Agricultural work machine with refrigeration unit

Description

[0001] The present invention relates to an agricultural machine such as a tractor, combine harvester, forage harvester, or the like. Such machines conventionally have an internal combustion engine as their main engine, for driving movement and for powering attached or integrated implements, and the waste heat from this engine must be dissipated to the environment.

[0002] German patent DE 35 27 54 C describes a fan for a motor vehicle that can be driven by both an internal combustion engine and a dynamo that can be operated as an electric motor. When the internal combustion engine is running, it simultaneously drives both the fan and the dynamo to charge a battery. A freewheel clutch allows the electric motor to drive the fan in one direction of rotation when the internal combustion engine is off. The dynamo cannot be stopped while the internal combustion engine is running, so frictional losses in the dynamo reduce the energy efficiency of the overall system consisting of the internal combustion engine, dynamo, and battery.

[0003] DE 42 28 586 A1 discloses a cooling system for an engine, in particular an agricultural machine, in which a fan can be driven by an electric motor in different directions of rotation. Since the drive energy for the fan must first be obtained by converting combustion energy into electrical energy, the efficiency of the fan with respect to the fuel required for its operation can be improved.

[0004] DE 10 2010 011 859 A1 describes an agricultural working machine according to the preamble of claim 1.

[0005] The object of the present invention is to provide an agricultural machine that can be cooled effectively and with low energy consumption.

[0006] The problem is solved by an agricultural machine according to claim 1, in that an agricultural machine comprising a main engine, an electric machine, at least one fan, a first drive train for driving the fan by the main engine and a second drive train for coupling the fan to the electric machine provides a coupling for disconnecting and / or connecting the drive trains, and the fan can be driven alternatively via the first or second drive train or simultaneously via both drive trains.

[0007] The coupling can be switched between a closed position, in which a motor-side connection and a fan-side connection of the coupling are rotationally fixed, and a first open position, in which the fan-side connection can be rotated in opposite directions relative to the motor-side connection.

[0008] For this purpose, the clutch, or at least parts of it, can be located in the first drive train in order to interrupt it in the open position.

[0009] In the closed position, this coupling allows the fan to be driven solely by the main motor, without any loss of efficiency due to prior energy conversion. In this position, the electric machine can operate as a generator. While it is also possible to operate it as a motor assisting the fan, this is generally of little interest, as the electric machine's power output is only a small fraction of that of the main motor.

[0010] In the open position, the electric machine can operate the fan even when the main motor is switched off, for example to cool it further after it has been switched off.

[0011] In a second open position of the coupling, a fan-side connection and a machine-side connection can be rotatable relative to each other. These connections are preferably non-rotatably connected in the first open position.

[0012] A control unit is provided for the electric machine, allowing the direction of rotation of the motor-operated electric machine to be reversed. By operating the fan in different directions, it is possible to loosen and, if necessary, remove dirt that accumulates on the cooling air path during operation.

[0013] The control unit can include a switch which, in a first switching position, connects a first battery terminal to a first supply terminal of the electric machine and a second battery terminal to a second supply terminal of the electric machine, and in a second switching position, connects the first battery terminal to the second supply terminal and the second battery terminal to the first supply terminal.

[0014] The reversal of direction is achieved by connecting the electric machine to an inverter with switches arranged in several parallel bridge circuits and by configuring the control unit to control the switches in a first sequence and a second sequence inverse to the first sequence.

[0015] An air filter should be provided, and the fan positioned to drive an airflow through the filter, thus keeping dirt away from the machine's surfaces requiring cooling. Dirt that accumulates on the air filter during fan operation in its main direction of rotation and is held against the filter by the airflow can be pushed away and removed by reversing the airflow direction. This prevents the air filter from becoming clogged and resulting in insufficient cooling or increased energy consumption for cooling.

[0016] If a cooling air duct runs from the air filter, through the fan, to a component requiring cooling, a dust outlet can be provided on the upstream side of the air filter to remove dust dislodged from the filter by a reversal of the airflow direction. By expelling the dust from the cooling air duct, re-intake when the airflow returns to its original direction of rotation can be prevented.

[0017] The control unit can be coupled to the clutch to operate the electric machine as a generator when the clutch is closed and as a motor when it is open.

[0018] Furthermore, the control unit can be configured to move the clutch into the open position when the main motor is switched off and to operate the electric machine as a motor at least temporarily, in particular until the temperature measured at a suitable measuring point of the agricultural machine falls below a limit value.

