WO1995004233A1

WO1995004233A1 - Vehicle with automatic mechanical transmission

Info

Publication number: WO1995004233A1
Application number: PCT/EP1994/002502
Authority: WO
Inventors: Fritz Eberhard Braun
Original assignee: Gebr. Holder Gmbh & Co.
Priority date: 1993-07-31
Filing date: 1994-07-29
Publication date: 1995-02-09
Also published as: DE4325788A1

Abstract

A vehicle (10) comprising an internal combustion engine (20), a transmission unit (26) whose ratio can be adjusted continuously by means of a controlling element, and a mechanical gear unit (28) which can be set to different ratios by means of a number of sets of gear wheels (38, 30; 38, 42), can be improved as follows to allow it to be operated with simple means over the greatest possible range of speeds: a switching element is provided to allow switching from a first set of gear wheels to a second set (38, 30; 38, 42), a speed range control is provided for automatic changing of the gear wheel set (38, 30; 38, 42) when a switching signal is applied, this being done by having the speed range control in a first switching step actuate the switching unit in such a way that the latter terminates the mutual engagement of the first set of gear wheels (38, 30; 38, 42), in a second switching step and via the continuously variable transmission unit (26) approximate the peripheral speed of the gear wheels of the second set (38, 42; 38, 30) in the engagement area and, in a third switching step, cause the second gear wheel set (38, 42; 38, 30) to engage mutually.

Description

Vehicle with automatically switching mechanical transmission

The invention relates to a vehicle comprising an internal combustion engine, a transmission which is infinitely variable in its translation by means of an actuating element, and a mechanical transmission which can be switched into different ratios by in each case bringing gear wheels into interaction with one of several sets of gear wheels.

Such a vehicle is known for example from German patent application 41 11 921.5. In this vehicle, however, the mechanical transmission cannot be shifted while driving, so that in every mode of operation of the vehicle according to the invention, a predetermined gear wheel set is used, the continuously variable transmission being a hydrostatic transmission which adjusts the gear ratio an optimal load on the internal combustion engine is permitted.

However, such a continuously variable transmission is structurally complex and therefore costly to manufacture if it is to work over a large gear ratio range.

The invention is therefore based on the object of improving a vehicle of the generic type in such a way that it can be operated with simple means over the largest possible speed range with the best possible adaptation of the overall ratio of the vehicle to the internal combustion engine. This object is achieved according to the invention in a vehicle of the type described in the introduction in that a switching element which interacts and disacts the respective gear wheels and which provides a switching control is provided for switching from a first set of gears to the mechanical transmission Which, when a switching signal is present, automatically changes the gear set by controlling the actuating element and the switching element in such a way that in a first switching step the switching control controls the switching element in such a way that it disables the first gear set, in a second switching step controls the actuating element in such a way that the continuously variable transmission approximates the peripheral speed of the gearwheels of the second gearwheel set in the engagement area and controls the switching element in a third switching step so that it controls the second gearwheels interaction.

The solution according to the invention can thus be seen in the fact that the continuously variable transmission is used to switch the mechanical manual transmission automatically controlled by the shift control while driving, the variable transmission of the continuously variable transmission also being controlled for switching in order to adjust the speed quickly the gear sets to be brought into engagement with one another.

The invention relates to transmissions with a total of at least two sets of gearwheels, the first set of gearwheels being the one that is effective before the shifting process and the second set of gearwheels that is effective after the shifting process. The mechanical manual transmission can be a synchronized transmission.

However, it is also possible to use an unsynchronized transmission as the mechanical manual transmission, since the continuously variable transmission opens up the possibility of carrying out the approximation of the peripheral speeds of the gear wheels to be interacted with one another with the required accuracy.

The advantage of the solution according to the invention can be seen in particular in the fact that the combination according to the invention of a continuously variable transmission with a mechanical manual transmission opens up the possibility of operating this combination in exactly the same way as a conventional powershift transmission used in automatic transmissions in the form of a planetary gear transmission . In particular, in the solution according to the invention, the control according to the invention of the continuously variable transmission during shifting also eliminates a torque converter customary in an automatic transmission, since this is replaced by the continuously variable transmission.

The present solution according to the invention ultimately represents, in its effect as an overall solution, an overall transmission which is adjustable over a very large range, the adjustability over a very large range not being achieved solely by the continuously variable transmission itself, but by combining the same with a mechanical manual transmission, which, in the simplest case, can also be a very simple unsynchronized manual transmission, for example in the manner of a countershaft transmission normally used. In principle, it is possible with the solution according to the invention to keep the translation of the continuously variable transmission constant during the first switching step and to act with sufficient force on the gear wheels of the first gear wheel set which are in interaction in order to bring them out of interaction.

However, it is even more advantageous if the shift control activates the actuating element in such a way that it reduces the translation of the continuously variable transmission during the first shift step. This relieves the load on the gear wheels of the first gear wheel set which are in interaction with one another, so that they can be more easily disengaged.

However, in order not to have to accept excessive speed losses, it is preferably provided that the shift control reduces the ratio of the continuously variable transmission in the sense of a slight braking of the vehicle during the first shifting step. Regardless of whether the vehicle is braked otherwise or not, this creates the possibility of relieving the gear wheels of the first gear wheel set that are interacting.

With regard to the translation of the continuously variable transmission during the third switching step, no further details were given in connection with the explanation of the above exemplary embodiments. An advantageous embodiment provides that the shift control controls the actuating element in such a way that the continuously variable transmission during the third shift step keeps the translation essentially constant. As a result, the gear wheels of the second pair of gear wheels can be easily engaged during the third switching step.

However, the essentially constant transmission ratio does not mean that this must be completely constant. The gearwheels of the second gearwheel set can be brought into engagement particularly easily if the translation of the continuously variable transmission deviates slightly from a constant value, for example in the manner of an oscillation around the constant value, so that the gearwheels of the second gearwheel set result from the small fluctuations in speed that occur can interact more easily, that is to say, for example, come into engagement.

