Method to control a transmission brake

A method of controlling a transmission brake of an automated change-speed transmission, of a countershaft design provided with claw clutches, the transmission brake is functionally connected, on an input side thereof to a transmission shaft and is actuated either hydraulically or pneumatically by an inlet valve and an outlet valve, each of the inlet and the outlet valves is a 2/2-way magnetic switching valve, such that for an upshift from a gear under load to a target gear, when the loaded gear has been disengaged, to synchronize the target gear, first the inlet valve is opened and the outlet valve is closed, then to produce a substantially constant torque (MBr), the inlet valve is closed after having been open for a determinable opening time duration (TVE), and to reach a synchronous rotational speed, the outlet valve is opened after having been closed for a determinable closing time duration (TVA), the opening time duration (TVE) for which the inlet valve is open being determined as a function of a specified characteristic parameter of the synchronization process, the method comprising the steps of:

• detecting, with sensors, an initial input rotational speed (nE—0) and a corresponding initial output rotational speed (nA—0) existing at a beginning of the synchronization process (t=t0);
• determining, with a transmission control unit and from the initial input and the initial output rotational speeds, an input speed gradient (ngE—W) and a corresponding output speed gradient (ngA)existing before activation of the transmission brake;
• determining, with the transmission control unit, a necessary braking gradient (ngE—Br) of the input shaft from values of the determined input and the output speed gradients existing before activation of the transmission brake and from transmission-specific and brake-specific characteristic valves, for a specified application duration (TH)of the transmission brake at a constant braking torque(MBR=const.);
• determining, with the transmission control unit, a needed brake pressure (pBr)to be produced in the transmission brake for obtaining the necessary braking gradient (ngE—Br);
• determining with the transmission control unit, the opening time duration ( TVE)of the inlet valve required in order to produce the needed brake pressure(pBr)as a function of a current brake pressure (pV) that is currently being supplied to the transmission brake;
• and
• calculating the needed brake pressure (PBr)to be produced in the transmission brake from the necessary braking gradient (ngE—Br) using the equation:
• pBr=pBr—0−ngE—Br*FBr
• wherein Pbr is the needed brake pressure to be produced in the transmission brake,
• pBr—0 is a device-specific pressure offset of the transmission brake,
• ngE—Br is the necessary braking gradient, and
• FBr is a device-specitic proportionality factor of the transmission brake.

A method of controlling a transmission brake of an automated change-speed transmission, of a countershaft design provided with claw clutches, the transmission brake is functionally connected, on an input side thereof to a transmission shaft and is actuated either hydraulically or pneumatically by an inlet valve and an outlet valve, each of the inlet and the outlet valves is a 2/2-way magnetic switching valve, such that for an upshift from a gear under load to a target gear, when the loaded gear has been disengaged, to synchronize the target gear, first the inlet valve is opened and the outlet valve is closed, then to produce a substantially constant braking torque (MBr), the inlet valve is closed after having been open for a determinable opening time duration (TVE), and to reach a synchronous rotational speed, the outlet valve is opened after having been closed for a determinable closing time duration (TVA), the opening time duration (TVE) for which the inlet valve is open being determined as a function of a specified characteristic parameter of the synchronization process, the method comprising the steps of:

• detecting, with sensors, an initial rotational speed (nE—0) and a corresponding initial output rotational speed (nA—0) existing at a beginning of the synchronization process (t=t0);
• determining, with a transmission control unit and from the initial input and the initial output rotational speeds, an input speed gradient(nE—W) and a corresponding output speed gradient (ngA) existing before activation of the transmission brake;
• determining, with the transmission control unit, a necessary braking gradient (ngE—Br) of the input shaft from values of the determined input and the output speed gradients existing before activation of the transmission brake and from transmission-specific and brake-specific characteristic values, for a specified application duration (TH) of the transmission brake at a constant braking torque (MBr =const.);
• determining, with the transmission control unit, a needed brake pressure (pBr) to be produced in the transmission brake for obtaining the necessary braking gradient (ngE—Br);
• determining, with the transmission control unit, the opening time duration (TVE) of the inlet valve required in order to produce the needed brake pressure (pBr) as a function of a current brake pressure (pv) that is currently being supplied to the transmission brake;
• and
• determining the necessary opening time duration (TVE) of the inlet valve for the needed brake pressure (pBr) to be produced in the transmission brake from a family of several characteristic curves determined for different supply pressures (pv).

A method of controlling a transmission brake of an automated change-speed transmission, of a countershaft design provided with claw clutches, the transmission brake is functionally connected, on an input side thereof to a transmission shaft and is actuated either hydraulically or pneumatically by an inlet valve and an outlet valve, each of the inlet and the outlet valves is a 2/2-way magnetic switching valve, such that for an upshift from a gear under load to a target gear, when the loaded gear has been disengaged, to synchronize the target gear, first the inlet valve is opened and the outlet valve is closed, then to produce a substantially constant braking torque (MBr), the inlet valve is closed after having been open for a determinable opening time duration (TVE), and to reach a synchronous rotational speed, the outlet valve is opened after having been closed for a determinable closing time duration (TVA), the opening time duration (TVE) for which the inlet valve is open being determined as a function of a specified characteristic parameter of the synchronization process, the method comprising the steps of:

• detecting, with sensors, an initial rotational speed (nE—0) and a corresponding initial output rotational speed (nA—0) existing at a beginning of the synchronization process (t=t0);
• determining, with a transmission control unit and from the initial input and the initial output rotational speeds, an input speed gradient(nE—W) and a corresponding output speed gradient (ngA) existing before activation of the transmission brake;
• determining, with the transmission control unit, a necessary braking gradient (ngE—Br) of the input shaft from values of the determined input and the output speed gradients existing before activation of the transmission brake and from transmission-specific and brake-specific characteristic values, for a specified application duration (TH) of the transmission brake at a constant braking torque (MBr =const.);
• determining, with the transmission control unit, a needed brake pressure (pBr) to be produced in the transmission brake for obtaining the necessary braking gradient (ngE—Br);
• determining, with the transmission control unit, the opening time duration (TVE) of the inlet valve required in order to produce the needed brake pressure (pBr) as a function of a current brake pressure (pv) that is currently being supplied to the transmission brake;
• and
• determining the necessary opening time duration (TVE) of the inlet valve for the needed brake pressure (pBr) to be produced in the transmission brake from a single characteristic line that has been determined from a family of several characteristic curves determined for different supply pressures (pv).