PROCEDURE FOR STARTING A VEHICLE

Abstract

Method for starting a vehicle comprising a power engine (12), a torque converter assembly (20) with converter lock-up clutch (100) and clutch actuation device (90), and an auxiliary pressure device (54), in a power train (10) designed for start / stop operation of the power engine (12), comprising the steps Stopping the engine (12) when the vehicle is stationary, Generating a flow of hydraulic pressure fluid through the auxiliary pressure device (54) while the power machine (12) is stopped, Supply at least part of the flow of hydraulic pressure fluid to the clutch actuation device (90) to allow the torque converter lock-up clutch (100) to be engaged, Starting the power engine (12), and Reducing the hydraulic fluid pressure to the clutch actuation device (90) after the vehicle has moved to allow slippage of the torque converter lock-up clutch (100).

Description

[0001] The present disclosure relates to the starting of a vehicle. In particular, it relates to the operation of torque converter lock-up clutches for automatic transmissions used in applications with start / stop functionality of the engine (ESS), and more specifically to the operation of a torque converter lock-up clutch in an application with start / stop functionality of the engine, which improves the starting performance and acceleration.

[0002] The most generally recognized significant functional difference between a conventional vehicle powertrain, as disclosed in DE 103 60 479 A1, and one designed for start / stop operation of the engine, is the delay experienced by the driver during a car start event before he feels any acceleration.While the engine of a conventional vehicle remains engaged in neutral when the vehicle is stopped, for example in traffic, so that when the brake is released and the accelerator pedal is pressed, the engine speed quickly increases above idle and the degree of torque converter coupling and torque delivery through the transmission quickly increases, in a powertrain with start / stop functionality, after the brake is released and the accelerator pedal is pressed, the engine must first spin up and restart, and then, as the engine speed increases, begin to transmit torque through the torque converter and the transmission.

[0003] Although it appears that the sequence of engine start and speed increase is primarily responsible for the vehicle movement and acceleration delay, it has been found that some delay is caused by the fact that the torque throughput cannot be established quickly through the fluid coupling of the torque converter, especially if the input to the torque converter and thus the torque converter pump wheel were previously stationary due to the stopped engine.

[0004] The subsequently published German patent DE 10 2011 087 891 A1 discloses a method for automatically switching off and starting an internal combustion engine in a motor vehicle with an automatic or automated transmission by means of a start-stop device. This device initiates an automatic shutdown of the internal combustion engine during a coasting phase and initiates an automatic start of the internal combustion engine when at least one start request is received. To switch off the internal combustion engine during a coasting phase, the charge exchange in the cylinders of the internal combustion engine is at least almost completely prevented, and simultaneously a torque converter lock-up clutch arranged between the internal combustion engine and the transmission for power transmission is controlled such that this torque converter lock-up clutch remains at least almost completely closed or is closed.When the internal combustion engine is restarted, the torque converter lock-up clutch is opened.

[0005] From DE 10 2006 034 935 A1, a method for operating a drive train comprising an internal combustion engine, an electric motor, a transmission and a torque converter with a converter lock-up clutch is known, in which the converter lock-up clutch is permanently closed at least between transmission shift operations to bridge the torque converter during an electric operating state in which the internal combustion engine is switched off and the electric motor is switched on, and / or during a recuperation operating state in which the internal combustion engine is switched off and the electric motor is operated as a generator.

[0006] DE 10 2008 064 291 A1 teaches a method in which a disconnecting clutch arranged between an internal combustion engine and an electric machine connected to the transmission is closed, the torque of the electric machine is increased according to the torque transmitted by the disconnecting clutch, the internal combustion engine is started depending on the torque required and achievable by the internal combustion engine, and, in particular after the start of the internal combustion engine, the torque of the electric machine is reduced according to the increase in the torque of the internal combustion engine, whereby the comfort level of the start of the internal combustion engine is adjusted by changing the time of the start of the individual process steps and / or by changing the duration of the individual process steps.The starting of the internal combustion engine in a moving vehicle driven by an electric motor should be as smooth as possible, meaning without any noticeable difference in torque at the drive wheels. Before the starting process, the lock-up clutch may be open, slipping, or closed, depending on the operating state of the vehicle and the drivetrain. Therefore, it is advantageous to engage the lock-up clutch before the disconnect clutch begins to close. If the lock-up clutch is closed, it should be opened and / or slipped before the disconnect clutch begins to close. This dampens disturbances and allows the electric motor to operate at a controlled speed while the disconnect clutch is subsequently closed. After the internal combustion engine has started and a positive connection has been established at the disconnect clutch, the lock-up clutch is closed again.