With regard to the type of generation of the switching signal, no further details have been given in connection with the previous explanations of the individual exemplary embodiments. An advantageous exemplary embodiment provides that the switching signal can be generated by a switching signal generator, the switching signal generator being able to generate the switching signal on the basis of a wide variety of driving conditions or on the basis of an intervention on the part of the operator.

In order, in particular, to be able to shift the mechanical transmission automatically, that is to say without direct intervention by the operator, a triggering device for the shift signal is preferably provided, which detects a driving parameter of the vehicle and triggers the shift signal when a shift value of the driving parameter is reached. This enables an automatic change between the individual ratios of the mechanical transmission, so that the vehicle according to the invention can be operated like a vehicle provided with an automatic transmission.

The driving parameters, which are detected by the triggering device, can be of the most varied types. For example, it would be conceivable to use the speed of the vehicle as the driving parameter.

However, it is particularly advantageous, in particular when the internal combustion engine is to be operated with optimal load, when the driving parameter is the transmission of the continuously variable transmission. In this solution according to the invention it is assumed in particular that the transmission ratio of the continuously variable transmission is adapted in accordance with a respective maximum load on the engine, this adaptation preferably also taking place automatically.

In order to be able to select both a larger transmission ratio of the mechanical transmission and a smaller transmission ratio of the mechanical transmission with the shift control, it is preferably provided that an upshift signal or a downshift signal can be applied to the shift control.

For the automatic operation of the vehicle according to the invention, it is provided in particular that the triggering device can be given switching points for the upshift signal and the downshift signal by specifying an upshift value and a downshift value of the translation of the continuously variable transmission. The switching control according to the invention thus changes depending on the translation of the Infinitely adjustable gearbox also the ratio of the mechanical gearbox. This means that when the upshift value or the downshift value is reached, the shift control automatically switches from the first set of gear wheels to the second set of gear wheels.

The transmission ratio of the continuously variable transmission can also be recorded in a wide variety of ways. A simple solution provides that the triggering device detects a control signal of the control element as a driving parameter, since this control signal of the control element is in turn proportional to the ratio of the continuously variable transmission.

In the context of the explanation of the exemplary embodiments described above, it was not discussed in detail how the circumferential speed of the gear wheels of the second gear wheel set to be brought into interaction should be approximated in detail.

The simplest solution provides that the shift control for changing the peripheral speed of the gear wheels of the second gear set changes the ratio of the continuously variable transmission by a value that can be predetermined for the shift control. This means that the gear ratio is reduced by a predeterminable value when shifting up and the gear ratio is increased by a predeterminable value when shifting down. A particularly simple exemplary embodiment of the solution according to the invention provides that the value which can be predetermined for the shift control is fixed, that is to say that when shifting up, the shift control always reduces the ratio by the fixed predetermined value and when shifting down, the ratio is always reduced by fixed predetermined value increased.

The above-mentioned solution can preferably be used particularly when upshifting at a single upshift value and downshifting at a single downshift value.

If an upshift and downshift are to take place with different ratios of the continuously variable transmission, a further exemplary embodiment provides that the value depends on the ratio of the continuously variable transmission that is present at the beginning of the first switching step. This creates the possibility to adjust the value individually.

Another advantageous exemplary embodiment provides that the value depends on the transmission ratio of the mechanical transmission that is present at the beginning of the first shift step. This is particularly advantageous in order to differentiate between an upshift and a downshift and also if more than two gear sets are to be shifted.

As an alternative to the solutions described above, an advantageous exemplary embodiment provides that the shift control detects the speed of the gear wheels of the second gear wheel set and that via the control element Ratio of the continuously variable transmission controls so that the gears to be brought into interaction have approximately the same peripheral speed in their engagement area.

This can be achieved particularly easily if a speed sensor is arranged on the drive side and the drive side of the mechanical transmission.

In order to be able to carry out the appropriate speed adjustment in accordance with the gear ratios in a simple manner, it is preferably provided that the shift control can be specified with the required speed ratios for the respective second set of gear wheels.

The switching control can be constructed in a wide variety of ways. For example, it would be conceivable to set up the switching control as an analog control. However, it is particularly advantageous if the switching control comprises a process computer and a programmable memory.

At least the value for adapting the peripheral speed of the gear wheels of the respective second gear wheel set is expediently stored in the memory. This is particularly necessary when the circumferential speeds are to be adjusted in a controlled manner with the shift control according to the invention, since in this case the speed ratios of the second gear set in each case must be taken into account in the control. No details have yet been given regarding the design of the triggering device. An advantageous exemplary embodiment provides that the triggering device comprises a process computer and a programmable memory and that at least one switching value, preferably at least one upshifting value and one downshifting value, is stored in the memory.

With regard to the control of the continuously variable transmission, no further details have been given in connection with the previous exemplary embodiments. An advantageous exemplary embodiment provides that a drive control is provided for controlling the continuously variable transmission, which has a process computer and a programmable memory.

The drive control is preferably connected to a position transmitter of an actuating device, which detects the respective position of the actuating device and transmits a maximum parameter to the drive control, and it is provided that the drive control translates the translation of the continuously variable according to a program stored in the memory and the transmitted maximum parameter adjustable gear controls.

The advantage of this solution can be seen in the fact that an optimal adaptation of the ratio of the hydraulic transmission to the performance characteristics of the internal combustion engine is possible in a simple manner and that, moreover, an optimal adaptation to a wide variety of internal combustion engines can also be carried out in a simple manner. Furthermore, the solution according to the invention additionally offers the possibility of networking a large number of parameters when controlling the transmission ratio of the hydraulic transmission. With regard to the type of continuously variable transmission, no further details have been given in connection with the previous explanation of the exemplary embodiments. A particularly advantageous exemplary embodiment provides that the continuously variable transmission is a hydrostatic transmission which comprises a hydraulic pump driven by the internal combustion engine and a hydraulic motor driven by the hydraulic pump, the transmission ratio of the hydrostatic transmission being proportional to the constant displacement volume of the hydraulic motor Delivery volume of the hydraulic pump is.

