SE521540C2 - Power units for motor vehicles - Google Patents

Abstract

Drive unit for motor vehicles, comprising an internal combustion engine (1) and a unsynchronised stepped automated gearbox (9) connected to the engine via a clutch (3). The clutch and the gearbox are controlled by an electronic control unit (45), which communicates with an engine control unit (48) to which there are fed signals representing the selected gear from a gear selector (46) and signals representing various engine and vehicle data. The engine control unit is disposed, when the synchronization with the engine when shifting demands a lower engine speed than the engine idle speed determined by the engine control unit for the selected gear, to steer the engine speed to a lower rpm than idle rpm. The transmission control unit is disposed to engage the selected gear when the engine speed has reached a speed lower than idle speed, which is suitable for engaging the selected gear.

Description

To lower fuel consumption. In a gearbox consisting of an unsynchronized step-shifted base gearbox and a range gearbox, the absence of synchronizations contributes to further reducing the cost. The absence of synchronizing means makes it possible to make the gearbox shorter or alternatively to make the gears wider with a given length than in a synchronized gearbox with a corresponding length in order thereby enabling the transmission of higher torques.

In such a gearbox, the shifting takes place unlike in a planetary automatic gearbox during a power failure. This is one reason why, if the wagon load and road conditions so allow, when shifting at least on the lower gears, skip some gears, for example go directly from one to three or even to four gears. The problem, however, is that the engine control unit controls the engine speed to a minimum speed, which is the idle speed, typically about 600 rpm. The risk is then that if fl your gear steps are skipped over the selected gear, a lower speed than the idle speed is required to synchronize the engine speed with the speed of the input shaft, which is of course directly dependent on the carriage speed. Especially when shifting in reverse, there is a great risk that the carriage speed and thus the speed of the gearbox input shaft during the power failure will have time to drop to a speed below the idle speed, so that it is not possible to load the selected gear but a lower gear must instead selected.

The purpose of the present invention is to solve the problems described above and make it possible, for example from the start of the vehicle and during acceleration up to the selected cruising speed, to reach the selected cruising speed with fewer numbers of shifts than has hitherto been possible, thereby achieving better comfort and higher performance.

This is achieved according to the invention in that the motor control unit is arranged to - when the synchronization with the motor when shifting requires lower motor speed than the idle speed determined by the motor control unit for the selected gear - control the motor speed at a speed lower than the idle speed and that the transmission control unit is 540 3 arranged to be engaged in the selected gear, when the engine speed has reached a speed synchronous with the input shaft speed below the idle speed.

By enabling control of the engine speed to a speed lower than the idle speed, not only can shifting up during skipping gears take place, but also shifting up to a new higher gear can take place earlier than if the lowest speed is the idle speed. In addition, the safety margin against changes in the vehicle's surroundings (travel resistance, road slope) can be increased when shifting up if the engine is allowed to be steered at a lower speed than the idle speed. This means that switching can take place as under normal conditions, despite the fact that input data could be uncertain.

The invention is described in more detail with reference to exemplary embodiments shown in the accompanying drawings, in which fi g. 1 shows a schematic representation of an embodiment of a drive unit according to the invention, fi g. 2 clutch and gearbox in fi g. 1 on an enlarged scale, fi g. 3 is a diagram of the engine speed and the input speed of the gearbox as a function of the time when shifting up a steep uphill slope, fi g. 4 a corresponding diagram for upshifting on flat ground and fi g. 5 is a diagram illustrating the required upshift speeds to end up at idle speed after shifting for four gears.

I fi g. 1, 1 denotes a six-cylinder internal combustion engine, for example a diesel engine, the crankshaft 2 of which is connected to a single-disc dry single-clutch clutch generally designated 3, which is enclosed in a clutch housing 4. Instead of a single-disc disc clutch, a two-disc clutch can be used. The crankshaft 2 is non-rotatably connected to the coupling housing 5 of the clutch 3, while its lamella disc 6 is non-rotatably connected to an input shaft 7 (fi g. 2), which is rotatably mounted in the housing 8 of a gearbox generally designated 9. In the housing 8, a main shaft 10 (fi g. 2) and an intermediate shaft 11 (fi g. 2) are rotatably mounted. As most clearly shown in Fig. 2, a gear 12 is rotatably mounted on the input shaft 7 and lockable on the shaft by means of a coupling sleeve 13 provided with synchronizing means, which is rotatably but axially displaceably mounted on a the hub 14 is rotatably connected to the input shaft 14. By means of the coupling sleeve 13, a gear 15 rotatably mounted on the main shaft 10 is also lockable relative to the input shaft 7. The gears 12 and 15 engage with gears 16 and 16, respectively. 17, which are non-rotatably connected to the intermediate shaft 11. On the intermediate shaft 11, further gears 18, 19 and 20 are rotatably arranged, which engage with gears 21, 22 and 22, respectively, rotatably mounted on the main shaft 10. 23, which are lockable on the main shaft by means of coupling sleeves 24 resp. 25, which in the exemplary embodiment shown do not have synchronizing devices. On the main shaft 10, a further gear 28 is rotatably mounted and engages with an intermediate gear 30 rotatably mounted on a separate shaft 29, which in turn engages with the intermediate shaft gear 20. The gear 28 is lockable on its shaft by means of a coupling sleeve 26.

