Parking brake control arrangement for vehicles with independent parking brake and transmission controls and self-arresting drive

Abstract

A vehicle (1) has a self-arresting drive (10) that arrests the vehicle (1) in the absence of a power command (C40), a transmission control (50) for selecting forward (F), neutral (N) or reverse (R) drive, and a parking brake control (31), e.g. an electrical switch, that is operable independently of the transmission control (50) to apply and release the parking brake (21). A control system (60) selectively enables and disables operation in forward (F) and reverse (R) drive responsive to an indication (S70) from a parking brake sensor (70), so that the drive system (10) does not supply power when the parking brake (21) is engaged. The control system (60) is arranged to detect a special command pattern (C500) comprising repeated movement of the transmission control (50) from the neutral (N) to the forward (F) or reverse (R) position within a defined time period, and to release the parking brake (21) independently of the parking brake control (31) in case the special command pattern (C500) is detected.

Description

[0001] Description

[0002] PARKING BRAKE CONTROL ARRANGEMENT FOR VEHICLES WITH INDEPENDENT PARKING BRAKE AND TRANSMISSION CONTROLS

[0003] AND SELF-ARRESTING DRIVE

[0004] Technical Field

[0005] This disclosure relates to arrangements for controlling the operation of a parking brake in vehicles having mutually independent parking brake and transmission controls, and of the type where the drive system will bring the vehicle to a halt in case the accelerator command is removed.

[0006] Background

[0007] In this specification, a transmission control means a control that is operable by the user to selectively engage a forward or reverse drive condition, or a neutral drive condition in which the driving power is decoupled from the wheels or tracks so that the vehicle can remain stationary. A transmission control is often implemented in the form of a movable lever, and may be referred to alternatively as a gearshift.

[0008] A parking brake is a brake that is designed to be applied when the vehicle is stationary to hold the vehicle stationary. In many vehicles, the parking brake is applied by a powerful spring, which must be energised (typically, compressed) by an actuator to relieve the spring force from the brake element (e.g. a friction pad) so as to release the parking brake to allow the vehicle to move. In so-called electrohydraulic systems, the spring force is relieved by a hydraulically powered actuator controlled by an electrically operated hydraulic valve, typically a solenoid valve.

[0009] In some vehicles, the transmission control includes a "Park" position in addition to the forward, neutral and reverse positions, and the parking brake is engaged by moving the transmission control to the "Park" position, so that the parking brake control is an integral function of the transmission control. The present disclosure is not directed to this last mentioned group of vehicles, but rather to those vehicles in which the parking brake is applied or released instead by a parking brake control that is operable independently of the transmission control. This arrangement is often preferred to provide a clear separation between the different control functions of the vehicle. For example, the parking brake control may be an electrical switch that controls the operation of the solenoid valve.

[0010] In order to avoid undesirable operation of the drive system against the resistance of the engaged parking brake, a controller is arranged to disable the drive system so that the driver cannot engage forward or reverse drive while the parking brake is engaged.

[0011] In many vehicles, such as those having an automatic transmission with a conventional torque converter, the vehicle drive system will set the vehicle in motion as soon as the brakes are released and the transmission control is moved to the forward or reverse position, or will maintain the motion of the vehicle as long as those conditions persist, even when the driver is not commanding power through the accelerator control. In this specification, the accelerator control means the control that is used to command power from the prime mover. By operating the accelerator control (typically by pressing down the accelerator pedal) the driver can increase the power supplied via the transmission to the wheels or tracks of the vehicle and so increase its speed.

[0012] The present disclosure however is not directed to this last mentioned group of vehicles, but rather to vehicles of the type where, in the absence of any input to the accelerator control, the drive system will arrest the motion of the vehicle and so bring the vehicle to a halt if it is already moving, or, if the vehicle is stationary on an incline, will oppose motion of the vehicle and so hold it stationary unless the incline is so steep as to overcome the resistance of the drive system. In this specification, a drive system having this characteristic is referred to as a self-arresting drive.

[0013] Self-arresting drives are commonly found in work vehicles, which is to say, in vehicles having a bucket or other work tool mounted on the vehicle and operable to manipulate a load in the vicinity of the vehicle, such as, for example, compact wheel loaders.

[0014] For example, in one common arrangement, the drive system may include a so-called hydrostatic transmission in which a variable displacement hydraulic pump is driven by an internal combustion engine. The accelerator control will adjust the pump displacement which remains at a minimum value when no power is commanded by the driver, and so prevents hydraulic flow through the pump and so also through the hydraulic motors that drive the wheels or tracks, thus preventing them from turning. When the accelerator pedal is released, the pump returns to the zero volume configuration (e.g. by movement of the swashplate to its rest position) and so the movement of the vehicle is retarded by the hydraulic resistance of the pump until the vehicle comes to a halt.

[0015] In another common arrangement, the vehicle may be driven by one or more electric motors powered by an on-board battery, where the motors are configured to exert a holding torque as long as the accelerator control is not demanding power. When the accelerator control is released by the driver, the vehicle is retarded by the holding torque until it comes to rest.

[0016] In vehicles with self-arresting drives, it is common for the driver to bring the vehicle to a stop merely by progressively releasing the accelerator control so that the vehicle is retarded by the drive system. After the vehicle comes to a stop, the driver may choose to leave the transmission control in the forward or reverse position and may not actuate the parking brake, relying instead on the self-arresting drive to hold the vehicle stationary until the driver is ready to move away by operating the accelerator control to demand power again. This can be done, for example, while the vehicle is being loaded ready for its next trip.

