Patent Application
20140032056
The present disclosure relates generally to machines and, more particularly, to systems and methods for neutralizing transmission of machines.
Many machines used in earth-moving, industrial and agricultural applications have a transmission neutralizer feature that allows an operator to manually control the neutralization or disengagement of the transmission. Such machines include, but are not limited to, wheel loaders, track-type tractors, excavators, articulated trucks and the like. With such systems, the operator may choose to neutralize the transmission depending on the operating conditions and application of the brake pedal. For example, when operating on level ground, the operator may neutralize the transmission early in the brake application. While operating on a slope, the operator may choose to neutralize the transmission deeper into the brake application to prevent rollback of the machine.
On conventional machines, there are multiple push buttons that the operator must toggle through in order to neutralize the transmission. Controlling the transmission with multiple push buttons not only requires operators with high skill levels, but also requires the operator to repeatedly switch modes of the transmission during operation. Given that operators have several other tasks to perform and mechanisms to control while operating the machine, the operators may become fatigued, overburdened, or frustrated due to the complexity of the controls. Furthermore, because the manual control settings of the transmission neutralizer require the hands of the operators to travel from one push button to another, there is an inherent reaction time delay.
Thus, there exists a need for an improved, reliable and efficient system and method for neutralizing transmissions in such machines. U.S. pre-grant publication 2009/0132134 A1 discloses an inch/brake device for a transmission having a control system that uses brake pedal position and accelerator pedal position as inputs. U.S.2009/0132134 A1 discloses a first range of motion of the inch/brake device providing a transmission engagement force and a second range of motion providing a braking force. U.S.2009/0132134 A1 further discloses an accelerator moving between two or more positions, wherein moving the accelerator causes an overlap between the first range of motion and the second range of motion to vary. However, U.S.2009/0132134 A1 does not disclose controlling a transmission by calculating outside forces acting on the machine.
One aspect of the present disclosure is directed to an automatic transmission neutralizer system for a machine. The system may include at least one sensor configured to detect a set of parameters of the machine, a transmission, and a control unit operatively in communication with the at least one sensor and the transmission. The control unit may be configured to: calculate a braking force of the machine and an external force on the machine using the set of parameters detected by the at least one sensor, compare the braking force to the external force, and selectively neutralize the transmission depending on input from the at least one sensor and the comparison of braking force to external force.
Another aspect of the present is directed to a machine having an automatic transmission neutralizer system. The machine may comprise a brake pedal having a brake pedal sensor configured to detect an angle of depression of the brake pedal; a torque converter having an input sensor and an output sensor, the input sensor configured to detect a speed going into the torque converter and the output sensor configured to detect a speed coming out of the torque converter; a transmission system comprising a transmission, a transmission shaft, and a transmission control module; a speed sensor configured to detect a speed of the transmission shaft; and a control unit operatively in communication with the brake pedal sensor, input sensor, output sensor, speed sensor, and transmission control module. The control unit may be configured to: calculate a braking force of the machine using input from the brake pedal sensor; calculate a propulsion force of the machine using input from the input sensor and the output sensor of the torque converter; calculate an acceleration of the machine using input from the speed sensor; calculate an external force on the machine as a function of the braking force, the propulsion force of the machine, a mass and the acceleration of the machine; compare the braking force to the external force; and output a signal to the transmission control module to selectively disengage the transmission based on input from the brake pedal sensor and the comparison of the braking force to the external force.
Another aspect of the present disclosure is directed to a transmission neutralizer system for a machine. The machine may include a transmission and a brake pedal having a brake pedal sensor configured to detect a position of the brake pedal. The transmission neutralizer system may include a transmission control module configured to disengage the transmission, and a control unit in communication with the transmission control module and the brake pedal sensor. The control unit may be configured to: calculate a braking force and an external force; compare the braking force to the external force; and send a signal to the transmission control module to disengage the transmission based on input from the brake pedal sensor and the comparison of the braking force to the external force.
