NL2024189B1 - Transmission unit with integrated torque sensor - Google Patents

Abstract

A transmission unit (1) for power take-off applications, comprising an input gear arrangement (2) connected to an input shaft member (3), an output gear arrangement (4) connected to an output 5 shaft member (5), and an idler gear member (6) connecting the input and the output shaft member (3, 5) through meshed engagement with the input and output gear arrangement (2, 4). The transmission unit (1) further comprises an idler shaft member (7) extending through the idler gear member (6), and wherein the idler gear member (6) is journaled for rotation about the idler shaft member (7). The idler shaft member (7) comprises a strain sensor (8) configured to provide 10 a sensor signal in correspondence with lateral bending/deflection (D) of the idler shaft member (7) when the transmission unit (1) in use. [Figure 1]

Description

Transmission unit with integrated torque sensor Field of the invention The present invention relates to a transmission unit with an integrated torque sensor, such as a power take-off (PTO) transmission unit with an integrated torque sensor for agricultural and/or industrial applications. Background art International application WO 2012/110617 A1 a PTO transmission system in an agricultural or industrial vehicle for transmitting power to a PTO shaft driving an implement. The PTO transmission system comprises a torque sensor operable to measure a load on a PTO output shaft and wherein the torque sensor is coupled to a control means which is operable to control the engine RPM for obtaining a PTO output shaft speed corresponding to a target PTO speed. Details on how the torque sensor specifically measures the load on the PTO output shaft are not disclosed.

Japanese patent application JPS60129453 (A) discloses a gear transmission allowing excessive torque to be automatically detected during operation. To that end the gear transmission comprises an input shaft provided with first stage small gear that meshes with a first stage large gear, wherein the first stage small gear and the first stage large gear are helical gears. A load cell is installed between a bearing fitted to an input shaft and a bearing cover attached to a gear casing. Axial thrust force generated by meshing of the first stage large gear is supported by the bearing and detected by the load cell. Although the transmitted torque can be determined from the axial thrust measured by the load cell, the helical gears generate an axial load on the input shaft and in particular the bearing, thereby restricting the amount of torque that can be transmitted by the gear transmission.

Summary of the invention The present invention seeks to provide a transmission unit with an integrated torque sensor, such as a transmission unit for power take-off (PTO) applications in agriculture and/or industry. The transmission unit is compact, exhibits reduced design complexity, and can be manufactured at relatively low cost, and wherein the transmission unit allows for transmitted torque loads to be accurately and reliably measured.

According to the present invention, a transmission unit as defined in the preamble above provided comprising an input gear arrangement connected to an input shaft member of the transmission unit, an output gear arrangement connected to an output shaft member of the transmission unit, and an idler gear member connecting the input and the output shaft member through meshed engagement with the input and output gear arrangement.

An idler shaft member is provided and extends through the idler gear member which is journaled for rotation about the idler shaft member. The idler shaft member then comprises a strain sensor which is configured to provide a sensor signal in correspondence with lateral bending/deflection of the idler shaft member when the transmission unit in use.

According to the present invention, the transmission unit allows for convenient measurement of lateral shaft bending/deflection of the idler shaft member in response to torque being transmitted from the input gear arrangement to the output gear arrangement when the transmission unit is in use. In particular, because the idler gear member is in meshed engagement with the input and output gear arrangement, tooth forces imposed on the idler gear member are transmitted to the idler shaft member which then deflects laterally in correspondence with the size/intensity of these tooth forces. The lateral deflection of the idler shaft member can therefore be taken as a measure of torque being transmitted by the transmission unit when in use, wherein the need for measuring torque in rotational manner is eliminated.

By only measuring lateral shaft deflection of the idler shaft member in response to transmitted torque greatly simplifies the design of the transmission unit. For example, communicatively connecting the strain sensor for receiving the sensor signal for further processing is greatly simplified. For example, in an advantageous embodiment the transmission unit allows for a simple wired connection to the strain sensor for distributing the sensor signal to other components of the transmission unit. In particular, since only lateral deflection of the idler shaft member is measured by the strain sensor, an advantageous embodiment is provided wherein the idler shaft member does not rotate about its longitudinal/centre axis and as such the strain sensor arranged on the idler shaft member does not rotate to measure the shaft deflection. In this way the design complexity of the transmission unit is greatly reduced as well as reducing manufacturing costs thereof. Therefore, in an advantageous embodiment the idler shaft member may be arranged rotationally immovable/stationary around its longitudinal/centre axis in the transmission unit.

Short description of drawings The present invention will be discussed in more detail below, with reference to the attached drawings, in which Figure 1 shows a three dimensional view of a transmission unit according to an embodiment of the present invention; Figure 2 shows a side view of a transmission unit according to an embodiment of the present invention; Figure 3 shows a cross section of an idler gear member and idler shaft member of the transmission unit according to an embodiment of the present invention; and wherein Figure 4 shows a schematic view of a PTO transmission system according to an embodiment of the present invention.

Description of embodiments Figure 1 and 2 show a three dimensional view and a side view, respectively, of a 40 transmission unit 1 according to an embodiment of the present invention. In the embodiments shown, the transmission unit comprises an input gear arrangement 2 which is connected to an input shaft member 3 of the transmission unit 1. An output gear arrangement 4 is provided and connected to an output shaft member 5 of the transmission unit 1. In an exemplary application, the input shaft member 3 may be connected to a drive shaft of a vehicle that provides power to the transmission unit 1 and wherein the output shaft member 5 may be connected to a driven shaft of an implement to be driven by the transmission unit 1.

The transmission unit 1 further comprises an idler gear member 6 that connects the input and the output shaft member 3, 5 through meshed engagement with the input and output gear arrangement 2, 4. An idler shaft member 7 is provided and extends through the idler gear member 6 which is then journaled for rotation about the idler shaft member 7. As detailed further below, in an embodiment the idler shaft member 7 may comprise a longitudinal/centre axis Cs and may be arranged rotationally immovable/stationary about the longitudinal/centre axis Cs in the transmission unit 1, see Figure 3.

