Patent Application
20190242445
The present invention relates to a shift gearbox according to the preamble of claim 1.
From DE 10 2006 038 446 A1 a shift gearbox with an electromotively driven piston-cylinder unit is described in which one or two piston-cylinder units operate four gear selectors and two clutches. The piston-cylinder unit generates the pressure required for adjusting the gear selectors and clutches, whereby a pressure sensor measures the pressure generated. DE 10 2006 038 446 A1 describes two possible embodiments for this purpose. In the first embodiment, clutches and gear selectors are adjusted over for actuation of so-called multiplex valves by means of the piston-cylinder unit. In this case, the pressure build-up and the pressure reduction can take place via the piston-cylinder unit. However, it is also possible that for some or all consumers additional exhaust valves are provided, via which the pressure in the individual consumers can be regulatedly lowered.
From DE 10 2006 014 280, a shift gearbox is already known in which the clutch actuator and gear selector are adjusted by means of second piston-cylinder units, wherein the pressure build-up and reduction takes place in the clutch actuators via proportional valves.
The object of the invention is to further improve the shift gearbox known from DE 10 2006 038 446 A1.
This object is achieved with a shift gearbox according to the invention with the features of claim 1. Advantageous embodiments of this shift gearbox result from the features of the dependent claims.
The invention is advantageously characterised in that a valve is arranged between each working chamber of a clutch actuator and a main hydraulic line, and both the pressure build-up and the pressure reduction in the clutch actuators takes place by adjusting the piston of a piston-cylinder unit, whereby the valve for the pressure change in the clutch actuator is opened and closed to maintain pressure in the clutch actuator, as well as to deactivate the clutch actuator while other shift gearbox units of the respective hydraulic main line are operated. As a result, a high-precision control of a multiple clutch system is possible, wherein a plurality of gear selectors and at least two clutches can be switched. The valves employing the clutch actuator of the piston-cylinder units, which serve to adjust the clutch plate, may advantageously be pure 2/2-way switching valves, as no proportional control takes place over them. Rather, the pressure build-up and reduction takes place via the adjustment of the respective piston of the associated piston-cylinder unit. In this case, the volume of fluid required for switching the clutch actuator is advantageously displaced with the piston-cylinder unit via a volume control. In doing so, advantageously, a pressure volume characteristic can be used, in which the pressure change is stored at a corresponding path change of the piston of the piston-cylinder unit. In addition, a model can be used which simulates the corresponding relationships and thus required control variables and parameters can be determined, whereby a precise pressure gradient control is possible. In the shift gearbox according to the invention, expensive proportional valves can thus advantageously be dispensed with.
The shift gearbox according to the invention thus advantageously manages to meet the very high demands on a very precise pressure regulation (micro-slip control) of the clutches with an angle sensor on the drive of a piston-cylinder unit. During the simultaneous switching of two clutches—one clutch is opened while the other clutch is closed—as well as during gear shifting, it may happen that the load of the engine changes and thus the clutch must be readjusted (slip control), so that the driver does not perceive the gear change, allowing maximum ride comfort to be achieved.
This is not possible with a classic control via pressure transducers or pressure sensors, since pressure transducers do not have resolution like an angle sensor of an electric motor. If a pressure transducer is used to determine the pressure or the piston force on the clutch (force or clutch torque=area*pressure), the usual pressure transducers only achieve a resolution of approx. 0.5 bar. The use of an angle sensor, however, brings a higher resolution by a factor of 10. A pressure transducer with correspondingly high resolution, however, is much more expensive. The angle sensor may be e.g. a classic Hall sensor, which can be very cheap and is also easy to read.
The gear selectors of the shift gearbox according to the invention generally comprise respectively a first and a second working chamber separated by a piston, wherein the working chambers of the clutch actuator are in communication with the respectively associated hydraulic main line via hydraulic connecting lines. The first working chambers of the gear selectors are in each case in communication with the respectively associated hydraulic main line by means of hydraulic connecting lines, wherein the hydraulic connecting lines can each be shut off by means of a switching valve.
The two working chambers delimiting piston surfaces of the piston of the gear selector are formed in different sizes, wherein the larger piston surface delimits the first working chamber.