[0019] The control unit is further configured to open the clutch when a limit temperature is exceeded and to operate the electric machine as a motor in such a way that the speed of the fan-side connection of the clutch is higher than the speed of the motor-side connection. Thus, when necessary, a higher speed and consequently a higher cooling capacity is achieved by decoupling the fan from the main motor than if the fan were driven directly by the main motor via the clutch.

[0020] Furthermore, the control unit is also designed to move the clutch into the open position and operate the electric machine with a direction of rotation opposite to the main motor if the ratio of measured pressure drop to fan speed exceeds a limit value, in order to remove deposits from the air filter and consequently enable more efficient cooling.

[0021] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1 a schematic representation of an agricultural work machine and Fig. 2 a fan and its connections to the main motor and the electrical machine of the working machine Fig. 1 . Fig. 3 a detail from the fan's drive system according to a second embodiment.

[0022] Fig. 1 Figure 1 schematically shows, as an example of an agricultural machine according to the invention, a tractor of a known external appearance, with a chassis 1 on which front wheels 2 and rear wheels 3 are mounted, an engine housing 4 which is mounted on the chassis and flanked on both sides by upper areas of the two front wheels 2, and a driver's cab 5 which is placed behind the engine housing 4 in the direction of travel.

[0023] The engine housing 4 contains a main engine 6, typically a diesel engine, and a fan unit 9. The fan unit 9 comprises, in a manner known per se, a radiator 10 through which cooling water from the main engine 6 flows, and a fan assembly 11, which includes one or more fans for driving an airflow through the radiator 10. A particulate filter 12 is located upstream of the radiator 10.

[0024] The fan unit can be arranged in a known manner in an upright orientation in front of the main engine 6 to draw in fresh air via an inlet on the front of the engine housing 4; in the case shown here, the fan unit 9 is installed in a substantially horizontal orientation, i.e., of its three dimensions in mutually orthogonal directions, the two longest run substantially horizontally, and fresh air reaches the fan unit 9 via air inlet openings 13 in a cover 14 of the engine housing 4. Thus, there is space below the fan unit 9 for other components such as an exhaust aftertreatment unit 7, to which the exhaust gases of the main engine 6 are fed in order to remove pollutants such as soot or nitrogen oxides, a fuel tank 8, or an actuator for raising a working tool mounted at the front of the tractor (not shown in the figure).

[0025] Fig. 2 Figure 1 schematically shows the fan assembly 11 and its drive. Like the cooler 10, the fan assembly 11 has the shape of a flat cuboid extending between the cooler 10 and the particle filter 12, such that an air inlet surface of the fan assembly 11 faces the particle filter 12 and an air outlet surface faces the cooler 10. A single axial fan of a known design can fill the entire cross-section of the fan assembly 11; however, an arrangement of several axial fans side by side is preferred, e.g., a matrix arrangement with 2x3 axial fans 15, in order to form a fan assembly 11 in which the longest and second-longest dimensions differ. The axes of rotation 16 of the axial fans 15 are each oriented in the direction of the shortest dimension of the fan assembly 11 in order to convey air through the fan assembly 11 in the direction of this shortest dimension.

[0026] The axial fans 15 are coupled to one another, e.g. by a belt drive 17, so that they can be driven via a common shaft 18. A fan-side section 18a of the shaft 18 is separated from a motor-side section 18b by a coupling 19. The coupling 19 comprises, in a manner known per se, two disks 19a, 19b, which are axially adjustable between a closed position, in which they are in torque-locked contact with each other, and an open position, in which they are freely rotatable relative to each other in any direction, by means of an actuator 20.

[0027] The fan-side disc 19a is simultaneously a pulley of a belt drive 21, which connects the fans 15 to an electric machine 22.

[0028] The motor-side section 18b is coupled to the main motor 6 via a further belt drive 23.

[0029] Instead of the belt drives 21, 23, any other transmissions capable of transmitting torque in both directions can be used.

[0030] The rotation axes 16 of the axial fans 15 are located in the Fig. 1 The fan unit 9 shown is not parallel to an output shaft 24 of the main motor 6. In order to nevertheless be able to mechanically couple the axial fans 13 to the output shaft 24, a cardan joint 25 can be provided between this and the belt drive 23 or in the shaft 18.

