WO2007006595A1

WO2007006595A1 - Device for measuring the torque on a gear shaft of a motor vehicle

Info

Publication number: WO2007006595A1
Application number: PCT/EP2006/062166
Authority: WO
Inventors: Leopold Hellinger; Gerhard Neumann; Jeffry Steppe; Ralf David Woods
Original assignee: SIEMENS AKTIENGESELLSCHAFT öSTERREICH
Priority date: 2005-07-12
Filing date: 2006-05-09
Publication date: 2007-01-18
Also published as: AT8935U1

Abstract

The invention relates to a device for the contactless measurement of the torque that is transmitted by a shaft which is rotatably mounted in a gear housing of a motor vehicle, the shaft, at least in a torque-transmitting section, being in the form of a hollow shaft, and with an opening in the housing side of the hollow shaft being accessible from the outside through a recess in the gear housing, the device comprising: a magnetised section (8) which is formed on an inner ring surface (26) in the torque-transmitting section of the hollow shaft (1) and emits a torque-dependent magnetic field into the hollow chamber (19); and a magnetic field detector, which is arranged on a support part that can be inserted from the outside into the hollow chamber and which detects the torque-dependent magnetic field, the support part, when inserted, being mounted by means of a support bearing on a section that projects into the hollow chamber, with the other end of the support part projecting out of the recess and being attached to the gear housing.

Description

Device for measuring the torque on a transmission shaft of a motor vehicle

Technical area

The invention relates to a device for measuring a torque which is transmitted by a rotatably mounted in a transmission housing of a motor vehicle shaft, wherein the shaft is formed at least in a torque-conducting portion as a hollow shaft and wherein a housing-side opening of the hollow shaft through a recess on the transmission housing from the outside is accessible.

State of the art

For measuring forces and torques, sensors are known which exploit the effect of the inverse magnetostriction.

Magnetostriction is an effect that describes the change in geometric dimensions of a body when it is under the influence of a magnetic field. When the cause and effect are reversed, an already premagnetized body responds to mechanical deformation with a change in its magnetization. This effect is referred to as inverse magnetostriction or as Villari effect and also used in sensors that detect contactless transmitted by a shaft torque. Such a sensor is described in DE 3407917 A1. The magnetic material is first applied to the surface of a non-magnetic carrier sleeve. The carrier sleeve is then pushed onto the transmission shaft of a motor vehicle and connected to this force-conducting. When the transmission shaft is subjected to a torque, the magnetic field radiated from the magnetic material into the outer space changes. The change of the magnetic field detects a magnetic field detector mounted on the outer peripheral side.

From US 2004/0035222 Al a torque-measuring system is known in which the magnetoelastic region is also formed on an inner cylinder wall surface of a hollow shaft.

The measurement of the torque conducted by a four-wheel drive transfer case to the front and rear axles, respectively, is crucial for controlling traction, vehicle stability, braking performance and fuel economy. A measuring device in a motor vehicle exposed to magnetic and electromagnetic interference fields and harsh operating conditions.

In a transmission of a motor vehicle mechanical

Loads up to twenty times the gravitational acceleration and temperatures of over 150 degrees Celsius occur. A torque measuring system that is used in a motor vehicle transfer case, however, not only has to be built sufficiently robust. It is also necessary that the

Measuring device is easily accessible and easy to maintain. If a change is necessary in the event of a malfunction, this should be done without the removal of a Transmission shaft be possible. Furthermore, electromagnetic interference fields, which can disturb the weak measuring signals of a magnetic torque sensor, act on a torque measuring system in a motor vehicle.

Presentation of the invention

It is an object of the present invention to provide a device for detecting the torque, which is sufficiently robust to be used in a motor vehicle gearbox which is largely insensitive to interference fields and which is easy to maintain and replaceable if necessary.

This object is solved by the features of claim 1.

Advantageous embodiments of the invention are the subject of dependent claims.

According to a basic idea of the invention is the

Measuring device arranged in a hollow shaft. In a torque-conducting region of the hollow shaft, an area with a magnetization is formed on an inner ring surface. A magnetic field detector, which is arranged on a carrier part at a distance from an annular gap of this magnetized area, detects the torque-dependent magnetic field. The carrier part is mounted in an inserted state with a projecting into the cavity portion by a support bearing. With another end, the support member is led out through a recess in the transmission housing and on a

Gear housing part set outside. The arrangement of the sensor inside the hollow shaft is the measuring device well shielded against magnetic interference fields. The measuring device is easily accessible from the outside. If, in the event of a fault, the detector or the evaluation circuit has to be serviced or replaced, this does not require removal of the gear shaft. The support member additionally causes heat removal from the interior of the hollow shaft, so that the magnetic field detector is comparatively exposed to a low operating temperature.

