WO2018107282A1

WO2018107282A1 - Pto drive provided with a cvt and control method therefor

Info

Publication number: WO2018107282A1
Application number: PCT/CA2017/051502
Authority: WO
Inventors: Daniel Girard; Jeremy SHIFLETT; Michel-xavier DUMAIS; Marc Lupien
Original assignee: Transmission Cvtcorp Inc.
Priority date: 2016-12-15
Filing date: 2017-12-12
Publication date: 2018-06-21

Abstract

A PTO drive provided with a CVT and control method therefor, wherein the CVT is so controlled as to decrease the power supplied to the controlled implement should an actual engine power be above a threshold is described herein.

Description

TITLE

PTO drive provided with a CVT and control method therefor

FIELD

[0001] The present disclosure generally relates to Continuously

Variable Transmissions (CVTs). More specifically, the present disclosure is concerned with the control of a PTO drive provided with a CVT.

BACKGROUND

[0002] CVTs are well known transmission mechanisms that can change trough an infinite number of gear ratios between upper and lower limits. Such transmissions are often used when transmission ratios have to be finely adjusted.

[0003] The present disclosure generally relates to a PTO drive transmission in an agricultural or industrial vehicle, i.e. a work vehicle, for transmitting power from a prime mover, generally in the form of an Internal Combustion Engine (hereinafter "ICE") to a PTO shaft driving an implement. The ICE also transfers power to ground traction wheels of the work vehicle via a main or traction drive transmission.

[0004] Present day work vehicles also generally comprise an ICE that can be electronically controlled and that may supply operational data to a controller, in an effort to provide optimum performance and fuel efficiency.

[0005] Therefore, PTO drive systems for work vehicles for transmitting power to a PTO shaft driving an implement or variable transmissions between the PTO shaft and drive means on the implement itself have been designed in an effort to allow the rotational speed of such implements to be controlled independently from the speed of the ground traction wheels of the vehicle or the speed of rotation of the ICE itself.

BRIEF DESCRIPTION OF THE DRAWINGS [0006] In the appended drawings:

[0007] Figure 1 is a schematic view of a drive train including a PTO drive provided with a CVT according to a first illustrative embodiment;

[0008] Figure 2 is a flowchart of a method according to an illustrative embodiment; and

[0009] Figure 3 is a schematic view of a drive train including a PTO drive provided with a CVT according to a second illustrative embodiment.

DETAILED DESCRIPTION

[0010] An object is generally to provide a PTO drive including a CVT that is so controlled as to take into account the actual engine power of the prime mover.

[0011] According to an illustrative embodiment, there is provided a

PTO drive connectable to an output shaft of a prime mover, the PTO drive comprising a CVT having an input connectable to the output shaft of the prime mover and an output connectable to a controlled implement; the CVT having a continuously variable ratio that is so controlled as to decrease the power supplied to the controlled implement by the output of the CVT should an actual engine power of the prime mover be above a threshold. [0012] According to another aspect, there is provided a PTO drive connectable to an output shaft of a prime mover, the PTO drive comprising: a CVT having an input shaft connectable to the output shaft of the prime mover, and an output connectable to a controlled implement; a controller so configured as to determine an actual engine power of the prime mover; the controller being connected to the CVT so as to control a continuously variable ratio thereof; wherein the continuously variable ratio of the CVT is so controlled by the controller as to decrease the power supplied to the controlled implement by the output shaft of the CVT should the controller determine that the actual engine power is above a threshold.

[0013] According to yet another aspect, there is provided a method for controlling a PTO drive having an input connected to an output shaft of a prime mover, the PTO drive including a CVT having a variable ratio and an output to which a controlled implement may be connected and a controller, the method comprising: obtaining an actual engine power value of the prime mover; comparing the obtained actual engine power value with a threshold; decreasing the ratio of the CVT should the obtained actual engine power value be greater than the threshold.

[0014] The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one", but it is also consistent with the meaning of "one or more", "at least one", and "one or more than one". Similarly, the word "another" may mean at least a second or more.

[0015] As used in this specification and claim(s), the words

"comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0016] The term "about" is used to indicate that a value includes an inherent variation of error for the device or the method being employed to determine the value.

[0017] It is to be noted that the expression "prime mover" is to be construed herein and in the appended claims as an internal combustion engine a turbine engine, or any other mechanical power production element or assembly.