In a first embodiment, the second working chambers of the gear selectors are connected to the same hydraulic main line with which the hydraulic feed lines are also connected, in which the switching valve associated with the control valve is arranged. In a second possible embodiment, however, the second working chambers of the gear selector are connected with the other hydraulic main line by means of a respective hydraulic connecting line, the hydraulic supply line of the respective gear selector being not directly connected with the other hydraulic main line, in that the associated switching valve is arranged in the gear selector.
In the first embodiment described above, the first working chamber of at least one gear selector is in connection with a reservoir via a hydraulic line, wherein a switching valve, in particular a 2/2-way valve, is arranged for selectively opening and shutting off the hydraulic line in this. In this embodiment, which is shown and described in
ΔF=P22a*A22a−P21a*A21a,with P21a≈1 bar.
Advantageously, the two hydraulic main lines can be connected to one another via a hydraulic connecting line, wherein a switching valve for selectively opening or closing the hydraulic connecting line is arranged in the hydraulic connecting line. This advantageously results in many additional possibilities and redundancies. Thus, in the case of failure in one piston-cylinder unit, the other can take over its function via the connecting line. It is also possible that the hydraulic pressure stored in one clutch can be used to support the shifting of the other clutch.
The control unit, which controls the respective electromotive drive for adjusting at least one of the shift gearbox units, uses the rotation angle φ of the drive, the motor current i flowing through the drive, the piston location s and/or the distance Δs of the piston of the piston-cylinder unit as a manipulated variable for the control of the drive, so that the piston conveys a required hydraulic volume in or out of the respective one shift gearbox unit.
Advantageously, the shift gearbox units may comprise a location sensor or position sensor. Their signals can be advantageously used to control the drive and/or to calibrate the control and/or the simulation model.
If a pressure transducer is used, it will only be used for calibration or redundancy. Optionally, a very simple pressure transducer is sufficient for calibration purposes only, to detect a correlation of the current flowing through the electric motor to the pressure, in order that changes in the system, e.g. a change in efficiency of the trapezoidal spindle, can be taken into account. But this can also be done via a displacement sensor of the gear selector or clutches. The adjustment is critical if e.g. a trapezoidal spindle is used in the electric motor, which due to its properties has high efficiency fluctuations in its operation, e.g. if it is made of plastic. However, the use of the trapezoidal spindle leads to significant cost savings, the additional effort for one or more calibration sensors is conversely low.
Also, both hydraulic actuators can be adjusted in the form of the piston-cylinder units with only one pressure transducer. This can take place e.g. via the connecting line and the valve arranged therein, which connects the two hydraulic main lines together.
In addition, the system can advantageously be simplified in such a way as to dispense with displacement sensors in the clutch and gear selector. However, primarily for safety reasons (e.g., detection of leaks in the hydraulic system, checking the start and end locations before and after a gear shift), a very simple sensor, e.g. digital Hall switch to determine the discrete position of the gearshift (left, neutral, right), and clutches are used, whereby with the clutch only a discrete position is required. In the simplest case, only one calibration sensor is used for both piston-cylinder units. Clutches and gear selectors are then controlled exclusively via travel control of the motor with simultaneous use of the current of the electric motor for pressure calculation. This leads to limitations in accuracy. However, the convenience is sufficient, whereby the full functionality is ensured for simple vehicles.
Advantageously, the shift gearbox according to the invention can comprise more than two clutch actuators. Thus it is easily possible that three clutches and several gear selectors can be actuated with the two piston-cylinder units. In the case of three clutch actuators or clutches, two or one clutch and one gear selector can be simultaneously displaced or switched at the same time. Thus, the third clutch actuator can be selectively shut off from the two hydraulic main lines or connected to one of the two hydraulic main lines, for example via a supply line by means of a 3/3-way valve or at least two 2/2-way valves. However, it is also possible that the third clutch actuator is connected by means of a valve only to a hydraulic main line. In the latter case, however, the third clutch can no longer be controlled separately from the other two clutch actuators.
