GB2335010A

GB2335010A - Gear synchronizing unit

Info

Publication number: GB2335010A
Application number: GB9804737A
Authority: GB
Inventors: Hans Juergen Schmitz
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-03-05
Filing date: 1998-03-05
Publication date: 1999-09-08
Also published as: GB9804737D0

Abstract

A single gear synchronizing unit provides an engageable link between the output shaft [6] and the input [8] or lay shaft of a manual gearbox, manual range speed gearbox and/or manual power transfer gearbox for the purpose of synchronization of all forward and reverse gears. The electronic module computes signals from speed sensors at the output shaft [18] and the input [19] or lay shaft, and from a gear shift position sensor to calculate the required speed of the input shaft [8] or lay shaft to enable synchronized gear engagement. The input shaft [8] or lay shaft is accelerated when the solenoid-controlled clutch [10] is activated, slowed down when the solenoid-controlled brake [16] is activated, and its rotation reversed when the solenoid-controlled clutch [13] is activated. A solenoid-controlled gear shift control mechanism controls the effort required to move the gear shift lever and prevents harsh gear engagement prior to complete synchronization.

Description

1 2335010 1 GEAR SYNCHRONIZING UNIT This invention relates to a gear

synchronizing unit for all forward and reverse gears of a manual gearbox, manual range speed gearbox, manual power transfer gearbox or any combination of such gearboxes as fitted to a passenger car, off-road, competition, commercial, agricultural, industrial or military vehicle.

is Conventional manual gearboxes provide different transmission ratios to make th e best use of engine torque throughout the vehicle's speed range. Manual range speed gearboxes work in addition to manual gearboxes to provide a means to alter the overall transmission ratio. Manual power transfer gearboxes provide a means to transmit power to axles which are not permanently driven and possibly to change the transmission ratio to all driven axles, or to transmit power to power take-off shafts which drive equipment not involved in propelling the vehicle.

Conventional manual gearboxes, manual range speed gearboxes or manual power transfer gearboxes can be of a two-shaft design comprising an input shaft and an output shaft with the constantly meshing gear pairs which provide the different gear ratios being situated on these shafts, or of a three-shaft design comprising an input shaft, a lay shaft and an output shaft, with the constantly meshing gear pairs which provide the different gear ratios being situated on the lay shaft and output shaft. The latter is commonly referred to as the main shaft. In the twoshaft design power input and output are offset, in the threeshaft design power input and output are concentric. Variations are possible and can benefit from this invention.

The power flow from the engine to the input shaft of manual gearboxes, manual range speed gearboxes or manual power transfer gearboxes goes through a disengageable clutch, whereas the output 2 is shaft is permanently connected to all or at least some of the vehicle's driven road wheels or tracks. The engagement of a forward or reverse gear from the neutral position with the clutch disengaged, typically but not necessarily while the vehicle is at a standstill, is at the start of every drive cycle. Changes in the overall transmission ratio are effected while the clutch is disengaged and the input shaft is disconnected from the engine. In all four modes of gear change, i.e. engagement of a gear from neutral, reduction or increase of the overall transmission ratio, and reversal of the direction of rotation, the task of gear synchronization is to accelerate or slow down the input shaft or lay shaft so that their speed and direction of rotation coincides with the arithmetic product of the speed of the output shaft and the ratio of the desired gear.

In conventional manual gearboxes, manual range speed gearboxes or manual power transfer gearboxes, individual freewheeling gear wheels or pairs of adjacent freewheeling gear wheels are coupled to a synchronizer assembly. During gear engagement or a gear change and while the clutch pedal is being depressed by the vehicle driver or the automatic clutch is disengaged through a signal from the gear shift lever knob sensor, a dedicated friction element known as a synchronizer ring in the synchronizer assembly synchronizes the speed of the gear wheel with the speed of the shaft, until a dog clutch can positively lock the gear wheel with the shaft. In the case of unassisted gear shift mechanisms the vehicle driver delivers the force required for the synchronization.

The operating conditions in conventional manual gearboxes, manual range speed gearboxes or manual power transfer gearboxes vary considerably. At low gearbox temperatures, the pre-load of taper roller bearings and/or the high viscosity of the lubricant lead to a high turning force of gearbox shafts. Urban traffic conditions can delay the warm-up period of gearboxes, but still 3 require frequent gear changes. Under these conditions, conventional synchronizer assemblies can be put under severe strain, with the result of accelerated wear of the friction elements.

