Electronic monitoring system for hydrostatic travel drives and travel drive with electronic monitoring system

Abstract

A monitoring system for a travel drive includes a rotational speed sensor of a hydrostatic motor. The rotational speed sensor is configured to determine acceleration. At least one signal from a pressure sensor mounted on at least one working line that connects a pump to the hydrostatic motor of a hydrostatic travel drive is evaluated. The pressure sensor is preferably arranged on at least one working connection of the pump. The system uses the additional pressure signal to evaluate in a reliable manner whether the hydrostatic travel drive generates an unwanted drive torque.

Claims

1. An electronic monitoring system for a hydrostatic drive that has a control element for transmitting a standstill signal or a no-drive signal, a hydrostatic pump, and a hydrostatic motor, the electronic monitoring system comprising: an electronic control unit configured to receive the standstill signal and/or the no-drive signal; a revolution rate sensor operably connected to the electronic control unit and configured to detect a motor revolution rate; and a first pressure sensor operably connected to the electronic control unit, wherein the electronic control unit is configured to detect an acceleration of the hydrostatic motor from the motor revolution rate, and wherein the first pressure sensor is configured to transmit a first pressure of a first working line of the hydrostatic drive to the electronic control unit, with which the electronic control unit is configured to determine a drive state and/or a no-drive state of the hydrostatic drive.

2. The electronic monitoring system as claimed in claim 1 further comprising: a second pressure sensor operably connected to the electronic control unit and configured to transmit a second pressure of a second working line to the electronic control unit.

3. The electronic monitoring system as claimed in claim 2, wherein: the electronic control unit is configured to determine a pressure difference between the first pressure and the second pressure, and the electronic control unit is configured to determine an error (i) when the standstill signal or the no-drive signal is transmitted to the electronic control unit, and (ii) when additionally the following three conditions are met: a motor revolution rate>0, the pressure difference>=a reference value for the pressure difference, and the acceleration>a negative reference value for the acceleration.

4. The electronic monitoring system as claimed in claim 2, wherein: the electronic control unit is configured to determine a pressure difference between the first pressure and the second pressure, and the electronic control unit is configured to detect an error (i) when the standstill signal or the no-drive signal is transmitted to the electronic control unit from an operating unit, and (ii) when the following three conditions are also met: a motor revolution rate<0, the pressure difference<=a negative reference value for the pressure difference, and the acceleration<a reference value for the acceleration.

5. A hydrostatic travel drive comprising: an electronic monitoring system including an electronic control unit, a revolution rate sensor, and a first pressure sensor; a control element operably connected to the electronic monitoring system and configured to transmit a standstill signal or a no-drive signal to the electronic control unit of the electronic monitoring system; a hydrostatic pump; and a hydrostatic motor, wherein the revolution rate sensor is configured to detect a motor revolution rate, wherein the electronic control unit is configured to detect an acceleration of the hydrostatic motor from the motor revolution rate, and wherein the first pressure sensor is configured to transmit a first pressure of a first working line of the hydrostatic travel drive to the electronic control unit, whereby a drive state and/or a no-drive state of the hydrostatic travel drive is determined.

6. The hydrostatic travel drive as claimed in claim 5, further comprising: a closed circuit with a second working line, wherein the electronic monitoring system has a second pressure sensor configured to transmit a second pressure of the second working line to the electronic control unit.

7. The hydrostatic travel drive as claimed in claim 6, wherein: the electronic control unit is configured to determine a pressure difference between the first pressure and the second pressure, and the electronic control unit is configured to detect an error (i) when the standstill signal or the no-drive signal is detected by the electronic control unit, and (ii) when the following three conditions are also met: the motor revolution rate>0, the pressure difference>=a reference value for the pressure different, and the acceleration>a negative reference value for the acceleration.

8. The hydrostatic travel drive as claimed in claim 6, wherein: the electronic control unit is configured to determine a pressure difference between the first pressure and the second pressure, and the electronic control unit is configured to detect an error (i) when the standstill signal or the no-drive signal is transmitted from an operating unit to the electronic control unit of the monitoring system, and (ii) when additionally the following three conditions are met: the motor revolution rate<0, the pressure difference<=a negative reference value for the pressure difference, and the acceleration<a reference value for the acceleration.

9. The hydrostatic travel drive as claimed in claim 5, wherein: the electronic control element is a direction of travel lever in a neutral position, the electronic control element is a gas pedal in a zero position, or the electronic control element is an inch pedal in a maximum position.

10. The hydrostatic travel drive according to claim 5, wherein: the hydrostatic pump is an ET pump, and non-stiff and non-pedal-driven control of the ET pump is provided via a control pressure.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The FIGURE is a block diagram of a travel drive as disclosed herein.

DETAILED DESCRIPTION

(2) The FIGURE shows an exemplary embodiment of the travel drive according to the disclosure for a mobile working machine, which can be, for example, a wheel loader. The mobile working machine has a diesel engine 1, to the crankshaft of which (not shown in detail) is coupled an axial piston pump 2 with an adjustable stroke volume. This supplies in a closed circuit via two working lines 4.sub.A, 4.sub.B a motor 6, the output shaft of which is coupled to two wheels 10 via a differential gearbox 8. The pump 2, the two working lines 4.sub.A, 4.sub.B and the motor 6 are the travel drive according to the disclosure.

