above-mentioned last formula is resolved according to the speed v and represented as a function of the steering angle γ, a curve v (γ) is obtained as the tilting limit. This is in Fig. 6 shown in a diagram. The characteristic stored in the control device, which is located below the tipping limit, is naturally below the tipping limit and possibly includes dynamic reserves.

When driving the counterbalance truck, the driving speed and the steering angle are measured or determined and from this the permissible driving speed is determined, namely from the mentioned characteristic. If the measured or determined driving speed or the specific speed exceeds the permissible value, two measures take place. On the one hand, the performance of the internal combustion engine is reduced. This is done by limiting the setpoint and / or by switching a power shift transmission in the neutral position. It is understood that the latter measure can only take place when a power shift transmission is arranged in the drive train. On the other hand, there is a deceleration, wherein the braking force is generated by driving a service brake and / or control of a counter-torque generator in the drive train and / or by switching the reverse gear in a power shift transmission. A counter-torque generator may e.g. be driven by a drive train hydraulic pump, which works on a hydraulic resistance.

An alternative solution of the object according to the invention is to store in a control device, depending on the steering angle, maximum values for the lateral acceleration of the vehicle. While driving, the lateral acceleration is measured. In the control device, the lateral acceleration is compared with the respective maximum value. Exceeds the determined lateral acceleration the maximum value, the same measures are set in motion, as have been explained in connection with claim 1.

The invention provides with simple measures that there is no risk of tipping when cornering counterbalance trucks. It is understood that the method steps prescribed by the method according to the invention are constantly repeated in order to counteract changing driving conditions.

To determine the risk of tipping, the steering angle and the driving speed must be measured. The steering angle may e.g. be measured by means of a steering angle sensor. The driving speed may e.g. be determined by the output speed of the transmission and the diameter of the driven wheels. The measurement of the driving speed is also conceivable via measurement of the engine speed and the engine load. The measure of the torque may e.g. be determined by known methods, such as measurement of the pressure or injection quantity. The driving speed can be estimated via the characteristic curve of the converter. For electronically controlled engines, both information is often available.

To measure the driving speed, the speed of both drive wheels can be measured. From the average and the wheel radius, the driving speed is determined. From the speed ratio of the steering angle can be determined and thus dispense with the steering angle sensor.

It is already mentioned above that the power reduction of the internal combustion engine can be done in different ways. If an electronically controlled combustion engine is available, the setpoint can be reduced via this. If a power shift transmission is set in the neutral position, This also leads to a reduction in performance. If the setpoint generator for the internal combustion engine mechanically works on an actuator of the internal combustion engine, a mechanical limitation can be made, for example, by the traction cable between accelerator pedal and actuator is extended. A comparable possibility results, for example, by an extension of the linkage between accelerator pedal and actuator of the internal combustion engine.

Counterbalance trucks naturally have a service brake. This can be controlled by the control device according to the invention, if there is a risk of tipping. An alternative or additional possibility is a metered connection of the reverse gear in the presence of the power shift transmission in the drive train. Finally, a hydraulic pump may be driven by the drive train, which operates on a controllable hydraulic resistance, such as a controllable throttle to generate a counter-torque, resulting in a deceleration of the drive torque.

In Kippgefährdungsfall the brake means used can generate a preset braking force. It is understood that the braking force can also be chosen differently high depending on the extent of the hazard, i. E. according to the extent of exceeding the permissible driving speed. It is further understood that for this purpose a brake controller can be used, which ensures that the desired braking value is achieved or maintained when driving the braking device.

The risk of tipping is naturally influenced by the load taken and the height of the load on the counterbalance truck. Therefore, in one embodiment of the invention, it is provided to determine the height and the size of the load by means of corresponding sensors and to send a corresponding signal to the control device which thereby modifies the permissible value or the respectively measured speed value.

Fig. 1

zeigt ein Blockschaltbild für eine Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens.

Fig. 2

zeigt eine gegenüber Fig. 1 abgewandelte Einzelheit.

Fig. 3a bis 3c

zeigen verschiedene Möglichkeiten zur Reduzierung der Antriebskraft eines Verbrennungsmotors für das erfindungsgemäße Verfahren.