In a very particularly preferred embodiment, the magnetization is formed directly in the material of the hollow shaft, or in other words, the magnetized region and the hollow shaft are made of a material and are designed to merge into one another. Compared to the prior art, in the annular magnetoelastic elements

Outer peripheral surfaces of waves are mounted on carrier sleeves, the production is easier and possible at a lower cost.

With regard to the required construction volume, it is favorable if the measuring device is arranged in the region of the bearing of the transmission shaft. A preferred embodiment of the invention is therefore characterized in that the hollow shaft is mounted in a, with respect to the inner ring surface radially outwardly opposite outer peripheral surface by a bearing in a gear housing part.

For an undisturbed formation of the magnetic field which is radiated from the magnetized region, it is favorable if the carrier part on which the magnetic field detector is arranged is made of a non-magnetic material. In order to keep the effect of temperature on the part of the transmission to the magnetic field detector low, it is advantageous if the outer ring or the inner ring of the support bearing, with which the support member is supported in the Holwelle, insulated by a heat insulating bushing.

In a preferred embodiment, the carrier part has a bore extending in the axial direction. This bore forms a cable duct for electrical lines which connects the magnetic field detector with an evaluation circuit arranged outside the transmission on a printed circuit board. In this way, electrical and magnetic interference are kept away both from the magnetic field detector and from the connecting lines to the transmitter.

In order to keep the effect of heat on the transmitter low, an electronics housing is provided which has a lower shell, which is made of a thermally insulating material.

In a particularly preferred embodiment, the electronics housing lower shell and the printed circuit board are each provided with a recess. In a mounted state these recesses align with the recess in the

Transmission housing part, so that the support member can be passed through these recesses and out. The support member may then be connected to a cover member formed as a heat sink, whereby to some extent operating heat can be derived from the interior of the hollow shaft to the outside. Preferably, a material from the group 40NiCrMo6, 14NiCrMol34, 20MnCrS5, 41Cr4 is used for the hollow shaft and thus also for the magnetized area.

In a very particularly preferred embodiment, the magnetic field detector includes a flux gate magnetometer module designed as an integrated circuit.

Brief description of the drawing

To further explain the invention, reference is made in the following part of the description to the drawings in which further advantageous embodiments, details and further developments of the invention can be found. It shows:

Figure 1 is a sectional view of a drive shaft in a transfer case of a motor vehicle;

FIG. 2 shows a detail drawing in the region X of the representation according to FIG. 1.

Embodiment of the invention

FIG. 1 shows a device 27 for the contactless determination of a torque, which is transmitted by a shaft designed as a hollow shaft 1 in a transfer case 6, 7 of a motor vehicle. Two

Radial shaft sealing ring 22 seal the hollow shaft 1 in the transfer case 6,7 relative to the outer space. The supply of torque takes place inside the housing 6,7 by means of a chain 11. The chain 11 is connected to a on the hollow shaft 1 on the outer peripheral side gear 12 is engaged. By this Umschlingungstrieb 11,12 the torque of the hollow shaft 1 is supplied. The hollow shaft 1 passes the torque to an output 13. The output 13 is led out in Figure 1 on the housing part 6 on the left. From this output 13, the drive power of the engine reaches the wheels of the motor vehicle.

The hollow shaft 1 is on the one hand in a driven side

Bearing 4 mounted on a front gear housing part 6. The other end of the hollow shaft 1 is rotatably supported by a drive side arranged bearing 5 in a rear gear housing part 7. The rear gear housing part 7 has a recess 25. Die

Hollow shaft 1 has a hollow interior 19 extending in the direction of the axis of rotation 23. In this interior 19, a support member 2 can be seen, which is inserted during assembly from the outside through the right in Figure 1 opening 29 of the hollow shaft 1 and the recess 25 in the housing part 7.

In the retracted state, the hollow shaft 1 is crashed left by acting as a support bearing deep groove ball bearing 3 in the hollow shaft 1 and simultaneously rotatably supported. A right end piece of the support part 2 extends through the recess 25 and is connected on the housing side by means of screws 21 with a cover part 15. The cover part 15 covers the recess 25 and in turn is bolted by fastening screws 24 to the rear gear housing part 7.