(3) A gas pedal 12 is mechanically coupled to the diesel motor 1 in the exemplary embodiment shown.

(4) Furthermore, the travel drive according to the disclosure has a central data line 14, to which an electronic control unit 15 is connected. Position data or position signals of the gas pedal 12, a direction lever 11 and an inch pedal 17 are transmitted via the central data line 14. The inch pedal 17 is used by users of the mobile working machine for preference compared to the travel drive.

(5) Furthermore, pressure signals of a first pressure sensor 16.sub.A and a second pressure sensor 16.sub.B are transmitted to the control unit 15 via the central data line 14. The two pressure sensors 16.sub.A, 16.sub.B are connected to the two main ports of the pump 2 and record the working pressure of the respective working line 4.sub.A, 4.sub.B.

(6) Furthermore, a pump revolution rate np from a (not shown) revolution rate sensor and a motor revolution rate n.sub.m from a revolution rate sensor 18.sub.M are transmitted to the control unit 15.

(7) A control pressure signal P.sub.St is transmitted from the control unit 15 via the central data line 14, wherein the pump 2 is in the form of an ET pump.

(8) In a preferred alternative exemplary embodiment, the pump 2 is not controlled via the central data line 14, but via two separate electrical lines (not shown in detail), by means of which two control current signals for solenoid valves of the pump 2 are transmitted.

(9) As an example, the safety function “safe standstill” or safe no-drive of the exemplary embodiment shown of the travel drive according to the disclosure is described. The safety function prevents unintentional active acceleration of the mobile working machine by the driver with the travel drive.

(10) The following driver control elements are evaluated by the control unit 15: Direction of travel lever 11, Gas pedal 12 and Inch pedal 17.

(11) The driver demands standstill or no drive if at least one of the following conditions is met: Direction of travel lever 11 is in “neutral” position, Gas Pedal 12 is in zero position or Inch pedal 17 is in maximum position.

(12) Other control elements such as a creep potentiometer and their evaluation are also possible.

(13) In particular then the following sensors are evaluated: Revolution rate sensor 18.sub.M on the hydrostatic motor 6 (motor revolution rate symbol: n.sub.M), First pressure sensor 16.sub.A on the hydrostatic pump 2 or on the first working line 4.sub.A (symbol for the first pressure: p.sub.A) and Second pressure sensor 16.sub.B on the hydrostatic pump 2 or on the second working line 4.sub.B (symbol for the second pressure: p.sub.B).

(14) The acceleration a is calculated numerically from the revolution rate signal n.sub.M. More specifically, the angular acceleration of the motor 6 is determined and the acceleration of the mobile working machine may be calculated numerically from this. The pressure difference Δp is formed from the two pressure signals p.sub.A and p.sub.B.

(15) The pressure difference Δp is always calculated by convention in such a way that a positive pressure difference Δp means an active drive torque in the forward direction. This is important for the formulation of the error condition for the pressure difference Δp. Depending on the installation position of the pressure sensors 16.sub.A, 16.sub.B and the hose of the hydrostatic drive, Δp=p.sub.A−P.sub.B or Δ.sub.p=P.sub.B−P.sub.A.

(16) If the driver demands a standstill or no drive by means of one of the above-mentioned control elements, and one of the following two conditions is met, then there is an error that is detected by the monitoring system according to the disclosure.

(17) 1. (n.sub.M>0) and (Δp>=Δp.sub.Ref) and (a>−a.sub.Ref)

(18) 2. (n.sub.M<0) and (Δp<=−Δp.sub.Ref) and (a<a.sub.Ref)

(19) Δp.sub.Ref and a.sub.Ref are reference values for pressure difference and acceleration that can also be time-dependent. The first condition means that the mobile working machine is moving forwards and there is a significant or excessive pressure difference Δp (relative to the reference value Δp.sub.Ref) from which a significant or excessive forward driving torque (relative to the reference value) results, with the forward acceleration a being significant or excessive (relative to the reference value −a.sub.Ref).

(20) In the case of the bidirectional drive with a closed circuit shown in the FIGURE, the second condition applies analogously to reversing. The second condition therefore means that the mobile working machine is reversing, and there is a significant or excessive pressure difference Δp (relative to the reference value −Δp.sub.Ref). This will result in a significant or excessive rearward driving torque (relative to the reference value). The rearward acceleration a is significant or excessive (relative to the reference value a.sub.Ref).

(21) When the error is detected in this way by the monitoring system, the electronic control unit 15 switches off all electrical outputs in order to finally switch off the travel drive and bring the mobile working machine into a safe state.

(22) A monitoring system for a travel drive and a travel drive with a monitoring system are disclosed. An acceleration is determined by means of a revolution rate sensor of a hydrostatic motor, and additionally at least one pressure sensor is evaluated, which is installed on the at least one working line that connects the pump to the motor of the hydrostatic travel drive. Preferably, the pressure sensor is arranged on the at least one working port of the pump. Using the additional pressure signal, it can be evaluated whether the hydrostatic drive motor generates an unintentional driving torque or not.