CLIMB ASSIST SYSTEM FOR NON- ABS VEHICLES FITTED WITH AUTOMATED MANUAL TRANSMISSION

FIELD OF INVENTION

The present invention relates to a climb assist system for a Non ABS vehicle fitted with Automated Manual Transmission (AMT) for avoiding rollback of the vehicle in an inclined road and enhancing drivability of the vehicle in hilly terrains. The invention also provides a method of preventing rollback of a vehicle.

BACKGROUND OF THE INVENTION

Many vehicles, including commercial vehicles are fitted with Automated Manual Transmission (AMT) system. An AMT has a shift system added to the basic manual transmission which enables automatic shifting when in Automatic mode and manual shifting when in manual mode. An AMT is an automobile transmission system that facilitates gear shifting by dispensing with the need to press a clutch pedal at the same time as changing gears. It uses electronic sensors, pneumatics, processors and actuators to execute gear shifts on the command of the driver or by a computer. A typical AMT comprises a dry clutch, a gearbox and an embedded dedicated control unit that uses the above-mentioned sensors, processors and actuators to actuate gear shifts on the driver's command. This removes the need for a clutch pedal while the driver is still able to decide when to change the gear. The clutch itself is actuated by electronics which can synchronize the timing and torque required to make quick, smooth gear shifts. The AMT system is designed to provide a better driving experience, especially in terrains where traffic congestion frequently causes stop-and-go traffic patterns.

In a vehicle, especially a commercial vehicle fitted with AMT, the driver needs to hold the vehicle with heavy payloads and has to drive in a gradient especially in hilly areas. In such circumstances the need for start-stop of the vehicle is inevitable. With two pedals, namely, the accelerator pedal and brake pedal being operated by the same leg, it becomes difficult for the driver to manoeuvre on gradients without rollback on restart. Only skilled drivers will be able to smoothly operate the heavily loaded vehicle in hilly terrains without causing accidents.

In order to accelerate the vehicle in a gradient or climbing a hill, the driver has to shift his foot from the brake pedal to the accelerator pedal. However, during this transition period, the vehicle tends to rollback while trying to move forward since the driveline does not become engaged instantly upon depression of the accelerator pedal simultaneously as the brakes are released.

The rollback of the vehicle is due to the combination of climbing in incline/gradient surface and the load/weight of the vehicle. Accidents may occur in the hilly terrains at the time of vehicle restart condition. Vehicle operation in hilly terrains causes high driver fatigue and creates fear for travelling on hilly terrains. Hence, a need exists in commercial vehicles for a climb assist system to assist the driver by aiding the vehicle to negotiate gradient during restart without any driver input.

Large extent of work has been carried over the years on development of climb assist systems for vehicles to overcome the above-mentioned causes of rolling back of vehicles. In the related arts, hill holder devices would comprise of multiple sensors such as clutch sensor, brake sensor, acceleration sensor, vehicle speed, gear sensor, engine speed sensor and incline sensor, for arriving at a logic to control the brake.

US 4,582,184 discloses a hill assist system which utilizes a linkage connection between clutch pedal and brake pedal to apply brakes when the clutch pedal is depressed on an incline. US 2010/0168974 discloses a hill assist system which utilizes an anti-lock braking system electronic control unit (ABS ECU) for giving electronic control commands for controlling the brake application and release. The hill assist system proposed by US 2010/0168974 is applicable for vehicles with ABS and therefore expensive. US 6,315,372 discloses a hill assist system which has an automatic control system to hold the vehicle during hill stop condition by triggering a time delay to retain the brake pressure to apply brakes. In the meantime, the driver can carry out the restart operation. This system can be used for automatic/manual transmission with automatic clutch only. Also, there is a preset time delay which widely varies based on driver and road traffic condition.

US 6,679,810 discloses a hill assist system which works based on the sensing of backward movement of the vehicle. The brakes get actuated once the backward speed exceeds the pre-determined set value. In this method, there is a requirement of additional vehicle backward motion sensor.