Fig. 4a und 4b

zeigen verschiedene weitere Möglichkeiten zur Reduzierung der Antriebskraft eines Verbrennungsmotors für das erfindungsgemäße Verfahren.

Fig. 5

zeigt ein Diagramm für das Fahrverhalten eines Gegengewichtsstaplers.

Fig. 6

zeigt ein Kurvendiagramm für die Abhängigkeit der Fahrgeschwindigkeit vom Lenkwinkel im Hinblick auf das Kippverhalten eines Gegengewichtsstaplers.

The invention will be explained in more detail with reference to drawings.

Fig. 1

shows a block diagram of an apparatus for carrying out the method according to the invention.

Fig. 2

shows one opposite Fig. 1 modified detail.

Fig. 3a to 3c

show various ways to reduce the driving force of an internal combustion engine for the inventive method.

Fig. 4a and 4b

show various other ways to reduce the driving force of an internal combustion engine for the inventive method.

Fig. 5

shows a diagram for the driving behavior of a counterbalance truck.

Fig. 6

shows a graph for the dependence of the driving speed of the steering angle with respect to the tilting behavior of a counterbalance truck.

Fig. 1 shows an internal combustion engine 10, such as a diesel or LPG engine, a torque converter 12, a power shift transmission 13 and a drive axle 14 with a differential 16 as the drive train of a counterbalance truck. Wheel brakes 18, 20 belong to front wheels 22, 24 of not shown Counterbalance truck. From this a rear steerable wheel 26 is shown for the steering axle. In the course of the drive shaft 14, a hydraulic pump 28 is arranged, which operates on a controllable hydraulic throttle 30. On the drive axle 14 also sits another brake 32nd

An accelerator pedal 34 acts on a control device 36, which controls the entire drive shown. Indicated at 38 is an actuator for the internal combustion engine 10, e.g. via a linkage or a traction cable (Bowden cable) adjusts the control variables of the internal combustion engine 10 or via an electronic control. The actuator 38 is also connected to the control device 36. A steering angle sensor 40 measures the steering angle of the steered wheel and provides a signal to the controller as well as a speed sensor 42 at the output of the engine 10, a speed sensor 44 on the output axle of the transmission 13, and speed sensors 46, 48 on the drive axle.

The counterbalance truck, not shown, naturally has a height-adjustable load-carrying device, which at 50 in Fig. 1 is shown. He is assigned a load sensor 52. For Hubhöhenmessung another sensor 54 is provided. The sensors 52, 54 are also connected to the central control device 36.

In the central control device 36, a characteristic is stored, which in Fig. 6 is specified with "characteristic with dynamic reserves". It is located below the curve for the tilt limit during stationary cornering of the counterbalance truck. The tilting limit results from the calculations made above and it is understood that the driving condition must be chosen so that the tilting limit is not reached to prevent tilting.

With the help of the individual sensors, it is possible to determine the driving speed of the vehicle at any time. It is understood that not all speed sensors 42, 44, 46 or 48 are required. Via the drive axle 14, the speed can be determined when the radius of the driven wheels 22, 24 is known. The wheels may alternatively be assigned a respective speed sensor 46, 48. For this purpose, it is necessary to determine the speed values if the vehicle speed is to be determined during cornering. The driving speed is usually set by the pedal 34, and the actuator 38 adjusts the engine 10 so that the requirement of the setpoint generator is met. Now occurs at a measured steering angle via steering angle sensor 40 and a measured driving speed on a critical value, i. a value above the "dynamic reserve characteristic", appropriate countermeasures must be taken. One is that the controller 36 modifies the setpoint and applies a reduced setpoint to the actuator 38. Alternatively and additionally, the power shift transmission 13 is switched to neutral position, also via the control device 36.

As a further measure, a braking process is initiated. A braking option is to control the service brakes 18, 20 and 32 accordingly. Another possibility, additionally or alternatively, is to control the reverse gear in the manual transmission via the control device 36 in part. Finally, with the aid of the hydraulic pump 28, which acts on the hydraulic throttle 30, a counter-torque can be generated on the drive axle 14, this counter-torque being adjustable in height via the control device 36.

