Commercial Products Hydraulics Hydrostatics Schematics and Test Equipment Part No. 82356SL, Rev.
Introduction Turf mowing equipment was very cumbersome and inefficient when it was first developed back in the early 1900’s. Improvements were made through the years of Turf equipment’s development, but it wasn’t until hydraulics became a part of the design that significant improvements were made. Use of hydraulics has increased to form a major portion of turf product designs.
INDEX 1: HYDRAULIC PRINCIPLES, PAGE 2. OBJECTIVE: To familiarize the technician with the basic fundamentals of hydraulic systems and their operation. 2: HYDRAULIC SCHEMATICS, PAGE 7. OBJECTIVE: Improve hydraulic technicians ability to read and comprehend hydraulic schematics, and apply them to various repair jobs. 3: HYDROSTATIC TRANSMISSIONS, PAGE 14. OBJECTIVE: Provide technicians with helpful information on the operation and maintenance of hydrostatic transmissions.
Principles of Hydraulic Circuits and Components 3. By making the containers or cylinders of different sizes, the mechanical advantage in work force increases (Fig. 4) Figure 1 A hydraulic circuit, whether it is simple or complex, uses the following basic hydraulic principles: Figure 4 1. A liquid can assume any shape and be bidirectional with out affecting its free flow movement (Fig 2) Basic Hydraulic Circuits and Components Used in Turf Equipment.
When the piston in the pump is pushed downward, oil will be directed past a second check ball into the cylinder. As the pump is actuated up and down, the incoming oil will cause the cylinder ram to extend. The lift cylinder will hold its extended position because the check ball is being seated by the pressure against it from the load side of the cylinder. The cylinder will return to neutral by unseating or bypassing the check balls, allowing the oil in the cylinder to return back to the reservoir (Fig.
Below is a cutaway of an actual hydraulic control valve (Fig 10). Figure 12 Figure 10 Since the fluid from a positive displacement pump must flow continuously whenever the pump is running it must have some where to go if not being used by the actuators. If the load on the cylinder becomes too great or if the ram bottoms out, the flow from the pump will be directed past the relief valve returning to the reservoir (Fig 13).
Figure 15 shows a hydraulic reel motor. solenoid valves and the internal porting to make the valve operate (Fig 18). The outer ports on the valve body are threaded to allow hoses and lines to be connected to the valve body. Care should be taken when tightening the hose and line fittings so the valve is not distorted by over tightening of the connections. Tighten the line and hose connections to the correct Flats From Finger Tight (F.F.F.T.) spec. listed in the service manual.
Figure 20 Figure 22 Inside the cartridge valve there is the valve spool, the armature and the armature spring. The manufacturing tolerances are extremely close and great care should be used when cleaning this type of valve. Cartridge valves used in most Toro equipment should not be disassembled. Figure 20 is for illustrative purposes only.
Introduction To Hydraulic Schematics Accurate diagrams of hydraulic circuits are essential to the technician who must repair it. The diagram shows how the components will interact. It shows the technician how it works, what each component should be doing and where the oil should be going, so that he can diagnose and repair the system. CIRCUIT DIAGRAMS There are two types of circuit diagrams. A: Cutaway Circuit Diagrams show the internal construction of the components as well as the oil flow paths.
3. Lines 5. Hydraulic motors Figure 7 LINES Hydraulic motor symbols (Fig 7) are circles with triangles, but opposite of a hydraulic pump, the triangle points inward to show the oil flows in to the motor. One triangle is used for a non-reversible motor and two triangles are used for a reversible motor. An arrow through a motor shows that it is a variable speed motor. Figure 4 A hydraulic line, tube, hose or any conductor that carries the liquid between components is shown as a line.
10. Hydraulic Cylinders 8. Hydraulic valves Figure 10 A control valve (Fig 10) has envelopes (squares) that represent the valve spool positions. There is a separate envelope for each valve position and within these envelopes there are arrows showing the flow paths then the valve is shifted to that position. All the port connections are drawn to the envelope that shows the neutral position of the valve. We can mentally visualize the function of the valve in any position.
13. Valve Enclosures 14. Complete hydraulic schematic Figure 15 When you see an enclosure outline, (Fig 15) that indicates that there are several symbols that make up a component assembly such as a valve body or valve stack. The enclosure outline appears like a box and is broken with dashes on all sides. Figure 16 Here we have a simple hydraulic schematic (Fig 16) using the symbols that we discussed and how they are used in a complete schematic.
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Hydrostatic Transmissions Hydrostatic transmissions have become quite popular in Turf equipment applications. Their increased use has been due to their simplicity, low maintenance requirements, compact design, operator convenience, and resistance to operator abuse. Hydrostatic transmissions can be easily repaired and maintained if you have a basic understanding of the components and their function.
pumped. As the operator moves the traction control pedal the angle of the swash plate increases, this in turn increases the piston travel. As the piston travel increases the amount of oil pumped increases and the travel speed changes. The pump consists of the following components. The piston group assembly. (Fig 4) This rotating piston group is mounted to the input shaft and is driven by the engine. It consists of a piston block with numerous precision machined bores which house the pump pistons.
Directional charge checks. (Fig 8) OVERALL OPERATION Directional charge check valves are incorporated into the charge circuit to direct the charge pump output to the low pressure side of the drive circuit. The oil will flow into the low pressure side to replace the oil lost through normal leakage. The oil in the high pressure side closes the remaining charge check valve so that no high pressure oil can bleed off into the charge circuit.
