WO1997015769A1

WO1997015769A1 - Switching device for motor vehicle gear boxes (pneumatic servo switch)

Info

Publication number: WO1997015769A1
Application number: PCT/EP1996/004545
Authority: WO
Inventors: Dieter Fischer; Wilfried Glaser; Daniel Kleiner; Klaus SPÄTH; Jürgen LAUMANN; Christoph Nuding; Rafael Tschirdewahn
Original assignee: Zf Friedrichshafen Ag
Priority date: 1995-10-24
Filing date: 1996-10-18
Publication date: 1997-05-01
Also published as: DE19539471A1

Abstract

The switching device (10) is intended in particular for toothed wheel gear boxes in motor vehicles. An actuating rod (20) in the switching device (10) can slide axially inside a piston rod (22) and co-operates via a switching linkage (6, 8, 16, 18) with a gear lever (4). A piston (114) which can be actuated on both sides with a pressurised medium is provided on the piston rod (22) which co-operates with means (24, 26, 28, 32) for switching the toothed wheel gears. When the actuating rod (20) moves axially in the piston rod (22), control valves (100, 102, 106, 108) can be actuated via command pistons (92, 94). The switching force exerted via the gear lever (4) and switching linkage (6, 8, 16, 18) on the actuating rod (20) is transmitted proportionally via the piston rod (22) to the means (24, 26, 28, 32) for switching the toothed wheel gears.

Description

Switching device for motor vehicle change gearbox - pneumatic shift servo -

The invention relates to a switching device for

Motor vehicle change transmission according to the preamble of claim 1.

In such switching devices, the rotary movement of the shift rod serves to preselect the individual shift gases and generally does not require high shift forces. The axial longitudinal movement of the shift rod serves for engaging the desired gear and, particularly in the case of transmissions for heavy vehicles and those vehicles whose driver's seat is arranged away from the transmission, requires greater shifting forces.

Today's commercial vehicles, such as buses and lorries, have spatial conditions for the installation of the transmission with their front link construction, in which case the transmission inevitably moves far away from the driver's seat. The distance becomes particularly great in vehicles with underfloor or rear engines. The long, sometimes tight shift linkage in mechanically shifted transmissions often makes the exact gear change difficult.

In order for the driver of a motor vehicle to devote his full attention to road traffic, he must be relieved and supported as much as possible in all activities which are necessary for driving a motor vehicle. Every driver knows how crucial correct operation of the gearbox can be in difficult traffic situations. Pneumatic switching aids for commercial vehicles of all sizes can help here.

Pneumatic switching aids of this type are known in a resolved construction, which consist of a mechanical-pneumatic control part and a separate, pneumatic force part. A switching aid in a disassembled design is made of Loomann; Gear transmission; 2nd Edition; Springer Verlag; 1988; P. 225 known. The control part is a mechanically operated control valve which is actuated by the shift linkage. The transmission of the selection movement when changing gears is done mechanically directly to the transmission. When the switching movement is transmitted, the control valve is actuated and, at the same time, the manual switching force is transmitted mechanically to the transmission via a lever. The manual switching force is additionally pneumatically supported by a compressed air cylinder. This compressed air cylinder, as a two-position cylinder with an integrated hydraulic damper, forms the pneumatic power unit. A direct proportional representation of the manual switching force is not achieved here. The distances between the control section and the power section are long and the attachment is space-consuming. Damage to the compressed air lines between the control section and the power section cannot be avoided.

From DE-OS 22 23 881 a switching device is known which can be used for switching gear change transmissions of motor vehicles. A shift lever is connected to a control rod. The control rod is in the piston rod of a pneumatic power partly included, which has pistons pressurized on both sides. When the control rod is axially displaced, control valves can be actuated in the piston rod. The piston rod is connected to an adjusting device, when used to shift motor vehicle manual transmissions, generally to an adjusting fork for axially displacing a sliding sleeve of a synchronization. From this disclosure, no switching force exerted on the adjusting device as a function of the driver switching force is known. When the pressure chamber is vented, the inflowing compressed air flows out of the reservoir with a delay. Furthermore, it is not provided that mechanical actuation should still be possible if the compressed air supply fails for the switching device. The mechanical transmission of the manual shifting force is neither described nor evident from the drawing.

The invention is based on the object of developing the switching device in such a way that it is small and compact in an integrated design and is carried out by the driver

Transmits shifting force proportionally to the transmission. Previous shifting devices could not transmit a proportionality from the manual shift lever to the transmission. No matter how high the manual switching force was, the force generated by the switching device was always the same.