[0017] In appropriate use situations, an experienced driver can operate such vehicles safely and efficiently in this way.

[0018] However, a self-arresting drive does not obviate the need for a parking brake, which provides a positive holding force to hold the vehicle stationary in case, for example, the force of gravity acting on the laden vehicle on a steep slope should overcome the resistance of the self-arresting drive, or in case the self-arresting drive should allow the vehicle to creep gradually downhill. The parking brake is designed to immobilise the vehicle against any movement, whether sudden or gradual, and so provides an important safety feature that the driver will use as appropriate, particularly in case the driver needs to leave the machine.

[0019] Work vehicles are often used in arduous environments in a repetitive work cycle, and so it is desirable to minimise as far as possible the number of control inputs that the driver has to make during the work cycle. In order to maximise availability of the vehicle, it is also desirable for the vehicle to remain safely operational in case a fault condition should develop.

[0020] US9421958B2 discloses an electrohydraulic parking brake controlled by a solenoid operated valve. The valve has two coils that can be operated by different systems of the vehicle to disengage the parking brake.

[0021] JP2005313820A discloses a wheel loader with a controller that applies the parking brake automatically, irrespective of the position of the parking brake switch, responsive to sensing that the transmission is in neutral and the machine has stopped. The parking brake is released again when the steering column is pulled back by the driver.

[0022] Summary of the Disclosure

[0023] In its various aspects the present disclosure provides a vehicle, and a corresponding method for controlling the parking brake in the vehicle, as defined in the independent claims. The dependent claims define optional features.

[0024] The vehicle is controllable by a user and includes a set of wheels or tracks for supporting the vehicle for motion over a surface, a drive system including at least one prime mover, and a transmission for supplying power from the at least one prime mover to drive the wheels or tracks in motion.

[0025] The drive system is selectively operable in a forward state, for driving the vehicle in motion in a forward direction; in a reverse state, for driving the vehicle in motion in a reverse direction; and in a neutral state, in which the transmission does not supply power from the at least one prime mover to drive the vehicle in motion.

[0026] The vehicle further includes a plurality of braking devices, each respective braking device having a braked state in which the respective braking device is arranged to arrest or prevent motion of the vehicle, and an unbraked state in which the respective braking device is arranged not to arrest or prevent motion of the vehicle.

[0027] A plurality of brake controls are operable by the user to selectively command the plurality of braking devices to transition between the braked and unbraked states.

[0028] An accelerator control is operable by the user to generate a power command to cause the at least one prime mover to supply power to drive the wheels or tracks in motion.

[0029] A transmission control is movable by the user between forward, neutral and reverse positions to selectively command the drive system to transition, respectively, to the forward, neutral, and reverse states.

[0030] The plurality of brakes include at least one parking brake which is arranged, in the braked state, to prevent motion of the vehicle when the vehicle is stationary.

[0031] The plurality of brake controls include a parking brake control which is operable by the user, independently of the transmission control, to selectively command the at least one parking brake to transition between the braked and unbraked states.

[0032] When all of the plurality of brakes are in the unbraked state and the drive system is in the forward or reverse state, the drive system is arranged to drive the vehicle in motion when the power command is generated, and to arrest or prevent motion of the vehicle when the power command is not generated; which is to say, the drive system is of the self-arresting type.

[0033] The vehicle further includes a control system operable to enable and disable operation of the drive system in the forward and reverse states, and at least one parking brake sensor in operative communication with the control system, and arranged to sense the braked and unbraked states of the at least one parking brake.

[0034] The control system is arranged, responsive to receiving, from the at least one parking brake sensor, an indication that the at least one parking brake is in the unbraked state, to enable operation of the drive system in the forward or reverse state when commanded by movement of the transmission control to the respective, forward or reverse position; and, responsive to receiving, from the at least one parking brake sensor, an indication that the at least one parking brake is in the braked state, to disable operation of the drive system in the forward or reverse state irrespective of the position of the transmission control.

[0035] The control system is further arranged to monitor movement of the transmission control, and to make a determination as to whether or not the transmission control has executed a special command pattern, the special command pattern being defined as movement of the transmission control for a multiple number of times within a defined length of time from the neutral position to a respective one of the forward and reverse positions; and, responsive to determining that the transmission control has executed the special command pattern, to command the at least one parking brake to transition from the braked state to the unbraked state, independently of the parking brake control.

[0036] Brief Description of the Drawings

[0037] Further features and advantages will be appreciated from the various illustrative embodiments that will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which:

[0038] Fig. 1 shows a vehicle in accordance with an embodiment of the disclosure.

[0039] Fig. 2 is a highly simplified system diagram of the vehicle of Fig. 1.

[0040] Fig. 3 is a flowchart illustrating a control sequence of the vehicle of Fig. 1. For simplicity, the diagram of Fig. 2 omits many practical details as will be evident to those skilled in the art, and should not be construed as implying any additional technical limitations beyond those described. In Fig. 2, hydraulic lines are shown as solid lines, and electrical signal lines are shown as broken lines.

[0041] Reference numerals and characters that appear in more than one of the drawings indicate the same or corresponding features in each of them.

[0042] Detailed Description

[0043] Fig. 1 shows a work vehicle 1 configured as a compact wheel loader with a work tool in the form of a bucket 4 mounted on the vehicle body and manipulable by hydraulic actuators 5 to handle a load of loose material. The vehicle 1 is mounted on a set of wheels 2 or tracks that support the vehicle 1 for motion over the ground surface G, and is controllable by the user from the vehicle cab 6 via user controls, some of which are shown in Fig. 2.