Some conventional manual gearboxes, manual range speed gearboxes or manual power transfer gearboxes feature double synchronization for certain gear wheels, where two friction elements contained in one synchronizer assembly and separated by an intermediate ring significantly enlarge the effective friction area, albeit within the dimensional restrictions imposed by the diameter of the gear wheel. Although this arrangement reduces wear of the friction elements, in the case of unassisted gear shift mechanisms the driver still has to apply increased force on the gear shift lever is to effect the synchronization and subsequent gear change under adverse operating conditions.

Some conventional manual gearboxes feature a braking mechanism which is activated when the reverse gear is being engaged. The braking mechanism aims to achieve quiet engagement of the reverse gear by braking the freewheeling gear wheel. The braking mechanism does not synchronize the reverse gear but attempts to stop the gear wheel without taking into account that the vehicle could still be in motion. This type of braking mechanism does not contribute to the synchronization of the forward gears either.

Synchronization of gears in conventional manual gearboxes, manual range speed gearboxes and manual power transfer gearboxes adds significantly to the manufacturing cost because each synchronized gear wheel requires accurate machining of a tapered friction area and one matched synchronizer ring, or possibly two synchronizer rings and an additional intermediate ring in the case of double synchronization. In addition, a finely machined and expensively assembled synchronizer assembly, often shared with another gear wheel, is necessary. The f orces that have to be transmitted 4 is through the gear shift mechanism and the selector forks require all components involved to be very strong and therefore heavy. Failing synchronization leads to substantial after-sales warranty/goodwill costs for repairs to or replacement of conventional manual gearboxes, manual range speed gearboxes and manual power transfer gearboxes, not least because this type of fault becomes immediately audible to the driver.

Repairs to the synchronization of gears in conventional manual gearboxes, manual range speed gearboxes and manual power transfer gearboxes necessitate the removal and disassembly of the gearbox housing, and the disassembly of the shaft on which the faulty synchronizer assembly is located.

Synchronization of gears in conventional manual gearboxes, manual range speed gearboxes and manual power transfer gearboxes is still a purely mechanical process. None of the vehicle operating data available from sensors used in modern engine management systems is exploited for the electronic management of manual gearboxes, manual range speed gearboxes and manual power transfer gearboxes to achieve true powertrain management.

The present invention addresses the need for one gear synchronizing unit for all forward and reverse gears of a manual gearbox, manual range speed gearbox, manual power transfer gearbox or any combination of such gearboxes, which omits the requirement for a synchronizer ring and corresponding accurately machined tapered friction area on each synchronized gear wheel and a separate synchronizer assembly for each synchronized gear wheel or pair of adjacent gear wheels. In addition, the gear synchronizing unit described in the present invention addresses the need to enhance gear shift comfort, to reduce the force required by the driver to effect gear changes, particularly under adverse operating conditions, and to keep the effort constant irrespective of gearbox operating conditions.

The present invention also addresses the need for a gear synchronization mechanism which can be calibrated electronically without mechanical intervention to compensate for manufacturing tolerances of synchronization components and gear shift actuating elements, and which can compensate for changes in operating conditions and mechanical wear. Additionally, the present invention addresses the need for a gear synchronization mechanism which can be removed, repaired or renewed and fitted without the complete disassembly of the manual gearbox, manual range speed gearbox or manual power transfer gearbox, and depending on installation constraints of individual applications even without the removal of the gearbox, range speed gearbox or power transfer gearbox itself.

is Furthermore, the present invention addresses the need for reductions in manufacturing and warranty/goodwill costs by using one synchronization unit for all forward and reverse gears, in gearbox weight by allowing for weaker and therefore lighter gear shift mechanism components and selector forks, and in overall gearbox dimensions by allowing for the installation of simplified dog clutches. Finally, the present invention addresses the need for a manual gearbox, manual range speed gearbox and/or manual power transfer gearbox which becomes part of a comprehensive electronic powertrain control system, thereby both contributing to and benefitting from the flow of electronic data concerning vehicle operating conditions at any given moment.

Accordingly, the present invention provides a single gear synchronizing unit for all forward and reverse gears of a manual gearbox, manual range speed gearbox and/or manual power transfer gearbox. The gear synchronizing unit comprises a solenoid-operated brake, two solenoid- operated clutches, a planetary gear and a set of auxiliary gears.