As already stated above, the energy stored hydraulically in another clutch can be used to switch over a clutch. In this case, in particular the stored energy from the one clutch occurs via the valve connecting the two hydraulic main lines together or via the one or two valves, by means of which the third clutch is connected to the two main hydraulic lines. The stored energy may be used to assist in the pressure build-up in another, e.g. the second clutch. Thus, the second piston-cylinder unit, which can also be referred to as a hydraulic actuator, can be discharged and can be designed for lower torques and power. This advantageously has significant effects on the costs, which are highly relevant in particular in a system with two piston-cylinder units or hydraulic actuators. As a result, the use of a trapezoidal spindle is possible, whereby further cost savings are possible.
It is also advantageously possible that at least one clutch is cooled by means of a cooling medium, wherein the cooling medium is conveyed by means of the drive of a piston-cylinder unit or a separate drive, which in particular drives a pump.
A particularly favourable shift gearbox is obtained when the power unit drives the piston via a trapezoidal spindle.
Furthermore, flow resistances may be arranged, in particular in the form of apertures in the hydraulic main lines, in particular in the sections connecting the clutch(es) with the gear selectors. For example,
As already stated, the shift gearbox according to the invention is advantageous in that either the pressure build-up and pressure reduction takes place in at least two clutches simultaneously, temporally overlapping or successively by means of back and forth movements of the piston of the piston-cylinder units (10a, 10b), or the pressure build-up or pressure reduction takes place in a clutch with one of the piston-cylinder units, and an adjustment of a gear selector takes place simultaneously, temporally overlapping or successively by means of the other piston-cylinder units, wherein in the case of the pressure change in a clutch, the respective associated valve is open.
Thus, it is particularly advantageous if either the pressure build-up and/or pressure reduction occurs in the first clutch via the first piston-cylinder unit and the simultaneous pressure build-up and/or pressure reduction occurs in the second or third clutch via the second piston-cylinder unit, or the pressure build-up and/or pressure reduction occurs in the second clutch via the second piston-cylinder unit and the simultaneous pressure build-up and/or pressure reduction occurs in the third clutch via the first piston-cylinder unit, whereby in all cases the valves of the shift gearbox are connected such that the pressure change in one clutch does not affect the pressure change in another clutch.
Because of the travel control of the pistons of the piston-cylinder units, which corresponds to a volume control, advantageously a cost-effective design is possible, in that the design allows the number of valves required to be reduced. Due to the travel or volume control, it can easily be effected that at least one shift gearbox unit may comprise more than two switching locations, without a complex pressure regulation, since, due to the incompressibility of the hydraulic medium over a predetermined conveyed volume, the respective shift gearbox unit can be adjusted specifically in one of the possible positions. The components of the shift gearbox units, in particular gear selectors and clutch actuators, moreover, can be adjusted accurately and more quickly by the travel and volume control with pistons, than with proportional valves, since an additional control variable can be used on the basis of prior knowledge of the displacement volume.
Various possible embodiments of the shift gearbox according to the invention will be explained in more detail with reference to the following drawings.
In the drawings:
The actuation unit comprises the sub-transmission 1, the sub-transmission 2 and the pressure supply unit 3. The pressure supply unit comprises the two piston-cylinder units or hydraulic actuators 10a and 10b. Preferably, the transmission is configured so that in a sub-transmission 1 the odd gears are arranged, and in the other sub-transmission the even gears and downshift are arranged.
Both sub-transmissions and both hydraulic actuators are constructed identically in principle, so that in the following only the sub-transmission 1 and hydraulic actuator 1 are described in more detail. For a better overview, its reference numerals are provided with the index a and c. The description also applies to the sub-transmission 2 and hydraulic actuator 2 with the corresponding change of the index reference numerals from a to b, and c to d. Also, the idea according to the invention can be extended to transmissions with different numbers of hydraulic actuator elements. More or fewer clutches C1, C2 or gear selectors 7a-d can be connected as shown here.
In the sub-transmission 1, the actuating piston 6a of the clutch actuator 4a actuates the clutch C1, not shown. The stroke is detected via the displacement sensor 5a. The clutch C1, not shown, is preferably designed so that when unactuated it is opened by the clutch spring.