As depicted in Figure 1, the idler shaft member 7 comprises a strain sensor 8 which is configured to provide a sensor signal in correspondence with lateral shaft bending/deflection “D” of the idler shaft member 7 when the transmission unit 1 is in use, i.e. under load, i.e. when torque is transmitted through the transmission unit 1.

It is worth noting that the strain sensor 8 may be configured to convert various types of forces applied to it for generating a sensor signal indicative of a torque load on the transmission unit 1. That is, the strain sensor 8 may use various phenomena for detecting lateral bending/deflection D of the idler shaft member 7. For example, the strain sensor 8 may be configured to measure or detect forces, magnetism, pressures, tension and/or weight applied to the strain sensor 8 when the transmission unit 1 is under load, i.e. when the idler shaft member 7 is under load. Also, the strain sensor 8 may be configured to measure expansion and/or contraction of the strain sensor 8 when the idler shaft member 7 is under load. Al these physical phenomena just mentioned may be used either individually or in combination in order to measure/detect the lateral bending/deflection D of the idler shaft member 7. As such the strain sensor 8 may be viewed as a generalised “force” sensor. In an advantageous embodiment, the strain sensor 8 is configured for measuring expansion and/or contraction of one or more portions, e.g. outer surface portions, of the idler shaft member 7 when it bends/deflects under load.

Referring to Figure 2, when the transmission unit 1 is in use the meshed engagement of the idler gear member 6 with the input and output gear arrangement 2, 4 produces tooth forces F1 and F2 on the idler gear member 6 in the exemplary directions shown. These tooth forces F1, F2 on teeth T of the idler gear member 6 correspond to the exemplary rotational directions shown, e.g. the clockwise direction r1 of the input gear arrangement 3, the counter clockwise direction r2 of the idler gear member 6, and the clockwise and counter clockwise directions r3, r4 of the output gear arrangement 4. The tooth forces F1, F2 yield a resultant force F on the idler gear member 6 wherein the resultant force F is subsequently transmitted to the idler shaft member 7. Because of the resultant force F, the idler shaft member 7 bends or deflects in the lateral direction “D” as 40 shown.

It is worth noting that in an advantageous embodiment, the teeth T of the idler gear member 6 are straight cut teeth T, so wherein the idler gear member 6 is a straight cut gear to avoid axial loads on the idler member 6 and the idler shaft member 7 when the transmission unit 1 under load. In such case there are no tooth forces on teeth T of the idler gear member 6 in a longitudinal direction of the idler gear member 6 and the idler shaft member 7, thereby circumventing the need for axial bearings and/or additional axial support of the idler shaft member

7. Of course, should it still be required then in an alternative embodiment the teeth T of the idler gear member 6 may be helical teeth and so the idler gear member 6 may be a helical gear member in such case.

According to the present invention, there is no need to measure torque in rotational manner by mounting a sensor on e.g. the rotatable input shaft member 3 or the rotatable output shaft member 5. Indeed, only lateral deflection/bending D of the idler shaft member 7 relates to transmitted torque through the tooth forces F1, F2. As such it is possible, in an embodiment, to mount the idler shaft member 7 rotationally immovable about its longitudinal axis Cs in the transmission unit 1. For example, the idler shaft member 7 may be held stationary by affixing the idler shaft member 7 to a casing part of the transmission unit 1.

In an advantageous embodiment, the sensor signal provided by the strain sensor 8 may be a linear sensor signal in correspondence with the lateral bending/deflection D of the idler shaft member 7 when the transmission unit 1 is in use, thereby simplifying torque estimation from the sensor signal.

Because the idler shaft member 7 need not rotate about its own longitudinal axis Cs in the transmission unit 1, the strain sensor 8 need not rotate. Consequently, a simple wired connection “S" as shown in Figure 1 may be sufficient for connecting the strain sensor 8 to peripheral components that should receive the sensor signal for further processing. In this way the design complexity of the transmission unit 1 is greatly reduced as well as having significantly lower manufacturing costs. Of course, in alternative embodiment the transmission unit 1 may comprise a wireless system connected to the strain sensor 8 for providing the sensor signal to peripheral components in wireless manner.

Since in an embodiment the strain sensor 8 may remain stationary relative to transmission unit 1, there is no need for “brushed” or sliding connecting interfaces with a rotating component to transfer the sensor signal from the strain sensor 8 to peripheral components. As a result, mechanical transmission losses are eliminated when communicatively interfacing with the strain sensor 8.

Referring to Figure 3, a cross section of an idler gear member 6 and an idler shaft member 7 of the transmission unit 1 is depicted according to an embodiment of the present invention. In the embodiments shown, the idler shaft member 7 comprises a first and a second shaft end portion 9, 10 arranged at opposing sides of the idler gear member 6 for support thereof in the transmission unit 1. For example, the opposing first and second shaft end portions 9, 10 may be affixed in a casing part (not shown) of the transmission unit 1 such that the idler shaft 40 member 7 remains, substantially, rotationally immovable/stationary about its longitudinal axis Cs.

In a further embodiment, the opposing first and second shaft end portions 9, 10 may be affixed, e.g. clamped, in a casing part (not shown) of the transmission unit 1 such that the idler shaft member 7 remains rotationally immovable about its longitudinal axis Cs as well as linearly immovable, e.g. linearly immovable in the direction of the longitudinal axis Cs of the idler shaft 5 member 7.

As further shown, the first shaft end portion 9 is at a first support distance W1 from the idler gear member 6 and wherein the second shaft end portion 10 is at a second support distance W2 from the idler gear member 6.