[0018] It is to be noted that while the expression "CVT", standing for

Continuously Variable Transmission is to be construed, herein and in the appended claims as any type of Continuously variable transmission including, amongst others dual-cavity full toroidal CVT, half-toroidal CVT; single cavity toroidal CVT, Variable-diameter pulley CVT, Magnetic CVT, Ratcheting CVT, hydrostatic CVT, Cone CVT and planetary CVT. It is also to be noted that the term "CVT" is also to be construed, herein and in the appended claims, as a CVT provided with further elements allowing it to operate as an IVT, standing for Infinitely Variable Transmission, a subset of CVT designs in which the range of ratios of output shaft speed to input shaft speed includes a zero ratio.

[0019] It is to be noted that the expression "overdrive" when used herein in the context of a CVT, is to be construed herein and in the appended claims as a condition where the CVT ratio is such that the CVT output speed is higher than the CVT input speed. [0020] It is to be noted that the expression "underdrive" when used herein in the context of a CVT, is to be construed herein and in the appended claims as a condition where the CVT ratio is such that the CVT output speed is lower than the CVT input speed.

[0021] It is to be noted that the term "drivetrain", used herein and in the appended claims, are to be construed as the intervening mechanism by which power is transmitted from a prime mover to a final drive as well as this mechanism plus the prime mover.

[0022] The expressions "connected" and "coupled" are interchangeable and should be construed herein and in the appended claims broadly so as to include any cooperative or passive association between mechanical parts or components. For example, such parts may be assembled together by direct coupling or connection, or indirectly coupled or connected using further parts in between. The coupling and connection can also be remote, using for example a magnetic field or else.

[0023] The expression "input", without reference to a specific component such as a shaft, should be construed herein and in the appended claims, as including any movable part of an object, an assembly, a system or a mechanism that is used to receive a mechanical work from same or from another assembly, system or mechanism. Similarly, the expression "output" should be construed as including a similar part that is used to transfer a mechanical work.

[0024] The expression "gear ratio" should be construed herein and in the appended claims broadly as meaning the ratio between the speed of rotation at the input of a machine, system or assembly to that of the output thereof. [0025] Other objects, advantages and features of the PTO drive provided with a CVT and control method therefor will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings.

[0026] Generally stated, the illustrative embodiments describe a

PTO drive provided with a CVT and a method for controlling such a PTO drive where the actual engine power of the prime mover is taken into account to limit the power supplied to the controlled implement should the actual engine power reach a threshold. Accordingly, when this is the case, the portion of the actual engine power supplied to the controlled implement is decreased, which increases the power available for vehicle traction via the ground traction wheels and decreases the likelihood of the prime mover stalling.

[0027] In a first illustrative embodiment of a work vehicle drivetrain

10 as schematically illustrated in Figure 1 , a prime mover, in the form of an internal combustion engine (ICE) 12, has an output shaft connected to the input of a drive transmission 14. The output of the drive transmission 14 is directly or indirectly connected to the ground traction wheels 1 6. Of course, one skilled in the art will understand that other mechanical elements, such as for example, a differential transmission (not shown), can be interposed between the transmission 14 and the ground traction wheels 16.

[0028] The drivetrain 10 also includes a PTO drive 17 including a

CVT 20. More specifically, an input shaft 18 of the CVT 20 is connected to the output shaft of the ICE 12 via a clutch 22. The output shaft 24 of the CVT defining the PTO drive output shaft is connectable to a controlled implement 26. [0029] A controller 28 is at least connected to the ICE 12, the CVT

20 and optionally to the controlled implement 26 so as to control the overall operations thereof.

[0030] A simple conventional method of operation of a drivetrain such as 1 0 including a PTO drive is to control the CVT 20 so that the controlled implement 26 receives a generally constant rotational input speed, according to its needs, notwithstanding the actual speed of the output shaft of the prime mover 12. In other words, the CVT 20 compensates for the variation of output speed of the prime mover 12. This is possible since the controller 28 receives rotation speed data from the prime mover 12 and can control the CVT 20 accordingly.

[0031] Since the controller 28 may also receive the actual engine power developed by the prime mover 12, generally in the form of a percentage of the maximal engine power, the controller 28 knows when the prime mover 1 2 is close to reach its limits and risks stalling.

