Compression-Based Speed Limitation for a Driveline Including a Transmission

FIELD

[0001] The present disclosure generally relates to drivelines including a transmission. More specifically, the present disclosure is concerned with compression-based speed limitation for such a driveline.

BACKGROUND

[0002] Some off-road vehicles need to go downhill for long stretches of time. Examples of these vehicles include mining vehicles that have to go down in mines. These long stretches of downhill travel have a negative impact on the conventional brakes of these vehicles that may overheat, which generally decreases their lifespan.

[0003] One conventional method of mitigating the premature wear and decreased lifespan of such a vehicle braking system is to downshift the transmission of the vehicle and use the engine compression to decrease the downhill speed of the vehicle to therefore decrease the use of the brakes. This method is somewhat inefficient and relies on the driver to control the discrete transmission ratio. The inefficiency of this conventional method is that with conventional discrete transmission, the driver must engage the gear that does not provide too much engine compression, but it does not mean that this chosen gear provides enough compression, leading to the required use of the brakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] In the appended drawings:

[0005] Figure 1 is a block diagram of a driveline including a transmission according to a first illustrative embodiment; and

[0006] Figure 2 is a schematic view of a first embodiment of the driveline of Figure 1 , illustrating the secondary transmission arrangement;

[0007] Figure 3 is a schematic view of a second embodiment of the driveline of Figure 1 , illustrating an alternative secondary transmission arrangement;

[0008] Figure 4 is a schematic view of a third illustrative embodiment of the driveline of Figure 1 , illustrating a simple secondary transmission arrangement; and

[0009] Figure 5 is a block diagram of a driveline similar to the driveline of Figure 1 but including a downhill detector.

DETAILED DESCRIPTION

[0010] An object is generally to provide an improved driveline including using compression-based speed limiting. More specifically, according to an illustrative embodiment, there is provided a driveline including: a prime mover having an output shaft; a transmission having an input associated with the output shaft of the prime mover and an output; the transmission having multiple transmission ratios; a secondary transmission including first and second clutches; the secondary transmission having an input associated with the output of the transmission and an output connectable to a load; and a main controller associated with the prime mover, the transmission and the secondary transmission; the main controller being so configured as to detect over speeding of the output of the secondary transmission and to decrease the transmission ratio to increase the prime mover compression to thereby limit the speed of the output of the secondary transmission.

[0011] According to another aspect, there is provided a driveline provided between a prime mover having an output shaft and a load, the driveline comprising: a transmission having an input associated with the output shaft of the prime mover and an output; the transmission having multiple transmission ratios; a secondary transmission including first and second clutches; the secondary transmission having an input associated with the output of the transmission and an output associated with the load; and a main controller associated with the prime mover, the transmission and the secondary transmission; the main controller being so configured as to detect over speeding of the output of the secondary transmission and to decrease the transmission ratio to increase the prime mover compression to thereby limit the speed of the output of the secondary transmission.

[0012] 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.

[0013] 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.

[0014] The expression “connected” 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 connection, or indirectly connected using further parts therebetween. The connection can also be remote, using for example a magnetic field or else.

[0015] 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.

[0016] 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 (ICE) a turbine engine, or any other mechanical power production element or assembly. [0017] It is to be noted that the term “CVT”, standing for

Continuously Variable Transmission, is used herein to describe any type of CVT including, amongst others, a toroidal CVT, a dual-cavity full toroidal CVT, a half-toroidal CVT, a single cavity toroidal CVT, a hydrostatic CVT, a Variable diameter pulley CVT, a magnetic CVT, a ratcheting CVT and a cone CVT.

[0018] It is to be noted that the expression “overdrive” when used 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. The CVT ratio (of output speed to input speed) is therefore higher that one to one (1 :1).