The actual torque sensor is highlighted in Figure 1 by a circle designated by X. This detail X can be seen in an enlarged view in FIG. It essentially consists of a magnetized area 8 the Holwelleninnenseite and a magnetic field detector device 9. The magnetized region 8 is radially opposite the bearing 4. The magnetized region 8 radiates a magnetic field into the cavity 19. The field lines of this magnetic field close over the

Hollow shaft 1. The operation of the torque measuring device is now as follows:

If a torque is introduced through the belt drive 11,12 on the hollow shaft 1, this passes through a torque-conducting portion of the hollow shaft 1 to the output 13. The lying between the gear 12 and output 13 part of the hollow shaft 1 is thus claimed to torsion. This twist is transmitted to the magnetized region 8. The consequence of this mechanical stress is a change in the orientation of the magnetic field lines in the region of the magnetization 8 and thus a change in the magnetic field quantities in the interior space 19. This change in the magnetic field quantities is detected by the magnetic field detector 9. The magnetic field detector 9 is fastened by a radial gap of the magnetized region 8 on the housing-fixed carrier part 2 and contains a designed as an integrated circuit flux gate magnetometer sensor module. It generates a torque-dependent electrical measurement signal, which is supplied by electrical lines 17 to an evaluation electronics 28. The transmitter 28 is located outside the gear housing 6, 7. The components of this evaluation circuit 28 are arranged on a printed circuit board 16. The circuit board 16 is located in an electronics housing 14,15, which is fixed to the right in Figure 1 gear housing part 7. In the support part 2, a bore 20 is formed (Figure 1). This bore 20 extends in the axial direction of the support member 2 and acts as a cable channel for the lines 17 between the detector 9 and circuit 28. Since the hollow shaft 1 is made of a ferromagnetic material, externally applied magnetic fields from the magnetic field detector 9 and the lines 17 are well shielded. As a result of this good shielding property, the torque can also be determined with sufficient accuracy from a comparatively weaker measuring signal, so that the magnetization 8 can be formed directly in the tempering steel of the hollow shaft 1. A separate magnetoelastic ring with a carrier sleeve, or the application of a coating of a special magnetic material, is not required.

The structural arrangement of the sensor arrangement 8,9 in the inner space 19 of a hollow shaft 1 utilizes the trend of modern transmission designs, in which the formation of transmission shafts as hollow shafts for reasons of weight saving is increasingly widespread. The measuring device according to the invention requires only a small installation volume and there are no significant changes to the transmission design required.

Since the mechanical moment is detected without contact, that is without mechanical contacts, the device according to the invention withstands the harsh operating conditions in a motor vehicle. At the same time, the device is easy to maintain. In case of disturbances of the magnetic field detector 9 and / or a break of the connecting lines 17, the maintenance can be done simply by the fixing screws 24 are released and the support member 2 together with sensor components 9 from the cavity 19 in Figure 1 in the direction from left to right out to be pulled. The electronic components on the Printed circuit board 16 are accessible by removing the lid 14 in a simple manner from the outside.

The arrangement of the magnetized region 8 immediately below the bearing seat of the groove bearing 4, there is no additional need for axial installation space for the magnetic sensor. The formation of the magnetized region 8 on the inner ring surface 26 of the hollow shaft 1 is - compared to arrangements on the outer peripheral surface of a shaft according to the prior art - cheaper because a relatively larger circumferential length for the formation of the magnetization 8 can be used.

Between the support bearing 3 and the support part 2, a heat insulating layer 10 is formed. These

Heat insulation layer 10 reduces the heat flow which is conducted from the hollow shaft 1 via the support bearing 3 on the support member 2. The carrier part 1 is made of a non-magnetic metallic material, such as aluminum. As a result, the field emitted by the magnetic region 8 is not influenced by the carrier part 2.

The transmitter 28 on the circuit board 16 is housed in an electronics housing 14, 15. This consists of an electronics housing lower shell 14 and a

Electronics Housing Lid Shell 15. The electronics housing lower shell 14 is made of a heat insulating material, for example, a polymeric material containing glass fiber portions, by injection molding. The operating temperature of the transfer case can rise to over 150 degrees Celsius. By acting as an insulator lower shell 14, the electronic components are thermally largely decoupled, so their maximum allowable Operating temperature of about 120 degrees Celsius is not exceeded. The electronics housing cover part 15 has projecting from the housing cooling fins. The electronics housing cover part 15 is fastened by fastening screws 21 with an end face of the support part 2. It has a connector 18, through which an electrical plug connection with the circuit board 16 can be produced. The support member 2 and the lid member 14 cause to some extent heat dissipation from the interior 19, which is favorable for the operating temperature of the magnetic field detector components 9.

