I doubt there are any rules against it -- you'd have to look at Google's terms of service to get a definitive answer for that -- but I also doubt this would actually work. According to this article, the number shown on the store is a count of the number of unique users who have ever installed the app.
So you could download the app all you want, and you'd see total installs on the developer console go up, but it wouldn't change the number shown in the store. Even if it did, it would take an exorbitant amount of time to reach a number that would be capable of influencing people.