The programmable memories are preferably each designed as interchangeable memory modules, so that the driving control and the shift control can always be constructed identically and an adaptation of the same to different internal combustion engines or different mechanical gears or other different purposes by exchanging the memory module stones is possible in a simple manner.

It is even more advantageous if the programmable memories have a plurality of programs which are coordinated for special uses of the vehicle according to the invention and are stored in them, so that, depending on the intended use of the vehicle, a program for driving control and the control system which is specifically tailored to this purpose Switching control can be used and thus an even more optimal adaptation to the required criteria and the performance characteristics of the internal combustion engine is possible. In the driving control in particular, it has proven to be particularly advantageous if the transmission ratio of the continuously variable transmission is controlled according to different criteria, wherein in addition to different measured parameters of the operating state of the vehicle according to the invention, different performance characteristics of the internal combustion engine can also be used as criteria.

For example, it is advantageous if the program is used to control the translation of the hydrostatically adjustable transmission in accordance with a load on the internal combustion engine, since the load on the internal combustion engine is one of the most significant criteria for controlling the translation of the continuously variable transmission.

Particularly advantageous adaptation options result when the transmission of the continuously variable transmission is controlled in accordance with different loads of the internal combustion engine in the different programs.

As an alternative to controlling the translation of the continuously variable transmission in accordance with the load on the internal combustion engine, it is also advantageous if a program is stored in the memory according to which the control of the translation of the continuously variable transmission takes place primarily taking into account the maximum parameter of the actuating device, that means that in this case primarily the load on the internal combustion engine is disregarded and only a control of the ratio of the hydrostatic transmission is carried out as a function of the predetermined maximum parameter, determined by the actuating device. An advantageous embodiment of the solution according to the invention provides that a program "road trip" is stored in the programmable memory of the driving control, in which an adaptation of the criteria to the road trip of the vehicle is possible in particular.

In the "road trip" program, the drive control expediently regulates the translation of the continuously variable transmission to a predefinable load on the internal combustion engine, so that the transmission of the hydrostatic transmission is controlled in this program with performance data optimized for adaptation to the internal combustion engine.

A particularly advantageous way of determining the predeterminable load in the "Road trip" program, in which the vehicle is to be operated like a conventional automatic vehicle, that is to say only with the accelerator pedal in a varying position, provides that the predeterminable load on the Internal combustion engine is defined as a speed-dependent characteristic field in the "Road trip" program.

In connection with the above-described exemplary embodiments according to the invention, it has already been mentioned that the driving control controls the translation of the continuously variable transmission in accordance with the load on the internal combustion engine. However, nothing was said about how the load should be determined. An advantageous version of the solution according to the invention therefore provides that the control system uses a program to determine the load on the internal combustion engine and the ratio of the continuously variable transmission accordingly controls the load on the internal combustion engine. An advantageous possibility for determining the load is that the drive control determines the load on the internal combustion engine from a pressure on the speed of the combustion engine.

For this purpose, it has proven to be advantageous if a sensor is connected to the driving control, which detects an actual speed of the internal combustion engine.

In addition, it is expedient if a sensor is connected to the control, which detects the predefined setpoint speed setting for the internal combustion engine, for example by detecting the position of a setpoint speed setting unit, in particular an injection pump.

If the aforementioned sensors are present, a particularly advantageous example of the driving control according to the invention provides that the process computer determines the load on the internal combustion engine from the predetermined target speed setting and the measured speed.

This is expediently done in that the process computer determines a computational idle speed - that is, a speed that would set itself without loading the internal combustion engine - based on the detection of the predetermined target speed setting, for example via one in the program stored relation between target speed setting and idling speed, and the load on the internal combustion engine is achieved by the deviation of the actual speed of the internal combustion engine from the idling speed. In the simplest case, this load can be determined in such a way that, based on the idling speed, the process computer calculates a nominal speed which corresponds to an appropriate load on the internal combustion engine.

The driving controller advantageously calculates the nominal speed by means of a characteristic field stored in the program.

Several types of characteristic curve fields of the internal combustion engine can now be stored in the program, so that different characteristic curve fields can also be used to calculate the nominal speed. An advantageous exemplary embodiment provides that the control system calculates the nominal speed taking into account the characteristic field of the maximum torque. As an alternative or in addition to this, in a further advantageous exemplary embodiment it is provided that the control system calculates the nominal speed taking into account the characteristic field of the maximum power.

In the case of a continuously variable hydrostatic transmission, the transmission ratio of the continuously variable transmission is controlled, for example, by controlling the delivery volume of the hydraulic pump. Alternatively or in addition, it is also conceivable to control the swallowing volume of the hydraulic motor.

Further features and advantages of the solution according to the invention are the subject of the following description and the drawing of some exemplary embodiments. The drawing shows:

Fig. 1 is a side view of an inventive

Vehicle, in this case, for example, a municipal vehicle;

2 shows a plan view of the vehicle according to the invention;

FIG. 3 shows a drive diagram of the vehicle according to FIG. 1;

FIG. 4 shows a hydraulic and control diagram of the vehicle according to FIG. 1;

Figure 5 is a schematic representation of the change in a translation of the continuously variable transmission in the individual switching steps when shifting up.

6 shows a representation of the translation of the continuously variable transmission during the individual switching steps when downshifting;

7 shows a hydraulic and control diagram of a variant of the first exemplary embodiment;

Fig. 8 is a drive diagram similar to Fig. 3 of the variant of the first embodiment, shown in Fig. 7 and

FIG. 9 shows a drive diagram similar to FIG. 4 of a second exemplary embodiment. An embodiment of a vehicle according to the invention, in this case a municipal vehicle with power take-off, shown as a whole in FIGS. 1 and 2, comprises a chassis 10 with a front axle 12 and a rear axle 14, the front axle having front wheels 16 and the rear axle is provided with rear wheels 18.