6 In the case of hydraulically assisted gear shift mechanisms, the hydraulic circuits of the gear synchronizing unit's brake and two clutches are controlled by solenoids, as is common practice on automatic transmissions.

is The gear synchronizing unit can be installed directly on the output, input or lay shaft of the gearbox, range speed gearbox or power transfer gearbox and manipulate the two shafts it links through auxiliary gears on these shafts. As an alternative in order to improve the unit's accessibility or to reduce the overall length of the gearbox, the gear synchronizing unit can be installed on an auxiliary shaft and manipulate auxiliary gears on the two shafts it links through its auxiliary gears. Such a gear train could be enlarged by any number of idler gears to achieve the most desirable installation position for the gear synchronizing unit.

As an alternative to meshing auxiliary and idler gears, sprockets and chains can be used to link the gear synchronizing unit with the relevant shafts.

The electronic module of the gear synchronizing unit's closedloop control system receives an activation signal from a clutch pedal switch or, in the case of an automatic clutch, a signal from the gear shift lever knob sensor, whereupon a gear shift lever position sensor or gear shift position sensor provides a unique, progressively changing resistance value for every possible shift lever position to monitor driver's intentions. Further signals come from speed sensors on the input shaft and output or lay shaft and from a lubricant temperature sensor in order to take temperature-dependent variations in turning forces into account.

The electronic module of the gear synchronizing unit's closed- loop control system emits a signal to a solenoid-operated gear 7 shift gate brake or gear shift lever brake which controls the effort required to move the gear shift lever and which can additionally lock the gear shift lever or selector finger when a gear is engaged and the clutch pedal or the gear shift lever knob sensor is released. Other outputs are the clutches and the brake in the gear synchronizing unit with which the shaft speeds are synchronized according to the desired transmission ratio.

The electronic module of the gear synchronizing unit's closed- loop control system compares the signal from the gear shift lever position sensor or gear shift position sensor and the signals from the speed sensors on the input shaft and output or lay shaft with stored transmission ratio information. Based on this information the electronic module energizes one of the clutches is or the brake in the gear synchronizing unit until the required synchronization of shaft speeds has been achieved. Simultaneously the electronic module energizes the solenoid-operated gear shift gate brake or gear shift lever brake to control the effort required to move the gear shift lever in order to avoid unsynchronized gear engagement. In order to react quickly and effectively to signal changes, the clutch and brake solenoids can be energized by digitally pulse-width modulated voltage or an analog variable control current.

The invention may be further illustrated, by way of example, with reference to the drawings described below, in which:- Figure 1 shows the gear synchronizing unit directly connected to the input and output shafts of a two-shaft gearbox, range speed gearbox or power transfer gearbox.

Figure 2 shows the gear synchronizing unit directly connected to the lay shaft and 'output shaft (main shaft) of a three-shaft gearbox, range speed gearbox or power transfer gearbox.

8 Figure 3 shows the gear synchronizing unit offset from the plane of the shafts of a gearbox, range speed gearbox or power transfer gearbox and comprising two auxiliary gears and one auxiliary shaft.

1 30 1 Figure 4 shows the gear synchronizing unit offset from the plane of the shafts of a gearbox, range speed gearbox or power transfer gearbox and comprising two auxiliary gears, one auxiliary shaft and one idler gear.

Figure 5 shows the components of a gear synchronizing unit in exploded view.

Figure 6 shows the gear shift lever position sensor for a biaxial gear shift mechanism.

Figure 7 shows the solenoid-operated gear shift gate brake for a biaxial gear shift mechanism.

Figure 8 shows the combination of gear shift lever position sensor and solenoid-operated gear shift gate brake to one assembly for a biaxial gear shift mechanism.

Figure 9 shows the gear shift position sensor and the solenoid-operated gear shift lever brake for a sequential gear shift mechanism.

Figure 10 shows the combination of gear shift position sensor and solenoid-operated gear shift brake to one assembly for a sequential gear shift mechanism.

Figure 11 shows spring-loaded rollers for optional installation between freewheeling gear and dog clutch.

Figure 12 shows clutch discs and solenoids in a. special execution 9 to enable electronically controlled rotation of the gear synchronizing unit.