Another aspect of the present disclosure is directed to a method of neutralizing a transmission of a machine is disclosed. The method may include monitoring a brake pedal position; calculating an external force on the machine; comparing the braking force to the external force; and selectively neutralizing the transmission according to the brake pedal position and comparison of the braking force to the external force.
These and other aspects and features of the invention will become more readily apparent upon reading the following detailed description when taken in conjunction with the accompanying drawings.
Although various features are disclosed in relation to specific exemplary embodiments, it is understood that the various features may be combined with each other, or used alone, with any of the various exemplary embodiments of the invention without departing from the scope of the claimed invention.
While the present disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof will be shown and described below in detail. The invention is not limited to the specific embodiments disclosed, but instead includes all modifications, alternative constructions, and equivalents thereof.
Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding reference numbers will be used throughout the drawings to refer to the same or corresponding parts.
Turning now to
That being said, the machine 12 may include an engine 13, a transmission system 14, a control unit 16 for controlling the machine 12, a brake pedal 18, and a torque converter 20. The transmission system 14 may comprise a transmission 22, a transmission shaft 24, and a transmission control module 26 for controlling the transmission 22. The control unit 16 may be in communication with the transmission control module 22 and at least one sensor, such as, but not limited to, a brake pedal sensor 28 configured to detect an angle of depression of the brake pedal 18, a speed sensor 30 configured to detect a speed of the transmission shaft 24, an input sensor 32 configured to detect a speed going into the torque converter 20, and an output sensor 34 configured to detect a speed coming out of the torque converter 20.
Turning now to
According to one exemplary embodiment of the present disclosure, the transmission 22 of the machine 12 may be disengaged or neutralized when the braking force Fb is greater than or equal to the external force Fe. The braking force Fb of the machine 12 may be calculated by first determining a brake pressure of the brake system of the machine. One way the brake pressure may be determined is by the position of the brake pedal 18. Specifically, the brake pedal sensor 28 may detect the angle of depression of the brake pedal 18 and send a corresponding signal to the control unit 16. Based on data programmed into the control unit 16 regarding the approximate brake pressure that correlates to the angle of depression of the brake pedal 18, the control unit 16 may then estimate the brake pressure. Another way the brake pressure may be determined is by directly detecting the brake pressure via a brake pressure sensor (not shown) which may be in communication with the control unit 16. The brake pressure sensor may detect the brake pressure by measuring a hydraulic oil pressure of the brake system and may send a corresponding signal to the control unit 16. After the brake pressure is determined, the control unit 16 may calculate the braking force Fb based on characteristics of the brake system and dimensions of the moving parts of the machine 12. For example, the control unit 16 may use programmed data relating to the brake disc area, clutch dimensions, tire radius, gear reduction ratios, or other parameters, to calculate the braking force Fb from the determined brake pressure.
From the free body diagram shown in
ΣF=m·a
The summation of all the forces includes the braking force Fb, external force Fe, and propulsion force Fp, and substituting these forces into the above equation results in the following equation:
Fb+Fe+Fp=m·a
After manipulating the above equation to solve for the external force Fe, the following formula results:
Fe=m·a−Fb−Fp
The control unit 16 may use the above formula to calculate the external force Fe on the machine 12. The calculation of braking force Fb described above may be used in the formula for external force Fe. To calculate the propulsion force Fp of the machine, the input sensor 32 and output sensor 34 of the torque converter 20 may send signals corresponding to the torque converter 20 input speed and output speed, respectively, to the control unit 16. Using these signals, as well as known torque converter 20 properties, what gear the transmission 22 of the machine 12 is in, associated gear reduction ratios of the machine, the tire radius, or other parameters of the machine 12 programmed into the control unit 16, the control unit 16 may then calculate the propulsion force Fp. For the m·a calculation, the known mass of the machine 12 may be programmed into the control unit 16, while the acceleration of the machine 12 may be determined from inputs provided by the speed sensor 30. More specifically, the speed sensor 30 may detect the rotational speed of the transmission shaft 24 and send a corresponding signal to the control unit 16. The control unit 16 may then determine the speed of the machine 12 based on the rotational speed of the transmission shaft 24 and the dimensions of the moving parts of the machine 12, such as the tire radius and gear reduction ratios. Next, the control unit 15 may calculate the acceleration of the machine 12, or the derivative of the speed of the machine 12, by monitoring the rate at which such speed is changing.