[0044] Referring also to Fig. 2, the drive system 10 of the vehicle includes at least one prime mover 11, and a transmission 12, 12' for supplying power from the at least one prime mover 11 to drive the wheels 2 or tracks in motion.

[0045] As illustrated, the transmission may include a primary transmission 12 that transforms the power input from the prime mover 11 and drives a secondary transmission 12' or final drive to the wheels 2 or tracks.

[0046] An accelerator control 40, e.g. a foot pedal, is operable by the user to generate a power command C40 to cause the at least one prime mover 11 to supply power to drive the wheels 2 or tracks in motion.

[0047] The drive system 10 is selectively operable in a forward F state, for driving the vehicle 1 in motion in a forward direction; a reverse R state, for driving the vehicle 1 in motion in a reverse direction; and a neutral N state, in which the transmission 12, 12' does not supply power from the at least one prime mover 11 to drive the vehicle 1 in motion. The F, N or R state of the drive system 10 may be determined by adjustment of the transmission 12, 12' and / or of the or each prime mover 11, depending on the configuration of the drive system as known in the art. For example, it could be defined by selectively configuring electric or hydraulic power flow paths, by selectively allowing and disallowing power flow, by selectively signalling different torque commands to an electric motor, by changing hydraulic pump capacity, by changing motor polarity or hydraulic flow direction, or by selectively engaging and disengaging different gears to define the direction of rotation of respective transmission shafts.

[0048] A transmission control 50 is movable by the user between forward F, neutral N and reverse R positions to selectively command the drive system 10 to transition, respectively, to the forward F, neutral N, and reverse R states. As illustrated, the transmission control 50 may be a lever that is movable in sequence from the forward F position through the neutral N position to the reverse R position in the conventional way.

[0049] The vehicle 1 has a plurality of braking devices 20, 21, each having a braked state in which the respective braking device 20, 21 is arranged to arrest or prevent motion of the vehicle 1, and an unbraked state in which the respective braking device 20, 21 is arranged not to arrest or prevent motion of the vehicle 1. A plurality of brake controls 30, 31 are operable by the user to selectively command the plurality of braking devices 20, 21 to transition between the braked and unbraked states.

[0050] The plurality of braking devices 20, 21 include at least one parking brake 21 which is arranged, in the braked state, to prevent motion of the vehicle 1 when the vehicle 1 is stationary. The parking brake is operable (and normally will be operated) when the vehicle 1 is stationary, so as to hold the vehicle 1 stationary, although it may also be arranged to be operable in case of emergency to bring the vehicle to a halt.

[0051] The plurality of brake controls 30, 31 include a parking brake control 31 that is operable by the user, independently of the transmission control 50, to selectively command the at least one parking brake 21 to transition between the braked and unbraked states. That is to say, the parking brake control 31 can be operated without simultaneously operating the transmission control 50.

[0052] As illustrated, the parking brake control 31 may be an electric switch, and may be mounted in the cab 6 of the vehicle. The parking brake control 31 may be mounted on a surface of the vehicle (e.g. on a dashboard or fascia of the cab 6) separate from the transmission control 50, although it could alternatively be mounted on a part of the transmission control 50, as long as it is operable independently of the transmission control 50.

[0053] The vehicle 1 further includes a control system 60, further discussed below, and at least one parking brake sensor 70 which is in operative communication with the control system 60 and arranged to sense the braked and unbraked states of the at least one parking brake 21.

[0054] As illustrated, the at least one parking brake 21 may include at least one parking brake element 22, at least one parking brake spring 23, at least one hydraulic actuator 24, and at least one electrically operable valve 25.

[0055] As illustrated, each wheel 2 or track may include a parking brake 21 and a service brake 20. So, for example, each parking brake 21 may include a respective parking brake element 22, parking brake spring 23, and hydraulic actuator 24, with the actuators 24 of all the parking brakes being controlled by one electrically operable valve 25 (or, if divided into multiple circuits, a plurality of electrically operable valves 25.)

[0056] The parking brake element 22 is arranged to selectively engage the respective movable part 3 (e.g. a brake disc or drum), which is coupled to the wheels 2 or tracks, to immobilise the at least one movable part 3. The parking brake spring 23 is arranged to urge the respective parking brake element 22 into contact with the respective movable part 3. The hydraulic actuator 24 is operable to selectively energise the respective parking brake spring 23 to disengage the parking brake element 22 from the respective movable part 3, thus releasing the parking brake. By de-energising the parking brake spring, the parking brake is applied to immobilise the brake disc or drum 3. The electrically operable valve 25 may be a solenoid actuated valve, either with or without pilot pressure, and is operable to selectively apply hydraulic pressure (e.g. from the accumulator 15) to the or each hydraulic actuator 24.

[0057] The at least one parking brake sensor 70 may include at least one pressure sensor, as illustrated, for sensing the hydraulic pressure applied to the at least one hydraulic actuator 24. Thus, when the sensor 70 detects the system hydraulic pressure in the line to the actuator 24, it generates the indication S70 that the parking brake is in the unbraked state; and, when the sensor 70 detects low pressure in the hydraulic line to the actuator 24 (e.g. when the line is connected to tank), it generates the indication S70 that the parking brake is in the braked state.

[0058] The valve 25 may be operable by an electric command signal C31 directly from the parking brake control 31, or alternatively, it may be operable indirectly, responsive to the command signal C31, by the control system 60, as further described below.