[0007] The object of the present invention is to provide a method for the prompt and smooth starting of a vehicle comprising a power engine, a torque converter with a torque converter lock-up clutch and a clutch actuation device, as well as an auxiliary pressure device.

[0008] This problem is solved by a method having the features of claim 1.

[0009] Advantageous embodiments are specified in the dependent claims.

[0010] The invention is described below by way of example with reference to the drawings: Fig. Figure 1 is a schematic representation of a section of a motor vehicle powertrain comprising a power engine, a torque converter assembly with converter lock-up clutch and a transmission; Fig. Figure 2 is a graph illustrating the performance of a powertrain with start / stop functionality of the engine during an event of a stopped engine, a start-up event of the engine, and an acceleration event; and Fig. Figure 3 is a graph illustrating the performance of a drive train with start / stop functionality of the power machine, which uses the method of the present invention, during an event of a stopped power machine, a start event of the power machine and an acceleration event.

[0011] With reference to Fig. Figure 1 illustrates a section of a motor vehicle powertrain and is generally designated by reference numeral 10. The motor vehicle powertrain 10 comprises a power engine 12, which may be a gasoline, flex-fuel, or diesel engine, an electric motor or motors, or a hybrid power system comprising a combination of one or more power engines and one or more electric motors. Drive torque from the power engine 12 is supplied to a crankshaft 14 at an input shaft 16 of a torque converter assembly 20 with a converter lock-up clutch 100. The torque converter assembly 20 with converter lock-up clutch 100 comprises a pump impeller 22, which is coupled to and driven by the input shaft 16, a stator 24, which is fixed to a stationary housing 26 of the torque converter assembly 20, and a turbine wheel 28.The turbine wheel 28 is coupled to and drives an output element 32, which is coupled, for example, by serrated teeth or a one-piece component, to a transmission input shaft 38 of an automatic transmission 40. The automatic transmission 40 will typically comprise a plurality of planetary gear assemblies, generally arranged in pairs, as well as friction brakes and clutches (all not illustrated), or it may be a dual-clutch transmission (DCT), which has a pair of input clutches and a pair of countershafts, a continuously variable transmission (CVT), or another type of automatic or manual transmission. The automatic transmission 40 delivers drive torque through a transmission output shaft 42 to an axle drive assembly (FDA) of a motor vehicle (both not illustrated).

[0012] A hydraulic pump 44 is mounted around and driven by the transmission input shaft 38. When the transmission input shaft 38 rotates, the pump draws hydraulic fluid (transmission oil) from a transmission sump 46 and supplies hydraulic pressure fluid to a hydraulic supply line 50. The hydraulic pump 44 can be, for example, a vane, gear, or gerotor type pump. The hydraulic supply line 50 delivers hydraulic pressure fluid to, for example, the valve body (not illustrated) of the automatic transmission 40 via a transmission supply line 52 and to an auxiliary pressure device 54. The auxiliary pressure device 54 can be a spring- or gas-driven pressure accumulator that provides a reserve of hydraulic pressure fluid when the input shaft 38 of the transmission 40, and thus the hydraulic pump 44, is not rotating. This occurs, among other situations, during an automatic stop event.Alternatively, a small, electrically operated hydraulic pump can be used to supply hydraulic pressure fluid when the (main) hydraulic pump 44 is not operating. The hydraulic supply line 50 also communicates with a solenoid valve 60, which may be a variable force solenoid valve (VFS) or a similar or other type of valve, and which may be controlled by a transmission control module (TCM) 62 or a similar or other type of controller or microprocessor, such as an engine control module (ECM).