In this embodiment the idler gear member 6 is arranged between the first and second shaft end portions 9, 10, wherein the first and second support distances W1, W2 may be chosen to achieve a desired lateral shaft deflection behaviour to be registered by the strain sensor 8. For example, increasing the first and second support distances W1, W2 may increase the lateral shaft deflection D under the resultant force/load F more pronounced and easier to detect.

In an exemplary embodiment, the first and second support distances W1, W2 may be different. For example, when particular space requirements for the strain sensor 8 are to be met, an embodiment is conceivable wherein the strain sensor 8 is located on the idler shaft member 7 between the first shaft end portion 9 and the idler gear member 6 so that the first support distance W1 may be larger than the second support distance W2 to make room for the strain sensor 8.

Allowing the first and second support distances W1, W2 to differ provides more design flexibility. However, this may introduce asymmetric or non-uniform lateral shaft deflection D between the first and second shaft end portions 9, 10 of the idler shaft member 7 along the longitudinal/centre axis Cs thereof. To accurately deduce transmitted torque from such asymmetric/non-uniform lateral shaft deflection D may require further processing and electronic compensation of the sensor signal provided by the strain sensor 8.

It is further noted that asymmetric lateral shaft deflection D caused by different first and second support distances W1, W2 may cause the idler gear member 6 to slightly rotate/pivot over the pivot angle a with respect to the depicted centre gear axis Cg, which is substantially perpendicular to the longitudinal/centre axis Cs. As a result, when the idler shaft member 7 is under the resultant load F, the idler gear member 6 may not be in evenly distributed meshed engagement, i.e. parallel to the longitudinal/centre axis Cs, with the first and second gear arrangements 2, 4 along a tooth length L of the teeth T. In such case there is provided an embodiment wherein the shape (e.g. the teeth T) of the idler gear member 6 may be adapted to cope with such rotation of the idler gear member 6 over the pivot angle a.

In an advantageous embodiment, the first support distance W1 is equal to the second support distance W2, so wherein the idler gear member 6 is centred between the first and second shaft end portions 9, 10. This embodiment allows for a symmetric or uniform lateral shaft deflection D of the idler shaft member 7 between the first and second shaft end portions 9, 10. Such symmetric or even lateral shaft deflection D under the resultant load F will prevent pivoting of the idler gear member 6 over the pivot angle a as outlined above, so that an evenly distributed meshed engagement of the idler gear member 6 with the first and second gear arrangements 2, 4 is achieved.

According to the present invention, the idler shaft member 7 comprises the strain sensor 8 which is configured to provide a sensor signal in response to lateral bending/deflection D of the idler shaft member 7 when the transmission unit 1 is under load. As depicted in Figure 1 and 3, there is an embodiment wherein the idler shaft member 7 comprises one or more shaft recesses 11, 12, 13, 14 adjacent to the idler gear member 6 at one or more corresponding recess distances x1, x2, x3, x4 from the idler gear member 6. The strain sensor 8 may then comprise one or more strain gauge members 8a, 8b, 8c, 8d each of which is arranged in a corresponding shaft recess of the one or more shaft recesses 11, 12, 13, 14.

In this embodiment, each of the one or more shaft recesses 11, 12, 13, 14 may be viewed as a blind bore that extends radially inward from an outer circumferential surface 18 of the idler shaft member 7, and wherein each of the strain gauge members 8a, 8b, 8c, 8d is arranged on a bottom part of a corresponding shaft recesses 11, 12, 13, 14. Here, the one or more recesses 11, 12, 13, 14 facilitate lateral shaft deflection D of the idler shaft member 7 and allows for improved registration/measurement of the lateral shaft deflection D by each of the one or more strain gauge members 8a, 8b, 8c, 8d.

Note that the one or more strain gauge members 8a, 8b, 8c, 8d may be configured to convert various types of forces applied to it for generating a sensor signal indicative of a torque load on the transmission unit 1. That is, the one or more strain gauge members 8a, 8b, 8c, 8d may use various phenomena for detecting lateral bending/deflection D of the idler shaft member

7. For example, the one or more strain gauge members 8a, 8b, 8c, 8d may be configured to measure or detect forces, magnetism, pressures, tension and/or weight applied to them when the transmission unit 1 is under load, i.e. when the idler shaft member 7 is under load. Also, the one or more strain gauge members 8a, 8b, 8c, 8d may also be configured to measure expansion and/or contraction of themselves when the idler shaft member 7 is under load.

As depicted, in an advantageous embodiment each of the one or more shaft recesses 11, 12, 13, 14 is arranged between one of the first or second shaft end portions 9, 10 and the idler gear member 6. This facilitates accurate measurement of the lateral shaft deflection D between the first and second shaft end portions 9, 10 and the idler gear member 6 when the idler shaft member 7 deflects between the first and second shaft end portions 9, 10 under load.

In an advantageous embodiment, each of the one or more corresponding recess distances x1, x2, x2, x4 are equal, thereby achieving a symmetrical strain gauge arrangement for improved accuracy of strain measurements as well as measurement robustness under various temperature variations.

It is worth noting that it is not required to utilize a plurality of strain gauge members 8a, 8b 8c, 8d arranged in a corresponding plurality of shaft recesses 11, 12, 13, 14. That is, in an embodiment the strain sensor 8 may comprise a single strain gauge member 8a, and wherein the idler shaft member 7 is provided with a single shaft recess 11 having arranged therein the single 40 strain gauge member 8a. Here, the single shaft recess 11 may be arranged between the first shaft end portion 9 and the idler shaft member 6 at a first recess distance x1 from the idler gear member 6. The first recess distance x1 may be chosen to achieve optimal deflection measurements from the single strain gauge member 8a.