According to the invention, the object is achieved by a switching device with the features of claim 1. Embodiments are the subject of subclaims.

Previous shifting devices that supported the driver's shifting force exhibited either-or behavior on, a so-called black and white behavior. The full support of the servo force was given to the synchronizations. For this reason, all synchronizations had to be designed for the greatest possible load, ie the synchronizations were generally overdimensioned or the synchronizations had to endure constant overloads. The driver was able to continuously act on the gear lever for a longer period of time and thus overload synchronization. The switching device according to the invention exhibits a behavior of the supporting switching force which corresponds to the ratio of the driver's manual force introduced into the switching device. This provides the driver with such light support as he requests on the gear lever during his gearshift. If the driver shifts quickly or tears on the shift lever, the shift time in the transmission will also be correspondingly short.

In a switching device according to the invention, the control valve and the power part are combined in one component. The driver's shifting force is increased depending on the shifting force and acts in accordance with a manual transmission. The driver does not lose track of the gearshift, he can immediately feel whether he is in gear or how long the synchronization phase lasts.

According to the invention, the shifting movement of a transmission shifting device is to be assisted by compressed air as an assistant, while the selection movement is carried out by hand without assistance. The fact that only part of the gear change is supported by a servo force simplifies the construction of the switching device compared to full servo switching devices. Costs and installation effort are considerably reduced, and retrofitting from already installed gearboxes is also possible without any problems.

The driver can still switch manually if the air pressure should be too low due to damage in the compressed air system or should even fail completely. No switchover measures of any kind are required for this. The braking ability of the motor vehicle, provided that it is provided by the transmission, remains ensured.

The compressed air support contributes a large part of the force to be applied when shifting - but only so much that the driver retains the shift feeling. The manual force to be applied manually by the driver is reduced to a fraction of the total force required by a pneumatic switching aid. Synchronized

Commercial vehicle transmissions become light-duty transmissions even in heavy vehicles. When driving downhill, the downshifting of the gearbox, in particular in the lower gears, is made extremely easy and this makes a significant contribution to increasing accident safety.

The switching device according to the invention is used in all synchronous transmissions with an H circuit, a double H circuit and a superimposed H circuit. It also has sufficient space for mounting on the gearbox in the installation space that is very limited by the vehicle manufacturer. If a replacement or retrofitting is required, the Fall times are pleasantly short for the vehicle operator, since the entire switching device can be exchanged or assembled together without having to make any special settings on the vehicle. The switching path of the transmission can also be represented in a shortened manner by the arrangement of the switching device according to the invention. The shift path can be reduced for a standard transmission by appropriate design of the lever ratios in the shift linkage. The shorter shift travel has a positive effect on the shift lever for the driver.

The driver also has a constantly noticeable feedback on the shift sequence in the transmission during the shifting process. As with a mechanical and unsupported shifting device, the driver feels the reaction of the transmission via the mechanical connection between the shift lever and the synchronization in the transmission. This means that the operator can always intervene in the switching process and can cancel the switching process in progress at any time. In the event of a failure of the compressed air support, the driver remains unrestricted in the shiftability of the transmission, so that in emergencies he can brake the vehicle, probably with increased effort, but surely, by changing the gear ratio.

By means of an appropriate design of the shifting device, the auxiliary forces generated by it can be adapted to support the shifting to the switchgear between driver and transmission. The look-up effects which can be felt in the pneumatic switching devices during the transition from the unlocking process to the free flight phase are eliminated or are compensated for by the switching device. In contrast to previous switching devices is ensured by a quick ventilation that in the event of an aborted shift sequence, there is no longer any pressure in the shifting device which could undesirably accelerate the entire shifting system as far as the shift lever and could cause this look-up effect. The

Switching device is completely depressurized when the switching sequence is interrupted.

Due to the proportionality between the manual switching force and the force emitted by the switching device, the manual switching force is only slightly supported if necessary. The overall system is not unnecessarily accelerated, as is the case with disproportionately reinforced devices. The integrated structure of the switching device creates small volumes, short direct routes and thus short filling times. A quick reaction of the components is also achieved due to small masses.

The invention is explained in more detail with reference to figures. Show it:

1 shows a switchgear;

Fig. 2 shows a section of the switching device and

Fig. 3 shows a section according to Fig. 2 in an enlarged view.