Co-pending Indian application 2008/CHE/2012 discloses a climb assisting system that prevents rollback of a vehicle at the time of restarting or moving of a vehicle on an incline. The system comprises a control unit which provides a control signal to operate a solenoid operated pneumatic valve to actuate parking brakes of the vehicle. The signal is sent whenever the clutch is disengaged, vehicle speed is zero and the service brakes are in the disengaged position. The solenoid valve is actuated as instructed by the control unit and operates the parking brake provided with the vehicle.

The above mentioned conventional systems do not provide adequate protection against the rollback of a heavy vehicle such as trucks fitted with AMT system. These existing systems require manual intervention by the driver to operate the hill assist system. Further, the integration of available automated hill assist system to automated manual transmission mandates ABS inputs. Moreover, these conventional systems are complex in nature and incur high cost for adaptation. Further, some of the above-mentioned systems will not be suitable for a vehicle fitted with an AMT system.

Therefore, it is desired to provide a simple and cost effective and completely automatic climb assist system that provides adequate protection against the roll back of the Non ABS vehicle fitted with an AMT system that is transitioning from a stationary position.

OBJECT OF THE INVENTION

The main object of the present invention is to provide a climb assisting system for a vehicle which uses automatic manual transmission.

Another objective of the present invention is to provide a climb assisting system that is completely automatic and does not take any driver input for actuation.

Another objective of the present invention is to provide a climb assisting system that utilizes the available equipment in the vehicle with minimum add on devices, which makes the system inexpensive and easy to adopt.

Another object of the present invention is to provide a method for assisting a vehicle driver to prevent rollback of a vehicle under gradient conditions.

Another object of the present invention is to provide a Hill assist system for a non ABS vehicle fitted with AMT.

SUMMARY OF THE INVENTION

The climb assist system according to this invention is automatically switched ON once the ignition key of the vehicle is turned on. Upon ensuring that the service brake and the parking brake is in the disengaged position, the system checks the logic provided in an AMT control unit that takes input from the accelerator sensor, clutch sensor, engine rpm sensor, gear box output shaft rpm sensor and gear input sensor. If the logic is determined to be TRUE then a signal is given to energize an electro pneumatic valve to actuate the brake chamber of the service brakes. Thus, with the help of the system the driver will be assisted to manoeuvre the vehicle to avoid vehicle roll back on a gradient surface without pressing the brake pedal during restart condition.

Alternately, if any of the service or parking brake is engaged or if the logic provided to the AMT control unit is FALSE, then the electro pneumatic valve is de-energized and the brake chamber actuation through the climb assist system is withdrawn.

The climb assist system according to this invention is fully automatic and does not take any driver input for actuation of the service brakes.

The signal from the parking brake and the service brake is sent to a pneumatic valve and the signal from the AMT control unit is sent to an electro pneumatic valve, preferably a solenoid valve. Only under the condition that the parking brake and the service brake are in the disengaged position and the condition of the AMT control unit is TRUE does the brake chambers of the service brake become actuated.

Accordingly, the invention provides a climb assist system for a vehicle fitted with Automated Manual Transmission comprising: means for sensing brake position of a service brake and a parking brake; a transmission control unit capable of receiving signals indicating an accelerator pedal position, gearbox output shaft rpm, and gearbox gear signal; wherein, when the service brake and the parking brakes are sensed to be in the disengaged position, the transmission control unit is capable of actuating an electro pneumatic valve when, at least the gear is in any position other than neutral, and the gearbox output shaft rpm and the accelerator pedal position are less than their respective threshold levels, thereby activating the service brake chamber pneumatically to prevent rollback of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings, wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for purpose of limiting the same,

Fig. 1 shows the logic flowchart involved in a climb assist system according to this invention;

Fig. 2 shows the schematic diagram of the climb assist system in accordance with an exemplary embodiment of the present invention;

Fig. 3 shows an electro-pneumatic circuit diagram of the climb assist system in accordance with an exemplary embodiment of the invention.