Instead of using a single strain gauge member 8a, a plurality of strain gauge members may be considered. For example, in an exemplary embodiment the strain sensor 8 may comprise two strain gauge members 8a, 8b and wherein the idler shaft member 7 is provided with two shaft recesses 11, 12 each having arranged therein one of the two strain gauge members 8a, 8b. As depicted in Figure 3, the two shaft recesses 11, 12 may be arranged at opposing sides of the idler gear member 6. That is, a first shaft recess 11 of the two shaft recesses 11, 12 may be arranged between the first shaft end portion 9 and the idler gear member 6 at a first recess distance x1, and wherein a second shaft recess 12 of the two shaft recesses 11, 12 may be arranged between the second shaft end portion 10 and the idler gear member 6 at a second recess distance x2. The first and second recess distances x1, x2 may of course be chosen to achieve optimal deflection measurements. In this embodiment, having two opposing strain gauge members 8a, 8b on both sides of the idler gear member 6 may render torque measurements more accurate, consistent and less susceptible to temperature variations.

In an advantageous embodiment, the two recess distances x1, x2 may be equal to obtain symmetric deflection measurements between the first and second shaft end portions 9, 10 for improved torque measurement accuracy, consistency and reduced measurement variability thereof.

Note that the embodiment of Figure 3 shows a specific example of how a plurality of strain gauge members 8a, 8b, 8c, 8d may be utilized. In the depicted embodiment, four strain gauge members 8a, 8b, 8c, 8d are provided wherein each strain gauge member is arranged in one of four shaft recesses 11, 12, 13, 14. As shown, the four shaft recesses 11, 12, 13, 14 are distributed “around” the idler gear member 6. That is, a first shaft recess 11 is arranged between the first shaft end portion 9 and the idler gear member 6 and a second shaft recess 12 is arranged between the second shaft end portion 10 and the idler gear member 6. Here, the first and second shaft recesses 11, 12 are arranged at a same side of the idler shaft member 7.

Further, a third shaft recess 13 is arranged between the second shaft end portion 10 and the idler gear member 6 and a fourth shaft recess 14 is arranged between the first shaft end portion 9 and the idler gear member 6. The third and fourth shaft recesses 13, 14 are arranged at an opposing side of the idler shaft member 7, so wherein the third shaft recess 13 is arranged opposite the second shaft recess 12 and wherein the fourth shaft recess 14 is arranged opposite the first shaft recess 11.

This particular embodiment allows for optimal distributed deflection measurement by the strain gauge members 8a, 8b, 8c, 8d, e.g. through compression and/or expansion thereof, thereby improving torque measurement accuracy and consistency under various temperature conditions.

In an advantageous embodiment, the corresponding recess distances x1, x2, x2, x4 of the four shaft recesses 11, 12, 13, 14 may be equal, so that a symmetric distribution of the four strain gauge members 8a, 8b, 8c, 8d with respect to the idler gear member 6 is achieved for optimal torque measurement.

It is worth noting that in a more generalised embodiment, the strain sensor 8, e.g. comprising one or more strain gauge members 8a, 8b, 8c, 8d, may be arranged on the above mentioned outer circumferential surface 18 of the idler shaft member 7 and arranged adjacent to the idler gear member 6. For example, each of the one or more strain gauge members 8a, 8b, 8c, 8d may be arranged on the outer circumferential surface 18 between one of the first or second shaft end portions 9, 10 and the idler gear member 6 as depicted in Figure 3. In this embodiment the one or more shaft recesses 11, 12, 13, 14 need not exist and the one or more recess distances x1, x2, x3, x4 may then be seen as gauge/sensor distances x1, x2, x3, x4 of the one or more strain gauge members 8a, 8b, 8c, 8d.

Therefore, each of the one or more strain gauge members 8a, 8b, 8c, 8d may be placed on the outer circumferential surface 18 of the idler shaft member 7 at these gauge distances x1, x2, x3, x4 from the idler gear member 6. Of course, in yet another embodiment the idler shaft member 7 may comprise one or more shaft recesses 11, 12, 13, 14 adjacent to the idler gear member 6 at one or more corresponding recess distances x1, x2, x3, x4 from the idler gear member 6, i.e. between the first and second shaft end portions 9, 10 and the idler gear member 6. The strain sensor 8 may then comprise one or more strain gauge members 8a, 8b, 8c, 8d each of which is arranged on the outer circumferential surface 18 of the idler shaft member 7 between the first and second shaft end portions 9, 10 and the idler gear member 6. However, in this case the one or more strain gauge members 8a, 8b, 8c, 8d are not arranged in the one or more shaft recesses 11, 12, 13, 14 but away therefrom on the outer circumferential surface 18 of the idler shaft member 7. In this way the shaft recesses 11, 12, 13, 14 may still facilitate lateral shaft bending/deflection D of the idler shaft member 7, but wherein the one or more strain gauge members 8a, 8b, 8c, 8d are placed on the outer circumferential surface 18 away from the shaft recesses 11, 12, 13, 14 for measuring the lateral shaft bending/deflection D, e.g. through compression and/or expansion of each strain gauge members 8a, 8b, 8c, 8d.

Referring to Figure 1, it may be advantageous to design the idler shaft member 7 in such a way so that a particular lateral shaft deflection D is achieved to optimize deflection measurement by the strain sensor 8. To that end an embodiment is conceivable wherein the idler shaft member 7 comprises one or more circumferential grooves 15 that are arranged adjacent to the idler gear member 6. In a particular embodiment, the idler shaft member 7 may comprises two circumferential grooves 15 arranged on opposite sides of the idler gear member 6, thus wherein a first circumferential groove is arranged between the first shaft end portion 9 and the idler gear member 6, and wherein a second circumferential groove is arranged between the second shaft end portion 10 and the idler gear member 8. In this way it is possible to achieve a particular lateral deflection D of the idler shaft member 7. In a further embodiment it is possible to combine one or more circumferential grooves 15 with one or more shaft recesses 11, 12, 13, 14 to further improve deflection measurements from which a torque load on the transmission unit 1 may be deduced. 40 For example, two circumferential grooves 15 may be arranged, each on either side of the idler gear member 6 at the same recess distances x1, x2 of a first and a second shaft recess 11, 12 as depicted in Figure 3.