The vehicle is driven by an internal combustion engine, designated as a whole by 20, which, as shown in FIG. 3 and explained in detail in connection with this figure in the following, drives a hydraulic pump 22 via which a hydraulic motor 24 is driven. The hydraulic pump 22 and the hydraulic motor 24 form a hydrostatic transmission 26.

The hydraulic motor 24 in turn drives a mechanical transmission, designated as a whole by 28, via which either the front axle 12 or the rear axle 14 or both can be driven.

The mechanical transmission 28 comprises a slow speed stage 30 with two transmission gears 32 and 34, the transmission gear 32 being seated on a drive shaft 36 of the mechanical transmission 28 and the transmission gear 34 being able to be coupled to a change gear 38 without synchronization, the change gear or the shifting center 38 is axially displaceable, but is non-rotatably connected to an output shaft 40 of the mechanical transmission 28 in order to be able to be coupled or uncoupled to the transmission gearwheel 34. In addition, the mechanical transmission 28 includes a high-speed stage 42, which comprises a gearwheel 44 seated on the drive shaft 36 and a gearwheel 46 rotatably seated on the output shaft 40, wherein the gearwheel 46 can also be coupled to the change gear or the shifting center 38 without synchronization.

By means of the shift center 38 there is now the possibility of driving the output shaft 40 either in accordance with the gear ratio of the slow speed stage 30 or the gear ratio of the high speed stage 42, depending on the gear mechanism 34 or 46 with which the shift center 38 interacts.

To move the switching center 38 in the axial direction of the output shaft 40, a switching device, designated as a whole by 50, is provided, which engages with a switching fork 52 on the switching center 38, the switching fork 52 in a displacement guide, designated as a whole by 54, parallel to the output shaft 40 is slidably mounted. The shift fork 52 is shifted via a hydraulic cylinder, designated as a whole by 56, which can be controlled by an electrically controllable shift valve 58, the hydraulic cylinder being able to couple the shifting center 38 to the gear wheel 34 into one Bring intermediate position or to couple with the gear wheel 36. For this purpose, a monitoring element 60 is preferably provided which detects the individual positions of the hydraulic cylinder and which, for example, detects the position of a piston 62 of the hydraulic cylinder 56. The internal combustion engine 20 also drives a front power take-off 70 and a rear power take-off 72, these power take-offs 70, 72, as also shown in FIG. 3, can be coupled directly to the internal combustion engine via a power take-off clutch 74.

Additional devices 76 can now be mounted on the chassis 10 of the municipal vehicle according to the invention, which can be driven via the power take-off 70 or 72 assigned to the respective side. These additional devices can be snow blowers or a mower or other additional devices.

As shown in FIGS. 1 and 2, the municipal vehicle according to the invention is conventionally steered via a steering wheel 80. In addition, the internal combustion engine 20 is regulated via an accelerator pedal 82 and a hand throttle lever 84 in accordance with the respective requirements. The individual driving states of the municipal vehicle can be influenced by the operator via the following operating options, the individual operating options being explained in detail below. Thus, a program selection switch 86 is provided for selecting a driving program, a travel direction pre-selection lever 88 for selecting the direction of travel between forward travel and reverse travel and a zero position, furthermore a fixed setting lever 90 and finally a reset pedal 92, which is arranged as in conventional municipal vehicles the clutch pedal, that is to say to the left of the steering wheel 80 as seen in the direction of travel. Furthermore, the locking lever 90 is preferably also arranged on the left of the steering wheel 80 as viewed in the direction of travel F, while the directional selection lever 88 is to the right of the steering wheel 80. As shown schematically in FIG. 3, the front axle 12 and the rear axle 14 are driven via the internal combustion engine 20, which drives the hydraulic pump 22 via a connecting element 94 and a central drive train 96. The hydraulic pump 22 is preferably an axial piston pump, which drives the hydraulic motor 24 via two hydraulic lines, designated 98 and 100 in FIG. 4. This hydraulic motor 24 in turn drives, via a gear set 102, the gearwheel 44 seated on the drive shaft 36 of the mechanical transmission 28 and thus the drive shaft 36 of the mechanical transmission.

The output shaft 40 of the transmission 28 leads on the one hand to the rear axle 14 and via an extension 104 to the front axle 12.

Furthermore, both the rear power take-off 70 and the front power take-off 72 can be activated simultaneously via the power take-off clutch 74, both power take-offs 70 and 72 being mechanically driven directly by the internal combustion engine 20 when the power take-off clutch 74 is closed.

A speed sensor 106 is assigned to a drive wheel of the hydraulic pump 22, for example, to detect a speed of the internal combustion engine 20. Furthermore, the speed of the output shaft 40 of the mechanical transmission 28, which is directly proportional to the speed of the municipal vehicle, is detected by a speed sensor 108. As can be seen from the overall representation of the hydraulic diagram in FIG. 4, the hydraulic pump designed as an axial piston pump is provided with a feed pump 110 which, on the one hand, is used to replace leakage losses in the circuit, formed by the hydraulic pump 22, the lines 98 and 100 and the hydraulic motor 24, ensures, on the other hand, a hydraulic cylinder system 114 for controlling the pivoting cradle of the hydraulic pump 22 is supplied with pressurized hydraulic medium via the feed pump 110 and a feed pressure line system 112.

A detailed description of the principle of an axial piston pump and the principle of a hydraulic cylinder system for adjusting the pivoting cradle and the resulting adjustment of the delivery volume of the hydraulic pump 22 can be found in German Patent 32 45 518, to which reference is made in full.

A pressure control valve 118 is provided as an example to maintain a constant feed pressure in the feed pressure line system 112.

In the simplest case, the hydraulic motor used in the municipal vehicle according to the invention is a hydraulic motor whose displacement volume per revolution of its output shaft 120 cannot be changed.

Alternatively, however, it is also conceivable to use an adjustable hydraulic motor, as described, for example, in German patent application 41 11 921.5. Furthermore, it is conceivable in the hydrostatic transmission 26 according to the invention to provide such a hydraulic pump 22 with a constant delivery volume and to design the hydraulic motor 24 to be controllable in terms of its swallowing volume, so that in this case the hydraulic cylinder system 114, for example, a pivoting cradle of the hydraulic motor 24 controls.

