The present invention relates to a method and a device for controlling movements movements of a work vehicle comprising an equipment assembly for handling objects or material.
The term work vehicle comprises different types of construction machines, such as a wheel loader, a backhoe loader and an excavator. The invention will be described below in a case in which it is applied in a wheel loader. This is to be regarded only as an example of a preferred application.
The wheel loader can be utilized for a number of different areas of activity, such as lifting and transporting stone and gravel, pallets and logs. For some of these activities, use is made of different implements, such as a bucket, a fork and gripping arms. Besides an implement, the equipment assembly also comprises a load-arm unit and one or more working cylinder(s) for operating/moving the implement in question.
When the wheel loader is used for loading material on a loading vehicle such as a dumper or a truck, the implement carrying the material is raised to a high vertical position and the wheel loader is brought nearer to the loading vehicle. Due to the large weight of the material, the movement of the wheel loader is sensitive, which requires great driver skills, and often leads to jerks and swings. It is known to use different so-called gear shifting modes according to a specific gear shifting strategy in wheel loaders with an automatic gear box. Shifting to a higher gear takes place at different minimum engine speeds in two different gear shifting modes. Further, shifting to a lower gear takes place at different minimum vehicle speed in two different gear shifting modes. The gear shifting modes are selected manually by a driver by operating a handle, a so-called APS-handle.
Further, it is known, for example from EP 0715102, to control gear shifting modes of an automatic vehicle transmission based on parameter signals representing specific operation conditions, such as road conditions. Especially, the parameter signal represents the inclination of the road, on which the vehicle is moving.
WO 03/89723 relates to a device for controlling a work vehicle. The control device comprises actuation means, which is manually operated by the driver, for selecting different operating states. Such operating states may be defined by specific activities where different implements, like a bucket or pallet forks are used. Said actuation means is coupled to a central unit. The central unit is coupled to the hydraulic system for moving the implement and the movement of the implement is controlled depending on the selected operating state. The central unit is also coupled to the engine and/or the transmission for controlling the speed of the engine and/or selecting a gear point for the transmission depending on the selected operating state, The control device also comprises means for detection of the position of the implement. The detection means is also coupled to the central unit and the speed of movement of the implement may be limited depending on the detected position of the implement.
One object of the invention is to achieve a method for controlling the movements of a work vehicle, which creates softer movements and a more simple operation, especially during loading. This object is achieved in that a state of said equipment assembly is determined and that at least one operating parameter of a driveline of the vehicle is controlled depending on the determined equipment assembly state. Preferably, the position of the equipment assembly is determined. By determining the vertical position of the equipment assembly and for a high vertical position changing gears in the gear box so that the driver can depress a gas pedal more for a certain vehicle speed/movement, the movements of the work vehicle may be softened and the operation of the vehicle facilitated and made more efficient.
According to one embodiment, the position of the equipment assembly is determined by a lift angle and/or a tilt angle of an implement in the equipment assembly. This may be achieved by sensing the extension of a hydraulic lift and/or tilt cylinder in the equipment assembly and/or by sensing the angular relationship in an articulation point in a load-arm unit.
According to another embodiment, at least two different equipment assembly position regions are predefined. By dividing the movement pattern of the implement in different regions, the operating parameter of the driveline may be controlled accurately. Especially, at least two different equipment assembly position regions are predefined for each of the lift angle and the tilt angle of the implement. Specific combinations of a lift angle region and a tilt angle region may therefore be used for controlling the operating parameter of the driveline.
Another object of the invention is to achieve a device for controlling the movements of a work vehicle, which creates softer movements and a more simple operation, especially during loading. This object is achieved in that the device comprises means for determining a state of said equipment assembly and a control unit for controlling at least one operating parameter of the driveline depending on the determined equipment assembly state.
Additional embodiments of the invention will be described in the following specification and the accompanying illustrative drawings.
The invention sill be explained below, with reference to the embodiments shown in the accompanying drawings, wherein:
The wheel loader 1 comprises an equipment assembly 11 for handling objects or material. The equipment assembly 11 comprises a load-arm unit 6 and an implement 7 in the form of a bucket fitted on the load-arm unit. The load-arm unit 6 can be raised and lowered relative to the front section 2 of the vehicle by means of two second hydraulic components in the form of two hydraulic cylinders 8,9, each of which is connected at one end to the front vehicle section 2 and at the other end to the load-arm unit 6. The bucket 7 can be tilted relative to the load-arm unit 6 by means of a third hydraulic component in the form of a hydraulic cylinder 10, which is connected at one end to the front vehicle section 2 and at the other end to the bucket 7 via a link-arm system.
More specifically, said means 27,28 are arranged for determining a position of the equipment assembly 11 and are preferably formed by sensors. Said means 27,28 are arranged for detection of the position of the equipment assembly in a vertical direction. Said sensors 27,28 are arranged for sensing the lift angle and the tilt angle, respectively, of the implement 7. The lift angle is defined in a vertical direction and determined by the extent of projection of the second hydraulic cylinders 8,9. The tilt angle is determined by the extent of projection of the third hydraulic cylinder 10. Said sensors 27,28 are formed by angular sensors for sensing the angular position at an articulation point. Each of said sensors 27,28 may alternatively be formed by linear sensors, sensing the extent of projection of the hydraulic cylinder in question.
The control device 25 comprises a second control unit 29 (see
The engine speed is detected via an engine speed sensor 30. The sensor 30 is electrically connected to the first control unit 26.
The vehicle's speed is detected by a sensor 32 in a conventional way, for example by measurement of the speed of rotation of a shaft inside the gearbox 15.