The gear pairs 12, 16 and 15, 17 and the clutch sleeve 13 form a split gear with a low gear stage LS and a high gear stage HS. The pair of gears 15, 17 together with the pair of gears 21, 18, 22, 19, 23, 20 and 28, 30 also form a basic gearbox with four forward gears and a reverse gear. On the output end of the main shaft 10, a gear 31 is arranged rotatably, which forms the sun gear in a planetary type gearbox designated 32, whose planet gear carrier 33 is rotatably connected to a shaft 34, which forms the output shaft of the gearbox. The planetary gear 35 of the range gear 32 engages with a ring gear 36, which by means of a coupling sleeve 37 is lockable relative to the gearbox housing 8 for low range LR and relative to the planet gear carrier 33 for high range HR. The coupling sleeve 37 also has a neutral position NR lying between the gear positions LR and HR, in which the output shaft 34 is disengaged from the main shaft 10.

The coupling sleeves 13, 24, 25, 26 and 37 are displaceable as the arrows show in fi g. 2, whereby the shift steps shown in connection with the arrows are obtained. The displacement is achieved with fi g. 2 schematically indicated servos 40, 41, 42, 43 and 44, which may be pneumatically actuated piston-cylinder devices of the type used in a gearbox of the type described above, which is marketed under the name Geartronic ®. The servo unit is controlled by an electronic transmission control unit 45 (fi g. 1), comprising a microcomputer, depending on signals input into the control unit representing various engine and vehicle data, which include at least engine speed, vehicle speed, clutch and accelerator pedal position and, where applicable, engine brake on, when an electronic gear selector 46 connected to the control unit 45 is in its automatic position. When the selector is in the position for manual shifting, the shift takes place at the driver's command via the gear selector 46. The transmission control unit 45 communicates with an engine control unit 48 and together with it also controls the fuel injection, ie the engine speed, depending on the accelerator pedal position and the air supply to a pneumatic piston-cylinder device 47, by means of which the coupling 3 is engaged and disengaged.

The transmission control unit 45 is programmed in a known manner so that it keeps the clutch 3 engaged when the vehicle is stationary and the gear selector 46 is in the neutral position.

This means that the motor drives the input shaft 7 and thus also the intermediate shaft, while the output shaft 34 is disengaged. Any attachments driven by the intermediate shaft, such as an oil pump for gearbox lubrication, are operated in this position. The control unit 45 is further programmed to, when the vehicle is stationary and the gear selector fl is moved from the neutral position to a gear position, either to a position for automatic transmission or to a position with the starter selected by the driver, first disengage the clutch 3, then brake the intermediate shaft ll to stop with using it in fi g. 2, which may be a per se known brake device controlled by the control unit 45.

With the intermediate shaft 11 braked to a stop or in any case at least almost to a stop, the control unit 45 now initiates shifting in the base gearbox to a starting gear, which is given by the automatic or by the driver selected total gear. When the driver after acceleration of the selected starting gear, for example one gear, gives gas, the accelerator pedal functions as a reverse clutch pedal, which via the transmission control unit gradually increases the clutch engagement with increasing throttle. 10 15 20 25 521 540 If the next gear selected - either directly by the driver or by the automatic system depending on a gear selection strategy stored in the transmission control unit 45, which can take into account what the vehicle's surroundings look like a bit into the future - is two or three steps higher than the starting gear, the situation may occur that the speed of the input shaft of the gearbox, which is directly dependent on the speed of the vehicle, requires a lower speed than the idle speed for synchronization with the engine. The same can occur when shifting to the nearest higher gear, if the shifting takes place on a steep uphill slope. In the diagram in fi g. 3 illustrates this situation when shifting on a steep uphill slope, where the vehicle loses so much speed from the time the shift is initiated until the engine speed and the speed of the gearbox input shaft (vehicle speed) are synchronous that this speed falls below the idle speed. By programming the motor control unit 48 according to the invention, so that in such a situation it lowers the minimum permissible motor speed to a speed below the idle speed, as illustrated in fi g. 3, for example from an idle speed of approx. 600 rpm or, where applicable, 700 rpm at a cold engine to a minimum speed of approx. 500 rpm, synchronization takes place in the speed range between said speeds so that the synchronization can be carried out and the changeover .

