SE534530C2 - Speed control of an engine and power transmission - Google Patents

Abstract

To control the hydrostatic transmission (7) of a cross country machine, for agriculture or forestry, during slow driving the motor speed is limited and is proportional to the speed command from the driver but slower than the normal driving speed. The diesel motor (1) drives a pump (8) for a hydraulic motor (9) connected to the wheels (13) through a gearbox (10) and differential axle (12).

Description

534 530 2 side in inaccessible terrain presupposes a different control of the propulsion transmission.

Figure 2 shows the function of steering in a normal situation, in which the rotational speed 21 of the diesel engine (the vertical axis, unit rpm) is linearly dependent on the steering value (ref), ie. pedal position. The horizontal axis represents the position of the pedal between a free position and a maximum position, ie. the maximum movement. The horizontal axis thus represents the value of the control value specified by the driver, which is in the fi clock scaled between 0 and 1. In the same fi clock the driving speed 22 of the work machine has also been marked (the vertical axis, unit rpm), which in this case has been produced by the rotational speed of the motor 7 for the propulsion transmission. The motor has a speed maximum 24 and the work machine a driving speed maximum 23.

The drive mode of the diesel engine affects the fuel economy of the work machine and the noise level experienced by the driver in a tangible way. In work machines, there is typically a creep gear (so-called inching function) to limit the work machine's maximum driving speed. The gear is necessary, for example, when advancing in difficult terrain, where driving is slower and more precise, whereby a change in the position of the pedal does not mean a major change in driving speed. The gear unit does not really affect the function of the rotational speed of the diesel engine but only the function of the hydrostatic propulsion transmission, since the stroke volume of the pump for the propulsion transmission is considerably limited when this gear is in use. The reduced volume of the motor controls the working machine to slow motion. The maximum position of the pedal means a lower driving speed, but the revving speed of the diesel engine is at its maximum (2200 rpm). Figure 4 shows the function of said gear, whereby it can be stated that the curve over the driving speed (engine speed) has dropped remarkably and is now from approx. 0 to max 400 rpm. The maximum driving speed 43 has decreased but the maximum rotational speed 44 has not changed.

According to the prior art, the creep gear in the control system of the work machine is a state which can be selected by the user and with which a either fixed or adjustable parameter is associated. In the example of fi gur4, the parameter is adjustable and the value is, for example, 10% (or 0.1) so that the maximum driving speed 43 in the state of slow driving is about one tenth of the maximum speed 23 during normal driving . With the adjustability, you can determine olika your different gears for the drive transmission for driving at lower and higher speeds between 0 and 100%. For normal driving, a control or a relationship between the control value and the speed has been determined in the control system. The control system asks the diesel engine for the required speed through the control unit. In the control system, a maximum and a minimum have been determined for the rotational speed in use. The torque curves are selected automatically using an ECU unit, but the maximum speed is affected by the parameter. During normal driving, the maximum position of the pedal (the maximum control value) is typically corresponded to a certain maximum value for the travel speed and the rev speed.

A problem with slow driving, however, is that the use of the crawler gear is continued when moving to terrain or a road that is clearly easily accessible and where the driving speed could be increased. The situation nevertheless leads to depression of the pedal to its maximum position and at the same time a considerable increase in the rotational speed of the diesel engine. However, an increase in the rotational speed is not necessary, as the power requirement has not increased.

The result is that with the high rotational speed, the fuel economy of the work machine becomes worse and the noise level rises.

Summary of the invention The purpose of the invention is to eliminate the problems described above, to improve the fuel economy of the work machine and to reduce unnecessary noise and at the same time also vibration to which the driver is exposed.

With the invention, it is possible to avoid the large rotational speeds of the diesel engine, which reduces fuel consumption and at the same time improves the durability of the components and reduces the need for maintenance.

The inventive method of controlling the hydrostatic propulsion transmission of a work vehicle is presented in claim 1.

A principle in the invention is to limit the maximum rotational speed of the diesel engine at the same time as limiting the maximum running speed of the work machine. The result is that in the maximum position of the pedal or another corresponding control value given by the driver, a rotational speed is reached which is lower than the previous maximum rotational speed which is in use during normal driving.

