Description

Hitachi Construction Machinery US6183210 2001 Technical Manual

Let me cut through the noise. You are working on a Hitachi excavator or a piece of hydraulic construction equipment that isn’t holding torque under load. The engine lugs down, the pump starts hunting, and you’re chasing a ghost because the aftermarket “manual” you bought online gives you a generic curve that doesn’t match the machine’s behavior. I have torqued more head bolts than most people have had hot meals, and I can tell you: when the pump torque control circuit goes sideways, you need the actual factory logic, not a rewrite. This Hitachi Construction Machinery US6183210 2001 Technical Manual is the original United States patent filed by Kazunori Nakamura that covers the torque control device for hydraulic pumps used in Hitachi construction equipment. It is 21 pages of dense engineering, not a fluff-filled brochure.

Look at page 2 and you will find 11 drawing sheets that show exactly how the speed sensing circuit, the torque modification value (ΔTTH), and the servo valves interact. The patent text on page 1 walks you through the modification gain calculation, the subtraction of the torque modification from the speed sensing deviation, and how that signal gets output to the synchronizing control circuit. If you have ever swapped a pump controller and still had the machine stall under load, this is the documentation that explains why. The OEM factory specs are right here: the target torque, the detected output, the pump torque reference. No guesswork.

Patent Number US6183210 – Why Factory Documentation Matters

I am a stickler for source authenticity. Aftermarket documentation often copies the abstract, forgets the math, and leaves out the field of search references (U.S. Cl. 417/222.1, 60/434) that tell you what other patents were considered. This manual is a direct scan of the original patent filed by Hitachi Construction Machinery Co., Ltd. in 1998 and published February 6, 2001. Every foreign patent reference — EP 062077, JP 55-4102002, JP 57-65822 — is listed on page 1. When you are troubleshooting a total horsepower control circuit, that list of prior art can point you to related designs. You don’t get that from a third-party reprint.

If you need a broader overview of Hitachi’s construction machine lineup, check out the Hitachi Construction Machinery ZX160W Technical Manual – OEM Factory Specs for wheeled excavators, or the Hitachi 160LC/180LC/180LCN Technical Manual – 354 Pages for track hoe models. For compact wheeled machines, the Hitachi ZX130W Technical Manual – OEM Factory Specs covers similar pump control architecture.

Torque Control Device for Hydraulic Pump – What the Manual Covers

The core of this document is the torque control system that prevents the prime mover from stalling when the load increases. The abstract on page 1 describes how “modification gain calculates portions 70e and 70a of the target torque” and then subtracts the torque modification value from the speed sensing deviation. That is not just theory — that is the exact algorithm used in the pump controller. The manual gives you the formula, the block diagram (Figure 1 through Figure 4 on sheets 1-4), and the entire patent claims. You can trace the signal path from the torque modification portion to the servo valve SV, which controls servo valves 22 for total horsepower control.

Working with hydraulic pump torque adjustments means understanding the relationship between engine output, pump suction torque, and the synchronizing circuit. The manual explains how the suction torque TR1 (target maximum torque) is determined by adding the torque modification ΔTTH to the pump torque 30b. That is a far cry from the generic “set the pump to 350 bar” advice you find online.

11 Sheets of Diagrams – Decoding the Hydraulic Logic

Pages 2 through 5 contain the first four sheets of the 11-drawing set. Sheet 1 shows the overall system layout; sheet 2 details the torque control circuit; sheet 3 gets into the modification gain blocks; sheet 4 illustrates the synchronizing control circuit. Each sheet is referenced in the patent claims. If you are rebuilding a pump controller board or troubleshooting a wiring harness, these diagrams are your road map. Without them, you are probing blindly. The OCR excerpt on page 4 shows the messy but accurate reproduced text — that tells you this is a straight scan, not a retyped version that introduces errors.

Who Needs This Technical Manual?

This manual is for the mechanic who has a Hitachi excavator in the bay and the engine is dropping 300 RPM under load. It is for the shop owner whose technician wasted three hours chasing a symptom that turned out to be a miscalculated torque modification gain in the controller. It is for the DIY landowner who owns a US6183210-series machine and wants to understand why the hydraulic pump behaves differently at high altitude or in cold weather. The patent references conditions where “engine output lowers due to change of the environment” — that temperature and altitude compensation is baked into the algorithm. If you are working on total horsepower control systems, this document gives you the factory math.

For comparison, a standard Manual Transmission repair guide won’t help you with pump torque deviation. Even a Manual Transmission overhaul manual is a different animal. This patent is specific to hydraulic construction equipment pump control.

FAQ

Is this a shop repair manual with step-by-step removal instructions?

No. This is the original utility patent document filed for the torque control device. It contains the technical theory, calculation formulas, and system diagrams, but not a removal-and-install procedure.

Does the manual include torque specifications for bolts?

No bolt torque specs. The manual focuses on hydraulic pump torque control values — target torque, modification gain, and speed sensing deviation.

Can I use this to program a pump controller?

Yes, if you understand the math. The patent describes the algorithm that the controller uses to modify the pump torque based on engine speed deviation. It gives you the framework for calibration, not the specific software code.

What page has the pump torque calculation formula?

The formula is described in the abstract on page 1 and detailed across the specification. Look for the section starting with “A speed sensing torque deviation is fixed portion 70d, subtracts the torque modification value ΔTTH from speed sensing torque deviation.” That paragraph contains the full calculation.

You have the machine in the bay, the engine is struggling, and you need the real engineering behind the pump control. Do not settle for a third-party summary. Access the Factory Manual and get the original Hitachi Construction Machinery documentation that explains exactly how the torque control device works. Every torque value, every diagram, every claim is here in these 21 pages.