DE2622927A1 - Automatic transmission for heavy vehicle - with fluid clutch and sensors to control gear change without synchronisation - Google Patents

Abstract

The automatic transmission is designed for heavy vehicles and uses a simple, economic layout without expensive synchronisation on each gear. A simple gear box is separated from the drive by a fluid clutch and the input and output drives from the gear box are monitored by sensors which are coupled to the gear change control. The gear change conditions are controlled w.r.t. vehicle speed and torque demands. The throttle setting is controlled during the gear change, so that it is blocked when changing up to allow the control to synchronise the next gear setting.

Description

Automatic Transmission Priority: May 23, 1975, Great Britain, No. 22467/75 The invention relates to an automatic transmission for motor vehicles; it is particularly suitable for heavy automatic transmissions Vehicles such as trucks or buses.

One known type of automatic transmission is a hydrodynamic one Uses a torque converter coupled to a planetary gear; the Control takes place through a relatively complicated hydraulic control system instead of.

In another known type of automatic transmission, a number used by planetary gears, with the switching operations by means of electrically / pneumatically or hydraulically operated brake bands are effected, the in turn are switched by a relatively complicated control system.

The object of the invention is to find an automatic transmission, that is particularly simple in construction, cheap to manufacture and reliable in operation is.

According to the invention, this object is achieved by an automatic Transmission with a fluid coupling, the output of which is connected to the input of a countershaft transmission is connected, and by a control device, by means of which various influencing factors, such as engine speed and throttle position (to name just a few), detectable and control signals as a function of a previously determined function map can be generated to trigger shifts in the transmission.

In an advantageous embodiment of the invention, there is a countershaft transmission provided without a synchronization device, and the control device has sensors to detect the speed of the input and output shaft of the gearbox, which is in Output a first and a second control signal depending on these speeds, and a comparison device for comparing the two control signals and for Output of another control signal to trigger a gear change when it is reached a suitable speed difference between the transmission input and output speed on.

Another advantageous embodiment of the invention consists in that a device is provided by means of which the throttle valve when upshifting can be closed, and thereby also a switching-neutral intermediate period is achieved during which a synchronization can be made - "throttle dipping "device - and that furthermore a switching device for a brake is provided for braking the transmission input shaft when upshifting. Besides it is also advantageous if the control device has a device for keeping it open of the throttle during a load downshift and into a "Neutral position" is adjustable, during the duration of which the transmission is in a neutral Is held intermediate position between the two gears to be shifted.

Another advantageous embodiment of the invention is thereby characterized in that the output of the fluid coupling is via a coupling device is connected to the input of the countershaft transmission and the countershaft transmission is a Having synchronization device, by means of which synchronization during the Gear change is feasible. Advantageously, there is again a “throttle” dipping "device (see above!) is provided, i.e. the control device has a corresponding Device by means of which the throttle valve can be closed when upshifting.

An automatic transmission according to the invention preferably has a Control device with a switching valve for distributing the working fluid the individual elements to be switched with Facilities for production of signals depending on the vehicle speed, on the engine speed and from the throttle valve position, as well as with a device for regulating the Engine power during all gear changes.

In the drawing, the invention is still illustrated by means of schematic sketches explained in more detail. 1 shows a schematic diagram of an embodiment of the invention, and FIG. 2 is a schematic diagram representation of another embodiment the invention.

In the schematic representation of an embodiment shown in FIG. 1 of an automatic transmission according to the invention is a fluid coupling 1 provided, which is connected to the input (input shaft) 2 of a countershaft transmission, which is indicated generally by 3. This countershaft transmission 3 has an output (Output shaft) 4 up. The input shaft 2 of the transmission 3 can by means of a brake 5 can be decelerated or braked.

Furthermore, a selector lever 6 is provided, which is used by the driver for adjustment a desired working position of the automatic transmission can be operated.

