The invention pertains to a gearbox arrangement for the power train of a motor vehicle, possibly to a dual-clutch gearbox arrangement or to a power-shift gearbox arrangement, with at least one group of gear-shifting elements, each of which can be actuated to engage and to disengage at least one individual gear of the gearbox arrangement by moving, relative to a gearbox arrangement housing, between at least one neutral position, in which no gear assigned to the gear-shifting element is engaged, and at least one gear-engaged position, in which a gear assigned to the gear-shifting element and to the gear-engaged position is engaged. In this context, we are thinking primarily but not exclusively about so-called dual-clutch gearboxes or power-shift gearboxes, which have two gear trains which can be shifted independently of each other, each gear train having its own input shaft, to which a clutch arrangement (such as a wet-running clutch of the plate type or a dry-running clutch of the friction disk type) of a dual clutch is assigned so as to allow shifting between a gear of the one gear train to a gear of the other gear train without any interruption in the tractive force.
A dual-clutch gearbox can in principle be considered a parallel circuit of two fully functional gearboxes, each of which forms one of the two gear trains of the dual-clutch gearbox. The engine torque is distributed by the two clutches (two clutch arrangements) between the gear trains, where the one gear train takes care of shifting the even gears, while the other gear train takes care of shifting the odd gears. So that shifting from one gear to another can be accomplished without any interruption in the tractive force, one gear must be engaged in each gear train while the clutch torque is passed from the one gear train to the other.
The invention also pertains, however, to simple gear-shift mechanisms in which shifting gears always means an interruption in the tractive force.
To provide a corresponding vehicle with sports car-like driving behavior and to make it possible for the driver to respond rapidly to hazardous driving situations, it is desirable to realize, at least optionally, short shifting times for switching the gearbox arrangement between different gears. To prevent two gears assigned to the same gearbox input shaft from being engaged simultaneously by mistake, which could destroy the gearbox arrangement, the shifting forces required to shift gears must, under the conventional approach, be applied to the gear-shifting elements in a coordinated manner so that two of these gears cannot be engaged simultaneously. This means that, to ensure that no shifting errors can occur, the gear-shift time cannot be reduced below a certain minimum value. Nor is it excluded that an occurring defect, such as a defect in the actuator arrangement or in the control unit which drives the actuator, could cause the error of simultaneous engagement of two gears assigned to the same gearbox input shaft, leading to the corresponding negative effects on the gearbox and also to an endangerment regarding the driving safety of the vehicle.
In the case of a dual-clutch gearbox, especially upshifting and downshifting by more than one gear are time-critical where the starting gear and the target gear are both assigned to the same gear train and the torque must therefore be re-routed temporarily via the other gear train. If it is important to shift without any interruption in the tractive force during these multi-gear shifts, there must be at least two phases, during each of which two gears, one in each gear train, are engaged simultaneously. Between the two phases, it is necessary to disengage one gear and to engage another one as quickly as possible in the same gear train.
An object of the present invention is to provide gearbox arrangement in which the danger of incorrect shifting such that two or more gears are simultaneously engaged, which should not or must not be engaged simultaneously, is at least reduced. Another object of the present invention is to provide a gearbox arrangement which allows very short gear-shift times.
According to an embodiment of the invention, at least one locking device is provided with the gearbox arrangement, which is assigned jointly to all the gear-shifting elements of the group or of one of the groups, which is in a releasing state when all of the gear-shifting elements are in their neutral positions, and which can be moved from the releasing state to the locking state by the movement of one of the gear-shifting elements into the gear-engaged position or into one such position, wherein the locking device, when in the locking position, prevents the other gear-shifting element or all the other gear-shifting elements from moving out of the neutral position into the gear-engaged position or into one such position.
The locking device opposes the incorrect movement of the other or of all the other gear-shifting elements from the neutral position into the gear-engaged position or into one such position when one of the gear-shifting elements is located in the gear-engaged position. Thus the danger of incorrect shifting, as discussed above, is at least greatly reduced if not eliminated entirely. For this reason, short shifting times are possible indirectly, because the specific coordination of the shifting forces to be applied to shift gears is no longer of any particular importance.
It is advantageous for the locking device, when it is in the releasing state, to allow the assigned gear-shifting elements to move out of the neutral position and into the gear-engaged position or into one such position. It is proposed in particular that the locking device, when in the releasing state, allows the assigned gear-shifting elements to move out of the neutral position into the gear-engaged position or into one such position in such a way that only one of the gear-shifting elements can move into the gear-engaged position or into one such position.