Referring to the drawings, an auxiliary gear [1 or 211 is integrally linked with the annulus [21 of a planetary gear of which [31 is the sun wheel and [4] are the planet gears. This assembly is located on a bush or roller bearing [51, which allows freewheeling and axial movement on the output shaft [61 or lay shaft [231 of the gearbox, range speed gearbox or power transfer gearbox. The auxiliary gear 11 or 211 meshes with a second auxiliary gear [7 or 221 which is locked to the input shaft [81 or output shaft [241 of the gearbox, range speed gearbox or power transfer gearbox.

is A solenoid [91 receives voltage from the electronic module according to synchronization requirements. When the solenoid [91 is energized, it draws the auxiliary gear [1 or 211 against the friction lining of a clutch disc [101. A circlip [111 restricts the axial movement of the clutch disc [101 and the auxiliary gear [1 or 211 towards the solenoid 191 in order to prevent contact between the rotating clutch disc [101 and the stationary solenoid [91. The clutch disc is splined to the output shaft [61 or lay shaft [231. When the solenoid [91 is energized, the clutch disc [101 connects the output shaft [6] or lay shaft [231 to the auxiliary gear [1 or 211. The auxiliary gear [11 then drives the input shaft [81 through the second auxiliary gear [71 in the forward direction of rotation, or the second auxiliary gear [221 then drives the lay shaft [231 through the auxiliary gear [211 in the forward direction of rotation. The transmission ratio of the two auxiliary gears [1 and 7, or 21 and 22] is chosen in such a way that the input shaft [81 or lay shaft [231 can be accelerated to any speed required for effective synchronization of the desired forward gear by controlling the solenoid activation pulse- width or current intensity.

A second solenoid [12) also receives voltage from the electronic module according to synchronization requirements. When the second solenoid [121 is energized, it draws the sun wheel [3] against the friction lining of a second clutch disc [131. A second circlip [141 restricts the axial movement of the second clutch disc [131 and the sun wheel [31 towards the second solenoid [121 in order to prevent contact between the rotating clutch disc [131 and the stationary solenoid [121. The second clutch disc is also splined to the output shaft [61 or lay shaft [231. When the solenoid is energized, the clutch disc [131 connects the output shaft [61 or lay shaft [231 to the sun wheel [31. The sun wheel [31 then drives the auxiliary gear [11 through the planet gears [41 and the integral annulus [21 against the direction of rotation of the forward gears, or the sun wheel [31 then connects the auxiliary gear [211 through the planet gears [41 and the integral annulus [21 to the lay shaft [231 and reverses the latter's direction of rotation. The auxiliary gear [11 then drives the input shaft [81 through the second auxiliary gear [7) against the direction of rotation of the forward gears, or the second auxiliary gear [221 then drives the lay shaft [231 through the auxiliary gear [211 against the direction of rotation of the forward gears. The transmission ratio of the planetary gear and the two auxiliary gears [1 and 7, or 21 and 22] is chosen in such a way that the input shaft or lay shaft caLn be accelerated to any speed required for effective synchronization of the reverse gear by controlling the solenoid activation pulse-width or current intensity.

A third solenoid [151 also receives voltage from the electronic module according to synchronization requirements. When the third solenoid [151 is energized, it draws a brake pad or brake band [161 against a suitable surface of the auxiliary gear [11, for instance the outer diameter of the integral annulus [21, or against a suitable surface of a component positively engaged with the lay shaft, for instance the outer friction ring [251 on a 11 clutch disc [131. When the third solenoid [151 is energized, the freewheeling auxiliary gear [11 brakes the auxiliary gear [71, or the brake band [161 brakes the clutch disc [131. The auxiliary gear [1] then brakes the input shaft [81 through the second auxiliary gear [71, or the clutch disc [131 then brakes the lay shaft [231 directly, to any speed required for effective synchronization of the desired gear, by controlling the solenoid activation pulse-width or current intensity.

The gear synchronizing unit is contained in a separate housing [17] which is flanged to the housing of the gearbox, range speed gearbox or power transfer gearbox. Where the gear synchronizing unit is directly connected to the input shaft or lay shaft and output shaft, an access cover [181 provides access to the second circlip [141. After removal of this circlip and the housing fasteners, the complete gear synchronizing unit can be eased off the input shaft [61 or lay shaft [231 and the housing 1171 can be removed from the gearbox, range speed gearbox or power transfer gearbox. With the housing [171 removed the second auxiliary gear [7) becomes accessible.