[0019] It is also to be noted that the expressions “fixed disk”, when used herein and in the appended claims in the context of clutch technology, may be viewed as any element or group of elements constituting a clutch driving member. Similarly, the expressions “movable disk”, when used herein and in the appended claims in the context of clutch technology, may be viewed as any element or group of elements constituting a clutch driven member.

[0020] It is to be noted that the expression “underdrive” when used 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. The CVT ratio (of output speed to input speed) is therefore lower that one to one (1 :1).

[0021] It is to be noted that the term "driveline", used herein and in the appended claims, is to be construed as the intervening mechanism by which power is transmitted from a prime mover to a load, for example the wheels of a vehicle, as well as this mechanism plus the prime mover. [0022] It is to be noted that the expression “off-highway vehicle” is to be construed herein and in the appended claims as any type of vehicle that is designed specifically for use off-road, including, amongst others, construction vehicles and agricultural vehicles.

[0023] It is also to be noted that the term “over speeding” is to be construed herein and in the appended claims as a speed that is higher than a threshold that may be fixed or variable according to vehicle parameters, such as the position of the acceleration pedal, for example.

[0024] Other objects, advantages and features of the compressionbased speed limitation for a driveline including a transmission 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.

[0025] Figure 1 of the appended drawings illustrate a driveline 10 according to an illustrative embodiment comprising a prime mover 12, in the form of an ICE, a transmission in the form of a CVT 14 and a secondary transmission 16 including a clutch. The output of the secondary transmission 16 is connected to a load 20, for example the wheels of an off-road vehicle.

[0026] A first shaft 22 interconnects the output of the ICE 12 and the input of the CVT 14; the speed of the first shaft is measured via a first speed sensor 24. A second shaft 26 interconnects the output of the CVT 14 and the input of the secondary transmission 16; the speed of the second shaft 26 is measured via a second speed sensor 28. A third shaft 30 interconnects the output of the secondary transmission 16 and the load 20; the speed of the third shaft 30 is measured via a third speed sensor 32. [0027] Conventionally, the ICE 12 is associated with a user throttle control 36, for example an acceleration pedal (not shown). Instead of being directly connected to the throttle input of the ICE 12, the user throttle 36 is connected to a main controller 42 to supply throttle data thereto. The main controller 42 may therefore supply throttle data to the ICE 12, in its original form or in a clipped form, as will be discussed hereinbelow.

[0028] The driveline 10 includes a ratio controller 38 so configured as to set the ratio of the CVT 14 according to a ratio provided by the main controller 42 as will be described hereinbelow.

[0029] Optionally, the driveline 10 is provided with a clutch controller

44 is so configured as to take a usable torque value from the main controller 42 and to control the clutch of the secondary transmission 16 so as to slip when the torque attempting to pass through is greater than this usable torque. In other words, when the torque present between the input and output of the clutch of the secondary transmission 16 is greater than the usable torque, the clutch slips.

[0030] One skilled in the art will have no problem building such an optional clutch controller 44 adapted to the technology used in the clutch of the secondary transmission 16.

[0031] Should the optional clutch controller 44 be absent from the driveline, the controller 42 controls the clutch of the secondary transmission in a conventional manner.

[0032] The speed data from the first and second speed sensors 24 and 28 is supplied to the main controller 42 so that the controller 42 may determine the actual ratio of the CVT 14 in real time. Furthermore, the speed data of the second and third speed sensors 28 and 32 is supplied to a slip detector 46 that may determine if slippage of the clutch of the secondary transmission 16 occurs, in real time, and supply this data to the main controller 42.

[0033] As will be easily understood by one skilled in the art, the main controller 42 could integrate the ratio controller 38, the optional clutch controller 44 and/or the slip detector 46.

[0034] When a driveline such as 10 is installed in an off-road vehicle that often needs to go downhill for long stretches of time, the controller 42 can be so configured as to control the ratio of the CVT so as to optimize the compression of the prime mover 12 and therefore to minimize the use of the brakes (not shown).