Detailed Description of the Invention

The invention will now be described with reference to figures 1 and 2. The climb assist system is an electro-pneumatic circuit that functions on a particular logic. The climb assist system is activated the instant an ignition key of the vehicle is turned on. Thus, the system is fully automated without the requirement of the driver intervention to enable the system.

The climb assist system checks for the condition of the service brake and the parking brake. Separate primary (service) brake and parking brake sensors (40, 50) are provided in the appropriate positions proximal to the primary brake and the parking brakes and the signals (42, 52) from these sensors are sent to an engine management system or to a CAN controller, which is connected to an actuator, preferably a pneumatic valve (60). The brake sensors (40, 50) may be in the form of a limit switch which is by default in off state "0" and at the initiation of brake engagement the state changes to "1". If the service brake and the parking brake are both in the disengaged position, the system then checks for the condition of the logic sent to an AMT control unit(20). The AMT control unit (20) receives signals from various sensors dedicated to transmit signals from an accelerator pedal (16), engine rpm (24), gearbox output shaft rpm (18), gear input (14) and clutch input (26).

Even if one of the service brake or the parking brake is engaged, the air supply from an air tank to the brake chambers (15) of the service brakes is cut off and the electro pneumatic valve (17) is de-energized.

Under the condition that both the service brake and the parking brake are disengaged, the climb assist system checks the condition of the logic sent to the AMT control unit (20), which is a transmission control unit (TCU). The AMT control unit obtains inputs from the accelerator pedal (16), the gearbox output shaft rpm (18), engine rpm (24), clutch position (26) and the gear input signal (14). A TRUE condition of the logic is said to be attained when the accelerator pedal positions and the gearbox output shaft rpm are less than their respective threshold values, the clutch is engaged and the gear is in any position other than neutral.

Merely as an example, the following AMT control unit input conditions may be said to meet the TRUE condition of the logic.

Accelerator pedal position: 0-5%
Gearbox output shaft rpm: < 50 rpm (i.e. < 1 revolution per second)
Clutch position: engaged
Gear signal: any gear position other than neutral

If the TRUE condition of the logic is attained then the AMT control unit (20) sends an electric signal to energize the electro pneumatic valve (17) which in turn activates the service brake chambers (15) with air supply from an air tank. Even if one of the AMT control unit input conditions is not fulfilled, then the electro pneumatic valve (17) is not actuated and the air supply to the brake chambers(15) is cut off.

During actual working of the vehicle the climb assist system will function as follows. In a gradient surface, in order to move the vehicle, the driver has to disengage the parking brake and shift his foot from the brake pedal to the accelerator pedal. At the instant the leg is lifted up from the brake pedal both the service and parking brakes are in disengaged condition. In this condition the accelerator pedal is not yet pressed or is only slightly pressed, and the gearbox output shaft rpm is less than a threshold value, and the gear is moved to a position other than the neutral position, thus engaging the clutch. Under the above mentioned conditions the vehicle is prevented from rolling back on the gradient surface by means of the climb assist system, which ensures prevention of roll back or movement of the vehicle in an unwarranted direction by sending an electric signal to energize the electro pneumatic valve, thereby activating the brake chamber with air supply from the air tank. With the help of this system, the driver will be assisted to manoeuvre the vehicle on a grade without pressing the brake pedal during restart condition.

The instant the AMT input conditions become FALSE the electric signal is discontinued and the air supply to the brake chambers is cut off thereby allowing the driver to take full control of the normal manoeuvring of the vehicle. The AMT input condition becomes FALSE the instant the driver presses the accelerator pedal such that the engine rpm and the gearbox shaft output rpm crosses their respective threshold values. Even if one of these factors is FALSE the AMT does not send the electric signal to the electro pneumatic valve.