To reverse the direction of travel, it is provided that a conveying direction of the hydraulic pump 22 is reversible. With regard to details of the design of the hydraulic pump and the hydraulic motor, reference is made to the German patent application P 41 11 921.5.

For operation of the municipal vehicle according to the invention, in particular for the operation of the hydrostatic transmission, a drive control, designated as a whole in FIG. 4 with 130, is provided, which comprises a process computer 132 and a programmable memory 134 assigned to this process computer.

The process computer 132 is preferably a microprocessor and the programmable memory 134 is an EPROM which can be used, for example, interchangeably or non-programmably in the drive control 130.

The driving control 130 controls a proportional control valve 136, which in turn serves to control the hydraulic cylinder system 114 and thus to control the delivery rate of the hydraulic pump. In both cases, process computer 132 operates according to a program stored in programmable memory 134. For example, three programs P1, P2 and P3 are stored in the programmable memory 134 and can be called up individually via the program selector switch 86 connected to the process computer 132.

A process direction selector switch 138 actuated by the direction selection lever 88, the speed sensor 106 and the speed sensor 108 are also connected to the process computer 132, which have already been mentioned in connection with FIGS. 1 and 3.

The fixed setting lever 90 explained in connection with FIGS. 1 and 2 and the return lever 92 are part of an adjusting device, designated as a whole by 140, with which a position transmitter, for example in the form of a potentiometer 142, can be set.

Different maximum parameters for the individual driving states can be specified to the process computer 132 via the actuating device and thus via the position transmitter 142.

An example of such an actuating device 140 is described in detail in German patent application 41 11 921.5 in FIG. 5, so that reference is expressly made to the explanations in this application for describing this actuating device.

With the adjusting device 140, on the one hand, a maximum parameter is fixedly predetermined via the fixed setting lever 90, which on the other hand is still smaller than that of the fixed setting lever 90 by actuating the reset lever 92 predetermined maximum parameters can be selected. The maximum parameter can thus be varied between the fixedly set value preselected by the fixed setting lever 90 and a value corresponding to the zero position, the maximum parameter specified by the fixed setting lever 90 being set again, for example, by releasing the reset lever 92.

The effect of the reset lever 92 can be compared with that of a clutch pedal of a conventional vehicle - as will become clear later from the functional description of the drive control 130 - and enables independent of the maximum parameter fixed with the fixed setting lever 90 stopping the municipal vehicle according to the invention is possible in any driving condition.

Furthermore, the drive control 130 is also connected to a potentiometer 144 for detecting a target speed setting, the position of the accelerator pedal 82 being detected, for example, as the target speed setting. In the case of the internal combustion engine designed as a diesel engine, the potentiometer 144 preferably detects the position of an injection pump control lever, as is described in detail, for example, in German patent application 41 11 921.5, to which reference is made here.

In addition, the municipal vehicle according to the invention also comprises a switching control, designated as a whole by 150, which controls the switching valve 58 and also acts on the proportional control valve 136 to switch the mechanical transmission 28. The switching control in turn also comprises a process computer, this process computer preferably being identical to the process computer 132 and a programmable memory 152.

Furthermore, the shift control comprises an integrated triggering device 154, which automatically triggers a shifting process for the mechanical transmission 28. The function of the trigger device 154 can be taken over by the process computer 132 by means of a corresponding program part.

The function of the switching control 150 is shown in FIGS. 5 and 6.

In the exemplary embodiment of the switching control 150 with the triggering device 154 shown in FIG. 4, the switching control detects a feed current I for the proportional control valve 136 as driving parameter, this feed current I in turn being proportional to the translation of the hydrostatic transmission 26.

If the municipal vehicle according to the invention is now started, the journey begins, as shown in FIG. 5, using the slow speed stage 30, the switching center 38 interacting with the gear wheel 34. This state is designated by L in FIG. 5.

In order to accelerate the municipal vehicle, the driving control 130 regulates the translation of the hydrostatic transmission 26 according to the load when the maximum parameter is set accordingly high, as described by way of example in connection with the driving program road travel of the internal combustion engine 20. For acceleration, the ratio of the hydrostatic transmission 26 is continuously increased, for example, until a ratio U-max is reached, this ratio corresponding to a supply current I-max for controlling the proportional control valve 136.

Since the feed current for controlling the proportional control valve 136 is detected by the trigger device 154, the reaching of the current I-max is also recognized. If, for example, the current I-max is defined as an upshift point in the programmable memory 152, the triggering device 154 triggers a switching operation by the switching control 150 via an upshift signal when the current I-max is reached. Such a switching process begins, as shown in FIG. 5, at a time TOH. From the time TOH, the shift control intervenes in the position of the proportional control valve 136 provided by the travel control 130 and reduces its feed current and thus also the transmission ratio of the hydrostatic transmission 26 slightly, for example continuously until a time T1H is reached. This slight and continuous reduction in the transmission ratio of the hydrostatic transmission 26 relieves the connection between the shifting center 38 and the gearwheel 34, so that the shifting center 38 can be disengaged from the gearwheel 34 without any problems.

For this purpose, the switching control 150 controls the switching valve 58 accordingly, so that the switching center comes into an intermediate position Z during the period between TOH and T1H, in which it is neither coupled to the gearwheel 34 nor to the gearwheel 46. For example, the switching valve 58 is actuated by the switching control 150 with a corresponding signal SAH, which is present until the switching center 38 is in the intermediate position Z. This is preferably recognized by the monitoring element 60, which is also connected to the switching control 150.

The time period between TOH and T1H can be predetermined, for example, via the programmable memory 152 and is chosen to be so large that the switching center 38 is certainly in the intermediate position Z. As an alternative to this, it is also conceivable, after the detection of the intermediate position Z by means of the monitoring element 60 of the switching center 38, to regard the time T1 as reached, that is to say to end the continuous reduction in the ratio of the hydrostatic transmission 26.