[0035] More specifically, since the controller 42 receives throttle data from the acceleration pedal 36, the controller 42 knows the position of the pedal 36 in real time. Accordingly, a speed limitation based on the position of the acceleration pedal 36 can be implemented by the controller 42.

[0036] As a non-limiting example, the speed threshold can be 42 km/h when the pedal 36 is totally depressed, 20 km/h when the pedal 36 is not depressed and can vary linearly between these two extreme positions. One skilled in the art will understand that the controller 42, by receiving speed data relating to the output of the secondary transmission 16 from the speed sensor 32, and by knowing the characteristics of the vehicle, can determine the ground speed of the vehicle from the speed data from the speed sensor 32. [0037] The controller 42 has mainly two ways of preventing the speed to be greater than the threshold, i.e., preventing over speeding: it can clip the accelerator pedal signal supplied to the prime mover 12 and it can decrease the ratio of the transmission 14. Both of these ways are generally used sequentially. The signal is first clipped and, should the speed be still higher than the threshold, the transmission ratio is decreased. Of course, both the signal clipping and the decrease of the transmission ratio can be done simultaneously.

[0038] One skilled in the art is believed in a position to configure the controller 42 to adequately clip the accelerator pedal signal and, for concision purpose, this will not be described further.

[0039] In this illustrative embodiment, when the vehicle travels downhill and the acceleration pedal 36 is not depressed, the controller 42 attempts to prevent over speeding by limiting the speed of the output of the secondary transmission 16 to an equivalent of 20 km/h at the wheels of the vehicle by decreasing the ratio of the transmission 14 to thereby increase the compression of the prime mover 12.

[0040] Indeed, by controlling the CVT ratio towards the underdrive, the downhill movement of the vehicle tries to speed up the shaft 22 of the prime mover 12, which increases the compression of the prime mover, making it harder for the vehicle to speed up, therefore decreasing the possibility of the downhill speed limit to be overshot. The controller 42 may thus control the speed of the vehicle by finely controlling the ratio of the CVT 14 depending on the prime mover ground speed detected, for example via the speed sensor 32. [0041] Of course, as mentioned hereinabove, the controller 42 also clips or otherwise sets the signal sent to the throttle input of the prime mover so as to promote compression thereof, when required.

[0042] As will easily be understood by one skilled in the art, the various speed sensors shown, herein as discrete elements, could be integrated with other elements. As non-limiting examples, the speed sensor 24 could be integrated with the prime mover 12, the speed sensors 24 and 28 could be integrated in the transmission 14, and/or the speed sensor 32 could be integrated with the secondary transmission 16.

[0043] Turning now to Figure 2 of the appended drawings, a driveline 100 according to a second illustrative embodiment similar to the one shown in Figure 1 will be described. Figure 2 includes a first illustrative embodiment of a secondary transmission 116.

[0044] The secondary transmission 116 includes first and second clutches 102 and 104 having a common fixed disk 108 associated with the shaft 26 and separately actuatable movable disks 110 and 112 each provided with a respective speed sensor 32A and 32B, replacing the speed sensor 32 of Figure 1.

[0045] The movable disk 110 is associated with a low-speed forward gear set 114 fixedly connected to an output gear set 122, while the movable disk 112 is associated to both a high-speed forward gear set 117 and a reverse gear set 118 both connectable to the output gear set 122 via a dog clutch assembly 120. [0046] One skilled in the art will understand that when the clutch 102 is engaged, i.e. , when the movable disk 110 is brought in contact with the fixed disk 108, power passes through the low-speed forward gear set 114 to reach the output gear set 122 of the secondary transmission 116 and ultimately the load 20. On the other hand, when the clutch 104 is engaged, i.e., when the movable disk 112 is brought in contact with the fixed disk 108, power passes either through the high-speed forward gear set 117 or the reverse gear set 118 to reach the output gear set 122 and ultimately the load 20, depending on the position of the dog clutch 120.