[0032] Since the actual engine power developed is the sum of the power required for the traction of the vehicle and the power supplied to the controlled implement, a control method according to an illustrative embodiment generally consists in controlling the CVT 20 so that a) the controlled implement 26 receives a rotational speed according to its needs, notwithstanding the actual rotational speed of the shaft of the prime mover 12, when the actual engine power is below a threshold; and b) the power supplied to the controlled implement 26 is decreased when the actual engine power reaches or exceeds the threshold. To decrease the power supplied to the controlled implement 26, the controller 28 changes the ratio of the CVT 20 so that the speed of its output shaft decreases. This decrease in the power supplied to the controlled implement 26, in turn, lowers the actual engine power below the threshold and therefore prevents the prime mover 12 from stalling.

[0033] One skilled in the art will understand that decreasing the speed of the controlled implement is not ideal, but it prevents the prime mover from stalling while allowing a limited operation of the controlled implement.

[0034] Figure 2 of the appended drawings is a flowchart of a control method 100 according to an illustrative embodiment.

[0035] In a first step 102, the controller obtains the actual engine power from the prime mover.

[0036] As will be apparent to one skilled in the art, obtaining the actual engine power of the prime mover as mentioned in step 102 is simple since the prime mover 12 is in communication with the controller 28 as can be seen in Figure 1 . Without limitations, a conventional CAN bus (Controller Area Network) can be used to interconnect the various elements of the drivetrain 10.

[0037] Step 104 consists in the comparison of the actual engine power with a threshold. It has been found that it is interesting to use an average of the actual engine power in the comparison. Indeed, if the instantaneous value of the actual engine power is used in this comparison, short spikes of high power values can cause the power supplied to the controlled implement to be decreased without adequate reason. Many averaging techniques can be used including, for example, moving average, harmonic average and Infinite Impulse Response (MR) filtered average. [0038] If the average actual engine power is not higher than a threshold, nothing happens and the method returns to step 1 02.

[0039] However, if the actual engine power is higher than the threshold, step 106 is performed and the CVT ratio is decreased. The method is then returned to step 102. As an example, the level of decrease of the CVT ratio in step 1 06 may be determined by the controller 28 as a function of the actual engine power value.

[0040] Of course, one skilled in the art will be in a position to modify the above control method. For example, in step 106, the CVT ratio could be brought to the maximum underdrive to minimize the power supplied to the controlled implement and gradually increased until the actual engine power is close to the threshold.

[0041] Another modification would be to have the controller 28 also control the clutch 22 and to disconnect the clutch should the maximal underdrive fail to bring the actual engine power of the prime mover below the threshold.

[0042] One skilled in the art will understand that the clutch 22 could be positioned downstream from the CVT 20. Also, fixed ratio gearing (not shown) could be provided upstream or downstream from the CVT 20 depending on the ratio range of the CVT, the speed range of the prime mover 12 and the desired speed range at the controlled implement 26.

[0043] One skilled in the art will also understand that a supplemental clutch (not shown) could be provided between the CVT 20 and the controlled implement 26 so that the clutch 22 may be engaged at start up of the drivetrain 10 and, subsequently, this supplemental clutch may be actuated so as to control the implement without disengaging the CVT 20 from the prime mover 12.

[0044] Without limitation, it has been found that an actual engine power threshold of 85% of the maximal engine power is an adequate value for the threshold of the method 1 00.

[0045] Turning now briefly to Figure 3 of the appended drawings, a second illustrative embodiment of a work vehicle drivetrain 200 will be described. Since the drivetrain 200 is very similar to the drivetrain 10 of Figure 1 , therefore, for concision purpose, only the differences will be described hereinbelow.

[0046] Generally stated, the main difference between the drivetrains

200 and 10 is the lack of direct interconnection between the prime mover 21 2 and the controller 228. This configuration may be used, for example, when the prime mover used is not provided with a CAN bus or other communication capabilities.

[0047] Accordingly, a rotation speed sensor 230 is associated with the output shaft of the prime mover 212 and supplies speed data to the controller 228. The controller may thus monitor the speed of the output shaft of the prime mover 212 and determine when a decrease in speed is due to an actual engine power that is about to reach or has already reached its limit. In other words, the controller uses the instantaneous rotational speed and the speed history of the output shaft of the prime mover 212 to determine if the actual engine power approaches its limits. When this is the case, the controller 228 may take actions on the CVT ratio to decrease the actual engine power as discussed hereinabove. One skilled in the art will understand that the speed sensor 230 could be positioned so as to monitor the speed of the input shaft of the CVT 20 or could even be integrated therewith. Since the input shaft of the CVT is connected to the output shaft of the prime mover via a clutch, the speed sensor 230 may be viewed as being associated with the output shaft of the prime mover even in this case.