Since the driving condition depends strongly on the amount of a load taken, the signals of the sensors 52, 54 in the control device 36 at the Determination of the permissible speed for the internal combustion engine or the calculation of the permissible speed considered accordingly.

In Fig. 2 an alternative solution with regard to the control of the control device 36 is shown. Their interconnection with regard to the components of the counterbalanced truck Fig. 1 resembles the Fig. 1 , In Fig. 2 However, a lateral accelerometer 56 is provided and in the control device 36 a steering angle dependent maximum values for the lateral acceleration are stored, which should not be exceeded during cornering. If this is the case, the measures will be taken individually or in combination, as in connection with Fig. 1 have been explained. Is also in the context of the invention to specify a fixed maximum lateral acceleration. As a result, a steering angle sensor can be omitted.

In Fig. 3 the three possibilities of modifying the speed setpoint of the internal combustion engine 10 are shown side by side. In Fig. 3a the same drive of the actuator 38 is shown as in FIG Fig. 1 , In Fig. 3b a separate engine control unit 60 is provided, which acts on the actuator 38 and to which the signal of the speed sensor 42 is given. The central control device 36b outputs in accordance with the measured values and the characteristic as described in connection with FIG Fig. 1 has been explained, the modified setpoint for the internal combustion engine 10, and the controller 16 downshifts the speed to the desired value.

In the embodiment according to Fig. 3c the pedal 34 acts directly on the engine control unit 60a, wherein in the control device 36c, in turn, the setpoint value for the internal combustion engine 10 is given modified to the control unit 60a in order to change the value predetermined by the pedal 34.

According to FIGS. 4a and 4b there is a mechanical connection between the accelerator pedal 34 and the actuator on the internal combustion engine 10. In Fig. 4a is a drawbar or Zugseilverbindung 62 indicated, which is variable by action on the control device 36 at 64 in length. If the setpoint, which is predetermined by the pedal 34, to be reduced, this is done by an extension of the drive connection, whereby the internal combustion engine 10 is set to a low speed.

In the execution after Fig. 4b an adjusting cylinder 66 is connected to a hydraulic line 68, the hydraulic pump 28 after Fig. 1 with the hydraulic throttle 30 connects. The throttle is controlled via the control device 36d. This happens at a required speed reduction to avoid tilting. As a result, a spring connection 70 is changed between a rod 72 connected to the pedal 34 and a rod 74 connected to the actuator of the internal combustion engine 10. The change results in accordance with the pressure in the line 68, which in turn is dependent on the setting of the throttle 30th

Claims (20)

1. Method for preventing a counterweight forklift tipping over, the counterweight forklift comprising a front drive axle with two driven wheels and a rear steering axle with at least one steered wheel, wherein the drive train comprises a combustion engine and a torque converter, wherein further, when the vehicle is travelling, travel speed and steering angle are measured and, in a control device, an admissible travel speed is assigned to each steering angle, and the control device reduces the travel speed of the counterweight forklift if the admissible travel speed is exceeded, characterised by means of the additional method steps:

   - in the control device a characteristic for preventing tipping over is saved as a function of the travel speed of the steering angle, the characteristic lying below the tipping over limit and containing dynamic reserves,

   - the admissible rotation speed of the combustion engine is determined from the admissible travel speed,

   - if the travel speed exceeds the admissible travel speed, the power of the combustion engine is reduced by

   - applying a brake to the combustion engine and/or

   - limiting the set value for the combustion engine and/or

   - by switching a power-shift gearbox into the neutral position,

   - and at the same time a braking force is generated by

   - activating an operating brake and/or

   - activating a counter-torque generator in the drive train

   and/or

   - engaging the reverse gear in a power-shift gearbox.
2. Method for preventing a counterweight forklift tipping over, the counterweight forklift comprising a front drive axle and two driven wheels and a rear steering axle with at least one steered wheel, the drive train comprising a combustion engine and a torque converter, with the following method steps:

   - steering angle-dependent maximum values for the lateral acceleration of the vehicle are saved in a control device,

   - the lateral acceleration is measured while the vehicle is travelling,

   - in the control device, the measured lateral acceleration is compared to the maximum value,