The electronic module receives a signal from an output shaft speed sensor [191 and a signal from an input shaft speed sensor [201 or lay shaft speed sensor [261. The inductive speed sensors can be triggered by the teeth of any of the gear wheels on the input and output shafts, provided that the gear wheels selected for this additional function are permanently locked to their respective shafts, or alternatively suitable trigger wheels can be fitted to the input and output shafts.

The gear synchronizing unit can be offset from the plane of the shafts [28 and 291 with the constantly meshing gear pairs (input shaft and output shaft or output shaft and lay shaft). In this arrangement the gear synchronizing unit is situated on an auxiliary shaft [271 which runs in bearings in a separate housing 12 [171 which is f langed to the housing of the gearbox, range speed gearbox or power transfer gearbox. The gear synchronizing unit uses a freewheeling auxiliary gear [301 in the way described above and a splined auxiliary gear. [311 to provide the necessary connections to the gearbox shafts [28 and 29] through two auxiliary gears [32 and 331 which are splined to their respective shafts. One [341 or more idler gears can be included in the gear train to increase the offset of the gear synchronizing unit from the gearbox shafts. The overall number of gears in such a gear train determines the assignment of the first and second clutch solenoids [9 and i21; if the number is uneven, synchronization of forward gears is effected by the second (planetary gear) solenoid [121 and the reversal of the direction of rotation of the input shaf t or lay shaf t is ef f ected by the f irst solenoid [91, and is vice versa if the number is even.

In the case of a biaxial gear shift mechanism, the electronic module receives a signal from a gear shift lever position sensor [351. The sensor is an integral part of the gear shift gate. In the case of remote gear shifting the gear shift gate can be situated around the gear shift lever, thereby necessitating a spherical sensor surface [361, or in the gear shift mechanism inside the gearbox, range speed gearbox or power transfer gearbox, thereby necessitating a curved sensor surface [371. A spring-loaded wiper ring [381 is installed on the gear shift lever [391 or gear shift gate follower [401 and slides on a set of resistance tracks [411 which connect to resistors [42] at each of their respective ends. The resistance values of the individual resistors [421 differ substantially from each other. The gear shift lever position sensor's electrical circuit consists of reference voltage supplies [431 to a resistor at one end of each resistance track [411 and a return through the other resistor, for instance through a ground connection [441. The wiper ring [381 of the gear shift lever position sensor picks up a unique voltage for every possible shift lever position. The voltage 13 changes progressively while the gear shift lever is moved along the neutral selection axis 'X' where the wiper ring [38] connects to at least two circuits in parallel. When the gear shift lever is moved away from the neutral selection axis 'X' along the gear shift axis 1Y1, the parallel connection to two or more circuits seizes and the wiper ring only connects to one circuit, thereby picking up a significantly different but equally unique voltage.

The gear shift gate brake or gear shift lever brake [451 for a biaxial gear shift mechanism sits on the gear shift lever [391 or gear shift gate follower [401. A solenoid [461 is situated around the gear shift lever [391 or gear shift gate follower [401 and is secured with two circlips [471. A sleeve [481 shrouds the solenoid and is held by a spring [491 against a circular bump stop [501. At its extremity adjacent to the gear shift gate [36/371, the sleeve contour [51] matches the contour of the gear shift gate. When the solenoid [461 is energized, the integral sleeve armature [521 is drawn towards the solenoid. The sleeve [481 is then pushed against the gear shift gate [36/371, thereby braking the progress of the gear shift lever [391 or gear shift gate follower [401. The level of resistance to the driver's movement of the gear shift lever is determined by the pulse-width modulated voltage or the analog control current which the electronic module sends to the solenoid.