1 shows a sketch of the switchgear assembly 2 of a motor vehicle. From a shift lever 4, a shift rod 6 leads via a lever deflection 8 to a switching device 10. The switching device 10 has a connecting line 12 which leads to a storage container 14 leads from which the switching device 10 is supplied with compressed air. The lever deflection 8 has a first lever 16, which is preferably connected in an articulated manner to the shift rod 6. The lever deflection 8 has a second lever 18, which in turn engages in a control rod 20 which is arranged in the switching device 10. Furthermore, a piston rod 22 is provided in the switching device 10, into which a lever 24 engages, which is connected via a rotary shaft 26 to a lever 28 in the vehicle transmission 30. The lever 28 engages in one

Shift rail 32, through which gear ratios of the transmission can be switched in a known manner. A movement of the lever 24 is transmitted via the rotary shaft 26 into a movement of the lever 28, so that the lever 28 can cause the shift rail 32 to move axially. During this movement, the shift rail 32 preferably occupies three positions, two axial end positions, each of which corresponds to a switched transmission ratio, and a middle position lying between the end positions, which corresponds to a neutral position of the transmission.

FIG. 2 shows a sectional illustration of the switching device 10 according to the invention. FIG. 3 shows an enlarged section of the illustration according to FIG. 2. As shown here, the switching device 10 can be inserted in a part of the transmission 30, or it is separately outside arranged on the housing. The lever 18 is connected via the rotary shaft 16 to the shift linkage, not shown here. About this shift linkage, the lever 18 from

Driver moves. In the axial continuation of the shaft 16, the rotary shaft 26 is provided, via which the lever 24 with interacts further components of the transmission not shown here.

The lever 18 engages in the control rod 20, which is located within a piston rod 22. The control rod 20 has an axial bore 36 from which radial openings 38, 40, 42, 46, 48 extend. The control rod 20 has a preferably circular cross section. At the respective axial position, the openings can also be distributed on the circumference of the control rod 20, differently than shown here in each case offset by 180 °. More than two openings are also possible at the respective axial position. The axial opening 36 ends at one end in the control rod 20 and is closed at its opposite end by a screw connection 50. A slide bearing 52 for the control rod 20 is provided within the piston rod 22. Furthermore, the control rod 20 is supported within the piston rod 22 by a cutting disc 58. A disc 54 has a sealing ring 56 which surrounds the control rod 20. Two disks 60 and 62 are also arranged on the control rod 20. The cutting disc 58 has at least one opening 64, the discs 60 and 62 each have at least one opening 66 and 68, respectively. An annular space 72 is formed between the two disks 60 and 62, the control rod 20 and a ring 70. The two disks 60 and 62 are displaceably arranged on the inner wall of the ring 70. The two disks 60 and 62 are held axially apart by a spring 74 arranged between them. The arrangement of the disks 60, 62 and the spring 74 serves to support and fix the manual shift lever.

The openings 66 and 68 ensure that there is none in the annular space 72 between the disks 60 and 62 forms undesirable pressure. The axial mobility of the disk 62 is limited on the one hand by the spring 74 and on the other hand by a disk 76. On the one hand the ring 70 is axially connected to the disk 76 and on the other side a locking ring 78 which is arranged inside the piston rod 22. The ring 70 is axially delimited on its other side by a control valve ring 80, which in turn abuts the cutting disc 58. The control valve ring 80 is arranged radially inside the piston rod 22. A space formed between washer 62, screw connection 50 and housing 116 is vented to the surroundings through an opening 77.

In the area of the control valve ring 80, the control rod 20 is surrounded by a ring 82 which has openings 84, 86, 88 and 90. The openings 84, 86, 88, 90 each correspond to the openings 40, 42, 46 and 48 in the inner control rod 20. Between the ring 82 and the control valve ring 80, two axially displaceable actuating pistons 92 and 94 are provided. The ring 82 is delimited by discs 83 and 85 at its axial ends. Disc 83 abuts an edge of control rod 20 and disc 85 is held on control rod 20 by a locking ring 87. The locking ring 87 likewise holds the washer 60 via a ring 89 arranged between the washer 60 and the securing ring 87.

The actuating pistons 92 and 94 have lugs 96 and 98, respectively. Also axially displaceable are two valve actuators 100 and 102 on the ring 82, which are held apart in the axial direction by a spring 104.