As mentioned above, the idler gear member 6 is journaled for rotation about the idler shaft member 7. To achieve this there is provided an embodiment wherein the transmission unit 1 comprises one or more radial bearings 16, 17 arranged on the idler shaft member 7 and arranged within the idler gear member 6. The one or more radial bearings 16, 17 allow forces F1, F2 imposed on the idler gear member 6 to be transferred in even fashion to the idler shaft member 7. In an exemplary embodiment, the one or more radial bearings 16, 17 may be ball bearings, cylindrical roller bearings, tapered roller bearings etc.

As further depicted in Figure 3, in an embodiment the transmission unit 1 may comprise two adjoining radial bearing 18, 17 arranged on the idler shaft member 7 and within the idler gear member 6, thereby achieving even force distribution along the idler shaft member 7 when the idler gear member 6 is under load.

It is interesting to note that the idler shaft member 7 may be machined to allow for direct interference or transition fit with one or more radial bearings 16, 17 without compromising torque measuring capabilities through lateral shaft deflect D of the idler shaft member 7. To that end an embodiment is provided wherein the idler shaft member 7 comprises the outer circumferential surface 18 which is configured, e.g. machined, for interference or transition fit with the one or more radial bearings 16, 17. In this way the idler shaft member 7 can be directly fitted with one or more radial bearings 16, 17 and thus provide immediate support to the one or more radial bearings 16, 17 whilst at the same time allow for lateral shaft deflection D to be measured by the strain sensor 8 for determining the torque load.

According to the present invention there are various arrangements possible for the input and output gear arrangements 2, 4. As depicted in Figure 1 and 2, in an embodiment the input gear arrangement 2 comprises an input gear member 19 arranged on the input shaft member 3, and wherein the output gear arrangement 4 comprises an output gear member 20 arranged on the output shaft member 5. An auxiliary idler gear member 21 is arranged on an auxiliary idler shaft member 22, wherein the output gear member 20 is in direct meshed engagement with the auxiliary idler gear member 21. The idler gear member 6 is then in direct meshed engagement with the input gear member 19 and the auxiliary idler gear member 21. This particular embodiment allows for opposite rotation directions r1, r4 of the input and output shaft members 3, 5 whilst providing torque measurement through the idler shaft member 7. The actual sizes of the input gear member 19, the output gear member 20, the idler gear member 6 and the auxiliary idler gear member 21 may be chose to achieve a particular speed reduction (or speed increase) from the input shaft member 3 to the output shaft member 5.

It is worth noting that the embodiment of Figures 1 and 2 could be adapted wherein the idler shaft member 7 and the auxiliary idler shaft member 22 are interchanged/swapped, so that the idler gear member 6 is in direct meshed engagement with the output gear member 20 and wherein the auxiliary idler gear member 21 is in direct meshed engagement with the input gear 40 member 19 and the idler gear member 6. Such an embodiment would not change the torque measurement capabilities of the transmission unit 1 as the idler shaft member 7 still exhibits lateral shaft deflection D caused by tooth forces F1, F2 on the idler gear member 6.

Moreover, an embodiment is conceivable wherein the auxiliary idler shaft member 22 comprises a further strain sensor (not shown) for measuring the torque in similar fashion as the strain sensor 8 on the idler shaft member 7.

In an alternative embodiment (not shown), it is possible to have identical rotation directions r1, r4 for the input and output shaft members 3, 5. For example, the input gear arrangement 2 may comprise an input gear member 19 arranged on the input shaft member 3, wherein the output gear arrangement 4 comprises an output gear member 20 arranged on the output shaft member 5, and wherein the idler gear member 6 is in direct meshed engagement with the input gear member 19 and the output gear member 20. This embodiment eliminates the auxiliary idler gear member 21 and auxiliary idler shaft member 22 as depicted in Figure 1 and 2, thereby allowing the input and output shaft members 3, 5 to rotate in the same direction.

In a more generalised embodiment it is understood that the transmission unit 1 may utilize an arbitrary number of auxiliary idler gear members 21 in addition to the idler gear member 6, wherein the auxiliary idler gear members 21 are in meshed engagement with the idler gear member 6 and the input and output gear arrangements 2, 4. In particular, the idler gear member 6 and the one or more auxiliary idler gear members 21 are then in meshed engagement with the input and output gear arrangements 2, 4 and arranged there between for connecting the input and output shaft member 3, 5. The actual location of the idler gear member 6 with respect to the one or more auxiliary idler gear members 21 may then be varied according to specifications, e.g. to achieve a particular rotational direction for the input and output shaft members 3, 5. So it is not required that the idler gear member 6 directly meshes with an input gear member 19 and as such it is likewise possible that the idler gear member 6 directly meshes with an output gear member 20 instead.

Moreover, it is likewise possible that the idler gear member 6 is arranged between two auxiliary idler gear members 21 and thus only meshes directly with these two auxiliary idler gear members 21, wherein the two auxiliary idler gear members 21 in turn mesh with the input and output gear arrangement 2, 4, e.g. the input and output gear members 19, 20.

Therefore, in a more general embodiment, the input gear arrangement 2 may comprise an input gear member 19 arranged on the input shaft member 3, wherein the output gear arrangement 4 comprises an output gear member 20 arranged on the output shaft member 5, and wherein the transmission unit 1 further comprises one or more auxiliary idler gear members 21 connecting the input and the output shaft member 3, 5 through meshed engagement with the idler gear member 6 and input and output gear members 19, 20. The transmission unit 1 may then further comprise an auxiliary idler shaft member 22 for each of the one or more auxiliary idler gear members 21 and extending there through, wherein each auxiliary idler gear member 21 is journaled for rotation about a corresponding auxiliary idler shaft member 22.

