CN106464560B

CN106464560B - Bus system

Info

Publication number: CN106464560B
Application number: CN201580029264.2A
Authority: CN
Inventors: 维尔纳·施米特
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2014-06-05
Filing date: 2015-06-02
Publication date: 2020-03-17
Anticipated expiration: 2035-06-02
Also published as: CN106464560A; WO2015185057A1; DE102014210698A1; DE112015002656A5

Abstract

The invention relates to a termination of a bus system, preferably for use in a dual clutch transmission, wherein the bus system, which is formed from at least two individual wires, connects at least three control devices to one another for communication purposes, wherein a bus termination resistor having a predetermined resistance value is assigned to each control device in order to adapt the control device resistance to the bus system resistance, wherein the bus termination resistors are connected in parallel to one another. In the case of a termination of a bus system which enables the greatest possible communication with subscribers on the bus system even if the cable breaks, the total resistance of the parallel bus termination resistances in the disturbed state of the bus system is approximately equal to the total resistance of the bus termination resistances in the undisturbed state of the bus system.

Description

Bus system

Technical Field

The invention relates to a termination of a bus system, preferably for use in a dual clutch transmission, wherein the bus system, which is formed from at least two individual wires, connects at least three control devices to one another for communication purposes, wherein a bus termination resistor having a predetermined resistance value is assigned to each control device in order to match the control device resistance to the bus system resistance, wherein the bus termination resistors are connected in parallel to one another.

Background

In motor vehicles, actuators are used, for example, for actuating automatic transmissions or for actuating automatic friction clutches. In this way, for actuating the automatic friction clutch, a hydrostatically operated actuator (HCA hydrostatic clutch actuator) is used, as is disclosed, for example, in DE 102010047801 a 1. An actuator is understood here to mean a system which converts an electronic signal, for example by a control device, into a mechanical movement.

DE 102012218252 a1 discloses a method for starting a vehicle transmission and/or a vehicle clutch, wherein such a hydrostatically operated clutch actuator (HCA) is used. The clutch actuator (HCA) is connected to a higher-order control device, preferably a transmission control device, via a local CAN bus, which is connected to a central CAN bus in the motor vehicle. The transmission control device communicates via a local CAN bus with two local control devices, which are contained in the electrostatic actuator, each of which controls a clutch of the dual clutch transmission.

The CAN bus for communication between the different control devices comprises a twisted pair (two insulated individual wires twisted about one another, with a predetermined characteristic impedance of 120 ohms at both line ends) as a bus medium, resulting in a parallel circuit with a total resistance of 60 ohms. Since the line used has a much lower impedance than the double 120 ohm characteristic impedance recommended according to ISO regulation 11898-2, an additional bus termination resistor has to be installed. The control device resistance is matched to the bus system resistance by means of this bus termination resistance. The bus termination resistance of the transmission control unit is designed to be high-ohmic and can be, for example, 2.6 k-ohms, while the 120-ohm termination resistance of the local control unit is low-ohmic. If the impedances are mismatched, the transmitted signal is not completely received by the control device and is then reflected back into the bus system, thereby changing the signal level at the bus system at that moment, which is an undesirable effect and leads to communication disturbances.

If now one of the individual cores of the CAN bus is interrupted, the entire bus transmission is disturbed, since the total resistance in the remaining bus system increases, thereby causing undesirable reflections which change the level of the CAN signal. This results in: such signals can no longer be interpreted.

Disclosure of Invention

The invention is therefore based on the object of: a termination of a bus system is provided, in which an almost error-free communication can be carried out between the remaining control devices even if the bus system is disturbed.

According to the invention, said object is achieved by: in the disturbed state of the bus system, the total resistance of the parallel bus termination resistances is approximately equal to the total resistance of the bus termination resistances in the undisturbed state of the bus system. Furthermore, termination is to be understood as: the physical ends of the data lines, in this case the two individual wires of the bus system, are each provided with a bus termination resistor in order to prevent reflections. The bus termination resistance forms the input resistance of the control device. The proposed solution has the advantages of: although the bus system between the remaining subscribers is disturbed, sufficient communication over the bus system is ensured, even if the availability of subscribers is reduced.

Advantageously, a disturbed state of the bus system is present in the event of an interruption in one of the individual strands. In the event of such an interruption, only the control devices connected to the bus system cannot participate in the communication, while all other control devices can continue to communicate with one another.

In one embodiment, the first control unit is designed as a superordinate control unit which controls the local second control unit and the local third control unit via the local bus system. In particular in such a small CAN bus system with only a small number of subscribers, the communication between the control subscribers CAN be continued in a simple manner by means of an undisturbed single-strand core. The local bus system therefore also remains operational without interfering with the overall data transmission of the motor vehicle.

In one variant, the upper-level first control device is provided with a low-ohmic bus termination resistor, while the second local control device and the third local control device are each provided with a high-ohmic bus termination resistor. According to the physical rule for the total resistance in the parallel circuit, the high-ohmic bus termination resistance of the local control device only does not significantly influence the total resistance. In the proposed manner, therefore, data transmission between control devices between which no interference of individual strands of the core wire is present can be maintained.

In one embodiment, the line length of the bus system is ≦ 1 m. By using very short data lines in the bus system, reflections applied by other bus users are reliably suppressed, so that communication between the bus users is reliably ensured.