The valve disks 100 and 102 lie close to control edges 106 and 108, which lie radially inside the control valve ring 80 and are axially on the one hand by this control valve ring 80 and on the other hand are limited by retaining rings 110 and 112, respectively. Depending on the actuation of the control rod 20 by the driver, the compressed air flowing in between the control edge 106, 108 and the valve plate 100, 102 generates a correspondingly proportional counterforce to the manual switching force on the actuating pistons 92, 94. Correspondingly, the respective pressure chamber 118, 120 fills and accordingly the piston rod 22 and thus the shift rail 32 also shift. Reactions from the transmission to the shift rail 32 are transferred back in a corresponding manner, ie depending on how strongly from the pressure chamber 118 , 120 is pressed back onto the contour of the actuating piston, this pressure is also transmitted via the control rod 20 to the shift lever 4 and thus to the driver's hand. The shift sequence with the characteristic shift points, for example synchronous phase, shift phase, determining that gear is engaged, can still be felt by the driver. He therefore also receives information feedback through high synchronous forces in the event of incorrect switching attempts. The switching sequences can be corrected or canceled at any time.

Radially outside the piston rod 22, a piston 114 divides the annular space between the housing 116 of the switching device 10 and the piston rod 22 into two pressure chambers 118 and 120. The piston 114 is communicated by disks 122, 123 and locking rings 124, 125 the piston rod 22 connected. The housing 116 has an opening 126 which is connected to the connecting line 12 for the supply of compressed air from the storage container 14. The piston 114 has radially extending openings 134 which, in the central position of the switching device 10, have the opening 126 in the housing 116 and also openings 136 in the piston rod 22 and openings 138 in the control valve ring 80 correspond. The piston rod 22 has further openings 140, which correspond to openings 142 in the control valve ring 80. An annular space 144 formed between control rod 20, piston rod 22, disk 54 and cutting disk 58 has an opening 146 which leads to a further annular space 148. The annular space 148 is formed between the housing 116 and the piston rod 22 and is connected to the outside environment via an opening 150.

The number of openings 134, 136, 138, 140, 142 and 146 is not limited to the number of two openings shown here in each case, but a plurality of openings can in each case be distributed around the circumference of the respective component having the openings.

From the central position of the switching device 10, the control rod 20 is moved axially when the switching lever 4 is actuated by the driver via the switching rod 6 and the levers 16 and 18, for example to the right in the plane of the drawing. In the middle position of the switching device 10, the pressure chamber 120 is connected to the outside environment via the openings 140, 142, 90, 48, 38, 146 and 150 and is thus vented. If the control rod 20 is now shifted to the right, the actuating piston 92 abuts the valve plate 100 with the lug 96 and also shifts it away from the control edge 106 to the right. As a result, compressed air can get from the storage container 14 via the connecting line 12 and through the openings 126, 134, 136 and 138 past the nose 96 of the actuating piston 92 and further through the openings 142 and 140 into the pressure chamber 118 the compressed air moves piston 114 to the right. The piston 114 moves using Disc 122 and the retaining ring 124 also move the piston rod 22 to the right. The piston rod 22 actuates the lever 24 and thus the lever 28 via the rotary shaft 26. The lever 28 displaces the shift rail 32 in the vehicle transmission in such a way that the neutral position is shifted into one gear. The pressure build-up takes place very quickly and without delay through correspondingly large openings in the entire switching device 10, which should not perform any throttling functions.

By moving the piston rod 22 to the right, the nose 96 of the actuating piston 92 is released again from the valve plate 100 and is essentially replaced by the inflowing compressed air with the support of the

Spring 104 pushed back to the control edge 106. The pressure chamber 118 is vented through the openings 140, 142 past the nose 96 of the actuating piston 92 through the openings 88, 46 into the bore 36 of the control rod 22 and from there through openings 38, 146 and 150 to the outside environment . Due to the correspondingly large cross sections of the openings, this ventilation is also carried out very quickly.

If the gear opposite in the shift gear is now to be shifted, the control rod 20 is shifted axially to the left in the plane of the drawing from the right position of the shift device 10 when the driver actuates the shift lever 4 via the shift rod 6 and the levers 16 and 18 . The actuating piston 94 abuts the valve plate 102 with the lug 98 and also shifts it away from the control edge 108 to the left. This allows compressed air from the storage container 14 via the connecting line 12 and through the openings 126, 134, 136 and 138 past the nose 98 of the actuating piston 94 and further through the openings 142 and 140 into the pressure chamber 120. There, the compressed air moves the piston 114 to the left. The piston 114 also displaces the piston rod 22 to the left with the aid of the disk 123 and the locking ring 125. The piston rod 22 in turn actuates the lever 24 and thus the lever 28 via the rotary shaft 26. The lever 28 shifts the shift rail 32 in the vehicle transmission in such a way that from one gear to the gear opposite in the shift gate is switched. The movement of the piston rod 22 to the left releases the nose 98 of the actuating piston 94 again from the valve plate 102 and this is pressed back against the control edge 108. The pressure chamber 120 is vented via the openings 140, 142 past the nose 98 of the actuating piston 94 through the openings 90, 48 into the bore 36 of the control rod 22 and from there through openings 38, 146 and 150 to the outside environment. Due to the correspondingly large cross-sections of the openings, this venting also takes place very quickly.