[0031] The electric machine can be a simple DC motor whose direction of rotation can be reversed by selectively connecting its two terminals directly or crosswise to the terminals of a battery via a switch. Fig. 2 Figure 22 shows a three-phase electric machine connected to the battery 26 via an inverter 27. The inverter 27 comprises, in a manner known per se, three bridges connected in parallel to each other to the terminals of the battery 26, each with two switches 28, which can be controlled by a driver circuit 29 in a first sequence to drive the machine 22 in a forward direction or in a reverse sequence to drive the machine 22 in a reverse direction.

[0032] The inverter 27 and the driver circuit 29 are parts of a control unit 30, which is connected to a temperature sensor 31 and a pressure sensor 32 for estimating a pressure drop along the path of the cooling air through the motor housing 4. The pressure sensor 32 can, in particular, be a differential pressure sensor arranged on the fan assembly 11 to detect the pressure difference between the upstream and downstream sides of the fan assembly 11 or its particle filter 12. The control unit 30 is connected to the actuator 20 to open and close the coupling 19.

[0033] The control unit 30 supports the operating modes described below: a normal operating mode in which the clutch 19 is closed, so that the main motor 6 drives the axial fans 15 and the electric machine 22 in a forward direction of rotation, so that the axial fans 15 draw fresh air through the air inlet openings 13 into the motor housing 4.In this operating mode, the electric machine 22 can run passively, depending on the charge level of the battery 26, or be driven by the inverter 27 as a generator; a low-power mode in which the clutch 17 is open and the electric machine 22 operates at low power or is switched off, so that the axial fans 15 rotate forward at a lower speed than they would at the same time with the clutch 19 closed and driven directly by the main motor 6; a high-power mode in which the clutch 19 is open and the electric machine 22 operates at high power to drive the axial fans 15 forward at a higher speed than they would at the same time with the clutch 19 closed; a reverse operating mode in which the clutch 19 is open and the electric machine 22 operates at high power in reverse to drive an airflow in the opposite direction through the fan assembly 11.

[0034] The low-power mode is selected when the temperature detected by temperature sensor 31 falls below a lower threshold. This allows the main motor 6 to be brought up to operating temperature quickly after a cold start; it also reduces energy consumption for cooling, for example when the agricultural machine is moving quickly on the road with the main motor 6 operating at low power.

[0035] The high-performance mode is selected when the temperature detected by temperature sensor 31 exceeds an upper threshold, meaning the cooling capacity available in normal operating mode is no longer sufficient to adequately cool the main motor 6. Additionally, the high-performance mode can be selected if the machine needs to be cooled down after the main motor 6 has been switched off.

[0036] The reverse operating mode is activated whenever the ratio of measured pressure drop to speed of the axial fans 15 exceeds a limit value.

[0037] Dirt that has accumulated on the upstream side of the particulate filter 12 in one of the forward operating modes is pushed away from the particulate filter 12 again in reverse operating mode and could fall to the ground if the particulate filter is installed vertically. In the Fig. 1 Due to the inclined installation position of the particulate filter shown, the lifted dirt is placed in a state of suspension, in which it slides downwards following the inclination of the particulate filter, passes its front lower edge and finally leaves the engine housing 4 via an outlet 33 in the form of a gap between the front wall and the foremost unit 8.

[0038] Fig. 3 shows a section of the drive trains that power the fan according to a second embodiment. Components already mentioned in relation to Fig. 1 The components described above correspond to those described above, bear the same reference numerals, and are not described again. A coupling 34 here has, as a fan-side connection 34b, a slider fixed on the shaft 18 and axially displaceable by the actuator 20. A motor-side and a machine-side connection are each formed by a pulley 34a of the belt drive 23 and 34c of the belt drive 21, respectively. If the slider 34b does not engage with the pulleys, as in Fig. 3 As shown for pulley 34c, these are freely rotatable about the shaft 18. Toothed teeth on the circumference of the slider 34b and in the recesses of the pulleys 34a, 34c receiving the slider 34b couple the pulleys to the shaft in a rotationally fixed manner, as shown in Fig. 3 shown for pulley 34a.

[0039] In the position of the glider shown, the fans 15 are driven by the main motor 6; the electric machine can remain stationary. This prevents the main motor 6 from being loaded by the electric machine 22 when the control unit 30 assesses the charge level of the battery 26 as sufficient.

[0040] To operate the electric machine 22 as a generator, to drive the fans 15 jointly with the main motor 6 and the electric machine 22, or to prepare for a transition to purely electric drive of the fans 15, the control unit 30, with the aid of the actuator, moves the slider 34b one step towards the pulley 34c. This causes the slider 34b to engage with the pulley 34c, and the engagement with the pulley 34c continues. The coupling 34 is now closed in both directions, and the main motor 6, fans 15, and electric machine 22 are rotationally fixed to one another.