A principle in the invention is to further use the parameters, which were used for the selection of driving at a low speed, also for controlling the primary power source. The two, ie. both the maximum driving speed and the maximum engine speed of the diesel engine, now depends on the value of said one parameter. Typically, said speeds are substantially linear depending on the position of the pedal, a signal indicating the position of the pedal or another control value given by the driver which can be given, for example, by changing the position of a control lever.

The desired driving speed achieved with the invention is achieved with a lower rotational speed, if the power demand has not increased and a higher rotational speed is not necessary. The invention also uses an extended operating condition for normal driving, which does not affect the diesel engine's maximum rotational speed, ie. it is not limited, or the maximum driving speed, ie. the speed is not limited, for example, by limiting the volume of the pump. On the other hand, the function of the pedal is affected so that the requested driving speed is reached with a smaller pedal movement, ie. the pedal for fl movement from the free position is less than during the condition of normal driving. The same also applies to a change in the control value.

The produced extended condition, which can also be called a condition for fast driving, is applicable especially when driving the work machine, for example a truck, on level ground when the power requirement is not great, ie. when driving on country roads or on other level surfaces.

For recovery, it is typical that the required driving speed is reached with a smaller pedal movement than before. The travel speed is no longer linear depending on the position of the pedal, although the maximum rotational speed and the maximum travel speed are still reached with the maximum position of the pedal.

The state for fast driving can also be used as such, by controlling it with its own parameter that the driver can set and enter into the control system. A particular advantage is obtained when it is used to supplement the function of the propulsion transmission in connection with such slow driving which limits the maximum rotational speed of the diesel engine. In the state for fast running, a fixed or adjustable parameter is used which affects the function of the drive transmission. The fast-running state is used when the slow-running state is not in use, ie when its parameter is set to 100% (or 1.0). The work machine's control system automatically provides for the change between states, depending on the value that the user and the driver of the work vehicle select for the parameter and enter into the control system.

A further principle in the invention is to use the parameter used in the selection of slow travel also for controlling the diesel engine, and in addition for controlling the power transmission so that the same parameter also determines that said state of fast driving is used. The maximum travel speed and the maximum engine speed of the diesel engine as well as the travel speed determined by the pedal now depend on the value of said adjustable parameter. As an example, a parameter is used that can be set between 0% and 200% or between -100% and +100%, or by using some other suitable minimum or maximum value. In the example presented, the range from 0% to 99% is the allocation for slow driving, 100% for normal driving and the range from 101% to 200% is the allocation for fast driving.

Brief description of the drawings In the following description, the invention will be illustrated in more detail by means of examples and with reference to the accompanying drawings, in which fi Figure 1 shows components and the principle of the system according to the invention, urer Figures 2 and 3 show operation according to the prior art under normal driving, fi clocks 4 and 5 show function according to the prior art during slow driving, 10 15 20 25 30 35 534 530 6 urer clocks 6 and 7 show components for controlling the system according to the invention, fi clocks8 and 9 show function according to the invention during slow driving - fi clocks 10 and 11 show function according to the invention during fast driving, and urer clocks 12 and 13 show function according to the invention during fast driving using another example.

DETAILED DESCRIPTION OF THE INVENTION According to Figure 1, forest machines typically use a hydrostatic propulsion transmission 7 which converts the mechanical force produced by the diesel engine 1 into a hydraulic force a pump 8, the force being proportional to the feed pressure and volume of the pump 8. The pump 8 is generally adjustable, whereby the volume fl can be varied. The hydraulic power is utilized in a motor 9 which in turn generates a driving torque and a rotational speed for a PTO shaft. The rotational speed of the motor 9 depends on the volume fl fate and the setting of the motor 9. The motor 9 is again connected to a gear 10, through which the mechanical power is transmitted to the wheels of the work machine, for example by a gimbal drive 11 and differential shafts 12 to bogies 13 with the wheels of the work machine which are mounted on rotating wheel suspensions. The hydrostatic propulsion transmission 7 is controlled by the work machine's electronic control system 6, and the diesel engine 1 can be controlled by an electronic control unit 14 (ECU).