The reduction of the idle speed enables upshift on very steep slopes, where upshift has not previously been possible with the idle speed as the lowest speed limit but the driver has had to remain in low gear until the end of the hill.

This is especially important at start-up, as the first gear is the most critical, as the input shaft of the gearbox decelerates quickly due to the large gear ratio. The torque is normally sufficient (due to the large gear ratio), which means that if you can only shift up the first gear, it is usually possible to shift up a few additional steps. If it is a long steep hill, you gain a lot from being able to drive in a few gears high-IC. In the diagram in Fig. 4, the process of upshifting on flat ground is shown in a corresponding manner. During shifting, the carriage speed and thus also the speed of the gearbox input shaft are basically unchanged. The time from the start of the shift and until the speeds of the engine and the input shaft of the gearbox are synchronous, so that the shift can be completed, depends on how fast the engine speed drops, but there is never a problem with finally getting in gear. To quickly reduce engine speed, you can use existing engine braking devices such as exhaust brakes or decompression brakes, which are common in engines for heavy trucks.

In the diagram in fi g. 5 illustrates the relationships between different engine speeds required to end up at idle speed when shifting up. "A" marks the speed to end up at idle speed when shifting to the next gear. "B", "c" and "d" mark the corresponding when skipping one, two and three gear steps, respectively. As can be seen from the diagram, it is not possible to directly take up four gear steps while maintaining the speed limit for the idle speed, since the maximum speed of the engine must then be exceeded in order for the idle speed not to be undershot. By temporarily lowering the lower speed limit below the idle speed in accordance with the invention when selecting a gear that requires a lower gear speed than the idle speed, a four-speed shift can still be performed, as illustrated by the dotted bar in the diagram.

In general, low engine speeds provide better comfort. It is therefore an advantage, not least from a comfort point of view, to lower the engine speeds in cases where this is possible. You can then, compared with some upshift without lowering the engine speed during idle speed, take the same upshift step but fl lower the gear speed.

Claims (4)

10 15 20 25 30 BIN 540 Patent claims Motor drive unit, comprising an internal combustion engine (1) and an input shaft (7) connected via a vane coupling (3) to the engine crankshaft (2) to a stepped gearbox (9), having at least one intermediate housing mounted in a housing shaft (1 1), which has at least one gear (16, 17) in engagement with a gear (12,15) on the input shaft, a main shaft (10) mounted in the housing with gears (15,21,22,23) , which engages gears (17, 18, 19, 20) on the intermediate shaft, wherein at least one gear in each pair of interlocking gears on the intermediate shaft and the main shaft is rotatably mounted on its shaft and lockable by means of coupling means ( 13, 24, 25), of which at least the coupling means for some forward gears have no synchronizing function, and operating means (40, 41, 42) cooperating with the coupling means, which are controlled by control means (45, 48) connected to a gear selector (46) with transmission control function and motor control function, in which signals representing the selected gear and o equal engine and vehicle data, which includes at least engine speed, input shaft speed, vehicle speed, clutch position and accelerator pedal position, characterized in that said control means (45,48) are arranged that - when synchronization with the motor when shifting requires lower engine speed than the motor determined by the control means idle speed for the selected gear - steer the engine speed to a speed lower than the idle speed and that the control means are arranged to be engaged in the selected gear, when the engine speed has reached a speed suitable for loading the selected gear during the idle speed. Drive unit according to claim 1, characterized in that said control means (45, 48) comprise a transmission control unit (45) and a motor control unit (48) which communicate with each other. Drive unit according to Claim 1 or 2, characterized in that the idle speed determined by the motor control unit (48) is approximately 600 rpm and in that the motor control unit is arranged to lower the minimum motor speed to approx. 500 rpm ... 521 540 Drive unit according to Claim 3, characterized in that the motor control unit (48) is arranged to control the motor speed at certain conditions, for example in the case of a cold engine, at an increased idle speed, eg about 700 rpm, and when shifting under said conditions. lower the minimum permissible engine speed to a speed below the original idle speed.