[0059] The or each parking brake 21 may be applied automatically when the driver leaves the machine, e.g. responsive to turning off the engine or other prime mover 11, or responsive to setting a conventional safety device (not shown) in the cab to a condition indicating that the driver is absent. Such safety devices may be implemented for example as a movable lever or steering column or a seat pressure sensor or any other sensor that detects the presence or position of the driver. Applying the parking brake 21 will prevent the drive system 10 from operating in the forward F or reverse R state, as further discussed below.

[0060] In addition to the parking brakes 21, the plurality of brakes may include, for example, service brakes 20 controlled by a service brake control 30, e.g. a brake pedal, to slow the vehicle when moving, and / or other conventional braking systems such as retarders. In the illustrated example, the service brakes 20 are operated by hydraulic pressure controlled by a service brake control valve 26 responsive to hydraulic pilot signals from the service brake pedal 30. Hydraulic pressure for operating the brakes 20, 21 and other vehicle functions may be supplied by a hydraulic service pump 14 powered by the prime mover 11, and stored in an accumulator 15. Of course, other arrangements are possible, and in any practical system there will be additional complexity not illustrated, such as multiple brake circuits and accumulators, return flow lines, and other details well known to those skilled in the art.

[0061] The drive system 10 is of the self-arresting type. That is to say, when all of the plurality of braking devices 20, 21 are in the unbraked state and the drive system 10 is in the forward F or reverse R state, the drive system 10 is arranged to drive the vehicle 1 in motion when the power command C40 is generated, and to arrest or prevent motion of the vehicle 1 when the power command C40 is not generated. Thus, by progressively removing his or her foot from the accelerator pedal 40, the driver may cause the vehicle 1 to slow down to a stop, even when moving downhill.

[0062] As illustrated, in one example of a self-arresting drive system, the primary transmission 12 may include a hydraulic pump 13 with a continuously variable displacement, wherein the accelerator control 40 is operable to vary the displacement of the hydraulic pump 13. The prime mover 11 that drives the hydraulic pump 13 may be an internal combustion engine, e.g. a diesel engine, or an electric motor driven by batteries mounted on the vehicle.

[0063] The hydraulic pump 13 may drive the secondary transmission 12' via a hydraulic motor 16 at a drive ratio that depends on the displacement of the pump 13, which in turn may be controlled by a swashplate of the pump 13. As the power demand defined by the power command C40 declines to zero, the swashplate moves progressively until the displacement of each piston of the pump 13 is also zero, at which point the motor 16 stops turning due to the hydraulic resistance of the pump 13 which no longer allows the hydraulic fluid to circulate through it.

[0064] The primary transmission 12 may incorporate such an arrangement in parallel with a mechanical power transfer arrangement, so as to optimise efficiency by transmitting power alternatively via the hydraulic system or via a mechanical system of shafts and gears, depending on the speed of the vehicle 1. Many other arrangements will be evident to those skilled in the art.

[0065] In another example of a self-arresting drive system, not shown, the at least one prime mover 11 may include at least one electric motor, wherein the or each motor is arranged to exert a holding torque to resist rotation when the power command C40 is not generated. In such arrangements the power command C40 may include a torque command that adjusts the operation of the motor as known in the art. The or each electric motor may be powered by batteries mounted on the vehicle.

[0066] The control system

[0067] The control system 60 may include a processor 61 and a nonvolatile memory 62 holding instructions executable on the processor 61 to cause the control system 60 to perform its various functions, including its special functions of enabling and disabling the drive system functions and controlling the parking brake in accordance with the novel method, as further discussed below. Thus, the special functions of the control system 60 may be implemented by software stored in the memory 62.

[0068] The control system may include further interface components, such as electrohydraulic valves and / or electrical relays, in operative communication with the other vehicle systems to execute the control system commands. Such arrangements are well known in the art and are not further discussed or illustrated.

[0069] The control system 60 may be arranged to perform other tasks in addition to its special functions. For example, it may be configured as an engine control module (ECM) or part thereof to control the engine or electric motor or other prime mover 11 and / or the transmission 12, 12'. Non-volatile memory 62 may further include stored data, e.g. in the form of a look-up table, that is used as an input by the processor 61 to perform the special or other functions, e.g. by comparing the stored data with sensor data from various systems of the vehicle 1. The control system 60 is operable to enable and disable operation of the drive system 10 in the forward F and reverse R states. That is to say, the control system 60 is operable to determine whether or not the drive system 10 can function in the forward F or reverse R states.

[0070] By way of example, this could be achieved by switches or hydraulic valves controlled by the control system 60 and arranged to influence the operation of the drive system 10, by controlling electrical or hydraulic pressure signals in the drive system 10.

[0071] Alternatively, as illustrated, it may be achieved by arranging for the control system 60 to receive command signals from the user controls, and to issue command signals to the various vehicle systems responsive to the command signals received from the user controls, and also responsive to the logic that implements the special functions, e.g. in the form of software instructions executed on the processor 61.

[0072] That is to say: as illustrated in Fig. 2, the control system 60 may be interposed functionally in-between respective ones of the user controls and respective ones of the vehicle systems, so that it functions as an input / output device whose special functions (e.g. running on processor 61) determine how the vehicle responds to user commands, depending on sensor input, at least from the parking brake sensor 70.

[0073] In this way the control system 60 may be arranged to enable and disable operation of the drive system 10 in the forward F and reverse R states, by selecting whether or not to send command signals to the drive system 10, or which command signals to send to the drive system 10, responsive to user commands.