Should it be required that the rotation direction r1 of the input gear member 19 and the 40 rotation direction r4 of the output gear member 20 are the same, see Figure 2, then an exemplary embodiment is conceivable wherein two auxiliary idler gear members 21 may be used in conjunction with the idler gear member 8, thus giving in total three idler gear members for meshed connecting with the input and output gear members 19, 20. From Figure 1 it is further seen that in an embodiment all gear members 6, 19, 20, 21 may be straight cut gear members, thereby eliminating axial forces on the various the shaft members 3, 5, 7, 22. Of course, should it be needed then in an embodiment all gear members 6, 19, 20, 21 may be helical gear members.

Figure 1 depicts a further embodiment wherein the output gear arrangement 4 comprises a clutch member 23 which is configured for coupling and decoupling the output shaft member 5 from the input shaft member 3. This allows the transmission unit 1 to enable or stop torque delivery to the output shaft member 5 when required. In the depicted embodiment, the clutch member 23 is configured for coupling and decoupling the output shaft member 5 from the output gear member 20.

According to the present invention, the transmission unit 1 provide an integrated torque sensor based on the sensor signal provided by the strain sensor 8, wherein the transmission unit 1 may be used for power take-off (PTO) applications in the agricultural and/or industrial sector. For example, in agricultural applications it is often required that a vehicle, e.g. a tractor, needs to operate a ground engaging implement by supplying power from the main engine of the vehicle to the implement. To that end the vehicle typically comprises a PTO drive shaft in the front or rear of the vehicle coupled to the main engine. The PTO drive shaft is then coupled to a PTO driven shaft of the ground engaging implement so that power/torque is supplied thereto.

In many cases the power/torque delivered by the PTO drive shaft is limited, particularly when the PTO drive shaft is a front PTO drive shaft, i.e. when the PTO drive shaft is located in the front of the vehicle. To cope with such power/torque limitations, the transmission unit 1 of the present invention allows for control, e.g. by a human operator or an autonomous controller unit, by reading or measuring the torque load on the transmission unit 1 as torque is supplied to the input shaft member 3 by the PTO drive shaft. The torque load measured by the transmission unit 1 may then be used by the autonomous controller unit or human operator for regulating the torque delivered by the PTO drive shaft to remain within a particular power or torque band/limit.

In view of the above, another aspect of the present invention relates to a PTO transmission system, wherein the PTO transmission system allows a vehicle to operate an implement through the PTO transmission system in a controlled manner.

Figure 4 shows a schematic view of a PTO transmission system 24 according to an embodiment of the present invention. In the embodiment shown, the PTO transmission system 24 comprises the transmission unit 1 as described above and wherein the PTO transmission system 24 is configured for being mounted on or connected to a vehicle 25, e.g. a tractor. The input shaft member 3 of the transmission unit 1 is configured for connection to a PTO drive shaft 26 of the vehicle 25 and the output shaft member 5 of the transmission unit 1 is configured for connection to a PTO driven shaft 27 of an implement 28, such as a ground engaging implement.

According to the present invention, the PTO transmission system 24 may utilize the integrated torque sensor of the transmission unit 1 based on the sensor signal provided by the strain sensor 8. Doing so allows the torque delivered by the PTO drive shaft 26 to be determined for feedback/control purposes, so that the torque provided by the PTO drive shaft 26 can be maintained within predefined limits.

In an embodiment, the PTO transmission system 24 may comprise a controller unit 29, e.g. an autonomous controller unit, which is communicatively coupled (c1) to the strain sensor 8 of the transmission unit 1 for receiving the sensor signal, and wherein the controller unit 29 is communicatively coupled (c2} to the vehicle 25 for controlling the power/torque provided by the PTO drive shaft 26 in response to the sensor signal.

In this way, automated control of the PTO transmission system 24 is possible.

That is, in an advantageous embodiment the controller unit 29 may be configured to autonomously maintain the delivered power/torque to the PTO drive shaft 26 within particular limits.

In another embodiment, the PTO transmission system 24 may further comprise a controller unit 29 communicatively coupled (c1) to the strain sensor 8 of the transmission unit 1 for receiving the sensor signal and wherein the controller unit 29 is communicatively coupled (c2} to a display device (not shown), e.g. a display device on the vehicle 25, which is configured for displaying operational information of the PTO transmission system 24 to e.g. a human operator for controlling power/torque provided by the vehicle 25 on the PTO drive shaft 26 in response to the sensor signal.