Figure 1 shows a solution in the form of a closed circuit and a single-circuit system, in particular a single-motor system. With the help of the hydrostatic drive transmission, a steplessly adjustable driving speed is achieved for the work machine, since the pump and the motor are infinitely adjustable. In addition, a high traction force for the wheels can be achieved even with low rotational speeds of the diesel engine. 10 15 20 25 30 35 534 530 7 The pump 8 is, for example, an axial piston pump which can be adjusted in its stroke volume (Vg) with an oblique disc, where the direction of the volume and at the same time the driving direction of the working machine can be changed by turning the oblique disc on both sides of the neutral intermediate position. The controllable quantities are thus the stroke volume of the pump and at the same time the volume av produced by the pump. The engine is, for example, an axial piston engine with an oblique disc or an oblique shaft, or a radial piston engine which can also have a fixed volume, the engine not being adjustable. The controllable parameters are thus the engine stroke volume (Vg) and rotational speed.

Control systems have been used for controlling forest machines in a known manner.

The control system monitors b | .a. the forest engine's diesel engine, hydrostatic drive transmission, and all with these associated auxiliary functions. Said control system works e.g. in a PC operating environment. The steering system's screen and central unit are located within easy reach of the driver in the cab. Regarding the connection to actuators, the control system's automatic control is based on a CAN bus solution according to the prior art, where information is transmitted in digital form.

Figure 6 shows in more detail the equipment for the control system to be placed in the vicinity of the driver in the operator's cab. The control system equipment includes an on-screen module 62, a PC keyboard 63, a touchpad mouse 64, a central processing unit (HPC-CPU) with processor and memory 65, and a printer 66, a hub module and a seat module. Control values of the method according to the invention are produced graphically for the user through the display module 62. According to fi gur7, the equipment also includes one or fl your control panels 71, whose keys, pushbuttons and control lever are used to influence the control system.

The application required for carrying out the invention and the software contained therein are installed in the control unit's central unit, which includes the necessary RAM and mass memories. The installation of the applications is performed either in a new forestry machine or as retrofitting in an older forestry machine, the transmission medium for the applications being, for example, a CD-ROM. For example, the core module includes the required CD-ROM drive. The control system uses an operating system known per se, during which the application is run. 10 15 20 25 30 35 534 530 8 The Execution Environment can be different computers with operating systems, especially processor-based control systems for forest machines, ie. harvesters, which are intended for the operation of applications and software serving the control system, in particular a personal computer (PC, Personal Computer) mounted in the forestry machine or a workstation functioning as such which has an appropriate operating system. The device and the operating system include the necessary applications and protocol means for communication with other devices.

The structure of the digital control and measurement system for a forestry machine and especially a harvester is based on CAN bus technology (Controller Area Network) and on decentralized control. The system consists of independent intelligent modules that communicate via a CAN bus. The system controls the diesel engine, the hydrostatic drive transmission, the boom system and the harvester head as well as these associated auxiliary functions. The system typically consists of six or seven modules that are located in the CAN bus and which are shown in more detail in Figure 7. The system's modules include e.g. a display module HPC-D, the computer central unit HPC-CPU (Harvester PC -Computer Processor Unit), a hub module (Hub module), to which the other modules are directly connected, with the exception of the screen and the harvester main module. To a seat module Ch (Chair module) are connected actuators and control panels 71 needed to control the system. Connected to the seat module are i.a. an accelerator pedal or a pedal, which the driver presses during operation of the work machine to change the driving speed. A suitable sensor is connected to the pedal, for example a control resistor, the function of which is to give the control system a signal (ref) which depends on the position of the pedal. The position of the pedal can change steplessly between the free position and the maximum movement. A power transmission module Tr (Transmission module) provides control and communication of the base machine's diesel engine, drive power transmission and the associated auxiliary functions. In other words, the power transmission module controls the stroke volume of said pump and motor. The ECU (Engine Control Unit) is the engine control unit that controls and monitors engine functions. The rotational speed is obtained from the diesel engine, and on the other hand, a signal indicating the desired rotational speed of the diesel engine can be fed into the control unit (ECU) through the control system. In a truck, the system is more limited than in a harvester, in terms of modules. 10 15 20 25 30 35 534 530 9 According to fi gur2, the drive transmission is usually controlled so that in the maximum position of the pedal the maximum travel speed 23 of the working machine can be reached, linearly in relation to the position of the pedal, the speed being zero in the free position of the pedal. Figure 3 shows the function of the stroke volume of the pump (curve 31) and the engine (curve 32) in the positions of the pedal (the horizontal axis) corresponding to fi figure 2. In figure 2, the rotational speed of the diesel engine starts to increase from the level 800 rpm, and the travel speed is indicated tion speed (from 0 to max 4300 rpm). In the same way, the rotational speed of the diesel engine also changes, but from a certain minimum rotational speed. A certain minimum level can be determined for the rotational speed, below which it must not fall, so that the rotational speed may start to increase possibly later, only after the pedal has been pressed sufficiently. The minimum level is determined, for example, when a higher van / speed and power are needed for the other functions of the forestry machine. More specifically, the control of the pump and the motor is designed so that the motor has its maximum stroke volume and you start to increase the stroke volume of the pump when you press the pedal.