[0074] For example: as illustrated in Fig. 2, the control system 60 may be arranged to receive transmission command signals C50 from the transmission control 50, and to selectively command (i.e. cause) the drive system 10 (by generating and sending to the drive system 10 corresponding command signals C61) to transition, respectively, to the forward, neutral, and reverse states, responsive to the transmission command signals C50. Alternatively or additionally, where the parking brake sensor 70 is arranged as a pressure sensor, as described above, the control system 60 may be arranged to receive parking brake command signals C31 from the parking brake control 31, and to generate electrical control signals C60 to operate the at least one electrically operable valve 25 responsive to the parking brake command signals C31.

[0075] Alternatively or additionally, the control system 60 may be arranged to receive power command signals C40 from the accelerator control 40, and to generate and send to the drive system 10 the power command C62 responsive to the power command signals C40.

[0076] The control system: special functions: enabling and disabling the F and R transmission states

[0077] The control system 60 is arranged, responsive to receiving, from the at least one parking brake sensor 70, an indication S70 that the at least one parking brake 21 is in the unbraked state, to enable operation of the drive system 10 in the forward F or reverse R state when commanded by movement of the transmission control 50 to the respective, forward F or reverse R position.

[0078] That is to say: when the drive system 10 is commanded to transition to F or R by the transmission control 50, it will transition to F or R if the control system 60 has caused or allowed it to do so, but it will not transition to F or R if the control system 60 has not caused or allowed it to do so.

[0079] In this context, "caused" will apply, for example, if the control system 60 is interposed to perform an input / output function between the transmission control 50 and the drive system 10, as illustrated in Fig. 2. In such arrangements, for example, the drive system 10 may transition to F or R responsive to an electrical control signal C61, which is generated and sent by the control system 60 responsive to the transmission command signal C50.

[0080] That is to say, "caused" will apply where the transmission control 50 and the control system 60 are arranged in a series functional relationship, so that the drive system 10 will only make the commanded transition responsive to the electrical control signal C61 from the control system 60.

[0081] "Allowed" will apply, for example, in an alternative arrangement (not illustrated) where the transmission control 50 sends the transmission command signal C50 directly to the drive system 10, but the F and R functions of the drive system may be disabled by a disabling command from the control system 60, and must be enabled by the control system 60 before the drive system 10 is able to respond to the transmission command signal C50 by transitioning to the F or R state.

[0082] That is to say, "allowed" will apply where the transmission control 50 and the control system 60 are arranged in a parallel functional relationship in the sense of a logical "AND" function, so that the drive system 10 can only make the commanded transition if that transition is commanded or allowed by both the transmission control 50 and the control system 60.

[0083] The control system 60 is further arranged, responsive to receiving, from the at least one parking brake sensor 70, an indication S70 that the at least one parking brake 21 is in the braked state, to disable operation of the drive system 10 in the forward F or reverse R state irrespective of the position of the transmission control 50.

[0084] That is to say: as long as the parking brake sensor 70 indicates that the parking brake 21 is in the braked state, the control system 60 will not cause or allow the drive system to operate in (or transition to) the forward F or reverse R state.

[0085] Again, in this context, "cause" and "allow" reflect the series or parallel functional relationship of the transmission control 50 and control system 60 as just discussed.

[0086] If arranged in a series functional relationship, the control system 60 can disable operation of the drive system in the F or R state, by not generating the electrical control signal C61 for the respective F or R transition responsive to the transmission command signal C50. If arranged in a parallel functional relationship, the control system 60 can disable operation of the drive system in the F or R state, by not enabling the drive system 10 to make the commanded transition in direct response to the transmission command signal C50.

[0087] The skilled person can implement either a series or parallel functional relationship to suit the configuration of the vehicle.

[0088] In either arrangement, the effect is that, when the driver moves the transmission control 50 to F or R, the transmission will not supply power to the wheels 2 or tracks unless the parking brake 21 is released. Thus, the prime mover 11 will not act in opposition to the parking brake 21. This avoids wear and overheating of the parking brake 21.

[0089] The control system: special functions: special command pattern C500

[0090] The special command pattern C500 is defined as movement of the transmission control 50 for a multiple number of times (which is to say, with a defined number of repetitions) within a defined length of time from the neutral position N to a respective one of the forward F and reverse R positions.

[0091] For example, the special command pattern C500 may be identified when the transmission control 50 moves from N to F to N to F (so three movements defining two repetitions, starting at N and ending at F), within a defined length of time Tmax. This would command the drive system 10 to transition to the forward F state.

[0092] Alternatively or additionally, the special command pattern C500 may be identified when the transmission control 50 moves from N to R to N to R (so three movements defining two repetitions, starting at N and ending at R), within a defined length of time Tmax. This would command the drive system 10 to transition to the reverse R state.

[0093] The special command pattern may be identified responsive only to the first mentioned pattern (repeatedly commanding the drive system to transition to the forward F state) and not responsive to the latter mentioned pattern (repeatedly commanding the drive system to transition to the reverse R state, which then does not affect the parking brake 21.)

[0094] Alternatively, the special command pattern may be identified responsive to each of those patterns, repeatedly commanding the drive system 10 to transition to the forward F and reverse R states, respectively (with each pattern then having the same effect on the parking brake 21.)

[0095] The required number of repetitions may be two repetitions (which is to say, a first movement from N to F or R followed by a second such movement, so two movements, i.e. said multiple number of times is two times) or more than two repetitions (which is to say, more than two such movements, so said multiple number of times is more than two times.)

[0096] The time period Tmax may be defined, for example, as not more than 2 seconds, or not more than 1 second.

[0097] The control system 60 is further arranged to implement the method by monitoring movement of the transmission control 50; making the determination as to whether or not the transmission control 50 has executed the special command pattern C500; and, responsive to determining that the transmission control 50 has executed the special command pattern C500, commanding (which is to say, causing) C60 the at least one parking brake 21 to transition from the braked state to the unbraked state, independently of the parking brake control 31.