Being able to control the output power/torque by means of the PTO transmission system 24 is particularly advantageous for a vehicle 25 which is to operate an implement 28 by means of a PTO drive shaft 26 on a front side 30 of the vehicle 25. In order to allow for such controlled operation of the implement 28, an embodiment is provided wherein the PTO transmission system 24 is a Front PTO Transmission system 24 configured for being mounted on or connected to the front side 30 of the vehicle 25 and wherein the PTO drive shaft 26 is a Front PTO drive shaft of the vehicle 25. In an advantageous embodiment, the controller unit 29, e.g. an autonomous controller unit, is communicatively coupled (c1) to the strain sensor 8 of the transmission unit 1 for receiving the sensor signal, and wherein the controller unit 29 is communicatively coupled (c2) to the vehicle 25, or a display device (not shown) for a human operator, for controlling the power/torque provided by the Front PTO drive shaft 26 in response to the sensor signal received from the strain sensor 8. In view of the above detailed description, the present invention can now be summarized by the following embodiments: Embodiment 1. A transmission unit (1) for power take-off applications, comprising an input gear arrangement (2) connected to an input shaft member (3) of the transmission unit (1), an output gear arrangement (4) connected to an output shaft member (5) of the transmission unit (1), and 40 an idler gear member (6) connecting the input and the output shaft member (3, 5) through meshed engagement with the input and output gear arrangement (2, 4); wherein the transmission unit (1) further comprises an idler shaft member (7) extending through the idler gear member (6) and wherein the idler gear member (6) is journaled for rotation about the idler shaft member (7); and wherein the idler shaft member (7) comprises a strain sensor (8) configured to provide a sensor signal in correspondence with lateral bending (D) of the idler shaft member (7) when the transmission unit (1) in use. Embodiment 2. The transmission unit according to embodiment 1, wherein the idler shaft member (7) comprises a first and a second shaft end portion (9, 10) arranged at opposing sides of the idler gear member (6) for support thereof in the transmission unit (1), wherein the first shaft end portion (9) is at a first support distance (W1) from the idler gear member (6) and wherein the second shaft end portions (10) is at a second support distance (W2) from the idler gear member (6). Embodiment 3. The transmission unit according to embodiment 2, wherein the first support distance (W1) is equal to the second support distance (W2). Embodiment 4. The transmission unit according to any one of embodiments 1-3, wherein the idler shaft member (7) comprises one or more shaft recesses (11, 12, 13, 14) adjacent to the idler gear member (6) at one or more corresponding recess distances (x1, x2, x3, x4) from the idler gear member (6), and wherein the strain sensor (8) comprises one or more strain gauge members (8a, 8b, 8c, 8d) each of which is arranged in a corresponding shaft recess of the one or more shaft recesses (11,12, 13, 14).

Embodiment 5. The transmission unit according to embodiment 4, wherein the one or more corresponding recess distances (x1, x2, x2, x4) are equal. Embodiment 6. The transmission unit according to any one of embodiments 1-5, wherein the idler shaft member (7) comprises one or more circumferential grooves (15) adjacent to the idler gear member (6). Embodiment 7. The transmission unit according to any one of embodiments 1-8, further comprising one or more radial bearings (16, 17) arranged on the idler shaft member (7) and arranged within the idler gear member (6). Embodiment 8. The transmission unit according to embodiment 7, wherein the idler shaft member (7) comprises an outer circumferential surface (18) configured for interference fit or transition fit with the one or more radial bearings (16, 17). 40

Embodiment 9. The transmission unit according to any one of embodiments 1-8, wherein the input gear arrangement (2) comprises an input gear member (19) arranged on the input shaft member (3), and wherein the output gear arrangement (4) comprises an output gear member (20) arranged on the output shaft member (5), and wherein the idler gear member (8) is in direct meshed engagement with the input and output gear member (19, 20). Embodiment 10. The transmission unit according to any one of embodiments 1-8, wherein the input gear arrangement (2) comprises an input gear member (19) arranged on the input shaft member (3), wherein the output gear arrangement (4) comprises an output gear member (20) arranged on the output shaft member (5), and wherein the transmission unit (1) further comprises an auxiliary idler gear member (21) arranged on an auxiliary idler shaft member (22), wherein the output gear member (20) is in direct meshed engagement with the auxiliary idler gear member (21), and wherein the idler gear member (6) is in direct meshed engagement with the input gear member (19) and the auxiliary idler gear member (21).

Embodiment 11. The transmission unit according to any one of embodiments 1-8, wherein the input gear arrangement (2) comprises an input gear member (19) arranged on the input shaft member (3), wherein the output gear arrangement (4) comprises an output gear member (20) arranged on the output shaft member (5), and wherein the transmission unit (1) further comprises one or more auxiliary idler gear members (21) connecting the input and the output shaft member (3, 5) through meshed engagement with the idler gear member (6) and input and output gear members (19, 20); and wherein the transmission unit (1) further comprises an auxiliary idler shaft member (22) for each auxiliary idler gear member (21) and extending there through, wherein each auxiliary idler gear member (21) is journaled for rotation about a corresponding auxiliary idler shaft member (22).

Embodiment 12. The transmission unit according to any one of embodiments 1-11, wherein the idler gear member (6) is a straight cut gear member.

Embodiment 13. The transmission unit according to any one of embodiments 1-12, wherein the output gear arrangement (4) comprises a clutch member (23) configured for coupling and decoupling the output shaft member (5) from the input shaft member (3).

Embodiment 14. The transmission unit according to any one of embodiments 1-13, wherein the sensor signal provided by the strain sensor (8) is a linear sensor signal in correspondence with 40 the lateral bending (D) of the idler shaft member (7) when the transmission unit (1) is in use.

Embodiment 15. A PTO transmission system (24) comprising the transmission unit (1) according to any one of embodiments 1-14, wherein the PTO transmission system (24) is configured for being mounted on a vehicle (25), wherein the input shaft member (3) of the transmission unit (1) is configured for connection to a PTO drive shaft (26) of the vehicle (25) and wherein the output shaft member (5) of the transmission unit (1) is configured for connection to a PTO driven shaft (27) of an implement (28). Embodiment 16. The PTO transmission system according to embodiment 15, further comprising a controller unit (29) communicatively coupled (c1) to the strain sensor (8) of the transmission unit (1) for receiving the sensor signal, and wherein the controller unit (29) is communicatively coupled (c2} to the vehicle (25) for controlling power/torque provided by the vehicle (25) on the PTO drive shaft (26) in response to the sensor signal. Embodiment 17. The PTO transmission system according to embodiment 15, further comprising a controller unit (29) communicatively coupled (c1) to the strain sensor (8) of the transmission unit (1) for receiving the sensor signal, and wherein the controller unit (29) is communicatively coupled (c2) to a display device, e.g. a display device of the vehicle (25), which is configured for displaying operational information to a human operator for controlling power/torque provided by the vehicle (25) on the PTO drive shaft (26) in response to the sensor signal.

Embodiment 18. The PTO transmission system according to any one of embodiments 15-17, wherein the PTO transmission system (24) is a front PTO transmission system configured for being mounted on a front side (30) of the vehicle (25) and wherein the PTO drive shaft (26) is a front PTO drive shaft (26) of the vehicle (25).