The transmission 3 has no synchronizing device for the various Gears open. Instead, the synchronization is achieved by setting it appropriately reached the engine throttle, namely when downshifting that the speed the input shaft 2 of the transmission 3 is raised and when upshifting by means of the Brake 5 is lowered. The synchronous speed can be passed electronically the installation of sensors 11 and 12 on the input or output shaft of the transmission 3 determine.

The gear change mechanism in the transmission 3 can either be electro-pneumatic or electro-hydraulically controlled and a number of servo-assisted Include devices that can be placed on top of the transmission.

When shifting up, the synchronous speed can be passed through achieve an automatic "throttle dipping", i.e. through an automatically adjusted Lowering the engine speed. For a downshift under load, use the throttle valve and the control device kept open during the switching process can be switched into a neutral intermediate position or that.

The control system sets a neutral intermediate position. In the event of a no-load downshift, the throttle closing mechanism operates vice versa and increases the engine speed.

In order to effect the respective adjustment of the throttle valve, a Lost motion linkage between the fuel pump 7 of the vehicle and the throttle valve linkage interposed. By means of a Piston pressurized with compressed air 8 the position of the fuel pump frame can be adjusted while changing gears respectively.

rules. The piston 8 in turn supplies or controls a valve 9 - this whole throttle linkage adjustment mechanism can be made similar to that which is already described in DT-OS 25 22 240.

In the system shown, a control device lo is also provided, to which the input signals listed below are applied: 1. one Signal that gives information about the position of the selector lever 6 (shown by the line A); 2. a signal that provides information about the speed (Speed) of the input shaft 2 of the transmission 3 outputs (represented by the line B); 3. a signal that provides information about the speed (rotational speed) of the Output shaft 4 of the transmission 3 there (shown by line C).

In the following, the mode of operation of the automatic gearbox, which is shown in Fig. 1, described in more detail: Start position of the transmission: By moving the selector lever from the neutral position to the "automatic" position causes the driver of the vehicle that the Gear itself to the start position adjusts. When the vehicle is stationary, this means that the transmission input shaft to Is brought to a standstill before synchronization can occur. This will achieved in that the brake 5 for the transmission input shaft 2 by a signal is activated from the control device lo. If the transmission input shaft is up to Is decelerated to a standstill, then the control device sends a signal to the gear selection mechanism to engage the shift claws.

As soon as the gear is engaged, the brake 5 is applied to the transmission input shaft acts, released and the vehicle is ready to drive off when the throttle linkage is depressed will. To ensure that there is no engine power when the starting gear is engaged occurs, the control device lo also gives a control signal to the throttle valve adjustment mechanism away. A control signal is sent back to the driver as soon as the gear is positively engaged is.

Upshifting: After the start gear is engaged, that will Set the vehicle in motion as soon as the accelerator pedal is depressed. When the vehicle When speed increases, the control device is determined at in advance Motor speeds (engine speeds) cause an upshift: When the correct switching speed, the control device lo a control signal for Removal of engine power by actuating the throttle rod or of the throttle valve adjustment mechanism. At the same time there is a signal causes the gear to disengage on the gear selection device. When the engine speed drops, the control device will synchronize the internal Determine components and then emit an engagement signal for the next gear. As soon as the engagement process has taken place, the performance reverts to that of the Driver returned predetermined value.

However, in the case of many large diesel engines, the decrease is the The engine speed is far too low when the fuel supply is switched off. This can do this cause the synchronization process to take an extremely long time. During this period of time, the vehicle speed can drop so much that a synchronization is no longer possible at all, or that instead other difficulties, such as control fluctuations, instabilities, vibrations etc. occur. To avoid this, it proves to be advantageous if at the automatic transmission according to the invention, the control device, the brake 5 for the transmission input shaft is activated to suit the drop in engine speed Way to support. The brake should not be applied so long that the Transmission input shaft comes to a standstill, but only so much that the speed the transmission input shaft sinks sufficiently low, so that a synchronization within can be performed in a reasonable amount of time.

