Investors have flocked into dividend funds and individual dividend-paying stocks as they try to generate steady income during a time of rock-bottom interest rates.

“Vanguard is proactively taking steps to slow strong cash flows to help ensure that the advisor’s ability to produce competitive long-term results for investors is not compromised,” Vanguard CEO Bill McNabb said in a statement. “We have long been committed to protecting the interests of our funds’ shareholders, and demonstrate this conviction by closing or restricting funds to stem further growth.”

Over the past six months, the fund has received an additional $3 billion in net cash inflows and, over the past three years, the fund’s assets have nearly doubled, Vanguard said.

A flood of cash into a fund can create problems for portfolio managers, as they may be tempted to take more risk to put the cash to work. And if they just sit on the cash, their returns may suffer when compared to a full invested benchmark index.

Vanguard’s fund has produced a total return of 9.13 percent for the 12-month period that ended June 30. That’s better than the 8.48 percent advance on the Nasdaq US Dividend Achievers Select Index.

Introduced in 1992, the fund is managed by Wellington Management’s Donald Kilbride.