The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.

Claims (18)

CONCLUSIONS A transmission unit (1) for power branch applications, comprising an input gear arrangement (2) connected to an input shaft member (3) of the transmission unit (1), an output gear arrangement (4) connected to an output shaft member ( 5) of the transmission unit (1), and an intermediate gear member (6) connecting the input and output shaft members (3, 5) by engagement with the input and output gear arrangement (2, 4), the transmission unit (1) further comprising an intermediate shaft part (7) extending through the intermediate gear part (6) and wherein the intermediate gear part (6) is journalled for rotation about the intermediate shaft part (7); and wherein the intermediate shaft part (7) comprises a strain sensor (8) configured to provide a sensor signal in accordance with lateral deflection (D) of the intermediate shaft part (7) when the transmission unit (1) is in use. The transmission unit according to claim 1, wherein the intermediate shaft part (7) comprises a first and a second shaft end (9, 10) arranged on opposite sides of the intermediate gear part (8) for supporting it in the transmission unit (1), the transmission unit (1) first shaft end (9) is at a first support distance (W1) from the idler gear part (6) and wherein the second shaft end (10) is at a second support distance (W2) from the idler gear part (6). The transmission unit according to claim 2, wherein the first support distance (W1) is equal to the second support distance (W2). The transmission unit according to any one of claims 1 to 3, wherein the intermediate shaft part (7) comprises one or more shaft recesses (11, 12, 13, 14) adjacent to the intermediate gear part (6) at one or more corresponding recess distances (x1, x2 x3, x4) of the intermediate gear member (6), and wherein the strain sensor (8) comprises one or more strain gauge members (8a, 8b, 8c, 8d) each arranged in a corresponding shaft recess of the one or more shaft recesses (11, 12, 13, 14). The transmission unit of claim 4, wherein the one or more corresponding recess distances (x1, x2, x2, x4) are equal. The transmission unit according to any one of claims 1-5, wherein the intermediate shaft part (7) comprises one or more circumferential grooves (15) adjacent to the intermediate gear part (6). The transmission unit according to any one of claims 1-6, further comprising one or more radial bearings (16, 17) mounted on the intermediate shaft part (7) and arranged within the intermediate gear part (6). The transmission unit of claim 7, wherein the intermediate shaft member (7) comprises an outer circumferential surface (18) configured for interference fit or transition fit with the one or more radial bearings (16, 17). The transmission unit according to any one of claims 1-8, wherein the input gear arrangement (2) comprises an input gear member (19) mounted on the input shaft member (3), and wherein the output gear arrangement (4) comprises an output gear member ( 20) mounted on the output shaft part (5), and wherein the idler gear part (6) is in direct engagement with the input and output gear part (19, 20). The transmission unit according to any one of claims 1-8, wherein the input gear arrangement (2) comprises an input gear member (19) mounted on the input shaft member (3), and wherein the output gear arrangement (4) comprises an output gear member ( 20) mounted on the output shaft part (5), and wherein the transmission unit (1) further comprises a further intermediate gear part (21) mounted on a further intermediate shaft part (22), wherein the output gear part (20) is in direct engagement is with the further idler gear part (21), and wherein the idler gear part (6) is in direct engagement with the input gear part (19) and the further idler gear part (21). The transmission unit according to any one of claims 1-8, wherein the input gear arrangement (2) comprises an input gear member (19) mounted on the input shaft member (3), and wherein the output gear arrangement (4) comprises an output gear member ( 20) mounted on the output shaft part (5), and wherein the transmission unit (1) further comprises one or more further intermediate gear parts (21) connecting the input and output shaft part (3, 5); and wherein the transmission unit (1) further comprises a further intermediate gear member (22) for each further intermediate gear member (21) and extending therethrough, wherein each intermediate gear member (21) is journalled for rotation about a corresponding further intermediate gear member (22). The transmission unit according to any one of claims 1-11, wherein the intermediate gear part (6) is a straight cut gear part. 40 The transmission unit according to any one of claims 1-12, wherein the output gear arrangement (4) comprises a clutch member (23) configured for coupling and uncoupling the output shaft member (5) from the input shaft member (3). The transmission unit according to any one of claims 1-13, wherein the sensor signal provided by the strain sensor (8) is a linear sensor signal in accordance with the lateral deflection {(D) of the intermediate shaft part (7) when the transmission unit (1 ) is in use. A PTO, power take-off, transmission system (24) comprising the transmission unit (1) according to any one of claims 1-14, wherein the PTO transmission system (24) is configured for mounting on a vehicle (25), wherein the input shaft part (3) of the transmission unit (1) is configured for connection to a PTO driving shaft (26) of the vehicle (25) and wherein the output shaft part (5) of the transmission unit (1) is configured for connection to a PTO driven shaft (27) of an implement (28). The PTO transmission system according to claim 15, further comprising a control unit (29) communicatively coupled (c1} to the strain sensor (8) of the transmission unit (1) for receiving the sensor signal, and wherein the control unit (29) is communicatively coupled (c2) is with the vehicle (25) for controlling power/torque delivered by the vehicle (25) on the PTO driving shaft (26) in response to the sensor signal. The PTO transmission system according to claim 15, further comprising a control unit (29) communicatively coupled (c1}) to the strain sensor (8) of the transmission unit (1) for receiving the sensor signal, and wherein the control unit (29) is communicatively coupled (c2) to a display device configured to display operational information to a human operator for controlling power/torque delivered by the vehicle (25) on the PTO driving shaft (26) in response to the sensor signal . The PTO transmission system according to any one of claims 15-17, wherein the PTO transmission system (24) is a front PTO transmission system (24) configured for mounting on a front (30) of the vehicle (25), and wherein the PTO driving shaft (26) is a front PTO driving shaft (26) of the vehicle (25). 40