Downshifting under load: When the engine speed is up to is lowered to a predetermined point by the inertia or drag of the vehicle is, the control device gives a signal to switch on the next lower Ganges. For this purpose, the transmission is first brought into a neutral position and held in this briefly, while in the meantime the engine speed to Increase is brought. The driver depresses the accelerator pedal. When the synchronization has been carried out, the control device emits a signal for engaging the corresponding gear. It must be ensured that that the effect of the accelerator pedal is momentarily canceled while the neutral Position in the gearbox is switched on.

Downshifting with no load: When the vehicle is with the throttle closed becomes slower, the control device in turn gives a signal for switching on of the next lower gear as soon as the vehicle speed has increased to an im previously set value has decreased. The neutral position of the transmission is included. switched on and then the accelerator pedal or the throttle valve automatically up adjusted to achieve or complete the synchronization. After that the throttle valve closed again (or the accelerator pedal returned) and the corresponding Gear engaged. Such "downshifting" operations occur at low engine speeds appear, if there is no power, unless the vehicle brakes are used, then such shifts are carried out at higher engine speeds to the Motor braking effect still to be supported.

Kickdown device: You can also use a power sampling switch install, which ensures that an upshift even at lower engine speeds is made to enable economical driving, or until if not just maximum power is needed. Such a change then in the level of performance issues a "kickdown" condition provided the vehicle speed is within a reasonable range that enables the next lower gear to be engaged made possible without overtightening.

Furthermore, devices for locking aisles or be provided for delimiting aisle areas ("override facilities").

Another embodiment of an automatic according to the invention Transmission is shown in FIG. The main difference between the two embodiments is that in the embodiment according to FIG a conventional synchronizing mechanism 14 in the countershaft transmission 3 is included, but a coupling 11 between the fluid coupling 1 and the input shaft 2 of the transmission 3 is interposed. The one shown here Embodiment of the transmission according to the invention is thus based on the use a conventional synchronizer for performing the synchronization effect during the switch-on and switch-off process, whereby the control device or the required Control system is simplified to a certain extent. In the embodiment shown just have to use a simple accelerator pedal or. Throttle valve operating mechanism from the control device are controlled.

In the following description, those parts that are shown in Fig. 1 correspond to and are already described there, with the same reference numerals Mistake. The operation of this embodiment shown in Fig. 2 is in Described in more detail below: Start position of the gear unit: By a movement of the selector lever 6 in the "automatic" position is the delivery of a signal from the Control device lo triggered on clutch 11, which separates the fluid coupling 1 triggers from gearbox input 2. The gear selector is then activated to the Engage starting gear. As soon as the starting gear is finally engaged, the clutch is 11 is brought back into engagement and the vehicle is then ready to step down of To drive away the accelerator.

The accelerator pedal (or throttle valve) is released during engagement of the starting gear is automatically withdrawn (or closed).

Upshifting: When the accelerator pedal is depressed, the fluid coupling takes place a transmission of the driving force and the vehicle departs. With one in advance certain engine speed, the control device gives a signal to switch on the next higher gear from, the clutch 11 disconnected, the accelerator pedal withdrawn (respectively.

closed the throttle valve /) and then the desired gear selected or is switched on. The clutch 11 is then brought into engagement again and de power or power of the engine returned to the original size.

Downshifting under load: When the engine speed under load is up to is lowered to a predetermined value, the control device outputs a signal to switch on the next lower gear. For this purpose, the coupling 11 is separated and the next gear switched on. Then the clutch 11 is engaged again. The throttle valve remains open (resp.

the accelerator lever is depressed) to increase the engine speed and thereby reducing the work of the clutch 11 during the engagement.

Downshifting with no load: When the vehicle slows down with no load, the control device in turn switches through the individual gears as a function of the gears from reducing the vehicle speed. For this purpose, the Clutch 11 opened and the next lower gear switched on, then the clutch 11 re-engaged.

Kickdown device: Also in the embodiment shown in FIG. 2 of the automatic transmission according to the invention can, in turn, have a switch for scanning the power level of the engine to enable economical driving in Connection to a kickdown switch-on device can be provided.

Furthermore, gear locks and / or limiters are also expediently for the individual speed ranges (similar to that shown in FIG System).