IMPLEMENT CIRCUIT (Fig 13) NOTE: It is important to realize that the main circuit must have enough oil flow and pressure supplied to it to replenish the oil lost in the drive circuit. Should the main circuit develop excessive leakage, the charge relief valve will not be opened and no oil will flow to the implement circuit. Some machines require hydraulic oil to operate the implement lift functions. This can be accomplished by using a larger charge pump.
The hydrostatic transmission will provide trouble free operation if it is serviced and maintained properly. There are, however, a few simple items that are often overlooked when poor performance is evident. even though the traction control pedal or hand lever is fully pushed. 1. The “ no-load” engine RPM. setting is too slow. 4. The hydraulic oil filter or inlet line is not tightened sufficiently; air is being drawn in past the filter seal into the charge pump, and then into the main circuit.
Hydraulic Hoses and Fittings Inspect hoses frequently for signs of deterioration or damage. Check hoses for leakage and replace when leaks are found. Hydraulic Hoses Hydraulic hoses are subject to extreme conditions such as, pressure differentials during operation and exposure to weather, sun, chemicals, high temperature operating conditions or mishandling during operation or storage. Hoses that move during operation are more susceptible to these conditions than others.
O-ring Face Seal (ORFS)Fittings 1. Make sure both threads and sealing surfaces are free of burrs, nicks, scratches, or any foreign material. Nut Sleeve 2. Make sure the O-ring is installed and properly seated in the groove. It is recommended that the O-ring be replaced any time the connection is opened. Body Seal 3. Lubricate the O-ring with a light coating of oil. 4. Put the tube and fitting squarely into position on the face seal end of the fitting and tighten the nut until finger tight.
SAE Straight thread O-ring Port Fittings (Non-Adjustable) 1. Make sure both threads and sealing surfaces are free of burrs, nicks, scratches, or any foreign material. Size F.F.F.T. 4 (1/4 in. nominal hose or tubing) 6 (3/8 in.) 8 (1/2 in.) 10 (5/8 in.) 12 (3/4 in.) 16 (1 in.) 1.00 ± .25 1.50 ± .25 1.50 ± .25 1.50 ± .25 1.50 ± .25 1.50 ± .25 2. Always replace the O-ring seal when this type of fitting shows signs of leakage. 3. Lubricate the O-ring with a light coating of oil. 4.
O-ring Kit After Repair or Replacement of Components O-ring face seal connections on Toro equipment require the use of special 90 Durometer O-rings. Toro recommends that the O-rings need to be replaced whenever a connection is loosened. An Oring kit is available containing quantities of O-rings for both face seal and port seal connections used in Toro equipment. 1. Check oil level in hydraulic reservoir and add correct oil if necessary.
Principles of Hydraulic Test Equipment A hydraulic system with an excessive increase in heat or noise is a potential failure. Should either of these conditions be noticed, immediately stop the machine, turn off the engine, locate the cause of the trouble, and correct it before allowing the machine to be used again. Continued use of an improperly functioning hydraulic system could lead to extensive internal damage. 6.
Hydraulic test equipment allows you to observe the amount of oil pressure and oil flow in a circuit under various conditions. Hydraulic Tester (With Pressure and Flow Capabilities) 1. INLET HOSE: Hose connected from the system circuit to the inlet side of the tester. Hydraulic testers may vary significantly in size, construction, accuracy, and cost.
turning it counter clockwise (tester with pressure and flow capabilities). Before Performing Hydraulic Tests ALL OBVIOUS AREAS SUCH AS OIL SUPPLY, FILTERS, IMPROPER ADJUSTMENT BINDING LINKAGE, OR LOOSE FASTENERS MUST BE CHECKED BEFORE ASSUMING THAT A HYDRAULIC COMPONENT IS THE SOURCE OF THE PROBLEM BEING EXPERIENCED. IMPORTANT: Pumps used on Toro equipment are of a positive displacement type.
HOOK UP NO. 2 TEST A: FLOW TO MOTOR With the control valve in the run position and the flow meter in series between the control valve and the motor, (Fig 8) we can measure the flow to the motor and compare this reading with the reading we had previously observed in Hookup No. 1, Test A. If this reading is now lower, it indicates a problem in the spool valve or oil leakage past the relief valve.
REVIEW QUESTIONS Answer the following review questions. 7: The following symbol is: 1: A larger displacement pump operating at the same speed will: A: Move more oil B: Move less oil. C: Displacement has no effect on oil flow. A: Oil Cooler. B: Reversible Hydraulic Motor. C: Combination pump\motor. D: Reversible Hydraulic Pump. 2: When a open center spool valve is in the neutral position: A. B. C: D: All oil flow stops. Oil flows back to reservoir. Oil flows to lower port. Oil flows to raise port.
REVIEW QUESTIONS 16: A properly installed hose will have a 45º twist in the hose. 11: A Hydrostatic Drive pump is: A: Fixed displacement. B: Variable displacement. C: Driven by the wheels. A: True B: False 17: Fitting O-rings should always be installed dry. 12: The purpose of the charge pressure circuit is: A: True B: False A: Pressurize the hydraulic filter. B: Replenish internal oil leakage in drive circuit. C: Pressurize transaxle case to keep dirt out.
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