Rexroth DA GB RZ 25.6.03 25.06.2003 14:37 Uhr Seite 22

Rexroth_DA_GB_RZ 25.6.03 25.06.2003 14:37 Uhr Seite 22

Industrial Electric Drives Linear Motion and Service Mobile Hydraulics and Controls Assembly Technologies Pneumatics Automation Hydraulics

Easy Machine Operation with

Bosch Rexroth AG Rexroth Automotive Drive and Mobile Hydraulics Glockeraustraße 4 Anti Stall Control 89275 Elchingen, Germany Tel . +49 (0) 73 08-82 0 Fax +49 (0) 73 08-72 74 [email protected] www.boschrexroth.com/brm The Drive & Control Company

Printed in Germany RE 98300/06.03 Rexroth_DA_GB_RZ 25.6.03 25.06.2003 14:37 Uhr Seite 2

2 Rexroth Automative Drive and Anti Stall Control | Features and Functions 3

Pressure sensing capabilities of the DA-system allow precise and efficient drive behavior since in the lower and intermediate engine speed range, the tractive effort is varied by the diesel engine speed. Telescopic handlers, for The Features The Functions instance, thus allow sensitive positioning.

The Automotive Drive and Anti Stall Control (DA) is a pure hydro-mechanical control for closed loop transmissions which provides two main features: Automotive Drive Control and/or Anti Stall Control. Additional options provide servo override controls and enhanced braking.

Automotive Drive Control Both features can be realized allows the operator to run a machine without any direct link between with a hydrostatic transmission pump and accelerator pedal. There similar to a passenger car with is no requirement for any control automatic transmission: The more rod or electronics. The pump the accelerator pedal is moved controller works fully automatically. down, the more the transmission pump increases its delivered flow, The DA control is a well proven i.e. speeds up the vehicle. control system, produced for many years. Thousands of different Automotive Drive Control makes the When wheels get blocked, the tractive pump displacement follow the engine effort is controlled via the diesel engine Anti Stall Control machines, e.g. fork lift trucks, speed, however, without heating up the ensures that the pump adjusts its municipal vehicles, wheel loaders speed: system. consumed power to the power or other vehicles are proof of the •Pushing down the accelerator pedal available from the diesel engine. reliability, durability, and leads to an increase in engine speed. In any overload situation, the Anti uniqueness of this concept. •The difference in engine speed also Stall Control reduces the pump’s causes a different pump speed. Since the flow rate to a value that prevents boost pump is integrated in the Arto stipata theatro spectat Roma po- the engine from stalling. transmission pump it also shows a tens habet hos numeratque. different flow rate. Interdum volgus rectum videt, est ubi peccat. Si veteres ita miratur laudatque poe- •The boost pump’s flow rate is measured tas, ut nihil anteferat, nihil illis comparet, within the transmission pump’s speed errat. Si quaedam nimis antique, si pera- sensing valve. que dure dicere volgus rectum videt, est ubi peccat. Si veteres ita miratur laudatque • The more flow travels through the speed An A4VG pump with Drive and Anti Stall Control DA as well as an integrated inching poetas, ut nihil anteferat, nihil illis compa- valve ensures a smooth drive characteristic. This allows careful handling of goods with sensing valve, the more the pump goes ret, errat. Si quaedam nimis antique, si pe- maximum drive comfort as well as quick acceleration and thus high turnover speeds of on stroke and thus delivers more flow. raque dure dicere arto stipata theatro the handled material. spectat Roma potens; habet hos numerat- This in turn increases the vehicle speed. que poetas ad nostrum tempus Livi scrip- The travel direction is selected by an toris ab aevo. Interdum volgus rectum vi- integrated forward-neutral-reverse valve. det, est ubi peccat. Si veteres ita miratur laudatque poetas. The selected hydraulic motor can be either of constant displacement (e.g. A2FM) or variable displacement (e.g. A6VM). Rexroth_DA_GB_RZ 25.6.03 25.06.2003 14:37 Uhr Seite 5

4 Rexroth Automative Drive and Anti Stall Control | Applications 5

The Functions The Applications

Well balanced rotary The working characteristic of a DA-controlled vehicle can be displayed within a three dimensional diagram shown on group technology this page. The x-axis describes the travel speed which corresponds to the flow rate of the transmission pump. features power self control to serve as The y-axis shows the tractive effort which is proportional to the drive pressure. Eventually, the z-axis displays the engine stalling engine speed which is mainly determined by the accelerator pedal position. protection All working points of a vehicle with Automative Drive and Anti Stall Control are located on a three dimensional surface within this diagram. Looking at three typical day to day travel situations, the working principle becomes clear:

Characteristic of the Rexroth Automative Drive and Vehicle Entering a Slope Anti Stall Control A vehicle traveling at full speed on plain ground enters an uphill slope. This obviously requires an increased tractive effort. The working points in the three dimensional diagram are:

1 Vehicle traveling at max. speed on plain ground: The pump is at full stroke and delivers maximum flow. The established pressure level corresponds to the vehicle’s drive resistance (rolling-, air resistance) in this operation condition. 2 Entering the slope causes the tractive effort to increase. This yields increasing hydraulic system pressure. The diesel engine lugs due to increased power requirement. The pressure sensing rotary Anti Stall Control protects the In case of additional power group swivels back and balances hydraulic and engine power engine from stalling: requirements from other consumers according to the increased system pressure. The pressure sensing capability of (e.g. steering systems, implement the transmission pump’s rotary hydraulics), the transmission pump group is the main feature of the Anti automatically adjusts its displacement Stall Control. Increasing pressure to balance the power of engine Vehicle Getting into Stall Mode may be caused by the vehicle getting (output) and hydraulics (input). Accelerating Vehicle A vehicle, e.g. a wheel loader, accelerating on plain ground shows a Another typical situation is a vehicle driving at medium speed and getting into heavy ground conditions, or by Depending on the application, the certain characteristic travel path within this diagram. The working stalled out. This may be for instance a loader entering a pile of gravel with driving up a hill. Anti Stall Control may allow the points at the different states are: its shovel. • Increasing pressure in the installation of smaller diesel engines 1 At standstill, the engine runs at low idle. The DA pump stays at 1 Driving at medium speed across a plain ground yields a certain transmission pump’s working lines since they are now protected against zero flow at this stage. pressure level that delivers the necessary tractive effort to overcome all drag. lead to a reduction in pump stalling. 2 Slightly pushing the accelerator pedal causes the engine to displacement. speed up. The DA pump senses the increased engine speed 2 Touching the first gravel increases the required tractive effort. The system pressure goes up. At the same time the pressure sensitive • With the reduced displacement the and starts to build up pressure. However, due to the vehicle’s friction, it does not yet move. DA-pump already reduces the flow to not overload the engine. pump delivers less flow and adapts 3 The vehicle overcomes the sticking forces and starts to move. 3 Fully digging into the pile of gravel further increases the system its power intake to the engine pressure. The engine sees increased loading. This loading leads to 4 Steadily pushing the accelerator pedal speeds up the engine. an engine speed decrease. power capabilities. It thus protects The DA pump continuously increases its stroke and thus the engine from stalling. delivers increased flow. The vehicle speeds up. 4 If the system pressure exceeds preset values (given by hydraulic component’s pressure rating), the DA-pump’s pressure cut-off 5 Approaching maximum speed, the pressure slightly decreases function reduces the pump’s flow rate. The pump adjusts its again since there is no further acceleration necessary. The displacement to maintain full system pressure (i.e. maximum tractive vehicle only needs to overcome the frictional drag forces. effort) without heating up the system. Rexroth_DA_GB_RZ 25.6.03 25.06.2003 14:38 Uhr Seite 8

6 Rexroth Automative Drive and Anti Stall Control | Options and Service 7

The Options The Service

Rexroth application engineers are ready to assist you in Servo Override Controls the right selection of components and controls that The Automotive Drive and/or Stall Control can be combined with all servo displacement controls. This allows both enjoying best suit for your application. All pumps equipped the ease of operation of an automotive drive when operating on the road and the load independent precision of servo with the Automotive Drive and Anti-Stall Control are displacement control in the working mode. Frequently used servo displacement controls with Automotive Drive and/or Anti factory set and fully tested according to specification to Stall Control (DA) are mechanical proportional (HW), hydraulical proportional (HD) or electrical proportional (EP). See the meet your engine and application requirements. Rexroth A4VG and A10VG pump data sheets RA/RE 92 003 and RA/RE 92 750 for reference.

The DA-pumps offer various options of override controls for specific braking and inching functions:

Brake pressure inching valve Rotary inching valve for low speed operations Rexroth Power Brakes with integrated inching valve The brake pressure inching valve works simultaneously Rotary Inching Valve is the preferred solution when If the vehicle includes a hydraulic power brake system, inching with the service brake. This is therefore the best solution inching shall be separated from braking. This is typically can be realized cost effectively by using the Rexroth power when inching shall support the service brake to reduce the case when certain operations require high engine brake valve LT 31 with integrated inching function (see technical brake pad wear. speeds while the travel speed is very low. data sheet RE 66 227). The function is similar to the version Application example: To slow down a wheel loader, the Application example: Sweeping machines when the brush with brake pressure inching valve described on the far left. operator pushes down the brake pedal. Pushing gently system requires full hydraulic oil flow from the implement means hydrostatic braking only, pushing harder means pump while the travel speed is low. Rexroth Power hydrostatic and service braking simultaneously. The pump’s control device is hydraulically connected to the Brake Valve LT31 The pump’s control device is hydraulically connected with remotely installed rotary inching valve. The inching valve with integrated the service brake circuit. Increasing pressure in the service in turn is mechanically operated by either a hand lever or a inching function brake system causes the transmission pump to destroke. pedal. Pushing the lever or pedal and thus increasing the angle of the rotary inching valve’s lever causes the transmission pump to destroke.