The sub-transmission 1 comprises the gear selectors 7a and 7c. Again, only the function of the gear selector 7a is described. Due to the corresponding change of indices, the description also applies to the gear selector 7c, or the gear selector 7b and 7d of the sub-transmission 2.
The gear selector piston 8a actuates the respective gears of the dual-clutch transmission, not shown, via the transmission shift fork, not shown. The displacement sensor 9a detects the stroke of the gear selector piston 8a.
The gear selector 7a is designed as a double-acting piston 8a. The two gear selector chambers 21a and 22a have differently sized hydraulically effective surfaces. Both gear selector chambers are connected to the pressure line 18a constituting the first hydraulic main line, wherein the left gear selector chamber 21a can be separated from the pressure pipe 18a by the gear selector valve 20a. In addition, the left gear selector chamber 21a can be connected to the reservoir 25 by correspondingly switching the gear selector outlet valve 23a via the hydraulic line 24a.
The hydraulic actuator 1 comprises the drive motor 11a, a transmission 13a, and a hydraulic piston 14a having the hydraulic chamber 40a. The hydraulic chamber 40a can draw hydraulic fluid from the reservoir 25 via the check valve 15a and the hydraulic line 16a by the switching valves 19a, 20a, 20c and 26 being closed and the piston 14a retracting. On the other hand, if the piston 14a moves forward, the hydraulic fluid in the chamber 40a is displaced, whereby pressure is generated in the pressure line 18a. This pressure can be detected by the optional pressure transducer 17a.
The motor angle sensor detects the rotor position and can thus detect the piston stroke via the known gear ratio. Alternatively, the engine torque and thus indirectly the pressure in the hydraulic chamber 40a can be measured via a corresponding current sensor (not shown) in the electronics.
In dual-clutch transmissions, the clutches are often operated in so-called micro-slip. This is done especially with so-called wet clutches but also with dry clutches. As a result, it is necessary that the clutch actuation must be permanently readjusted. With the inventive use of two hydraulic actuators, it is possible that a hydraulic actuator permanently controls the pressure in the active clutch and the other hydraulic actuator simultaneously and independently manages the gear position of the inactive sub-transmission.
Since the clutch actuation and gear position thus take place independently of one another, it is possible to use, for example, a trapezoidal spindle as the transmission and still dispense with a pressure transducer. A trapezoidal spindle has the disadvantage compared to a ball screw of having a poorer efficiency, which can also vary over its life. Thus, the pressure estimate on the motor current becomes increasingly inaccurate. If the clutch control relies on an accurate pressure regulation, then a pressure transducer is required. This would be the case if the actuation of the active clutch has to be interrupted for a short time, e.g. to handle a gear position. However, since in the described embodiment, the clutch operation does not have to be interrupted, it is possible purely to control the clutch actuator position.
Through the connection valve 26, the two hydraulic lines 18a and 18b can be connected. Thus, it is possible to transfer the pressure from the opening clutch into the closing clutch during a quick clutch change. Thus, the hydraulic actuator of the closing clutch has to apply less power and thus can be made smaller, whereby costs can be saved.
In addition, it is possible that, e.g. in the case of failure of a hydraulic actuator, the still functioning hydraulic actuator controls the drive, the clutches and gear selector of both sub-transmission lines with appropriate performance restrictions and thus enables emergency operation. In particular, it is thus certainly possible to engage the reverse gear.
Another advantage of the connection valve is that for special cases both hydraulic actuators can operate a clutch together. This can be advantageous if the performance of a clutch actuator should not be sufficient to achieve the maximum clutch actuation force.
Nevertheless, the connection valve 26 is to be regarded as optional and is not absolutely necessary for the basic function of the transmission control.
In the described embodiment of the actuation unit of a multi-clutch transmission, all the drives of the hydraulic actuator elements are effected by the location and speed of the master cylinders 14a and 14b, or the pressure in the pressure lines 18a and 18b. The valves do not have to fulfil a pressure regulation task, but represent a pure hydraulic connection between the respective pressure chambers.