When the pedal is pressed further down, the stroke volume of the pump finally reaches its maximum, starting to reduce the stroke volume of the engine. In this way, the desired driving speed is reached in each pedal position.

Figure 4 again shows a situation in which the crawler gear, ie slow driving, is in use. It is found that the rotational speed of the motor (travel speed 42) is limited by the fact that the volume produced by the pump relative to the pedal position is limited in comparison with the normal situation shown in Figure 2. The engine speed of the diesel engine (curve 41) is maintained corresponding to normal driving. In fi gur5 it is detected that the pump (curve 51) does not reach its maximum stroke volume at all and that the position of the motor does not change (curve 52).

Figure 8 shows a situation in which, in addition to slow driving, the limitation of the maximum speed 84 of the diesel engine is also used, on the basis of a common adjustable parameter which is set to the value 10%. It is discovered that the rotational speed of the diesel engine (curve 81) is linear depending on the position of the pedal, but in the maximum position of the pedal the rotational speed is limited to the value 1280 rpm, when in the situation of fi gures 2 and 4 it was 2040 rpm. The travel speed (curve 82) has the maximum value 83 which corresponds to fi gur 4. In fi gur 9 you see the function of the power transmission in comparison with fi gur 5. In fi gur 9 you discover that 10 15 20 25 30 35 534 530 10 when the diesel engine's rotational speed decreases , the pump volume fl fate and stroke volume (curve 91) must be increased to reach the same engine speed. Engine displacement does not change (curve 92).

Figure 10 shows a situation, in which the fast driving state is in use, on the basis of an adjustable parameter which may be common to the slow driving state and the normal state. The value of the parameter is set in the value 200% (on the scale from 0% to 200%).

In fi gur 10, the function of the travel speed (curve 104) corresponding to fi gur2 has also been plotted for comparison. It is discovered that in the state of fast driving (curve 101), for example, the speed of 2000 rpm is reached in the pedal position of approx. 0.23 (23%), when normally (curve 104) is first reached in the pedal position of approx. 0.47 (47%). The biggest difference in pedal positions is in the driving speed of approx. 2750 rpm, which is due to the fact that the driving speed operates linearly for two different periods one after the other but includes a discontinuity point 105 at the driving speed of approx. 2750 rpm. However, the end point 106 and the starting point of the travel speed curve 101 are the same as in the normal state, according to Figure 2. The rotational speed of the diesel engine (curve 102) has the same maximum value 103 as during normal driving. Figure 11 shows the function of the drive transmission in comparison with Figure 3. The pump is controlled to the maximum stroke volume more quickly (curve 112), ie with a shorter pedal movement, and in addition the engine stroke volume is reduced more quickly (curve 111). The control according to what is produced means that the engine reaches its minimum stroke volume earlier, which causes the said discontinuity point 105. Thereafter, the driving speed is only affected by the increasing engine speed of the diesel engine, since the stroke volumes do not change, but only the volume produced by the pump.