Figure 3 shows the electro-pneumatic circuit diagram of the climb assist system in accordance with an exemplary embodiment of the invention. In a normal working condition, the air compressor (1) supplies pressurized air which is stored in rear air tank (3) and front air tank (5) of appropriate capacities, each after going through the drying and distributor unit (7). When the brake pedal is pressed, or when the hand control valve (9) is engaged, the dual brake valve (11) sends pressurized air through its respective outlet ports (6, 8) to the front brake chambers (13) and the rear brake chambers (15) through respective relay valves (10,12).

For a vehicle fitted with a climb assist system the working principle of the brake system is as follows. When a climb assist system is added, the following signals are checked by the Transmission Control unit (TCU) (20) when the vehicle starts rolling back on a gradient.

Accelerator pedal position (16): (Obtained from Engine ECU) Gearbox output shaft rpm(18): (sensor input from transmission) Gearbox Gear signal(14): any gear position other than neutral (sensor
input from transmission) In addition to these signals, clutch signal, engine available torque, engine rpm signals are obtained from the engine ECU for standard checks.

A TRUE condition of the logic is said to be attained when the accelerator pedal positions and the gearbox output shaft rpm are less than their respective threshold values, the clutch is engaged and the gear is in any position other than neutral. Once the TRUE condition of the logic is attained, an electric signal (22) will be sent from the TCU (20) to a solenoid valve (17), which, in turn, will engage the brakes pneumatically as indicated by line (19) in figure 3. The solenoid operated valve (17) will get input air from the tanks (3, 5) only if the pneumatic operated 3 port, 2 stage spring return valve logics are true.

The pneumatic operated valves will be activated if the brake pedal is not pressed and if the hand control valve is disengaged.

The climb assisting system according to the present invention can be achieved with minimal modification in the existing design of the vehicle, and can be constructed using simple components thus providing a cost effective system for the vehicle to aid the driver to climb in an incline or gradient path.

While the above paragraphs explain the various embodiments of the invention, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated in the appended claims.

WE CLAIM

1. A climb assist system for a vehicle fitted with Automated Manual Transmission (AMT) comprising:
means (40, 50) for sensing brake position of a service brake and a parking brake;

a transmission control unit (20) capable of receiving signals indicating at least an accelerator pedal position, gearbox output shaft rpm, and gearbox gear signal;

wherein, when the service brake and the parking brakes are sensed to be in the disengaged position, the transmission control unit (20) is capable of actuating an electro pneumatic valve (17) when at least the gear is in any position other than neutral, the gearbox output shaft rpm and the accelerator Iedal position are less than their respective threshold values, thereby pneumatically activating a service brake chamber to prevent rollback of the vehicle.

2. The climb assist system as claimed in claim 1, wherein said system is activated upon turning on the ignition key.

3. The climb assist system as claimed in claim 2, wherein said system is independent of any driver intervention for its function.

4. The climb assist system as claimed in claim 1, wherein the transmission control unit actuates the electro pneumatic valve (17) when the gearbox output shaft rpm is < 1 revolution per second, and the accelerator pedal is 0-5% depressed.

5. The climb assist system as claimed in claim 1, wherein further inputs, such as engine rpm, clutch position are fed to the transmission control unit (20).

6. The climb assist system as claimed in claim 1, wherein the transmission control unit (20) is configured to send an electric signal to energize the electro pneumatic valve (17) thereby activating the service brake chamber (15) with air supply from an air tank.

7. The climb assist system as claimed in claim 1, wherein said system is independent of ABS inputs.

8. A method of preventing rollback of a vehicle comprising the steps of: activating a climb assist system;

obtaining inputs regarding the brake position of service brakes and parking brakes;

obtaining signals indicating an accelerator pedal position, gearbox output shaft rpm, and gearbox gear signal;

wherein, when the service brake and the parking brakes are sensed to be in the disengaged position, the method comprises the step of actuating an electro pneumatic valve (17) when at least the gear is in any position other than neutral, the gearbox output shaft rpm and the accelerator pedal position are less than their respective threshold values, thereby activating the service brake chamber pneumatically to prevent rollback of the vehicle.

9. The method as claimed in claim 8, wherein said system is independent of ABS inputs.