[0098] The determination can be made, for example, by starting a timer when the first transmission command signal C50 indicating a transition from the N state to the F or R state is received, and re-setting the timer at the end of the time period Tmax. If the defined pattern of transmission command signals C50 (i.e. the define number of repetitions) is received before the timer is re-set, then the determination is made. If the defined pattern of transmission command signals C50 is not completed before the end the time period Tmax then the determination is not made.

[0099] For example: if the first transmission command signal C50 indicates a transition from the N state to the F state, followed by a second transmission command signal C50 indicating a transition back to the N state, followed by a third transmission command signal C50 indicating a transition back to the F state, before the end of the time period Tmax initiated by the first transmission command signal C50, then the determination is made.

[0100] As illustrated in Fig. 2, once the special command pattern C500 is identified, the control system 60 may cause the parking brake 21 to transition to the unbraked state by generating the electrical control signal C60 that operates the electrically operable valve 25. In this way the control system 60 is able to release the parking brake 21 independently of the parking brake control 31 - which is to say, without receiving any parking brake command signal C31 from the parking brake control 31.

[0101] In this way the driver may release the parking brake 21 by moving the transmission control 50 rapidly from N>F>N>F (so two repetitions, thus causing the drive system 10 to transition to the forward F state.)

[0102] Optionally, the driver may be able to release the parking brake 21 also by moving the transmission control 50 rapidly from N>R>N>R (so two repetitions, thus causing the drive system 10 to transition to the reverse R state.)

[0103] Example control sequence

[0104] Fig. 3 illustrates an example control sequence that may be executed by the processor 61 of the control system 60.

[0105] The sequence begins by monitoring M movement of the transmission control 50, by the control system 60.

[0106] Monitoring may simply mean that the control system 60 is ready to receive transmission command signals C50 which are generated only when the transmission control 50 changes position, or it may mean that the control system 60 repeatedly receives transmission command signals C50 indicating the position of the transmission control 50 even when it has not changed position.

[0107] At step SI the control system 60 receives a transmission command signal C50 commanding a transition to the forward F, neutral N or reverse R state. If the signal C50 commands a transition to the neutral N state then at step S5 the control system 60 generates the electrical control signal C61 that causes the drive system 10 to transition to the neutral N state. Alternatively, the control system 60 may not issue any signal if the drive system 10 is already in the neutral N state.

[0108] If the signal C50 commands a transition to the forward F or reverse R state, then at step S2 the control system 60 determines whether the parking brake 21 is in the braked state, based on the indication S70 from the parking brake sensor 70. (The determination at step S2 may be a software function or a hardware function, e.g. implemented by an electrical switch, depending on how the control functions are implemented.)

[0109] If at step S2 the determination is No (N), which is to say, the parking brake 21 is in the unbraked state, then at step S5 the control system 60 generates the electrical control signal C61 that causes the drive system 10 to transition to the respective, forward F or reverse R state as commanded by the transmission control 50.

[0110] If at step S2 the determination is Yes (Y), which is to say, the parking brake 21 is in the braked state, then at step S3 the control system 60 determines whether the special command pattern (SCP, C500) has been identified.

[0111] The identification of the special command pattern C500 may be implemented as a timed subroutine in parallel with the illustrated steps, e.g. by setting flags in volatile memory of the processor 61 that indicate each iteration (i.e. repetition or instance) of step SI. Thus, at step S3 it may be determined whether the transmission command signal C50 received at step SI is the final signal in the defined special command pattern C500 including a previous iteration or iterations of the illustrated routine (the or each previous iteration terminating at branch No (N) at step S3) within the defined time period Tmax.

[0112] If at step S3 the determination is No (N) then the routine returns to monitoring M the signals from the transmission control 50. Further signals within the time period Tmax may be logged in the subroutine. If at step S3 the determination is Yes (Y) then at step S4 the control system 60 generates the electrical control signal C60 to command (i.e. cause) the parking brake 21 to transition to the unbraked condition. (So, if the special command pattern consists of two repetitions or instances of the same movement of the transmission control 50 from N to F or from N to R, then the determination will be Yes (Y) in case the identified instance is the second recorded instance within the defined time period.)

[0113] Then, at step S5, the control system 60 generates the electrical control signal C61 that causes the drive system 10 to transition to the respective, forward F or reverse R state as commanded by the transmission control 50.

[0114] Industrial Applicability

[0115] The novel arrangement can be used to allow the user to continue to drive normally in case the parking brake control 31 should develop a fault, by using the transmission control 50 instead of the parking brake control 31 to release the parking brake. Thus, the vehicle is made more tolerant of component failure which is not uncommon in heavily used electromechanical components such as an electrical parking brake switch.

[0116] The driver may also use the transmission control 50 habitually to disengage the parking brake, which may be found more convenient that using the parking brake switch since it reduces the number of touch points between entering the cab and moving the vehicle.

[0117] Advantageously, the drive system 10 may be operable to drive the vehicle 1 in motion at not more than a maximum speed, wherein the maximum speed is the same irrespective of whether the at least one parking brake 21 has transitioned from the braked state to the unbraked state responsive to operation of the parking brake control 31 or responsive to the special command pattern C500. Thus, the vehicle 1 may be fully functional irrespective of how the driver chooses to operate the parking brake 21.

[0118] Since the special command pattern C500 is a well defined sequence of movements in a limited time period, the driver should always be aware of when that command pattern is executed, obviating the risk of unintentional release of the parking brake 21.

