DE10232639A1 - Load transport vehicle, especially forklift trucks - Google Patents

Abstract

The invention relates to a load transport vehicle (1), in particular a forklift truck with a chassis (2), which has at least two wheel axles (3, 4), with brakes (5) for the wheels (6, 7) and at least one wheel axle (3 or 4) and with a drive train (8) which has at least one motor (9), at least one transmission (10) and at least one clutch (11) for connecting the motor (9) and transmission (10), a control device (12) is provided for the drive train (8), which is coupled to a determination device (13) for detecting the angle of inclination (alpha) of the vehicle (1) and for detecting the degree of acceleration or deceleration of the vehicle (1).

Description

The invention relates to a load transport vehicle, in particular a forklift, according to the preamble of the claim 1.

In one of the preamble of claim 1 corresponding load transport vehicle can, for example, a so-called Power shift gear can be provided. A power shift gearbox one has a mechanical gear arrangement by a hydraulic Torque converter is driven, the gear changes without Torque interruption enabled. The switching operations are by opening a clutch and closing one another clutch causes what a gear wheel from the gear shaft separates and connects another gear wheel to the shaft. The Clutches have a stack of alternately arranged friction plates and steel plates. A piston under hydraulic pressure presses these plates together to connect the gearbox with the Shaft and a spring presses the non-pressurized Piston back, around the gear wheels and separate the gear shaft from each other.

With such an arrangement the brake system is operated hydraulically and has an arrangement, which makes electro-proportional pressure control possible. The engine will controlled with the help of a CAN controller or it becomes a servo motor used that interacts with the fuel pump.

A central control device for the drive train monitors the accelerator pedal (accelerator pedal) to the driver's driving intentions to investigate. The degree of pedal actuation is a measure of the desired vehicle speed. The Level of change the pedal actuation shows the desired acceleration or braking the vehicle.

The control device continuously tries that desired Speed measure by Adjust the torque delivered by the motor, a suitable pressure on the brakes of the transmission for one given translation range is created. If the speed is too low, the speed is reduced Control device the brake pressure and increases the engine torque, and, if the speed is too high, the procedure is reversed.

Entering the operating mode enables this Driver, the acceleration or braking effect of the system adapt to the respective driving condition.

Usually in parallel with this speed control algorithm is an automatic switching algorithm to achieve a suitable selection of the gear ratio carried out.

To further increase driving comfort, Operational controls (e.g. control of the forks of a forklift) carried out for monitoring. This Information is used to automatically change the engine, transmission and adjust braking parameters when additional engine power for vehicle hydraulics is required.

A considerable technical problem this system is caused by the fact that the previously explained Vehicle types often be operated on inclined roads. Compared to the operation change on a level road the powers for starting and stopping on inclined roads considerably and To make matters worse, these forces are very difficult to predict are since they are in large Dimensions from Depending on the inclination angle of the road.

Previous attempts to address these issues to overcome, either suffer from the disadvantage of undesired rolling back of the vehicle or starting at too high an engine speed, which in turn means that driving comfort (especially with regard to increased noise) suffers and using too much fuel.

If the control device does not Has travel direction sensor, it is also possible that rolling back is not even recognized, resulting in uncontrollable, accident-prone Operating modes can.

There are also further complications permanent Variations in vehicle weight due to loading and unloading of the vehicle. These variations make it difficult, even on the level Roadway a stable To achieve driving behavior.

In a nutshell, this means that conventional vehicles, especially when starting off on an incline Do not roll back the road, especially for safety reasons allowed to. On the other hand, the vehicle should not accelerate too quickly, otherwise the starting behavior will be too aggressive. At the downhill directional start-up there is also the problem that it too accelerating too strongly, which is also not for safety reasons is acceptable.

It is therefore conventional Vehicles mainly The driver's job, these shortcomings balance and both the brakes and the engine power to control accordingly. Here, of course, result from never entirely impossible human misconduct problems as a correct one to be carried out by the driver Control mainly depends on the load of the vehicle and the slope of the road, which is usually not known.

It is therefore the task of the present Invention, a load transport vehicle in the preamble of the claim 1 specified type, its driving behavior in particular is easy to optimize on inclined roads.

This task is solved by the features of claim 1.

In that the control device of the vehicle according to the invention is provided with a determination device that both the detection the degree of inclination of the vehicle or the road and the detection of the acceleration or deceleration rate or value possible the gravitational force acting on the vehicle from the control device using the formula F = sin (α) ⋅ mg relative exactly estimated become. Represented in this formula m the sum of the mass of the vehicle and the load, g the acceleration due to gravity and α the angle of inclination the roadway.

After determining the force F and under consideration of rolling resistance, it is possible in the vehicle according to the invention, exactly to determine the force required to start uphill and downhill is required.