Compilation of the reference numbers used

1 hollow shaft

2 carrier part

3 Bearings of the support member 4 bearings of the hollow shaft, the output side

5 bearings of the hollow shaft, drive side

6 Gearbox housing front

7 Transmission housing part Rear side

8 magnetized area 9 magnetic field detector

10 heat insulation

11 chain

12 gear

13 Output 14 Electronics housing lower shell

15 Electronics housing cover part, heat sink

16 circuit board

17 electrical lines

18 plug 19 cavity

20 hole in 2

21 fixing screws

22 Radial shaft seal

23 rotation axis 24 fixing screws

25 recess in 7

26 inner ring surface

27 device

28 Evaluation circuit 29 Opening in the hollow shaft

30 outer peripheral surface

31 recess

32 ring groove

Claims

claims

1. A device for measuring a torque which is transmitted by a rotatably mounted in a transmission housing of a motor vehicle shaft, wherein the shaft is formed at least in a torque-conducting portion as a hollow shaft (1), wherein a housing-side opening (29) of the hollow shaft (1) is accessible from outside through a recess (25) on a gear housing part (7), comprising:

a magnetized region (8) formed on an inner annular surface (26) in the torque-conducting section of the hollow shaft (1) and radiating a torque-dependent magnetic field into the hollow space (19),

a magnetic field detector (9) which is arranged on a carrier part (2) which can be inserted from the outside into the cavity (19) and detects the torque-dependent magnetic field, wherein - the carrier part (2) in an inserted state at one in the cavity ( 19) projecting portion by a support bearing (3) is mounted and led out with another end through the recess (25) and fixed to the transmission housing part (7).

2. Apparatus according to claim 1, characterized in that the magnetized region (8) of the same material and merging with each other with the material of the hollow shaft (1) is formed.

3. Apparatus according to claim 1 or 2, characterized in that the hollow shaft (1) at a relative to the inner ring surface (26) radially outwardly opposite outer peripheral surface (30) by a bearing (4) in the gear housing part (7) is mounted.

4. Device according to one of claims 1 to 3, characterized in that the carrier part (2) is made of a non-magnetic metallic material.

5. Device according to one of claims 1 to 4, characterized in that the carrier part (2) by a on the outer and / or inner bearing seat surface of the

Support bearing (3) formed thermal insulation bushing (10) of the hollow shaft (1) is thermally insulated.

6. Device according to one of claims 1 to 5, characterized in that the carrier part (2) has an axially extending bore (20) which forms a duct for electrical lines (17), which the magnetic field detector (9 ) connect to an evaluation circuit (28) arranged outside the transmission housing on a printed circuit board (16).

7. The device according to claim 6, characterized in that the evaluation circuit (28) in an electronics housing (14, 15) is housed, consisting of a on the gear housing part (7) adjacent heat-insulating electronics housing lower shell (14) and designed as a heat sink electronics housing Cover shell (15) is formed.

8. The device according to claim 9, characterized in that the electronics housing lower shell (14) and the printed circuit board (16) are each provided with a recess (31) in an assembled state with the Recess (25) of the gear housing part (7) are arranged in alignment with each other in the direction of a rotation axis 23, that the support part (2) through these recesses (25,31) is passed and with the designed as a heat sink electronics housing cover shell

(15) is thermally conductively connected.

9. Apparatus according to claim 8, characterized in that on the electronics housing cover shell (15) an electrical connector (18) is formed, through which an electrical connection to the circuit board

(16) can be produced.

10. Device according to one of claims 7 to 9, characterized in that the electronics housing lower shell (14) is made of a polymeric material by injection molding.

11. Device according to one of claims 7 to 9, characterized in that the electronics housing cover part (15) is made of a metallic material by injection molding.

12. Device according to one of the preceding claims, characterized in that the magnetic field detector (9) comprises a formed as an integrated circuit flux gate magnetometer sensor module.

13. Device according to one of the preceding claims, characterized in that the material of the magnetized region (8) and the hollow shaft (1) from the group 40NiCrMo6, 14NiCrMol34, 20MnCrS5, 41Cr4 is selected.