The switching step in the period between TOH and T1H is referred to as the first switching step.

After the time T1H has been reached, a reduction in the transmission ratio and thus the supply current I for the proportional control valve 114 takes place during a second switching step, for example by a value URH which is constant in the programmable memory 152, the reduction being so large that the switching center 38 and the gear wheel 46 have approximately the same circumferential speed in the mutual engagement range, that is to say in the case of the construction of the mechanical transmission 28, have the same speed and can be brought into interaction without problems. This is finished at a time of T2H. The reduction in the gear ratio in order to achieve an approximately equal circumferential speed between the switching center 38 and the gear wheel 46 in the period between T1H and T2H is referred to as the second switching step.

Between the time T2H and a subsequent time T3H, the transmission ratio of the hydrostatic transmission is kept essentially constant.

At the same time, the switching control 150 transmits the signal SEH to the switching valve 58, so that the hydraulic cylinder 56 engages the switching center 38 with the gear wheel 46, that is to say moves the switching center 38 from the Z position to the S position. For example, the position S is recognized by the monitoring element 60.

The time period between T2H and T3H can likewise be predetermined by the programmable memory 152, or after the position S has been recognized, the time T3 can be regarded as reached.

The switching step between time T2H and time T3H is referred to as the third switching step.

After the third switching step, the switching control in turn enables the control of the proportional control valve 136 by the drive control 130, which in turn controls the translation of the hydrostatic transmission 26 in accordance with the load on the internal combustion engine 20. In Fig. 5, the speed V of the municipal vehicle according to the invention is also given, whereby it can be seen that this initially increases until the time TOH is reached in accordance with the increase in the ratio of the hydrostatic transmission 26, then either remains constant during the switching steps between TOH and T3H or decreases slightly and increases again, for example, from time T3H, but because of the now more effective high-speed stage 42 of the mechanical transmission 28, it is faster than the transmission ratio of the hydrostatic transmission 26, since the transmission ratio of the high-speed stage 42 is greater than that of the slow-speed stage 30.

The mechanical transmission 28 is shifted down in a similar manner when the municipal vehicle according to the invention travels, for example, with the mechanical transmission 28 switched to the high-speed stage 42 and thereby comes to a mountain. This leads to a greater load on the internal combustion engine 20 and to a reduction in the transmission ratio of the hydrostatic transmission 26, regulated by the drive control 130.

The reduction in the ratio of the hydrostatic transmission and thus also the reduction in the feed current I for the proportional control valve 136 takes place until a minimum ratio U-min and a minimum feed current I-min have been reached for the proportional control valve 136. This value is also preferably set in the programmable memory 152 as a switch-back point. The tripping device 154 recognizes this switch-back point at a time TOZ and triggers a switching operation of the switching controller 150 with a switch-back signal. The shift control 150 very rapidly further reduces the transmission ratio U of the hydrostatic transmission 26 between the time TOZ and a subsequent time TIZ in order to relieve the connection between the shifting center 38 and the gearwheel 46. At the same time, the switching controller 150 outputs the control signal SAZ to the switching valve 58 at the time TOZ, which controls the hydraulic cylinder 56 in such a way that it brings the switching center 38 out of interaction and from the position S into the intermediate position Z out of the position S. This is also recognized by the monitoring element 60.

From the point in time TIZ at which the switching center 38 is in the intermediate position Z, the ratio of the hydrostatic transmission 26 is increased to a point in time T2Z, the increase taking place, for example, by a fixed value U _{vz which} is so large that that the switching center 38 and the gear wheel 44 approximately the same peripheral speed in the engagement area, that is to say in the present case have the same speed.

From the point in time T2Z, the shift control 150 keeps the transmission ratio of the hydrostatic transmission 26 essentially constant and at the same time, from the point in time T2Z, sends the signal SEZ to the switching valve 58, which leads to the hydraulic cylinder 56 switching the center 38 with the gearwheel 34 in Engagement and thus the switching center 38 moves from the Z position to the L position. This is in turn recognized by the monitoring device 60. From time T3Z, the control of the proportional control valve 136 is released again by the switching control 150 and the control is carried out again in accordance with the specifications of the driving control 130, in particular the load on the internal combustion engine 20.

In FIG. 6, the speed V of the municipal vehicle according to the invention is also shown by way of example, the speed V initially decreasing with the transmission of the hydrostatic transmission up to the time TOZ, and also decreasing further after the time T3Z.

The time between TOZ and T3Z is usually so short that approximately due to the inertia of the moving municipal vehicle, the speed in this period drops approximately the same or slightly more than before the time TOZ.

The shift control 150 according to the invention thus leads to an automatic shifting of the mechanical transmission 28 as a function of the transmission ratio of the hydrostatic transmission 26, which in turn is influenced by the load on the internal combustion engine 20.

In the second switching step, the exemplary embodiment described so far either provides for a reduction in the gear ratio of the hydrostatic transmission 26 by a value URH when shifting up, or an increase in the gear ratio by a value UVZ when shifting down, the two values in the programmable memory 152 can be predefined. This possibility is provided in particular when working with fixed upshift points U-max and downshift points U-min, since in this case it can be assumed that the value URH or UVZ is also constant and thus approximately the switching center 38 to the same Speed brings either the gear 46 or the gear 34.

This solution can be improved further in that, before the switching center 38 is brought into engagement with the gearwheel 46 or the gearwheel 34, the speed is adjusted by means of a conventional gear synchronization.

However, problems can arise due to different acceleration or braking of the municipal vehicle.

For this reason, a variant of the first exemplary embodiment, shown in FIGS. 7 and 8, provides that the mechanical transmission 28 is assigned a speed sensor 160, with which the shift control 150 is able to determine the speed of the drive shaft 36 of the mechanical transmission 28 to detect. At the same time, the shift control 150 is able to detect the speed of the output shaft 40 of the mechanical transmission 28 via the speed sensor 108.