[0041] When the slider 34b is moved one step further towards pulley 34c, it loses engagement with pulley 34a. This interrupts the first drive train between the main motor 6 and the fans 15, and the latter can then only be driven by the electric machine 22. As with reference to Fig. 2 As described, the fans 15 can now be operated faster than the speed of the main motor, slower or even with reversed rotation as required. Reference symbol list

[0042] 1 Chassis 2 Front wheel 3 Rear wheel 4 Engine housing 5 Driver's cab 6 Drive motor 7 Auxiliary unit (exhaust aftertreatment unit) 8 Auxiliary unit (fuel tank) 9 Fan unit 10 Radiator 11 Fan assembly 12 Particulate filter 13 Air intake opening 14 Ceiling 15 Axial fan 16 Shaft of rotation 17 Belt drive 18 Shaft 18a Fan-side section 18b Engine-side section 19 Clutch 19a Disc 19b Disc 20 Actuator 21 Belt drive 22 Electric machine 23 Belt drive 24 Output shaft 25 Universal joint 26 Battery 27 Inverter 28 Switch 29 Driver circuit 30 Control unit 31 Temperature sensor 32 Pressure sensor 33 Outlet

Claims

1. An agricultural working machine with a main motor (6), an electric machine (22), at least one fan (15), a first drive train for driving the fan (15) by the main motor (6) and a second drive train for coupling the fan (15) to the electric machine (22), wherein a clutch (19) is provided for disconnecting and / or connecting the drive trains, and the fan (15) can be driven via the first drive train or alternatively via the second drive train or via both drive trains at the same time, wherein a control unit (30) is provided, by means of which the direction of rotation of the electric machine (22) operated as a motor can be reversed, wherein the electric machine (22) is connected to an inverter (27) with switches (28) disposed in a plurality of mutually parallel bridge circuits, wherein the control unit (30) is configured to control the switches (28) in a first sequence and in a second sequence which is reversed with respect to the first sequence, characterized in that the inverter (27) and a driver circuit (29) are parts of the control unit (30) which is connected to a temperature sensor (31) and a pressure sensor (32) in order to evaluate a pressure drop along the path of the cooling air through the motor housing (4), wherein the control unit (30) is configured to control the clutch (19) and the electric machine (22) as a function of information from the temperature sensor (31) and the pressure sensor (32) in order to operate the fan (15), wherein the control unit (30) is configured, when a temperature limit is exceeded, to move the clutch (19) into the open position and to operate the electric machine (22) as a motor in a manner such that the speed of the fan-side connection (19a) of the clutch (19) is higher than the speed of the motor-side connection (19b), wherein the control unit (30) is configured, when the relationship of the measured pressure drop to the speed of the fan (15) exceeds a limiting value, to move the clutch (19) into the open position and to operate the electric machine (22) as a motor such that the fan (15) rotates in the direction of rotation which is opposite to the direction of rotation when driven by the main motor (6).

2. The agricultural working machine according to claim 1, characterized in that the clutch (19) can be switched between a closed position, in which a motor-side connection (19b) and a fan-side connection (19a) of the clutch (19) are coupled in a manner which is fixed against rotation, and a first open position in which the fan-side connection (19a) can be rotated in opposite directions of rotation relative to the motor-side connection (19b).

3. The agricultural working machine according to claim 1 or claim 2, characterized in that in a second open position of the clutch, a fan-side connection (19a) of the clutch (19) and a machine-side connection (19c) are rotatable with respect to each other.

4. The agricultural working machine according to one of the preceding claims, characterized in that the fan (15) is disposed to drive a flow of air through an air filter (12).

5. The agricultural working machine according to claim 5, characterized in that a cooling air duct extends from the air filter (12) via the fan (15) and to an assembly to be cooled and a dust outlet (33) is provided on the cooling air duct on an upstream side of the air filter (12).

6. The agricultural working machine according to one of the preceding claims, characterized in that the control unit (30) is configured to operate the electric machine (22) as a generator in the closed position of the clutch (19) and as a motor in the open position.

7. The agricultural working machine according to one of the preceding claims, characterized in that the control unit (30) is configured to move the clutch (19) into the open position and to operate the electric machine (22) as a motor when the main motor (6) is switched off.