[0013] The solenoid valve 60 comprises an inlet or supply port 64, which is in fluid communication with the supply line 50, and an outlet or drain port 66, which returns hydraulic fluid to the transmission sump 46 in a return line 68. A valve spool 70, which defines various webs and passages, moves axially to open and close specific flow paths, as described below. The solenoid valve 60 also comprises a first, release supply port 72, a second, application supply port 74, a third, application drain port 76, and a fourth, release drain port 78.The first release port 72 and the fourth release port 78 feed a release side or chamber 84 of a hydraulic clutch actuating device 90 via a release line 82, and the second enclosing port 74 and the third enclosing port 76 feed an enclosing side or chamber 88 of the hydraulic clutch actuating device 90 via an enclosing line 86. The hydraulic clutch actuating device 90 comprises a piston 92 that defines the release chamber 84 on one side and the enclosing chamber 88 on the other.

[0014] In a first position of the valve slide 70, which is in Fig. As generally illustrated in Figure 1, hydraulic fluid flow is supplied from the inlet port 64 to the first, release supply port 72, through the release line 82 and to the release chamber 84 of the hydraulic clutch actuating device 90, and hydraulic fluid flows from the lubricating chamber 88 through the lubricating line 86 to the third, lubricating drain port 76, from the drain port 66 and through the return line 68 to the transmission sump 46. Thus, the piston 92 of the hydraulic clutch actuating device 90 moves to the right. Fig. 1. In a second position of the valve spool 70, hydraulic fluid flow is supplied from the inlet port 64 to the second, contact port 74, through the contact line 86 to the contact chamber 88 of the hydraulic clutch actuating device 90, and hydraulic fluid flows from the release chamber 84 through the release line 82 to the fourth, release / drain port 78, from the drain port 66 and through the return line 68 to the transmission sump 46. Now the piston 92 of the hydraulic clutch actuating device 90 moves to the left. Fig. 1.

[0015] In this way, the position of the piston 92 of the hydraulic clutch actuation device 90 can be controlled and modulated. It should be understood that this arrangement is only exemplary and that other valve designs and fluid supply and drainage arrangements can be used to achieve this function. Such other arrangements are to be considered as being entirely within the scope of this invention.

[0016] The hydraulic clutch actuation device 90 is a component of a torque converter lock-up clutch 100 of the torque converter assembly 20. Therefore, the torque converter lock-up clutch 100 comprises a first set or a first plurality of friction clutch plates or discs 102 which are coupled to the input shaft 16 of the torque converter assembly 20 by, for example, meshing serrated teeth (not illustrated).

[0017] Interlocking with the first set or first plurality of friction clutch plates or discs 102 is a second set or second plurality of clutch plates or discs 104, which are coupled to the output element 32 of the torque converter arrangement 20 by, for example, interlocking serrated teeth (not illustrated).

[0018] When hydraulic pressure fluid is supplied to the contact chamber 88 of the hydraulic clutch actuating device 90 by the solenoid valve 60, the first and second sets of clutch plates or discs 102 and 104 are compressed according to the summed hydraulic pressure applied to the piston 92, and torque is transmitted from the input shaft 16 to the output element 32 (and the transmission input shaft 38).

[0019] In operation, when a pressure accumulator is used as an auxiliary pressure device 54 and an auto-stop event (stop event of the power unit) occurs, the power unit 12, the transmission input shaft 38, and the hydraulic pump 44 cease to rotate. Thus, no hydraulic pressure fluid is supplied by the (main) hydraulic pump 44, and the pressure in the supply line 50 (and the rest of the automatic transmission 40) drops, and the automatic transmission 40 enters a neutral state. During the auto-stop event, the solenoid valve 60 (and other valves in the transmission 40) are energized. When the engine 12 starts rotating at the end of an auto-stop event, the pressure accumulator auxiliary pressure device 54 is emptied, the valve spool 70 moves to the second position described above, hydraulic fluid is supplied to the inlet chamber 88 of the hydraulic clutch actuation device 90 of the torque converter assembly 20, and the converter lock-up clutch 100 is engaged.

[0020] When the auxiliary electric pump is used as the auxiliary pressure device 54 and an auto-stop event (power engine stop event) occurs, the power engine 12, the transmission input shaft 38 and the hydraulic pump 44 cease to rotate.

