The evolution of DENSO’s Starter & Alternator technology

DENSO-starter-smStarters and Alternators have a vital role to play – from starting the motor to keeping the vehicle running – no vehicle is complete without them. True pioneers of leading Starter and Alternator technology for modern cars, motorcycles and commercial vehicles, DENSO has become the world’s largest OE rotating machine manufacturers, with 33.4 percent global market share.

Nick Thomas, Product Manager at DENSO Aftermarket Sales UK & Ireland explains how the company’s Starters and Alternators have evolved to bring cutting-edge, world class rotating machine technology to the aftermarket.

Since the evolution of more ‘intelligent’ vehicles featuring equipment such as navigation systems and complex electronic control panels, the demands placed on the starter and alternator have increased dramatically. The continual need for higher power outputs – without compromising weight limitations and improved environmental standards – has led DENSO to develop rotating machines that are smaller, lighter, quieter and more powerful.

More recently the growth of stop-start technology in Europe has been more rapid than anywhere else in the world. Driven by strict European regulations (95g/km by 2020), European car manufacturers are looking to develop vehicles which improve fuel efficiency and reduce CO2 emissions. Stop-Start systems, which automatically stop the engine while the vehicle is waiting at traffic lights or is stopped for other reasons, and restart it smoothly when the vehicle needs to move again, hold part of the solution. The technology, which centres on the vehicle’s starter, has proved to be reliable and cheap to manufacture, saving drivers gallons of fuel every year and reducing the level of harmful emissions produced by cars every year.

Advanced Starters from DENSO – then and now
DENSO launched its first OE Starter programme in the early 1960s. From there the products’ design and efficiency have developed in line with the demands of modern vehicles, including the introduction of External-Gear Deceleration R and RA-Starters in the early 1970s and late 1980s respectively. However, it was in the early part of the 21st century that saw the ‘big leap’ in starter technology, with DENSO’s introduction of the world’s first PS Starter (Planetary Reduction Segment Conductor Motor). Featuring a square conductor in the armature coil, the PS starter was 22 percent lighter and 14 percent shorter than its predecessor, resulting in improved fuel efficiency and mountability.
Most recently DENSO’s newest additions to this market include the Advanced Engagement (AE) Starter – DENSO’s first stop-start starter – and the Tandem Solenoid incorporating the latest DENSO technology.
Designed specifically for stop-start systems using the world’s first mechanism to separately control the forward shift of the pinion gear and the motor rotation, DENSO’s innovative Tandem Solenoid (TS) Starter ensures a quick restart even when the engine is rotating. Depending on vehicle specifications, the technology can help improve fuel efficiency by approximately 3 to 5 percent.
The Advanced Engagement (AE) Starter works like a typical planetary starter but has 10 times the durability. When it’s energized, the pinion shifts forward, engages with the flywheel, and immediately spins. In terms of starter motor-based solutions for stop-start systems, AE starter is the easiest to integrate to the engine, requiring no unique controls or engine modifications. It helps car manufacturers achieve approximately 3-5 percent fuel savings, depending on engine size.

DENSO Starters development history

  • Unique structure with the pinion gear pushed through the drive lever
  • Spiral brush spring
  • Aluminium end frame


  • External-Gear Deceleration R-Starter
  • World’s first deceleration structure – decreased the mass by half, while maintaining the same output
  • Pinion direct-shift method improves environmental durability


  • External-Gear Deceleration RA-Starter
  • High-speed motor with an improved deceleration ratio and heat-resistant electric wire reduces the size and weight of the motor
  • Cold-forged spline reduces the size and weight of the magnetic switch


  • Internal-Gear Deceleration PS-Starter
  • A rectangular conductor and surface commutator in the armature and a magnet between the main electrodes of the yoke, reduced the size and weight of the starter
  • Combining the damper unit and the high deceleration ratio reduced the size and lowered driving noise

Stop/Start Starters

  • Long life starter technology, quick and quiet restart times
  • Advanced Engagement (AE) Starter
  • – The AE includes key design features like dual layer, long-life electrical brushes, as well as a unique pinion spring mechanism that reduces ring gear/ flywheel wear by approximately 90 percent
  • Permanently Engaged (PE) Starter
    – Jointly developed with a leading car manufacturer
    – The PE Starter delivers the quickest and quietest restart times of all starter motor-based systems, with increased overall fuel-saving potential. Starter and flywheel gears are permanently connected, meaning there are no difficulties with the dynamics of gear engagement and disengagement.
  • Tandem Solenoid (TS) Starter
    – The TS starter is unique, because it restarts the car’s engine before zero rpm. It is the first starter in the world to use a structure that separately controls starting the motor and shifting the pinion gear and it can fit in the same space as a traditional starter.

Advanced Alternators from DENSO – then and now
Leading the way with its advanced technology, DENSO’s Alternators have been part of vehicle OE manufacturing since the early 1960s. Over the last 50 years, vehicle demands and add-on technologies have developed greatly, putting more strain on the vehicle’s electronic system than ever before. Because of this, alternators have needed to develop in parallel; meeting the demand for additional electrical output by producing more power via smaller size and lighter weight.

For the last few decades, DENSO has been at the cutting edge of alternator design, with the world’s first SC (Segment Conductor) Alternator. DENSO was the first manufacturer in the world to use a rectangular conductor for its stator cell. Added to this the raising of the winding density (space factor) from 45 to 70 percent, enabled DENSO to develop an alternator that is 20 percent lighter, as well as benefiting from increased output of over 50 percent higher than conventional types.

In 2012 DENSO launched the first replacement DENSO Alternator for BMW, suitable for BMW 1 and 3 series. The same year DENSO Corporation celebrated the production of its 100 millionth SC Alternator.

DENSO Alternators development history
Alternator with Separate Regulator

  • First alternator using a silicon rectifier
  • Separate contact regulator

Alternator with Integrated Regulator

  • Produced higher output using a cold forged rotor core to improve magnetic circuit
  • Reduced size and weight by using an internal regulator IC

Alternator with Internal Fan

  • Increased output by optimising stator and rotor sizes to improve the magnetic circuit and decreasing the pulley diameter for a faster rotor
  • Fan having two fan blades, integrated with the rotor – reduced fan noise, size and weight

SC Alternator

  • Using the world’s first rectangular conductor in stator coil increased winding density, reduced weight and increased output
  • One chip IC regulator

The DENSO difference
DENSO Starters and Alternators have been getting our vehicles going and keeping them moving since 1961. As the world’s leading automotive components supplier, DENSO is a global leader in developing and manufacturing original equipment rotating machines. DENSO’s aftermarket Starter and Alternators programmes are subject to continual expansion, helping the company to offer a number of unique OE references. The programme currently comprises 294 part references for 2,721 key applications including OE coverage of Toyota, plus a wide range of European marques such as Ford, Audi, Opel, BMW, Fiat, Volvo and Land Rover.

Every machine is completely new in box rather than re-manufactured. With no core surcharge administration is greatly reduced; ensuring a high quality product made from genuine parts at a competitive price.

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Published on: March 10, 2015

Filled Under: News, Technical Articles

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