An especially preferred embodiment is characterized in that, when the locking device is in the locking state, the other or all of the other gear-shifting elements are held, preferably locked, to prevent them from moving out of the neutral position into the gear-engaged position or into one such position, when subjected to a given maximum actuating force in this context, we are thinking in particular of a mechanical, positive type of interlock.
It is highly advisable for the locking device, when it is in the releasing state, to prevent the assigned gear-shifting elements from moving out of the neutral position into the gear-engaged position or into one such position on the basis of an actuating force which is less than a certain minimum actuating force. In this context, it is proposed by way of elaboration that, when the locking device is in the releasing state, all of the assigned gear-shifting elements are held and preferably locked to prevent them from moving out of the neutral position into the gear-engaged position or into one such position when subjected to an actuating force less than a certain minimum actuating force. In the releasing state of the locking device, it is advantageous for the individual assigned gear-shifting element to be released by the application of the minimum actuating force or of an actuating force greater than the minimum actuating force (for example, an actuating force equal to or approximately equal to the maximum actuating force).
An especially preferred embodiment is characterized in that, as a result of the movement of one of the gear-shifting elements from the neutral position into the gear-engaged position or into one such position, a retaining force can be activated or increased which acts on the other or on all the other gear-shifting elements, thus holding it/them in the neutral position. A locking device design of this type is especially resistant to errors, and a corresponding locking device can be realized mechanically in a very simple manner.
We are thinking here in particular that, as a result of the movement of one of the gear-shifting elements from the neutral position into the gear-engaged position or into one such position, a locking engagement which locks the other or all the other gear-shifting elements in the neutral position can be activated or increased.
According to an especially effective embodiment, the locking device comprises a locking element arrangement, which is preferably elastically pretensioned against the gear-shifting elements and engages positively with guide surfaces on the individual gear-shifting elements. The gear-shifting element guide surface can be advantageously designed so that a movement of one of the gear-shifting elements from the neutral position into the gear-engaged position or into one such position causes at least one element of the locking element arrangement to move in such a way that the locking element arrangement is tensioned more strongly against the other or all the other gear-shifting elements. A locking device of this type of particularly simple mechanical design has a spring-loaded plunger arrangement or ball arrangement, which is tensioned between two shaft elements and which engages positively in a recess in the guide surface of the gear-shifting element in question when this element is in the neutral position.
The locking device can have an even simpler mechanical design when formed as one rigid, inelastic locking element, not pretensioned in any way, or based on several such elements. It is proposed in this respect but also in general that the locking device have at least one locking element which is movably supported and dimensioned in such a way that, when the gear-shifting elements are in the neutral position, it is or can be brought into retaining engagement with at least one of the gear-shifting elements, and that any one of the gear-shifting elements can be moved out of the neutral position into the gear-engaged position or into one such position, where, when any one of the gear-shifting elements moves out of the neutral position into the gear-engaged position or into one such position, the gear-shifting element which moves out of the neutral position brings the locking element into retaining engagement with the other gear-shifting element or with all the other gear-shifting elements. The locking element can be, for example, a rigid plunger or pin with no moving parts, or a rigid disk with no moving parts.
It is proposed by way of elaboration that the retaining engagement is a positive engagement between an engaging section, such as an engaging end, of the locking element and an engaging section, such as a recess, in a surface of the associated gear-shifting element.
We are thinking here, for example, that, when the gear-shifting elements are in the neutral position, the locking element (e.g., the previously mentioned pin or plunger) can move in exactly one direction, especially in linear fashion, between a retaining engagement with a first gear-shifting element and a retaining engagement with a second gear-shifting element. In the case of a pin or plunger, the linear movement of the pin or plunger would be in the direction of its longitudinal axis.
As an alternative, it is proposed that, when the gear-shifting elements are in the neutral position, the locking element (e.g., the previously mentioned disk) can move, especially in linear fashion, in several directions between retaining engagements with more than two gear-shifting elements. In the case of a disk, the linear directions of movement will be in the plane of the disk.
As another possibility, it is proposed as being especially preferred that, when the gear-shifting elements are in the neutral position, the locking element can pivot between a retaining engagement with a first and a retaining engagement with a second gear-shifting element. A pivot bearing can be provided at especially low cost and provides a high level of functional reliability.