The control device 25 comprises means 34 for controlling the torque converter 16. Said converter control means 34 is electrically connected to the control unit 26 and is controlled by the same. Said converter control means 34 is here arranged for controlling lock-up of the torque converter 16.
The control device 25 comprises a plurality of means 35 for controlling transmission shifting points in the gearbox 15. Said transmission control means 35 are electrically connected to the control unit 26 and are controlled by the same.
The control device 25 is arranged to shift gears according to a plurality of predefined gear modes. Shifting to a higher gear takes place at different minimum engine speeds in two different gear shifting modes. Further, shifting to a lower gear takes place at different minimum vehicle speed in two different gear shifting modes. One parameter for selecting the gear shifting mode is the above-mentioned determined equipment assembly state. There may also be other parameters that influence the selection of gear shifting mode.
Further, a plurality of operating levers 22 are arranged in the wheel loader cab for being maneuvered by the driver and electrically connected to the control unit 26 for controlling movements of the wheel loader 1 (and the equipment assembly 11). The signals from the operating levers 22 are converted in a characteristic way in the control unit 26 depending on the position signals from the position sensors 27,28 and are then sent as output signals to the respective driveline component in question.
The inventive method for controlling the movements of the wheel loader will below be described according to a first embodiment in connection with
In
A state of the equipment assembly 11 is defined by the lift angle and the tilt angle. More specifically, three position regions are defined for the lift angle, α; “Bucket down”:α<−30°, “Bucket inbetween”:−30°<α<30° and “Bucket raised”:α>30°. Three position regions are also defined for the tilt angle, β; “Bucket forwards”:β<−30°; “Bucket neutral”:−30°<β<30° and “Bucket backwards”:β>30°. These three position regions for the lift angle and the tilt angle, respectively, give 3*3=9 equipment assembly states.
Each of said nine equipment assembly states corresponds to a specific gear mode. Each gear mode comprises predefined transmission shifting points adapted for an optimum operation. Below follows three examples of gear modes.
A first curve 36, or line, in the diagram, defines the engine speed limit for shifting from gear number two to gear number one in a first gear mode. The gear shifting line is different for different gear modes, which is indicated by an arrow 50. A second curve 38, or line, in the diagram defines the engine speed limit for shifting from gear number two to gear number one in a second gear mode. The first and second curve 36,38 are here defined by straight lines at different engine speeds.
A third curve 37, or line, in the diagram, defines the vehicle velocity limit for engaging lock-up in the converter 16 in a third gear mode. The converter lock-up line is different for different gear modes, which is indicated by an arrow 51. A fourth curve 39, or line, in the diagram defines the vehicle velocity limit for engaging lock-up in the converter 16 in a fourth gear mode. The third and fourth curve 37,39 are here defined by straight lines at different vehicle velocities. A vehicle state is below defined by the parameters engine speed and vehicle velocity.
As a first example, the detected equipment assembly state is: lift angle; “Bucket down”, and tilt angle; “Bucket neutral”. This equipment assembly state is linked to the first curve 36 in the diagram (defining the engine speed limit for shifting from gear number two to gear number one). Further, this equipment assembly state is also linked to the third curve 37 in the diagram (defining the vehicle velocity limit for engaging lock-up in the converter 16).
As a second example, the detected equipment assembly state is: lift angle; “Bucket raised”, and tilt angle; “Bucket forwards”. For this equipment assembly state, shifting down to gear number one is prohibited and lock-up in the converter is also prohibited.
As a third example, the detected equipment assembly state is: lift angle; “Bucket down”, and tilt angle; “Bucket backwards”. This equipment assembly state is linked to the second curve 38 in the diagram (defining the engine speed limit for shifting from gear number two to gear number one). Further, this equipment assembly state is also linked to the fourth curve 39 in the diagram (defining the vehicle velocity limit for engaging lock-up in the converter 16).
As an alternative to the bucket, the above-described method is also applicable when the wheel loader is equipped with pallet forks.
The above-described method may also be used for equipment assembly with more degrees of freedom.
In
In
The invention is also directed to a computer program comprising code means for performing all the method steps described above when said program is run on a computer. Said computer program is loaded in a memory in the control unit. Said computer program may be sent to the control unit by wireless technique, for example via the internet.
The invention is further directed to a computer program product comprising program code means stored on a computer readable medium for performing the method described above when said program product is run on a computer. Said computer readable medium may be in the form of a floppy disk or a CD-ROM.
The abovementioned control unit (ECU) 26 is also often called a CPU (Control Power Unit) or plainly vehicle computer.
The invention is not in any way limited to the above described embodiments, instead a number of alternatives and modifications are possible without departing from the scope of the following claims.
For example, the gearbox design shown in
Further, said gear mode may comprise controlling the speed of the engine.
In addition, the two control units 26,29 can be integrated into a single control unit.
As an alternative, or complement, to controlling transmission shifting points and lock-up in the converter, said control unit may be arranged to set a torque curve in the engine.
As an alternative, or complement, to the vertical position, said equipment assembly state may comprise the speed of movement of the equipment assembly.
The invention may also be applied for a fork-lift truck for handling pallets in an industry.
The present application is a continuation patent application of International Application No. PCT/SE2004/001151 filed 27 Jul. 2004 which was published in English pursuant to Article 21(2) of the Patent Cooperation Treaty; said application is expressly incorporated herein by reference in its entirety.
Number | Date | Country | |
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Parent | PCT/SE04/01151 | Jul 2004 | US |
Child | 11627953 | Jan 2007 | US |