In one refinement, the first control device is designed to control a motor vehicle transmission, and the second control device and the third control device are designed to each control a motor vehicle clutch. The described termination of the bus system can therefore be used in particular for structurally complex units having a plurality of control devices which are spatially installed in the mechanical unit.

In one embodiment, the local second control unit and the local third control unit are part of a hydrostatic clutch actuator, wherein each local control unit controls a clutch of the dual clutch transmission. With this configuration, the clutches of the dual clutch transmission remain in operation even when the bus system is disturbed.

Drawings

Many embodiments of the invention are possible. One embodiment of which is explained in detail with the aid of the figures shown in the drawings.

It shows that:

figure 1 shows a schematic diagram of a dual clutch transmission system in a motor vehicle,

figure 2 shows a schematic diagram of the connections of the control devices of the dual clutch transmission system according to figure 1,

fig. 3 shows a schematic diagram of a disturbed bus system of the dual clutch transmission system according to fig. 1.

Like features are provided with like reference numerals.

Detailed Description

The schematic representation of a transmission system of a motor vehicle, which is shown in fig. 1 and has a dual clutch transmission, shows a transmission control device 1, which is arranged upstream of the clutch system. The clutch system is designed as a dual clutch system and has two

clutch actuators

2, 3, each of the

clutch actuators

2, 3 having an automatic clutch 4, 5, on which a

clutch control device

6, 7 for controlling the clutches 4, 5 is locally positioned. A bus termination resistor 1.1, 6.1, 7.1 is provided in each

control unit

1, 6, 7. The transmission 8 together with the two

clutch actuators

2, 3 is integrated as a component 9 into the motor vehicle. Here, the transmission control device 1 is connected to a transmission actuator 11 via a connecting cable 10. The transmission actuator 11 is likewise fixedly mounted in the transmission 8. The transmission control device 1 is also connected to a common vehicle CAN bus 12, to which other control devices of the motor vehicle, such as an engine control unit 13, are also connected.

Fig. 2 shows the connection of the transmission control device 1 to the

clutch control devices

6, 7. The local bus system 14, which connects the transmission control device 1 to the

clutch control devices

6, 7, is formed from two individual wires CAN low and CAN high, which are insulated from one another. The bus termination resistance 1.1 of the transmission control device 1 comprises a low-ohmic resistance value of, for example, 60 Ω. The bus termination resistances 6.1, 7.1 of the

clutch control devices

6, 7 are designed to be high-ohmic and each comprise a resistance value of approximately 2.6k Ω. Due to a line interruption, for example, in the individual core wires CANhigh in the connection to the second clutch control device 7, the total resistance of the parallel circuit is now maintained at 60 Ω, since the bus termination resistances 6.1, 7.1 of the

clutch control devices

6, 7 only slightly influence the total resistance due to their high ohmic resistance. Since the total resistance remains approximately constant, at least the communication between the transmission control device 1 and the clutch control device 6 can also be undisturbed.

The value of 2.6k omega of the bus termination resistances 6.1, 7.1 applied in the figures is merely exemplary and represents a high ohmic value. The specification of a resistance value of 60 Ω for the bus termination resistance 1.1 of the control device 1 is also a general specification.

List of reference numerals

1 Transmission control apparatus

1.1 bus termination resistance

2 Clutch actuator

3 Clutch actuator

4 Clutch

5 Clutch

6 Clutch control apparatus

6.1 bus termination resistor

7 Clutch control device

7.1 bus termination resistance

8 speed variator

9 component

10 connecting line

11 speed variator actuator

12 vehicle CAN bus

13 Engine control Unit

14 local CAN bus

Claims

1. A bus system comprising a termination structure, wherein the bus system (14) consisting of at least two individual conductors (CANlow; CAN high) connects at least three control devices (1, 6, 7) to one another for communication purposes, wherein each control device (1, 6, 7) is assigned a bus termination resistance (1.1, 6.1, 7.1) having a predetermined resistance value in order to match the control device resistance to the bus system resistance, wherein the bus termination resistances are connected in parallel to one another, characterized in that, in the disturbed state of the bus system (14), the total resistance of the parallel bus termination resistances (1.1, 6.1, 7.1) is approximately equal to the total resistance of the bus termination resistances (1.1, 6.1, 7.1) in the undisturbed state of the bus system (14).

2. Bus system according to claim 1, characterized in that a disturbed state of the bus system (14) exists in case of an interruption of one of the individual core wires (CANlow; CAN high).

3. Bus system according to claim 1, characterized in that the first control unit (1) is designed as a superordinate control unit which controls the local second and third control units (6, 7) via the local bus system (14).

4. Bus system according to claim 3, characterized in that the first superordinate control device (1) is assigned a low-ohmic bus termination resistor (1.1), while the second and third local control devices (6, 7) are each assigned a high-ohmic bus termination resistor (6.1, 7.1).

5. Bus system according to claim 1, characterised in that the line length of the bus system (14) is ≦ 1 m.

6. Bus system according to claim 3 or 4, characterised in that the first control device (1) is designed for controlling a motor vehicle transmission (8) and the second and third control devices (6; 7) are designed for controlling in each case one motor vehicle clutch (4, 5).

7. The bus system according to claim 6, wherein the local second control unit and the local third control unit (6; 7) are part of a hydrostatic clutch actuator, wherein each local control unit (6; 7) controls one clutch (4, 5) of the dual clutch transmission.

8. The bus system as set forth in claim 1, wherein said termination structure is for a bus system used in a dual clutch transmission.