[0119] Moreover, releasing the parking brake by operation of the transmission control 50 does not give rise to a risk of inadvertent movement of the vehicle, as would be the case with more common drive systems that are not self-arresting. Since the drive system 10 is of the self-arresting type, once the transmission has transitioned to the forward F or reverse R state, the vehicle will only begin to move if the driver also issues a power command signal C40.

[0120] In summary, a vehicle has a self-arresting drive that arrests the vehicle in the absence of a power command, a transmission control for selecting forward F, neutral N or reverse R drive, and a parking brake control, e.g. an electrical switch, that is operable independently of the transmission control to apply and release the parking brake. A control system selectively enables and disables operation in forward F and reverse R drive responsive to an indication from a parking brake sensor, so that the drive system does not supply power when the parking brake is engaged. The control system is arranged to detect a special command pattern comprising repeated movement of the transmission control from the neutral N to the forward F or reverse R position within a defined time period, and to release the parking brake independently of the parking brake control in case the special command pattern is detected.

[0121] In alternative embodiments, the novel control arrangement may be applied to other vehicles, including road vehicles and work vehicles mounted on tracks or on wheels. The prime mover and transmission may be of any conventional type that exhibits a self-arresting behaviour as discussed above.

[0122] As illustrated, the prime mover 11 may produce power to drive all the wheels 2 or tracks, or alternatively, each of the wheels 2 or tracks may have an individual prime mover, such as an individual electric motor or hydraulic motor, in which case the transmission will include the mechanical elements that transmit torque from each prime mover to its respective wheel 2 or track.

[0123] Many further adaptations are possible within the scope of the claims. In the claims, reference numerals and characters are provided in parentheses, purely for ease of reference, and should not be construed as limiting features.

Claims

Claims1. A vehicle (1) controllable by a user and including: a set of wheels (2) or tracks for supporting the vehicle (1) for motion over a surface (G); a drive system (10), the drive system including at least one prime mover (11), and a transmission (12, 12') for supplying power from the at least one prime mover (11) to drive the wheels (2) or tracks in motion; the drive system (10) being selectively operable in: a forward (F) state, for driving the vehicle (1) in motion in a forward direction; a reverse (R) state, for driving the vehicle (1) in motion in a reverse direction; and a neutral (N) state, in which the transmission (12, 12') does not supply power from the at least one prime mover (11) to drive the vehicle (1) in motion; a plurality of braking devices (20, 21), each respective braking device (20, 21) of the plurality of braking devices having: a braked state in which the respective braking device (20, 21) is arranged to arrest or prevent motion of the vehicle (1); and an unbraked state in which the respective braking device (20, 21) is arranged not to arrest or prevent motion of the vehicle (1); a plurality of brake controls (30, 31) operable by the user to selectively command the plurality of braking devices (20, 21) to transition between the braked and unbraked states; an accelerator control (40) operable by the user to generate a power command (C40) to cause the at least one prime mover (11) to supply power to drive the wheels (2) or tracks in motion; a transmission control (50) movable by the user between forward (F), neutral (N) and reverse (R) positions to selectively command the drivesystem (10) to transition, respectively, to the forward (F), neutral (N), and reverse (R) states; the plurality of braking devices (20, 21) including at least one parking brake (21), the at least one parking brake (21) being arranged, in the braked state, to prevent motion of the vehicle (1) when the vehicle (1) is stationary; the plurality of brake controls (30, 31) including a parking brake control (31); the parking brake control (31) being operable by the user, independently of the transmission control (50), to selectively command the at least one parking brake (21) to transition between the braked and unbraked states; wherein, when all of the plurality of braking devices (20, 21) are in the unbraked state and the drive system (10) is in the forward (F) or reverse (R) state, the drive system (10) is arranged: to drive the vehicle (1) in motion when the power command (C40) is generated; and to arrest or prevent motion of the vehicle (1) when the power command (C40) is not generated; the vehicle further including: a control system (60) operable to enable and disable operation of the drive system (10) in the forward (F) and reverse (R) states; and at least one parking brake sensor (70) in operative communication with the control system (60); the at least one parking brake sensor (70) being arranged to sense the braked and unbraked states of the at least one parking brake (21); the control system (60) being arranged: responsive to receiving, from the at least one parking brake sensor (70), an indication (S70) that the at least one parking brake (21) is in the unbraked state, to enable operation of the drive system (10) in the forward (F) or reverse (R) state when commanded by movement of the transmission control (50) to the respective, forward (F) or reverse (R) position; and,responsive to receiving, from the at least one parking brake sensor (70), an indication (S70) that the at least one parking brake (21) is in the braked state, to disable operation of the drive system (10) in the forward (F) or reverse (R) state irrespective of the position of the transmission control (50); wherein the control system (60) is further arranged: to monitor (M) movement of the transmission control (50); and to make a determination as to whether or not the transmission control (50) has executed a special command pattern (C500), the special command pattern (C500) being defined as movement of the transmission control (50) for a multiple number of times within a defined length of time from the neutral (N) position to a respective one of the forward (F) and reverse (R) positions; and, responsive to determining that the transmission control (50) has executed the special command pattern (C500), to command (C60) the at least one parking brake (21) to transition from the braked state to the unbraked state, independently of the parking brake control (31).

2. A vehicle (1) according to claim 1, wherein the transmission (12, 12') includes a hydraulic pump (13) with a continuously variable displacement, and the accelerator control (40) is operable to vary the displacement of the hydraulic pump (13).