[0047] It is to be noted that the speed sensors 32A and 32B are respectively provided to measure the rotating speed of the movable disks 110 and 112, or their respective shafts, and the speed data is sent to the controller 142. Accordingly, the controller 142 may determine the slippage of the clutches 102 and 104 since the rotational speed of the fixed disk is known from speed sensor 28.

[0048] Alternatively, a single speed sensor (not shown) could replace the two sensors 32A and 32B by being positioned at the output of the secondary transmission 116 and the controller 142 could determine the slippage condition since the position of the dog clutch assembly 120 and the ratio of the various gear sets are known.

[0049] It is to be noted that, in Figure 2, the main controller 142 integrates the ratio controller 38, the optional clutch controller 44 and the slip detector 46 described separately in Figure 1.

[0050] As mentioned hereinabove in connection to Figure 1 , a compression-based speed limitation may be done using the CVT 14. [0051] In some cases, for example when the downhill gradient is large or the weight of the vehicle is great, the compression of the prime mover 12 might not be enough to sufficiently slow down the vehicle so that the use of the conventional braking system is not required. In other words, in these cases, the energy dissipated by the compression of the prime mover 12 is not sufficient to compensate for the kinetic energy that must be dissipated to slow the vehicle to the desired speed.

[0052] When a secondary transmission such as 116 is used, it is possible to further use the clutches 102 and 104 to dissipate more energy to thereby further decrease the use of the conventional brakes.

[0053] More specifically, since only one of the clutches 102 and 104 is fully engaged at any one time, in this illustrated embodiment, the controller 142 is so configured as to monitor the compression level of the prime mover 12, and when the compression level gets close to a predetermined threshold, to partially engage the unused one of the clutches 102 and 104 to thereby dissipate some of the kinetic energy from the load and therefore at least partially compensate for the compression shortfall of the prime mover 12.

[0054] One skilled in the art is believed in position to configure the controller 142, according to the clutch technology used, to partially engage the other of the clutches 102 and 104 so that energy is dissipated by the friction of the partially engaged movable and fixed disks of the unused one of the two clutches.

[0055] It is to be noted that it is believed interesting to monitor the temperature of the partially engaged clutch so that it does not reach a temperature that would decrease the efficiency and/or the lifespan of the clutch. Sensors (not shown) can be used to monitor the temperature of the clutch or estimations of the rising temperature using the clutch slipping data can be configured in the controller 142. One skilled in the art is believed in a position to design an adequate temperature monitoring strategy.

[0056] One skilled in the art will understand that the use of the unused one of the clutch 102 and 104 can be momentary or continuous, i.e., that this other clutch can be used to slow down the vehicle until a desired speed is reached and then the compression of the prime mover is sufficient to maintain the desired speed or, should the compression of the prime mover be insufficient to maintain the desired limited speed, the other clutch can be used in a continuous manner.

[0057] Turning now to Figure 3 of the appended drawings, a schematic diagram of a driveline 200 similar to driveline 100 shown in Figure 2 will be described. The driveline 200 illustrates a second illustrative embodiment of a secondary transmission 216.

[0058] Since the driveline 200 is very similar to the driveline 100 described hereinabove, only the differences therebetween will be described, for concision purpose.

[0059] Generally stated, the main difference between driveline 200 and driveline 100 is the use of a third forward speed. Accordingly, the movable disk 110 is associated with a low-speed forward gear set 214 and a high-speed forward gear set 218 both connectable to the output gear set 222 via a first dog clutch assembly 220, while the movable disk 112 is associated to both a medium-speed forward gear set 224 and a reverse gear set 226 both connectable to the output gear set 222 via a second dog clutch assembly 228. [0060] One skilled in the art will understand that this addition of a third forward speed does not significantly impact the operation of the compression-based speed limiting features of the driveline since only one of the clutches 102 and 104 is fully engaged to the output of the secondary transmission 216 to supply torque to the load at any one time; the unused one of the clutches 102 and 104 may be so controlled by the controller 142 to dissipate energy as discussed hereinabove.

