Drive system for a towing vehicle

Abstract

A drive system for a towing vehicle (10) pulling a towed powered device (12), the drive system comprising: a power generation unit (14) including a generator (16) for generating electrical energy; an electric drive motor (76) connected to a driven axle (78) of the towed device (12); a manually operable power distribution setting unit (54) via which a power split value is set by the operator, which determines the split of the electrical power between the towing vehicle (10) and the towed device (12); a vehicle speed sensor (57) for generating a vehicle speed signal; a power distribution unit (15) for controlling the distribution of electrical energy from the generator (16) to the drive motor (76) of the towed device (12); and a control unit (58) connected to the power distribution setting unit (54), the vehicle speed sensor (57), the power distribution unit (15), and an engine control unit (32), wherein the control unit (58) obtains an engine load factor from the engine control unit (32), a power split from the operator-controlled power distribution setting unit (54) and the vehicle speed sensor (57), wherein, in the event that the sensed engine load is greater than a load threshold and the vehicle speed is less than a speed threshold, the control unit (58) causes the power distribution unit (15) to distribute electrical power to the towing vehicle (10) and to the drive motor (76) of the towed device (12) as set by the power distribution setting unit (54);and wherein, in the event that a sensed engine load is greater than a load threshold and the vehicle speed is not less than the speed threshold, the control unit (58) causes the power distribution unit (15) to direct all electrical power to the towing vehicle (10);

Description

[0001] The present disclosure relates to a drive system for a towing vehicle that pulls a towed powered device.

[0002] A tractor pulling a scraper is an example of a towing vehicle pulling a towed piece of equipment. Earthmoving scrapers are heavy and often operate in soil conditions where putting power to the ground can be challenging. The weight carried by the scraper tires provides the potential to develop tractive effort to assist the towing vehicle in moving the machine. If this additional pulling power can be harnessed, the drawbar pull required by the tractor can be reduced during scraper loading and climbing steep grades. The operational advantage gained by employing a drawbar axle linked to a drive control system on the scraper can be significant. First, the system will develop better traction for the overall system, resulting in faster dump fills and the removal of more soil in less time.Second, there will be less wear on the tractor tires due to the reduction in wheel slip and drawbar load. Third, this reduction in maximum drawbar load allows ballast to be removed from the tractor and reduces parasitic losses due to rolling resistance of the entire tractor-scraper system. This will enable higher haul speeds and more productive operation, while ensuring a fuel economy advantage throughout the cycle. Finally, the system will increase equipment utilization by enabling operations in conditions where a normal tractor-scraper system would bog down.

[0003] Against this background, US 2010 / 0018728 A1 discloses a drive system for an earthmoving scraper, comprising a tractor section and a scraper section attached thereto. The tractor section comprises a drive source connected to a generator, which generates electrical power to operate one or more electric motors, by means of which front wheels arranged on the tractor section can be driven. Furthermore, the scraper section has hydraulic drive motors connected to rear wheels. These can be manually activated in the form of rear-wheel drive assistance. The rear-wheel drive assistance is designed to operate only at relatively low machine speeds, for example, below 9 mph. Compliance with this condition is monitored by sensors in an associated control unit.

[0004] A comparable drive system for an earthmoving scraper is also known from US 2010 / 0018727 A1.

[0005] The object of the present invention is to provide a drive system of the type mentioned at the outset which is improved with regard to rear-wheel drive support.

[0006] This object is achieved by a drive system for a towing vehicle having the features of patent claim 1.

[0007] According to the invention, a drive system for a towing vehicle towing a towed powered device is provided. The drive system includes a power generation unit on the towing vehicle, such as a diesel engine, which drives a generator for generating electrical power. An electric drive motor is connected to a driven axle of the towed device. A manually operable power distribution setting unit, via which a power split value is set by the operator, determines the split of the electrical power between the towing vehicle and the towed device. Further components include a vehicle speed sensor for generating a vehicle speed signal, a power distribution unit for controlling the distribution of electrical power from the generator to the drive motor of the towed device, and a control unit.The control unit is connected to the power distribution adjustment unit, the speed sensor, the power distribution unit, and an engine control unit, wherein the control unit obtains an engine load factor from the engine control unit, a power split from the operator-controlled power distribution adjustment unit, and the vehicle speed sensor. If the sensed engine load is greater than a load threshold and the vehicle speed is less than a speed threshold, the control unit causes the power distribution unit to distribute electrical power to the towing vehicle and to the drive motor of the towed device as set by the power distribution adjustment unit.In the event that a sensed engine load is greater than a load threshold and the vehicle speed is not less than the speed threshold, the control unit causes the power distribution unit to direct all electrical power to the towing vehicle.