3. A vehicle (1) according to claim 1, wherein the at least one prime mover (11) includes at least one electric motor, the at least one electric motor being arranged to exert a holding torque to resist rotation when the power command (C40) is not generated.

4. A vehicle (1) according to claim 1, wherein the drive system (10) is operable to drive the vehicle (1) in motion at not more than a maximum speed, wherein the maximum speed is the same irrespective of whether the at least one parking brake (21) has transitioned from the braked state to theunbraked state responsive to operation of the parking brake control (31) or responsive to the special command pattern (C500).

5. A vehicle (1) according to claim 1, wherein the at least one parking brake (21) includes: at least one parking brake element (22) for selectively engaging a respective at least one movable part (3) coupled to the wheels (2) or tracks to immobilise the at least one movable part (3); at least one parking brake spring (23) for urging the at least one parking brake element (22) into contact with the respective at least one movable part (3); at least one hydraulic actuator (24) for selectively energising the at least one parking brake spring (23) to disengage the at least one parking brake element (22) from the respective at least one movable part (3); and at least one electrically operable valve (25) for selectively applying hydraulic pressure to the at least one hydraulic actuator (24); and the at least one parking brake sensor (70) includes at least one pressure sensor for sensing the hydraulic pressure applied to the at least one hydraulic actuator (24).

6. A vehicle (1) according to claim 5, wherein the control system (60) is further arranged: to receive parking brake command signals (C31) from the parking brake control (31), and to generate electrical control signals (C60) to operate the at least one electrically operable valve (25) responsive to the parking brake command signals (C31).

7. A vehicle (1) according to claim 1, wherein the control system (60) is further arranged:to receive transmission command signals (C50) from the transmission control (50), and to selectively command (C61) the drive system (10) to transition, respectively, to the forward (F), neutral (N), and reverse (R) states, responsive to the transmission command signals (C50).

8. A vehicle (1) according to claim 1, wherein the control system (60) is further arranged: to receive power command signals (C40) from the accelerator control (40), and to generate the power command (C62) responsive to the power command signals (C40).

9. A method for controlling a parking brake (21) in a vehicle (i); the vehicle (1) being controllable by a user and including: a set of wheels (2) or tracks for supporting the vehicle (1) for motion over a surface (G); a drive system (10), the drive system including at least one prime mover (11), and a transmission (12, 12') for supplying power from the at least one prime mover (11) to drive the wheels (2) or tracks in motion; the drive system (10) being selectively operable in: a forward (F) state, for driving the vehicle (1) in motion in a forward direction; a reverse (R) state, for driving the vehicle (1) in motion in a reverse direction; and a neutral (N) state, in which the transmission (12, 12') does not supply power from the at least one prime mover (11) to drive the vehicle (1) in motion;a plurality of braking devices (20, 21), each respective braking device (20, 21) of the plurality of braking devices having: a braked state in which the respective braking device (20, 21) is arranged to arrest or prevent motion of the vehicle (1); and an unbraked state in which the respective braking device (20, 21) is arranged not to arrest or prevent motion of the vehicle (1); a plurality of brake controls (30, 31) operable by the user to selectively command the plurality of braking devices (20, 21) to transition between the braked and unbraked states; an accelerator control (40) operable by the user to generate a power command (C40) to cause the at least one prime mover (11) to supply power to drive the wheels (2) or tracks in motion; a transmission control (50) movable by the user between forward (F), neutral (N) and reverse (R) positions to selectively command the drive system (10) to transition, respectively, to the forward (F), neutral (N), and reverse (R) states; the plurality of braking devices (20, 21) including at least one parking brake (21), the at least one parking brake (21) being arranged, in the braked state, to prevent motion of the vehicle (1) when the vehicle (1) is stationary; the plurality of brake controls (30, 31) including a parking brake control (31); the parking brake control (31) being operable by the user, independently of the transmission control (50), to selectively command the at least one parking brake (21) to transition between the braked and unbraked states; wherein, when all of the plurality of braking devices (20, 21) are in the unbraked state and the drive system (10) is in the forward or reverse state, the drive system (10) is arranged: to drive the vehicle (1) in motion when the power command (C40) is generated; andto arrest or prevent motion of the vehicle (1) when the power command (C40) is not generated; the vehicle further including: a control system (60) operable to enable and disable operation of the drive system (10) in the forward (F) and reverse (R) states; and at least one parking brake sensor (70) in operative communication with the control system (60); the at least one parking brake sensor (70) being arranged to sense the braked and unbraked states of the at least one parking brake (21); the control system (60) being arranged: responsive to receiving, from the at least one parking brake sensor (70), an indication (S70) that the at least one parking brake (21) is in the unbraked state, to enable operation of the drive system (10) in the forward (F) or reverse (R) state when commanded by movement of the transmission control (50) to the respective, forward (F) or reverse (R) position; and, responsive to receiving, from the at least one parking brake sensor (70), an indication (S70) that the at least one parking brake (21) is in the braked state, to disable operation of the drive system (10) in the forward (F) or reverse (R) state irrespective of the position of the transmission control (50); the method including: monitoring (M), by the control system (60), movement of the transmission control (50); and making, by the control system (60), a determination as to whether or not the transmission control (50) has executed a special command pattern (C500), the special command pattern (C500) being defined as movement of the transmission control (50) for a multiple number of times within a defined length of time from the neutral (N) position to a respective one of the forward (F) and reverse (R) positions; and, responsive to determining, by the control system (60), that the transmission control (50) has executed the special command pattern (C500), commanding (C60), by the control system (60), the at least one parking brake(21) to transition from the braked state to the unbraked state, independently of the parking brake control (31).

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