In the case of a sequential gear shift mechanism, the electronic module receives a signal from a gear shift position sensor [531 The sensor is a potentiometer which is fixed to a stationary bracket [541, while the potentiometer shaft [551 is linked to the rotary gear shift gate [561. The gear shift lever [571 actuates the gear shift gate through cables and a ratchet and pawl mechanism. The gear shift lever brake solenoid [581 is attached to the gear shift lever bracket [591. When the solenoid is activated, it pulls the gear shift lever [571 against its lateral friction surface [601. Alternatively, a solenoid- operated gear 14 shift brake [611 acts directly on the rotary gear shift gate. In both cases, the solenoid regulates the resistance of the gear shift lever to the driver's movement as a function of the pulsewidth modulated voltage or the analog control current it receives from the electronic module.

is Where it proves- necessary to assist the clutches and brake of the gear synchronizing unit in ensuring smooth gear engagement, rollers [621 held in leaf springs [631 can be mounted to the splined dog clutch [64). The leaf springs [631 have elongated holes [65] where they are fixed to the dog clutch [641 to allow for radial displacement during load changes. In the neutral position [66), the rollers clear the freewheeling gear wheel [671. When the dog clutch [641 is moved towards the gear wheel in the first stage of gear engagement [681, the rollers [621 begin to engage frictionally in a wavy track [691 in the gear wheel [67), thereby starting to accelerate or brake the gear wheel to the speed of the dog clutch. A recess [70] in the dog clutch allows for movement [711 of the rollers [621 along the radius described by the tip of the leaf springs [631. As the frictional engagement of the rollers in the wavy track gradually synchronizes the speed of the dog clutch and the speed of the gear, the force of the leaf springs [631 turns the frictional engagement of the rollers into a positive engagement [721, until the dog clutch can engage in the corresponding recesses in the gear wheel [731.

The electronic module and its associated sensors and actuators link and overlay two control circuits into one closed-loop control system which compares stored information with actual sensor signals and accordingly calculates outgoing signals to actuators. The first control circuit consists of the speed sensors on input [201 or lay shaft [261 and output shaft [191 and the gear synchronizing unit's solenoid- activated brake [15/161 and solenoid- activated clutches [9/10 and 12/131. The second is control circuit consists of the gear shift lever position sensor [351 or gear shift position sensor [531 and the gear shift gate brake or gear shift lever brake 145/581.

In all four modes of gear change, the closed-loop control system is initially activated by a signal from a clutch pedal switch or, in the case of an automatic clutch, a signal from the gear shift lever knob sensor.

The first mode of gear change is the engagement of a forward or reverse gear from neutral. Depression of the clutch pedal or activation of an automatic clutch separates the input shaft [81 (and therefore the lay shaft [231 in a three-shaft gearbox) from the engine. To enable synchronized engagement of a gear, the is input shaft [81 or meshing input shaft [81 and lay shaft [231 need to be slowed down. At the same time, the progress of the gear shift lever needs to be controlled to prevent harsh (unsynchronized) gear engagement. The electronic module therefore energizes the third solenoid [151, which activates the brake pad 20 or brake band [161, and it activates the gear shift gate brake or gear shift lever brake [45/581. The brake pad or band [161 slows down the input shaft [81 through the auxiliary gears [1 and 71, or it slows down the lay shaft [231 through the outer friction ring [251 on the splined clutch disc [131. When the signals from the speed sensors on the gearbox shafts [19 and 20, or 19 and 26] coincide with the ratio of the demanded gear, the gear shift-gate brake or gear shift lever brake [45/581 is released, and the gear can be engaged.

Prolonged depression of the clutch pedal prior to gear engagement with thevehicle at a standstill, and/or a high prevailing turning force of the input shaft [81 or meshing input shaft [81 and lay shaft [231, and/or an over-braking of the input shaft or meshing input shaft and lay shaft, can lead to the input shaft or 35 meshing shafts coming to a stop. If the dog clutch elements come 16 to rest in an unfavourable position, this condition makes it difficult or even impossible to shift into a gear. To overcome the problem, the clutch discs [10] and [131 of the gear synchronizing unit are equipped with radial cut-outs [741 and their respective solenoids [751 each have several radially offset coils. When the electronic module senses that the input shaft [81 or meshing input shaft [81 and lay shaft [231 have come to a stop prior to gear shifting, the module sequentially emits current to each of the radially offset coils in the solenoids [751. The solid parts of the clutch discs [101 and [131 are attracted by the energized coil in the solenoids [751 and the clutch discs [10/131 begin to rotate, thereby setting the auxiliary gear [11 or auxiliary shaft [271 in motion, which in turn makes it possible to engage a gear. The sense of rotation can be reversed is by changing the sequence in which the solenoid coils are energized.