This is usually the case when starting off in downhill direction sufficient to reduce the braking force. At the The control device, on the other hand, must start uphill the measure of increase engine torque while gently and evenly Release the brakes.

It is possible to use the force F in the control device as a dynamic offset for to use the PID algorithms, resulting in a quick and accurate Responsiveness without the need for excessive corrections.

It is thus possible to use the vehicle according to the invention in both directions (uphill and downhill) to predictable and starting in a well-controlled manner, especially without that there is a risk of rolling back or excessive acceleration occurs.

Because of this arrangement it is with the vehicle according to the invention in principle possible, optimal speed and driving behavior control only by using the accelerator pedal.

So it would be possible to only use this a pedal to control both acceleration and braking, the brake pedal then only (or at least predominantly) the Take over the function of an emergency brake could.

The subclaims have advantageous developments the content of the invention.

With the vehicle according to the invention it is advantageously possible by measuring the vehicle inclination to calculate the holding force that is required is to stop the vehicle even on an inclined road to keep.

Using this calculated Holding force, the control device can preferably dynamically Adjust the braking force to the current situation, whereby it possible is an adequate one Braking performance independent from the slope of the roadway. This gives the advantage that not just the transition is optimized in the standstill, but also a considerable one advantage over conventional systems is achievable because of a predictable braking behavior is achievable. Furthermore, it is with the vehicle according to the invention and the control device according to the invention possible that Disadvantages in the control characteristic occurring with previous systems to fix, which are in particular that attitudes to the uphill directional start-up generally differ markedly from those for Starting off is on a level road or downhill road.

If no information about that Lane inclination was only one in previous systems compromise-based regulation possible, which, however, is only a relatively moderate compensation between comfort and safety.

In contrast, it is with the vehicle according to the invention possible, with these conflicting conditions of different driving situations to be finished without sacrificing high security and comfort.

The control device thus determines when driving information about the inclination of the road from the signals from the determination device, being usually uses a combination of analog and digital filtering becomes.

The measured inclination is preferably direct used to interpolate separate PID control parameters to control the brake and the motor. The PID controller for the brake and the engine are dynamically determined with these on a real time basis Values updated.

This approach is seamless Integration of optimized control parameters for all driving situations. For the This gives the driver the advantage of a control behavior without the receipt of the previously explained Compromises of conventional systems.

In known control systems a PID control algorithm is used for the vehicle speed, who tries to base the difference between a target and an actual speed to correct the speed to adjust engine and brake settings. PID control strategies are preferred according to the invention, however can also other control methods and devices and thus other control strategies are used.

With the system according to the invention it is opposite possible, an improvement in the dynamic behavior of a driving control system to get a parent PID controller is used, e.g. the desired acceleration with the actual Acceleration compares and corrects the output of a first PID controller.

Such a configuration has the advantage that the cruise control is considerably less ger sensitive to changes in vehicle mass (or vehicle load) and the inclination of the road.

Furthermore, the vehicle according to the invention and the control device according to the invention compared below explained Problems of the prior art have significant advantages on:

Usually the acceleration is based on a first derivative of a Wheel speed signals are calculated and then a second PID controller fed.

In cases where the wheel speed is not can be determined directly, but from the output speed of the Gear must be determined, it is difficult to be reliable Obtain acceleration values because of the rotations of the drive shafts represent a significant noise factor, so that the desired improved Control strategy is more or less unattainable.

If on the other hand the wheel speed is measured directly, this is usually especially with regard to size restrictions only possible with limited accuracy, which in turn makes the applicability of this control strategy difficult.

It further exacerbates the situation makes it difficult for wheel slip to occur in some driving conditions, what the acceleration value completely can be incorrect. Such a common one The condition that occurs is the forward or backward approach of a vehicle empty forklift truck with the weight on the drive axle is low.

In contrast, it is with the control strategy according to the invention possible, that the controller provides dynamic acceleration information when driving received from the determination device, preferably a digital bandpass filter is used. This value becomes direct with the desired one Acceleration value compared, resulting in improved speed control without leads to the disadvantages mentioned above.

If the acceleration signal from a wheel speed signal is derived, and this acceleration signal is compared with the acceleration signal of the determination device, Is it possible, to determine the wheel slip.

This information can be used for this the driving characteristics and safety by limiting the Acceleration or deceleration, which is fed to the second PID controller, improve what is the response to varying road conditions (such as snow, ice, rain, dirt, etc.).

In claim 9 is a method according to the invention Are defined.

In claim 10, a control according to the invention or control device as an independently tradable object accordingly defined the principles of the invention.