   - if the measured lateral acceleration exceeds the maximum value, the power of the combustion engine is reduced, by

   - applying a brake to the combustion engine and/or

   - limiting the set value for the combustion engine and/or

   - switching a power-shift gearbox into the neutral position,

   and at the same time a braking force is generated, by

   - activating a service brake and/or

   - activating a counter-torque generator in the drive train

   and/or

   - engaging the reverse gear in a power-shift gearbox.
3. Method according to claim 1 or 2, characterised in that the travel speed is determined by the output speed and the radius of the wheels of the front axle.
4. Method according to claim 1 or 2, characterised in that the engine speed and the load on the engine are measured and the travel speed is estimated via the characteristic of the torque converter.
5. Method according to claim 1 or 2, characterised in that the speed of both drive wheels is measured and the travel speed is determined from the mean value and the radius of the driven wheels.
6. Method according to claim 1 or 2, characterised in that the lateral acceleration and the steering angle are measured and the travel speed is determined therefrom.
7. Method according to one of claims 1 to 6, characterised in that the lifting height of a load-bearing means of the counterweight forklift and/or the weight of a load on the load-bearing means are/is measured and the measured travel speed or lateral acceleration is modified in accordance with the values for the lifting height and/or load.
8. Method according to one of claims 1 to 7, characterised in that a set braking force is dependent on the deviation of a measured travel speed from the admissible travel speed.
9. Method according to one of claims 1 to 8, characterised in that the applied braking force is regulated, wherein the braking force when the vehicle is moving backwards is lower than the braking force when the vehicle is moving forwards.
10. Device for preventing a counterweight forklift tipping over comprising a front drive axle and two driven wheels and a rear steering axle with at least one steered wheel, , wherein the drive train comprises a combustion engine and a torque converter, with the following characteristics:

    - a control device (36, 36a, 36b, 36c, 36d), in which a characteristic for preventing tipping over is saved as a function of the travel speed of the steering angle, the characteristic lying below the tipping over limit and containing dynamic reserves,

    - a device for determining the travel speed

    - a device for determining the steering angle

    - a device for determining the admissible travel speed and/or the engine speed of the combustion engine

    - a comparing device which compares the determined travel speed and/or the speed with the respective admissible travel speed and/or the admissible speed

    - a set value transmitter, controllable by the control device, for the combustion engine

    - an actuator, controlled by the control device, for setting the engine speed of the combustion engine and

    - a braking device, controlled by the control device, for the drive train.
11. Device according to claim 10, characterised in that a rotation speed sensor (42) is assigned to the combustion engine (10).
12. Device according to claim 10 or 11, characterised in that a power-shift gearbox (13), switchable by the control device (36), is subordinate to the torque converter (12).
13. Device according to claim 12, characterised in that a rotation speed sensor (44) is assigned to the output of the power-shift gearbox (13).
14. Device according to one of claims 10 to 13, characterised in that, in the drive train, on the drive side or the output side of the torque converter, a hydraulic pump (28) is arranged, which acts on a controllable throttle (30), and the controllable throttle (30) is controlled by the control device (36).
15. Device according to one of claims 10 to 14, characterised in that a steering angle sensor (40) is assigned to the steered wheel (26).
16. Device according to one of claims 10 to 15, characterised in that a lifting height sensor (54) and/or a load sensor (52), which is connected to the control device (36), is assigned to a load bearing means (50) of the forklift.
17. Device according to one of claims 10 to 16, characterised in that the set value transmitter comprises an operating element (34) that acts on an actuator of the combustion engine (10) via a controllable transmitter gearbox and the controllable transmitter gearbox is connected to the control device (36d).
18. Device according to claim 17, characterised in that the transmitter gearbox comprises a lengthways extendable pulling rod or a lengthways extendable pulling cable (62).
19. Device according to one of claims 14 to 18, characterised in that the transmitter gearbox is controlled by the pressure of the hydraulic pump (28).
20. Device according to any of claims 10 to 16, characterised in that, an operating element (34) is provided for the set value transmitter and an electronic set value transmitter (38) is provided, which is connected to the control device (36, 36b,36c).

Images