In this case, the variation of the transmission ratio U of the hydrostatic transmission 26 does not take place during the second switching step by the constant value URH or UVZ, but the transmission ratio U is regulated according to the measured values of the sensors 160 and 108, so that the value URH 'and the value UVZ' each Measurements of the speeds of the input shaft 36 and the output shaft 40 of the mechanical transmission 28 result, however, the gear ratios of the slow speed stage 30 and the high speed stage 42 are stored in the programmable memory 152, from which, together with the speed of the drive shaft 36, the speeds of the gear wheels Determine 46 or 34 and have them set in relation to the speed of the switching center 38, detected by the speed sensor 108.

In this variant of the first embodiment, it is thus ensured that the peripheral speeds between the switching center 38 and the gear wheels 46 and 34 are identical in the engagement area, so that the switching center 38 can be brought into engagement with the gear wheels 46 and 34 without synchronization with certainty , Additional influences which affect the speed of the municipal vehicle and thus the speed of the output shaft 40 and the switching center 38 are automatically compensated for.

In a second exemplary embodiment, shown in FIG. 9, there is the possibility of triggering a switching operation with a trigger switch 162, this being possible independently of the switching points U-max and U-min. In this case, the shift control 150 operates in accordance with the variant of the first exemplary embodiment, that is to say with the speed sensor 160 and the speed sensor 108, so that in each case the shift center 38 and the gear wheels 46 and 34 are regulated to a constant peripheral speed in the engagement area. In this exemplary embodiment, the driver thus has the possibility of switching between the slow speed stage 30 and the fast speed stage 42, independently of the set switching points. In addition, the driver has the option of additionally using the function of the trigger device 154 via the trigger switch 162, that is to say switching over at the predetermined switching points U-max and U-min.

Otherwise, the second exemplary embodiment is identical to the first, so that the same reference numerals are used and full reference is made to the explanations for the first exemplary embodiment.

The municipal vehicle according to the invention can now be operated as follows.

After the internal combustion engine 20 is running, one of the programs P1 or P2 or P3 stored in the memory 134 can be called up by the process computer 132 of the drive control 130 via the program selection switch 86. Here, for example, a program Pl road trip is provided, which works as follows:

Program Pl road trip

In the road trip program, the operator of the municipal vehicle is to be allowed to drive on the road with it in the same way as with a conventional motor vehicle with automatic operation, that is to say the speed is to be variable as a function of the target speed setting of the internal combustion engine 20, wherein in addition, regardless of the target speed setting of the internal combustion engine 20, a clutch is to be simulated by means of the reset pedal 92, so that the municipal vehicle can be stopped by pressing the reset pedal 92. When the internal combustion engine 20 is running, the operator sets the fixed setting lever 90 to the maximum position and thus specifies the largest possible maximum parameter. The process computer 132 detects the set speed via the set speed setting sensor 144 and the process computer 132 controls the pivoting cradle of the hydraulic pump 22 via the proportional control valve 136, for example when the vehicle is at idle speed, so that the vehicle despite the fixed setting lever 90 and which is in the maximum position unactuated reset pedal 92 does not yet drive.

Furthermore, the driver has to set the direction of travel with the direction of travel preselection switch 138 before starting the journey by means of the travel direction selection lever 88, whereupon the delivery direction of the hydraulic pump 22 is determined.

By changing the target speed setting sensor 144 in the direction of the full throttle position, the municipal vehicle according to the invention now starts, the process computer 132 recognizing that the idling position has been exited and the pivoting cradle corresponding to the setting of the target speed setting sensor 144 from the idling position the hydraulic pump 22 and thus its delivery volume is adjusted via the proportional control valve, as follows:

An idling speed of the internal combustion engine 20 is assigned to the respective position of the target speed setting sensor 144 outside of the idle position. Starting from this idling speed, a pressure of the idling speed corresponding to the performance characteristic of the internal combustion engine 20 to a first nominal speed below the idling speed is permitted and aimed for, this pressure being stored in the form of a characteristic field in the "road travel" program. The process computer 132 now regulates the delivery volume of the hydraulic pump 22 so that the actual speed of the internal combustion engine 20 measured by the speed sensor 106 corresponds to the calculated first nominal speed, the maximum delivery volume being limited by the maximum parameter, specified by the actuating device 140 via the actuator 142 is, in particular if the reset pedal 92 or the fixed setting lever 90 are in an intermediate position between the rapid travel maximum position and the zero position.

The first nominal speed is preferably calculated in accordance with the data on the maximum output of the internal combustion engine 20, so that in the road travel program the internal combustion engine 20 outputs the maximum output at each speed selected via the setpoint speed setting sensor 144 and thus the maximum output for the Road trip is available.

In addition to the transmission ratio of the hydrostatic transmission 26, the shift control 150 is now used to select between the slow speed stage 30 and the fast speed stage 42 of the mechanical transmission 28, in the first exemplary embodiment corresponding to the predetermined upshift U-max and reverse switching points U-min as already explained in the above explanations on the function of the switching control 150. The municipal vehicle can thus be accelerated when driving on the road, for example at slow speed 30. When the upshift point U-max is reached, the speed changeover 42 is automatically switched over and the maximum speed V is set by setting the Desired speed setting encoder 144 is set, wherein the drive control 130 always selects the transmission ratio U of the hydrostatic transmission in such a way that the internal combustion engine 20 delivers its maximum power.

If, for example, the counter-torque acting on the driven wheels 16, 18 becomes so high in the high-speed stage 42 that the drive control 130 reduces the transmission ratio U of the hydrostatic transmission - as before, with maximum load on the internal combustion engine - to the switchback point U-min, the shift control 150 automatically switches from the high-speed stage 42 to the slow-speed stage 30 and thus creates the possibility, in turn, of increasing the transmission ratio U of the hydrostatic transmission 26 to such an extent that a further control range is available, so long until the maximum load on the internal combustion engine 20 can be continued at a constant speed V and thus also a constant transmission ratio U of the hydrostatic transmission 26.

In the second exemplary embodiment, in addition to an automatic switchover, triggered by the trigger device 154, there is also the possibility that the driver intervenes actively via the trigger switch 162 and either an automatic switchover from the slow speed stage 30 to the fast drive stage 42 or an automatic switchover triggers from the high speed stage 42 to the slow speed stage 30.

