The controller can be operated at different engine speeds and the controller can be operated in one of three different POWER modes.
The controller receives signals from the engine speed dial switch, the power mode selector switch and the engine speed sensor. The controller processes the information and the controller sends a signal to the proportional reducing valve solenoid. The proportional reducing valve changes the electric signal into a hydraulic signal (power shift pressure). The power shift pressure is used to regulate the output of the pump. As the power shift pressure increases, the pump will destroke in order to decrease the output of the pump. If the power shift pressure decreases, the pump will upstroke in order to increase the output of the pump. For more information about the flow control by the pump regulator, see Systems Operation, "Hydraulic System" for the machine that is being serviced.
| Speed Settings for the 345 Excavators | |
|---|---|
| Engine Speed Dial | RPM |
| 1 (1) |
800 (2) |
| 2 | 1000 |
| 3 | 1150 |
| 4 | 1300 |
| 5 | 1450 |
| 6 | 1600 |
| 7 | 1750 |
| 8 | 1900 |
| 9 | 2050 |
| 10 (3) | 2150 |
| ( 1 ) | Position 1 of the engine speed dial is for LOW IDLE. The "tortoise" is used for the LOW IDLE setting. |
| ( 2 ) | Position 1 of the engine speed dial corresponds to 880 rpm for the following machines: AGS, ALB, APB |
| ( 3 ) | Position 10 of the engine speed dial is for HIGH IDLE. The "rabbit" is used for the HIGH IDLE setting. |
Pump output is regulated according to the position of the engine speed dial. The dial position of 10 will cause a minimum of power shift pressure for a maximum allowable output for the pump. As the dial is turned in a direction to decrease the speed, the power shift pressure will increase for a decreased output in the pump. The maximum allowable pump output is set with the power mode selector switch. The power mode switch provides two modes, power mode and standard mode. When an indicator that is next to the power mode switch illuminates by pushing the power mode switch, the power mode is selected and 100 percent of the engine output is available. When the indicator is turned off, standard mode is selected and 90 percent of engine output is available.
The figure that is shown below represents the pressure/flow characteristic curves for three power modes. With the engine speed dial in the 10 position, the output of the pump in each mode is listed:
Power Mode - 100 percent
Standard Mode - 90 percent
Fine Control Mode - 70 percent
 | |
| Illustration 1 | g00671124 |
P-Q Characteristic Curves (1) Start of the destroke of the pump in the fine control mode (2) Start of the destroke of the pump in the standard mode (3) Start of the destroke of the pump in the power mode (4) Fine control mode (5) Standard mode (6) Power mode | |
Power Mode
Engine Speed Dial At Position 10
The power mode is used for heavy work that requires a higher engine speed. Selecting the power mode with the engine speed dial in position 10 will allow regulation of output of the pump. This regulation is accomplished through engine speed and delivery pressure. This regulation provides the maximum available engine horsepower for a work operation.
The controller will regulate the pump so that the engine can maintain the target speed. This will give the maximum torque and the maximum horsepower that is available from the engine. As a load on the engine is increased, there is an incremental decrease from the no-load speed (2150 RPM). The rated speed is 2000 RPM. The rated speed provides the maximum available horsepower. If the load is increased further, the engine speed decreases below the rated speed to the target speed (1980 RPM). The controller will regulate the output of the pump so that the engine speed will be maintained at the target speed. While the engine is operating at the target speed, the horsepower of the engine is approximately equal to the horsepower for the rated speed. The engine runs at a speed that is close to the target speed for most of the pressure/flow points on the power mode.
The controller will monitor the engine speed through the speed sensor. The controller will send the appropriate signals to the proportional reducing valve in order to maintain the target engine speed. The proportional reducing valve will use the signal to adjust the power shift pressure to the regulator of the pump. Therefore, the power shift pressure will regulate the output of the pump in order to maintain the target engine speed.