[0048] It is to be noted that while the illustrative embodiments illustrated in the figures and described herein use actual power data supplied directly from the ICE or inferred by the rotational speed of the output shaft of the ICE, one skilled in the art will understand that other methods can also be used to determine the closeness of the ICE to stall. For example, a power sensor (not shown) could be associated with the prime mover 212 to measure the power supplied thereby and supply this data to the controller.

[0049] It is to be noted that other data can be supplied to the controller in order for the controller to determine if a power decrease of the PTO drive is in order. For example, a GPS (not shown) can supply terrain slope data to the controller so as to help the controller determine the duration required to go up a hill and therefore determine is the maximal allowable power on the prime mover 12 is likely to be reached and control the CVT ratio accordingly.

[0050] Similarly, data coming from accelerometers and/or tilt or slope sensors and/or other types of terrain sensors (all not shown) can be supplied to the controller to help in the control the CVT ratio.

[0051] One skilled in the art will understand that the controllers 28 or

228 may be part of a main controller (not shown) of the drivetrain 10 used, amongst others, to control the prime mover and the transmission 14. [0052] One skilled in the art will also understand that the main transmission 14 of the drivetrain 10 can also be a CVT.

[0053] It is believed that one skilled in the art of work vehicles will understand what controlled implement are and they therefore will not be described in great details herein. As non-limiting examples, feed mixers, pumps, electrical generators, rotary cutters, mowers, snow blowers and shredders are examples of controlled implements that could benefit from the above-described PTO drive.

[0054] It is to be understood that the PTO drive provided with a CVT and control method therefor is not limited in its application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The PTO drive provided with a CVT and control method therefor is capable of other embodiments and of being practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation. Hence, although the PTO drive provided with a CVT and control method therefor has been described hereinabove by way of illustrative embodiments thereof, it can be modified, without departing from the spirit, scope and nature thereof.

[0055] The following numbered clauses are offered as further description:

[0056] 1 . A PTO drive connectable to an output shaft of a prime mover, the PTO drive comprising a CVT having an input connectable to the output shaft of the prime mover and an output connectable to a controlled implement; the CVT having a continuously variable ratio that is so controlled as to decrease the power supplied to the controlled implement by the output of the CVT should an actual engine power of the prime mover be above a threshold. [0057] 2. A PTO drive as recited in clause 1 , wherein the input of the CVT is connected to the output shaft of the prime mover via a clutch.

[0058] 3. A PTO drive as recited in any of the preceding clauses, further comprising a controller so connected to the CVT as to control the continuously variable ratio thereof.

[0059] 4. A PTO drive as recited in clause 3, wherein the controller is so configured as to determine the actual engine power of the prime mover.

[0060] 5. A PTO drive as recited in any of clauses 3 and 4, further comprising a speed sensor associated with the output shaft of the prime mover and supplying speed data to the controller, wherein the controller is so configured as to determine if the actual engine power is above the threshold from the speed data.

[0061] 6. A PTO drive as recited in any of clauses 3 and 4, wherein the controller is so connected to the prime mover as to receive the value of the actual engine power therefrom.

[0062] 7. A PTO drive as recited in any of the preceding clauses, wherein the actual engine power threshold is about 85% of a maximal actual engine power.

[0063] 8. A PTO drive connectable to an output shaft of a prime mover, the PTO drive comprising:

a CVT having an input shaft connectable to the output shaft of the prime mover, and an output connectable to a controlled implement; a controller so configured as to determine an actual engine power of the prime mover; the controller being connected to the CVT so as to control a continuously variable ratio thereof;

wherein the continuously variable ratio of the CVT is so controlled by the controller as to decrease the power supplied to the controlled implement by the output shaft of the CVT should the controller determine that the actual engine power is above a threshold.

[0064] 9. A PTO drive as recited in clause 8, wherein the controller is so connected to the prime mover as to receive actual power data directly from the prime mover.

[0065] 10. A PTO drive as recited in clause 8, further comprising a speed sensor associated with the output shaft of the prime mover and supplying speed data to the controller, wherein the controller determines the actual engine power of the prime mover from the speed data.

[0066] 1 1 . A PTO drive as recited in any of clauses 8 to 10, further comprising a clutch connected to the input shaft of the CVT, the clutch being connectable to the output shaft of the prime mover.

