ELECTRONICALLY CONTROLLED BRAKE APPARATUS FOR TRACTORS

The present invention relates to an electronically controlled brake apparatus for tractors.

A major problem with tractors, and one also commonly encountered by ordinary motorists, is that, to prevent back-rolling of the tractor by force of gravity when braked uphill, the driver is forced to use the handbrake or adopt other awkward measures, such as accelerating slightly to compensate the backward pull induced by force of gravity.

The present invention is designed to provide a straightforward solution to the above problem, by means of an automatic uphill parking apparatus requiring no use of the handbrake or other awkward measures.

A non-limiting embodiment of the present invention will be described by way of example with reference to the attached drawing. Number 10 in the attached drawing indicates as a whole an electronically controlled brake apparatus, in particular for tractors, in accordance with the present invention .

Apparatus 10 comprises a compressor 11 for supplying compressed air to an air-processing substantially air-dehumidifying - unit 12.

The processed air is stored in two parallel tanks 13a, 13b, both connected pneumatically to a pedal

arrangement 14 which provides for normal braking or steer-by-braking (SBF) .

As is known, with this type of pedal arrangement

14, when the driver presses the left (or right) pedal only, the brake apparatus only brakes the rear left (or right) wheel, thus reducing the turn radius of the tractor, especially during headland manoeuvres.

A circuit 15 is connected to tank 13a to feed high- pressure (e.g. 8-bar) air to a brake valve 16 of a trailer (not shown) and to a high-pressure coupling 17 forming part of an assembly BTG for connecting a trailer brake apparatus (neither shown) .

As shown in the attached drawing, a first adjustable low-pressure air circuit Cl and a second adjustable low-pressure air circuit C2 originate from pedal arrangement 14.

First circuit Cl comprises two branches Rl, R2, of which a first branch Rl connects pedal arrangement 14 pneumatically to the trailer brake valve 16, and a second branch R2 connects pedal arrangement 14 pneumatically to two front ABS modulators 18, 19.

ABS modulator 18 regulates compressed-air supply to a corresponding pneumatic/hydraulic converter 20, which converts the incoming energy, in the form of compressed air, to hydraulic energy to power a corresponding front right brake 21 of a front right wheel (not shown) fitted to an axle AXLl with a conventional differential DFl.

Likewise, ABS modulator 19 regulates compressed-air

supply to a corresponding pneumatic/hydraulic converter 22, which converts the incoming energy, in the form of compressed air, to hydraulic energy to power a corresponding front left brake 23 of a front left wheel (not shown) also fitted to axle AXLl.

A speed sensor SSl and speed sensor SS2 are provided for determining the speed of the front right wheel and front left wheel respectively.

ABS modulators 18, 19 and front-wheel speed sensors SSl, SS2 are connected electrically to an electronic central control unit CNT for the reasons explained below.

Second circuit C2 comprises two branches RMl and RM2. Like branch Rl of circuit Cl, a first branch RMl connects pedal arrangement 14 pneumatically to valve 16; and the second branch RM2 connects pedal arrangement 14 pneumatically to two rear ABS modulators 24, 25.

ABS modulator 24 regulates compressed-air supply to a corresponding pneumatic/hydraulic converter 26, which converts the incoming energy, in the form of compressed air, to hydraulic energy to power a corresponding rear right brake 27 of a rear right wheel (not shown) fitted to an axle AXL2 with a conventional differential DF2. Likewise, ABS modulator 25 regulates compressed-air supply to a corresponding pneumatic/hydraulic converter 28, which converts the incoming energy, in the form of compressed air, to hydraulic energy to power a

corresponding rear left brake 29 of a rear left wheel (not shown) also fitted to axle AXL2.

A speed sensor SS3 and speed sensor SS4 are provided for determining the speed of the rear right wheel and rear left wheel respectively.

ABS modulators 24, 25 and rear-wheel speed sensors SS3, SS4 are also connected electrically to electronic central control unit CNT.

Between valve 16 and assembly BTG (more specifically, between valve 16 and a fitting 31 forming part of assembly BTG) is interposed an electric valve 30, through which flows the adjustable low-pressure compressed air flowing along first branch RMl of circuit C2 to assembly BTG. Electric valve 30 is a normally-open type controlled by electronic central control unit CNT.

Apparatus 10 according to the present invention operates as follows:

(A) To simply brake the tractor and trailer (if any) , the driver acts accordingly on pedal arrangement

14; compressed air, adjustable according to driver operation of pedal arrangement 14, is supplied simultaneously to the four ABS modulators, thus initiating braking of all four wheels, which is regulated electronically by electronic central control unit CNT using ABS logic.

(B) To simply brake the tractor towing a trailer, electric valve 30 is open, and so permits adjustable-air

flow to assembly BTG.

(C) Conversely, to implement the steer-by-braking function (SBF) using pedal arrangement 14, since nothing is gained - in fact, driver safety is even jeopardized - by also involving the trailer, electronic central control unit CNT closes electric valve 30 to cut off adjustable-air supply to assembly BTG.

(D) The four wheel speeds detected by sensors SSl, SS2, SS3, SS4 and transmitted to electronic central control unit CNT obviously also play their part in controlling both normal braking of the four wheels (with electric valve 30 open) , and steer-by-braking (SBF)

(with electric valve 30 closed) of either the rear right wheel by brake 27, or the rear left wheel by brake 29, depending on the desired turn direction.