All valves shown can thus be represented as purely digitally switching 2/2-way valves. These can be designed as so-called seated ball valves. These valves are much cheaper than proportional valves and have a much lower leakage in the closed state. The electronics required for switching are also advantageously much simpler. Also, the drive logic of these valves is simpler since no thermal models, etc., are required. The seated ball valves are also smaller.
Seated ball valves in 2/2-way versions can be designed to be open or closed when currentless. In all figures, the preferred embodiment is realised. However, the respective other embodiment is also possible.
The additional clutch 41 can be connected via the additional valves 42a and 42b to the pressure lines 18a and 18b. Depending on the control logic and driving condition, this clutch can be actuated via the hydraulic actuator 1 or the hydraulic actuator 2. The clutch can be controlled via location or pressure. The clutch can be designed to be open or closed when not in operation. In addition, it is possible to operate a clutch with leakage, e.g. with hydraulic rotary feedthrough.
It is also possible to control one or more further gear selectors, not shown, by controlling them with the same switching logic.
The actuation of the clutch actuators 4a and 4b takes place as described in
Compared to
The following describes how the clutch actuator 4a is actively controlled simultaneously and the gear selector 7b is moved simultaneously from the illustrated central position into the right-hand end position:
First, all switching valves are closed up to 19a. The hydraulic actuator 10a directly drives the clutch actuator 4a. The pressure in the pressure line 18a is accordingly also present in the right gear selector chamber 22b of the gear selector 7b. Since the valve 20b is closed, the gear selector piston 8b does not move. Nevertheless, pressure builds up in the left gear selector chamber 21b. Since the left gear selector chamber 21b has a larger hydraulically active area than the right gear selector chamber 22b, the pressure in the left gear selector chamber is smaller in accordance with the area ratio of the two gear selector chambers.
This adjusting pressure in the left gear selector chamber 21b is now driven by the hydraulic actuator 10b. As a controlled variable, the pressure transducer 17b can be used for this purpose. Alternatively, the pressure can also be regulated with sufficient accuracy via the motor current. Now the gear selector inlet valve 20b is opened. Since a balance of forces acts on the gear selector piston 8b, this initially remains in the middle position. Now, the hydraulic actuator 10b starts to supply hydraulic fluid to the left-hand gear selector chamber 21b. At the same time, in the hydraulic actuator 10a, the master cylinder 14a is moved backward, so that the pressure in the gear selector 4a remains constant, but at the same time fluid is removed from the right gear selector chamber 22b. It is also possible during this process to modulate the pressure or location of the clutch actuator. An optional hydraulic damping element 27a can be used to reduce the influence of the pressure in the gear selector 4a by a dynamic gear shift operation.
The sequence of the switching operation of the gear selector 7b in the left end position is almost identical. Only the direction of movement of the two hydraulic actuators changes, so that the hydraulic actuator 10b withdraws fluid from the left hydraulic actuator chamber 21b and the hydraulic actuator 10a delivers fluid into the right hydraulic actuator chamber 22b.
The sequence for switching operations of the gear selector 7a-9d is analogous to the case described here by way of example. Only the corresponding gear selector inlet valve 20a-20d is opened.
It should be noted that the control of the gear selector piston 8a-8d is selected so that the pressure of the active clutch actuator 4a or 4b acts on the right gear selector chamber 22a-22d. Thus, the pressure which must be established in the respective left gear selector chamber 21a-21d, which is to be controlled, must be respectively lower than the pressure in the active gear selector 4a or 4b. Thus, the hydraulic actuators 10a-10b can be designed for the maximum required pressure for the clutch actuation and need not provide even higher pressures for the gear position. Thus, in comparison with another embodiment, e.g. as described in
By the described embodiment of the actuation unit, it is thus possible to reduce the number of switching valves required and still have the full degree of freedom in the simultaneous control of the clutch and gear position. The power requirements on the hydraulic actuator 10a and 10b thereby do not increase in relation to the embodiment in
As already described in
As already described in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 116 778.9 | Sep 2016 | DE | national |
| 10 2016 118 423.3 | Sep 2016 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/054641 | 2/28/2017 | WO | 00 |
