GB2233408A

GB2233408A - Electro-pneumatic gear-change system with emergency back up pressure source

Info

Publication number: GB2233408A
Application number: GB9010840A
Authority: GB
Inventors: Norbert Lemp
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 1989-05-16
Filing date: 1990-05-15
Publication date: 1991-01-09
Anticipated expiration: 2010-05-15
Also published as: SE9001718D0; SE9001718L; GB9010840D0; GB2233408B

Abstract

An electro-pneumatic gear-change system for a variable-speed gearbox, in which the gear selections are made pneumatically via actuating cylinders which are controlled by solenoid valves. The solenoid valves or a central valve block (4) are supplied via a compressed air connection (3) where a valve (5) is positioned with which a first connection (31) which is or can be connected to the general air supply system (6) of the vehicle, and with which a second filling connection (32) which is or can be connected to a second compressed air source (7) upon failure of the general air supply system. It is an advantage if the valve is a two-way valve (51). The second source (7) is preferably a spare tyre. <IMAGE>

Description

EMERGENCY GEAR CHANGE DEVICE FOR AN ELECTRO-PNEUNATIC GEAR-CHANGE SYSTEM DESCRIPTION This invention relates to an emergency gear change device for use with an electro-pneumatic gear-change system and to a gear change system fitted with said device.

Electro-pneumatic gear-change systems are known which are designed to assist drivers of vehicles, usually heavy vehicles with many gears.

In the applicant's own gear-change system with Easyshift (ES), the control elements (gear-shift lever and clutch pedal) are present as in a conventional gear-shift arrangement and also have to be operated by the driver. There is no usual gear-shift linkage, however, because the drivers gear-shift commands are conveyed electrically via the gear-change switch or gear-shift lever to a central valve block on the gear box. Here, these electrical -switching pulses are converted into pneumatic signals. The command for a gear-change is given via a trip switch on the clutch pedal and a main control valve and is carried out by corresponding actuating cylinders.

In another of the applicant's gear-change systems with automatic preselection (APS), the starting operation and all other gear-change operations are preselected in a specific postion of the preselector switch. In this position of the preselector switch, the driver has only to operate the clutch pedal in order to change-gear. Gear shifting is then effected pneumatically via actuating cylinders, as already described in conjunction with ES gear-change system.

Finally, an emergency system is also known, whose operation is purely pneumatic and which allows the vehicle to be moved, albeit to a limited extent, in the event of failure of the electrical system.

In all of these gear-change systems, compressed air, which is predominantly required for gear-changing in order to move the vehicle, is generated in the vehicle and is stored in a limited quantity in a compressed air reservoir independently of the air reservoir for the brakes. In addition to the solenoid valves for gear-changing, other loads, e.g.

for operating the doors in a bus, are connected to this compressed air system and, because of the many branches of this compressed air circuit, it is very susceptible to breakdown. For instance, if the vehicle is parked for a lengthy period, due to defective seals; the pressure can fall to such an extent that the vehicle can no longer be operated.

However, a leak can also occur during operation so that the vehicle will be unable to move.

The aim of the invention is therefore to provide a simple way of modifying an electro-pneumatic gear-change system so that in the event of loss of compressed air in the so-called general supply circuit of the vehicle, the vehicle can be moved again or generally put into operation.

According to one aspect of the invention, there is provided an emergency gear-change device for fitting to an electro-pneumatic gear-change system for a variable speed gearbox in which the gear selections are made pneumatically via actuating cylinders controlled by solenoid valves from a main source of compressed air on the vehicle, the device comprising a valve having first connection means for connection to the main compressed air source of the vehicle, second connection means for connection to an emergency source of compressed air and third connection means for connection to the solenoid valves controlling the actuating cylinders, the arrangement being such that, in use, the valve normally places the main compressed air source in communication with the solenoid valves but, in the event of a failure in said supply of compressed air from the main source, the valve places the emergency source in communication with the solenoid valves.