In addition, in a further variant, automatic switching can also be triggered via a more complex control in accordance with the driving programs to be selected. In addition to the "road trip" program, there is also the possibility of operating the vehicle according to the invention in the programs P2 "work with power take-off" and P3 "constant travel I or II".

These programs are described in detail in German patent application P 41 11 921.5.

In addition, in connection with the solution according to the invention, there is also the possibility in these programs of switching the mechanical transmission 28 to either the slow speed stage 30 or the high speed stage 42, depending on which of the two transmission stages for the respective program is as suitable as possible Load of the internal combustion engine is optimal.

Claims

P A T E N T A N S P R Ü C H E

Vehicle, comprising an internal combustion engine, a continuously variable transmission by means of an adjusting element and a mechanical transmission, which can be shifted into gear ratios by interacting gear wheels of one of several gear sets, characterized in that for shifting from a first set of gear wheels (38, 30; 38, 42) to a second set of gear wheels (38, 42; 38, 30) of the mechanical transmission (28), the respective gear wheels (38, 34; 38, 46) interact and not interact Bringing switching element (56) is provided that a Schalt¬ control (150) is provided which, when a switching signal is present, automatically the gear set (38, 30; 38, 42) by controlling the actuating element (136) and the switching element (56) changes that the switching control (150) controls the switching element (56) in a first switching step so that d ieses the first gear set (38, 30; 38, 42) interacts, in a second switching step controls the control element (136) so that the continuously variable transmission (26) adjusts the peripheral speed of the gear wheels (38, 46; 38, 34) of the second gear set (38 , 42; 38, 30) in the engagement area and in a third switching step controls the switching element (56) in such a way that it brings the second gear set (38, 42; 38, 30) into interaction.

2. Vehicle according to claim 1, characterized in that the shift control (150) controls the actuating element (136) so that this reduces the translation (U) of the continuously variable transmission (26) during the first switching step.

3. Vehicle according to claim 2, characterized in that the shift control (150) during the first Schalt¬ step reduces the translation (U) of the continuously variable transmission (26) in the sense of a slight braking of the vehicle.

4. Vehicle according to one of the preceding claims, characterized in that the shift control (150) controls the actuating element (136) so that the continuously variable transmission (26) keeps the translation (U) substantially constant during the third switching step.

5. Vehicle according to one of the preceding claims, characterized in that a triggering device (154) is provided for the switching signal, which detects a driving parameter (U) of the vehicle and when a switching value (U-min, U-max) of the Fahr¬ parameters triggers the switching signal.

6. Vehicle according to claim 5, characterized in that the driving parameter (U) is the translation (U) of the continuously variable transmission (26).

7. Vehicle according to one of the preceding claims, characterized in that an upshift signal or a Rückschalt¬ signal can be applied to the shift control (150).

8. Vehicle according to one of claims 5 to 7, characterized in that the triggering device (154) switching points for the upshift signal and the Rück¬ shift signal by setting an upshift value (U-max) and a downshift value (U-min) of the translation (U) of the continuously variable transmission (26) can be predetermined.

9. Vehicle according to one of claims 6 to 8, characterized in that the triggering device (154) detects a control signal of the control element (136) as a driving parameter.

10. Vehicle according to one of the preceding claims, characterized in that the shift control (150) for approximating the peripheral speed of the gear wheels (38, 46; 38, 34) of the second gear set (38, 42; 38, 30) the translation ( U) of the continuously variable transmission (26) is changed by a value (URH; UVZ) which can be predetermined by the shift control (150).

11. Vehicle according to claim 10, characterized in that the shift control (150) predetermined value (URH; UVZ) is fixed.

12. Vehicle according to claim 10 or 11, characterized gekenn¬ characterized in that the value (URH; UVZ) depends on the existing at the beginning of the first switching step translation (U) of the continuously variable transmission (26).

13. Vehicle according to one of claims 10 to 12, characterized in that the value (URH; UVZ) depends on the existing at the beginning of the first switching step ratio of the mechanical transmission (28).

14. Vehicle according to one of claims 1 to 10, characterized in that the switching control (150) detects the speed of the gear wheels (38, 46; 38, 34) of the second gear set (38, 42; 38, 30) and via the control element (136) regulates the translation (U) of the continuously variable transmission (26) in such a way that the gear wheels (38, 46; 38, 34) to be brought into interaction have approximately the same peripheral speeds in their area of engagement.

15. Vehicle according to claim 14, characterized in that a speed sensor (160, 108) is arranged on the drive side and output side of the mechanical transmission (28).

16. Vehicle according to claim 14 or 15, characterized gekenn¬ characterized in that the shift control (150), the speed ratio for the respective second gear set (38, 42; 38, 30) can be predetermined.

17. Vehicle according to one of the preceding claims, characterized in that the switching controller (150) comprises a process computer (132) and a programmable memory (152).

18. Vehicle according to one of claims 5 to 17, characterized in that the triggering device (154) comprises a process computer (132) and a programmable memory (152) and that in the memory (152) at least one switching value (U-max, U -min) is saved.

19. Vehicle according to one of the preceding claims, characterized in that a drive control (130) is provided for controlling the continuously variable transmission (26), which has a process computer

(132) and a programmable memory (134).

20. Vehicle according to claim 19, characterized in that the drive control (130) is connected to a position transmitter (142) of an actuating device (140) which detects the respective position of the actuating device and transmits a maximum parameter to the drive control (130) and in that the drive control (130) controls the gear ratio (U) of the continuously variable transmission (26) in accordance with a program (P1, P2, P3) stored in the memory (134) and the maximum parameter transmitted.

21. Vehicle according to one of the preceding claims, characterized in that the continuously variable transmission (26) is a hydrostatic transmission which has a hydraulic pump (22) driven by the internal combustion engine (20) and a hydraulic motor (22) driven by the hydraulic pump (22) 24) includes.