Insofar as a “retaining engagement” has been mentioned above, what is meant primarily or meant additionally is that, when the gear-shifting elements are in the neutral position, the retaining engagement of the locking element, at least one of which is provided, with an associated gear-shifting element is a nonlocking type of engagement, which can be overcome by the movement of the gear-shifting element in the direction toward the gear-engaged position or into one such position, and that, in the case of a gear-shifting element which has been moved out of the neutral position into the gear-engaged position or into one such position, the retaining engagement of the at least one locking element with the other gear-shifting element or all the other gear-shifting elements is a locking type of engagement which cannot be overcome, at least not by the given actuating forces, and which is locked by the gear-shifting element which has moved out of its neutral position.
Especially short gear-shift times are possible when a gear-engaging actuating force can be applied to one of the gear-shifting elements of the group in the neutral position while the other or one of the other gear-shifting elements of the group is in the gear-engaged position or in one such position, the one gear-shifting element being held in the neutral position by the locking device in opposition to the applied gear-engaging actuating force, wherein, through the movement of the other gear-shifting element from the gear-engaged position into the neutral position under the action of an applied gear-disengaging force, the locking device can be switched to the releasing state in order to allow the one gear-shifting element to move under the action of the applied gear-engaging actuating force out of the neutral position and into the gear-engaged position or into one such position.
In correspondence with conventional designs, the gear-shifting elements can be designed as gear-shift rods. The group or the individual group in question can have two gear-shifting elements (possibly gear-shift rods). The group or each group, however, can also have more than two gear-shifting elements (possibly gear-shift rods). For example, it can have three gear-shifting elements (possibly gear-shift rods).
Especially in the case of a dual-clutch gearbox arrangement or power-shift gearbox arrangement, at least two groups of gear-shifting elements (possibly gear-shift rods), which can be actuated independently of each other, are provided.
We are thinking here in particular of an automatic shifting of the gearbox arrangement. For this purpose, an actuator arrangement assigned to the gear-shifting elements (possibly gear-shift rods) can be provided, by means of which the gear-shifting elements (possibly gear-shift rods) can be actuated in automated fashion.
It is preferable for each of the gear-shifting elements (possibly gear-shift rods) of the group or of at least one group to have at least one actuator assigned to, so that an actuating force which acts in the direction of movement of the gear-shifting elements (possibly gear-shift rods) can be applied simultaneously to each of several gear-shifting elements (possibly gear-shift rods) of the group.
The invention also provides a motor vehicle power train comprising a drive unit (possibly an internal combustion engine), a gearbox arrangement (possibly a dual-clutch gearbox arrangement or a power-shift gearbox arrangement with two groups of gear-shifting elements) according to the invention, and a clutch device (possibly a dual-clutch device with two clutch arrangements, each of which is assigned to its own gearbox input shaft and thus to its own group of gear-shifting elements) for the transmission of torque between the drive unit and the gearbox arrangement.
The invention also provides a process for shifting an inventive gearbox arrangement or the gearbox arrangement of an inventive motor vehicle power train. The inventive process is characterized by a sequence of gear-shifting steps in which a gear-engaging actuating force is applied to one of the gear-shifting elements of the group of gear-shifting elements or of one such group of the elements in the neutral position, while the other gear-shifting element or one of the other gear-shifting elements of the group is in the gear-engaged position or in one such position, wherein the one gear-shifting element is held in the neutral position by the locking device in opposition to the applied gear-engaging actuating force as long as the other gear-shifting element is in the engaged position; and in which a gear-disengaging actuating force is applied to the other gear-shifting element to move the other gear-shifting element out of the gear-engaged position into the neutral position, wherein the locking device is switched to the releasing state by the movement of the other gear-shifting element out of the gear-engaged position into the neutral position, as a result of which the one gear-shifting element is then moved out of the neutral position into the gear-engaged position or into one such position under the action of the applied gear-engaging actuating force. Very short gear-shift times can thus be realized.
By way of elaboration, it is proposed with respect to the shifting of a dual-clutch gearbox arrangement or of a power-shift gearbox arrangement that the shifting sequence comprise a multi-gear shifting of the gearbox arrangement from a starting gear to a target gear several gears away from the starting gear, wherein a gear-shifting element assigned to the starting gear and a gear-shifting element assigned to the target gear both belong to the same group of gear-shifting elements, and wherein the gear-engaging actuating force is applied to the one gear-shifting element and the gear-disengaging force is applied to the other gear-shifting element during the process of shifting from the starting gear to the target gear. The sequence of shifting steps can comprise, for example, a multi-gear downshift, especially a multi-stage downshift. We are thinking here in particular that the sequence of shifting operations will comprise at least one crossover shifting phase and preferably at least two crossover shifting phases between the starting gear or one of the starting gears and a target gear or one of the target gears.