[0061] Turning now briefly to Figure 4 of the appended drawings, a schematic diagram of a driveline 300 similar to driveline 100 shown in Figure 2 will be described. The driveline 300 illustrates a third illustrative embodiment of a secondary transmission 316.

[0062] Since the driveline 300 is very similar to the driveline 100 described hereinabove, only the differences therebetween will be described, for concision purpose.

[0063] Generally stated, the main difference between driveline 300 and driveline 100 is that the secondary transmission 316 of the driveline 300 is a simple forward/re verse secondary transmission. Accordingly, the movable disk 110 is associated with a forward gear set 314 while the movable disk 112 is associated to a reverse gear set 336, both connected to the output gear set 322 defining the output of the secondary transmission 316.

[0064] One skilled in the art will understand that this modification to the secondary transmission does not significantly impact the operation of the compression-based speed limiting features of the driveline since only one of the clutches 102 and 104 is fully engaged to the output of the secondary transmission 316 to supply torque to the load at any one time; the unused one of the clutches 102 and 104 may be so controlled by the controller 142 to dissipate energy as discussed hereinabove.

[0065] While the clutches 102 and104 are shown herein as being packaged together, sharing a fixed disk, one skilled in the art will understand that these clutches could be separated.

[0066] One skilled in the art will understand that while the driveline

200 is shown with a third forward speed ratio, this third forward speed ratio could be replaced by a second reverse speed ratio.

[0067] One skilled in the art will understand that in the abovedescribed drivelines, when the driver changes the position of the acceleration pedal the controller adapts the speed limit threshold to the position of the acceleration pedal.

[0068] Furthermore, one skilled in the art will understand that should the driver of the vehicle decide to depress the acceleration pedal during downhill travel, the vehicle will accelerate.

[0069] In another illustrative embodiment shown in Figure 5, the driveline 400 further includes a downhill detector 402 that is connected to the controller 42.

[0070] The use of a downhill detector 402 makes it possible to totally ignore the position of the acceleration pedal 36 during downhill travel. Accordingly, the speed limit features could be identical to the speed limit features described hereinabove when the downhill detector 402 does not detect downhill travel and could be 20 km/h (for example) when downhill travel is detected.

[0071] In other words, when such a downhill detector 402 is used, the main controller enters in the speed limiting mode when the downhill detector detects downhill travel, without reference to the position of the acceleration pedal. It is interesting since it allows the downhill speed to be fixedly limited even though a careless or distracted driver may still depress the acceleration pedal while travelling downhill.

[0072] As non-limiting examples, altimeters, inclinometers, GPS and maps, manual selector, proximity beacons and/or extended brake-use detectors can be used as a downhill detector to determine if the vehicle travels downhill.

[0073] The driveline 400 also includes a conventional multispeed transmission 404 in place of the CVT 14. Accordingly, a suitable transmission controller 406 is provided. This transmission controller 406 receives instruction from the main controller 42.

[0074] One skilled in the art will understand that any multispeed transmission that can be controlled electronically can be used as the transmission 404. The efficiency of the system described herein to selectively promote adequate compression of the prime mover 12 generally increases with the number of transmission ratios available on the multispeed transmission.

[0075] Finally, one skilled in the art will understand that the various features of the different embodiments described hereinabove could be used on the other embodiments. As a non-limiting example, the use of a downhill detector such as 402 could be used on any of the other embodiments.

[0076] It is to be understood that the compression-based speed limitation for a driveline including a transmission is not limited in its application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The compression-based speed limitation for a driveline including a transmission 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 compression-based speed limitation for a driveline including a transmission has been described hereinabove by way of illustrative embodiments thereof, it can be modified, without departing from the spirit, scope, and nature thereof.