[0021] While no hydraulic pressure fluid is supplied by the (main) hydraulic pump 44, the electric auxiliary pressure device 54 maintains the pressure in the supply line 50 and supplies hydraulic pressure fluid. Thus, the automatic transmission 40 remains in gear. During the auto-stop event, the solenoid valve 60 (and other valves in the transmission 40) are energized, the valve spool 70 moves to the second position described above, and hydraulic fluid is supplied to the engagement chamber 88 of the hydraulic clutch actuation device 90 of the torque converter assembly 20 to engage the converter lock-up clutch 100.

[0022] Thus, when the engine 12 is started at the end of the auto-stop event, the torque converter lock-up clutch 100 is engaged or left locked, ensuring prompt and sufficient torque transmission through the torque converter assembly 20 to the transmission 40 and rapid and appropriate acceleration during vehicle start-up. As the vehicle accelerates, the hydraulic pressure in the hydraulic clutch actuation device 90 can be reduced and the slip through the lock-up clutch 100 increased to achieve smooth starts and allow the torque converter assembly 20 to function as a conventional torque converter, i.e., as a fluid coupling device and torque multiplier.

[0023] The hydraulic pressure applied to the contact chamber 88 of the hydraulic clutch actuation device 90 of the torque converter lock-up clutch 100 can be reduced and the slip increased according to one of several approaches. For example, the pressure can be reduced according to a simple step function. That is, the hydraulic pressure applied to the contact chamber 88 of the clutch actuation device 90 can be reduced in, for example, ten equal ten percent increments over a few seconds, a smaller number of larger increments, a larger number of smaller increments, unequal increments (e.g., smaller initial increments and larger subsequent increments), increments over longer or shorter periods, and combinations thereof.

[0024] Furthermore, the hydraulic pressure applied to the engagement chamber 88 of the clutch actuating device 90 can be reduced according to a linear function or a higher-order function (and the resulting clutch slip 100 can be increased). That is, instead of reducing or increasing the pressure and slip in steps or increments, the pressure and slip can be changed according to a linear (proportional) relationship or a higher-order function.

[0025] Finally, the hydraulic pressure applied to the engagement chamber 88 of the clutch actuating device 90 can be reduced (and the resulting slip increased) according to a specific, usually predetermined function of torque converter input speed via clutch slip. That is, data from a vehicle speed sensor (or shaft speed sensor) can be used to achieve any degree of clutch engagement (or disengagement) and resulting clutch slip according to a predetermined program or relationship. This speed-to-slip relationship can further be refined or modified by delaying the increase in slip when the vehicle operator demands significant acceleration.

[0026] Fig. 2 and Fig. Figure 3 illustrates the comparative starting performance (acceleration) of a vehicle designed for start / stop operation during a car start. In both diagrams, time is represented on the horizontal (X) axis. Fig. Figure 2, which represents a conventional vehicle designed for start / stop functionality of the engine according to the state of the art, illustrates that it takes 1 second to achieve a certain acceleration S1. Fig.Figure 3 represents a similar event in a vehicle designed for a start / stop functionality of the engine, which incorporates and operates according to the method of the present invention. Here, only S2 seconds elapse before the vehicle achieves the same acceleration. Thus, an exemplary vehicle designed for a start / stop functionality, operating according to the present method of the invention, requires only approximately one-quarter of the time to achieve the same acceleration relative to a conventional vehicle designed for a start / stop functionality, according to the prior art, at the beginning of an auto-start event.

Claims

[1] Method for starting a vehicle comprising a power engine (12), a torque converter assembly (20) with converter lock-up clutch (100) and clutch actuation device (90), and an auxiliary pressure device (54), in a power train (10) designed for start / stop operation of the power engine (12), comprising the steps Stopping the engine (12) when the vehicle is stationary, Generating a flow of hydraulic pressure fluid through the auxiliary pressure device (54) while the power machine (12) is stopped, Supply at least part of the flow of hydraulic pressure fluid to the clutch actuation device (90) to allow the torque converter lock-up clutch (100) to be engaged, Starting the power engine (12), and Reducing the hydraulic fluid pressure to the clutch actuation device (90) after the vehicle has moved to allow slippage of the torque converter lock-up clutch (100). [2] Method according to claim 1, wherein the auxiliary pressure device (54) is a pressure accumulator. [3] Method according to claim 1, wherein the flow of hydraulic pressure fluid is controlled by a solenoid valve (60) which is controlled by a transmission control module (62).

Images