The entire switching device is flow-optimized. There is no throttling of air flows at the existing openings. This leads to quick ventilation and quick ventilation of the pressure rooms.

If the compressed air fails, the gearbox can be shifted like an unsupported gearbox. The manual shifting force of the driver is transmitted to control rod 20 via shift lever 4, shift rod 6, levers 16 and 18. The control rod 20 moves the actuating piston 92 to the right in the case of a movement to the right in the plane of the drawing. The nose 96 abuts the valve plate 100. Depending on the design of the springs 104 and 74, the piston rod 22 is also moved to the right either via the valve plate 102, control edge 108, locking ring 112, control valve ring 80, ring 70, washer 76 and locking ring 78 or by locking ring 87, ring 89 , Washer 60, spring 74, washers 62 and 76 and locking ring 78. The switchability is thereby ensured mechanically without interruption.

If the required manual switching force exceeds the

Spring forces of the springs 104 and 74, a positive connection can be achieved by a device, not shown here, between the lever deflection 8 and the rotary shaft 26.

Essentially, all components can be provided as turned parts that are simple and inexpensive to manufacture. Injection molded plastic parts can also be used for different components for reasons of cost, for improved tightness, and to avoid corrosion. This enables the switching device according to the invention to be offered as a compactly constructed and cost-effective finishing part and retrofitting part.

Reference sign

2 switchgear

4 shift levers

6 shift rod

8 lever deflection

10 switching device

12 connecting cable

14 storage containers

16, 18 levers

20 control rod

22 piston rod

24 levers

26 rotary shaft

28 levers

30 vehicle transmissions

32 shift rail

36 - 48 opening

50 screw connection

52 plain bearing

54 disc

56 sealing ring

58 cutting disc

60, 62 disc

64 - 68 openings

70 ring

72 annulus

74 spring

76 disc

77 opening

78 circlip

80 control valve ring 82 ring

83, 85 disc

84 - 90 openings

87 circlip

89 ring

92, 94 actuating piston

96, 98 noses

100, 102 valve disc

104 spring

106, 108 control edge

110, 112 circlip

114 pistons

116 housing

118, 120 pressure room

122, 123 disc

124, 125 circlip

126 - 142 openings

144 annulus

146 opening

148 annulus

150 opening

Claims

Patent claims

1. Switching device (10), in particular for gear change transmissions of motor vehicles, with an axially displaceable control rod (20) which interacts via a shift linkage (6, 8, 16, 18) with a shift lever (4) and is located within a piston rod (22) is provided with a piston (114) which can be pressurized with pressure medium on both sides, the piston rod (22) interacting with means (24, 26, 28, 32) for shifting the gear change transmission, and in the case of an axial adjustment the Control rod (20) in the piston rod (22) control valves (100, 102, 106, 108) can be actuated, characterized in that the

Control rod (20) actuating pistons (92, 94) can be activated, which have a switching force exerted on the control rod (20) via shift lever (4) and shift linkage (6, 8, 16, 18) via the piston rod (22) on the means (24 , 26, 28, 32) for switching the gear change transmission.

2. Switching device (10) according to claim 1, characterized in that the actuating pistons (92, 94) are arranged within the piston rod (22).

3. Switching device (10) according to claim 1 or 2, da¬ characterized in that on the control rod (20) a first disc 60, a second disc (62) and an intermediate spring (74) an annular space ( 72) form for fixing the shift linkage (6, 8, 16, 18).

4. Switching device (10) according to one of claims 1 to 3, characterized in that the openings (36 - 48, 64 - 68, 77, 84 - 90, 126 - 142, 146, 150) of the switching device (10) so large designed diameter that the pressure medium can pass through the openings without throttling.

5. Switching device (10) according to one of claims 1 to 4, characterized by the fact that daε

Gearbox via the shift lever (4), the shift linkage (6, 8, 16, 18), the control rod (20), the piston rod (22) and the means (24, 26, 28, 32) if the pressure medium fails can be switched.

6. Switching device (10) according to any one of claims 1 to 4, characterized in that daε transmission via the shift lever (4), daε Schaltgeεtänge (6, 8, 16), rotary shaft (26), a device for forming a form-locking between lever deflection (8) and rotary shaft (26) and the means (28, 32) can be switched manually if the pressure means fails.