It will be understood that although the system and method described above for calculating braking force Fb and external force Fe has been disclosed herein, other systems and methods may be used without departing from the scope of the invention. For example, according to yet another embodiment of the present disclosure, an inclinometer may be used to determine the grade or angle of inclination on which the machine 12 is operating. The inclinometer (not shown) may be in communication with the control unit 16, which may then use the measured angle input from the inclinometer, as well as the known mass of the machine 12 and acceleration of gravity to calculate the external force Fe.
After calculating the braking force Fb of the machine 12 and the external force Fe on the machine 12 as described above, the control unit 16 compares the braking force Fb to the external force Fe. If the braking force Fb is equal to or greater than the external force Fe, then the control unit 16 may output a signal to disengage or neutralize the transmission 22. More specifically, the control unit 16 may send a signal to the transmission control module 26, which may then put the transmission 22 into neutral.
Turning now to
At step 66, and as shown by comparator 44, if the minimum brake pedal position is met, then the control unit 16 may compare the detected brake pedal position to a maximum brake pedal position or maximum angle of depression of the brake pedal 18, which may be programmed into the control unit 16. If the maximum brake pedal position is met, then the control unit 16 may output a signal to neutralize the transmission 22. In this case, the transmission would be neutralized regardless of the external force because of the significant application of the brake pedal 18.
At step 68, and as shown by gate 46, if there is sufficient application of the brake pedal 18 but the maximum brake pedal position has not been met, then the control unit 16 may determine whether the machine 12 is moving below a threshold speed. More specifically, the control unit 16 may compare the machine 12 speed, which can be determined based on input from the speed sensor 30 (as described above), to a threshold speed that may be programmed into the control unit 16. If the machine is not moving below the threshold speed, then at step 70, the control unit 16 calculates the external force Fe, as described in detail above. However, if the machine 12 is moving below the threshold speed, then at step 72, the control unit 16 may latch or hold the last known calculation for external force Fe for the following process (step 74) of comparing the braking force Fb to external force Fe. At low speeds, the detected or calculated parameters may become less accurate due to friction or other circumstances. Thus, the control unit 16 may compensate for this by using the last known or most recent calculation of external force Fe once the machine 12 operates below the threshold speed.
At step 74, and as shown by comparator 48, the control unit 16 compares the braking force Fb to the external force Fe. If the braking force Fb is greater than or equal to the external force Fe, then the control unit 16 may output a signal to neutralize the transmission 22 (at step 76) because there is sufficient braking force Fb to prevent roll back of the machine 12. If the braking force Fb is less than the external force Fe, then the transmission 22 is not disengaged.
It will be understood that although the steps 62-76 of the method shown in the flowchart of
In general, the foregoing disclosure finds utility in various industrial applications, such as in earth-moving, industrial, construction and agricultural machines. In particular, the disclosed transmission neutralizer system and method may be applied to wheel loaders, and the like. By applying this system and method to a machine, such as a wheel loader, automatic neutralization of a transmission can be achieved. Furthermore, the automatic transmission neutralizer system and method disclosed herein provides for adaptive selection of the transmission neutralizer setpoint. Thus, the present invention adapts the neutralization setpoint to the operating conditions of the machine, thereby resulting in a reliable and efficient system and method for neutralizing transmissions, while eliminating the need for an operator of the machine to manually select control settings in order to neutralize the transmission during operation.
While the foregoing detailed description has been given and provided with respect to certain specific embodiments, it is to be understood that the scope of the disclosure should not be limited to such embodiments, but that the same are provided simply for enablement and best mode purposes. The breadth and spirit of the present disclosure is broader than the embodiments specifically disclosed and encompassed within the claims appended hereto.
While some features are described in conjunction with certain specific embodiments of the invention, these features are not limited to use with only the embodiment with which they are described, but instead may be used together with or separate from, other features disclosed in conjunction with alternate embodiments of the invention.