According to another aspect of the invention there is provided an electro-pneumatic gear-change system for a variable-speed gearbox, in which the gear selections, which are controlled by solenoid valves, are made pneumatically via actuating cylinders, whereby the solenoid valves or the central valve block in which the solenoid valves are combined, are supplied via a compressed air connection, a valve positioned at the compressed air connection, with a first connection to the general compressed air system of the vehicle and a second compressed air connection to which a second compressed air source is or can be connected.

With the preferred device and gear change system of the invention, it is possible to isolate the general compressed air supply circuit of the vehicle, which may have many branches and is thus at risk, via a simple valve, preferably a two-way valve, which is positioned at the compressed air connection, in conjunction with a filling connection and a second compressed air source. This ensures that at least the actuating cylinder required for starting the engine or for driving can be supplied with compressed air. If the second compressed air source is the spare tyre found in every vehicle, there is practically no additional cost as the tyre inflating hose, which is required for connecting the spare tyre to the filling connection, is present in every vehicle.If, for example, a line filter or possibly a drainage device is placed between the two-way valve and the filling connection, the emergency compressed air supply is complete, so that as a result of the relatively large reservoir provided by the spare tyre, a larger distance can be travelled without limitations, if gear changes are kept to a minimum.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a known electro-pneumatic gear-change system (ES); Figure 2 is a block diagram of the compressed air supply of the gear-change system of Figure 1 but including the emergency gear-change device of the invention incorporating a two-way valve, Figure 3 is a block diagram as in Figure 2, but with a solenoid valve and Figre 4 is a pneumatically-operated emergency gear-change device.

In the gear-change system in Figure 1, gearbox 1 is controlled electro-pneumatically. The control commands are generated by gear-change switch 8, trip switch 81 and clutch pedal 82 and pass via electric cables 83 to a central valve block 4 which houses all the solenoid valves needed to operate the gearbox.

Compressed air is supplied via compressed air connection 3, distributor 84 and line 85 to the solenoid valves in the central valve block 4 and via line 86 to the gear-change switch 8. The actual changing of the gears in the gearbox 1 is effected by actuating cylinders 2 whose position is controlled by the solenoid valves in the central valve block 4.

A pressurised supply or so-called general compressed air system 6 for the vehicle is installed in the latter independently of the gear-change system and has a compressed air reservoir 61 with a compressed air cleaner and water separator 62. The gear-change system also includes an electronic module 87 for overspeed protection, a warning buzzer 88 and an electronic tachometer 89 to ensure its reliable operation. In this example, the gearbox has 6 forward gears in addition to the reverse and crawler gears. In another gear-change system (APS), as described in the introduction to this patent specification, the compressed air connection 3 can be made directly into line 85, that is just before the central valve block 4, because the gear-change switch 8 is constructed as a purely electrical preselector switch and requires no compressed air.In Figure 2 the compressed air connection 3 is made directly to the central valve block 4 and a two-way valve 51 is connected to a first compressed air connection 31 and to a second compressed air connection (filling connection) 32.

The compressed air connection to the general compressed air system 6 of the vehicle with compressed air reservoir 61 and compressed air cleaner with water separator 62, is made via the connection 31. The second filling connection 32 is connected to the second compressed air source, comprising a spare tyre 7, via a tyre inflating hose 71. A line filter 33 and a drainage device 34 can be placed between two-way valve 51 and the second compressed air connection (filling connection) 32.

The emergency compressed air supply to the solenoid valves 4 and the actuating cylinders 2, as shown in Figure 2, is effected as follows: During normal use, the supply to the solenoid valves 4 is effected via the general compressed air system 6 of the vehicle, where the shut-off ball of the two-way valve 51 is in the position shown. If this pressure drops, it is possible to connect the spare wheel 7 as a second emergency compressed air source to the filling connection 32 via tyre inflating hose 71. When the connection is made, the ball of the two-way valve closes off the connection 31 from the general compressed air system of the vehicle and the solenoid valves 4, and thus also actuating cylinders, are supplied by the emergency compressed air source of the spare tyre 7.In principle, the filling connection 32 already exists in every vehicle as a so-called test connection so that in actual fact only the two-way valve 51 and possibly a line filter 33 and a drainage device 34 or, as represented by 62 in the general compressed air system 6, a combined device, need be fitted. The tyre inflating hose 71 for inflating the tyres is also fitted to every vehicle and in the event of failure if the general compressed sir system. i.e. in an emergency situation, this can be used to connect the spare tyre to the filling connection.