[0008] In this way, it is possible to specify the power split to the tractor drive engine in a way that is adapted to the respective traction conditions.

[0009] Such a system can be used with many types of towed equipment, such as grain wagons, sludge tanks, tiller wagons, etc., where additional traction is needed.

[0010] The drive system for a towing vehicle according to the invention will be explained in more detail below with reference to the attached drawings. They show: Fig. 1 is a simplified schematic representation of a drive system embodying the invention, Fig. Figure 2 is a simplified schematic electrical representation of the system of Fig. 1, and Fig. 3 is a flowchart of a process executed by the power control unit of Fig. 2 executed algorithm.

[0011] With reference to Fig. 1 and Fig. 2, a drive system is provided for a towing vehicle or tractor 10 pulling an implement 12. The towing vehicle 10 may be an agricultural tractor. The towed implement 12 may be a tractor scraper. The tractor 10 includes an engine 14, such as a diesel engine, that drives the tractor axles and an electric generator 16. The generator 16 provides electrical power to power electronics units 15. The power electronics units 15 distribute electrical power to drive motor units 24 and 76 that drive respective vehicle wheels 25 and 79. Alternatively, the tractor 10 may have an engine that drives a generator that feeds electric wheel motors (not shown) that provide power to driven wheels of the tractor.Alternatively, instead of a diesel engine driving a generator, the tractor 10 may include a known fuel cell (not shown) and power electronics for generating electrical energy. Consequently, this would require a tractor 10 with some type of electric drivetrain. This would typically be a diesel-electric system somewhat similar to a locomotive. The prime mover could be any type of internal combustion engine or fuel cell of appropriate capacity, and the electrical energy would typically be used to drive the drive axles of the tractor 10.

[0012] The towed device 12 includes an auxiliary electric or device drive motor 76 that receives electrical energy from the power electronics unit 15. The auxiliary motor 76 drives an axle 78, which drives wheels 79 of the towed device 12.

[0013] With reference to Fig. 2, the electric generator 16 is connected by 3-phase wiring 17 to a power electronics unit 15, which includes electrical power inverters 18, 20, and 22. The inverter 18 is connected to the inverter 20 and the inverter 22 by a DC bus bar 19. The inverter 20 is operatively connected by 3-phase wiring 21 to a drive motor 24, which is coupled to a transmission 26, such as a two-speed transmission, drivingly coupled to driven wheels 25 of the towing vehicle 10. The inverter 22 is connected by 3-phase wiring 23 to a 3-phase connector 28, which electrically connects the power electronics of the towing vehicle 10 to the implement drive motor of the towed implement 12.

[0014] Control wiring 30 connects inverters 18 to 22 to each other, a transmission control unit 34, and the power control unit 58. Control wiring 36 connects the transmission control unit 34 to the two-speed transmission 26 and to a control connector 28, which electrically connects the control electronics of the towing vehicle 10 to the control electronics of the towed device 12. Control wiring 40 connects the inverter 22 to the control connector 38. Control wiring 42 connects the inverter 20 to the generator 16. Control wiring 44 connects the inverter 18 to the drive motor 24.

[0015] An interlock wiring 46 connects the inverter 20 to the generator 16. An interlock wiring 48 connects the inverter 18 to the motor 24. An interlock wiring 50 connects the inverter 22 to the connector 28.

[0016] Ground wiring 52 connects the 3-phase connector 28 to ground points of equal potential. The power control unit 58 obtains the engine load factor from the engine control unit 32 and the power distribution from the operator-controlled power distribution adjustment unit 54 and the vehicle speed sensor 57.

[0017] Referring now to the towed equipment section of Fig. 2, the 3-phase connector 28 is connected to an interface box 66 via ground wiring 52, interlock wiring 62, and 3-phase AC wiring 64. The interface box 66 is connected to a high-current connector 72 via 3-phase AC wiring 68 and interlock wiring 70. The connector 72 is connected to the towed device drive motor 76 via 3-phase AC wiring 74, which is drivingly connected to the driven axle 78 of the towed device 12.

[0018] A one-way clutch 77 is coupled between the drive motor 76 and the driven axle 78. Because the towed implement axle 78 has such a high gear ratio, once the vehicle reaches higher speeds (approximately 11 mph), the towed implement axle 78 must be disengaged from the electric motor 76 to prevent engine damage from overspeeding. The one-way clutch 77 is used to accomplish this and will automatically disengage the electric motor 76 from the towed implement axle 78.

[0019] The control connector 38 is connected to the drive motor 76 and to the axle 78 of the towed implement by control lines 80 and 82 and a connector 84. The control connector 38 is also connected by the control line 80 to sensors of the towed implement and the vehicle, which sense parameters such as electric motor temperatures, electric motor / generator speeds, implement wheel speeds, implement wheel slip (uses radar / GPS and axle speeds for calculation), and ground speed.