More details, features and Advantages of the invention result from the following description of an embodiment based on the drawing. It shows:

1 a representation of a possible embodiment of a vehicle according to the invention on an inclined roadway, and

2 a block diagram of the essential drive and control components of the vehicle according to 1 ,

In 1 is an example of a load transport vehicle 1 shown in the form of a forklift. In principle, however, the invention is not limited to forklifts, but rather can be used in practically any type of load transport vehicle, such as front loaders and the like.

The vehicle 1 has a usual chassis in the example 2 on the two wheel axles in the illustrated embodiment 3 and 4 having.

The wheel axles have pairs of wheels 6 and 7 on, each with in 1 Brakes not shown are shown, but in 2 through the block 5 are symbolized.

In 2 is a powertrain 8th of the vehicle 1 shown. The drivetrain 8th has an engine in the example 9 on the clutch shown only schematically very simplified 11 with a gear 10 is coupled. About the transmission 10 the drive axle is driven with the assigned brakes, which in 2 through the block already mentioned 5 is symbolized.

Furthermore, in 2 a block 12 shown, the control device for the drive train 8th represents.

The block 12 is with a determination device 13 for the detection of the inclination angle α of the vehicle (see 1 ) and to record an acceleration or deceleration rate of the vehicle 1 coupled.

Furthermore, in 2 through the block 14 symbolizes a driver interface. This interface gives data to the control device 2 , such as setpoints for speed ranges or driving directions, operating modes, operating control behavior, as well as the positions of the accelerator pedal and the brake pedal.

The destination facility 13 delivers values about the road inclination and the acceleration and braking status of the vehicle to the control device 12 , The control device also receives 12 Information about the engine speed and gives to the engine 9 Signals to control the engine torque.

The control device gives 12 to the transmission 10 Signals for the clutch pressure from the respective gear stages of the transmission, which is usually designed as an automatic transmission 10 to control and regulate.

Furthermore, the control device 12 Brake pressure signals to the block 5 from the interface 14 optional signals for an emergency brake can get pressure.

In addition to the previously explained According to the invention, it is also possible for measurement signals to determine the output speed on the transmission side of the transmission and the converter speed. The output speed of the gearbox can be recorded with a sensor that makes it possible to detect the drive direction. This means that these measurement signals can also be used the control strategy according to the invention considered become.

Claims (10)

Load transport vehicle ( 1 ), especially forklift trucks, - with a chassis ( 2 ) that has at least two wheel axles ( 3 . 4 ) having; - with brakes ( 5 ) for the bikes ( 6 . 7 ) at least one wheel axle ( 3 respectively. 4 ); and - with a drive train ( 8th ) that has at least one motor ( 9 ), at least one gear ( 10 ) and at least one clutch ( 11 ) to connect motor ( 9 ) and gear ( 10 ), characterized in that - a control device ( 12 ) for the drive train ( 8th ) is provided, which with a determination device ( 13 ) for detecting the angle of inclination (α) of the vehicle ( 1 ) and to record the acceleration or deceleration rate of the vehicle ( 1 ) is coupled. Vehicle according to claim 1, characterized in that the control device ( 12 ) on the basis of the determination device ( 13 ) data supplied and the estimated vehicle mass (m) the holding force calculated to the vehicle ( 1 ) to stand still on an inclined surface. Vehicle according to claim 2, characterized in that the control device ( 12 ) regulates the braking force dynamically depending on the driving condition and the vehicle position, in particular the vehicle inclination. Vehicle according to one of claims 1 to 3, characterized in that the control device ( 12 ) the detected angle of inclination (α) is used for the interpolation of separate control parameters, preferably PID control parameters, for brake and / or motor control. Vehicle according to claim 4, characterized in that the control device ( 12 ) the control parameters, preferably PID parameters, are updated dynamically with real-time values. Vehicle according to one of claims 1 to 5, characterized in that the control device ( 12 ) has a first and a second, preferably designed as a PID controller, the second controller, the target acceleration with the actual acceleration of the vehicle ( 1 ) compares and corrects the output values of the first controller according to the comparison result. Vehicle according to one of claims 1 to 6, characterized in that the control device ( 12 ) is in operative connection with a wheel speed sensor device. Vehicle according to claim 7, characterized in that the control device ( 12 ) determines the wheel slip on the basis of the signals from the wheel speed sensor device. Method for controlling or regulating load transport vehicles according to at least one of the features of claims 1 to 8, characterized in that the degree of inclination (α) of the vehicle ( 1 ) and the acceleration or Braking rate of the vehicle ( 1 ) is determined, and that on the basis of this data, both the engine control and the transmission control and the control of the brake pressure are carried out. Control device ( 12 ) for a load transport vehicle ( 1 ), in particular a forklift, according to the preamble of claim 1, characterized by at least one of the characterizing features of claims 1 to 8.