Figure 3 shows a second example where a solenoid valve 52 is used in place of the two-way valve 51. If the solenoid valve is energized, the general compressed air system 6 of the vehicle is connected to the central valve block 4. If the general compressed air system of the vehicle fails, and the solenoid valve takes up the position shown - where the filling connection 32 is connected to the central valve block - the solenoid valves can be supplied via the tyre inflating hose 71 and the second emergency compressed air source of the spare tyre 7. It is possible to connect the filling connection 32 to the vent of the solenoid valve 52 becuse all solenoid valves in the central valve block 4 have separate vents, so that in such a situation repeated venting in the solenoid valve 52 controlling the compressed air can be dispensed with.

The emergency gear-change device in Figure 4 also requires compressed air since its operation is exclusively pneumatic. In this case, as shown in Figre 2 or Figure 3, a two-way valve 51 or a solenoid valve 52 can be positioned at the compresssed air connection 3 in the manner already described. With an emergency circuit, in the event of simultaneous failure of the compressed air, it is thus possible to select a limited number of gears via the second compressed air source e.g. the spare tyre 7, as can be seen from the emergency control valve 9. In this arrangement, the actuating cylinders 2 are supplied with compressed-air via line 91, depending on the setting of the emergency control valve 9, so that the gearbox can be set, for example, to forward gears 1,2, reverse gear and the neutral position.

Claims

1. An emergency gear-change device for fitting to an electro-pneumatic gear-change system for a variable speed gearbox in which the gear selections are made pneumatically via actuating cylinders controlled by solenoid valves from a main source of compressed air on the vehicle, the device comprising a valve having first connection means for connection to the main compressed air source of the vehicle, second connection means for connection to an emergency source of compressed air and third connection means for connection to the solenoid valves controlling the actuating cylinders, the arrangement being such that, in use, the valve normally places the main compressed air source in communication with the solenoid valves but, in the event of a failure in said supply of compressed air from the main source, the valve places the emergency source in communication with the solenoid valves.

2. An emergency gear-change device according to claim 1, wherein the emergency compressed air source is the spare tyre of the motor vehicle.

3. An emergency gear-change device according to claim 1 or claim 2, wherein the valve is a two-way valve.

4. An emergency gear-change device according to claim 3, wherein a line filter for cleaning air supplied from the emergency source is positioned between the two-way valve and a filling connection to said emergency compressed air source.

5. An emergency gear-change device according to claim 4, wherein a drainage device is positioned between the filling connection and the two-way valve.

6. An emergency gear-change device according to claim 4, wherein the spare tyre is connected to the valve via a tyre inflating hose connected to. the filling connection.

7. An electro-pneumatic gear-change system for a variable-speed gearbox, in which the gear selections, which are controlled by solenoid valves, are made pneumatically via actuating cylinders whereby the sdlenoid valves or the central valve block in which the solenoid valves are combined, are supplied via a compressed air connection, a valve positioned at the compressed air connection with a first connection to the general compressed air system of the vehicle and a second compressed air connection to which second compressed air source is or can be connected.

8. An electro-pneumatic gear-change system according to claim 7, wherein the second compressed air source is the spare tyre of the motor vehicle.

9. An electro-pneumatic gear-change system according to claim 8, wherein the valve is a two-way valve.

10. An electro-pneumatic gear-change system according to claim 9, wherein a line filter for cleaning the compressed air is positioned between the two-way valve and the filling connection.

11. An electro-pneumatic gear-change system according to claim 10, wherein a drainage device is positioned between the filling connection and the two-way valve.

12. An electro-pneumatic gear-change system according to claim 9, wherein the spare tyre is positioned as a true emergency driving device at the filling connection via the tyre inflating hose.

13. An electro-pneumatic gear-change system substantially as herein described with reference to Figures 2-4 of the accompanying drawings.

14. An emergency gear-change device for fitting to an electro-pneumatic gear-change system substantially as herein described with reference to Figures 2-4 of the accompanying drawings.