[0067] 12. A PTO drive as recited in any of clauses 8 to 1 1 , wherein the output of the CVT includes a clutch to which a control implement is connectable.

[0068] 13. A PTO drive as recited in any of clauses 8 to 12, wherein the actual engine power threshold is about 85% of a maximal actual engine power. [0069] 14. A PTO drive as recited in clause 8, further including a terrain sensor connected to the controller.

[0070] 15. A method for controlling a PTO drive having an input connected to an output shaft of a prime mover, the PTO drive including a CVT having a variable ratio and an output to which a controlled implement may be connected and a controller, the method comprising:

obtaining an actual engine power value of the prime mover; comparing the obtained actual engine power value with a threshold;

decreasing the ratio of the CVT should the obtained actual engine power value be greater than the threshold.

[0071] 16. A method as recited in clause 15, wherein the actual engine power value obtaining is done by a transmission of the actual engine power from the prime mover to the controller.

[0072] 17. A method as recited in clause 15, wherein the actual engine power value obtaining is done by a measurement of a rotation speed of the output shaft of the prime mover.

[0073] 18. A method as recited in any of clauses 1 5 to 1 7, wherein the actual engine power threshold is about 85% of a maximal actual engine power.

Claims

WHAT IS CLAIMED IS:

1. A PTO drive connectable to an output shaft of a prime mover, the PTO drive comprising a CVT having an input connectable to the output shaft of the prime mover and an output connectable to a controlled implement; the CVT having a continuously variable ratio that is so controlled as to decrease the power supplied to the controlled implement by the output of the CVT should an actual engine power of the prime mover be above a threshold.

2. A PTO drive as recited in claim 1 , wherein the input of the CVT is connected to the output shaft of the prime mover via a clutch.

3. A PTO drive as recited in claim 1 , further comprising a controller so connected to the CVT as to control the continuously variable ratio thereof.

4. A PTO drive as recited in claim 3, wherein the controller is so configured as to determine the actual engine power of the prime mover.

5. A PTO drive as recited in claim 4, further comprising a speed sensor associated with the output shaft of the prime mover and supplying speed data to the controller, wherein the controller is so configured as to determine if the actual engine power is above the threshold from the speed data.

6. A PTO drive as recited in claim 3, wherein the controller is so connected to the prime mover as to receive the value of the actual engine power therefrom.

7. A PTO drive as recited in claim 1 , wherein the actual engine power threshold is about 85% of a maximal actual engine power.

8. A PTO drive connectable to an output shaft of a prime mover, the PTO drive comprising:

a CVT having an input shaft connectable to the output shaft of the prime mover, and an output connectable to a controlled implement;

a controller so configured as to determine an actual engine power of the prime mover; the controller being connected to the CVT so as to control a continuously variable ratio thereof;

9. A PTO drive as recited in claim 8, wherein the controller is so connected to the prime mover as to receive actual power data directly from the prime mover.

10. A PTO drive as recited in claim 8, further comprising a speed sensor associated with the output shaft of the prime mover and supplying speed data to the controller, wherein the controller determines the actual engine power of the prime mover from the speed data.

11. A PTO drive as recited in claim 8 further comprising a clutch connected to the input shaft of the CVT, the clutch being connectable to the output shaft of the prime mover.

12. A PTO drive as recited in claim 8, wherein the output of the CVT includes a clutch to which a control implement is connectable.

13. A PTO drive as recited in claim 8, wherein the actual engine power threshold is about 85% of a maximal actual engine power.

14. A PTO drive as recited in claim 8 further including a terrain sensor connected to the controller.

15. A method for controlling a PTO drive having an input connected to an output shaft of a prime mover, the PTO drive including a CVT having a variable ratio and an output to which a controlled implement may be connected and a controller, the method comprising:

obtaining an actual engine power value of the prime mover; comparing the obtained actual engine power value with a threshold; decreasing the ratio of the CVT should the obtained actual engine power value be greater than the threshold.

16. A method as recited in claim 15, wherein the actual engine power value obtaining is done by a transmission of the actual engine power from the prime mover to the controller.

17. A method as recited in claim 15, wherein the actual engine power value obtaining is done by a measurement of a rotation speed of the output shaft of the prime mover.

18. A method as recited in claim 15, wherein the actual engine power threshold is about 85% of a maximal actual engine power.