The second mode of gear change is the reduction of the overall transmission ratio, commonly referred to as changing up (a gear) To enable synchronized engagement of a gear, the input shaft [8) or meshing input shaft [81 and lay shaft [231 need to be slowed down. At the same time, the progress of the gear shift lever needs to be controlled to prevent harsh (unsynchronized) gear engagement. The electronic module therefore energizes the third solenoid [151, which in turn activates the brake pad or brake band [16), and it activates the gear shift gate brake or gear shift lever brake [45/581. The brake pad or band [161 slows down the input shaft [81 through the auxiliary gears [l and 71, or it slows down the lay shaft [231 through the outer friction ring [251 on the splined clutch disc [131. If the speed of the input shaft [81 or the meshing input shaft [81 and lay shaft [231 drops too low, the electronic module energizes the solenoid [91, which activates the clutch disc [101. The clutch disc [101 connects the output shaft [61 or lay shaft [231 to the auxiliary gear [1 or 211. The auxiliary gear [11 then accelerates the input shaft [81 17 through the second auxiliary gear [71, or the second auxiliary gear [221 then accelerates the lay shaft [23] through the auxiliary gear [211. When the signals from the speed sensors on the gearbox shafts [19 and 20, or 19 and 261 coincide with the ratio of the demanded gear, the gear shift gate brake or gear shift lever brake [45/581 is released, and the gear can be engaged.

The third mode of gear change is the increase of the overall transmission ratio, commonly referred to as changing down (a gear). To enable synchronized engagement of a gear, the input shaft [81 or meshing input shaft [81 and lay shaft [231 need to be accelerated. At the same time, the progress of the gear shift lever needs to be controlled to prevent harsh (unsynchronized) is gear engagement. The electronic module therefore energizes the solenoid [91, which activates the clutch disc [101, and it activates the gear shift gate brake or gear shift lever brake [45/581. The clutch disc [101 connects the output shaft [61 or lay shaft [231 to the auxiliary gear [1 or 211. The auxiliary gear [11 then accelerates the input shaft [81 through the second auxiliary gear [71, or the second auxiliary gear [221 then accelerates the lay shaft [231 through the auxiliary gear [211.

If the speed of the input shaft [81 or the meshing input shaft [81 and lay shaft [231 rises too high, the electronic module energizes the third solenoid [151, which in turn activates the brake pad or brake band [161. The brake pad or band [161 slows down the input shaft [81 through the auxiliary gears [1 and 71, or it slows down the lay shaft [231 through the outer friction ring [251 on the splined clutch disc [131. When the signals from the speed sensors on the gearbox shafts [19 and 20, or 19 and 261 coincide with the ratio of the demanded gear, the gear shift gate brake or gear shift lever brake [45/58] is released, and the gear can be engaged.

The fourth mode of gear change is the reversal of the direction 18 of rotation. Shifting into reverse after driving in a forward direction should - strictly speaking - only be attempted when the vehicle has come to a standstill. However, dense urban traffic and other operating conditions and modes may require a shift into reverse while the vehicle is still in motion. To enable synchronized engagement of a reverse gear, the sense of rotation of the input shaft [81 or meshing input shaft [81 and lay shaft [23] needs to be reversed. At the same time, the progress of the gear shift lever needs to be controlled to prevent harsh (unsynchronized) gear engagement. The electronic module therefore energizes the second solenoid [121, and it activates the gear shift gate brake or gear shift lever brake [45/58]. When the second solenoid [121 is energized, it draws the sun wheel [31 against the friction lining of a second clutch disc [131. The sun wheel [31 then accelerates the auxiliary gear [11 through the planet gears [41 and the integral annulus [21 against the direction of rotation of the forward gears, or the sun wheel [31 then connects the auxiliary gear [211 through the planet gears [41 and the integral annulus [21 to the lay shaft [231 to accelerate the latter in the reverse direction of rotation.

Conversely, when shifting into a forward gear after reversing with the vehicle still in motion, the sense of rotation is altered by activating the solenoid [91 as described above.

If the reversed speed of the input shaft [81 or the meshing input shaft [81 and lay shaft [23] rises too high, the electronic module energizes the third solenoid [151, which in turn activates the brake pad or brake band [161. The brake pad or band [161 slows down the input shaft [81 through the auxiliary gears [1 and 71, or it slows down the lay shaft [23] through the outer friction ring [251 on the splined clutch disc [131. When the signals from the speed sensors on the gearbox shafts [19 and 20, or 19 and 261 coincide with the ratio of the demanded gear, the gear shift gate brake or gear shift lever brake [45/581 is released, and the gear can be engaged.