Apparatus 10 also comprises a line CAP, which starts immediately downstream from tank 13b and feeds high-pressure air to a normally-closed valve 50. Valve 50 is connected electrically to electronic central control unit CNT, and may be either an ON/OFF or gradually opened type (see below) .

Branch RM2 is fitted with a comparing valve 60 connected pneumatically to valve 50 by a line 70.

More specifically, comparing valve 60 divides branch RM2 into two portions TR* and TR**.

As will be seen in the operating description of apparatus 10 below, comparing valve 60 determines the instantaneous air pressure at a point Pl along portion

TR* and a point P2 along line 70, compares the pressures at points Pl and P2, and opens on the higher-pressure side .

In other words, if comparing valve 60 detects a higher pressure at point P2 than at point Pl, it opens on the line 70 side to connect line 70 to portion TR**.

Conversely, if comparing valve 60 detects a higher pressure at point Pl than at point P2, it opens on the portion TR* side to connect portion TR* to portion TR**. Comparing valve 60 and points Pl and P2 are also connected electrically to electronic central control unit CNT.

Line CAP, valve 50, line 70, and comparing valve 60 form a device DS for supplying high-pressure air, and selecting the maximum pressure of the air supply, to rear modulators 24, 25.

Electronic central control unit CNT is also connected electrically to an acceleration sensor 80, which, even when the tractor is stationary uphill, detects negative acceleration (with respect to the travelling direction of the tractor) caused by gravity which, as is known, tends to pull the tractor in reverse .

Electronic central control unit CNT is also connected electrically to a tractor speed sensor 90; a sensor 100 connected to the accelerator pedal (not shown) ; and a travelling direction sensor 110 (forward

(F) or reverse (B) ) .

Apparatus 10 according to the present invention operates as follows:

(E) When the tractor is stopped uphill (e.g. by a red light), this is detected by acceleration sensor 80, which accordingly transmits a signal to electronic central control unit CNT. (Alternatively, reverse movement with a forward gear engaged may be detected) .

(F) Electronic central control unit CNT therefore transmits a signal to normally-closed valve 50, which opens to set line 70 to high pressure (e.g. of 8 bars) .

(G) On comparing the pressures at points Pl and P2 and determining a higher pressure at point P2 than at point Pl (because pedal arrangement 14 is not pressed by the driver, so circuits Cl and C2 are discharged) , comparing valve 60 connects line 70 to portion TR** to feed high-pressure air to modulators 24, 25.

(H) Converters 26, 28 therefore activate rear brakes 27, 29, which act as parking brakes.

(I) When the driver presses the accelerator pedal, sensor 100 transmits a signal to central control unit CNT, which electronically closes valve 50 to discharge modulators 24, 25.

(L) At this point, the pressure at point P2 falls to zero, so that the pressure at point Pl is higher than at point P2, and comparing valve 60 reconnects portions TR* and TR** of branch RM2 and disconnects line 70 from portion TR**, thus restoring the original braking apparatus .

Though the above description with reference to the attached drawing refers to a particular electronic apparatus employing ABS logic, the teachings of the present invention also apply to any electronically controlled brake apparatus, such as the brake-by-wire apparatus .

Similarly, though the above description refers to an apparatus comprising four ABS modulators, the teachings of the present invention may also be applied to three-channel apparatuses (i.e. with two ABS modulators for the rear wheels, and one ABS modulator for both the front wheels) , or even to two-channel apparatuses (i.e. with only two ABS modulators for the rear wheels) . The apparatus according to the present invention provides for the following functions:

(1) ABS electronic braking;

(2) Electronic steer-by-braking (e-SBF) ;

(3) Yaw moment control (YMC) ; (4) Cornering brake control (CBC) for stabilizing and preventing the tractor from swerving when braking around bends; this control operates with no intervention on the part of the ABS apparatus;

(5) Dynamic drift control (DDC) for stabilizing the vehicle when braking around bends, and preventing swerving during intervention of the ABS apparatus;

(6) Electronic brake distribution (EBD) to avoid damaging the clutch;

(7) Autonomous steer-by-braking function (ASBF) . In this case, when the driver turns the steering wheel, the electronic steer-by-braking function (e-SBF) is activated automatically to assist steering with no direct intervention by the driver on the brake pedals; electronic central control unit CNT opens valve 50 and simultaneously discharges modulator 24 to turn left; and, at the same time, high pressure is supplied from valve 50 to brake 29 via modulator 25. The same also applies when the driver makes a right turn.

(8) Hill holder (HH) . As already described, this function provides for automatically keeping the tractor braked uphill, without using the handbrake.

(9) Traction control apparatus (ASR) . This function is engaged automatically when the driver, for example, accelerates on muddy ground, and one wheel starts spinning. When the ASR function is engaged, the apparatus automatically only brakes the spinning wheel to transfer torque to the wheel on solid ground. If the left wheel is spinning, electronic central control unit CNT opens valve 50 and simultaneously discharges modulator 24; at the same time, high pressure is supplied from valve 50 to brake 29 via modulator 25, so that the left wheel is braked and stops spinning, thus improving traction of the right wheel. This also prevents over-revving of the tractor engine, and ensures more power to the wheel with traction.

The advantages of the present invention are as

fol lows : uphill re-starting of the tractor no longer requires use of the handbrake; the ASBF function simplifies manoeuvring in confined spaces, without the driver having to operate the brake pedals; and

- the ASR function improves traction over rough ground, without the driver having to engage the differential lock.