[0020] The power control unit 58 performs a Fig. 3. The conversion of this flowchart into a standard language for implementing the algorithm described by the flowchart in a digital computer or microprocessor will be obvious to one of ordinary skill in the art.

[0021] In step 102, the PMU 58 obtains a power split value, set by the operator, which determines the split of electrical power between the tractor 10 and the towed implement 12. The operator preferably considers site conditions and determines, based on experience, how much electrical power should be provided to the towed implement 12. Typically, the looser or more slippery the condition (such as mud or sand), the more power would be shifted to the towed implement to help improve overall traction. On clay soil, where traction is good, less power would need to be shifted from the tractor axles to the towed implement because the tractor would experience less wheel slippage. Inputting the power split is performed by the power split setting unit 54, which may be a touchscreen or a rotary dial.

[0022] In step 104, the PMU 58 monitors ground speed, engine load, and / or tractor load and determines when to generate and distribute electrical power. If the engine load and / or tractor load exceed a stored lower threshold, then electrical power will begin to be generated, and the power may be shared between the tractor 10 and the towed implement 12 if a speed parameter is met. The electrical power will continue to increase, and if an upper threshold is exceeded, then full electrical power is commanded and is capable of driving either the tractor axle, the scraper axle, or any distribution in between, as selected by the operator.

[0023] Step 106 directs control to step 108 if the sensed groundspeed is less than a stored threshold. Step 106 directs control to step 110 if the sensed groundspeed is not less than a stored threshold.

[0024] Step 108 distributes electrical power to the tractor drive motor 24 and to the towed implement drive motor 76 according to the power split set by the operator using the power split setting unit 54. Thus, if the ground speed is not exceeded, the system will split the electrical power between the tractor 10 and the towed implement 12 as commanded by the operator. Step 108 then directs the algorithm to step 114. Step 110 distributes all electrical power to the tractor drive motor 24. Thus, steps 106 through 110 operate to monitor ground speed from tractor axle sensors, radar, or by GPS, and if a threshold speed has been reached, all electrical power will be directed to the tractor 10.Otherwise, the electrical power will be shared between the towed device 12 and the tractor 10 as specified by the operator.

[0025] Step 112 continues to monitor ground speed, train load, and engine load and returns control to step 104.

[0026] Step 114 continues to monitor ground speed, train load, and engine load and returns control to step 104.

[0027] The system provides better traction, resulting in faster skip filling and more earth moved in less time if the towed equipment is a scraper. There is also less wear on the tractor tires and driveline due to less wheel slip and reduced drawbar load. Furthermore, the operator will experience increased equipment utilization in less than ideal ground conditions because the equipment can be operated when it would not normally be used.

Claims

[1] A drive system for a towing vehicle (10) pulling a towed powered device (12), the drive system comprising: a power generation unit (14) including a generator (16) for generating electrical energy; an electric drive motor (76) connected to a driven axle (78) of the towed device (12); a manually operable power distribution setting unit (54) via which a power split value is set by the operator, which determines the split of the electrical power between the towing vehicle (10) and the towed device (12); a vehicle speed sensor (57) for generating a vehicle speed signal; a power distribution unit (15) for controlling the distribution of electrical energy from the generator (16) to the drive motor (76) of the towed device (12); and a control unit (58) connected to the power distribution setting unit (54), the vehicle speed sensor (57), the power distribution unit (15), and an engine control unit (32), wherein the control unit (58) obtains an engine load factor from the engine control unit (32), a power split from the operator-controlled power distribution setting unit (54) and the vehicle speed sensor (57), wherein, in the event that the sensed engine load is greater than a load threshold and the vehicle speed is less than a speed threshold, the control unit (58) causes the power distribution unit (15) to distribute electrical power to the towing vehicle (10) and to the drive motor (76) of the towed device (12) as set by the power distribution setting unit (54);and wherein, in the event that a sensed engine load is greater than a load threshold and the vehicle speed is not less than the speed threshold, the control unit (58) causes the power distribution unit (15) to direct all electrical power to the towing vehicle (10); [2] Drive system according to claim 1, characterized by in that a one-way clutch (77) is coupled between the electric drive motor (76) of the towed device (12) and the driven axle (78) of the towed device (12), the clutch (77) disengaging to prevent overspeed of the electric drive motor (76) of the towed device (12) if the vehicle speed exceeds a set speed level. [3] Drive system according to claim 1, characterized by that the towing vehicle (10) comprises a tractor; and the towed device (12) comprises a scraper.

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