Figure 12 shows an example, in which the parameter for fast driving is set to the value 150% (on the scale from 0 to 200%). It is detected that the discontinuous fast travel curve 121 begins to approach the driving speed curve 124 which is in use in the normal state. In 13 gur 13 it is discovered that the pump and the motor are controlled at a later stage than in fi gur 11, ie. the movement of the pedal is longer. The maximum values 123 and 126 correspond to those shown in Figure 10, and the curve 122 over the rotational speed is also the same. The discontinuity point 125 is reached later, with a longer pedal movement. 10 15 20 25 534 530 11 With reference to fi gur1, the invention is applied so that the parameter (set) is fed to the control system 6, which in turn controls the motor control unit 14 (ECU) by giving it a signal 15 corresponding to the requested rotational speed. The setting of the parameter (set) has been shown with a switch 16 which can also be a Greek representation on the display of the display module, which is controlled by means of a pointing device. It can also be a percentage or another ratio or value that is entered into the control, for example through a keyboard. The requested rotational speed is again proportional to the position of the pedal 3 in such a ratio or relation as is determined by the value of the parameter. The pedal position signal 5 is obtained from a sensor 4 which follows the position of the pedal 3. Instead of the pedal 3, you can also use another control value (ref) with a corresponding function. The control system knows the maximum rotational speed and the minimum rotational speed, which are obtained from the diesel engine 1 and to which the requested rotational speed is related. The pump 8 and the motor 9 are controlled by the control system as presented above, by controlling the setting of their stroke volume. In the application of the invention, per se known software applications, components or parts intended for pre-existing control systems are used, which are modified in a manner provided by the invention. However, the modification work and application is clear to a person skilled in the art on the basis of the foregoing description.

The invention is not limited only to the examples presented above, but it may vary within the scope of the appended claims.

Claims (6)

10 15 20 25 30 35 534 530 12 Patent claims A method of controlling hydrostatic propulsion transmission and a primary power source of a working machine, the method comprising a state of normal driving and a state of fast driving, wherein the driver can select by means of a parameter which of these states is to prevail, and wherein the hydrostatic the driving force transmission in the fast-driving condition is controlled in such a way that the driving speed is proportional to a steering value given by the driver, but higher than the driving speed in the normal driving condition for the same driving value given by the driver, characterized in that the primary speed normal driving and fast driving in such a way that the rotational speed is proportional to the control value given by the driver, the rotational speed in fast driving being proportional to the control value given by the driver but higher than the rotational speed in normal driving for the same control value given by the driver. Method according to claim 1, characterized in that: power is transmitted to the hydrostatic power transmission by means of the primary power source, the hydrostatic propulsion power transmission during normal driving is controlled in such a way that the driving speed thus obtained is proportional to the control value given by the driver, which may vary within predetermined limits. Method according to claim 2, characterized in that the maximum permissible value for the rotational speed during fast driving is substantially the same as the maximum permissible value of the rotational speed during normal driving, and the maximum permissible value of the driving speed during fast driving is substantially the same as the maximum permissible value of the driving speed during normal driving. 10 15 20 25 534 530 13 Method according to Claim 1, 2 or 3, characterized in that the ratio between the control value and the travel speed during fast driving is substantially non-linear, so that the travel speed changes faster at small values of the control value than at large values of the control value. Method according to Claim 4, characterized in that the relationship between the control value and the travel speed consists of two linear sections one after the other. A system for controlling hydrostatic propulsion transmission and a primary power source of a work machine, which system comprises a control system (6) arranged to control the function of the hydrostatic propulsion transmission for normal driving so that the driving speed is proportional to a control value given by the driver, both in a state of normal driving and a state of fast driving, wherein the driver by selecting a parameter can choose which of these conditions should prevail, and wherein the control system (6) controls the function of the hydrostatic propulsion transmission in the state of fast driving on such way that the driving speed is proportional to a control value given by the driver, but higher than the driving speed in the state of normal driving for the same control value given by the driver, characterized in that the system is further arranged to control the function of the hydrostatic drive transmission in the fast driving state. the rotational speed is proportional to that of the driver given the steering value but higher than the speed at normal driving for the same steering value given by the driver.