Summing up the characteristics of the automatic transmission according to the invention together again, the following gear functions result: 1. an automatic control or switching of all gears 2. stop positions at all Gears with gear and speed locks to prevent impermissible driving conditions 3. Protection against low fluid pressure for operating servo units 4. Full synchronization of all gear changes to achieve smooth shifting and maximum transmission life 5. Possibility of a kickdown in all gears at speeds at which a forced downshift does not lead to that the engine speed rises above the permissible maximum speed. 6th possibility an additional engine braking effect by increasing the speeds at which a Upshifting is carried out under the conditions "without gas, with brake" 7. economical Driving style or lower fuel consumption possible by lowering the engine speed downshifting, under the condition n no throttle "8. at In the absence of a vehicle speed signal, the power transmission is in the The gear currently engaged is held. 9. Full engine speed / speed interlock 10. During upshifts, the power transmission is brought into a neutral position and the gas is released. 11. When downshifting, the power transmission is shut down brought into a neutral position and taken the gas up (Throttle open) 12. Facilities are provided to initiate and regulate the application a brake for the transmission input shaft 13. Motor / transmission coupling at Start 14. Simple assembly for easy service.

If in the above in the explanation of those shown in the figures Embodiments Terms such as "accelerator pedal" or "throttle valve" are sometimes used alone were used, it should be noted that the one used alone Of course, the term is only used as a representative and not exclusively will. Rather, the invention also encompasses all those skilled in the art to the same extent common other design variants, whereby e.g. opening the throttle valve "as is to be regarded as equivalent to "stepping on the accelerator". Using the The designation throttle valve should therefore only be used as an example for power control the engine is at a standstill; it is by no means to say that the invention is about can only be used for engines with throttle valve output control.

Claims (7)

Expectations 1. Automatic transmission, especially for trucks, g e k E n n z e i c h n e t by a fluid coupling (1), the output of which with the Input of a countershaft transmission (3) is connected, and through a control device (10), by means of which various influencing factors, such as engine speed and throttle position, detectable and control signals as a function of a predetermined function map can be generated to trigger shifts in the transmission. 2. Automatic transmission according to claim 1, characterized in that g e k e n n -z E i c h n e t that a countershaft transmission (3) is provided without a synchronizing device is, and the control device (10) sensors (12, 13) for detecting the speed of Input (2) and output shaft (4) of the transmission (3), depending on these Speeds output a first (B) and a second (C) control signal, as well as a comparator to compare the two control signals (B, C? and to output a control signal to trigger a gear change when a suitable speed difference is reached between the transmission input and output speed. 3. Automatic transmission according to claim 1 or 2, g e k e n n -z e i c h n e t by a closing device for the throttle valve when upshifting to achieve a neutral intermediate period for synchronization and a Switching device for a brake (5) to brake the transmission input shaft (2) when upshifting. 4. Automatic transmission according to one of claims 1 to 3, characterized g e k e n n n z e i c h n e t that the control device (10) is a device for Having the throttle open during a load downshift and can be set to a neutral position, during the duration of which the transmission (3) held in a neutral intermediate position between the two gears to be shifted is. 5. Automatic transmission iach claim 1, characterized in that g e -k e n n z e i c h n e t that the output of the fluid coupling (1) via a coupling device is connected to the input of the countershaft gear (3) and the countershaft gear (3) has a synchronizing device (14) for changing gears. 6. Automatic transmission according to claim 5, characterized in that g e -k e n n z e i c h n e t that the control device (10) is a closing device for the throttle valve when upshifting ("throttle dipping"). 7. Automatic transmission according to one of claims 1 to 6, characterized it is noted that the control device (10) has the following devices comprises: a) a switching valve for distributing the working fluid to the individual elements to be switched, b) a device for generating a signal as a function of the vehicle speed, c) a device for generating a signal as a function of the engine speed, d) a device for generating of signals as a function of the throttle valve position, and e) a device to regulate the engine power during all gear changes. Blank page