In the power mode, the power shift pressure will be lower than the pressure in the other two modes. The flow that is delivered will begin to decrease after the pump delivery pressure has reached a higher pressure than the pressure in the other two modes. Therefore, the output of the pump is higher than the pressure of the other two modes. If the available engine horsepower for the main pump decreases due to the addition of an attachment pump or adverse conditions, the main pumps will be regulated in the following manner:
- The main pumps are designed to allow the addition of attachment pumps. If an attachment pump is added, the engine can maintain the target speed until a maximum of 50 percent of available engine horsepower is used for the attachment pump. When the main pumps use the other 50 percent of the available engine horsepower or more, the target speed is maintained through main pump regulation by power shift pressure.
- The engine horsepower can be decreased by the following conditions: engine wear, low grade of fuel, high altitude operation and other conditions. If the engine horsepower is decreased by any of these conditions, the main pumps are regulated electronically. This allows the engine to run at the target speed until the engine horsepower has decreased by 30 percent.
- As the engine horsepower is decreased, the engine can reach the target speed at a lower output of the pump than the speed at the maximum engine horsepower. This allows the engine to operate without stalling even if there is a maximum of 30 percent reduction in engine horsepower.
Engine Speed Dial At Position 9 Or Less
The power shift pressure will remain relatively constant at a selected position of the engine speed dial until the no-load engine speed decreases 250 rpm or more. If the engine speed is decreased below this level, the power shift pressure is increased in order to reduce the pump output. Therefore, the available engine horsepower to the pump is less than the horsepower at the 10 position for the engine speed dial. The pump is regulated by constant power shift pressure. This provides pump output according to a certain P-Q characteristic curve.
This power mode and the settings of the engine speed dial are used to perform operations under heavy loads or trenching. These operations require a slightly reduced operating speed for the machine. If the engine speed dial is in the 9 position and the power mode is "OFF", a slightly higher power shift pressure is produced. This pressure is slightly higher than the pressure that would be produced if the engine speed dial was in the 10 position. This reduces pump output by about ten percent.
Standard Mode
The standard mode is used to perform ordinary work. Selecting this mode will slightly decrease the working speed of the machine and the noise level and fuel consumption of the machine will be reduced. Under the following conditions, the performance of the machine will resemble a setting of the 9 position of the engine speed dial:
- The machine is in the standard mode.
- The engine speed dial is set at 10.
- The machine is not under a load.
Other positions of the engine speed dial are not affected. When the travel control is used or the control is used with other controls simultaneously, the power that is available for the travel circuits is equivalent to the power of the power mode.
The power shift pressure will remain relatively constant at a position on the engine speed dial of 1 to 9 until the no-load engine speed is decreased by 250 RPM.
If the RPM is decreased below this level, the power shift pressure is increased in order to reduce the pump output. The power shift pressure in the standard mode is higher than the pressure in the power mode. This will cause the pump to destroke at an earlier time than the amount of time that is required in the power mode.
Fine Control Mode
The engine speed dial of 1 is used for light work. This work does not require high speed and high power. Selecting this power mode will slow the working speed. The reduction of the working speed will improve the fine control operation. The reduction in the speed will also reduce the amount of noise and fuel consumption.
When the fine control mode is active, the maximum engine speed is limited to the speed of position 7 of the engine speed dial. Even if the engine speed dial is placed in the 8 through 10 position, the maximum engine speed is limited to the speed of the 7. Other positions of the engine speed dial are not affected. The available power for the travel circuits is equivalent to the available power of the standard mode when the travel control is used or the control is used with other controls simultaneously.
The power shift pressure will remain relatively constant at the setting of 5 to 10 of the engine speed dial, until the no-load engine speed has decreased by 250 rpm or more. The power shift pressure will vary at the setting of 4 to 1 of the engine speed dial. However, the powershift pressure will not vary with a change in load. If the RPM is decreased below this level, the power shift pressure is increased in order to reduce the pump output. The power shift pressure in fine control mode is higher than the pressure in the standard mode. This pressure will cause the pump to destroke at an earlier time than the time that is required in the standard mode. However, the power shift pressure will keep a higher constant level than the level of the standard mode. The pressure is not affected by the power mode switch.