19

Claims

1 A single gear synchronizing unit for the synchronization of all forward and reverse gears of a manual gearbox, manual range speed gearbox and/or manual power transfer gearbox.

2 A gear synchronizing unit as claimed in Claim 1 which comprises a solenoid-operated brake, two solenoid-operated clutches, a planetary gear and a set of auxiliary gear wheels.

3 A gear synchronizing unit as claimed in Claim 1 and Claim 2 wherein a solenoid-operated clutch connects the output shaft to the input shaft in order to increase the speed of the input shaft.

4 A gear synchronizing unit as claimed in Claim 1 and Claim 2 wherein a solenoid-operated clutch connects the output shaft to the lay shaft in order to increase the speed of the lay shaft.

A gear synchronizing unit as claimed in Claims 1 to 3 wherein a solenoidoperated brake reduces the speed of the input shaft.

6 A gear synchronizing unit as claimed in Claims 1, 2 and 4 wherein a solenoid-operated brake reduces the speed of the lay shaft.

7 A gear synchronizing unit as claimed in Claims 1 to 3 and Claim 5 wherein a solenoid-operated clutch connects the output shaft through a planetary gear to the input shaft in order to reverse the sense of rotation of the input shaft.

8 A gear synchronizing unit as claimed in Claims 1, 2, 4 and 6 wherein a solenoid-operated clutch connects the output shaft through a planetary gear to the lay shaft in order to reverse the sense of rotation of the lay shaft.

9 A gear synchronizing unit as claimed in Claims 1 to 8 wherein the gear synchronizing unit's brake and two clutches are hydraulically assisted and the hydraulic circuits are controlled by solenoids.

A gear synchronizing unit as claimed in Claims 1 to 9 wherein the installation of the unit occurs directly on the output shaft or input shaft or lay shaft.

11 A gear synchronizing unit as claimed in Claims 1 to 9 wherein the installation of the unit occurs on an auxiliary shaft adjacent to the output shaft and input shaft or lay shaft.

12 A gear synchronizing unit as claimed in Claims 1 to 9 and Claim 11 wherein the installation of the unit occurs on an auxiliary shaft adjacent to the output shaft or input shaft or lay shaft and one or more idler gear wheels are part of the auxiliary gear train.

13 A gear synchronizing unit as claimed in Claims 1 to 12 wherein manipulation of the output shaft and input shaft or lay shaft occurs through auxiliary idler gear wheels.

14 A gear synchronizing unit as claimed in Claims 1 to 12 wherein manipulation of the output shaft and input shaft or lay shaft occurs by auxiliary sprockets and chains.

is A gear synchronizing unit as claimed in Claims 1 to 14 wherein a gear shift lever position sensor provides a unique, progressively changing resistance value for every possible shift lever position to monitor driver's intentions.

21 16 A gear synchronizing unit as claimed in Claims 1 to 15 wherein a solenoid-operated gear shift gate control mechanism controls the effort required to move the gear shift lever.

17 A gear synchronizing unit as claimed in Claims 1 to 16 wherein the solenoids for the forward and reverse gear synchronization contain two or more electrical coils each and act on suitably shaped clutch discs in order to make the gear synchronizing unit rotate to enable gear engagement with a stationary gearbox.

18 A gear synchronizing unit as claimed in Claims 1 to 17 wherein the electronic control system for the powertrain control of the manual gearbox, manual range speed gearbox or manual power transfer gearbox comprises an input shaft speed sensor, an output shaft speed sensor, a lubricant temperature sensor, a gear shift lever position sensor or gear shift position sensor, a solenoid-operated gear shift gate control mechanism and a solenoid-operated gear synchronizing unit.

19 A gear synchronizing unit as claimed in Claims 1 to 18 wherein the electronic module for the powertrain control of the manual gearbox, manual range speed gearbox or manual power transfer gearbox compares the signals from the input shaft speed sensor and the engine speed sensor to monitor the performance of the clutch and to raise a diagnostic trouble code if slip is detected.

A gear synchronizing unit as claimed in Claims 1 to 19 wherein springloaded rollers attached to a dog clutch run against a wavy track in the corresponding freewheeling gear in order to assist synchronization.

21 A gear synchronizing substantially as described herein with reference to Figures 1-12 of the accompanying drawings.